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Polyamines inhibit myosin phosphatase and increase LC20 phosphorylation and force in smooth muscle

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Author

Summary, in English

The increase in Ca(2+)-activated force caused by polyamines in beta-escin-permeabilized guinda pig ileum is shown to be associated with increased myosin 20-kDa light chain (LC20) phosphorylation and shortening velocity. Myosin LC20 dephosphorylation with arrested kinase activity was slower in the presence of 1 mM spermine. Smooth muscle phosphatases (SMP-I, -II, -III, and -IV) isolated from turkey gizzard are all active against phosphorylated LC20, but only SMP-III and -IV dephosphorylate heavy meromyosin (HMM). Spermine inhibited SMP-III activity toward LC20 but stimulated HMM dephosphorylation, whereas SMP-IV was inhibited with both substrates. In contrast, SMP-I and -II were stimulated by spermine. The relative effects of different polyamines correlated with an increasing number of positive charges. Spermine did not affect binding of SMP-IV to myosin and did not dissociate any of the subunits of the enzyme. Incubation of permeabilized strips with SMP-IV resulted in attenuated responses to Ca2+, an effect that was opposed by spermine and abolished by microcystin-LR. We conclude that spermine selectively inhibits myosin phosphatase activity and suggest that polyamines function as endogenous myosin phosphatase inhibitors.

Publishing year

1995-09

Language

English

Pages

563-571

Publication/Series

American Journal of Physiology: Cell Physiology

Volume

269

Issue

3

Document type

Journal article

Publisher

American Physiological Society

Topic

  • Physiology

Keywords

  • Animals
  • Female
  • Gizzard
  • Guinea Pigs
  • Ileum
  • In Vitro Techniques
  • Muscle Contraction
  • Muscle, Smooth
  • Myosin Light Chains
  • Myosin-Light-Chain Kinase
  • Myosin-Light-Chain Phosphatase
  • Permeability
  • Phosphoprotein Phosphatases
  • Phosphoric Monoester Hydrolases
  • Phosphorylation
  • Polyamines
  • Spermine
  • Turkeys

Status

Published

Research group

  • Vascular Physiology

ISBN/ISSN/Other

  • ISSN: 1522-1563