A Rictor-Myo1c complex participates in dynamic cortical actin events in 3T3-L1 adipocytes.
Insulin signaling through phosphatidylinositol 3-kinase (PI 3-kinase) activates the protein kinase Akt through phosphorylation of its threonine 308 and serine 473 residues by the PDK1 protein kinase and the Rictor-mammalian target of rapamycin complex (mTORC2), respectively. Remarkably, we show here that the Rictor protein is also present in cultured adipocytes in complexes containing Myo1c, a molecular motor that promotes cortical actin remodeling. Interestingly, the Rictor-Myo1c complex is biochemically distinct from the previously reported mTORC2 and can be immunoprecipitated independently of mTORC2. Furthermore, while RNA interference-directed silencing of Rictor results in the expected attenuation of Akt phosphorylation at serine 473, depletion of Myo1c is without effect. In contrast, loss of either Rictor or Myo1c inhibits phosphorylation of the actin filament regulatory protein paxillin at tyrosine 118. Furthermore, Myo1c-induced membrane ruffling of 3T3-L1 adipocytes is also compromised following Rictor knockdown. Interestingly, neither the mTORC2 inhibitor rapamycin nor the PI 3-kinase inhibitor wortmannin affects paxillin tyrosine 118 phosphorylation. Taken together, our findings suggest that the Rictor-Myo1c complex is distinct from mTORC2 and that Myo1c, in conjunction with Rictor, participates in cortical actin remodeling events.
Hagan
G Nana
GN
Program in Molecular Medicine, University of Massachusetts Medical School, 373 Plantation Street, Worcester, MA 01605, USA.
Lin
Yenshou
Y
Magnuson
Mark A
MA
Avruch
Joseph
J
Czech
Michael P
MP
D041721:3T3-L1 Cells; D000199:Actins / Q000378:metabolism*; D017667:Adipocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D021961:Cell Membrane Structures / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D006801:Humans; D047468:Immunoprecipitation; D007328:Insulin / Q000494:pharmacology; D051379:Mice; D024461:Myosin Type I; D009218:Myosins / Q000737:chemistry / Q000378:metabolism*; D051419:Paxillin / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D019000:Phosphotyrosine / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D011494:Protein Kinases / Q000378:metabolism; D017434:Protein Structure, Tertiary; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D000076226:Rapamycin-Insensitive Companion of mTOR Protein; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases
D000199:Actins; D002352:Carrier Proteins; D007328:Insulin; D024461:Myosin Type I; D009218:Myosins; D051419:Paxillin; D019869:Phosphatidylinositol 3-Kinases; D019000:Phosphotyrosine; D011494:Protein Kinases; D051057:Proto-Oncogene Proteins c-akt; D000076226:Rapamycin-Insensitive Companion of mTOR Protein; D020123:Sirolimus; D058570:TOR Serine-Threonine Kinases; C470422:Myo1c protein, mouse; C525637:rictor protein, mouse; C546842:MTOR protein, human; C546843:mTOR protein, mouse