Ca(2+)‐independent change in phosphorylation of the myosin light chain during relaxation of ferret aorta by vasodilators.

Suematsu, Eiichi; Resnick, Moira S.; Morgan, Kathleen G.

doi:10.1113/jphysiol.1991.sp018697

Cited by 13 publications

(10 citation statements)

References 27 publications

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“…72 Normally, stimulation of GOJ inhibits adenylate cyclase; removal of inhibition by pertussis toxin would therefore permit the unopposed basal activity of adenylate cyclase and consequent accumulation of cyclic AMP (cAMP), an effect similar to that of papavarine, which is a phosphodiesterase inhibitor. Although it is disputed whether cAMP causes relaxation via a decrease in [Ca 2+ ]i 73 or by increasing the Ca 2+ requirement for force maintenance, 74 pertussis toxin nevertheless produced a vasodilator response, presumably through disinhibiting adenylate cyclase. 71 These data therefore suggest that the maintenance of myogenic tone is mediated at least in part by the tonic inhibition of adenylate cyclase.…”

Section: Guanine Nucleotide Regulatory Proteinsmentioning

confidence: 99%

Transduction mechanisms involved in the regulation of myogenic activity.

1994

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Vascular smooth muscle has the ability to exist in a state of maintained partial constriction. This state of partial activation is initiated and/or maintained by the mechanical effects of distending pressure acting on the vascular wall. The intrinsic ability of vascular smooth muscle to respond to these mechanical forces is referred to as the myogenic mechanism. Within the past decade the signaling mechanisms responsible for mechanotransduction of myogenic phenomena have been the focus of extensive research. Two areas of active investiga-T he intrinsic ability of vascular smooth muscle to maintain a partial state of contraction and to alter its state of contractile activation, either spontaneously or in response to changes in intravascular pressure, is commonly referred to as myogenic behavior. This behavior presents itself in several characteristic forms, including (1) myogenic tone (often referred to as basal, intrinsic, or spontaneous tone), the sustained contractile state intrinsic to vascular smooth muscle exhibited in the absence of neural or humoral influence; (2) the myogenic response, or the ability of vascular smooth muscle to constrict after an increase in intravascular pressure and, conversely, to dilate on lowering of intravascular pressure; and (3) vasomotion, the spontaneous, rhythmic oscillations in lumen diameter (see Johansson 1 for review). Although myogenic behavior has been reported in conduit arteries 2 and the facial vein, 3 ' 4 myogenic tone and myogenic responses are more prevalent in the resistance vasculature, in particular, within the microcirculation. In fact, detailed studies have shown that within a vascular network, relative myogenic responsiveness increases with decreasing arteriolar size. Use of the term myogenic itself implies that mechanical stimuli act directly on vascular smooth muscle cells to elicit contraction. However, more recent evidence has shown that the vascular endothelium can modulate force production by vascular smooth muscle by virtue of its ability to release both relaxing and contracting factors in response to chemical and mechanical stimuli.8 ' 9 Thus, endothelium-derived vasoactive agents may play a role in regulating myogenic behavior and in some cases 1013 may be responsible for pressure-dependent changes in vasoconstrictor activity previously ascribed

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Section: Guanine Nucleotide Regulatory Proteinsmentioning

confidence: 99%

Transduction mechanisms involved in the regulation of myogenic activity.

1994

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“…It is a calcium- and calmodulin-dependent enzyme and requires the calcium-calmodulin complex for its activity [Gallagher et al, 1997]. However, several studies suggest calcium- [Ozaki et al, 1987a,b; Suematsu et al, 1991; McFawn et al, 2003; Formigli et al, 2004] and MLCK-independent phosphorylation of MLC20 [Emmert et al, 2004]. Isometric contraction and MLC20 phosphorylation were also observed in embryo fibroblasts, which contain no detectable MLCK [Emmert et al, 2004].…”

Section: Introductionmentioning

confidence: 99%

MLCK‐independent phosphorylation of MLC20 and its regulation by MAP kinase pathway in human bladder smooth muscle cells

