Affiliations: Department of Biochemistry and Biomedical Sciences, Seoul National University, College of Medicine, Seoul, Republic of Korea
Correspondence:
[*]
Correspondence to: Inhee Mook-Jung, PhD, Department of Biochemistry and Biomedical Sciences, Seoul National
University, College of Medicine, 103 Daehak-ro, Jongro-gu, Seoul 110-799, Republic of Korea. Tel.: +82 2 740
8245; Fax: +82 2 3672 7352; E-mail: [email protected].
Abstract: Increased levels of total tau (t-tau) and hyperphosphorylated tau (p-tau) proteins in the cerebrospinal fluid of Alzheimer’s disease (AD) patients are well documented and strongly correlate with AD pathology. Recent studies have further shown that human tau can be released into the extracellular space and transferred to nascent neurons. However, because the tau protein has no signal peptide identity, the mechanisms underlying its secretion remain poorly understood. In the present study, we confirmed that tau protein secretion was promoted by autophagy inducers and downregulated by beclin1 knockdown or autophagy inhibitors derived from human wild type tau (wt-tau)-overexpressing SH-SY5Y cells. Moreover, both t-tau and p-tau secretion were increased by autophagy activation. Furthermore, we identified that six isoforms of tau protein are secreted in an autophagy-dependent manner. These results indicate that both normal and pathological tau are secreted via an autophagy-mediated secretory pathway in neurons. Understanding this new pathway for tau secretion may provide critical future insights into tau pathologies, such as AD.
Keywords: Alzheimer’s disease, autophagy-mediated secretion, beclin1, SH-SY5Y
cells, tau protein
