scholarly journals Effect of lithium on smooth muscle contraction and phosphorylation of myosin light chain by MLCK

2010 ◽  
pp. 919-926
Author(s):  
ZY Tang ◽  
ZN Liu ◽  
L Fu ◽  
DP Chen ◽  
QD Ai ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Atpase Activity ◽  
Muscle Contraction ◽  
Light Chain ◽  
Myosin Light Chain ◽  
Contractile Activity ◽  
Smooth Muscle Contraction ◽  
Time Dependent ◽  
Dependent Manner ◽  
Myosin Phosphorylation

The aims of our study were to investigate into the effect of lithium on smooth muscle contraction and phosphorylation of myosin light chain (MLC20) by MLCK and to find out the clue of its mechanism. Isolated rabbit duodenum smooth muscle strips were used to study the effects of lithium on their contractile activity under the condition of Krebs’ solution by means of HW400S constant temperature smooth muscle trough. Myosin and MLCK were purified from the chicken gizzard smooth muscle. Myosin phosphorylation was determined by Glycerol-PAGE, myosin Mg2+-ATPase activity was measured by Pi liberation method. Lithium (10-40 mM) inhibited the contraction in duodenum in a dose-related and time-dependent manner. Lithium could also inhibit the extent of myosin phosphorylation in a dose-related and time-dependent manner, whereas it inhibited Mg2+-ATPase activity in a dose-related manner. Lithium inhibited smooth muscle contraction by inhibition of myosin phosphorylation and Mg2+-ATPase activity.

Calcium-dependent mechanisms of regulation of smooth muscle contraction

1991 ◽  
Vol 69 (12) ◽  
pp. 771-800 ◽  
Author(s):  
Michael P. Walsh
Keyword(s):  
Smooth Muscle ◽  
Muscle Contraction ◽  
Light Chain ◽  
Myosin Light Chain Kinase ◽  
Myosin Light Chain ◽  
Binding Protein ◽  
Smooth Muscle Contraction ◽  
Light Chains ◽  
Contractile State ◽  
Calmodulin Binding

The contractile state of smooth muscle is regulated primarily by the sarcoplasmic (cytosolic) free Ca2+ concentration. A variety of stimuli that induce smooth muscle contraction (e.g., membrane depolarization, α-adrenergic and muscarinic agonists) trigger an increase in sarcoplasmic free [Ca2+] from resting levels of 120–270 to 500–700 nM. At the elevated [Ca2+], Ca2+ binds to calmodulin, the ubiquitous and multifunctional Ca2+-binding protein. The interaction of Ca2+ with CaM induces a conformational change in the Ca2+-binding protein with exposure of a site(s) of interaction with target proteins, the most important of which in the context of smooth muscle contraction is the enzyme myosin light chain kinase. The interaction of calmodulin with myosin light chain kinase results in activation of the kinase that catalyzes phosphorylation of myosin at serine-19 of each of the two 20-kDa light chains (native myosin is a hexamer composed of two heavy chains (230 kDa each) and two pairs of light chains (one pair of 20 kDa each and the other pair of 17 kDa each)). This simple phosphorylation reaction triggers cycling of myosin cross-bridges along actin filaments and the development of force. Relaxation of the muscle follows removal of Ca2+ from the sarcoplasm, whereupon calmodulin dissociates from myosin light chain kinase regenerating the inactive kinase; myosin is dephosphorylated by myosin light chain phosphatase(s), whereupon it dissociates and remains detached from the actin filament and the muscle relaxes. A substantial body of evidence has been accumulated in support of this central role of myosin phosphorylation–dephosphorylation in the regulation of smooth muscle contraction. However, a wide range of physiological and biochemical studies supports the existence of additional, secondary Ca2+-dependent mechanisms that can modulate or fine-tune the contractile state of the smooth muscle cell. Three such mechanisms have emerged: (i) the actin-, tropomyosin-, and calmodulin-binding protein, calponin; (ii) the actin-, myosin-, tropomyosin-, and calmodulin-binding protein, caldesmon; and (iii) the Ca2+- and phospholipid-dependent protein kinase (protein kinase C).Key words: smooth muscle, Ca2+, myosin phosphorylation, regulation of contraction.

