Effects of severe hypoxia and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) knock-down on its gene expression, activity, subcellular localization, and apoptosis in gills of the shrimp Penaeus vannamei

Penaeus vannamei, experiences hypoxia in its natural habitat and in aquaculture. Under hypoxia, cells enhance anaerobic energy production through glycolysis dependent on the up-regulation of glycolytic enzymes including glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in gills. In vertebrates, GAPDH translocates into the nucleus and displays "moonlighting" functions including apoptosis. These alternative localizations and functions have not been described in crustaceans. We examined the effect of severe hypoxia and GAPDH silencing by RNA interference (RNAi) on its mRNA expression localization and glycolytic activity in P. vannamei gills. Expression and cytosolic activity were up-regulated only in hypoxia-exposed shrimp, but not in hypoxia-silenced specimens. GAPDH was immunodetected in cytosol and nucleus regardless of oxygen conditions. Hypoxia and RNAi decreased activity in cytosol and nucleus without affecting protein abundance, which suggests that nuclear GAPDH may have non-glycolytic functions. Moreover, Caspase-3 (Casp-3) expression increased with GAPDH silencing, suggesting alternative roles for GAPDH in apoptosis evasion.