A role for 14-3-3 in insulin-stimulated GLUT4 translocation through its interaction with the RabGAP AS160.
Translocation of the insulin-regulated glucose transporter GLUT4 to the cell surface is dependent on the phosphatidylinositol 3-kinase/Akt pathway. The RabGAP (Rab GTPase-activating protein) AS160 (Akt substrate of 160 kDa) is a direct substrate of Akt and plays an essential role in the regulation of GLUT4 trafficking. We have used liquid chromatography tandem mass spectrometry to identify several 14-3-3 isoforms as AS160-interacting proteins. 14-3-3 proteins interact with AS160 in an insulin- and Akt-dependent manner via an Akt phosphorylation site, Thr-642. This correlates with the dominant negative effect of both the AS160(T642A) and the AS160(4P) mutants on insulin-stimulated GLUT4 translocation. Introduction of a constitutive 14-3-3 binding site into AS160(4P) restored 14-3-3 binding without disrupting AS160-IRAP (insulin-responsive amino peptidase) interaction and reversed the inhibitory effect of AS160(4P) on GLUT4 translocation. These data show that the insulin-dependent association of 14-3-3 with AS160 plays an important role in GLUT4 trafficking in adipocytes.
Ramm
Georg
G
Diabetes and Obesity Program, Garvan Institute of Medical Research, Sydney, NSW, Australia. g.ramm@garvan.org.au
Larance
Mark
M
Guilhaus
Michael
M
James
David E
DE
D048948:14-3-3 Proteins / Q000737:chemistry*; D041721:3T3-L1 Cells; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D020690:GTPase-Activating Proteins / Q000378:metabolism / Q000502:physiology*; D005947:Glucose / Q000378:metabolism; D051275:Glucose Transporter Type 4 / Q000378:metabolism / Q000502:physiology*; D007328:Insulin / Q000378:metabolism; D051379:Mice; D011494:Protein Kinases / Q000378:metabolism; D021381:Protein Transport; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000378:metabolism*
D048948:14-3-3 Proteins; D020690:GTPase-Activating Proteins; D051275:Glucose Transporter Type 4; D007328:Insulin; C505647:Tbc1d4 protein, mouse; D011494:Protein Kinases; D051057:Proto-Oncogene Proteins c-akt; D020691:rab GTP-Binding Proteins; D005947:Glucose