scholarly journals Three-dimensional reconstruction of caldesmon-containing smooth muscle thin filaments.

1993 ◽  
Vol 123 (2) ◽  
pp. 313-321 ◽  
Author(s):  
P Vibert ◽  
R Craig ◽  
W Lehman
Keyword(s):  
Smooth Muscle ◽  
Three Dimensional ◽  
Smooth Muscles ◽  
Smooth Muscle Contraction ◽  
Structural Basis ◽  
Actin Monomer ◽  
Thin Filaments ◽  
Outer Domain ◽  
Dimensional Reconstruction

Caldesmon is known to inhibit actomyosin ATPase and filament sliding in vitro, and may play a role in modulating smooth muscle contraction as well as in diverse cellular processes including cytokinesis and exocytosis. However, the structural basis of caldesmon action has not previously been apparent. We have recorded electron microscope images of negatively stained thin filaments containing caldesmon and tropomyosin which were isolated from chicken gizzard smooth muscle in EGTA. Three-dimensional helical reconstructions of these filaments show actin monomers whose bilobed shape and connectivity are very similar to those previously seen in reconstructions of frozen-hydrated skeletal muscle thin filaments. In addition, a continuous thin strand of density follows the long-pitch actin helices, in contact with the inner domain of each actin monomer. Gizzard thin filaments treated with Ca2+/calmodulin, which dissociated caldesmon but not tropomyosin, have also been reconstructed. Under these conditions, reconstructions also reveal a bilobed actin monomer, as well as a continuous surface strand that appears to have moved to a position closer to the outer domain of actin. The strands seen in both EGTA- and Ca2+/calmodulin-treated filaments thus presumably represent tropomyosin. It appears that caldesmon can fix tropomyosin in a particular position on actin in the absence of calcium. An influence of caldesmon on tropomyosin position might, in principle, account for caldesmon's ability to modulate actomyosin interaction in both smooth muscles and non-muscle cells.

scholarly journals Anatomy of Cowper’s gland in humans suggesting a secretion and emission mechanism facilitated by cooperation of striated and smooth muscles

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Satoru Muro ◽  
Janyaruk Suriyut ◽  
Keiichi Akita
Keyword(s):  
Smooth Muscle ◽  
Striated Muscle ◽  
Three Dimensional ◽  
Smooth Muscles ◽  
Levator Ani ◽  
Striated Muscles ◽  
External Urethral Sphincter ◽  
Macroscopic Anatomy ◽  
Dimensional Reconstruction ◽  
Perineal Muscle

AbstractThis study presents the detailed anatomy of the Cowper’s gland in humans. Elucidating the mechanism of secretion and emission of the Cowper’s gland requires analysis of the muscles around the Cowper’s gland. We hypothesized that the Cowper’s gland involves not only smooth muscle but also the striated muscles of the pelvic floor. Here, we provide comprehensive and three-dimensional anatomy of the Cowper’s gland and its surrounding structures, which overcomes the current local and planar understanding. In this study, seven male corpses of body donors were used to conduct macroscopic anatomy, histology, and three-dimensional reconstruction. The Cowper’s gland was surrounded laterally and posterosuperiorly by striated and smooth muscles, respectively. The striated muscle bundle was connected from the superficial transverse perineal muscle, levator ani, and external anal sphincter to the external urethral sphincter (rhabdosphincter). The smooth muscle was part of the deep transverse perineal muscle and entered between the bilateral Cowper’s glands and lobules. Our findings indicate that the secretion and emission of the Cowper’s gland in humans are carried out through the cooperation of striated and smooth muscles.

Smooth muscle: contraction hypothesis based on the arrangement of actin and myosin filaments in different states of contraction*

1973 ◽  
Vol 265 (867) ◽  
pp. 213-217 ◽  
Keyword(s):  
Smooth Muscle ◽  
Muscle Contraction ◽  
Hexagonal Lattice ◽  
Smooth Muscles ◽  
Smooth Muscle Contraction ◽  
Thin Filaments ◽  
Random Fashion ◽  
Filament Bundles ◽  
Small Contraction ◽  
Electron Microscopical

Electron microscopical studies were m ade of the changes occurring during contraction of mouse taenia coli. In relaxed fibres actin filaments were found clearly ordered into bundles. W ithin the bundles the filaments were often arranged in rows or in a hexagonal lattice. In the areas between the filament bundles thick filaments were detected. The shortened fibres showed a different appearance. Thick and thin filaments were interm ingled in a random fashion. By com paring these findings with observations m ade on invertebrate smooth muscles, a model for smooth muscle contraction is proposed. According to this hypothesis the contractile apparatus of smooth muscles is composed of small contraction units of interdigitating bundles of thick and thin filaments. They seem to be irregularly shaped and random ly arranged. During the contraction the sets of filaments slide into each other. The result is the intermingling of the thick and thin filaments found in contracted fibres.

