Abstract
mTOR/RAFT1/FRAP is the target of the immunosuppressive drug rapamycin and the central component of a nutrient- and hormone-sensitive signaling pathway that regulates cell growth. We report that mTOR forms a stoichiometric complex with raptor, an evolutionarily conserved protein with at least two roles in the mTOR pathway. Raptor has a positive role in nutrient-stimulated signaling to the downstream effector S6K1, maintenance of cell size, and mTOR protein expression. The association of raptor with mTOR also negatively regulates the mTOR kinase activity. Conditions that repress the pathway, such as nutrient deprivation and mitochondrial uncoupling, stabilize the mTOR-raptor association and inhibit mTOR kinase activity. We propose that raptor is a missing component of the mTOR pathway that through its association with mTOR regulates cell size in response to nutrient levels.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adaptor Proteins, Signal Transducing
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Amino Acid Sequence
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Binding Sites
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Carrier Proteins / metabolism
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Cell Cycle Proteins
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Cell Division
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Cell Line, Transformed
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Cell Size
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Conserved Sequence
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Culture Media
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Evolution, Molecular
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Humans
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Molecular Sequence Data
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Phosphoproteins / metabolism
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Protein Kinases / metabolism*
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Protein Structure, Tertiary
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Proteins / genetics
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Proteins / metabolism*
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Regulatory-Associated Protein of mTOR
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Repetitive Sequences, Amino Acid
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Ribosomal Protein S6 Kinases / metabolism
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Signal Transduction*
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Sirolimus / pharmacology
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TOR Serine-Threonine Kinases
Substances
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Adaptor Proteins, Signal Transducing
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Carrier Proteins
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Cell Cycle Proteins
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Culture Media
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EIF4EBP1 protein, human
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Phosphoproteins
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Proteins
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RPTOR protein, human
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Regulatory-Associated Protein of mTOR
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Protein Kinases
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MTOR protein, human
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Ribosomal Protein S6 Kinases
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TOR Serine-Threonine Kinases
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Sirolimus