TY - JOUR
T1 - Signaling processes for initiating smooth muscle contraction upon neural stimulation
AU - Ding, Hai Lei
AU - Ryder, Jeffrey W.
AU - Stull, James T.
AU - Kamm, Kristine E.
PY - 2009/6/5
Y1 - 2009/6/5
N2 - 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.
AB - 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.
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U2 - 10.1074/jbc.M900888200
DO - 10.1074/jbc.M900888200
M3 - Article
C2 - 19349274
AN - SCOPUS:67650138614
SN - 0021-9258
VL - 284
SP - 15541
EP - 15548
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 23
ER -