Overexpression of wild-type Akt1 promoted insulin-stimulated p70S6 kinase (p70S6K) activity and affected GSK3 beta regulation, but did not promote insulin-stimulated GLUT4 translocation or glucose transport in L6 myotubes

J Med Invest. 2000 Feb;47(1-2):47-55.

Abstract

We have developed a simple, direct and sensitive method to detect GLUT4 on the cell surface. Using this system, we found that PI3-kinase plays a key role in the signaling pathway of insulin-stimulated GLUT4 translocation. One of the down stream effectors of PI3-kinase is serine-threonine kinase Akt (protein kinase B, RAK-PK), but the involvement of Akt in insulin-stimulated GLUT4 translocation is controversial. To investigate whether Akt1 regulates insulin-stimulated GLUT4 translocation and glucose uptake in L6 myotubes, we established L6 myotubes stably expressing c-myc epitope-tagged GLUT4 (GLUT4myc) and mouse wild type (WT) Akt1. We found that overexpression of WT Akt1 promoted insulin-stimulated p70S6 kinase (p70S6K) activity and increased the basal activity of GSK3 beta, but did not promote insulin-stimulated GLUT4 translocation or glucose uptake. These data supported the result that Akt is not a main signaling molecule to transmit the signal of insulin-stimulated GLUT4 translocation or glucose uptake from insulin-activated PI3-kinase.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Biological Transport
  • Calcium-Calmodulin-Dependent Protein Kinases / metabolism*
  • Cell Line
  • Glucose / metabolism*
  • Glucose Transporter Type 4
  • Glycogen Synthase Kinase 3
  • Insulin / metabolism*
  • Insulin / pharmacology
  • Mice
  • Molecular Sequence Data
  • Monosaccharide Transport Proteins / genetics
  • Monosaccharide Transport Proteins / metabolism*
  • Muscle Proteins*
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • Proto-Oncogene Proteins c-akt
  • Proto-Oncogene Proteins*
  • Rats
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Ribosomal Protein S6 Kinases / metabolism*

Substances

  • Glucose Transporter Type 4
  • Insulin
  • Monosaccharide Transport Proteins
  • Muscle Proteins
  • Proto-Oncogene Proteins
  • Recombinant Fusion Proteins
  • Slc2a4 protein, mouse
  • Slc2a4 protein, rat
  • Akt1 protein, rat
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • Ribosomal Protein S6 Kinases
  • Calcium-Calmodulin-Dependent Protein Kinases
  • Glycogen Synthase Kinase 3
  • Glucose