PAK1 limits the expression of the pro-apoptotic protein Bad in pancreatic islet β-cells

Human type 2 diabetes is associated with β-cell apoptosis, and human islets from diabetic donors are ∼80% deficient in PAK1 protein. Toward addressing linkage of PAK1 to β-cell survival, PAK1–siRNA targeted MIN6 pancreatic β-cells were found to exhibit increased caspase-3 cleavage, cytosolic cytochrome-C and the pro-apoptotic protein Bad. PAK1+/− heterozygous mouse islets recapitulated the upregulation of Bad protein expression, as did hyperglycemic treatment of human or mouse islets; Bad levels were exacerbated most in PAK1+/− islets subjected to hyperglycemic stress. These data implicate PAK1 in β-cell survival via quenching of Bad protein expression, and suggest PAK1 as potential molecular target to preserve β-cell mass.

▸ Bad expression in islets was increased by chronic exposure to hyperglycemic conditions. ▸ Depletion of PAK1 in the absence of glucose induced Bad expression. ▸ Bad expression increased most in PAK1+/− heterozygous islets subjected to hyperglycemia. ▸ PAK1 is required to protect against β-cell apoptosis under hyperglycemic conditions.