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Polylysine activates smooth muscle actin-myosin interaction without LC20 phosphorylation
P T Szymanski1, J D Strauss, G Doerman
1Department of Physiology and Biophysics, College of Medicine, University of Cincinnati, Ohio 45267-0576.
The American Journal of Physiology
|June 1, 1992
Summary
Polylysine, a positively charged molecule, directly enhances smooth muscle contraction by increasing actin-myosin interaction, independent of myosin light chain phosphorylation. This finding offers a new tool for studying muscle activation mechanisms.
Area of Science:
- Biochemistry
- Muscle Physiology
Background:
- Actin-myosin interaction is regulated by myosin light chain phosphorylation.
- Phosphatase inhibitors enhance smooth muscle contraction.
- Polylysine inhibits type II phosphatase activity against phosphorylated myosin light chains.
Purpose of the Study:
- To investigate the effects of polylysine on actin-myosin interaction in smooth muscle.
- To determine if polylysine can elicit contraction in smooth muscle models.
Main Methods:
- Used permeabilized guinea pig taenia coli fibers and bovine aortic actomyosin.
- Administered polylysine in low calcium conditions.
- Measured force generation and ATPase activity.
- Utilized heparin to inhibit polylysine effects.
- Assessed myosin light chain phosphorylation and 32P incorporation.
Main Results:
- Polylysine induced significant contraction in smooth muscle fibers.
- Polylysine dose-dependently stimulated ATPase activity in fibers and actomyosin.
- Heparin abolished polylysine-induced stimulation.
- Polylysine did not alter myosin light chain phosphorylation levels.
Conclusions:
- Polylysine enhances actin-myosin interaction directly, not through myosin light chain phosphorylation.
- Polylysine acts as a direct activator of contractile proteins in smooth muscle.
- Polylysine is a valuable tool for probing smooth muscle activation mechanisms.