VEGF up-regulation by G93A superoxide dismutase and the role of malate–aspartate shuttle inhibition

A gain of interaction of the amyotrophic lateral sclerosis (ALS)-linked G93A-superoxide dismutase-1 (G93A-hSOD1) with cytosolic malate dehydrogenase (cytMDH), a key enzyme in the malate–aspartate shuttle, diverts neurons towards anaerobic metabolism. Changes in vascular endothelial growth factor (VEGF) are reported in ALS and hypoxia. Here we report that expression of G93A-hSOD1 fused with green fluorescent protein in NSC-34 cells enhanced VEGF expression and levels of VEGF and its upstream regulator hypoxia-inducible factor (HIF-1α). G93A-hSOD1 expressing cells were unable to further up-regulated VEGF in response to Co2+ and H2O2. Amino-oxyacetate that inhibits the malate–aspartate shuttle caused a similar increase in VEGF mRNA and impaired response to H2O2 in WT-hSOD1 expressing cells. Interruption of the G93A-hSOD1/cytMDH interaction reduced VEGF expression in G93A-hSOD1 expressing cells and restored their ability to up-regulate VEGF in response to Co2+ and H2O2. These results demonstrate that the ALS-linked G93A hSOD1 mutation impairs VEGF regulation compatible with the inhibition of neuronal malate–aspartate shuttle.