Abstract 3948: Glucose-6-phosphate Induces Spontaneous Swelling in Isolated Mitochondria via Hexokinase II Dissociation From Mitochondria
Glucose-6-phosphate (G6P) is a glycolytic intermediate that is significantly elevated during cardiac ischemia, and its accumulation is markedly attenuated by ischemic preconditioning. In this study, we provide evidence that G6P induces rapid dissociation of hexokinase II (HXK II) from mitochondria and induces spontaneous mitochondrial swelling. Fresh mitochondria were isolated from rat heart and used immediately. G6P potently increased mitochondrial swelling in a dose-dependent manner (0 –20 mM) monitored by absorbance at 540 nm (Fig A⇓). G6P also partially dissipated mitochondrial membrane potential. Following moderate calcium loading (3×20μM or 1×60μM), G6P directly induced calcium release from mitochondria (Fig B⇓). These effects were significantly attenuated by 0.2 μM cyclosporine A. However, partial inhibition of the voltage dependent anion channel (VDAC) by G3139, a novel nucleotide inhibitor, did not significantly alter the G6P effect. Western blot showed that the G6P effect was correlated strictly with HXK II associated with the mitochondria; its analogues such as 2-deoxyglucose and 2-deoxyglucose 6-phosphate did not dissociate HXK II from mitochondria and did not promote mitochondrial swelling, suggesting that HXK II dissociation from the mitochondrial is critical for this effect. Moreover, G6P-treated mitochondria showed no change of adenine nucleotide transport through VDAC. The data suggest a novel effect of HXK II dissociation on mitochondrial function.