GAPDH oligomerization as a switch for its functions

224/250 words) Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), an important glycolytic enzyme, has a non-catalytic (thus a non-canonical) role in inducing mitochondrial elimination under oxidative stress. We recently demonstrated that phosphorylation of GAPDH by delta protein kinase C (δPKC) inhibits this GAPDH-dependent mitochondrial elimination. PKC phosphorylation of GAPDH correlates with increased cell injury following oxidative stress, suggesting that inhibiting GAPDH phosphorylation should decrease cell injury. Using rational design, we identified pseudoGAPDH (ψGAPDH) peptide, an inhibitor of δPKC-mediated GAPDH phosphorylation that does not inhibit the phosphorylation of other PKC substrates. Unexpectedly, ψGAPDH decreased mitochondrial elimination and increased cardiac damage in an animal model of heart attack. Either treatment with ψGAPDH or direct phosphorylation of GAPDH by PKC decreased GAPDH tetramerization, which corresponded to reduced GAPDH glycolytic activity in vitro and ex vivo. Taken together, our study identified the potential mechanism by which oxidative stress inhibits the protective GAPDH-mediated elimination of damaged mitochondria. Our study also identified a pharmacological tool, ψGAPDH peptide, with interesting properties. ψGAPDH peptide is an inhibitor of the interaction between δPKC and GAPDH, and of the resulting phosphorylation of GAPDH by δPKC. ψGAPDH peptide is also an inhibitor of GAPDH oligomerization and thus an inhibitor of GAPDH glycolytic activity. Finally, we found that ψGAPDH peptide is an inhibitor of the elimination of damaged mitochondria. We discuss how this unique property of increasing cell damage following oxidative stress suggests a potential use for ψGAPDH peptide-based therapy. by gest on Sptem er 1, 2017 hp://w w w .jb.org/ D ow nladed from GAPDH oligomerization as a switch for its functions