You are viewing a javascript disabled version of the site. Please enable Javascript for this site to function properly.
Go to headerGo to navigationGo to searchGo to contentsGo to footer
In content section. Select this link to jump to navigation

Calmodulin Binding Proteins and Alzheimer’s Disease


The small, calcium-sensor protein, calmodulin, is ubiquitously expressed and central to cell function in all cell types. Here the literature linking calmodulin to Alzheimer’s disease is reviewed. Several experimentally-verified calmodulin-binding proteins are involved in the formation of amyloid-β plaques including amyloid-β protein precursor, β-secretase, presenilin-1, and ADAM10. Many others possess potential calmodulin-binding domains that remain to be verified. Three calmodulin binding proteins are associated with the formation of neurofibrillary tangles: two kinases (CaMKII, CDK5) and one protein phosphatase (PP2B or calcineurin). Many of the genes recently identified by genome wide association studies and other studies encode proteins that contain putative calmodulin-binding domains but only a couple (e.g., APOE, BIN1) have been experimentally confirmed as calmodulin binding proteins. At least two receptors involved in calcium metabolism and linked to Alzheimer’s disease (mAchR; NMDAR) have also been identified as calmodulin-binding proteins. In addition to this, many proteins that are involved in other cellular events intimately associated with Alzheimer’s disease including calcium channel function, cholesterol metabolism, neuroinflammation, endocytosis, cell cycle events, and apoptosis have been tentatively or experimentally verified as calmodulin binding proteins. The use of calmodulin as a potential biomarker and as a therapeutic target is discussed.


Alzheimer’s disease (AD) is the leading cause of dementia, with close to 50 million people worldwide currently suffering from dementia and the number expected to increase to 1 in 85 people by the year 2050 [1]. First described by the German psychiatrist Alois Alzheimer, it manifests through progressive memory loss ultimately encompassing a loss of recognition of people, places, and things, eventually leading to death [2]. Currently, the cure for AD remains elusive, with treatments focusing on managing symptoms and attempts to slow neurodegeneration. While the initiating events leading to late onset AD (LOAD) remain to be discovered, the formation of amyloid plaques and neurofibrillary tangles remain as central culprits in the neurodegenerative aspects of the disease. More recently, numerous genes and several metabolic events have been identified as either central or contributing factors in AD.

A decade ago, O’Day and Myre [3] proposed the “Calmodulin Hypothesis” as an extension of the well-established “calcium hypothesis” of LOAD. In that study, a number of proteins linked to the production of amyloid-β (Aβ) were shown to possess putative calmodulin binding domains (CaMBDs) suggesting that they could be regulated by the small regulatory, calcium-binding protein calmodulin (CaM). Subsequently, two of the central proteins in this event, amyloid-β precursor protein (AβPP) and beta-secretase (BACE1; beta-site AβPP cleaving enzyme 1) were each shown to bind to and be regulated by CaM [4, 5]. Non-amyloidogenic processing of AβPP in platelets was induced in a time- and dose-dependent manner by the calmodulin antagonist W7 [6]. Over the past 10 years, advancements have been made into understanding the pathways involved in both amyloid plaque and neurofibrillary tangle formation. Based on these new insights, here we first re-examine the role of calmodulin binding proteins (CaMBPs) in the formation of the two primary culprits linked to the symptoms and progression of AD: amyloid plaques and neurofibrillary tangles (Fig. 1). As summarized in Fig. 1, we then look at the function of calmodulin as a regulator of other events and recently identified proteins linked to the disease before looking at CaM as a potential therapeutictarget.


The “calcium hypothesis” is one prominent model for AD [7]. It suggests that an imbalance of calcium levels in cells precedes the signaling pathway malfunctions and neuronal deterioration observed in neurodegenerative diseases. It has long been known that calcium ions (Ca2 +) play a substantial role in normal physiology. In the brain, Ca2 + functions in neurotransmitter synthesis and release as well as in the control of membrane excitability [8]. The intracellular concentration of Ca2 + is kept within a tight range of 10 −7 to 10 −8 mol; variation from the norm, even if slight, is detrimental when it persists [8].

Calcium ions perform their function primarily through binding to membrane or cytoplasmic proteins. Arguably the primary calcium-binding protein and effector of calcium function is the small protein CaM. Highly conserved and ubiquitously expressed in all eukaryotes and in all cell types, it is a member of the EF-hand family of calcium sensors [9]. CaM possesses four E-F hands, two at the C-terminal and two at the N-terminal, allowing it to bind up to four Ca2 + ions [9, 10]. Each lobe (N, C) can bind up to two calcium ions (Fig. 2). The number and location of binding of this cation affects CaM’s conformation and how it interacts with its target CaMBPs. Proteins do not bind to Ca2 +/CaM via traditional targeting sequences. In the absence of Ca2 +, the apo-CaM conformation allows the binding of the sub-group of Ca2 +-independent CaMBPs (Table 1). Ca2 +-independent binding occurs via well-defined IQ [(FILV)Qxxx(RK)Gxxx(RK)xx(FILVWY)] andIQ-like [(FILV)Qxxx(RK)xxxxxxxx] motifs. Upon Ca2 + binding, CaM undergoes significant conformational changes allowing it to bind to Ca2 +-dependent CaMBPs. Ca2 +-dependent binding involves a diversity of motifs and sub-classes that are defined primarily by the sequence and positioning of hydrophobic amino acids sometimes in conjunction with basic residues within the motif (e.g., 1–5–10 motif: xxx(FILVW)xxxx(FAILVW)xxxx(FILVW) where x = any a.a.) [11]. The “Calmodulin Target Database” categorizes the various types of CaM-binding motifs (Table 1; In addition to the major CaMBD categories (e.g., 1–8–14, 1–5–10, etc.), there are also a large number of others that do not fit into any of these specific categories (e.g., 1–12 and basic motifs) among other more recently discovered binding non-canonical motifs [12].

To add to this non-conventional binding interaction, Villarroel et al. [13] have presented evidence indicating that while CaM binds its calcium-dependent targets via these CaMBDs in their normal orientation it can also bind to those sequences in the opposite direction. Furthermore, their data also suggests that upon binding to its target, CaM can undergo a conformational rotation further altering its structural relationship with that CaMBP. Considering the central importance of CaM to essential life processes, this complex protein interaction may be part of the reason CaM historically has eluded serving as a primary target in various diseases. Once the interactions between CaM and specific CaMBPs linked to AD are fully clarified, it may become possible to develop target-specific peptides to fight different aspects of the disease.


The Calmodulin Target Database identifies the presence and types of CaMBDs in protein sequences with over 90% accuracy [11]. Using this database, O’Day and Myre [3] first identified a diversity of potential CaMBPs linked to the formation of amyloid plaques. The “amyloid hypothesis” is arguably the predominant hypothesis for the symptoms and progression of AD [14]. It is based on the aggregation of Aβ peptides plus a multitude of other components to form extracellular amyloid plaques in the brains of AD sufferers [15–17]. Aβ peptides vary slightly in length and are formed through the regulated intramembrane proteolytic (RIP) cleavage of AβPP at the carboxy-terminal fragment (CTF) by β-secretase and γ-secretase enzymes (Fig. 3) [18]. The main products of this pathway are Aβ40 and Aβ42 with Aβ42 being the more toxic fragment [19]. Aβ peptides interfere with normal signaling leading to neuronal malfunction and, eventually, synapse loss [20]. On the other hand, there exists a non-amyloidogenic pathway of cleavage, where AβPP is cleaved in the middle of the Aβ sequence by α-secretase thereby preventing the formation of the neurodegenerative Aβ peptide [18].

CaM is significantly decreased in the brains of AD individuals [21]. In spite of this, the existing CaM can interact with several proteins in the amyloid pathway. Two independent groups have demonstrated experimentally that AβPP binds to CaM [4, 6]. The main β-secretase enzyme in the brain that begins the amyloidogenic processing of AβPP is BACE1 (Fig. 3). Its activity and expression are both increased in AD brains and its ablation completely prevents AβPP cleavage through the amyloidogenic pathway in mouse models [22, 23]. BACE1 cleaves AβPP at CTF-99 (and sometimes CTF-89), as opposed to cleavage at CTF-83 which is observed in the non-amyloidogenic pathway [18]. Most of the action of BACE1 on AβPP occurs in endocytotic vesicles as opposed to when AβPP is localized at the cell membrane [24]. BACE1 binds CaM with its activity being increased up to 2.5-fold by CaM in a dose dependent manner in vitro [5]. Sequence analysis of the enzyme indicates that binding most likely occurs via a 1-16 motif ((FILVW)xxxxxxxxxxxxxx(FILVW)).

After BACE1, γ-secretase performs the final cleavage to produce Aβ. γ-Secretase consists of four main subunits: nicastrin (Nic), anterior pharynx-defective 1 (APH-1), presenilin (PSEN), and presenilin enhancer 2 (PEN-2), which assemble in the order listed (Fig. 3) [25]. PEN-2, the final subunit to be attached, leads to the activation of the enzyme complex [25]. Sequence analysis of the four γ-secretase subunits using the Calmodulin Database revealed that they all possess presumptive CaMBDs, with some having more than one binding motif [3]. Of these subunits, only PSEN has been experimentally verified to bind CaM [26]. Michno et al. [26] also showed that the loss of function of a single CaM copy inhibits Ca2 + dysregulation induced by PSEN in Drosophila neurons.

