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

Swärd, Karl LU ; Pato, M D; Nilsson, Bengt-Olof LU ; Nordström, Ina LU and Hellstrand, Per LU (1995) In American Journal of Physiology 269(3). p.563-571
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. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
American Journal of Physiology
volume
269
issue
3
pages
563 - 571
publisher
American Pysiological Society
external identifiers
  • pmid:7573385
  • scopus:0029130591
ISSN
0002-9513
language
English
LU publication?
yes
id
a318afe9-3167-40d9-9a17-81d8381f4c66 (old id 1109022)
alternative location
http://ajpcell.physiology.org/cgi/reprint/269/3/C563
date added to LUP
2008-07-25 12:27:54
date last changed
2017-01-01 07:04:17
@article{a318afe9-3167-40d9-9a17-81d8381f4c66,
  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 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.},
  author       = {Swärd, Karl and Pato, M D and Nilsson, Bengt-Olof and Nordström, Ina and Hellstrand, Per},
  issn         = {0002-9513},
  language     = {eng},
  number       = {3},
  pages        = {563--571},
  publisher    = {American Pysiological Society},
  series       = {American Journal of Physiology},
  title        = {Polyamines inhibit myosin phosphatase and increase LC20 phosphorylation and force in smooth muscle},
  volume       = {269},
  year         = {1995},
}