title: Identification of a proline-rich Akt substrate as a 14-3-3 binding partner.
abstract: 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.
authors.affiliation: Department of Molecular Pharmacology, Stanford University, California 94305-5174, USA.
authors.forename: Kristina S
authors.initials: KS
authors.lastname: Kovacina
authors.forename: Grace Y
authors.initials: GY
authors.lastname: Park
authors.forename: Sun Sik
authors.initials: SS
authors.lastname: Bae
authors.forename: Andrew W
authors.initials: AW
authors.lastname: Guzzetta
authors.forename: Erik
authors.initials: E
authors.lastname: Schaefer
authors.forename: Morris J
authors.initials: MJ
authors.lastname: Birnbaum
authors.forename: Richard A
authors.initials: RA
authors.lastname: Roth
mesh_terms: D048948:14-3-3 Proteins; D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000032:analysis / Q000235:genetics; D002460:Cell Line; D007328:Insulin / Q000494:pharmacology; D051379:Mice; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010766:Phosphorylation; D011392:Proline; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D012333:RNA, Messenger / Q000032:analysis; D013912:Threonine / Q000378:metabolism; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism*
chemical_list: D048948:14-3-3 Proteins; D002352:Carrier Proteins; D007328:Insulin; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D013912:Threonine; D011392:Proline; D014446:Tyrosine 3-Monooxygenase; C494922:Akt2 protein, mouse; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt