Glyceraldehyde-3-Phosphate Dehydrogenase as a Sensor of Cellular Metabolic States

The chemical pathways by which redox perturbations and disulfide bonds contribute to cellular responses and respond to changes in nutrient availability have not been well explored and are implicated in a host of human diseases. To determine the role of these redox perturbations, HepG2 cells were treated with different compounds intended to induce oxidative stress, then subjected to PAO-affinity chromatography, which isolates proteins containing reducible disulfide bonds. Results indicated that the levels of GAPDH disulfides were highly dynamic relative to total protein disulfides and that they were responsive to changes in the nutrient availability in the cells, increasing when glucose was withdrawn. The disulfide formed in GAPDH under these conditions involved the catalytic cysteine, strongly suggesting that disulfide formation results in the inhibition of GAPDH. The dynamic character of the GAPDH disulfide bond, and its responsiveness to glucose withdrawal is of particular importance in the context of aerobic glycolysis, where GAPDH is a rate limiting step. These findings suggest that redox modifications of GAPDH may play an important role in regulating cellular responses to limited nutrients by potentially rerouting nutrients to the pentose phosphate pathway where they can help respond to oxidative stress