Intestinal Cell Kinase (ICK) Promotes Activation of mTOR Complex 1 (mTORC1) through Phosphorylation of Raptor Thr-908
| Autor: | Thurl E. Harris, Di Wu, Jeffrey Shabanowitz, Zheng Fu, Jessica R. Chapman, Donald F. Hunt, Lifu Wang |
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| Rok vydání: | 2012 |
| Předmět: |
Molecular Sequence Data
Cell Cycle Proteins mTORC1 Mechanistic Target of Rapamycin Complex 1 Protein Serine-Threonine Kinases Biochemistry Mice 3T3-L1 Cells Consensus Sequence Animals Humans Protein phosphorylation Amino Acid Sequence Phosphorylation Protein kinase A Molecular Biology PI3K/AKT/mTOR pathway Adaptor Proteins Signal Transducing Cell Proliferation Monomeric GTP-Binding Proteins biology Cell growth TOR Serine-Threonine Kinases Neuropeptides G1 Phase Proteins Ribosomal Protein S6 Kinases 70-kDa Regulatory-Associated Protein of mTOR Cell Biology Phosphoproteins Molecular biology Peptide Fragments HEK293 Cells Phosphothreonine Amino Acid Substitution Multiprotein Complexes Mutagenesis Site-Directed biology.protein Ras Homolog Enriched in Brain Protein Signal transduction Oligopeptides Signal Transduction Protein Binding RHEB |
| Zdroj: | Journal of Biological Chemistry. 287:12510-12519 |
| ISSN: | 0021-9258 |
| Popis: | Intestinal cell kinase (ICK), named after its cloning origin, the intestine, is actually a ubiquitously expressed and highly conserved serine/threonine protein kinase. Recently we reported that ICK supports cell proliferation and G(1) cell cycle progression. ICK deficiency significantly disrupted the mammalian target of rapamycin (mTOR) complex 1 (mTORC1) signaling events. However, the biological substrates that mediate the downstream signaling effects of ICK in proliferation and the molecular mechanisms by which ICK interacts with mTORC1 are not well defined. Our prior studies also provided biochemical evidence that ICK interacts with the mTOR/Raptor complex in cells and phosphorylates Raptor in vitro. In this report, we investigated whether and how ICK targets Raptor to regulate the activity of mTORC1. Using the ICK substrate consensus sequence [R-P-X-S/T-P/A/T/S], we identified a putative phosphorylation site, RPGT908T, for ICK in human Raptor. By mass spectrometry and a phospho-specific antibody, we showed that Raptor Thr-908 is a novel in vivo phosphorylation site. ICK is able to phosphorylate Raptor Thr-908 both in vitro and in vivo and when Raptor exists in protein complexes with or without mTOR. Although expression of the Raptor T908A mutant did not affect the mTORC1 integrity, it markedly impaired the mTORC1 activation by insulin or by overexpression of the small GTP-binding protein RheB under nutrient starvation. Our findings demonstrate an important role for ICK in modulating the activity of mTORC1 through phosphorylation of Raptor Thr-908 and thus implicate a potential signaling mechanism by which ICK regulates cell proliferation and division. |
| Databáze: | OpenAIRE |
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