title: m-Calpain implication in cell cycle during muscle precursor cell activation.
abstract: Milli-calpain, a member of the ubiquitous cysteine protease family, is known to control late events of cell-cell fusion in skeletal muscle tissue through its involvement in cell membrane and cytoskeleton component reorganization. In this report, we describe the characterization of m-calpain compartmentalization and activation during the initial steps of muscle precursor cell recruitment and differentiation. By immunofluorescence analysis, we show that m-calpain is present throughout the cell cycle in the nucleus of proliferating myoblast C2 cells. However, when myoblasts enter a quiescent/G0 stage, m-calpain staining is detected only in the cytoplasm. Moreover, comparison of healthy and injured muscle shows distinct m-calpain localization in satellite stem cells. Indeed, m-calpain is not found in quiescent satellite cells, but following muscle injury, when satellite cells start to proliferate, m-calpain appears in the nucleus. To determine the implication of m-calpain during the cell cycle progression, quiescent myoblasts were forced to re-enter the cell cycle in the presence or not of the specific calpain inhibitor MDL 28170. We demonstrate that this calpain inhibitor blocks the cell cycle, prevents accumulation of MyoD in the G1 phase and enhances Myf5 expression. These data support an important new role for m-calpain in the control of muscle precursor cell activation and thus suggest its possible implication during the initial events of muscle regeneration.
authors.affiliation: UMR 5539-CNRS, Laboratoire de Motilité Cellulaire, EPHE, cc107, University of Montpellier 2 place Eugène Bataillon, 34090 France. raynaudf@univ-montp2.fr
authors.forename: F
authors.initials: F
authors.lastname: Raynaud
authors.forename: G
authors.initials: G
authors.lastname: Carnac
authors.forename: A
authors.initials: A
authors.lastname: Marcilhac
authors.forename: Y
authors.initials: Y
authors.lastname: Benyamin
mesh_terms: D000818:Animals; D002154:Calpain / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002451:Cell Compartmentation / Q000502:physiology; D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology; D002460:Cell Line; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016193:G1 Phase / Q000235:genetics; D006801:Humans; D051379:Mice; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000378:metabolism*; D009124:Muscle Proteins / Q000378:metabolism; D018482:Muscle, Skeletal / Q000254:growth & development* / Q000293:injuries / Q000378:metabolism*; D017570:MyoD Protein / Q000378:metabolism; D051787:Myogenic Regulatory Factor 5; D012038:Regeneration / Q000502:physiology; D016192:Resting Phase, Cell Cycle / Q000235:genetics; D032496:Satellite Cells, Skeletal Muscle / Q000166:cytology / Q000378:metabolism; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; C497417:MYF5 protein, human; D009124:Muscle Proteins; C497418:Myf5 protein, mouse; D017570:MyoD Protein; D051787:Myogenic Regulatory Factor 5; D015534:Trans-Activators; D002154:Calpain; C449000:m-calpain