Several enzymes can degrade Aβ including neprilysin, endothelin-converting enzymes (ECE), insulin degrading enzymes (IDE), and BACE1 (Fig. 3) [18, 27]. Aside from BACE1, none of the other Aβ degrading enzymes have yet been experimentally confirmed to bind CaM, although all of them were found to possess putative CaMBDs [28]. In addition to binding to the enzymes which generate Aβ, CaM was found to directly bind to Aβ42 itself through a 1-8-14 motif ((FILVW)xxxxxx(FAILVW)xxxxx(FILVW)) [29]. When bound to CaM, Aβ cannot inhibit the brain plasma membrane Ca2 +-ATPase (PMCA) and prevent Ca2 + entry into the cell. Thus the accumulated data presents a clear link between amyloid plaque formation, Ca2 +, and CaM revealing how the dysfunction in Ca2 + levels and Aβ production contribute to each other with CaM functioning at many levels during this interaction.

As mentioned above AβPP binds to CaM in vitro in a Ca2 +-independent manner [6]. The non-amyloidogenic pathway involves α-secretase cleavage of AβPP at CTF-83 precluding the formation of Aβ (Fig. 3). AβPP processed in this non-amyloidogenic pathway appears to have a neuroprotective effect. The ADAM (A Disintegrin And Metalloproteinase) family of proteases, specifically ADAM9, 10, 17, and 19 are all thought to exhibit α-secretase activity in neurons [18]. ADAM10, the predominant α-secretase, binds CaM through an IQ-motif [30–32]. In contrast, ADAM17 does not bind CaM [30]. Importantly, W7 an antagonist of CaM stimulates cleavage of AβPP via the non-amyloidogenic pathway [6, 33].


Neurofibrillary tangles constitute the second major hallmark of AD. Consisting primarily of hyperphosphorylated tau, they have long been known to be a neuropathological feature of the disease; although their role in neurodegeneration has come into question [34]. Tau belongs to the family of microtubule-associated proteins which function in microtubule assembly and stability [35]. Several early studies provided evidence for an in vitro association between tau and CaM that is Ca2 + dependent (Fig. 4) [36–38]. Tau’s association with CaM prevents its binding to microtubules [36]. Furthermore, tau cannot be phosphorylated by protein kinase C in vitro when it is in a complex with CaM [37]. In spite of this extensive early association, no recent studies have been conducted on the direct interaction between CaM and tau.

Tau can undergo many post-translational modifications including phosphorylation, acetylation, glycation, and oxidation [39]. Phosphorylation is the best studied and important tau modification related to AD, with several kinases and some phosphatases working in concert to regulate phosphorylation at several specific serine, threonine, and tyrosine residues [39]. Of the kinases, two have been found to interact with CaM: Ca2 +/CaM-dependent protein kinase II (CaMKII) and cyclin-dependent kinase 5 (CDK5). In addition, protein phosphatase 2B (PP2B or calcineurin) is a well-established CaMBP that has been historically linked to tau dephosphorylation [40].

CaMKII phosphorylates tau in vitro at different sites including Ser262 which is in the microtubule binding domain of tau (Fig. 3) [41–44]. The enzyme was also found to phosphorylate tau in neurons at Ser416 [45]. CaM is responsible for activating CaMKII by binding to its regulatory segment through a 1–5–10 binding motif [10, 46]. However, CaMKII is capable of acquiring autonomy from CaM in the presence of high frequency Ca-2 + spikes, despite it being able to phosphorylate tau more efficiently in the presence of CaM [43, 46].

It should also be noted that CaMKII has an established role in neuronal apoptosis which is observed throughout the course of the disease. Phosphorylation by CaMKII is a central pro-apoptotic event. Normally a murine double mutant 2 (MDM2) pathway mediates the degradation of CaMKII but this process is defective in AD lymphocytes [47]. The role of CaM in apoptosis has been reviewed by Berchtold and Villalobo [48].

CDK5 is another kinase with a well-established role in tau phosphorylation (Fig. 4). Various studies indicate that it phosphorylates a number of specific residues including Ser202, Thr205, Ser369, and others, both in vitro and in vivo. Additionally, reducing CDK5 activity using RNA interference was found to reduce tau phosphorylation and the number of neurofibrillary tangles formed in transgenic mouse models, making it a possible target for AD treatment [54]. CDK5 has several activators, one of which is p35 [50]. Truncation of p35 into a shorter p25 fragment is observed in AD [50]. Unlike p35, p25 leads to constitutive CDK5 activation [50, 53]. The p10 fragment lost from p35 upon conversion to p25 is involved in the mutually exclusive binding of p35 to microtubules or CDK5 [55, 56]. The p10 segment also facilitates Ca2 +-dependent binding between p35 and CaM, which not observed with p25 (Fig. 4) [55]. It is possible that p35 contains a novel CaMBD since no canonical binding motifs were identified upon sequence analysis of the p35 peptide sequence [55]. Moreover, in the model organism Dictyostelium discoideum, CDK5 itself was found to bind CaM in a Ca2 +-independent manner [57]. The two CaMBDs found in D. discoideum CDK5 are highly conserved in human CDK5 indicating that the same interaction likely occurs in the human brain [57].

The role of the well documented CaMBP PP2B in tau dephosphorylation was established early but recently has been relegated to a less important role with the discovery of other phosphatases linked to the process. More to the point, studies on the function of PP2B in tau dephosphorylation have been contradictory. PP2B is a heterodimer made of A and B subunits. The A subunit is catalytic and known to be activated by CaM in a Ca2 +-dependent manner through a 1–8–14 binding motif while the B subunit is regulatory and is itself largely homologous to CaM and able to bind Ca2 + ions [58, 59]. Early studies in vitro showed PP2B’s ability to dephosphorylate tau at positions including Ser262 and Ser369 (Fig. 4) [60–62]. However, when compared to other phosphatases such as protein phosphatase 2A (PP2A) and protein phosphatase 1 (PP1), it was found that PP2B is only responsible for 7% of the dephosphorylation activity which has been attributed to its low affinity toward tau [63]. Recent studies have reported an increased enzyme activity level of PP2B in AD brains [63]. While this seems contradictory to previous findings, this increase was ascribed to the increased levels of calpain I [64]. Calpain I is Ca2 + activated and its activity is increased in AD brains. It cleaves the A subunit of PP2B and renders it CaM-independent; the truncated form of PP2B has higher activity than the full length protein [64]. Therefore, the persistent high level of phosphorylation observed should indicate that PP2B does not play a major role in tau dephosphorylation. On the other hand, in vivo studies using PP2B-specific inhibitors resulted in hyperphosphorylated tau at positions including Ser262, Ser369, Thr181, and Thr231 [65–67]. To complicate matters further, CaM binding to PP2B, which normally activates the enzyme, was found to inhibit its association with tau [40].


Furthermore, the two enzymes CaMKII and PP2B have been implicated as central players in deficient memory storage that occurs due to the Ca2 + deregulation that occurs in AD individuals. These enzymes often act antagonistically by phosphorylating (CaMKII) and dephosphorylating (PP2B) the same proteins. Long-term potentiation (LTP) has been well studied in the mammalian hippocampus as it is the region of the brain that is critical in the formation and retrieval of various forms of memory. The morphology of hippocampal neurons including dendritic spine structures and their density are essential for memory storage. In the case of AD, progressive damage to the hippocampus results in an inability to form and store certain types of new memories concomitant with alterations in neuronal morphology, dendritic spine density, synapse formation, and deficits in LTP [68, 69]. Importantly, hyperactivation of the Ca2 +/CaM-dependent phosphatase calcineurin in the hippocampus has been reported for various models of AD and suggests that aberrant Ca2 + signaling contributes to deregulated interactions between CaM and calcineurin which impairs memory, increases tau phosphorylation and neuronal death [69, 70]. Short-term inhibition of calcineurin using the inhibitor FK506 was found to effectively reverse object recognition deficits in Tg2576 mice and improved dendritic spine loss, neuronal structure, and morphology in plaque bearing YFP-APP/PS1 transgenic mice [71]. Other work further demonstrated a direct connection between CaMKII activity in spines and spine loss in AD and aging brains [72]. Taken together, these data strongly suggest that the inhibition of calcineurin might protect hippocampal neurons and that the mechanism by which this occurs should be explored further. Recently, Berridge [73] has reviewed the positive role of CaMKII in memory formation and of PP2B in memory erasure. He has presented evidence arguing that the rapid memory erasure that occurs during wakefulness in AD individuals due to the action of PP2B prevents the ability of consolidating these memories during sleep which occurs in those not suffering from the disease. While much remains to be learned about this model, this again puts CaM and two of its primary targets— CaMKII and PP2B— at the center of issues facing those suffering from AD.


