Activation of protein kinase C (alpha, beta, and zeta) by insulin in 3T3/L1 cells. Transfection studies suggest a role for PKC-zeta in glucose transport

J Biol Chem. 1997 Jan 24;272(4):2551-8. doi: 10.1074/jbc.272.4.2551.

Abstract

We presently studied (a) insulin effects on protein kinase C (PKC) and (b) effects of transfection-induced, stable expression of PKC isoforms on glucose transport in 3T3/L1 cells. In both fibroblasts and adipocytes, insulin provoked increases in membrane PKC enzyme activity and membrane levels of PKC-alpha and PKC-beta. However, insulin-induced increases in PKC enzyme activity were apparent in both non-down-regulated adipocytes and adipocytes that were down-regulated by overnight treatment with 5 microM phorbol ester, which largely depletes PKC-alpha, PKC-beta, and PKC-epsilon, but not PKC-zeta. Moreover, insulin provoked increases in the enzyme activity of immunoprecipitable PKC-zeta. In transfection studies, stable overexpression of wild-type or constitutively active forms of PKC-alpha, PKC-beta1, and PKC-beta2 failed to influence basal or insulin-stimulated glucose transport (2-deoxyglucose uptake) in fibroblasts and adipocytes, despite inhibiting insulin effects on glycogen synthesis. In contrast, stable overexpression of wild-type PKC-zeta increased, and a dominant-negative mutant form of PKC-zeta decreased, basal and insulin-stimulated glucose transport in fibroblasts and adipocytes. These findings suggested that: (a) insulin activates PKC-zeta, as well as PKC-alpha and beta; and (b) PKC-zeta is required for, and may contribute to, insulin effects on glucose transport in 3T3/L1 cells.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 3T3 Cells
  • Animals
  • Cell Differentiation
  • Deoxyglucose / metabolism
  • Dose-Response Relationship, Drug
  • Enzyme Activation
  • Insulin / pharmacology*
  • Isoenzymes / metabolism*
  • Mice
  • Molecular Weight
  • Monosaccharide Transport Proteins / metabolism*
  • Protein Kinase C / metabolism*
  • Protein Kinase C beta
  • Protein Kinase C-alpha
  • Tetradecanoylphorbol Acetate / pharmacology
  • Transfection

Substances

  • Insulin
  • Isoenzymes
  • Monosaccharide Transport Proteins
  • Deoxyglucose
  • protein kinase C zeta
  • Prkca protein, mouse
  • Protein Kinase C
  • Protein Kinase C beta
  • Protein Kinase C-alpha
  • Tetradecanoylphorbol Acetate