GTP gamma S-dependent regulation of smooth muscle contractile elements

1992 ◽  
Vol 262 (2) ◽  
pp. C405-C410 ◽  
Author(s):  
Y. Kubota ◽  
M. Nomura ◽  
K. E. Kamm ◽  
M. C. Mumby ◽  
J. T. Stull
Keyword(s):  
Smooth Muscle ◽  
Light Chain ◽  
Protein Phosphatase ◽  
Myosin Light Chain Kinase ◽  
Myosin Light Chain ◽  
Kinase Activity ◽  
Tracheal Smooth Muscle ◽  
Proportional Increase ◽  
Gamma S ◽  
Muscle Contractile

Guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) increases the sensitivity of the contractile response to activation by Ca2+ in permeabilized tracheal smooth muscle. Increased tension was associated with a proportional increase in myosin light chain phosphorylation. The site of phosphorylation was determined to be serine-19, which corresponds to the site rapidly phosphorylated by myosin light chain kinase. GTP gamma S did not affect the contraction induced by the protein phosphatase inhibitor okadaic acid but did enhance contraction produced by Ca(2+)-independent myosin light chain kinase. In tracheal homogenates Ca(2+)-dependent myosin light chain kinase activity was not affected by GTP gamma S; however, dephosphorylation of 32P-labeled heavy meromyosin by phosphatase was inhibited. Thus GTP gamma S may increase the Ca2+ sensitivity of contractile elements in tracheal smooth muscle by inhibition of protein phosphatase activity toward myosin light chain.

Regulation of Myosin Light Chain Kinase Activity in Smooth Muscle

1995 ◽  
pp. 139-158 ◽  
Author(s):  
Kristine E. Kamm ◽  
Katherine Luby-Phelps ◽  
Malu G. Tansey ◽  
Patricia J. Gallagher ◽  
James T. Stull
Keyword(s):  
Smooth Muscle ◽  
Light Chain ◽  
Myosin Light Chain Kinase ◽  
Myosin Light Chain ◽  
Kinase Activity

Regulation of myosin light chain kinase: kinetic mechanism, autophosphorylation, and cooperative activation by Ca2+ and calmodulin

1994 ◽  
Vol 72 (11) ◽  
pp. 1368-1376 ◽  
Author(s):  
Apolinary Sobieszek
Keyword(s):  
Smooth Muscle ◽  
Light Chain ◽  
Myosin Light Chain Kinase ◽  
Myosin Light Chain ◽  
Kinase Activity ◽  
Kinetic Mechanism ◽  
Binding Stoichiometry ◽  
Myosin Interaction ◽  
Cooperative Activation ◽  
Fold Excess

Phosphorylation of the regulatory light chain of myosin catalyzed by myosin light-chain kinase (MLCK) is the key reaction in the regulation of actin–myosin interaction in smooth muscle. It is shown that this reaction is of an ordered type, whereby kinase first binds ATP and then the light chain, and following phosphate transfer, the phosphorylated light chain is released before ADP. The MLCK also phosphorylates itself, and this intramolecular autophosphorylation is Ca2+ and calmodulin (CaM) dependent. It has, however, no pronounced effect on the kinase activity or on its affinity for Ca2+ and CaM. With the aim of understanding the cooperativity of MLCK activation, the activity of the kinase was systematically measured as a function of different ligands involved. In these measurements the isolated light chain and intact filamentous myosin, as well as native actomyosin, were used as substrates. The activation of the kinase by Ca2+ was positively cooperative but only at relatively low CaM levels. The activation by CaM (at saturating Ca2+ levels) was also cooperative, even though noncooperative activation would be expected from the established 1:1 binding stoichiometry between CaM and the kinase. This cooperativity was shown to result from time-dependent changes in the MLCK that take place during incubation with Ca2+ and CaM before addition of ATP in phosphorylation assays. As a result, activity of the kinase as a function of its concentration at constant CaM was biphasic: there was optimum activity at a ratio of 1:1 CaM to kinase and almost complete inhibition of the activity at a three- to six-fold excess of the kinase over CaM. The modification required 10–15 min preincubation (with Ca2+ and CaM) and could be explained by a dimerization of the kinase, demonstrated by the use of a zero-length cross-linker.Key words: kinetic mechanism, autophosphorylation, calcium and calmodulin activation, cooperativity, myosin light chain kinase, smooth muscle.

scholarly journals Ontogenesis of myosin light chain kinase mRNA and protein content in guinea pig tracheal smooth muscle

2004 ◽  
Vol 38 (6) ◽  
pp. 456-464 ◽  
Author(s):  
Pasquale Chitano ◽  
Judith A. Voynow ◽  
Valeria Pozzato ◽  
Viviana Cantillana ◽  
Lauranell H. Burch ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Guinea Pig ◽  
Protein Content ◽  
Light Chain ◽  
Myosin Light Chain Kinase ◽  
Myosin Light Chain ◽  
Tracheal Smooth Muscle

Latch-bridge model in smooth muscle: [Ca2+]i can quantitatively predict stress

1990 ◽  
Vol 259 (2) ◽  
pp. C251-C257 ◽  
Author(s):  
C. M. Rembold ◽  
R. A. Murphy
Keyword(s):  
Smooth Muscle ◽  
Light Chain ◽  
Myosin Light Chain Kinase ◽  
Time Course ◽  
Myosin Light Chain ◽  
Kinase Activity ◽  
Force Production ◽  
Cross Bridge ◽  
Bridge Model ◽  
Latch State

Ca2+ concentration ([Ca2+])-dependent cross-bridge phosphorylation by myosin light chain kinase is postulated to be the primary regulator of stress development in smooth muscle. A four-state model of cross-bridge function, regulated only by [Ca2+]-dependent changes in myosin kinase activity, has been proposed to explain contraction and the latch state of smooth muscle (high force with reduced cross-bridge cycling and ATP consumption). A key test of this model is to determine whether changes in myoplasmic [Ca2+], per se, can quantitatively predict changes in myosin kinase activity, cross-bridge phosphorylation, and therefore force production. We find that changes in aequorin-estimated myoplasmic [Ca2+] can quantitatively predict the time course of phosphorylation and isometric stress production in response to stimulation with histamine and angiotensin II and during adenosine 3',5'-cyclic monophosphate-mediated relaxation when [Ca2+] is not changing rapidly. These results suggest that changes in myoplasmic [Ca2+] and activation of myosin light chain kinase may be sufficient to explain both contraction and relaxation of agonist stimulated swine carotid arterial smooth muscle.

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