The oldest of all the models attempting to explain the causes and effects of AD, the “cholinergic hypothesis” is based on the decrease in acetylcholine neurocommunication [74, 75]. In AD, the levels of acetylcholine, acetylcholine receptors (AchR), and cholinergic neurons decrease [76]. Acetylcholine activates either inotropic nicotinic (nAchR) or metabotropic muscarinic (mAchR) receptors. The five subtypes (M1-M5) of mAchR are G-protein coupled receptors (GPCR) involved in Ca2 + signaling. M1 mAchR has been a primary therapeutic focus in the treatment of AD [77]. Like a number of verified GPCRs, M1 mAchR has a CaMBD on the cytoplasmic i3 loop [78]. Peptides derived from this intracellular loop bind to CaM. To date these peptides have not been used therapeutically. It should be noted that CaM also has indirect but major effects on the function of the mAchR first through regulation via phosphorylation (CaMKII) and dephosphorylation (PP2B) and second through more complex processes such as the formation of multiprotein complexes including the binding and activation of TRPC6 channels that are also involved in Ca2 + signaling [79].


The N-methyl-D-aspartate receptor (NMDAR) is a major Ca2 + channel involved in synaptic plasticity and memory [80, 81]. The receptor binds glutamate allowing cations to enter the cell [80]. NMDAR levels are generally reduced in AD, likely as an adaptive mechanism in response to the increased receptor activity due to Ca2 + dysregulation [82]. Likewise, Aβ can cause overactivation of the receptor leading to increased intracellular Ca2 + levels, an effect which can be reduced through NMDAR antagonists [83]. In addition to affecting Ca2 + homeostasis, NMDAR plays a role in the cell’s antioxidant response, where it can augment the cell’s defenses under conditions of oxidative stress [84]. On the other hand, overstimulation of the receptor can also lead to free radical generation which can be detrimental [85].

NMDAR is a heteromultimeric complex with the required presence of at least one monomer of each of NR1 and NR2. Different combinations of NR1 splice products and NR2 subunits vary among different cell types offering the receptor varied pharmacological and physiological properties [81]. CaM is capable of binding the NR1 subunit both in vitro and in vivo [86–88]. Binding occurs at two locations, both of which are in the cytoplasmic domain of NR1, reducing the mean time of the channel being open and the frequency at which it opens thus inhibiting Ca2 + entry [81]. While its specific regulatory role is being elucidated, Apo-CaM can associate with the NR1 subunit at a different site than Ca2 + dependent CaM binding. Upon Ca2 + entry activated Ca2 +/CaM induces a rapid structural shift in the NMDAR allowing for an efficient negative feedback cycle [89]. Binding of NR1 to CaM occurs through a novel 1–7 motif which is highly unusual and only observed in myristoylated alanine-rich C-kinase substrate (MARCKS) [90].


Recent genome wide association studies (GWAS) have linked certain gene polymorphisms with LOAD [91–94]. Although the specific functions of each gene and its encoded protein remain to be elucidated, most are involved either in cholesterol metabolism, neuroinflammation or endocytosis [95]. Using the Calmodulin Target Database, the proteins discussed below were found to be putative CaMBPs but most remain to be experimentally verified (Table 2).

Cholesterol metabolism

The brain is rich in cholesterol, containing approximately 25% of the body’s cholesterol content which is essential for myelin formation [96]. An association between cholesterol and AD was made when statins, which are used to treat elevated cholesterol levels, were found to reduce disease incidence [97]. Furthermore, levels of 24S-hydroxycholesterol, one of the first intermediates of cholesterol elimination, were higher in AD individuals than in healthy controls [98]. Since it cannot cross the blood-brain barrier, the brain’s cholesterol is internally synthesized and must be shuttled around by lipoproteins containing ApoE [96, 99]. ApoE contains two putative CaMBDs each with 2-3 potential binding motifs (Table 2). While the role of CaM binding in ApoE function remains to be clarified, it is well established that the ApoEɛ4 variant is a significant risk factor for LOAD.

Clusterin (CLU) and ATP-binding cassette transporter A7 (ABCA7) are two other proteins involved in cholesterol metabolism with polymorphisms which are risk factors for LOAD [91–93]. Each possesses a single putative CaMBD as revealed through Calmodulin Target Database analysis (Table 2). The CLU protein is multifunctional affecting immunity and apoptosis in addition to playing a role in lipid metabolism [100]. With its expression increased in AD, CLU (also termed apolipoprotein J) is a component of the lipid particles that transport cholesterol [101]. ABCA7 belongs to the ABC transporter superfamily, which regulates cholesterol transport across the cell membrane [102]. However, it is likely that the highly homologous protein ABCA1, which is a proven CaMBP, plays a more prominent role in this process than ABCA7, according to mouse models. Binding through a 1–5–8–14 motif, CaM affects the stability of ABCA1 in vivo, preventing its degradation [103].


Inflammation of neurons and dysregulation of different aspects of the immune response are characteristic of AD brains (reviewed in [104]). GWAS identified several proteins that affect the immune response. All were found through the Calmodulin Target Database to contain presumptive CaMBDs, although none have so far been experimentally tested to confirm the interaction with CaM (Table 2). Cluster of differentiation 33 (CD33), which is upregulated in microglial cells of AD brains, impairs Aβ clearance propagating plaque pathology [91, 105]. A second protein, the complement receptor 1 (Cr1) connects the complement system and CaM to AD although its exact role in propagation of pathology remains unknown [91, 106]. Moreover, polymorphisms in the membrane spanning 4-subfamily A (MS4A) proteins, MS4A4E and MS4A6A, were also found as risk factors for LOAD [91]. The function of the MS4A family remains poorly characterized, although, they may be components of Ca2 + channels and thus, affect Ca2 + homeostasis in neurons [107].

AβPP endocytosis

The AβPP protein is synthesized in the rough endoplasmic reticulum and travels through the trans-Golgi network to the cell membrane where it can be brought back into the cell through receptor-mediated endocytosis [108]. The exact subcellular location where Aβ is generated remains a topic of debate although endocytotic vesicles seem to be likely candidates since inhibition of endocytosis reduces the levels of Aβ produced [109]. A number of putative CaMBPs related to vesicle assembly were also identified including the phosphatidylinositol-binding clathrin assembly protein (PICALM), the scaffolding protein CD2-associated protein (CD2AP), the sortilin-related receptor L (SORL1), ephrin type-A receptor 1 (EPHA1), and the bridging integrator 1 (BIN1) (Table 2) [28]. To date, only BIN1 has been experimentally confirmed as a CaMBP[110].

AD, calmodulin, and the cell cycle

Although the amyloid cascade hypothesis dominates the AD research landscape, a number of alternative theories have been suggested in attempts to understand the pathogenesis of AD. In the developing brain neurons are integrated into complex synaptic networks after they have completed their proliferation, migration, and differentiation. The cellular signals that tightly regulate neuronal connectivity and plasticity also serve to ensure neurons are maintained in a differentiated state while simultaneously preventing reactivation of signaling pathways that control proliferation and cell cycle progression. The protection from aberrant neuronal cell cycle re-entry occurs through strict regulatory mechanisms at specific cell cycle control checkpoints. However, neuronal plasticity and formation of neuritic extensions allows for progression of the cycle early in G1 phase which is followed by opposing signals for re-differentiation back into G0. The mechanisms controlling transient re-entry into the cell cycle is considered to be an essential event for synaptic remodeling (reviewed in [111]).

In AD, the G1/S phase check-point regulatory mechanisms break down to the point where individual neurons can proceed through S-phase and undergo full or partial DNA re-replication with consequent entry into the G2 phase of the cell cycle [112–114]. Normally, in cycling non-neuronal cells, the G2 phase prepares the cell for mitosis, but in the case of post-mitotic neurons, improper cycling halts during the G2 phase and triggers neuronal death by apoptosis. Evidence from a number of animal models of human neurodegenerative disorders strongly suggests that atypical cell cycle re-entry events precede neuronal apoptosis ultimately leading to cell death [114–117]. Upregulation or improper protein degradation alters the normal level of a number of cell cycle proteins, including proliferating cell nuclear antigen (PCNA), cyclin D1, CDK4, and cyclin B1, within the hippocampus and other AD-diseased brain regions. These markers of cell cycle re-entry are not found randomly dispersed throughout the AD diseased brain nor are they detected in age-matched control patient brains [118, 119]. This ectopic cell cycle re-entry (CCR) is believed to account for a significant fraction of cortical neurons that are lost in AD [120]. Even more intriguing is that cell cycle markers are not only one of the earliest cellular abnormalities detected in AD, but theoretically may contribute to AD pathology including tau phosphorylation, Aβ formation, and neuronal calcium-ion dysfunction [121–123]. Seward et al. [124] further showed that CCR requires soluble Aβ, tau, and concomitant activation of kinases including the Ca2 +-calmodulin kinase II (CaMKII). This irregular cell cycle control within specific neuronal populations in the AD brain likely plays an early, yet crucial role for abnormalities associated with AD pathogenesis [117, 125, 126].

