Regulation of K_ATP Channel Trafficking in Pancreatic β-Cells by Protein Histidine Phosphorylation.

Abstract

Protein histidine phosphatase 1 (PHPT-1) is an evolutionarily conserved 14-kDa protein that dephosphorylates phosphohistidine. <i>PHPT-1^-/-</i> mice were generated to gain insight into the role of PHPT-1 and histidine phosphorylation/dephosphorylation in mammalian biology. <i>PHPT-1^-/-</i> mice exhibited neonatal hyperinsulinemic hypoglycemia due to impaired trafficking of K_ATP channels to the plasma membrane in pancreatic β-cells in response to low glucose and leptin and resembled patients with congenital hyperinsulinism (CHI). The defect in K_ATP channel trafficking in PHPT-1^-/- β-cells was due to the failure of PHPT-1 to directly activate transient receptor potential channel 4 (TRPC4), resulting in decreased Ca²⁺ influx and impaired downstream activation of AMPK. Thus, these studies demonstrate a critical role for PHPT-1 in normal pancreatic β-cell function and raise the possibility that mutations in PHPT-1 and/or TRPC4 may account for yet to be defined cases of CHI.