mTOR Substrates Antibody Sampler Kit

The mammalian target of rapamycin (mTOR, FRAP, RAFT) is a Ser/Thr protein kinase (1-3) that functions as an ATP and amino acid sensor to balance nutrient availability and cell growth (4,5). When sufficient nutrients are available, mTOR responds to a phosphatidic acid-mediated signal to transmit a positive signal to p70 S6 kinase and participate in the inactivation of the eIF4E inhibitor, 4E-BP1 (6). These events result in the translation of specific mRNA subpopulations. mTOR is phosphorylated at Ser2448 via the PI3 kinase/Akt signaling pathway and autophosphorylated at Ser2481 (7,8). mTOR plays a key role in cell growth and homeostasis and may be abnormally regulated in tumors. For these reasons, mTOR is currently under investigation as a potential target for anti-cancer therapy (9).The regulatory associated protein of mTOR (Raptor) interacts with mTOR to mediate mTOR signaling to downstream targets (10,11). Raptor binds to mTOR substrates, such as 4E-BP1 and p70 S6 kinase, through their TOR signaling (TOS) motifs and is required for mTOR-mediated substrate phosphorylation (12,13). Binding of the FKBP12-rapamycin complex to mTOR inhibits mTOR-raptor interaction, which suggests a mechanism for the inhibition of mTOR signaling by rapamycin (14). This mTOR-raptor interaction and its regulation by nutrients and/or rapamycin are dependent on a protein called GβL (15). GβL is part of the rapamycin-insensitive complex between mTOR and rictor (rapamycin-insensitive companion of mTOR) and may mediate rictor-mTOR signaling to PKCα and other downstream targets (16). The rictor-mTOR complex has been identified as the previously elusive PDK2 responsible for the phosphorylation of Akt/PKB at Ser473, which is required for PDK1 phosphorylation of Akt/PKB at Thr308 and full activation of Akt/PKB (17). 1.Sabers, C.J. et al. (1995) J Biol Chem 270, 815-22. 2.Brown, E.J. et al. (1994) Nature 369, 756-8. 3.Sabatini, D.M. et al. (1994) Cell 78, 35-43. 4.Gingras, A.C. et al. (2001) Genes Dev 15, 807-26. 5.Dennis, P.B. et al. (2001) Science 294, 1102-5. 6.Fang, Y. et al. (2001) Science 294, 1942-5. 7.Navé, B.T. et al. (1999) Biochem J 344 Pt 2, 427-31. 8.Peterson, R.T. et al. (2000) J Biol Chem 275, 7416-23. 9.Huang, S. and Houghton, P.J. (2003) Curr Opin Pharmacol 3, 371-7. 10.Hara, K. et al. (2002) Cell 110, 177-89. 11.Kim, D.H. et al. (2002) Cell 110, 163-75. 12.Beugnet, A. et al. (2003) J Biol Chem 278, 40717-22. 13.Nojima, H. et al. (2003) J Biol Chem 278, 15461-4. 14.Oshiro, N. et al. (2004) Genes Cells 9, 359-66. 15.Kim, D.H. et al. (2003) Mol Cell 11, 895-904. 16.Sarbassov, D.D. et al. (2004) Curr Biol 14, 1296-302. 17.Sarbassov, D.D. et al. (2005) Science 307, 1098-101.