Studies in many cell types using a variety of approaches have implicated both Ca2 + and CaM as key regulators of distinct checkpoints in the cell cycle, including early G1, the G1 to S phase transition and G2/M transition. Calmodulin interactions with the CaMK family of CaMBPs act as important regulators of cell cycle progression (reviewed in [128]). Putative CaM-binding motifs have also been detected in a large number of cell cycle proteins including the cyclins (reviewed in [129]). Mitogenic stimulation leads to a variety of Ca2 +-CaM-mediated responses yet when the stimulation is permanent it causes changes in the sub-cellular distribution of CaM, which leads to changes in the total amount of CaM, alters cellular sensitivity to Ca2 + signals, and presents the potential for aberrant interactions between CaM and CaMBPs [130]. Although the deregulation of Ca2 +/calmodulin signaling in AD brains is not well understood, increased levels of CaM and decreased levels of phosphorylated CaMKII have been reported in the hippocampus of APP/PS1 mice [131]. These changes might be reflective of an aberrant involvement of CaM/CaMKII in the impairment of cell cycle control in AD. Indeed many different kinds of signaling pathways are changed in AD, and the relevance of the mitogenic upregulation that may induce cell cycle re-entry in the disease process is far from clear. Future studies will need to focus on identifying the mechanisms that regulate CaM and CaMKII expression in the hippocampus, as well as the downstream effector molecules involved, as this will potentially uncover new pathways for understanding the dysregulation of cell cycle control in ADbrains.


Since AD cannot be fully verified until autopsy, the search for minimally invasive biomarkers for the disease continues [132]. While cerebrospinal levels of Aβ, tau, and phosphorylated tau are effective biomarkers, this approach is fairly invasive and not without problems. Generally blood tests for those same biomarkers have been less than rewarding. Esteras et al. [133] have shown that levels of CaM are significantly increased in lymphoblasts from AD individuals. In a subsequent study, the increased CaM levels in lymphoblasts and peripheral blood mononuclear cells from AD individuals were found to be significantly greater than from non-dementia persons or those suffering from other types of dementia including amyotrophic lateral sclerosis, dementia with Lewy bodies, and frontotemporal dementi, among others [134]. These results suggest that CaM levels in peripheral blood cells have the potential to serve as a biomarker for various dementias including that resultingfrom AD.


Considering the multiple regulatory functions that CaM carries out in all cells, it is not surprising that it has many links to the underlying events of AD. CaM is involved in the defining aspects of AD progression and pathogenesis including Aβ generation, tau phosphorylation, Ca2 + homeostasis, cholesterol metabolism, neuroinflammation, AβPP endocytosis, and apoptosis. While it seems to present itself as a primary target in combating the symptoms and progression of the disease, many issues appear to reduce its current appeal as a therapeutic target. It has both positive and negative regulatory roles, making blanket inhibition approaches untenable. Thus currently available pharmaceutically proven CaM antagonists likely would not be an option for medical treatment. However, circumstances could change with the development of new CaM antagonists (e.g., [135]). Since most CaMBPs bind to CaM in unique ways and since some have multiple types of binding sequences, based on the technologies that exist for developing CaM antagonists it should be possible to develop target-specificpharmaceuticals.

The idea of targeting CaM and its CaMBPs is not without precedent. CaM is already a potential target for the treatment of Huntington’s disease, another neurodegenerative disease. Huntington’s disease is an autosomal dominant disorder due to a polyglutamine expansion in the huntingtin protein that is exacerbated by transglutaminase [136]. Huntingtin binds CaM and this binding can be disrupted using a CaM-peptide consisting of amino acids 76–121 of the CaM protein [137]. This peptide was then shown to reduce the level of transglutaminase-modified huntingtin and cytotoxicity in differentiated neuroblastoma (SH-SY5Y) cells. Subsequent treatment of a Huntington’s mouse (R6/2) model with this CaM-peptide led to neuroprotection via the mechanisms established in the tissue culture cells [138]. Thus CaM-Huntingtin binding appears to present a potential therapeutic target in combating this disease. The identification of critical CaMBPs linked to AD may also open a similardoor.


Robert J. Huber is thanked for his constructive comments on a draft of this manuscript. This work was supported by the Natural Sciences and Engineering Research Council of Canada (DHO’D; A6807).

Authors’ disclosures available online (



Brookmeyer R, Johnson E, Ziegler-Graham K, Arrighi HM2007Forecasting the global burden of Alzheimer’s diseaseAlzheimers Dement3186191


Hippius H, Neundörfer G2003The discovery of Alzheimer’s diseaseDialogues Clin Neurosci5101108


O’Day DH, Myre MA2004Calmodulin-binding domains in Alzheimer’s disease proteins: Extending the calcium hypothesisBiochem Biophys Res Commun23010511054


Myre MA, Tesco G, Tanzi RE, Wasco W2005Calmodulin binding to APP and the APLPs.: A Joint Biochemical Society/Neuroscience Ireland Focused Meeting; March 13-16, University College Dublin, Republic of IrelandMolecular Mechanisms of Neurodegeneration


Chavez SE, O’Day DH 2007 Current Research on Alzheimer’s Disease 37 47 Calmodulin binds to and regulates the activity of beta-secretase (BACE1) Volume 1 Issue 1/2 Nova Scienceublishers, Inc Hauppage, New York


Canobbio I, Catricalà S, Balduini C, Torti M2011Calmodulin regulates the non-amyloidogenic metabolism of amyloid precursor protein in plateletsBiochem Biophys Acta1813500506


Khachaturian ZS1994Calcium hypothesis of Alzheimer’s disease and brain agingAnn N Y Acad Sci747111


Gareri P, Mattace R, Nava F, De Sarro G1995Role of calcium in brain agingGen Pharmacol2616511657


Chin D, Means AR2000Calmodulin: A prototypical calcium sensorTrends Cell Biol10322328


Rhoads AR, Friedberg F1997Sequence motifs for calmodulin recognitionFASEB J11331340


Yap KL, Kim J, Truong K, Sherman M, Yuan T, Ikura M2000Calmodulin target databaseJ Struct Funct Genomics1814


Tidow H, Nissen P2013Structural diversity of calmodulin binding to its target sitesFEBS J28055515565


Villarroel A, Taglialatela M, Bernardo-Seisdedos G, Aliamo A, Agirre J, Alberdi A, Gomis-Perez C, Soldovieri MV, Ambrosino P, Malo C, Areso P2014The ever changing moods of calmodulin: How structurallasticity entails transductional adaptabilityJ Mol Biol42627172735


Hardy JA, Higgins GA1992Alzheimer’s disease: The amyloid cascade hypothesisScience256184185


Hardy J, Selkoe DJ2002The amyloid hypothesis of Alzheimer’s disease: Progress and problems on the road to therapeuticsScience297353356


Selkoe DJ2001Clearing the brain’s amyloid cobwebsNeuron32177180


Sunde M, Blake CC1998From the globular to the fibrous state: Protein structure and structural conversion in amyloid formationQ Rev Biophys31139


Kojro E, Fahrenholz F2005The non-amyloidogenic pathway: Structure and function of alpha-secretasesSubcell Biochem38105127


Dobson CM2004Protein chemistry. In the footsteps of alchemistsScience30412591262


Chow VW, Mattson MP, Wong PC, Gleichmann M2010An overview of APP processing enzymes and productsNeuromolecular Med12112


McLachlan DR, Wong L, Bergeron C, Baimbridge KG1987Calmodulin and calbindin D28K in Alzheimer diseaseAlzheimer Dis Assoc Discord1171179


Holsinger RM, McLean CA, Beyreyther K, Masters CL, Evin G2002Increased expression of the amyloid precursor beta-secretase in Alzheimer’s diseaseAnn Neurol51783786


Laird FM, Cai H, Savonenko AV, Farah MH, He K, Melnikova T, Wen H, Chiang HC, Xu G, Koliatsos VE, Borchelt DR, Price DL, Lee HK, Wong PC2005BACE1, a major determinant of selective vulnerability of the brain to amyloid-beta amyloidogenesis, is essential for cofnitive, emotional, and synaptic functionsJ Neurosci251169311709


Saito Y, Sano Y, Vassar R, Gandy S, Nakaya T, Yamamoto Y, Suzuki T2008X11 proteins regulate the translocation of amyloid beta-protein precursor (APP) into detergent-resistent membrane and suppress the amyloidogenic cleavage of APP by beta-site-cleaving enzyme in the brainJ Biol Chem2833576335771


Li H, Wolfe MS, Selkoe DJ2009Toward structural elucidation of the γ-secretase complexStructure17326334


Michno K, Knight D, Campusano JM, van de Hoef D, Boulianne GL2009Intracellular calcium deficits incholinergic neurons expressing wild type or FAD-mutant presenilinPLoS One4e6904


Pacheco-Quinto J, Eckman EA2013Endothelin-converting enzymes degrade intracellular β-amyloid produced within endosomal/lysosomal pathway and autophagosomesJ Biol Chem28856065615


O’Day DH, Myre MA 2007 Alzheimer’s Disease Research Trends Chan A Alzheimer’s disease: The calmodulin connection and β-amyloid Nova Biomedical Books NY 1 10


Berrocal M, Sepulveda MR, Vazquez-Hernandez M, Mata AM2012Calmodulin antagonizes amyloid-β peptides-mediated inhibition of brain plasma membrane Ca(2+)-ATPaseBiochim Biophys Acta1822961969


Nagano O, Murakami D, Hartmann D, De Strooper B, Saftig P, Iwatsubo T, Nakajima M, Shinohara M, Saya H2004Cell-matrix interaction via CD44 is independently regulated by different metalloproteinases activated in response to extraceullular Ca(2+) influx and PKC activationJ Cell Biol165893902


