Type II myosin regulatory light chain relieves auto-inhibition of myosin-heavy-chain function

2000 ◽  
Vol 2 (11) ◽  
pp. 855-858 ◽  
Author(s):  
Naweed I. Naqvi ◽  
Kelvin C. Y. Wong ◽  
Xie Tang ◽  
Mohan K. Balasubramanian
Keyword(s):  
Myosin Heavy Chain ◽  
Heavy Chain ◽  
Light Chain ◽  
Regulatory Light Chain ◽  
Myosin Regulatory Light Chain ◽  
Type Ii ◽  
Type Ii Myosin

Differential expression and effect of 1,25-dihydroxyvitamin D3 on myosin in arterial tree of rats

1995 ◽  
Vol 269 (2) ◽  
pp. C443-C450 ◽  
Author(s):  
K. Ishibashi ◽  
A. Evans ◽  
T. Shingu ◽  
K. Bian ◽  
R. D. Bukoski
Keyword(s):  
Smooth Muscle ◽  
Heavy Chain ◽  
Light Chain ◽  
Myosin Light Chain ◽  
Regulatory Light Chain ◽  
Myosin Regulatory Light Chain ◽  
Arterial Tree ◽  
Dihydroxyvitamin D3 ◽  
1,25 Dihydroxyvitamin D3 ◽  
Wistar Kyoto

The hypothesis that 1,25-dihydroxyvitamin D3 [1,25(OH)2D3, also known as calcitriol] modulates myosin expression in vascular smooth muscle was tested. Wistar-Kyoto or spontaneously hypertensive rats given intraperitoneal injections of 25 ng 1,25(OH)2D3/100 g body weight for varying periods of time showed a greater than twofold increase in aortic mRNA encoding the myosin regulatory light chain relative to 18S rRNA (P < 0.05). 1,25(OH)2D3 administration to Wistar rats caused a significant increase in the aortic content of total myosin regulatory light chain and total myosin heavy chain. The increase in myosin light chain was the result of a specific increase in expression of its smooth muscle isoform [control = 65.2 +/- 3.4% vs. 1,25(OH)2D3 = 78.7 +/- 3.6%, P = 0.020]. 1,25(OH)2D3 had no effect on total myosin light chain or heavy chain in the superior mesenteric artery. The hormone did, however, increase the proportion of the smooth muscle isoform of the light chain in this vessel [control = 81.4 +/- 2.6% vs. 1,25(OH)2D3 = 88.8 +/- 2.1%, P = 0.048]. In branch II and III mesenteric resistance arteries, 1,25(OH)2D3 significantly increased the active stress response to 10 mumol/l norepinephrine but was without effect on total myosin light chain or heavy chain content or on the relative expression of the myosin light chain isoforms [control = 94.0 +/- 1.4% vs. 1,25(OH)2D3 = 95.8 +/- 1.1%, P = 0.33].(ABSTRACT TRUNCATED AT 250 WORDS)

Relationships between maximal strength, muscle size, and myosin heavy chain isoform composition and postactivation potentiation

2016 ◽  
Vol 41 (5) ◽  
pp. 491-497 ◽  
Author(s):  
Laurent B. Seitz ◽  
Gabriel S. Trajano ◽  
G. Gregory Haff ◽  
Charles C.L.S. Dumke ◽  
James J. Tufano ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Myosin Heavy Chain ◽  
Heavy Chain ◽  
Human Skeletal Muscle ◽  
Knee Extensor ◽  
Type Ii ◽  
Postactivation Potentiation ◽  
Test Protocol ◽  
Extensor Torque ◽  
Type Ii Myosin

The purpose of this study was to examine the relationships between maximal voluntary postactivation potentiation (PAP) and maximal knee extensor torque, quadriceps cross-sectional area (CSA) and volume, and type II myosin heavy chain (MHC) isoform percentage in human skeletal muscle. Thirteen resistance-trained men completed a test protocol consisting of 2 isokinetic knee extensions at 180°·s–1 performed before and 1, 4, 7, and 10 min after the completion of 4 maximal knee extensions at 60°·s–1 (i.e., a conditioning activity (CA)). Magnetic resonance imaging and muscle microbiopsy procedures were completed on separate days to assess quadriceps CSA and volume and MHC isoform content. Maximal voluntary PAP response was assessed as the ratio of the highest knee extensor torques measured before and after the CA. There were large to very large correlations between maximal voluntary PAP response and maximal knee extensor torque (r = 0.62) and quadriceps CSA (r = 0.68) and volume (r = 0.63). Nonetheless, these correlations were not statistically significant after adjusting for the influence of type II MHC percentage using partial correlation analysis. By contrast, the strongest correlation was observed for type II MHC percentage (r = 0.77), and this correlation remained significant after adjusting for the other variables. Maximal voluntary PAP response is strongly correlated with maximal knee extensor torque and quadriceps CSA and volume, but is mostly clearly associated with the type II myosin isoform percentage in human skeletal muscle.

scholarly journals Regulatory light chain phosphorylation augments length-dependent contraction in PTU-treated rats