Activation of smooth muscle contraction: relation between myosin phosphorylation and stiffness

Science ◽  
1986 ◽  
Vol 232 (4746) ◽  
pp. 80-82 ◽  
Author(s):  
KE Kamm ◽  
JT Stull
Keyword(s):  
Smooth Muscle ◽  
Light Chain ◽  
Myosin Light Chain ◽  
Myosin Head ◽  
Isometric Force ◽  
Smooth Muscle Contraction ◽  
Myosin Phosphorylation ◽  
First Order ◽  
Cooperative Process ◽  
Pseudo First Order

Contraction and myosin light-chain phosphorylation were measured in electrically stimulated tracheal smooth muscle. Latencies for the onset of force, stiffness, and light-chain phosphorylation were 500 milliseconds. Myosin light chain was phosphorylated from 0.04 to 0.80 mole of phosphate per mole of light chain with a pseudo-first-order rate of 1.1 per second with no evidence of an ordered or negatively cooperative process. Following the period of latency, stiffness increased with phosphorylation and both increased more rapidly than isometric force. The linear relation between stiffness and phosphorylation during activation suggests independent attachment of each myosin head upon phosphorylation.

Regulation of vascular smooth muscle contraction: myosin light chain phosphorylation dependent and independent pathways

1994 ◽  
Vol 72 (11) ◽  
pp. 1386-1391 ◽  
Author(s):  
Yawen Zhang ◽  
Suzanne Moreland ◽  
Robert S. Moreland
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Muscle Contraction ◽  
Light Chain ◽  
Myosin Light Chain ◽  
Smooth Muscle Contraction ◽  
Mitogen Activated Protein ◽  
Vascular Smooth Muscle Contraction ◽  
Triton X ◽  
Mlc Phosphorylation

Ca2+-dependent myosin light chain (MLC) phosphorylation is an important step in the initiation of smooth muscle contraction. However, MLC phosphorylation alone cannot account for all aspects of contractile regulation, suggesting the involvement of other elements. In this article we present evidence obtained from Triton X-100 detergent skinned and intact tissue which demonstrates that vascular smooth muscle contraction can be initiated by a Ca2+-dependent mechanism that does not require prior MLC phosphorylation. We show that Ca2+ can initiate contractions supported by cytidine triphosphate (CTP) and that these contractions are inhibited by calmodulin antagonists, suggesting a Ca2+–calmodulin dependence of force distinct from that for MLC phosphorylation. Evidence is presented to demonstrate that carotid medial fibers contain a mitogen-activated protein (MAP) kinase which is activated by Ca2+ and may catalyze caldesmon phosphorylation. Based in part on our results and those of other investigators, we propose that direct Ca2+–calmodulin binding to caldesmon or phosphorylation of caldesmon by a Ca2+-dependent MAP kinase disinhibits caldesmon. Disinhibition of caldesmon allows an inherent basal level of actin-activated myosin ATPase activity to be expressed. The result is the slow development of force.Key words: mitogen-activated protein kinase, caldesmon, Triton X-100, detergent-skinned fibers, cytidine triphosphate, calmodulin.

scholarly journals Rho-associated kinase plays a role in rabbit urethral smooth muscle contraction, but not via enhanced myosin light chain phosphorylation

2011 ◽  
Vol 300 (1) ◽  
pp. F73-F85 ◽  
Author(s):  
Michael P. Walsh ◽  
Keith Thornbury ◽  
William C. Cole ◽  
Gerard Sergeant ◽  
Mark Hollywood ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Muscle Contraction ◽  
Light Chain ◽  
Actin Polymerization ◽  
Myosin Light Chain ◽  
Smooth Muscle Contraction ◽  
Regulatory Light Chains ◽  
Kinase C ◽  
Protein Kinase C Inhibitor ◽  
Urethral Smooth Muscle

The involvement of Rho-associated kinase (ROK) in activation of rabbit urethral smooth muscle contraction was investigated by examining the effects of two structurally distinct inhibitors of ROK, Y27632 and H1152, on the contractile response to electric field stimulation, membrane depolarization with KCl, and α1-adrenoceptor stimulation with phenylephrine. Both compounds inhibited contractions elicited by all three stimuli. The protein kinase C inhibitor GF109203X, on the other hand, had no effect. Urethral smooth muscle strips were analyzed for phosphorylation of three potential direct or indirect substrates of ROK: 1) myosin regulatory light chains (LC20) at S19, 2) the myosin-targeting subunit of myosin light chain phosphatase (MYPT1) at T697 and T855, and 3) cofilin at S3. The following results were obtained: 1) under resting tension, LC20 was phosphorylated to 0.65 ± 0.02 mol Pi/mol LC20 ( n = 21) at S19; 2) LC20 phosphorylation did not change in response to KCl or phenylephrine; 3) ROK inhibition had no effect on LC20 phosphorylation in the absence or presence of contractile stimuli; 4) under resting conditions, MYPT1 was partially phosphorylated at T697 and T855 and cofilin at S3; 5) phosphorylation of MYPT1 and cofilin was unaffected by KCl or phenylephrine; and 6) KCl- and phenylephrine-induced contraction-relaxation cycles did not correlate with actin polymerization-depolymerization. We conclude that ROK plays an important role in urethral smooth muscle contraction, but not via inhibition of MLCP or polymerization of actin.