Kuhn PH, Wang H, Dislich B, Colombo A, Zeitschel U, Ellwart JW, Kremmer E, Rossner S, Lichtenthaler SF2010ADAM10 is the physiologically relevant, constitutive alpha-secretase of the amyloid precursor protein in primary neuronsEMBO J2930203032


Horiuchi K, Le Gall S, Schulte M, Yamaguchi T, Reiss K, Murphy G, Toyama Y, Hartmann D, Saftig O, Blobel CP2007Substrate selectivity of epidermal growth factor-receptor ligand sheddases and their regulation by phorbol esters and calcium influxMol Biol Cell18176188


Díaz-Rodríguez E, Esparís-Ogando A, Monero JC, Yuste L, Pandiella A2000Stimulation of cleavage of membrane proteins by calmodulin inhibitorsBiochem J346359367


Lee HG, Perry G, Moreira PI, Garrett MR, Liu Q, Zhu X, Takeda A, Nunomura A, Smith MA2005Tau phosphorylation in Alzheimer’s disease: Pathogen or protector?Trends Mol Med11164169


Martin L, Latypova X, Wilson CM, Magnaudeix A, Perrin M-L, Yardin C, Terro F2013Tau protein kinases; Involvement in Alzheimer’s diseaseAgeing Res Rev12289309


Padilla R, Maccioni RB, Avila J1990Calmodulin binds to a tubulin binding site of the microtubule-associated protein tauMol Cell Biochem973541


Baudier J, Mochly-Rosen D, Newton A, Lee SH, Koshland DEJr, Cole RD1987Comparison of S100b protein with calmodulin: Interactions with melittin and microtubule-associated tau roteins and inhibition ofhosphorylation of tau poteins by protein kinase CBiochemistry2628862893


Lee YC, Wolff J1984Calmodulin binds to both microtubule-associated protein 2 and tau proteinsJ Biol Chem25912261230


Mietelska-Porowska A, Wasik U, Goras M, Filipek A, Niewiadomska G2014Tau protein modifications and interactions: Their role in function and dysfunctionInt J Mol Sci154674146713


Yu DY, Tong L, Song GJ, Lin WL, Zhang LQ, Bai W, Gong H, Yin YX, Wei Q2008Tau binds both subunits of calcineurin, and binding is impaired by calmodulinBiochem Biophys Acta178322552261


Steiner B, Mandelkow EM, Biernat J, Gustke N, Meyer HE, Schmidt B, Mieskes G, Söling HD, Dreschsel D, Kirschner MW1990Phosphorylation of microtubule-associaed protein tau: Identification of the site for Ca2(+)-calmodulin dependent kinase and relationship with tau phosphorylation in Alzheimer tanglesEMBO J935393544


Singh TJ, Wang JZ, Novak M, Kontzekova E, Grundke-Iqbal I, Iqbal K1996Calcium/calmodulin-dependent protein kinase II phosphorylates au at Ser-262 but only partially inhibits its binding to microtubulesFEBS Lett387145148


Yamamoto H, Yamauchi E, Taniguchi H, Ono T, Miyamoto E2002Phosphorylation of microtubule-associaed protein tau by Ca2+/calmodulin-dependent protein kinase II in its tubulin binding sitesArch Biochem Biophys408255262


Yoshimura Y, Ichinose T, Yamauchi T2003Phosphorylation of tau protein to sites found in Alzheimer’s disease brain is catalyzed by Ca2+/calmodulin-dependent protein kinase II as demonstrated tandem mass spectrometryNeurosci Lett353185188


Yamamoto H, Hiragami Y, Murayama M, Ishizuka K, Kawahara M, Takashima A2005Phosphorylation of tau at serine 416 by Ca2+/calmodulin-dependent protein kinase II in neuronal soma in brainJ Neurochem9414381447


Straton MM, Chao LH, Schilman H, Kuriyan J2013Structural studies on the regulation of Ca2+/calmodulin dependent protein kinase IICurr Opin Sruct Biol23292301


Esteras N, Alquézar C, Bermejo-Pareja F, Bialopiotrowicz E, Wojda U, Martin-Requero A2013aDownregulation of extracellular signal-regulated kinase 1/2 activity by calmodulin KII modulates p21Cip1 levels and survival of immortalized lymphocytes from Alzheimer’s disease patientsNeurobiol Aging3410901100


Berchtold MW, Villalobo A2014The many faces of calmodulin in cell proliferation, programmed cell death, autophagy and cancerBiochim Biopys Acta1843398435


Lund ET, McKenna R, Evans DB, Sharma SK, Matthews WR2001Characterization of the in vitro phosphorylation of human tau by tau protein kinase II (cdk5/p20) using mass spectrometryJ Neurochem7612211232


Hashiguchi M, Saito T, Hisanaga S, Hashiguchi T2002Truncation of CDK5 activator p35 induces intensive phosphorylation of Ser202/Thr205 of human tauJ Biol Chem2774452544530


Noble W, Olm V, Takata K, Casey E, Mary O, Meyerson J, Gaynor K, Lafrancois J, Wang L, Kondo T, Davies P, Burns M, Nixon R, Dickson D2003Cdk5 is a key factor in tau aggregation and tangle formation in vivoNeuron38555565


Götz J, Nitsch RM2001Compartmentalized tau hyperphosphorylation and increased levels of kinases in transgenic miceNeuroreport1220072016


Patrick GN, Zukerberg L, Nikolic M, de la Monte S, Dikkes P, Tsai LH1999Conversion of p35 to p25 deregulates Cdk5 activity and promotes neurodegenerationNature402615622


Piedrahita D, Hernández I, López-Tobón A, Fedorov D, Obara B, Manjuath BS, Boudreau RL, Davidson B, LaFerla F, Gallego-Gómez JC, Kosik KS, Cardona-Gómez GP2010Silencing of CDK5 reduces neurofibrillary tangles in transgenic Alzheimer’s miceJ Neurosci301396613976


He L, Hou Z, Qi RZ2008Calmodulin binding and Cdk5 phosphorylation of p35 regulate its effect on microtubulesJ Biol Chem2831325213260


Hou Z, Li Q, He L, Lim HY, Fu X, Cheung NS, Qi DX, Qi RZ2007Microtubule association of the neuronal p35 activator of Cdk5J Biol Chem2821866618670


Huber RJ, Catalano A, O’Day DH2013Cyclin-dependent kinase 5 is a calmodulin-binding protein that associates with puromycin-sensitive aminopeptidase in the nucleus of DictyosteliumBiochem Biophys Acta18331120


Hoekman JD, Tokheim AM, Spannaus-Martin DJ, Martin BL2006Molecular modeling of the calmodulin binding region of calcineurinProtein J25175182


Klee CB, Ren H, Wang X1998Regulation of the calmodulin-stimulated protein phosphatase, calcineurinJ Biol Chem2731336713370


Drewes G, Mandelkow EM, Baumann K, Goris J, Merlevedede W, Mandelkow E1993Dephosphorylation of tau protein and Alzheimer paired helical filaments by calcineurin and phosphatase-2AFEBS Lett336425432


Gong CX, Singh TJ, Grundke-Iqbal I, Iqbal K1994Alzheimer’s disease abnormally phosphorylated tau is dephosphorylated by protein phosphatase-2B (calcineurin)J Neurochem62803806


Rahman A, Grundke-Iqbal I, Iqbal K2006PP2B isolated from human brain preferentially dephosphorylates Ser-262 and Ser-396 of the Alzheimer disease abnormally hyperphosphorylated tauJ Neural Transm113219230


Liu F, Grundke-Iqbal I, Iqbal K2005Contributions of protein phosphatases PP1, PP2A, PP2B and PP5 to the regulation of tau phosphorylationEur J Neurosci2219421950


Liu F, Grundke-Iqbal I, Iqbal K, Oda K, Tomizawa Y, Gong K, CX 2005Truncation and activation of calcineurin A by calpain I in Alzheimer disease brainJ Biol Chem2803775537762


Garver TD, Kincaid RL, Conn RA, Billingsley ML1999Reduction of calcineurin activity in brain by antisense oligonucleotides leads to persistent phosphorylation of tau protein at Thr181 and Thr231Mol Pharmacol55632641


Yu DY, Luo J, Bu F, Song GJ, Zhang LQ, Wei Q2006Inhibition of calcineurin by infusion of CsA causes hyperphosphorylation of tau and is accompanied by abnormal behavior in miceBiol Chem387977983


Luo J, Ma J, Yu DY, Bu F, Zhang W, Tu LH, Wei Q2008Infusion of FK506, a specific inhibitor of calcineurin, induces potent tau hyperphosphorylation in mouse brainBrain Res Bull76464468


Koffie RM, Hyman BT, Spires-Jones TL2011Alzheimer’s disease: Synapses gone coldMol Neurodegener663


Reese LC, Taglialatela G2011A role for calcineurin in Alzheimer’s diseaseCurr Neuropharmacol9685692


Wu HY, Hudry E, Hashimoto T, Kuchibhotla K, Rozkalne A, Fan Z, Spires-Jones T, Xie H, Arbel-Ornath M, Grosskreutz CL, Bacskai BJ, Hyman BT2010Amyloid beta induces the morphological neurodegenerative triad of spine loss, dendritic simplification, and neuritic dystrophies through calcineurin activationJ Neurosci3026362649


