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Molecular and Cellular Biology, February 2004, p. 1245-1255, Vol. 24, No. 3
0270-7306/04/$08.00+0 DOI: 10.1128/MCB.24.3.1245-1255.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.
,
Marie Vandromme,2,
Sabine Caussanel,1 Laure Valdacci,1,2 Dominique Baas,
Marc Vidal,3 Gilbert Brun,1 Laurent Schaeffer,2 and Evelyne Goillot1*
Equipe de Biologie des Regulations Cellulaires,1 Equipe Differenciation Neuromusculaire, LBMC, CNRS UMR5665, ENS Lyon, IFR128 BioSciences Lyon-Gerland, Lyon, France,2 Dana Farber Cancer Institute and Department of Genetics, Harvard Medical School, Boston, Massachusetts3
Received 29 July 2003/ Returned for modification 10 September 2003/ Accepted 4 November 2003
In this work, we report the implication of the pleckstrin homology (PH) domain-containing protein CKIP-1 in phosphatidylinositol 3-kinase (PI3-K)-regulated muscle differentiation. CKIP-1 is upregulated during muscle differentiation in C2C12 cells. We show that CKIP-1 binds to phosphatidylinositol 3-phosphate through its PH domain and localizes to the plasma membrane in a PI3-K-dependent manner. Activation of PI3-K by insulin or expression of an active form of PI3-K p110 induces a rapid translocation of CKIP-1 to the plasma membrane. Conversely, expression of the 3-phosphoinositide phosphatase myotubularin or PI3-K inhibition by LY294002, wortmannin, or mutant p85 abolishes CKIP-1 binding to the membrane. Upon induction of differentiation in low-serum medium, CKIP-1 overexpression in C2C12 myoblasts first promotes proliferation and then stimulates the expression of myogenin and cell fusion in a manner reminiscent of the dual positive effect of insulin-like growth factors on muscle cells. Interference with the PI3-K pathway impedes the effect of CKIP-1 on C2C12 cell differentiation. Finally, silencing of CKIP-1 by RNA interference abolishes proliferation and delays myogenin expression. Altogether, these data strongly implicate CKIP-1 as a new component of PI3-K signaling in muscle differentiation.
Present address: Department of Biochemistry, Duke University Medical Center, Durham, N.C.
A.S. and M.V. contributed equally to this work.
Present address: Laboratoire Matrice Extracellulaire et Developpement, CNRS UMR 5086, Institut de Biologie et Chimie des Proteines, Lyon, France.
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