NO-induced GAPDH aggregation is increased by GOSPEL protein and inhibited by NAD+

GONZALEZ, MARÍA C.; ROMERO, JORGE M.; INGARAMO, MARÍA C.; MUÑOZ SOSA, CHRISTIAN J.; CURTINO, JUAN A.; CARRIZO, MARÍA E.

Rio de Janeiro

Congreso; 5th Latin American Protein Society Meeting (LAPSM); 2016

Latin American Protein Society

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) catalyzes the reversible formation of 1,3-bisphosphoglycerate from glyceraldehyde-3-phosphate and inorganic phosphate with a concomitant reduction of NAD+ to NADH. A large body of evidence indicates that in addition to being involved in glycolysis, GAPDH has multiple functions in a variety of biochemical processes. The S-nitrosylation of GAPDH at the active site cysteine augments its binding to Siah1, an E3-ubiquitin-ligase whose nuclear localization signal mediates the nuclear translocation of the GAPDH-Siah1 complex. Inside the nucleus, GAPDH stabilizes Siah1 promoting the degradation of selected nuclear targets of Siah1 and finally apoptosis. A protective effect against apoptosis caused by the GAPDH-Siah1 complex nuclear translocation was described for a protein named GOSPEL (GAPDH?s competitor of Siah Protein Enhances Life). The S-nitrosylation of GOSPEL promotes its binding to S-nitrosylated GAPDH in competition with Siah1, retaining GOSPEL-bound GAPDH in the cytosol and preventing the cytotoxic effect. Under these conditions, GAPDH may also form amyloid-like aggregates proposed to be involved in cell death. No studies have been reported on the effect of GOSPEL in the latter event.In the present work, we describe the in vitro enhancement by GOSPEL of NO-induced GAPDH aggregation resulting in the formation GOSPEL-GAPDH co-aggregates with some amyloid-like properties. This would imply a potential new role for this protein in total contrast to the prevention of cell apoptosis elicited by nuclear translocation of Siah1-bound GAPDH. NAD+, the GAPDH coenzyme, inhibited both GAPDH aggregation and co-aggregation with GOSPEL. Our results suggest that even though NAD+ causes loss of GAPDH activity under oxidative stress conditions, it might nevertheless protect the enzyme from aggregation, an event that could lead to more damaging consequences than the loss of activity since the high GAPDH content in cells would assure sufficient active enzyme to sustain its metabolic function.