Rozkalne A, Hyman BT, Spires-Jones TL2011Calcineurin inhibition with FK506 ameliorates dendritic spine density deficits in plaque-bearing Alzheimer model miceNeurobiol Dis41650654


Sun S, Zhang H, Liu J, Popugaeva E, Xu NJ, Feske S, White CL3rd, Bezprozvanny I2014Reduced synaptic STIM2 expression and impaired store-operated calcium entry cause destabilization of mature spines in mutant presenilin miceNeuron827993


Berridge MJ2014Calcium regulation of neural rhythms, memory and Alzheimer’s diseaseJ Physiol592281293


Richter JA, Perry EK, Tomlinson BE1980Acetylcholine and choline levels in post-mortem human brain tissue: Preliminary observations in Alzheimer’s diseaseLife Sci2616831689


Francis PT, Palmer AM, Snape M, Wilcock GK1999The cholinergic hypothesis of Alzheimer’s disease: A review of progressJ Neurol Neurosurg Psychol66137147


Jiang S, Li Y, Zhang C, Zhao Y, Bu G, Xu H, Zhang Y-W2014M1 muscarinic acetycholine receptor in Alzheimer’s diseaseNeurosci Bull30295307


Anand P, Singh B2013A review on cholinesterase inhibitors for Alzheimer’s diseaseArch Pharm Res36375399


Lucas JL, Wang D, Sadée W2006Calmodulin binding to peptides derived from the i3 loop of muscarinic receptorsPharmaceutical Res23647653


Kim JY, Saffen D2005Activation of M1 muscarinic acetylcholine receptors stimulates the formation of a multiprotein complex centered on TRPC6 channelsJ Biol Chem20803203532047


Zito K, Scheuss V2009NMDA receptor function and physiological modulationSquire LThe New Encyclopedia of NeuroscienceElsevier


Ehlers MD, Zhang S, Bernhadt JP, Hunganir RL1996Inactivation of NMDA receptors by direct interaction of calmodulin with the NR1 subunitCell84745755


Danysz W, Parsons CG2012Alzheimer’s disease, β-amyloid, glutamate, NMDA receptors and memantine— searching for the connectionsBrit J Pharmacol167324352


Alberdi E, Sánchez-Gómez MV, Cavaliere F, Pérez-Samartin A, Zugaza JL, Trullas R, Domercg M, Matute C2010Amyloid beta oligomers induce Ca2+ dysregulation and neuronal death through activation of ionotropic glutamate receptorsCell Calcium47264272


Papadia S, Soriano FX, Láveillé F, Martel MA, Dakin KA, Hansen HH, Kaindl A, Sifringer M, Fowler J, Stefovska V, McKenzie G, Craigon M, Corriveau R, Ghazal P, Horsburgh K, Yankner BA, Wyllie DJ, Ikonomidou C, Hardingham GE2008Synaptic NMDA receptor activity boosts intrinsic antioxidant defensesNat Neurosci11476478


Gonzalez J, Jurado-Coronel JC, Avila MF, Sabogal A, Capani F, Barreto GE2014NMDARs in neurological diseases: A potential therapeutic targetInt J Neurosci124717723


Hisatsune C, Umemori H, Inoue T, Michikawa T, Kohda K, Mikoshiba K, Yamamoto T1997Phosphorylation-dependent regulation of N-methyl-D-aspartate receptors by calmodulinJ Biol Chem2722080520810


Rycroft BK, Gibb AJ2002Direct effects of calmodulin on NMDA receptor single-channel gating in rat hippocampal granule cellsJ Neurosci2288608868


Zhang S, Huganir RL1999Calmodulin modification of NMDA receptorsMethods Mol Biol128103111


Akyol Z, Bartos JA, Merrill MA, Faga LA, Jaren OR, Shea MA, Hell JW2004Apo-calmodulin binds with its C-terminal domain to the N-methyl-D-aspartate receptor NR1 C0 regionJ Biol Chem27921662175


Ataman ZA, Gakhar L, Sorensen BR, Hell JW, Shea MA2007The NMDA receptor NR1 C1 region bound to calmodulin: Structural insights into functional differences between homologous domainsStructure1516031617


Harold D, Abraham R, Hollingworth R, Sims R, Gerrish A, Hamshere M, Pahwa JS, Moskvina V, Dowzell K, Williams A, Jones N, Thomas C, Stretton A, Morgan A, Lovestone S, Powell J, Proitsi P, Lupton MK, Brayne C, Rubinsztein DC, Gill M, Lawlor B, Lynch A, Morgan K, Brown K, Passmore P, Craig D, McGuinness B, Todd S, Holmes C, Mann D, Smith AD, Love S, Kehoe PG, Hardy J, Mead S, Fox N, Rossor M, Collinge J, Maier W, Jessen F, Schürmann B, van den Bussche H, Heuser I, Kornhuber J, Wiltfang J, Dichgans M, Frölich M, Hampel H, Hüll M, Rujescu D, Goate A, Kauwe JSK, Cruchaga C, Nowotny P, Morris JC, Mayo K, Sleegers K, Bettens K, Engelborghs S, De Deyn P, van Broeckhoven C, Livingston G, Bass NJ, Gurling H, McQuillin Q, Gwilliam R, Deloukas P, Al-Chalabi A, Shaw CE, Tsolaki M, Singleton A, Guerreiro R, Mühleisen TW, Nöthen MM, Moebus S, Jöckel K-H, Klopp N, Wichmann H-E, Carrasquillo MM, Pankratz VS, Younkin SG, Holmans P, O’Donovan M, Owen MJ, Williams J2009Genome-wide association study identifies variants at CLU and PICALM associated with Alzheimer’s diseaseNat Genet4110881093


Naj AC, Jun G, Beecham GW, Wang L-S, Vardarajan BN, Buros J, Gallins PJ, Buxbaum JD, Jarvik GP, Crane PK, Larson EB, Bird TD, Boeve BF, Graff-Radford NR, Philip L, De Jager PL, Denis Evans D, Julie A, Schneider JA, Carrasquillo MM, Ertekin-Taner N, Younkin SG, Cruchaga C, Kauwe JSK, Nowotny P, Kramer P, Hardy J, Huentelman MJ, Myers AJ, Barmada MM, Demirci FY, Baldwin CT, Green RC, Rogaeva E, St George-Hyslop P, Arnold SE, Barber R, Beach T, Bigio EH, Bowen J, Boxer JD, Burke A, Cairns JR, Carlson NJ, Carney CS, Carrol RM, Chui SL, Clark HC, Corneveaux DG, Cotman J, Cummings CW, DeCarli JL, DeKosky C, Diaz-Arrastia ST, Dick R, Dickson M, Ellis DW, Faber WG, Fallon KM, Farlow KB, Ferris MR, Frosch S, Galasko MP, May Ganguli DR, Gearing M, Geschwind M, Ghetti DH, Gilbert B, Gilman JR, Giordani S, Glass B, Growdon JD, Hamilton JH, Harrell RL, Head LE, Honig E, Hulette LS, Hyman CM, Jicha BT, Jin GA, Johnson L-W, Karlawish N, Karydas J, Kaye A, Kim JA, Koo R, Kowall EH, Lah NW, Levey JL, Lieberman AI, Lopez AP, Mack OL, Marson WJ, Martiniuk DC, Mash F, Masliah DC, McCormick E, McCurry WC, McDavid SM, McKee AN, Mesulam AC, Miller M, Miller BL, Miller CA, Parisi JW, Perl JE, Peskind DP, Petersen E, Poon RC, WW , Quinn J, Rajbhandary JF, Raskind RA, Reisberg M, Ringman B, Roberson JM, Rosenberg ED, Sano RN, Schneider M, Seeley LS, Shelanski W, Slifer ML, Smith MA, Sonnen CD, Spina JA, Stern S, RA , Tanzi R, Trojanowski RE, Troncoso JQ, Van Deerlin JC, Vinters VM, Vonsattel HV, Weintraub JP, Welsh-Bohmer S, Williamson KA, Woltjer J, Cantwell RL, Dombroski LB, Beekly BA, Lunetta DB, Martin KL, Kamboh ER, Saykin MI, Reiman AJ, Bennett EM, Morris DA, Montine JC, Goate TJ, Blacker AM, Tsuang D, Hakonarson DW, Kukull H, Foroud WA, Haines TM, JL , Pericak-Vance1 R, Farrer MA, Schellenberg LA, GD 2011Common variants at MS4A4/MS4A6E, CD2AP, CD33 and EPHA1 are associated with late-onset Alzheimer’s diseaseNat Genet43436441


