title: Comparison of M-line and other myofibril components during reversible phorbol ester treatment.
abstract: The events occurring during phorbol ester mediated destruction of myofibrils in differentiated muscle cells were followed at the fluorescence and electron microscope levels using antibodies which bind troponin-T, a newly discovered 185 000 dalton M-line protein called myomesin and muscle type creatine kinase. The following series of events is proposed. Within one day of phorbol ester treatment, Z-bands and thin filaments, including troponin-T, are absent from many myofibrils resulting in the rapid loss of longitudinal and lateral alignment. A-bands become randomly oriented and clustered into ever smaller compartments within the rounding, myosac-like, multinucleated cells until after 3 days of treatment they too disappear. The M-line proteins are always present in existing A-bands. These results suggest that the Z-band and associated structures are responsible for the maintenance of alignment and the lateral register of myofibrils, whereas the M-line is responsible for the structural integrity of the A-band. When phorbol ester is removed, the cells revert to a myotube morphology and within 2 to 3 days are filled with myofibrils. A comparison of the appearance of troponin-T and the 185 000 dalton myomesin in the recovery period to their appearance during normal myofibrillogenesis reveals that these proteins are more temporally co-ordinated during myofibrillogenesis than in the phorbol ester experimental system.
mesh_terms: D000818:Animals; D030161:Avian Proteins; D002642:Chick Embryo; D064211:Connectin; D005455:Fluorescent Antibody Technique; D009124:Muscle Proteins / Q000378:metabolism*; D009132:Muscles / Q000033:anatomy & histology / Q000378:metabolism*; D009210:Myofibrils / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D010704:Phorbols / Q000494:pharmacology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D030161:Avian Proteins; D064211:Connectin; D009124:Muscle Proteins; D010704:Phorbols; C036203:Z-protein (muscle), chicken; D013755:Tetradecanoylphorbol Acetate