A Ral GAP Complex Links PI 3-kinase/Akt Signaling to RalA Activation in Insulin Action

Overview

Journal Mol Biol Cell

Specialties Cell Biology
Molecular Biology

Date 2010 Dec 15

PMID 21148297

Citations 53

Authors

Xiao-Wei Chen

Dara Leto

Tingting Xiong

Genggeng Yu

Alan Cheng

Stuart Decker

Alan R Saltiel

Affiliations

Soon will be listed here.

Abstract

Insulin stimulates glucose transport in muscle and adipose tissue by translocation of glucose transporter 4 (GLUT4) to the plasma membrane. We previously reported that activation of the small GTPase RalA downstream of PI 3-kinase plays a critical role in this process by mobilizing the exocyst complex for GLUT4 vesicle targeting in adipocytes. Here we report the identification and characterization of a Ral GAP complex (RGC) that mediates the activation of RalA downstream of the PI 3-kinase/Akt pathway. The complex is composed of an RGC1 regulatory subunit and an RGC2 catalytic subunit (previously identified as AS250) that directly stimulates the guanosine triphosphate hydrolysis of RalA. Knockdown of RGC proteins leads to increased RalA activity and glucose uptake in adipocytes. Insulin inhibits the GAP complex through Akt2-catalyzed phosphorylation of RGC2 in vitro and in vivo, while activated Akt relieves the inhibitory effect of RGC proteins on RalA activity. The RGC complex thus connects PI 3-kinase/Akt activity to the transport machineries responsible for GLUT4 translocation.

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