Cdc42 is a Rho GTPase family member that can mediate insulin signaling to glucose transport in 3T3-L1 adipocytes.
We investigated the role of cdc42, a Rho GTPase family member, in insulin-induced glucose transport in 3T3-L1 adipocytes. Microinjection of anti-cdc42 antibody or cdc42 siRNA led to decreased insulin-induced and constitutively active G(q) (CA-G(q); Q209L)-induced GLUT4 translocation. Adenovirus-mediated expression of constitutively active cdc42 (CA-cdc42; V12) stimulated 2-deoxyglucose uptake to 56% of the maximal insulin response, and this was blocked by treatment with the phosphatidylinositol 3-kinase (PI3-kinase) inhibitor, wortmannin, or LY294002. Both insulin and CA-G(q) expression caused an increase in cdc42 activity, showing that cdc42 is activated by insulin and is downstream of G alpha(q/11) in this activation pathway. Immunoprecipitation experiments showed that insulin enhanced a direct association of cdc42 and p85, and both insulin treatment and CA-cdc42 expression stimulated PI3-kinase activity in immunoprecipitates with anti-cdc42 antibody. Furthermore, the effects of insulin, CA-G(q), and CA-cdc42 on GLUT4 translocation or 2-deoxyglucose uptake were inhibited by microinjection of anti-protein kinase C lambda (PKC lambda) antibody or overexpression of a kinase-deficient PKC lambda construct. In summary, activated cdc42 can mediate 1) insulin-stimulated GLUT4 translocation and 2) glucose transport in a PI3-kinase-dependent manner. 3) Insulin treatment and constitutively active G(q) expression can enhance the cdc42 activity state as well as the association of cdc42 with activated PI3-kinase. 4) PKC lambda inhibition blocks CA-cdc42, CA-G(q), and insulin-stimulated GLUT4 translocation. Taken together, these data indicate that cdc42 can mediate insulin signaling to GLUT4 translocation and lies downstream of G alpha(q/11) and upstream of PI3-kinase and PKC lambda in this stimulatory pathway.
Usui
Isao
I
Department of Medicine, Division of Endocrinology and Metabolism, University of California, San Diego, La Jolla 92093, USA.
Imamura
Takeshi
T
Huang
Jie
J
Satoh
Hiroaki
H
Olefsky
Jerrold M
JM
D016475:3T3 Cells; D017667:Adipocytes / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D015153:Blotting, Western; D002867:Chromones / Q000494:pharmacology; D003847:Deoxyglucose / Q000493:pharmacokinetics; D004305:Dose-Response Relationship, Drug; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D005947:Glucose / Q000378:metabolism*; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism; D007074:Immunoglobulin G / Q000378:metabolism; D007328:Insulin / Q000378:metabolism*; D007527:Isoenzymes; D051379:Mice; D008856:Microscopy, Fluorescence; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011233:Precipitin Tests; D011493:Protein Kinase C / Q000378:metabolism; D021381:Protein Transport; D015398:Signal Transduction; D013997:Time Factors; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism / Q000502:physiology*; D020741:rho GTP-Binding Proteins / Q000502:physiology*; D000099293:Protein Kinase C-lambda
D002867:Chromones; D003847:Deoxyglucose; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D005947:Glucose; D020962:Heterotrimeric GTP-Binding Proteins; D007074:Immunoglobulin G; D007328:Insulin; D007527:Isoenzymes; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D011493:Protein Kinase C; D020764:cdc42 GTP-Binding Protein; D020741:rho GTP-Binding Proteins; D000099293:Protein Kinase C-lambda; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one