scholarly journals Filament evanescence of myosin II and smooth muscle function

2021 ◽  
Vol 153 (3) ◽  
Author(s):  
Lu Wang ◽  
Pasquale Chitano ◽  
Chun Y. Seow
Keyword(s):  
Smooth Muscle ◽  
Muscle Function ◽  
Molecular Mechanisms ◽  
Striated Muscle ◽  
Myosin Ii ◽  
Length Distribution ◽  
Myosin Filament ◽  
New Paradigm ◽  
Smooth Muscle Function ◽  
Myosin Filaments

Smooth muscle is an integral part of hollow organs. Many of them are constantly subjected to mechanical forces that alter organ shape and modify the properties of smooth muscle. To understand the molecular mechanisms underlying smooth muscle function in its dynamic mechanical environment, a new paradigm has emerged that depicts evanescence of myosin filaments as a key mechanism for the muscle’s adaptation to external forces in order to maintain optimal contractility. Unlike the bipolar myosin filaments of striated muscle, the side-polar filaments of smooth muscle appear to be less stable, capable of changing their lengths through polymerization and depolymerization (i.e., evanescence). In this review, we summarize accumulated knowledge on the structure and mechanism of filament formation of myosin II and on the influence of ionic strength, pH, ATP, myosin regulatory light chain phosphorylation, and mechanical perturbation on myosin filament stability. We discuss the scenario of intracellular pools of monomeric and filamentous myosin, length distribution of myosin filaments, and the regulatory mechanisms of filament lability in contraction and relaxation of smooth muscle. Based on recent findings, we suggest that filament evanescence is one of the fundamental mechanisms underlying smooth muscle’s ability to adapt to the external environment and maintain optimal function. Finally, we briefly discuss how increased ROCK protein expression in asthma may lead to altered myosin filament stability, which may explain the lack of deep-inspiration–induced bronchodilation and bronchoprotection in asthma.

scholarly journals Functions of Muscarinic Receptor Subtypes in Gastrointestinal Smooth Muscle: A Review of Studies with Receptor-Knockout Mice

2021 ◽  
Vol 22 (2) ◽  
pp. 926
Author(s):  
Yasuyuki Tanahashi ◽  
Seiichi Komori ◽  
Hayato Matsuyama ◽  
Takio Kitazawa ◽  
Toshihiro Unno
Keyword(s):  
Smooth Muscle ◽  
Knockout Mice ◽  
Muscle Function ◽  
Molecular Mechanisms ◽  
Muscarinic Acetylcholine Receptors ◽  
Receptor Subtype ◽  
Receptor Subtypes ◽  
Gastrointestinal Smooth Muscle ◽  
Subtype Selectivity ◽  
Smooth Muscle Function

Parasympathetic signalling via muscarinic acetylcholine receptors (mAChRs) regulates gastrointestinal smooth muscle function. In most instances, the mAChR population in smooth muscle consists mainly of M2 and M3 subtypes in a roughly 80% to 20% mixture. Stimulation of these mAChRs triggers a complex array of biochemical and electrical events in the cell via associated G proteins, leading to smooth muscle contraction and facilitating gastrointestinal motility. Major signalling events induced by mAChRs include adenylyl cyclase inhibition, phosphoinositide hydrolysis, intracellular Ca2+ mobilisation, myofilament Ca2+ sensitisation, generation of non-selective cationic and chloride currents, K+ current modulation, inhibition or potentiation of voltage-dependent Ca2+ currents and membrane depolarisation. A lack of ligands with a high degree of receptor subtype selectivity and the frequent contribution of multiple receptor subtypes to responses in the same cell type have hampered studies on the signal transduction mechanisms and functions of individual mAChR subtypes. Therefore, novel strategies such as genetic manipulation are required to elucidate both the contributions of specific AChR subtypes to smooth muscle function and the underlying molecular mechanisms. In this article, we review recent studies on muscarinic function in gastrointestinal smooth muscle using mAChR subtype-knockout mice.

scholarly journals Myosin filament structure in vertebrate smooth muscle.

1996 ◽  
Vol 134 (1) ◽  
pp. 53-66 ◽  
Author(s):  
J Q Xu ◽  
B A Harder ◽  
P Uman ◽  
R Craig
Keyword(s):  
Smooth Muscle ◽  
Striated Muscle ◽  
Smooth Muscles ◽  
Helical Structure ◽  
Structure Characteristic ◽  
Myosin Filament ◽  
Filament Structure ◽  
Myosin Filaments ◽  
Intact Muscle

The in vivo structure of the myosin filaments in vertebrate smooth muscle is unknown. Evidence from purified smooth muscle myosin and from some studies of intact smooth muscle suggests that they may have a nonhelical, side-polar arrangement of crossbridges. However, the bipolar, helical structure characteristic of myosin filaments in striated muscle has not been disproved for smooth muscle. We have used EM to investigate this question in a functionally diverse group of smooth muscles (from the vascular, gastrointestinal, reproductive, and visual systems) from mammalian, amphibian, and avian species. Intact muscle under physiological conditions, rapidly frozen and then freeze substituted, shows many myosin filaments with a square backbone in transverse profile. Transverse sections of fixed, chemically skinned muscles also show square backbones and, in addition, reveal projections (crossbridges) on only two opposite sides of the square. Filaments gently isolated from skinned smooth muscles and observed by negative staining show crossbridges with a 14.5-nm repeat projecting in opposite directions on opposite sides of the filament. Such filaments subjected to low ionic strength conditions show bare filament ends and an antiparallel arrangement of myosin tails along the length of the filament. All of these observations are consistent with a side-polar structure and argue against a bipolar, helical crossbridge arrangement. We conclude that myosin filaments in all smooth muscles, regardless of function, are likely to be side-polar. Such a structure could be an important factor in the ability of smooth muscles to contract by large amounts.

