TY - JOUR
T1 - Preferential binding of Grb2 or phosphatidylinositol 3-Kinase to the Met receptor has opposite effects on HGF-induced myoblast proliferation
AU - Leshem, Yael
AU - Gitelman, Inna
AU - Ponzetto, Carola
AU - Halevy, Orna
N1 - Funding Information:
We thank Eyal Bengal (Technion, Haifa, Israel) for critical reading of the manuscript and helpful discussions. We also thank Bruce Paterson (NIH, Bethesda, MD) for a generous gift of chicken anti-myogenin. The G3G4 antibody was obtained from the Developmental Studies Hybridoma Bank (Baltimore, MD) and the Department of Biology, University of Iowa (Iowa City, IA). This work was supported in part by a grant to O.H. and C.P. from the European Community (EC-Biomed BMH4-97-2767). The continuing support of the Com-pagnia di San Paolo and Fondazione CRT to C.P.’s laboratory is gratefully acknowledged.
PY - 2002/1/1
Y1 - 2002/1/1
N2 - Hepatocyte growth factor (HGF) and its receptor, Met, play a crucial role in regulating adult skeletal myoblast proliferation and differentiation. Met signaling is mediated by phosphorylation of two carboxy-terminal tyrosines, which act as docking sites for a number of intracellular mediators. These include Grb2 and p85, which couple the receptor with the Ras and phosphatidylinositol 3-kinase (PI3K) pathways, respectively. In this study, we define the role of these effectors in response to HGF by utilizing Met mutants, designed to obtain preferential coupling of Met to either Grb2 or PI3K or both. We found that relative to the wild-type receptor, enhanced binding to Grb2 further increases the incorporation of bromodeoxyuridine and the expression of Twist, while decreasing that of p27Kip1 and myogenin. Conversely, preferential coupling with PI3K induced cell-cycle withdrawal and differentiation. Whereas enhanced Grb2 binding increased the phosphorylation of the mitogen-activated protein kinase/extracellular signal-regulated protein kinases (MAPK/ERK) and abrogated that of p38 MAPK, PI3K had the opposite effect. PD098059 reversed the inhibitory effects of Met on cell proliferation and differentiation, while wortmannin had only a very marginal effect. Taken together, these data suggest that coupling of Met with Grb2 is necessary for HGF-mediated inhibition of muscle differentiation. This inhibition occurs only when PI3K signaling downstream of Met is low. Imposing an efficient coupling of PI3K to Met would lead to up-regulation of muscle regulatory factors and subsequent cell differentiation.
AB - Hepatocyte growth factor (HGF) and its receptor, Met, play a crucial role in regulating adult skeletal myoblast proliferation and differentiation. Met signaling is mediated by phosphorylation of two carboxy-terminal tyrosines, which act as docking sites for a number of intracellular mediators. These include Grb2 and p85, which couple the receptor with the Ras and phosphatidylinositol 3-kinase (PI3K) pathways, respectively. In this study, we define the role of these effectors in response to HGF by utilizing Met mutants, designed to obtain preferential coupling of Met to either Grb2 or PI3K or both. We found that relative to the wild-type receptor, enhanced binding to Grb2 further increases the incorporation of bromodeoxyuridine and the expression of Twist, while decreasing that of p27Kip1 and myogenin. Conversely, preferential coupling with PI3K induced cell-cycle withdrawal and differentiation. Whereas enhanced Grb2 binding increased the phosphorylation of the mitogen-activated protein kinase/extracellular signal-regulated protein kinases (MAPK/ERK) and abrogated that of p38 MAPK, PI3K had the opposite effect. PD098059 reversed the inhibitory effects of Met on cell proliferation and differentiation, while wortmannin had only a very marginal effect. Taken together, these data suggest that coupling of Met with Grb2 is necessary for HGF-mediated inhibition of muscle differentiation. This inhibition occurs only when PI3K signaling downstream of Met is low. Imposing an efficient coupling of PI3K to Met would lead to up-regulation of muscle regulatory factors and subsequent cell differentiation.
UR - http://www.scopus.com/inward/record.url?scp=0036343577&partnerID=8YFLogxK
U2 - 10.1006/excr.2002.5473
DO - 10.1006/excr.2002.5473
M3 - Article
AN - SCOPUS:0036343577
SN - 0014-4827
VL - 274
SP - 288
EP - 298
JO - Experimental Cell Research
JF - Experimental Cell Research
IS - 2
ER -