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Calponin and smooth muscle regulation
J D Carmichael1, S J Winder, M P Walsh
1Department of Physiology, University of Massachusetts Medical School, Worcester 01655, USA.
Canadian Journal of Physiology and Pharmacology
|November 1, 1994
Summary
Calponin regulates smooth muscle contraction by inhibiting myosin ATPase. Its phosphorylation by specific kinases and dephosphorylation by phosphatases modulate this function, impacting muscle activity.
Area of Science:
- Biochemistry
- Molecular Biology
- Physiology
Background:
- Calponin is a protein involved in smooth muscle contraction.
- It inhibits the actin-activated Mg ATPase of smooth muscle myosin.
Purpose of the Study:
- To investigate the role of calponin phosphorylation in regulating smooth muscle contraction.
- To understand how protein kinases and phosphatases affect calponin's inhibitory function.
Main Methods:
- Confocal immunofluorescence microscopy to visualize calponin localization in smooth muscle cells.
- Measurement of calponin and myosin light chain phosphorylation in response to contractile stimuli and phosphatase inhibitors.
Main Results:
- Calponin is localized on thin filaments in smooth muscle cells.
- Phosphorylation by Ca2+/calmodulin-dependent protein kinase II or protein kinase C abolishes calponin's inhibitory effect.
- Dephosphorylation by type 2A protein phosphatase restores the inhibitory effect.
- Both calponin and myosin light chain phosphorylation increase during smooth muscle contraction induced by carbachol or okadaic acid.
Conclusions:
- Calponin phosphorylation-dephosphorylation is a key mechanism regulating smooth muscle contraction.
- This process involves the interplay of protein kinases and phosphatases.