Blebbistatin, a myosin II inhibitor, suppresses contraction and disrupts contractile filaments organization of skinned taenia cecum from guinea pig

2010 ◽  
Vol 298 (5) ◽  
pp. C1118-C1126 ◽  
Author(s):  
Masaru Watanabe ◽  
Masatoshi Yumoto ◽  
Hideyuki Tanaka ◽  
Hon Hui Wang ◽  
Takeshi Katayama ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Guinea Pig ◽  
Muscle Contraction ◽  
Light Chain ◽  
Myosin Light Chain ◽  
Myosin Ii ◽  
Smooth Muscle Contraction ◽  
Myosin Light Chain Phosphorylation ◽  
Thin Filaments ◽  
Tension Development

To explore the precise mechanisms of the inhibitory effects of blebbistatin, a potent inhibitor of myosin II, on smooth muscle contraction, we studied the blebbistatin effects on the mechanical properties and the structure of contractile filaments of skinned (cell membrane permeabilized) preparations from guinea pig taenia cecum. Blebbistatin at 10 μM or higher suppressed Ca2+-induced tension development at any given Ca2+ concentration but had little effects on the Ca2+-induced myosin light chain phosphorylation. Blebbistatin also suppressed the 10 and 2.75 mM Mg2+-induced, “myosin light chain phosphorylation-independent” tension development at more than 10 μM. Furthermore, blebbistatin induced conformational change of smooth muscle myosin (SMM) and disrupted arrangement of SMM and thin filaments, resulting in inhibition of actin-SMM interaction irrespective of activation with Ca2+. In addition, blebbistatin partially inhibited Mg2+-ATPase activity of native actomyosin from guinea pig taenia cecum at around 10 μM. These results suggested that blebbistatin suppressed skinned smooth muscle contraction through disruption of structure of SMM by the agent.

scholarly journals A Calponin Peptide Enhances Ca2+Sensitivity of Smooth Muscle Contraction without Affecting Myosin Light Chain Phosphorylation

1995 ◽  
Vol 270 (35) ◽  
pp. 20400-20403 ◽  
Author(s):  
Takeo Itoh ◽  
Akito Suzuki ◽  
Yoshimasa Watanabe ◽  
Terumasa Mino ◽  
Michiko Naka ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Muscle Contraction ◽  
Light Chain ◽  
Myosin Light Chain ◽  
Smooth Muscle Contraction ◽  
Myosin Light Chain Phosphorylation

scholarly journals Inhibition of smooth-muscle myosin-light-chain phosphatase by Ruthenium Red

2000 ◽  
Vol 349 (3) ◽  
pp. 797-804 ◽  
Author(s):  
Aki YAMADA ◽  
Osamu SATO ◽  
Minoru WATANABE ◽  
Michael P. WALSH ◽  
Yasuo OGAWA ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Light Chain ◽  
Myosin Light Chain ◽  
Smooth Muscles ◽  
Direct Interaction ◽  
Smooth Muscle Contraction ◽  
Ruthenium Red ◽  
Dependent Manner ◽  
Myosin Light Chain Phosphatase ◽  
Concentration Dependent Manner

Ruthenium Red (RuR) is widely used as an inhibitor of ryanodine receptor Ca2+ release channels, but has additional effects such as the induction of Ca2+ sensitization of contraction of permeabilized smooth muscles. To address the mechanism underlying this process, we examined the effects of RuR on contractility in permeabilized guinea-pig ileum and on the activity of myosin-light-chain phosphatase (MP). RuR increased the force at submaximal [Ca2+] (pCa 6.3) approx. 4-fold. This effect was not observed after thiophosphorylation of MP. RuR also seemed capable of preventing the thiophosphorylation of MP, suggesting a direct interaction of RuR with MP. Consistent with this possibility, smooth-muscle MP was inhibited by RuR in a concentration-dependent manner (IC50 23µM). Exogenous calmodulin significantly increased RuR-induced contraction at pCa 6.3 but had little effect on contraction induced by microcystin at this [Ca2+]. Ca2+-independent contraction was induced by RuR (EC50 843µM) and by microcystin (EC50 59nM) but the maximal force induced by RuR was smaller than that induced by microcystin. The addition of 300µM RuR enhanced the contraction induced by 30nM microcystin but markedly decreased that induced by 1µM microcystin. Such a dual action of RuR on microcystin-induced effects was not observed in experiments using purified MP. We conclude that the RuR-induced Ca2+ sensitization of smooth-muscle contraction is due to the direct inhibition of MP by RuR.

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