scholarly journals Myosin light chain kinase binding to a unique site on F-actin revealed by three-dimensional image reconstruction

2001 ◽  
Vol 154 (3) ◽  
pp. 611-618 ◽  
Author(s):  
Victoria Hatch ◽  
Gang Zhi ◽  
Lula Smith ◽  
James T. Stull ◽  
Roger Craig ◽  
...  
Keyword(s):  
Light Chain ◽  
Myosin Light Chain Kinase ◽  
Myosin Light Chain ◽  
Three Dimensional ◽  
Actin Binding ◽  
Structural Basis ◽  
Thin Filaments ◽  
Helical Reconstruction ◽  
Nonmuscle Cells

Ca2+–calmodulin-dependent phosphorylation of myosin regulatory light chains by the catalytic COOH-terminal half of myosin light chain kinase (MLCK) activates myosin II in smooth and nonmuscle cells. In addition, MLCK binds to thin filaments in situ and F-actin in vitro via a specific repeat motif in its NH2 terminus at a stoichiometry of one MLCK per three actin monomers. We have investigated the structural basis of MLCK–actin interactions by negative staining and helical reconstruction. F-actin was decorated with a peptide containing the NH2-terminal 147 residues of MLCK (MLCK-147) that binds to F-actin with high affinity. MLCK-147 caused formation of F-actin rafts, and single filaments within rafts were used for structural analysis. Three-dimensional reconstructions showed MLCK density on the extreme periphery of subdomain-1 of each actin monomer forming a bridge to the periphery of subdomain-4 of the azimuthally adjacent actin. Fitting the reconstruction to the atomic model of F-actin revealed interaction of MLCK-147 close to the COOH terminus of the first actin and near residues 228–232 of the second. This unique location enables MLCK to bind to actin without interfering with the binding of any other key actin-binding proteins, including myosin, tropomyosin, caldesmon, and calponin.

Regulatory mechanism of smooth muscle contraction studied with gelsolin-treated strips of taenia caeci in guinea pig

2009 ◽  
Vol 296 (5) ◽  
pp. C1024-C1033 ◽  
Author(s):  
Ying-Ming Liou ◽  
Masaru Watanabe ◽  
Masatoshi Yumoto ◽  
Shin'ichi Ishiwata
Keyword(s):  
Smooth Muscle ◽  
Muscle Contraction ◽  
Actin Filaments ◽  
Smooth Muscles ◽  
Smooth Muscle Contraction ◽  
Irreversible Damage ◽  
Cross Sectional ◽  
Thin Filaments ◽  
Force Development ◽  
Skinned Smooth Muscle

The potential roles of the regulatory proteins actin, tropomyosin (Tm), and caldesmon (CaD), i.e., the components of the thin filament, in smooth muscle have been extensively studied in several types of smooth muscles. However, controversy remains on the putative physiological significance of these proteins. In this study, we intended to determine the functional roles of Tm and CaD in the regulation of smooth muscle contraction by using a reconstitution system of the thin filaments. At appropriate conditions, the thin (actin) filaments within skinned smooth muscle strips of taenia caeci in guinea pigs could be selectively removed by an actin-severing protein, gelsolin, without irreversible damage to the contractile apparatus, and then the thin filaments were reconstituted with purified components of thin filaments, i.e., actin, Tm, and CaD. We found that the structural remodeling of actin filaments or thin filaments was functionally linked to the Ca2+-induced force development and reduction in muscle cross-sectional area (CSA). That is, after the reconstitution of the gelsolin-treated skinned smooth muscle strips with pure actin, the Ca2+-dependent force development was partially restored, but the Ca2+-induced reduction in CSA occurred once. In contrast, the reconstitution with actin, followed by Tm and CaD, restored not only the force generation but also both its Ca2+sensitivity and the reversible Ca2+-dependent reduction in CSA. We confirmed that both removal of the thin filaments by gelsolin treatment and reconstitution of the actin (thin) filaments with Tm and CaD caused no significant changes in the level of myosin regulatory light chain phosphorylation. We thus conclude that Tm and CaD are necessary for the full regulation of smooth muscle contraction in addition to the other regulatory systems, including the myosin-linked one.

