Plasminogen activator in chick embryo muscle cells: induction of enzyme by RSV, PMA and retinoic acid

Area of Science:

• Cell Biology
• Molecular Biology
• Virology

Background:

• Plasminogen activator (PA) production is crucial in cellular processes.
• Understanding PA regulation is key to studying viral transformation and differentiation.

Purpose of the Study:

• To investigate the effects of Rous sarcoma virus (RSV), phorbol myristate acetate (PMA), and retinoic acid on plasminogen activator production in differentiating chick myogenic cultures.
• To compare these effects with those observed in chick fibroblast cultures.
• To explore the role of cyclic AMP (cAMP) in mediating these responses.

Main Methods:

• Differentiating chick myogenic cultures were used.
• Cultures were infected with a temperature-sensitive Rous sarcoma virus (RSV) mutant.
• Plasminogen activator production was measured after treatment with RSV, PMA, and retinoic acid.
• The influence of cAMP on enzyme induction was assessed.

Main Results:

• RSV transformation, PMA, and retinoic acid all induced high levels of plasminogen activator production in differentiating myotubes, even without DNA synthesis.
• While slower than in fibroblasts, virus-induced enzyme synthesis in myogenic cultures reached comparable levels.
• cAMP weakly stimulated enzyme synthesis in myotubes, contrasting with its strong repression in fibroblasts.

Conclusions:

• RSV, PMA, and retinoic acid are potent inducers of plasminogen activator production in differentiating myogenic cells.
• The mechanisms of enzyme induction by RSV and PMA in myotubes do not appear to be primarily mediated through cAMP signaling pathways.
• Myogenic cultures provide a model to study the generality of these inductive effects.