title: RhoA modulates signaling through the mechanistic target of rapamycin complex 1 (mTORC1) in mammalian cells.
abstract: The mechanistic target of rapamycin (mTOR) in complex 1 (mTORC1) pathway integrates signals generated by hormones and nutrients to control cell growth and metabolism. The activation state of mTORC1 is regulated by a variety of GTPases including Rheb and Rags. Recently, Rho1, the yeast ortholog of RhoA, was shown to interact directly with TORC1 and repress its activation state in yeast. Thus, the purpose of the present study was to test the hypothesis that the RhoA GTPase modulates signaling through mTORC1 in mammalian cells. In support of this hypothesis, exogenous overexpression of either wild type or constitutively active (ca)RhoA repressed mTORC1 signaling as assessed by phosphorylation of p70S6K1 (Thr389), 4E-BP1 (Ser65) and ULK1 (Ser757). Additionally, RhoA·GTP repressed phosphorylation of mTORC1-associated mTOR (Ser2481). The RhoA·GTP mediated repression of mTORC1 signaling occurred independent of insulin or leucine induced stimulation. In contrast to the action of Rho1 in yeast, no evidence was found to support a direct interaction of RhoA·GTP with mTORC1. Instead, expression of caRheb, but not caRags, was able to rescue the RhoA·GTP mediated repression of mTORC1 suggesting RhoA functions upstream of Rheb to repress mTORC1 activity. Consistent with this suggestion, RhoA·GTP repressed phosphorylation of TSC2 (Ser939), PRAS40 (Thr246), Akt (Ser473), and mTORC2-associated mTOR (Ser2481). Overall, the results support a model in which RhoA·GTP represses mTORC1 signaling upstream of Akt and mTORC2.
authors: The Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, PO Box 850, Hershey, PA 17033, USA.
authors: Bradley S
authors: BS
authors: Gordon
authors: The Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, PO Box 850, Hershey, PA 17033, USA.
authors: Abid A
authors: AA
authors: Kazi
authors: The Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, PO Box 850, Hershey, PA 17033, USA.
authors: Catherine S
authors: CS
authors: Coleman
authors: The Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, PO Box 850, Hershey, PA 17033, USA.
authors: Michael D
authors: MD
authors: Dennis
authors: The Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, PO Box 850, Hershey, PA 17033, USA.
authors: Vincent
authors: V
authors: Chau
authors: The Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, PO Box 850, Hershey, PA 17033, USA.
authors: Leonard S
authors: LS
authors: Jefferson
authors: The Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, PO Box 850, Hershey, PA 17033, USA. Electronic address: skimball@psu.edu.
authors: Scot R
authors: SR
authors: Kimball
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry; D000818:Animals; D000071189:Autophagy-Related Protein-1 Homolog; D018797:Cell Cycle Proteins; D002460:Cell Line; D036386:Ephrin-A5 / Q000096:biosynthesis; D005347:Fibroblasts; D057809:HEK293 Cells; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry; D007930:Leucine / Q000494:pharmacology; D000076222:Mechanistic Target of Rapamycin Complex 1; D000076225:Mechanistic Target of Rapamycin Complex 2; D020559:Monomeric GTP-Binding Proteins / Q000096:biosynthesis / Q000378:metabolism; D046912:Multiprotein Complexes / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D009479:Neuropeptides / Q000096:biosynthesis / Q000378:metabolism; D010750:Phosphoproteins / Q000737:chemistry; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry; D051057:Proto-Oncogene Proteins c-akt / Q000737:chemistry; D000076205:Ras Homolog Enriched in Brain Protein; D051381:Rats; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000737:chemistry; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins / Q000737:chemistry; D020742:rhoA GTP-Binding Protein / Q000096:biosynthesis / Q000378:metabolism*
chemical_list: C484523:AKT1S1 protein, human; D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; C087000:EIF4EBP1 protein, human; D036386:Ephrin-A5; D007328:Insulin; D047908:Intracellular Signaling Peptides and Proteins; D046912:Multiprotein Complexes; D009479:Neuropeptides; D010750:Phosphoproteins; C490211:RHEB protein, human; D000076205:Ras Homolog Enriched in Brain Protein; C000624653:TSC2 protein, human; C000624655:Tsc2 protein, rat; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins; C066737:RHOA protein, human; D000071189:Autophagy-Related Protein-1 Homolog; D000076222:Mechanistic Target of Rapamycin Complex 1; D000076225:Mechanistic Target of Rapamycin Complex 2; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases; C484754:ULK1 protein, human; D020559:Monomeric GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein; D007930:Leucine
keywords: 4E-BP1; 70kDa ribosomal protein S6 kinase 1; Akt; PRAS40; RAPTOR; RAPTOR-independent companion of mTOR; RICTOR; Sin1; TSC; TSC2; ULK1; UTR; caRags; caRheb; caRhoA; constitutively active Rags B and C; constitutively active Rheb; constitutively active RhoA; eukaryotic initiation factor 4E binding protein 1; mTOR; mTORC; mTORC2; mechanistic target of rapamycin; mechanistic target of rapamycin complex; p70S6K1; proline-rich Akt/PKB substrate 40kDa; regulatory-associated protein of mTOR, complex 1; stress-activated map kinase-interacting protein 1; tuberous sclerosis complex; uncoordinated-51-like kinase 1; untranslated region; wild type RhoA; wtRhoA