Calmodulin antagonists inhibit insulin-stimulated GLUT4 (glucose transporter 4) translocation by preventing the formation of phosphatidylinositol 3,4,5-trisphosphate in 3T3L1 adipocytes

Mol Endocrinol. 2000 Feb;14(2):317-26. doi: 10.1210/mend.14.2.0425.

Abstract

It has been previously reported that calmodulin plays a regulatory role in the insulin stimulation of glucose transport. To examine the basis for this observation, we examined the effect of a panel of calmodulin antagonists that demonstrated a specific inhibition of insulin-stimulated glucose transporter 4 (GLUT4) but not insulin- or platelet-derived growth factor (PDGF)-stimulated GLUT1 translocation in 3T3L1 adipocytes. These treatments had no effect on insulin receptor autophosphorylation or tyrosine phosphorylation of insulin receptor substrate 1 (IRS1). Furthermore, IRS1 or phosphotyrosine antibody immunoprecipitation of phosphatidylinositol (PI) 3-kinase activity was not affected. Despite the marked insulin and PDGF stimulation of PI 3-kinase activity, there was a near complete inhibition of protein kinase B activation. Using a fusion protein of the Grp1 pleckstrin homology (PH) domain with the enhanced green fluorescent protein, we found that the calmodulin antagonists prevented the insulin stimulation of phosphatidylinositol 3,4,5-trisphosphate [PI(3,4,5)P3] formation in vivo. Similarly, although PDGF stimulation increased PI 3-kinase activity in in vitro immunoprecipitation assays, there was also no significant formation of PI(3,4,5)P3 in vivo. These data demonstrate that calmodulin antagonists prevent insulin-stimulated GLUT4 translocation by inhibiting the in vivo production of PI(3,4,5)P3 without directly affecting IRS1- or phosphotyrosine-associated PI 3-kinase activity. This phenomenon is similar to that observed for the PDGF stimulation of 3T3L1 adipocytes.

Publication types

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

MeSH terms

  • 3T3 Cells / drug effects
  • 3T3 Cells / metabolism
  • Adipocytes / drug effects
  • Adipocytes / metabolism
  • Animals
  • Calmodulin / antagonists & inhibitors*
  • Glucose Transporter Type 1
  • Glucose Transporter Type 4
  • Insulin / metabolism*
  • Insulin / pharmacology
  • Insulin Receptor Substrate Proteins
  • Mice
  • Monosaccharide Transport Proteins / drug effects
  • Monosaccharide Transport Proteins / metabolism*
  • Muscle Proteins*
  • Phosphatidylinositol 3-Kinases / drug effects
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphatidylinositol Phosphates / metabolism*
  • Phosphoproteins / metabolism
  • Phosphorylation
  • Precipitin Tests
  • Protein-Serine-Threonine Kinases*
  • Proto-Oncogene Proteins / drug effects
  • Proto-Oncogene Proteins / metabolism
  • Proto-Oncogene Proteins c-akt
  • Sulfonamides / pharmacology
  • Trifluoperazine / pharmacology

Substances

  • Calmodulin
  • Glucose Transporter Type 1
  • Glucose Transporter Type 4
  • Insulin
  • Insulin Receptor Substrate Proteins
  • Irs1 protein, mouse
  • Monosaccharide Transport Proteins
  • Muscle Proteins
  • Phosphatidylinositol Phosphates
  • Phosphoproteins
  • Proto-Oncogene Proteins
  • Slc2a1 protein, mouse
  • Slc2a4 protein, mouse
  • Sulfonamides
  • phosphatidylinositol 3,4,5-triphosphate
  • Trifluoperazine
  • W 7
  • N-(6-aminohexyl)-1-naphthalenesulfonamide
  • N-(4-aminobutyl)-5-chloro-2-naphthalenesulfonamide
  • Phosphatidylinositol 3-Kinases
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt