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Rapid inhibition of myogenin-driven acetylcholine receptor subunit gene transcription
C F Huang1, Y S Lee, M M Schmidt
1Department of Biochemistry and Cell Biology, State University of New York at Stony Brook 11794.
Abstract:
In investigating the coupling of depolarization and transcription in skeletal muscle we have focused on how protein kinase C suppresses acetylcholine receptor subunit genes. The activity of acetylcholine receptor subunit promoters in non-muscle cells co-transfected with myogenic factors and E proteins was measured, and their response to protein kinase C activation analyzed. To simplify interpretation of results, gene activities rather than levels of reporter enzymes were assayed, transcriptional effects of phorbol esters were determined, with drug exposures brief enough to preclude kinase depletion, and analysis was carried out with HeLa cells, which are not liable to myogenic conversion. Myogenin, which had been postulated previously to play a role in denervation supersensitivity (Neville et al., Mol. Cell. Neurobiol., 12, 511-527, 1992), was found to be the only myogenic factor whose inactivation kinetics can account for the plasma membrane-protein kinase C-receptor gene cascade observed in intact muscle (Huang et al., Neuron, 9, 671-678, 1992).
Insights
Protein kinase C activation suppresses acetylcholine receptor subunit genes in skeletal muscle. Myogenin
Area of Science:
- Molecular biology
- Neuroscience
- Muscle physiology
Background:
- Depolarization and transcription are coupled in skeletal muscle.
- Protein kinase C (PKC) is implicated in regulating gene expression.
- Acetylcholine receptor (AChR) subunit gene expression is critical for neuromuscular function.
Purpose of the Study:
- To investigate how protein kinase C (PKC) suppresses acetylcholine receptor (AChR) subunit genes.
- To elucidate the role of myogenic factors in this regulatory pathway.
Main Methods:
- Assayed gene activity of AChR subunit promoters in co-transfected HeLa cells.
- Analyzed the response to protein kinase C activation using phorbol esters.
- Focused on transcriptional effects with brief drug exposures to avoid kinase depletion.
Main Results:
- Myogenin was identified as the sole myogenic factor whose inactivation kinetics explain the observed PKC-mediated receptor gene cascade.
- PKC activation was shown to suppress AChR subunit gene expression.
Conclusions:
- Myogenin's inactivation kinetics are key to understanding the plasma membrane-PKC-receptor gene cascade in muscle.
- This study clarifies a crucial mechanism linking muscle activity to gene regulation.