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Akt-2 binds to Glut4-containing vesicles and phosphorylates their component proteins in response to insulin

T A Kupriyanova1, K V Kandror

  • 1Boston University School of Medicine, Boston, Massachusetts 02118, USA.

The Journal of Biological Chemistry
|January 9, 1999
PubMed

Insights

Insulin activates protein kinase activity in Glut4 vesicles, identified as Akt-2. This kinase phosphorylates vesicle proteins, including Glut4, and is recruited to vesicles by insulin signaling in rat adipocytes.

Area of Science:

  • Cell Biology
  • Molecular Signaling
  • Endocrinology

Background:

  • Glucose transporter 4 (Glut4) vesicles are crucial for insulin-stimulated glucose uptake in adipocytes.
  • The precise molecular mechanisms regulating Glut4 vesicle trafficking and function remain under investigation.

Purpose of the Study:

  • To identify the protein kinase activity associated with Glut4-containing vesicles.
  • To investigate the role of insulin in modulating this kinase activity and its substrates.
  • To determine the identity and localization of the vesicle-associated kinase.

Main Methods:

  • Immunoadsorption of Glut4-containing vesicles from primary rat adipocytes.
  • In vitro kinase assays and Western blot analysis.
  • MonoQ chromatography for protein purification and identification.
  • In vivo insulin administration and wortmannin treatment.

Main Results:

  • Glut4-containing vesicles exhibit endogenous protein kinase activity and contain phosphorylation substrates, including Glut4.
  • Insulin rapidly stimulates the phosphorylation of vesicle proteins.
  • Wortmannin inhibits insulin's effect on vesicle protein phosphorylation.
  • Vesicle-associated protein kinase activity was identified as Akt-2.
  • Akt-2 is recruited to Glut4-containing vesicles in response to insulin.

Conclusions:

  • Akt-2 is a key component of the signaling machinery regulating Glut4 vesicle function.
  • Insulin signaling directly impacts the kinase activity and localization of Akt-2 on Glut4 vesicles.
  • These findings elucidate a novel mechanism for insulin-mediated glucose transport regulation.

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