The cells in our body have several mechanisms to counteract oxidative stress by producing antioxidants. One of the natural sources of antioxidants occurs through the activity of an enzyme known as glucose-6-phosphate dehydrogenase (G6PD). G6PD catalyzes the first and rate-limiting step of the pentose phosphate pathway, in which reduced NADPH (nicotinamide adenine dinucleotide phosphate) is generated. NADPH is in turn used to maintain the supply of reduced glutathione (GSH), which plays a critical role in regulating antioxidant balance and thus protecting cells from oxidative damage. Particularly, erythrocytes, which lack mitochondria, have no other means of generating NADPH and rely solely on G6PD for the generation of antioxidants. G6PD deficiency, caused by a loss of enzymatic activity and structural integrity due to a variety of different point mutations of G6PD, disrupts the physiological antioxidant balance with significant decreases in NADPH and GSH levels and thus increases the vulnerability to oxidative stress in cells. Lacking protection against oxidative stress, G6PD-deficient individuals are highly susceptible to hemolytic anemia, neonatal jaundice, and kernicterus (bilirubin-induced brain damage), it left untreated. Currently there are no treatments available for G6PD deficiency. Given that G6PD deficiency can lead to such devastating diseases, there is a pressing need to develop a therapeutic plan that will correct G6PD deficiency. Towards this end, we first characterized one of the most common G6PD mutant enzymes, Canton G6PD, by X-ray crystallography. We identified the structurally distorted areas in the enzyme leading to the decreased enzyme activity. Using this enzyme, we screened over 100,000 molecules for activators (chaperones) and identified a potential molecule (referred to as AG1 hereafter) that activated the enzyme by at least 2-fold and significantly increased the enzyme’s stability in cells. AG1 activated other common G6PD mutant enzymes as well, suggesting that it can be a general treatment for G6PD deficiency. Furthermore, AG1 alleviated loss-of-function phenotypes in a G6PD-deficient (Canton G6PD overexpressing) zebrafish model. Taken together, our study provides novel insights into developing a therapeutic strategy to G6PD deficiency that prevents or reduces G6PD deficiency-associated pathologies that affect 7-8% of world population.

Generation of allosteric chaperones for Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency

253rd National Meeting (2017)

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