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Inhibition of apoptosis as one of the functions of the Akt/PKB kinase Volume 4, issue 2, Mars-Avril 1998

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Akt is the cellular homologue of the v-akt oncogene transduced in an oncogenic murine retrovirus. Akt is a 59 kDa serine/threonine kinase which is activated in a variety of cells by growth factors and cytokines. Besides a catalytic domain Akt has a pleckstrin homology domain (PH domain). Akt is activated through the binding of its PH domain to specific membrane phospholipids generated after membrane receptor activation and through its phosphorylation on serine and threonine residues by other cellular kinases. Little is known on the targets of Akt. Akt phosphorylates GSK3 which is involved in glycogen synthesis and in b catenin activation. It has been also suggested that Akt regulates the activity of the p70S6 kinase and thereby protein synthesis. Very recent results have demonstrat-ed that Bad is a direct target of Akt. Phosphorylated Bad is sequestered in the cytosol bound to 14-3-3 proteins and does no more heterodimerize with Bcl-XL. These data indicate that Akt plays a major role in cell survival.