The serine/threonine kinase Akt/PKB plays a critical role in executing multiple cellular metabolic pathways and in particular cellular energy metabolism. It can mediate cell survival, cell proliferation, cell growth and differentiation. Up-regulation of Akt activity can lead to tumorigenesis, whereas down-regulation of Akt activity can lead to degenerative diseases. We have previously shown that Akt is a major downstream effector of growth factor mediated cell survival. To determine the role of Akt in vivo and to genetically dissect its activities we have generated Akt knock-out (KO) mice and thus provided genetic evidence that Akt is required for cell survival in mammalian cells. Systematic analysis reveals that Akt intervenes in the apoptotic cascade by maintaining the integrity of mitochondria and inhibition of cytochrome c release. The ability of Akt to maintain mitochondrial integrity is dependent on glucose availability. Experimental evidence suggests that Akt mediates cell survival, at least in part, through the increase of mitochondrial hexokinase (mtHK) activity associated with mitochondria. The fact that mtHKs catalyze the first committed step in glycolysis, and their mitochondrial localization couples glucose metabolism to mitochondrial ATP synthesis, may explain the dependency of Akt-mediated cell survival on glucose. We propose that Akt-mediated cellular energy metabolism is recruited to the apoptotic cascade in mammalian cells. During the previous funding period we have shown the role of Akt in the regulation of the target of rapamycin (mTOR) and protein synthesis that are determinants of cell mass and cellular atrophy. We intend to verify whether the function of Akt in energy metabolism also contributes to the activity of mTOR and to cell mass. Our long-term goal is to dissect the functions of Akt in cell survival, cell growth, cellular metabolism, and differentiation and to understand how these functions interact with each other. To achieve this goal we have generated individual KO and DKO of the 3 akt genes and have been analyzing the phenotypes of these mice. In this grant application we will verify a link between the role of Akt in energy metabolism and its abilities to mediate cell survival and cell growth (cell mass). We will use the Akt KO mice and cells derived from these mice to provide genetic evidence for the role of Akt in these processes. ? ? ?
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