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Signaling processes for initiating smooth muscle contraction
Author(s) -
Ding HaiLei,
Ryder Jeffrey W.,
Stull James T.,
Kamm Kristine E.
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.1181.7
Subject(s) - myosin light chain kinase , phosphorylation , myosin light chain phosphatase , calmodulin , förster resonance energy transfer , myosin , chemistry , microbiology and biotechnology , biophysics , muscle contraction , kinase , contraction (grammar) , biology , biochemistry , anatomy , endocrinology , fluorescence , enzyme , physics , quantum mechanics
Relationships among signaling processes involved in Ca 2+ /calmodulin‐dependent phosphorylation of myosin regulatory light chain (RLC) by myosin light chain kinase (MLCK) were determined to provide insights into cellular mechanisms for initiating smooth muscle contraction. A genetically encoded MLCK biosensor showing Ca 2+ ‐dependent CaM binding by decreased fluorescence resonance energy transfer (FRET) coincident with increased kinase activity was expressed in smooth muscles of transgenic mice. Isolated bladder smooth muscle tissues were neurally stimulated for 3 s. The latencies for the onset of [Ca 2+ ] i and FRET were 55±8 and 65±6 ms, respectively. Both increased along with RLC phosphorylation at 100 ms while force latency was 109±3 ms. Increases in [Ca 2+ ] i , FRET and RLC phosphorylation were maximal by 1.2 s whereas force increased more slowly to a maximal value at 3 s. Phosphorylation of two myosin RLC phosphatase regulatory proteins (MYPT1 and CPI‐17) did not change during the initial contraction phase. Thus, increases in [Ca 2+ ] i lead to a rapid MLCK activation and RLC phosphorylation showing a tightly coupled signaling complex. The delayed temporal response between RLC phosphorylation and force may be due to mechanical effects associated with myosin cross bridge attachment and expression of force through series elastic elements in the tissue. This study was supported by NIH Grant HL026043.