| Background |
Cell growth is a fundamental biological process whereby cells accumulate mass and increase in size. The mammalian TOR (mTOR) pathway regulates growth by coordinating energy and nutrient signals with growth factor-derived signals mTOR is a large protein kinase that is a component of two different complexes. The mTOR complex 1 (mTORC1), a target of rapamycin, contains mTOR, GβL, and raptor. mTORC2, insensitive to rapamycin, includes mTOR, GβL, Sin1, and rictor The mTORC2 complex phosphorylates Ser473 of Akt/PKB in vitro This phosphorylation is essential for full Akt/PKB activation. Furthermore, an siRNA knockdown of rictor inhibits Ser473 phosphorylation in 3T3-L1 adipocytes mTORC2 has also been shown to phosphorylate the rapamycin-resistant mutants of S6K1, another effector of mTOR In addition, phosphorylation of Sin1 at Thr86 by Akt/PKB was shown to regulate the activity of mTORC2 in adipocytes upon stimulation by growth factors.
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