The Rab GTPase-activating protein AS160 integrates Akt, protein kinase C, and AMP-activated protein kinase signals regulating GLUT4 traffic

Diabetes. 2007 Feb;56(2):414-23. doi: 10.2337/db06-0900.

Abstract

Insulin-dependent phosphorylation of Akt target AS160 is required for GLUT4 translocation. Insulin and platelet-derived growth factor (PDGF) (Akt activators) or activation of conventional/novel (c/n) protein kinase C (PKC) and 5' AMP-activated protein kinase (AMPK) all promote a rise in membrane GLUT4 in skeletal muscle and cultured cells. However, the downstream effectors linking these pathways to GLUT4 traffic are unknown. Here we explore the hypothesis that AS160 is a molecular link among diverse signaling cascades converging on GLUT4 translocation. PDGF and insulin increased AS160 phosphorylation in CHO-IR cells. Stimuli that activate c/n PKC or AMPK also elevated AS160 phosphorylation. We therefore examined if these signaling pathways engage AS160 to regulate GLUT4 traffic in muscle cells. Nonphosphorylatable AS160 (4P-AS160) virtually abolished the net surface GLUT4myc gains elicited by insulin, PDGF, K(+) depolarization, or 5-aminoimidazole-4-carboxamide-1-beta-d-ribofuranoside but partly, yet significantly, inhibited the effects of 4-phorbol-12-myristate-13-acetate. However, the hypertonicity or 2,4-dinitrophenol-dependent gains in surface GLUT4myc were unaffected by 4P-AS160. RK-AS160 (GTPase-activating protein [GAP] inactive) or 4PRK-AS160 (GAP inactive, nonphosphorylatable) had no effect on surface GLUT4myc elicited by all stimuli. Collectively, these results indicate that activation of Akt, c/n PKC, or alpha2-AMPK intersect at AS160 to regulate GLUT4 traffic, as well as highlight the potential of AS160 as a therapy target to increase muscle glucose uptake.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • CHO Cells
  • Cricetinae
  • Cricetulus
  • GTPase-Activating Proteins / metabolism*
  • Glucose Transporter Type 4 / drug effects
  • Glucose Transporter Type 4 / metabolism*
  • Insulin / pharmacology
  • Muscle, Skeletal
  • Myoblasts / physiology
  • Phosphorylation / drug effects
  • Platelet-Derived Growth Factor / pharmacology
  • Protein Kinase C / drug effects
  • Protein Kinase C / metabolism*
  • Protein Transport
  • Proto-Oncogene Proteins c-akt / drug effects
  • Proto-Oncogene Proteins c-akt / metabolism*
  • Signal Transduction / drug effects
  • Signal Transduction / physiology*

Substances

  • GTPase-Activating Proteins
  • Glucose Transporter Type 4
  • Insulin
  • Platelet-Derived Growth Factor
  • Proto-Oncogene Proteins c-akt
  • Protein Kinase C