Hyperinsulinemic hypoglycemia subtype glucokinase V91L mutant induces necrosis in β-cells via ATP depletion

Abstract

Hyperinsulinemic hypoglycemia subtype glucokinase (GCK-HH) is caused by an activating mutation in glucokinase (GCK) and has been shown to increase β-cell death. However, the mechanism of β-cell death in GCK-HH remains poorly understood. Here, we expressed the GCK-HH V91L GCK mutant in INS-1 832/13 cells to determine the effect of the mutation on β-cell viability and the mechanisms of β-cell death. We showed that expression of the V91L GCK mutant in INS-1 832/13 cells resulted in a rapid glucose concentration-dependent loss of cell viability. At 11 mM D-glucose, INS-1 832/13 cells expressing V91L GCK showed increased cell permeability without significant increases in Annexin V staining or caspase 3/7 activation, indicating that these cells are primarily undergoing cell death via necrosis. Over-expression of SV40 large T antigen, which inhibits the p53 pathway, did not affect the V91L GCK-induced cell death. We also found that non-phosphorylatable L-glucose did not induce rapid cell death. Of note, glucose phosphorylation coincided with a 90% loss of intracellular ATP content. Thus, our data suggest that the GCK V91L mutant induces rapid necrosis in INS-1 cells through accelerated glucose phosphorylation, ATP depletion, and increased cell permeability. Keywords: Glucokinase, Hyperinsulinemic hypoglycemia subtype glucokinase, Beta-cell death, Hyperinsulinemic hypoglycemia, Necrosis