Hollingworth P, Harold D, Sims R, Gerrish A, Lambert J-C, Carrasquillo MM, Abraham R, Hamshere ML, Pahwa JS, Moskvina V, Dowzel K, Jones N, Stretton A, Thomas C, Richards A, Ivanov D, Widdowson C, Chapman J, Lovestone S, Powell J, Proitsi P, Lupton MK, Brayne C, Rubinsztein DC, Gill M, Lawlor B, Lynch A, Brown KS, Passmore PA, Craig D, McGuinness B, Todd S, Holmes C, Mann D, Smith AD, Beaumont H, Warden D, Wilcock G, Love S, Kehoe PG, Hooper NM, Vardy ERLC, Hardy J, Mead S, Fox NC, Rossor M, Collinge J, Maier W, Jessen F, Schürmann B, Rüther E, Heun R, Kölsch H, van den Bussche H, Heuser I, Kornhuber J, Wiltfang J, Dichgans M, Frölich L, Hampel H, Hüll M, Gallacher J, Rujescu D, Giegling I, Goate AM, Kauwe JSK, Cruchaga C, Nowotny P, Morris JC, Mayo K, Sleegers K, Bettens K, Engelborghs S, De Deyn PP, Van Broeckhoven C, Livingston G, Bass J, Gurling NJ, McQuillin H, Gwilliam A, Deloukas R, Al-Chalabi P, Shaw A, Tsolaki CE, Singleton M, Guerreiro AB, Mühleisen R, Nöthen TW, Moebus MM, Jöckel S, Klopp K-H, Wichmann N, Pankratz H-E, Sando VS, Aasly SB, Barcikowska JO, Wszolek M, Dickson ZK, Graff-Radford DW, Petersen NR, the Alzheimer’s Disease Neuroimaging Initiative RCvan Duijn CM, Breteler MMB, Ikram MA, DeStefano AL, Fitzpatrick AL, Lopez O, Launer LJ, Seshadri S, consortium CHARGEBerr C, Campion D, Epelbaum J, Dartigues J-F, Tzourio C, Alpérovitch A, Lathrop M, EADI1 consortiumFeulner TM, Friedrich P, Riehle C, Krawczak M, Schreiber S, Mayhaus M, Nicolhaus S, Wagenpfeil S, Steinberg S, Stefansson H, Stefansson K, Snædal J, Björnsson S, Jonsson PV, Chouraki V, Genier-Boley B, Hiltunen M, Soininen H, Combarros O, Zelenika D, Delepine M, Bullido MJ, Pasquier F, Mateo I, Frank-Garcia AF, Porcellini E, Hanon O, Coto E, Alvarez V, Bosco P, Siciliano G, Mancuso M, Panza F, Solfrizzi V, Nacmias B, Sorbi S, Bossù P, Piccardi P, Arosio B, Annoni G, Seripa D, Pilotto A, Scarpini E, Galimberti D, Brice A, Hannequin D, Licastro F, Jones L, Holmans PA, Jonsson T, Riemenschneider M, Morgan K, Younkin SG, Owen MJ, O’Donovan M, Amouyel P, Williams J2011Common variants at ABCA7, MS4A6A/MS4A4E, EPHA1, CD33 and CD2AP are associated with Alzheimer’s diseaseNat Genet43429435


Lambert J-C, Ibrahim-Verbaas CA, Harold D, Naj AC, Sims R, Bellenguez C, Jun G, DeStefano AL, Bis JC, Beecham GW, Grenier-Boley B, Russo G, Thornton-Wells TA, Jones N, Smith AV, Chouraki V, Thomas C, Ikram MA, Zelenika D, Vardarajan BN, Kamatani Y, Lin C-F, Gerrish A, Schmidt H, Kunkle B, Dunstan ML, Ruiz A, Bihoreau MT, Choi S-H, Reitz C, Pasquier F, Hollingworth P, Ramirez A, Hanon O, Fitzpatrick AL, Buxbaum JD, Campion D, Crane PK, Baldwin C, Becker T, Gudnason V, Cruchaga C, Craig D, Amin N, Berr C, Lopez OL, De Jager PL, Deramecourt V, Johnston JA, Evans D, Lovestone S, Letenneur L, Morón FJ, Rubinsztein DC, Eiriksdottir G, Sleegers K, Goate AM, Fiévet N, Huentelman MJ, Gill M, Brown K, Kamboh MI, Keller L, Barberger-Gateau P, McGuinness B, Larson EB, Green R, Myers AJ, Dufouil C, Todd S, Wallon D, Love S, Rogaeva E, Gallacher J, St George-Hyslop P, Clarimon J, Lleo A, Bayer A, Tsuang DW, Yu L, Tsolaki M, Bossù P, Spalletta G, Proitsi P, Collinge PJ, Sorbi S, Sanchez-Garcia F, Fox NC, Hardy J, Naranjo MCD, Bosco P, Clarke R, Brayne C, Galimberti D, Mancuso M, Matthews F, European Alzheimer’s disease Initiative (EADI)Genetic, Environmental Risk in Alzheimer’s Disease (GERAD)Alzheimer’s Disease Genetic Consortium (ADGC)Cohorts for HeartAging Research in Genomic Epidemiology (CHARGE)Moebus S, Mecocci P, Del Zompo M, Maier W, Hampel H, Pilotto A, Bullido M, Panza F, Caffarra P, Nacmias B, Gilbert JR, Mayhaus M, Lannfelt L, Hakonarson H, Pichler S, Carrasquillo MM, Ingelsson M, Beekly D, Alvarez V, Zou F, Valladares O, Younkin SG, Coto E, Hamilton-Nelson K-L, Gu W, Razquin C, Pastor P, Mateo I, Owen MJ, Faber KM, Jonsson PV, Combarros O, O’Donovan MC, Cantwell LB, Soininen H, Blacker D, Mead S, Mosley TH, Bennett DA, Harris TB, Fratiglioni L, Holmes C, de Bruijn RFAG, Passmore P, Montine TJ, Bettens K, Rotter JI, Brice A, Morgan K, Foroud TM, Kukull WA, Hannequin D, Powell JF, Nalls MA, Ritchie KR, Lunetta KL, Kauwe1 JSK, Boerwinkle E, Riemenschneider M, Boada M, Hiltunen M, Martin ER, Schmidt R, Rujescu D, Wang L-S, Dartigues J-F, Mayeux R, Tzourio C, Hofman A, Nöthen MM, Graff C, Psaty BM, Jones L, Haines JL, Holmans PA, Lathrop M, Pericak-Vance MA, Launer LJ, Farrer LA, van Duijn CM, Van Broeckhoven C, Moskvina V, Seshadri S, Williams J, Schellenberg GD, Amouyel P2013Meta-analysis of 74,046 individuals identifies 11 new susceptibility loci for Alzheimer’s diseaseNat Genet4514521458


Karch CM, Goate AM2015Alzheimer’s disease risk genes and mechanisms of disease pathogenesisBiol Psychiatry774351


Kang J, Rivest S2012Lipid metabolism and neuroinflammation in Alzheimer’s disease: A role for liver X receptorsEndocr Rev33715746


Fassbender K, Simons M, Bergmann C, Stroick M, Lutjohan D, Keller P, Runz H, Kuhl S, Bertsch T, von Gergmann K, Hennerici M, Meyreuther K, Hartman T2001Simvastatin strongly reduces levels of Alzheimer’s disease beta-amyloid peptides Abeta 42 and Abeta 40 in vitro and in vivoProc Nat Acad Sci U S A9858565861


Schönknecht P, Lütjohann D, Pantel J, Bardenheuer H, Hartmann T, von Bergmann K, Beyreuther K, Schröder J2002Cerebrospinal fluid 24S-hydroxycholesterol is increased in patients with Alzheimer’s disease compared to healthy controlsNeurosci Lett3248385


Jurevics H, Morell P1995Cholesterol for synthesis of myelin is made locally, not imported into brainJ Neurochem64895901


Jones SE, Jomary C2002ClusterinInt J Biochem Cell Biol34427431


Nuutinen T, Suuronen T, Kauppinen A, Salminen A2009Clusterin: A forgotten player in Alzheimer’s diseaseBrain Res Rev6189104


Kim WS, Weickert CS, Garner B2008Role of ATP-binding cassette transporters in brain lipid transport and neurological diseaseJ Neurochem10411451166


Iwamoto N, Lu R, Abe-Dohmae S, Yokoyama S2010Calmodulin interacts with ATP binding cassette transporter A1 to protect from calpain-mediated degradation and upregulates high-density lipoprotein generationArterioscler Thromb Vasc Biol3014461452


Akiyama H, Barger S, Barnum S, Bradt B, Bauer J, Cole GM, Cooper NR, Eikelenboom P, Emmerling M, Fiebich BL, Finch CE, Frautschy S, Griffin WS, Hampel H, Hull M, Landreth G, Lue L, Mrak R, Mackenzie IR, McGeer PL, O’Banion MK, Pachter J, Pasinetti G, Plata-Salaman C, Rogers J, Rydel R, Shen Y, Streit W, Strohmeyer R, Tooyoma I, Van Muiswinkel FL, Veerhuis R, Walker D, Webster S, Wegrzyniak B, Wenk G, Wyss-Coray T2000Inflammation and Alzheimer’s diseaseNeurobiol Aging21383421


Jiang T, Yu JT, Hu N, Tan MS, Zhu XC, Tan L2014CD33 in Alzheimer’s diseaseMol Neurobiol49529535


Crehan H, Holton P, Wray S, Pocock J, Guerreiro R, Hardy J2012Complement receptor 1 (CR1) and Alzheimer’s diseaseImmunobiology217244250


Ma J, Yu JT, Tan L2014MS4A cluster in Alzheimer’s diseaseMol Neurobiol10.1007/s12035-014-8800-z