Deng¹,

Ding²,

Min³

et al. 2010

Cytoskeleton

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Myosins are a superfamily of actin-based molecular motor proteins, which hydrolyze ATP and generate various forms of eukaryotic motility and muscle contraction. Myosin light chain 20 (MLC20) is small ring around the neck region of heavy chain of myosins. Phosphorylation of MLC20 is thought to play a key role in regulation of smooth muscle contraction. Calcium- and calmodulin-dependent myosin light chain kinase (MLCK) is considered the primary regulator of MLC20 phosphorylation. However, several observations in smooth muscle contraction cannot be explained by the mode of phosphorylation. By performing a series of experiments in vitro and in vivo, we report here MLCK-independent MLC20 phosphorylation. Gene expression study reveals that expression of MLCK in smooth muscles is inconsistent with MLC20 phosphorylation at Ser19. None of inactivating calmodulin/MLCK, depriving of calcium and silencing MLCK expression by siRNA blocks effectively the phosphorylation of MLC20 at Ser19. In addition, by overexpressing active human MAP (mitogen-activated protein)-ERK kinase kinase-1 (MEKK1) and blocking its downstream messengers, we have demonstrated a new regulatory system of MLC phosphorylation via MEKK1, which downregulates Ser19 phosphorylation of MLC20 through its downstream molecules, p38, JNK, and ERK in human bladder smooth muscle cells.

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“…3,18,20 The difference could be due either to the difference in temperature or the difference in tissue or both. However, as previously seen for ferret aorta, phenylephrine increased LC20 phosphorylation levels ( Figure 6A) to a high level initially (43%) followed by a relatively rapid decline in phosphorylation levels, whereas the increase in contractile force was maintained ( Figure 6B).…”

Section: Shin Et Al Myosin Phosphatase Subunit Localizationmentioning

confidence: 99%

“…However, it has been known for some time that agonist-induced contractions can involve "Ca 2ϩ sensitization", 2 ie, increased force production at any given [Ca 2ϩ ]. One mechanism that has been suggested to explain Ca 2ϩ sensitization in cases where LC20 phosphorylation is also increased at any given [Ca 2ϩ ] 3 is inhibition of MP by signaling pathways. 4 MP is composed of 3 subunits: a catalytic subunit (PP1c), a large noncatalytic subunit (targeting subunit, MYPT1, M130), and a small noncatalytic subunit of unknown function (M20).…”

mentioning

confidence: 99%

Differential Association and Localization of Myosin Phosphatase Subunits During Agonist-Induced Signal Transduction in Smooth Muscle

Shin

Gallant

et al. 2002

Circulation Research

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Abstract-It has been known for some time that agonist-induced contractions of vascular smooth muscle are often associated with a sensitization of the contractile apparatus to intracellular Ca 2ϩ . One mechanism that has been suggested to explain Ca 2ϩ sensitization is inhibition of myosin phosphatase activity. In the present study, we tested the hypothesis that differential localization of the phosphatase might be associated with its inhibition. Quantitative confocal microscopy of freshly dissociated, fully contractile smooth muscle cells was used in parallel with measurements of myosin light chain and myosin phosphatase phosphorylation. The results indicate that, in the smooth muscle cells, the catalytic and targeting subunits of the phosphatase are dissociated from each other in an agonist-specific manner and that the dissociation is accompanied by a slower rate of myosin phosphorylation. Targeting of myosin phosphatase to the cell membrane precedes the dissociation of subunits and is associated with phosphorylation of the targeting subunit at a Rho-associated kinase (ROK) phosphorylation site. The phosphorylation and membrane translocation of the targeting subunit are inhibited by a ROK inhibitor. This dissociation of subunits may provide a mechanism for the decreased phosphatase activity of phosphorylated myosin phosphatase. (Circ Res. 2002;90:546-553.)

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Ca(2+)‐independent change in phosphorylation of the myosin light chain during relaxation of ferret aorta by vasodilators.

Cited by 13 publications

References 27 publications

Transduction mechanisms involved in the regulation of myogenic activity.

Transduction mechanisms involved in the regulation of myogenic activity.

MLCK‐independent phosphorylation of MLC20 and its regulation by MAP kinase pathway in human bladder smooth muscle cells

Differential Association and Localization of Myosin Phosphatase Subunits During Agonist-Induced Signal Transduction in Smooth Muscle

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