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J. Biol. Chem., Vol. 282, Issue 32, 23708-23715, August 10, 2007

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P-Rex1 Links Mammalian Target of Rapamycin Signaling to Rac Activation and Cell Migration^*

Ivette Hernández-Negrete¹, Jorge Carretero-Ortega¹, Hans Rosenfeldt, Ricardo Hernández-García¹, J. Victor Calderón-Salinas^¶, Guadalupe Reyes-Cruz^||, J. Silvio Gutkind, and José Vázquez-Prado²

From the Departments of Pharmacology, ^||Cell Biology, and ^¶Biochemistry, CINVESTAV-IPN, Apartado Postal 14-740, México D.F., 07000 Mexico and the Oral and Pharyngeal Cancer Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892

Polarized cell migration results from the transduction of extra-cellular cues promoting the activation of Rho GTPases with the intervention of multidomain proteins, including guanine exchange factors. P-Rex1 and P-Rex2 are Rac GEFs connecting G and phosphatidylinositol 3-kinase signaling to Rac activation. Their complex architecture suggests their regulation by protein-protein interactions. Novel mechanisms of activation of Rho GTPases are associated with mammalian target of rapamycin (mTOR), a serine/threonine kinase known as a central regulator of cell growth and proliferation. Recently, two independent multiprotein complexes containing mTOR have been described. mTORC1 links to the classical rapamycin-sensitive pathways relevant for protein synthesis; mTORC2 links to the activation of Rho GTPases and cytoskeletal events via undefined mechanisms. Here we demonstrate that P-Rex1 and P-Rex2 establish, through their tandem DEP domains, interactions with mTOR, suggesting their potential as effectors in the signaling of mTOR to Rac activation and cell migration. This possibility was consistent with the effect of dominant-negative constructs and short hairpin RNA-mediated knockdown of P-Rex1, which decreased mTOR-dependent leucine-induced activation of Rac and cell migration. Rapamycin, a widely used inhibitor of mTOR signaling, did not inhibit Rac activity and cell migration induced by leucine, indicating that P-Rex1, which we found associated to both mTOR complexes, is only active when in the mTORC2 complex. mTORC2 has been described as the catalytic complex that phosphorylates AKT/PKB at Ser-473 and elicits activation of Rho GTPases and cytoskeletal reorganization. Thus, P-Rex1 links mTOR signaling to Rac activation and cell migration.

Received for publication, May 8, 2007

^* This work was supported by Consejo Nacional de Ciencia y Tecnologia Grants 43970-Q (to J. V. P.) and 45957 (to G. R. C.), National Institutes of Health Grant R01TW006664 (to J. V. P.), and in part by NIDCR, National Institutes of Health. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The on-line version of this article (available at http://www.jbc.org) contains supplemental Fig. S1.

¹ Supported by fellowship from Consejo Nacional de Ciencia y Tecnologia.

² To whom correspondence should be addressed. Tel.: 52-55-5061-3380; Fax: 52-55-5061-3394; E-mail: jvazquez{at}cinvestav.mx.

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