2018 ◽  
Vol 151 (1) ◽  
pp. 66-76 ◽  
Author(s):  
Jason J. Breithaupt ◽  
Hannah C. Pulcastro ◽  
Peter O. Awinda ◽  
David C. DeWitt ◽  
Bertrand C.W. Tanner
Keyword(s):  
Myosin Heavy Chain ◽  
Heavy Chain ◽  
Light Chain ◽  
Myosin Heavy Chain Isoforms ◽  
Regulatory Light Chain ◽  
Cardiac Myosin ◽  
Myosin Heavy Chain Isoform ◽  
Cross Bridge ◽  
Detachment Rate ◽  
Length Dependent Activation

Force production by actin–myosin cross-bridges in cardiac muscle is regulated by thin-filament proteins and sarcomere length (SL) throughout the heartbeat. Prior work has shown that myosin regulatory light chain (RLC), which binds to the neck of myosin heavy chain, increases cardiac contractility when phosphorylated. We recently showed that cross-bridge kinetics slow with increasing SLs, and that RLC phosphorylation amplifies this effect, using skinned rat myocardial strips predominantly composed of the faster α-cardiac myosin heavy chain isoform. In the present study, to assess how RLC phosphorylation influences length-dependent myosin function as myosin motor speed varies, we used a propylthiouracil (PTU) diet to induce &gt;95% expression of the slower β-myosin heavy chain isoform in rat cardiac ventricles. We measured the effect of RLC phosphorylation on Ca2+-activated isometric contraction and myosin cross-bridge kinetics (via stochastic length perturbation analysis) in skinned rat papillary muscle strips at 1.9- and 2.2-µm SL. Maximum tension and Ca2+ sensitivity increased with SL, and RLC phosphorylation augmented this response at 2.2-µm SL. Subtle increases in viscoelastic myocardial stiffness occurred with RLC phosphorylation at 2.2-µm SL, but not at 1.9-µm SL, thereby suggesting that RLC phosphorylation increases β-myosin heavy chain binding or stiffness at longer SLs. The cross-bridge detachment rate slowed as SL increased, providing a potential mechanism for prolonged cross-bridge attachment to augment length-dependent activation of contraction at longer SLs. Length-dependent slowing of β-myosin heavy chain detachment rate was not affected by RLC phosphorylation. Together with our previous studies, these data suggest that both α- and β-myosin heavy chain isoforms show a length-dependent activation response and prolonged myosin attachment as SL increases in rat myocardial strips, and that RLC phosphorylation augments length-dependent activation at longer SLs. In comparing cardiac isoforms, however, we found that β-myosin heavy chain consistently showed greater length-dependent sensitivity than α-myosin heavy chain. Our work suggests that RLC phosphorylation is a vital contributor to the regulation of myocardial contractility in both cardiac myosin heavy chain isoforms.

scholarly journals Type II Myosin Heavy Chain Encoded by the myo2 Gene Composes the Contractile Ring during Cytokinesis in Schizosaccharomyces pombe

1997 ◽  
Vol 137 (6) ◽  
pp. 1309-1319 ◽  
Author(s):  
Chikako Kitayama ◽  
Asako Sugimoto ◽  
Masayuki Yamamoto
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Myosin Heavy Chain ◽  
Heavy Chain ◽  
Coiled Coil ◽  
Yeast Cells ◽  
Type Ii ◽  
Contractile Ring ◽  
Iq Motif ◽  
Multinucleated Cells ◽  
Type Ii Myosin

We cloned the myo2 gene of Schizosaccharomyces pombe, which encodes a type II myosin heavy chain, by virtue of its ability to promote diploidization in fission yeast cells. The myo2 gene encodes 1,526 amino acids in a single open reading frame. Myo2p shows homology to the head domains and the coiledcoil tail of the conventional type II myosin heavy chain and carries putative binding sites for ATP and actin. It also carries the IQ motif, which is a presumed binding site for the myosin light chain. However, Myo2p apparently carries only one IQ motif, while its counterparts in other species have two. There are nine proline residues, which should break α-helix, in the COOH-terminal coiled-coil region of Myo2p. Thus, Myo2p is rather unusual as a type II myosin heavy chain. Disruption of myo2 inhibited cell proliferation. myo2Δ cells showed normal punctate distribution of interphase actin, but they produced irregular actin rings and septa and were impaired in cell separation. Overproduction of Myo2p was also lethal, apparently blocking actin relocation. Nuclear division proceeded without actin ring formation and cytokinesis in cells overexpressing Myo2p, giving rise to multinucleated cells with dumbbell morphology. Analysis using tagged Myo2p revealed that Myo2p colocalizes with actin in the contractile ring, suggesting that Myo2p is a component of the ring and responsible for its contraction. Furthermore, genetic evidence suggested that the acto–myosin system may interact with the Ras pathway, which regulates mating and the maintenance of cell morphology in S. pombe.

Identification of Myo3, a second type-II myosin heavy chain in the fission yeast Schizosaccharomyces pombe

FEBS Letters ◽  
1997 ◽  
Vol 420 (2-3) ◽  
pp. 161-166 ◽  
Author(s):  
Fumio Motegi ◽  
Kentaro Nakano ◽  
Chikako Kitayama ◽  
Masayuki Yamamoto ◽  
Issei Mabuchi
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Myosin Heavy Chain ◽  
Fission Yeast ◽  
Heavy Chain ◽  
Type Ii ◽  
Type Ii Myosin
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