Nonmuscle myosin is regulated during smooth muscle contraction

Samantha L. Yuen, Ozgur Ogut, Frank V. Brozovich

Research output: Contribution to journalArticlepeer-review

47 Scopus citations


The participation of nonmuscle myosin in force maintenance is controversial. Furthermore, its regulation is difficult to examine in a cellular context, as the light chains of smooth muscle and nonmuscle myosin comigrate under native and denaturing electrophoresis techniques. Therefore, the regulatory light chains of smooth muscle myosin (SM-RLC) and nonmuscle myosin (NM-RLC) were purified, and these proteins were resolved by isoelectric focusing. Using this method, intact mouse aortic smooth muscle homogenates demonstrated four distinct RLC isoelectric variants. These spots were identified as phosphorylated NM-RLC (most acidic), nonphosphorylated NM-RLC, phosphorylated SM-RLC, and nonphosphorylated SM-RLC (most basic). During smooth muscle activation, NM-RLC phosphorylation increased. During depolarization, the increase in NM-RLC phosphorylation was unaffected by inhibition of either Rho kinase or PKC. However, inhibition of Rho kinase blocked the angiotensin II-induced increase in NM-RLC phosphorylation. Additionally, force for angiotensin II stimulation of aortic smooth muscle from heterozygous nonmuscle myosin IIB knockout mice was significantly less than that of wild-type littermates, suggesting that, in smooth muscle, activation of nonmuscle myosin is important for force maintenance. The data also demonstrate that, in smooth muscle, the activation of nonmuscle myosin is regulated by Ca 2+-calmodulin-activated myosin light chain kinase during depolarization and a Rho kinase-dependent pathway during agonist stimulation.

Original languageEnglish (US)
Pages (from-to)H191-H199
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Issue number1
StatePublished - Jul 2009


  • Agonist
  • Depolarization
  • Myosin light chain kinase
  • Rho kinase

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)


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