Identification of a human Akt3 (protein kinase B gamma) which contains theregulatory serine phosphorylation site

The family of protein kinases called Akt, protein kinase B (PKB), or relate d to A and C kinase (RAC) have been implicated in numerous biological proce sses including adipocyte and muscle differentiation, glycogen synthesis, gl ucose uptake, apoptosis and cellular proliferation. There are 3 known isofo rms of this enzyme in mammalian cells (1/alpha, 2/alpha and 3/gamma), Akt1 and 2 contain a key regulatory serine phosphorylation site in the carboxy-t erminal region of the protein, However, the reported sequence of the rat Ak t3 protein differed significantly from this in that it lacked 25 amino acid s in the C-terminal region, including this key regulatory serine phosphoryl ation site (Biochem. Biophys. Res. Commun. 216, 526-534). In the present st udies we show that the deduced sequence of human Akt3 contains this serine and that it is phosphorylated in response to insulin. These results indicat e that human Akt3 is regulated similarly to Akt1 and Akt2. (C) 1999 Academi c Press.