Myosin light chain diphosphorylation is enhanced by growth promotion of cultured smooth muscle cells

Minoru Seto, Katsuhiko Sakurada, Kristine E. Kamm, James T. Stull, Yasuharu Sasaki

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18 Scopus citations


The characteristics of actively growing smooth muscle cells (a variant, SM-3) were compared with those of growth-arrested cells with regard to response of myosin light chain (MLC) phosphorylation. Augmented MLC phosphorylation, in particular diphosphorylation, was observed in actively growing cells when stimulated with 30 μM prostaglandin F (PGF ). The maximum level of diphosphorylation in growing cells was significantly higher than that in growth-arrested cells. The MLC diphosphorylation was sensitive to protein kinase C down-regulation by phorbol dibutylate and pretreatment by the protein kinase inhibitors, staurosporine (30 nM) and isoquinoline sulphonamide HA 1077 (20 μM). The actively growing cells contained larger amounts of protein kinase C than growth-arrested cells. The phosphorylation sites of mono- and diphospho-MLC were determined to be MLC kinase-dependent sites (Thr18, Ser19). The PGF concentration/response curves of MLC diphosphorylation were shifted to the left and upwards in the presence of the protein phosphatase inhibitor calyculin A. These results suggest that PGF stimulation of actively growing SM-3 cells augments MLC kinase-dependent MLC diphosphorylation. Protein kinase C is involved indirectly in this reaction, possibly through MLC phosphatase-sensitive regulatory mechanisms.

Original languageEnglish (US)
Pages (from-to)7-13
Number of pages7
JournalPflügers Archiv
Issue number1
Publication statusPublished - May 1996



  • Myosin light chain mono and diphosphorylation
  • Phosphatase
  • Protein kinase C
  • Smooth muscle cell

ASJC Scopus subject areas

  • Physiology (medical)
  • Physiology
  • Clinical Biochemistry

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