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

Swärd, KarlLund University,Lunds universitet,Kärlfysiologi,Forskargrupper vid Lunds universitet,Vascular Physiology,Lund University Research Groups (author)

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.

MEDICIN OCH HÄLSOVETENSKAP Medicinska och farmaceutiska grundvetenskaper Fysiologi hsv//swe
MEDICAL AND HEALTH SCIENCES Basic Medicine Physiology hsv//eng
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

Pato, M DUniversity of Saskatchewan (author)
Nilsson, Bengt-OlofLund University,Lunds universitet,Kärlfysiologi,Forskargrupper vid Lunds universitet,Vascular Physiology,Lund University Research Groups(Swepub:lu)mphy-bon (author)
Nordström, InaLund University,Lunds universitet,Kärlfysiologi,Forskargrupper vid Lunds universitet,Vascular Physiology,Lund University Research Groups(Swepub:lu)mphy-ino (author)
Hellstrand, PerLund University,Lunds universitet,Kärlfysiologi,Forskargrupper vid Lunds universitet,Vascular Physiology,Lund University Research Groups(Swepub:lu)mphy-phe (author)
KärlfysiologiForskargrupper vid Lunds universitet (creator_code:org_t)

By the author/editor: Swärd, Karl; Pato, M D; Nilsson, Bengt-O ...; Nordström, Ina; Hellstrand, Per

About the subject

MEDICAL AND HEALTH SCIENCES: MEDICAL AND HEAL ...; and Basic Medicine; and Physiology

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