title: RhoA GTPase regulates M-cadherin activity and myoblast fusion.
abstract: The Rho family of GTP-binding proteins plays critical roles during myogenesis induction. To elucidate their role later during myogenesis, we have analyzed RhoA function during myoblast fusion into myotubes. We find that RhoA activity is rapidly and transiently increased when cells are shifted into differentiation medium and then is decreased until myoblast fusion. RhoA activity must be down-regulated to allow fusion, because expression of a constitutively active form of RhoA (RhoAV14) inhibits this process. RhoAV14 perturbs the expression and localization of M-cadherin, a member of the Ca2+-dependent cell-cell adhesion molecule family that has an essential role in skeletal muscle cell differentiation. This mutant does not affect N-cadherin and other proteins involved in myoblast fusion, beta1-integrin and ADAM12. Active RhoA induces the entry of M-cadherin into a degradative pathway and thus decreases its stability in correlation with the monoubiquitination of M-cadherin. Moreover, p120 catenin association with M-cadherin is decreased in RhoAV14-expressing cells, which is partially reverted by the inhibition of the RhoA effector Rho-associated kinase ROCK. ROCK inhibition also restores M-cadherin accumulation at the cell-cell contact sites. We propose that the sustained activation of the RhoA pathway inhibits myoblast fusion through the regulation of p120 activity, which controls cadherin internalization and degradation.
authors.affiliation: Centre de Recherches de Biochimie Macromoléculaire, Centre National de la Recherche Scientifique Formation de Recherche en Evolution 2593, 34293 Montpellier Cedex, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Charrasse
authors.forename: Franck
authors.initials: F
authors.lastname: Comunale
authors.forename: Yaël
authors.initials: Y
authors.lastname: Grumbach
authors.forename: Francis
authors.initials: F
authors.lastname: Poulat
authors.forename: Anne
authors.initials: A
authors.lastname: Blangy
authors.forename: Cécile
authors.initials: C
authors.lastname: Gauthier-Rouvière
mesh_terms: D051722:ADAM Proteins / Q000378:metabolism; D000072199:ADAM12 Protein; D000818:Animals; D015820:Cadherins / Q000032:analysis / Q000378:metabolism*; D051177:Catenins; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002459:Cell Fusion; D002460:Cell Line; D019012:Integrin beta1 / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D032446:Myoblasts / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D034622:RNA Interference; D020742:rhoA GTP-Binding Protein / Q000378:metabolism / Q000502:physiology*; D000095002:Delta Catenin
chemical_list: D015820:Cadherins; D051177:Catenins; D015815:Cell Adhesion Molecules; D019012:Integrin beta1; D010750:Phosphoproteins; C070896:M-cadherin; D051722:ADAM Proteins; D000072199:ADAM12 Protein; C096115:Adam12 protein, mouse; D020742:rhoA GTP-Binding Protein; D000095002:Delta Catenin; C000722349:Ctnnd1 protein, mouse