Involvement of protein kinase C-ε in inositol hexakisphosphate-induced exocytosis in mouse pancreatic β-cells

Abstract

Inositolhexakisphosphate (InsP6) plays a pivotal role in the pancreatic β-cell stimulus-secretion coupling. We have used capacitance measurements to study the effects of InsP6 on Ca 2+-dependent exocytosis in single mouse pancreatic β-cells. In the presence of inhibitors of the protein phosphatase calcineurin to block endocytosis, intracellular application of InsP6 produced a dose-dependent stimulation of exocytosis, and half-maximal effect was observed at 22 μM. The stimulatory effect of InsP6 was dependent on protein kinase C (PKC) activity. Antisense oligonucleotides directed against specific PKC isoforms (α, βII, δ, ε, ξ) revealed the involvement of PKC-ε in InsP6-induced exocytosis. Furthermore, expression of dominant negative PKC-ε abolished InsP6-evoked exocytosis, whereas expression of wild-type PKC-ε led to a significant stimulation of InsP6-induced exocytosis. These data demonstrate that PKC-ε is involved in InsP6-induced exocytosis in pancreatic βcells.