Arachidonic acid inhibits myosin light chain phosphatase and sensitizes smooth muscle to calcium

Cui Gong Ming Cui Gong, A. Fuglsang, D. Alessi, S. Kobayashi, P. Cohen, A. V. Somlyo, A. P. Somlyo

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227 Citations (Scopus)


Arachidonic acid (AA) increased, at constant Ca2+, the levels of force and 20-kDa myosin light chain (MLC20) phosphorylation in permeabilized smooth muscle, and slowed relaxation and MLC20 dephosphorylation. The Ca2+-sensitizing effect of AA was not inhibited by inhibitors of AA metabolism (indomethacin, nordihydroguaiaretic acid, or propyl gallate), of protein kinase C (pseudopeptide) or by guanosine-5'-O-(β-thiodiphosphate) and was abolished by oxidation of AA in air. A non-metabolizable AA analog, 5,8,11,14-eicosatetraynoic acid) also had Ca2+-sensitizing effects. Extensive treatment with saponin abolished the Ca2+-sensitizing effects of phorbol 12,13-dibutyrate and guanosine-5'-O-(γ-thiotriphosphate), but not that of AA. A purified, oligomeric MLC20 phosphatase isolated from gizzard smooth muscle was dissociated into subunits by AA, and its activity was inhibited toward heavy meromyosin but not phosphorylase. We conclude that AA may act as a messenger-promoting protein phosphorylation through direct inhibition of the form of protein phosphatase(s) that dephosphorylate MLC20 in vivo.

Original languageEnglish
Pages (from-to)21492-21498
Number of pages7
JournalJournal of Biological Chemistry
Issue number30
Publication statusPublished - 1992

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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