A Rab10:RalA G protein cascade regulates insulin-stimulated glucose uptake in adipocytes.
Bottom Line: Once activated, Rab10 can increase the GTP binding of RalA by recruiting the Ral guanyl nucleotide exchange factor, Rlf/Rgl2.Overexpression of membrane-tethered Rlf compensates for the loss of Rab10 in Glut4 translocation, suggesting that Rab10 recruits Rlf to membrane compartments for RalA activation and that RalA is downstream of Rab10.Together these studies identify a new G protein cascade in the regulation of insulin-stimulated Glut4 trafficking and glucose uptake.
Affiliation: Life Sciences Institute, University of Michigan Medical School, Ann Arbor, MI 48109.Show MeSH
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Mentions: Because Rlf is required for Rab10-stimulated activation of RalA, we tested whether Rlf might be a direct effector for Rab10. Immunoprecipitation of HA-Rlf from Cos-1 cells overexpressing Myc-Rab10 (WT or QL) revealed that Rab10 specifically binds to Rlf, and further that this binding depends on the activation state of Rab10 (Figure 4A). Constitutively active Rab10 (QL) was twofold more effective in binding to Rlf than with the wild-type G protein (Figure 4C). Rlf binding to Rab10 (QL) was comparable to that observed with Rim1-RBD, a known effector of Rab10 (Figure 4, B and 4C). In addition, reciprocal immunoprecipitation of Myc-Rab10 also showed specific binding of Rlf to active Rab10 (QL) (Supplemental Figure S3).
Affiliation: Life Sciences Institute, University of Michigan Medical School, Ann Arbor, MI 48109.