Insulin Granule Recruitment and Exocytosis Is Dependent on p110γ in Insulinoma and Human β-Cells

• DOI: 10.2337/db08-1371
• Publication Date: 2009-06-24T01:53:56Z
• Authors: Gary M. Pigeau; Jelena Kolic; Brandon J. Ball; Michael B. Hoppa; Ying W. Wang; Thomas Rückle; Minna Woo; Jocelyn E. Mannin...; Patrick E. MacDonald
• Keywords: Tensin

OBJECTIVE Phosphatidylinositol 3-OH kinase (PI3K) has a long-recognized role in β-cell mass regulation and gene transcription is implicated the modulation of insulin secretion. The nontyrosine receptor–activated PI3K isoforms largely unexplored. We therefore investigated G-protein–coupled PI3Kγ its catalytic subunit p110γ granule recruitment exocytosis. RESEARCH DESIGN AND METHODS expression was knocked down by small-interfering RNA, activity selectively inhibited with AS605240 (40 nmol/l). Exocytosis monitored islet perifusion, whole-cell capacitance, total internal reflection fluorescence microscopy, electron microscopy INS-1 human β-cells. Cortical F-actin examined cells islets mouse β-cells lacking phosphatase tensin homolog (PTEN). RESULTS Knockdown or inhibition markedly blunted depolarization-induced secretion exocytosis ablated exocytotic response to direct Ca2+ infusion. This resulted from reduced localization plasma membrane associated increased cortical F-actin. Inhibition had no effect on PTEN. Finally, could be rapidly reversed agents that promote actin depolymerization. CONCLUSIONS an important determinant secretory trafficking membrane, at least part through negative Thus, plays maintaining membrane-docked, readily releasable pool granules insulinoma