Choy RW, Cheng Z, Schekman R2012Amyloid precursor protein (APP) traffics from the cell surface via endosomes for amyloid β (Aβ) production in the trans-Golgi networkProc Natl Acad Sci U S A109E2077E2082


Carey RM, Balcz BA, Lopez-Coviella I, Slack BE2005Inhibition of dynamin-dependent endocytosis increases shedding of the amyloid precursor protein ectodomain and reduces generation of amyloid beta proteinBMC Cell Biol630


Berggård T, Arrigoni G, Olsson O, Fex M, Linse S, James P2006140 mouse brain proteins identified by Ca2+-calmodulin affinity chromatography and tandem mass spectrometryJ Proteome Res5669687


Arendt T2005Alzheimer’s disease as a disorder of dynamic brain self-organizationProg Brain Res147355378


Nagy Z2000Cell cycle regulatory failure in neurones: Causes and consequencesNeurobiol Aging21761769


Zhu X, McShea A, Harris PL, Raina AK, Castellani RJ, Funk JO, Shah S, Atwood C, Bowen R, Bowser R, Morelli L, Perry G, Smith MA2004Elevated expression of a regulator of the G2/M phase of the cell cycle, neuronal CIP-1-associated regulator of cyclin B, in Alzheimer’s diseaseJ Neurosci Res75698703


Yang Y, Geldmacher DS, Herrup K2001DNA replication precedes neuronal cell death in Alzheimer’s diseaseJ Neurosci2126612668


Nagy ZS, Esiri MM1997Apoptosis-related protein expression in the hippocampus in Alzheimer’s diseaseNeurobiol Aging18565571


Raina AK, Hochman A, Zhu X, Rottkamp CA, Nunomura A, Siedlak SL, Boux H, Castellani RJ, Perry G, Smith MA2001Abortive apoptosis in Alzheimer’s diseaseActa Neuropathol101305310


Herrup K, Neve R, Ackerman SL, Copani A2004Divide and die: Cell cycle events as triggers of nerve cell deathJ Neurosci2492329239


Busser J, Geldmacher DS, Herrup K1998Ectopic cell cycle proteins predict the sites of neuronal cell death in Alzheimer’s disease brainJ Neurosci1828012807


Khurana V, Lu Y, Steinhilb ML, Oldham S, Shulman JM, Feany MB2006TOR-mediated cell-cycle activation causes neurodegeneration in atauopathy modelCurr Biol16230241


Arendt T, Bruckner MK, Mosch B, Losche A2010Selective cell death of hyperploid neurons in Alzheimer’s diseaseAm J Pathol1771520


Walsh DM, Selkoe DJ2004Deciphering the molecular basis of memory failure in Alzheimer’s diseaseNeuron44181193


Zhu X, Rottkamp CA, Boux H, Takeda A, Perry G, Smith MA2000Activation of p38 kinase links tau phosphorylation, oxidative stress, and cell cycle-related events in Alzheimer diseaseJ Neuropathol Exp Neurol59880888


Mattson MP, Chan SL2003Neuronal and glial calcium signaling in Alzheimer’s diseaseCell Calcium34385397


Seward ME, Swanson E, Norambuena A, Reimann A, Cochran JN, Li R, Roberson ED, Bloom GS2013Amyloid-β signals through tau to drive ectopic neuronal cell cycle re-entry in Alzheimer’s diseaseJ Cell Sci12612781286


Yang Y, Varvel NH, Lamb BT, Herrup K2006Ectopic cell cycle events link human Alzheimer’s disease and amyloid precursor protein transgenic mouse modelsJ Neurosci26775784


Lee HG, Casadesus G, Zhu X, Castellani RJ, McShea A, Perry G, Petersen RB, Bajic V, Smith MA2009Cell cycle re-entry mediated neurodegeneration and its treatment role in the pathogenesis of Alzheimer’s diseaseNeurochem Int 548488


Kahl CR, Means AR2003Regulation of cell cycle progression by calcium/calmodulin-dependent pathwaysEndocr Rev24719736


Skelding KA, Rostas JA, Verrills NM2011Controlling the cell cycle: The role of calcium/calmodulin-stimulated protein kinases I and IICell Cycle4631639


Choi J, Husain M2006Calmodulin-mediated cell cycle regulation: New mechanisms for old observationsCell Cycle521832186


Gnegy ME1993Calmodulin in neurotransmitter and hormone actionAnnu Rev Pharmacol Toxicol334570


Min D, Guo F, Zhu S, Xu X, Mao X, Cao Y, Lv X, Gao Q, Wang L, Chen T, Shaw C, Hao L, Cai J2013The alterations of Ca2+/calmodulin/CaMKII/CaV1.2 signaling in experimental models of Alzheimer’s disease and vascular dementiaNeurosci Lett5386065


Young AL, Oxtoby NP, Daga P, Cash DM, Fox NC, Ourselin S, Schott JM, Alexander DC2014A data-driven model of biomarker changes in sporadic Alzheimer’s diseaseBrain13725642577


Esteras N, Munoz U, Alquézar C, Bartolome F, Bermejo-Pareja F, Martin-Requero A2012Altered calmodulin degradation and signaling in non-neuronal cells from Alzheimer’s disease patientsCurr Alzheimer Res9267277


Esteras N, Alquézar C, de la Encarnación A, Vallarejo A, Bermejo-Pareja F, Martin-Requero A2013Calmodulin levels in blood cells as a potential marker of Alzheimer’s diseaseAlzheimers Res Ther555


Audran E, Dagher R, Gioria S, Tsvetkov PO, Kulikova AA, Didier B, Villa P, Makarov AA, Kilhoffer M-C, Haiech J2013A general framework to characterize inhibitors of calmodulin: Use of calmodulin inhibitors to study the interaction between calmodulin and its calmodulin binding domainsBiochim Biophys Acta183317201731


Walling HW, Baldassare JJ, Westfall TC1998Molecular aspects of Huntington’s diseaseJ Neurosci Res50301308


Dudek NL, Dai Y, Muma NA2008Protective effects of interrupting the binding of calmodulin to mutant huntingtinJ Neuropathol Exp Neurol67355365


Dudek NL, Dai Y, Muma NA2010Neuroprotective effects of calmodulin peptide 76-121aa: Disruption of calmodulin binding to mutant huntingtinBrain Pathol20176189

Figures and Tables


Calcium-bound calmodulin (CaM) and its calcium-free form (Apo-CaM) are involved to many central events linked to Alzheimer’s disease as discussed in this review.

Calcium-bound calmodulin (CaM) and its calcium-free form (Apo-CaM) are involved to many central events linked to Alzheimer’s disease as discussed in this review.

Apo-Calmodulin (Apo-CaM) can bind up to two calcium ions in each of its N-term (pink) or C-term lobes (green). These binding options affect the conformation of CaM and its ability to bind to specific target CaM-binding proteins.

Apo-Calmodulin (Apo-CaM) can bind up to two calcium ions in each of its N-term (pink) or C-term lobes (green). These binding options affect the conformation of CaM and its ability to bind to specific target CaM-binding proteins.

Calmodulin binding proteins linked to the amyloidogenenic and non-amyloidogenic pathways. amyloid-β precursor protein (AβPP); anterior pharynx defective 1 (APH-1); β site-amyloid converting enzyme 1 or β-secretase (BACE1); A Disintegrin And Metalloproteinase Family (ADAM 9,10,17, 19); endothelin-converting enzyme (ECE); insulin-degrading enzyme (IDE); nicastrin (Nic); presenilin enhancer protein 2 (PEN-2); and presenilin-1 (PSN-1); superscripts:  *putative CaMBD detected; vCaMBD experimentally verified.

Calmodulin binding proteins linked to the amyloidogenenic and non-amyloidogenic pathways. amyloid-β precursor protein (AβPP); anterior pharynx defective 1 (APH-1); β site-amyloid converting enzyme 1 or β-secretase (BACE1); A Disintegrin And Metalloproteinase Family (ADAM 9,10,17, 19); endothelin-converting enzyme (ECE); insulin-degrading enzyme (IDE); nicastrin (Nic); presenilin enhancer protein 2 (PEN-2); and presenilin-1 (PSN-1); superscripts:  *putative CaMBD detected; vCaMBD experimentally verified.

Calmodulin binding proteins linked to tau phosphorylation. Calmodulin-dependent kinase II (CaMKII); cyclin-dependent kinase 5 (CDK5); calmodulin (CaM); neurofibrillary tangles (NFTs); CDK5 activator (P35); protein phosphatase 2B (PP2B); colors: green, stimulated/activated; red, inhibited.

Calmodulin binding proteins linked to tau phosphorylation. Calmodulin-dependent kinase II (CaMKII); cyclin-dependent kinase 5 (CDK5); calmodulin (CaM); neurofibrillary tangles (NFTs); CDK5 activator (P35); protein phosphatase 2B (PP2B); colors: green, stimulated/activated; red, inhibited.
Table 1

Calmodulin binding domain (CaMBD) subclasses that have been identified and experimentally verified

Table 2

Putative calmodulin binding domain (CaMBD) classes in GWAS proteins linked to Alzheimer’s disease. Appropriate hydrophobic (green), acidic (yellow), and IQ (cyan) amino acids are highlighted.