Control of myogenic factor genes by the membrane depolarization/protein kinase C cascade in chick skeletal muscle.

Myogenic factor genes were found to respond differentially to electrical stimulation of denervated chick skeletal muscle. Myogenin gene activity declined rapidly (t1/2: approximately 2 min), comparable to the rate of acetylcholine receptor (AChR) gene inactivation, while other myogenic bHLH genes either lost activity more slowly (MyoD) or not at all (myf5, herculin). Protein kinase C (PKC) is known to couple membrane activity to AChR gene inactivation; myogenin gene transcription was also rapidly blocked by the PKC activator PMA, whereas electrostimulation remained without effect on myogenin gene activity in muscle that was either exposed to the kinase inhibitor staurosporine or chronically treated with PMA to deplete PKC. These results attest to a special role for myogenin in the activation of AChR genes in denervation supersensitivity.