ATM protein kinase mediates full activation of Akt and regulates glucose transporter 4 translocation by insulin in muscle cells

Cell Signal. 2008 Aug;20(8):1555-63. doi: 10.1016/j.cellsig.2008.04.011. Epub 2008 Apr 26.

Abstract

Ataxia-telangiectasia (A-T) is an autosomal recessive disorder characterized by cerebellar ataxia and oculocutaneous telangiectasias. Patients with A-T also have high incidences of type 2 diabetes mellitus. The gene mutated in this disease, ATM (A-T, mutated), encodes a protein kinase. Previous studies have demonstrated that cytoplasmic ATM is an insulin-responsive protein and a major upstream activator of Akt following insulin treatment. To further investigate the function of ATM in insulin signal transduction, insulin resistance was induced in rats by feeding them a high-fat diet. Muscle tissue of rats with insulin resistance had both dramatically reduced ATM levels and substantially decreased Akt phosphorylation at Ser473 in comparison to that of regular chow-fed controls. The decreased ATM expression suggests that ATM is involved in the development of insulin resistance through down-regulation of Akt activity. The role of ATM in activation of Akt was further confirmed in mouse embryonic fibroblast (MEF) A29 (ATM+/+) and A38 (ATM-/-) cells. In addition, insulin-mediated Akt phosphorylation in mouse L6 muscle cells was greatly reduced by KU-55933, a specific inhibitor of ATM. A 2-deoxyglucose incorporation assay showed that this inhibitor also caused a significant reduction in insulin-mediated glucose uptake in L6 cells. An immunofluorescence experiment demonstrated that in L6 cells transfected with wild-type (WT) ATM, insulin caused a dramatic increase of the cell surface glucose transporter 4 (GLUT4), while in cells transfected with kinase-dead (KD) ATM, translocation of GLUT4 to the cell surface in response to insulin was markedly inhibited.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Ataxia Telangiectasia Mutated Proteins
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism*
  • Cell Line
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Enzyme Activation
  • Glucose Transporter Type 4 / metabolism*
  • Insulin / pharmacology*
  • Insulin Resistance*
  • Male
  • Mice
  • Muscle, Skeletal / enzymology*
  • Protein Transport
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • Proto-Oncogene Proteins c-akt / metabolism*
  • Rats
  • Rats, Wistar
  • Tumor Suppressor Proteins / genetics
  • Tumor Suppressor Proteins / metabolism*

Substances

  • Cell Cycle Proteins
  • DNA-Binding Proteins
  • Glucose Transporter Type 4
  • Insulin
  • Tumor Suppressor Proteins
  • Ataxia Telangiectasia Mutated Proteins
  • Atm protein, mouse
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt