RESUMEN

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.

Asunto(s)

Proteínas Portadoras/metabolismo , Proliferación Celular , Regulación de la Expresión Génica/fisiología , Complejos Multiproteicos/metabolismo , Proteínas Quinasas/metabolismo , Receptor beta de Factor de Crecimiento Derivado de Plaquetas/biosíntesis , Transducción de Señal/fisiología , Proteínas Adaptadoras Transductoras de Señales/genética , Proteínas Adaptadoras Transductoras de Señales/metabolismo , Neoplasias de la Mama/genética , Neoplasias de la Mama/metabolismo , Proteínas Portadoras/genética , Proliferación Celular/efectos de los fármacos , Transformación Celular Neoplásica/genética , Transformación Celular Neoplásica/metabolismo , Neoplasias Colorrectales/genética , Neoplasias Colorrectales/metabolismo , Factor de Crecimiento Epidérmico/farmacología , Regulación de la Expresión Génica/efectos de los fármacos , Silenciador del Gen , Células HeLa , Humanos , Hipoglucemiantes/farmacología , Insulina/farmacología , Péptidos y Proteínas de Señalización Intracelular , Diana Mecanicista del Complejo 1 de la Rapamicina , Complejos Multiproteicos/genética , Fosforilación , Proteínas Quinasas/genética , Proteínas/genética , Proteínas/metabolismo , Proteínas Proto-Oncogénicas c-akt/genética , Proteínas Proto-Oncogénicas c-akt/metabolismo , Proteína Asociada al mTOR Insensible a la Rapamicina , Receptor beta de Factor de Crecimiento Derivado de Plaquetas/genética , Proteína Reguladora Asociada a mTOR , Proteínas Quinasas S6 Ribosómicas/genética , Proteínas Quinasas S6 Ribosómicas/metabolismo , Eliminación de Secuencia , Transducción de Señal/efectos de los fármacos , Serina-Treonina Quinasas TOR , Factores de Transcripción/genética , Factores de Transcripción/metabolismo