SMALL BOWEL ISCHEMIA/REPERFUSION (II/R) ALTERS COLONIC SMOOTH MUSCLE FUNCTION.

Shock ◽  
1998 ◽  
Vol 9 (Supplement) ◽  
pp. 13
Author(s):  
DT Dempsey ◽  
BS Myers ◽  
JP Ryan ◽  
J Carroll ◽  
SI Myers
Keyword(s):  
Smooth Muscle ◽  
Small Bowel ◽  
Muscle Function ◽  
Ischemia Reperfusion ◽  
Bowel Ischemia ◽  
Smooth Muscle Function

Effect of Flush-Perfusion on Vascular Endothelial and Smooth Muscle Function

1997 ◽  
Vol 64 (4) ◽  
pp. 1075-1081 ◽  
Author(s):  
Richard Ingemansson ◽  
Algimantas Budrikis ◽  
Ramunas Bolys ◽  
Trygve Sjöberg ◽  
Stig Steen
Keyword(s):  
Smooth Muscle ◽  
Muscle Function ◽  
Vascular Endothelial ◽  
Smooth Muscle Function

scholarly journals Effects of Scleroderma Antibodies and Pooled Human Immunoglobulin on Anal Sphincter and Colonic Smooth Muscle Function

2012 ◽  
Vol 143 (5) ◽  
pp. 1308-1318 ◽  
Author(s):  
Jagmohan Singh ◽  
Sidney Cohen ◽  
Vaibhav Mehendiratta ◽  
Fabian Mendoza ◽  
Sergio A. Jimenez ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Anal Sphincter ◽  
Muscle Function ◽  
Human Immunoglobulin ◽  
Smooth Muscle Function

scholarly journals Fundamental Roles of Axial Stretch in Isometric and Isobaric Evaluations of Vascular Contractility

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
Alexander W. Caulk ◽  
Jay D. Humphrey ◽  
Sae-Il Murtada
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Muscle Function ◽  
Contractile Function ◽  
Contractile Activity ◽  
Comparison Of Methods ◽  
Axial Stretch ◽  
Smooth Muscle Function ◽  
In Vivo Loading

Vascular smooth muscle cells (VSMCs) can regulate arterial mechanics via contractile activity in response to changing mechanical and chemical signals. Contractility is traditionally evaluated via uniaxial isometric testing of isolated rings despite the in vivo environment being very different. Most blood vessels maintain a locally preferred value of in vivo axial stretch while subjected to changes in distending pressure, but both of these phenomena are obscured in uniaxial isometric testing. Few studies have rigorously analyzed the role of in vivo loading conditions in smooth muscle function. Thus, we evaluated effects of uniaxial versus biaxial deformations on smooth muscle contractility by stimulating two regions of the mouse aorta with different vasoconstrictors using one of three testing protocols: (i) uniaxial isometric testing, (ii) biaxial isometric testing, and (iii) axially isometric plus isobaric testing. Comparison of methods (i) and (ii) revealed increased sensitivity and contractile capacity to potassium chloride and phenylephrine (PE) with biaxial isometric testing, and comparison of methods (ii) and (iii) revealed a further increase in contractile capacity with isometric plus isobaric testing. Importantly, regional differences in estimated in vivo axial stretch suggest locally distinct optimal biaxial configurations for achieving maximal smooth muscle contraction, which can only be revealed with biaxial testing. Such differences highlight the importance of considering in vivo loading and geometric configurations when evaluating smooth muscle function. Given the physiologic relevance of axial extension and luminal pressurization, we submit that, when possible, axially isometric plus isobaric testing should be employed to evaluate vascular smooth muscle contractile function.

scholarly journals Homeostatic and therapeutic roles of VIP in smooth muscle function: myo-neuroimmune interactions

2009 ◽  
Vol 297 (4) ◽  
pp. G716-G725 ◽  
Author(s):  
Xuan-Zheng Shi ◽  
Sushil K. Sarna
Keyword(s):  
Smooth Muscle ◽  
Inflammatory Response ◽  
Muscle Function ◽  
Contractile Response ◽  
Enteric Neurons ◽  
Muscle Dysfunction ◽  
Spontaneous Release ◽  
Circular Smooth Muscle ◽  
Smooth Muscle Function ◽  
Smooth Muscle Dysfunction

