Affiliations: Department of Biochemistry and Molecular Biology,
School of Biomedical Sciences, Monash University, Wellington Road, Melbourne,
VIC 3800, Australia
Note: [] Present address: Eijkman Institute for Molecular Biology, Jl.
Diponegoro 69, Jakarta 10430, Indonesia
Note: [] Present address: Victorian Breast Cancer Research Consortium,
The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade,
Melbourne, VIC 3050, Australia
Abstract: The mammalian plasma membrane (PM) NADH-oxidoreductase (PMOR) system
is a multi-enzyme complex located in the plasma membrane of all eukaryotic
cells, harboring at least two distinct activities, the plasma membrane
NADH-ferricyanide reductase and the NADH-oxidase. To assess the behaviour of
the two activities of the PMOR system, we measured the NADH-ferricyanide
reductase and NADH-oxidase activities in fibroblast cell lines derived from
patients carrying a mitochondrial DNA (mtDNA) G11778A mutation. We also
measured the two activities in other cell lines, the HL-60 and HeLa (S3) lines,
as well as in ρ^0 cells (cells devoid of mtDNA) generated
from those lines and the fibroblast cells. These ρ^0
cells consequently lack oxidative phosphorylation and rely on anaerobic
glycolysis for their ATP need. We have proposed that in
ρ^0 cells, at least in part, up-regulation of the PMOR is
a necessity to maintain the NAD^+/NADH ratio, and a
pre-requisite for cell growth and viability. We show here that the PM
NADH-ferricyanide reductase activity was up-regulated in HL-AV2 (HL-60
ρ^0) cell lines, but not in the other
ρ^0 and mtDNA mutant lines. The plasma membrane NADH
oxidase activity was found to be up-regulated in both HL-AV2 and HeLa
ρ^0 cell lines, but not significantly in the fibroblast
ρ^0 and G11778A lines.
