Dynamics of glucose-induced membrane recruitment of protein kinase C beta II in living pancreatic islet beta-cells

J Biol Chem. 2002 Oct 4;277(40):37702-10. doi: 10.1074/jbc.M204478200. Epub 2002 Jul 30.

Abstract

The mechanisms by which glucose may affect protein kinase C (PKC) activity in the pancreatic islet beta-cell are presently unclear. By developing adenovirally expressed chimeras encoding fusion proteins between green fluorescent protein and conventional (betaII), novel (delta), or atypical (zeta) PKCs, we show that glucose selectively alters the subcellular localization of these enzymes dynamically in primary islet and MIN6 beta-cells. Examined by laser scanning confocal or total internal reflection fluorescence microscopy, elevated glucose concentrations induced oscillatory translocations of PKCbetaII to spatially confined regions of the plasma membrane. Suggesting that increases in free cytosolic Ca(2+) concentrations ([Ca(2+)](c)) were primarily responsible, prevention of [Ca(2+)](c) increases with EGTA or diazoxide completely eliminated membrane recruitment, whereas elevation of cytosolic [Ca(2+)](c) with KCl or tolbutamide was highly effective in redistributing PKCbetaII both to the plasma membrane and to the surface of dense core secretory vesicles. By contrast, the distribution of PKCdelta.EGFP, which binds diacylglycerol but not Ca(2+), was unaffected by glucose. Measurement of [Ca(2+)](c) immediately beneath the plasma membrane with a ratiometric "pericam," fused to synaptic vesicle-associated protein-25, revealed that depolarization induced significantly larger increases in [Ca(2+)](c) in this domain. These data demonstrate that nutrient stimulation of beta-cells causes spatially and temporally complex changes in the subcellular localization of PKCbetaII, possibly resulting from the generation of Ca(2+) microdomains. Localized changes in PKCbetaII activity may thus have a role in the spatial control of insulin exocytosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • Cell Membrane / enzymology
  • Cell Membrane / physiology
  • Clone Cells
  • Cytosol / enzymology
  • Diazoxide / pharmacology
  • Egtazic Acid / pharmacology
  • Glucose / pharmacology*
  • Green Fluorescent Proteins
  • Islets of Langerhans / drug effects
  • Islets of Langerhans / enzymology
  • Islets of Langerhans / physiology*
  • Isoenzymes / metabolism*
  • Kinetics
  • Luminescent Proteins / metabolism
  • Membrane Potentials / drug effects
  • Membrane Potentials / physiology
  • Mice
  • Potassium / pharmacology
  • Protein Kinase C / metabolism*
  • Protein Kinase C beta
  • Protein Transport
  • Recombinant Fusion Proteins / metabolism

Substances

  • Isoenzymes
  • Luminescent Proteins
  • Recombinant Fusion Proteins
  • Green Fluorescent Proteins
  • Egtazic Acid
  • Protein Kinase C
  • Protein Kinase C beta
  • Glucose
  • Diazoxide
  • Potassium