title: Phosphorylation of ezrin-radixin-moesin-binding phosphoprotein 50 (EBP50) by Akt promotes stability and mitogenic function of S-phase kinase-associated protein-2 (Skp2).
abstract: The regulation of the cell cycle by the ubiquitin-proteasome system is dependent on the activity of E3 ligases. Skp2 (S-phase kinase associated protein-2) is the substrate recognition subunit of the E3 ligase that ubiquitylates the cell cycle inhibitors p21(cip1) and p27(kip1) thus promoting cell cycle progression. Increased expression of Skp2 is frequently observed in diseases characterized by excessive cell proliferation, such as cancer and neointima hyperplasia. The stability and cellular localization of Skp2 are regulated by Akt, but the molecular mechanisms underlying these effects remain only partly understood. The scaffolding protein Ezrin-Binding Phosphoprotein of 50 kDa (EBP50) contains two PDZ domains and plays a critical role in the development of neointimal hyperplasia. Here we report that EBP50 directly binds Skp2 via its first PDZ domain. Moreover, EBP50 is phosphorylated by Akt on Thr-156 within the second PDZ domain, an event that allosterically promotes binding to Skp2. The interaction with EBP50 causes cytoplasmic localization of Skp2, increases Skp2 stability and promotes proliferation of primary vascular smooth muscle cells. Collectively, these studies define a novel regulatory mechanism contributing to aberrant cell growth and highlight the importance of scaffolding function of EBP50 in Akt-dependent cell proliferation.
authors.affiliation: From the Department of Pharmacology and Chemical Biology, Department of Pharmacology, Brain Science and Engineering Institute, School of Medicine, Kungpook National University, Daegu 702-701, Korea, and.
authors.forename: Gyun Jee
authors.initials: GJ
authors.lastname: Song
authors.affiliation: From the Department of Pharmacology and Chemical Biology.
authors.forename: Kristen L
authors.initials: KL
authors.lastname: Leslie
authors.affiliation: From the Department of Pharmacology and Chemical Biology.
authors.forename: Stacey
authors.initials: S
authors.lastname: Barrick
authors.affiliation: From the Department of Pharmacology and Chemical Biology.
authors.forename: Tatyana
authors.initials: T
authors.lastname: Mamonova
authors.affiliation: Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755.
authors.forename: Jeremy M
authors.initials: JM
authors.lastname: Fitzpatrick
authors.affiliation: From the Department of Pharmacology and Chemical Biology.
authors.forename: Kenneth W
authors.initials: KW
authors.lastname: Drombosky
authors.affiliation: From the Department of Pharmacology and Chemical Biology.
authors.forename: Noah
authors.initials: N
authors.lastname: Peyser
authors.affiliation: From the Department of Pharmacology and Chemical Biology.
authors.forename: Bin
authors.initials: B
authors.lastname: Wang
authors.affiliation: Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755.
authors.forename: Maria
authors.initials: M
authors.lastname: Pellegrini
authors.affiliation: Vascular Medicine Institute, and Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15260.
authors.forename: Philip M
authors.initials: PM
authors.lastname: Bauer
authors.affiliation: From the Department of Pharmacology and Chemical Biology.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Friedman
authors.affiliation: Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755.
authors.forename: Dale F
authors.initials: DF
authors.lastname: Mierke
authors.affiliation: From the Department of Pharmacology and Chemical Biology, Vascular Medicine Institute, and alb138@pitt.edu.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Bisello
mesh_terms: D000818:Animals; D049109:Cell Proliferation; D002478:Cells, Cultured; D006801:Humans; D051379:Mice; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D055550:Protein Stability; D051057:Proto-Oncogene Proteins c-akt / Q000737:chemistry / Q000378:metabolism*; D044786:S-Phase Kinase-Associated Proteins / Q000737:chemistry / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers / Q000737:chemistry / Q000378:metabolism*
chemical_list: D010750:Phosphoproteins; D044786:S-Phase Kinase-Associated Proteins; D017923:Sodium-Hydrogen Exchangers; C093376:sodium-hydrogen exchanger regulatory factor; D051057:Proto-Oncogene Proteins c-akt
keywords: Akt PKB; Cell Proliferation; EBP50; PDZ Domain; Phosphorylation; Skp2; Vascular Smooth Muscle Cells; nherf; nherf1