Abstract 19262: Hexokinase-2-Mediated Protection Against Cell Death is Dependent Upon Voltage-Dependent Anion Channels 2&3
It is well known that tumor cells, which by definition do not die easily, have high rates of glycolysis. Hexokinase (HK), the first enzyme in glycolysis, is often overexpressed in these tumor cells, and is thought to be driving these high glycolytic rates. As HK is localized partly to the outer mitochondrial membrane (OMM), it has been proposed that HK may also be playing a role in these tumor cells’ resistance to death. Cardiomyocytes and murine embryonic fibroblasts (MEFs) express both HK1 and HK2 isoforms, both of which are capable of localizing to the OMM mainly through interaction with Voltage-Dependent Anion Channels (VDACs). Therefore, the purpose of this study was to assess whether overexpression of HK1 or HK2 could protect cultured cardiomyocytes or MEFs against H2O2-induced cell death. Additionally, HK2-mediated protection was also investigated in MEFs with genetic deletion of VDAC1 or VDAC3, or WT MEFs treated with a VDAC2 siRNA to significantly reduce VDAC2 protein levels. HK1 or HK2 protein expression and enzymatic activity was increased 2-3 fold by infection of cells with HK1 or HK2-encoding adenovirus. Control cells were infected with adenovirus encoding Β-Galactosidase. Cell death was induced by 50 μM H2O2 in cultured neonatal rat cardiomyocytes (NRCM), or by 500 μM H2O2 in MEFs. Overexpression of HK1 or HK2 reduced H2O2-induced death by ∼50% in both NRCMs and WT MEFs. Interestingly, overexpression of HK2 also protects MEFs devoid of VDAC1 by ∼50%. However, in MEFs with reduced VDAC2 expression or MEFs with deletion of VDAC3, HK2-mediated protection against H2O2-induced death is completely lost. Thus, it appears that the minor VDAC isoforms 2 & 3 are essential, while the main VDAC1 isoform is dispensable for HK2-mediated protection against cell death.
- © 2012 by American Heart Association, Inc.