Phosphorylation of myosin light chain kinase by the multifunctional calmodulin-dependent protein kinase II in smooth muscle cells

Malú G. Tansey, R. Ann Word, Hiroyoshi Hidaka, Harold A. Singer, Charles M. Schworer, Kristine E. Kamm, James T. Stull

Research output: Contribution to journalArticle

97 Scopus citations

Abstract

Stimulation of tracheal smooth muscle cells in culture with ionomycin resulted in a rapid increase in cytosolic free Ca2+ concentration ([Ca2+](i)) and an increase in both myosin light chain kinase and myosin light chain phosphorylation. These responses were markedly inhibited in the absence of extracellular Ca2+. Pretreatment of cells with 1-[N-O-bis(5- isoquinolinesulfonyl)-N-methyl-L-tyrosyl]-4-phenylpiperazine (KN-62), a specific inhibitor of the multifunctional calmodulin-dependent protein kinase II (CaM kinase II), did not affect the increase in [Ca2+](i) but inhibited ionomycin-induced phosphorylation of myosin light chain kinase at the regulatory site near the calmodulin-binding domain. KN-62 inhibited CaM kinase II activity toward purified myosin light chain kinase. Phosphorylation of myosin light chain kinase decreased its sensitivity to activation by Ca2+ in cell lysates. Pretreatment of cells with KN-62 prevented this desensitization to Ca2+ and potentiated myosin light chain phosphorylation. We propose that the Ca2+-dependent phosphorylation of myosin light chain kinase by CaM kinase II decreases the Ca2+ sensitivity of myosin light chain phosphorylation in smooth muscle.

Original languageEnglish (US)
Pages (from-to)12511-12516
Number of pages6
JournalJournal of Biological Chemistry
Volume267
Issue number18
StatePublished - 1992

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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