Signaling processes for initiating smooth muscle contraction upon neural stimulation

Hai Lei Ding, Jeffrey W. Ryder, James T. Stull, Kristine E. Kamm

Research output: Contribution to journalArticlepeer-review

52 Scopus citations


Relationships among biochemical signaling processes involved in Ca2+/calmodulin (CaM)-dependent phosphorylation of smooth muscle myosin regulatory light chain (RLC) by myosin light chain kinase (MLCK) were determined. A genetically-encoded biosensor MLCK for measuring Ca2+- dependent-CaM binding and activation was expressed in smooth muscles of transgenic mice. We performed real-time evaluations of the relationships among [Ca2+]v̇MLCK activation, and contraction in urinary bladder smooth muscle strips neurally stimulated for 3 s. Latencies for the onset of [Ca2+]i and kinase activation were 55 ± 8 nd 65 ± 6 ms, respectively. Both increased with RLC phosphorylation at 100 ms, whereas force latency was 109 ± 3 MS. [CA2+]v̇kinase activation, and RLC phosphorylation responses were maximal by 1.2 s, whereas force increased more slowly to a maximal value at 3 s. A delayed temporal response between RLC phosphorylation and force is probably due to mechanical effects associated with elastic elements in the tissue. MLCK activation partially declined at 3 s of stimulation with no change in [Ca2+]i and also declined more rapidly than [Ca2+]i during relaxation. The apparent desensitization of MLCK to Ca2+ activation appears to be due to phosphorylation in its calmodulin binding segment. Phosphorylation of two myosin light chain phosphatase regulatory proteins (MYPT1 and CPI-17) or a protein implicated in strengthening membrane adhesion complexes for force transmission (paxillin) did not change during force development. Thus, neural stimulation leads to rapid increases in [Ca2+]v̇ MLCK activation, and RLC phosphorylation in phasic smooth muscle, showing a tightly coupled Ca2+ signaling complex as an elementary mechanism initiating contraction.

Original languageEnglish (US)
Pages (from-to)15541-15548
Number of pages8
JournalJournal of Biological Chemistry
Issue number23
StatePublished - Jun 5 2009

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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