COMPARISON OF M-LINE AND OTHER MYOFIBRIL COMPONENTS DURING REVERSIBLE PHORBOL ESTER TREATMENT

  • 1 January 1984
    • journal article
    • research article
    • Vol. 33  (2) , 265-274
Abstract
The events occurring during phorbol ester mediated destruction of myofibrils in differentiated [chick] muscle cells were followed at the fluorescence and EM 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 1 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. The Z-band and associated structures may be 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 2-3 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.