title: PRR5, a novel component of mTOR complex 2, regulates platelet-derived growth factor receptor beta expression and signaling.
abstract: The protein kinase mammalian target of rapamycin (mTOR) plays an important role in the coordinate regulation of cellular responses to nutritional and growth factor conditions. mTOR achieves these roles through interacting with raptor and rictor to form two distinct protein complexes, mTORC1 and mTORC2. Previous studies have been focused on mTORC1 to elucidate the central roles of the complex in mediating nutritional and growth factor signals to the protein synthesis machinery. Functions of mTORC2, relative to mTORC1, have remained little understood. Here we report identification of a novel component of mTORC2 named PRR5 (PRoline-Rich protein 5), a protein encoded by a gene located on a chromosomal region frequently deleted during breast and colorectal carcinogenesis (Johnstone, C. N., Castellvi-Bel, S., Chang, L. M., Sung, R. K., Bowser, M. J., Pique, J. M., Castells, A., and Rustgi, A. K. (2005) Genomics 85, 338-351). PRR5 interacts with rictor, but not raptor, and the interaction is independent of mTOR and not disturbed under conditions that disrupt the mTOR-rictor interaction. PRR5, unlike Sin1, another component of mTORC2, is not important for the mTOR-rictor interaction and mTOR activity toward Akt phosphorylation. Despite no significant effect of PRR5 on mTORC2-mediated Akt phosphorylation, PRR5 silencing inhibits Akt and S6K1 phosphorylation and reduces cell proliferation rates, a result consistent with PRR5 roles in cell growth and tumorigenesis. The inhibition of Akt and S6K1 phosphorylation by PRR5 knock down correlates with reduction in the expression level of platelet-derived growth factor receptor beta (PDGFRbeta). PRR5 silencing impairs PDGF-stimulated phosphorylation of S6K1 and Akt but moderately reduces epidermal growth factor- and insulin-stimulated phosphorylation. These findings propose a potential role of mTORC2 in the cross-talk with the cellular machinery that regulates PDGFRbeta expression and signaling.
authors.affiliation: Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota at the Twin Cities, Minneapolis, Minnesota 55455, USA.
authors.forename: So-Yon
authors.initials: SY
authors.lastname: Woo
authors.forename: Dong-Hwan
authors.initials: DH
authors.lastname: Kim
authors.forename: Chang-Bong
authors.initials: CB
authors.lastname: Jun
authors.forename: Young-Mi
authors.initials: YM
authors.lastname: Kim
authors.forename: Emilie Vander
authors.initials: EV
authors.lastname: Haar
authors.forename: Seong-il
authors.initials: SI
authors.lastname: Lee
authors.forename: James W
authors.initials: JW
authors.lastname: Hegg
authors.forename: Sricharan
authors.initials: S
authors.lastname: Bandhakavi
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Griffin
authors.forename: Do-Hyung
authors.initials: DH
authors.lastname: Kim
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D049109:Cell Proliferation / Q000187:drug effects; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism; D015179:Colorectal Neoplasms / Q000235:genetics / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D020868:Gene Silencing; D006367:HeLa Cells; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D000076222:Mechanistic Target of Rapamycin Complex 1; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D000076226:Rapamycin-Insensitive Companion of mTOR Protein; D020797:Receptor, Platelet-Derived Growth Factor beta / Q000096:biosynthesis* / Q000235:genetics; D000076223:Regulatory-Associated Protein of mTOR; D019893:Ribosomal Protein S6 Kinases / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D058570:TOR Serine-Threonine Kinases; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D007004:Hypoglycemic Agents; D007328:Insulin; D047908:Intracellular Signaling Peptides and Proteins; C493277:MAPKAP1 protein, human; D046912:Multiprotein Complexes; C523793:PRR5 protein, human; D011506:Proteins; C492571:RICTOR protein, human; C463659:RPTOR protein, human; D000076226:Rapamycin-Insensitive Companion of mTOR Protein; D000076223:Regulatory-Associated Protein of mTOR; D014157:Transcription Factors; D004815:Epidermal Growth Factor; D011494:Protein Kinases; C546842:MTOR protein, human; D020797:Receptor, Platelet-Derived Growth Factor beta; D000076222:Mechanistic Target of Rapamycin Complex 1; D051057:Proto-Oncogene Proteins c-akt; D019893:Ribosomal Protein S6 Kinases; D058570:TOR Serine-Threonine Kinases