title: S100B protein in myoblasts modulates myogenic differentiation via NF-kappaB-dependent inhibition of MyoD expression.
abstract: S100B, a Ca(2+)-binding protein of the EF-hand type, is expressed in myoblasts, the precursors of skeletal myofibers, and muscle satellite cells (this work). S100B has been shown to participate in the regulation of several intracellular processes including cell cycle progression and differentiation. We investigated regulatory activities of S100B within myoblasts by stable overexpression of S100B and by inhibition of S100B expression. Overexpression of S100B in myoblast cell lines and primary myoblasts resulted in inhibition of myogenic differentiation, evidenced by lack of expression of myogenin and myosin heavy chain (MyHC) and absence of myotube formation. S100B-overexpressing myoblasts showed reduced MyoD expression levels and unchanged Myf5 expression levels, compared with control myoblasts, and transient transfection of S100B-overexpressing myoblasts with MyoD, but not Myf5, restored differentiation and fusion in part. The transcriptional activity of NF-kappaB, a negative regulator of MyoD expression, was enhanced in S100B-overexpressing myoblasts, and blocking NF-kappaB activity resulted in reversal of S100B's inhibitory effects. Yin Yang1, a transcriptional repressor that is induced by NF-kappaB (p65) and mediates NF-kappaB inhibitory effects on several myofibrillary genes, also was upregulated in S100B-overexpressing myoblasts. Conversely, silencing S100B expression in myoblast cell lines by RNA interference resulted in reduced NF-kappaB activity and enhanced MyoD, myogenin and MyHC expression and myotube formation. Thus, intracellular S100B might modulate myoblast differentiation by interfering with MyoD expression in an NF-kappaB-dependent manner.
authors.affiliation: Department of Experimental Medicine and Biochemical Sciences, University of Perugia, Perugia, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Tubaro
authors.forename: Cataldo
authors.initials: C
authors.lastname: Arcuri
authors.forename: Ileana
authors.initials: I
authors.lastname: Giambanco
authors.forename: Rosario
authors.initials: R
authors.lastname: Donato
mesh_terms: D000818:Animals; D002417:Cattle; D002454:Cell Differentiation; D002460:Cell Line; D051550:I-kappa B Kinase / Q000378:metabolism; D051379:Mice; D024510:Muscle Development; D017570:MyoD Protein / Q000378:metabolism*; D032446:Myoblasts / Q000378:metabolism*; D051787:Myogenic Regulatory Factor 5 / Q000378:metabolism; D018008:Myogenin / Q000378:metabolism; D018995:Myosin Heavy Chains / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism*; D009414:Nerve Growth Factors / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D014162:Transfection; D050986:YY1 Transcription Factor / Q000378:metabolism
chemical_list: D017570:MyoD Protein; C057363:MyoD1 myogenic differentiation protein; C503801:Myog protein, mouse; C503803:Myog protein, rat; D051787:Myogenic Regulatory Factor 5; D018008:Myogenin; D016328:NF-kappa B; D009414:Nerve Growth Factors; D011994:Recombinant Proteins; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins; C579159:S100b protein, mouse; C579158:S100b protein, rat; D050986:YY1 Transcription Factor; D051550:I-kappa B Kinase; D018995:Myosin Heavy Chains