Identification of a Proline-rich Akt Substrate as a 14-3-3 Binding Partner

• Published in: The Journal of biological chemistry Vol. 278; no. 12; pp. 10189 - 10194
• Main Authors: Kovacina, Kristina S, Park, Grace Y, Bae, Sun Sik, Guzzetta, Andrew W, Schaefer, Erik, Birnbaum, Morris J, Roth, Richard A
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 21.03.2003
• Subjects: 14-3-3 Proteins; Amino Acid Sequence; Animals; Carrier Proteins - analysis; Carrier Proteins - genetics; Cell Line; Insulin - pharmacology; Mice; Molecular Sequence Data; Molecular Weight; Phosphorylation; Proline; Protein-Serine-Threonine Kinases; Proto-Oncogene Proteins - metabolism; Proto-Oncogene Proteins c-akt; RNA, Messenger - analysis; Threonine - metabolism; Tyrosine 3-Monooxygenase - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M210837200

Akt (also called protein kinase B) is one of the major downstream targets of the phosphatidylinositol 3-kinase pathway. This protein kinase has been implicated in insulin signaling, stimulation of cellular growth, and inhibition of apoptosis as well as transformation of cells. Although a number of cellular proteins have been identified as putative targets of the enzyme, additional substrates may play a role in the varied responses elicited by this enzyme. We have used a combination of 14-3-3 binding and recognition by an antibody to the phosphorylation consensus of the enzyme to identify and isolate one of the major substrates of Akt, which is also a 14-3-3 binding protein. This 40-kDa protein, designated PRAS40, is a proline-rich Akt substrate. Demonstration that it is a substrate of Akt was accomplished by showing that 1) PRAS40 was phosphorylated in vitro by purified Akt on the same site that was phosphorylated in insulin-treated cells; 2) activation of an inducible Akt was alone sufficient to stimulate the phosphorylation of PRAS40; and 3) cells lacking Akt1 and Akt2 exhibit a diminished ability to phosphorylate this protein. Thus, PRAS40 is a novel substrate of Akt, the phosphorylation of which leads to the binding of this protein to 14-3-3.