We tested the hypothesis that spontaneous release of vasoactive intestinal peptide (VIP) from enteric neurons maintains homeostasis in smooth muscle function in mild inflammatory insults and that infusion of exogenous VIP has therapeutic effects on colonic smooth muscle dysfunction in inflammation. In vitro experiments were performed on human colonic circular smooth muscle tissues and in vivo on rats. The incubation of human colonic circular smooth muscle strips with TNF-α suppressed their contractile response to ACh and the expression of the pore-forming α1C subunit of Cav1.2 channels. VIP reversed both effects by blocking the translocation of NF-κB to the nucleus and its binding to the κB recognition sites on hα1C1b promoter. The translocation of NF-κB was inhibited by blocking the degradation of IκBβ. Induction of inflammation by a subthreshold dose of 17 mg/kg trinitrobenzene sulfonic acid (TNBS) in rats moderately decreased muscularis externa concentration of VIP, and it had little effect on the contractile response of circular smooth muscle strips to ACh. The blockade of VIP and pituitary adenylate cyclase-activating peptide receptors 1/2 during mild inflammatory insult significantly worsened the suppression of contractility and the inflammatory response. The induction of more severe inflammation by 68 mg/kg TNBS induced marked suppression of colonic circular muscle contractility and decrease in serum VIP. Exogenous infusion of VIP by an osmotic pump reversed these effects. We conclude that the spontaneous release of VIP from the enteric motor neurons maintains homeostasis in smooth muscle function in mild inflammation by blocking the activation of NF-κB. The infusion of exogenous VIP mitigates colonic inflammatory response and smooth muscle dysfunction.

Mechanism of partial adaptation in airway smooth muscle after a step change in length

2007 ◽  
Vol 103 (2) ◽  
pp. 569-577 ◽  
Author(s):  
Farah Ali ◽  
Leslie Chin ◽  
Peter D. Paré ◽  
Chun Y. Seow
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Intermediate State ◽  
Ultrastructural Changes ◽  
Myosin Filament ◽  
Shortening Velocity ◽  
Myosin Filaments ◽  
Partial Adaptation ◽  
Static Conditions

The phenomenon of length adaptation in airway smooth muscle (ASM) is well documented; however, the underlying mechanism is less clear. Evidence to date suggests that the adaptation involves reassembly of contractile filaments, leading to reconfiguration of the actin filament lattice and polymerization or depolymerization of the myosin filaments within the lattice. The time courses for these events are unknown. To gain insights into the adaptation process, we examined ASM mechanical properties and ultrastructural changes during adaptation. Step changes in length were applied to isolated bundles of ASM cells; changes in force, shortening velocity, and myosin filament mass were then quantified. A greater decrease in force was found following an acute decrease in length, compared with that of an acute increase in length. A decrease in myosin filament mass was also found with an acute decrease in length. The shortening velocity measured immediately after the length change was the same as that measured after the muscle had fully adapted to the new length. These observations can be explained by a model in which partial adaptation of the muscle leads to an intermediate state in which reconfiguration of the myofilament lattice occurred rapidly, followed by a relatively slow process of polymerization of myosin filaments within the lattice. The partially adapted intermediate state is perhaps more physiologically relevant than the fully adapted state seen under static conditions, and it simulates a more realistic behavior for ASM in vivo.

scholarly journals Force maintenance and myosin filament assembly regulated by Rho-kinase in airway smooth muscle

2015 ◽  
Vol 308 (1) ◽  
pp. L1-L10 ◽  
Author(s):  
Bo Lan ◽  
Linhong Deng ◽  
Graham M. Donovan ◽  
Leslie Y. M. Chin ◽  
Harley T. Syyong ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Initial Phase ◽  
Rho Kinase ◽  
Myosin Filament ◽  
Second Phase ◽  
Minimal Effect ◽  
Kinase Inhibition ◽  
Myosin Filaments ◽  
Force Maintenance

Smooth muscle contraction can be divided into two phases: the initial contraction determines the amount of developed force and the second phase determines how well the force is maintained. The initial phase is primarily due to activation of actomyosin interaction and is relatively well understood, whereas the second phase remains poorly understood. Force maintenance in the sustained phase can be disrupted by strains applied to the muscle; the strain causes actomyosin cross-bridges to detach and also the cytoskeletal structure to disassemble in a process known as fluidization, for which the underlying mechanism is largely unknown. In the present study we investigated the ability of airway smooth muscle to maintain force after the initial phase of contraction. Specifically, we examined the roles of Rho-kinase and protein kinase C (PKC) in force maintenance. We found that for the same degree of initial force inhibition, Rho-kinase substantially reduced the muscle's ability to sustain force under static conditions, whereas inhibition of PKC had a minimal effect on sustaining force. Under oscillatory strain, Rho-kinase inhibition caused further decline in force, but again, PKC inhibition had a minimal effect. We also found that Rho-kinase inhibition led to a decrease in the myosin filament mass in the muscle cells, suggesting that one of the functions of Rho-kinase is to stabilize myosin filaments. The results also suggest that dissolution of myosin filaments may be one of the mechanisms underlying the phenomenon of fluidization. These findings can shed light on the mechanism underlying deep inspiration induced bronchodilation.

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