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

Swärd, Karl LU ; Pato, M D; Nilsson, B O LU ; Nordström, I LU and Hellstrand, P LU (1995) In American Journal of Physiology 269(3 Pt 1). p.71-563
Abstract

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... (More)

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.

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subject
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
in
American Journal of Physiology
volume
269
issue
3 Pt 1
pages
71 - 563
publisher
American Pysiological Society
external identifiers
  • Scopus:0029130591
ISSN
0002-9513
language
English
LU publication?
yes
id
9e677a59-6747-43e3-8eb7-6e8d1847f492
date added to LUP
2016-06-17 16:40:06
date last changed
2016-10-13 05:10:16
@misc{9e677a59-6747-43e3-8eb7-6e8d1847f492,
  abstract     = {<p>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.</p>},
  author       = {Swärd, Karl and Pato, M D and Nilsson, B O and Nordström, I and Hellstrand, P},
  issn         = {0002-9513},
  keyword      = {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},
  language     = {eng},
  number       = {3 Pt 1},
  pages        = {71--563},
  publisher    = {ARRAY(0x8bf3d00)},
  series       = {American Journal of Physiology},
  title        = {Polyamines inhibit myosin phosphatase and increase LC20 phosphorylation and force in smooth muscle},
  volume       = {269},
  year         = {1995},
}