Human vascular smooth muscle responses mediated by α2 mechanisms in vivo and in vitro

1985 ◽  
Vol 68 (s10) ◽  
pp. 147s-150s ◽  
Author(s):  
S. Thom ◽  
J. Calvete ◽  
R. Hayes ◽  
G. Martin ◽  
P. Sever
Keyword(s):  
Smooth Muscle ◽  
Physiological Role ◽  
Smooth Muscle Contraction ◽  
Α1 Receptors ◽  
Dose Dependent ◽  
Higher Doses ◽  
Α2 Receptors ◽  
Autoregulatory Mechanism

1. The effects of compounds with α2-agonist and α2-antagonist properties on human forearm blood flow and on isolated human arterial segments have been studied. 2. The findings from these studies in vivo and in vitro did not provide evidence in support of the hypothesis that postsynaptic α2-receptors mediate smooth muscle contraction in the tissues under investigation. 3. The constriction of the forearm vascular bed in response to low intra-arterial doses of idazoxan (RX 781094), an α2-antagonist, provides evidence for a physiological role for a presynaptic α2 autoregulatory mechanism. 4. The variability of the forearm vascular responses to higher doses of idazoxan highlights the pitfalls that may have misled previous authors in their interpretation of the results of similar studies. A U-shaped dose-response curve to compounds with mixed α2-and α1-antagonist properties may be constructed, which emphasizes the importance of the dose-dependent selectivity of these antagonists at α2- and α1-receptors. 5. The effect of idazoxan on the responses of arterial segments in vitro to exogenous catecholamines was dependent on the integrity of the endothelium, and provides evidence that α2-receptors may mediate release of the endothelium-derived relaxing factor.

scholarly journals Aging-associated changes in microRNA expression profile of internal anal sphincter smooth muscle: Role of microRNA-133a

2016 ◽  
Vol 311 (5) ◽  
pp. G964-G973 ◽  
Author(s):  
Jagmohan Singh ◽  
Ettickan Boopathi ◽  
Sankar Addya ◽  
Benjamin Phillips ◽  
Isidore Rigoutsos ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Anal Sphincter ◽  
Internal Anal Sphincter ◽  
Smooth Muscles ◽  
Smooth Muscle Contractility ◽  
Network Analyses ◽  
Rhoa Signaling

A comprehensive genomic and proteomic, computational, and physiological approach was employed to examine the (previously unexplored) role of microRNAs (miRNAs) as regulators of internal anal sphincter (IAS) smooth muscle contractile phenotype and basal tone. miRNA profiling, genome-wide expression, validation, and network analyses were employed to assess changes in mRNA and miRNA expression in IAS smooth muscles from young vs. aging rats. Multiple miRNAs, including rno-miR-1, rno-miR-340-5p, rno-miR-185, rno-miR-199a-3p, rno-miR-200c, rno-miR-200b, rno-miR-31, rno-miR-133a, and rno-miR-206, were found to be upregulated in aging IAS. qPCR confirmed the upregulated expression of these miRNAs and downregulation of multiple, predicted targets ( Eln, Col3a1, Col1a1, Zeb2, Myocd, Srf, Smad1, Smad2, Rhoa/Rock2, Fn1, Tagln v2, Klf4, and Acta2) involved in regulation of smooth muscle contractility. Subsequent studies demonstrated an aging-associated increase in the expression of miR-133a, corresponding decreases in RhoA, ROCK2, MYOCD, SRF, and SM22α protein expression, RhoA-signaling, and a decrease in basal and agonist [U-46619 (thromboxane A2analog)]-induced increase in the IAS tone. Moreover, in vitro transfection of miR-133a caused a dose-dependent increase of IAS tone in strips, which was reversed by anti-miR-133a. Last, in vivo perianal injection of anti-miR-133a reversed the loss of IAS tone associated with age. This work establishes the important regulatory effect of miRNA-133a on basal and agonist-stimulated IAS tone. Moreover, reversal of age-associated loss of tone via anti-miR delivery strongly implicates miR dysregulation as a causal factor in the aging-associated decrease in IAS tone and suggests that miR-133a is a feasible therapeutic target in aging-associated rectoanal incontinence.

Ca2+-independent contraction of longitudinal ileal smooth muscle is potentiated by a zipper-interacting protein kinase pseudosubstrate peptide

2009 ◽  
Vol 297 (2) ◽  
pp. G361-G370 ◽  
Author(s):  
Eikichi Ihara ◽  
Lori Moffat ◽  
Meredith A. Borman ◽  
Jennifer E. Amon ◽  
Michael P. Walsh ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Protein Kinase ◽  
Conformational Changes ◽  
Kinase Inhibitor ◽  
Smooth Muscles ◽  
Dominant Negative ◽  
Myosin Phosphatase ◽  
Interacting Protein ◽  
Zipper Interacting Protein Kinase

As a regulator of smooth muscle contraction, zipper-interacting protein kinase (ZIPK) can directly phosphorylate the myosin regulatory light chains (LC20) and produce contractile force. Synthetic peptides (SM-1 and AV25) derived from the autoinhibitory region of smooth muscle myosin light chain kinase can inhibit ZIPK activity in vitro. Paradoxically, treatment of Triton-skinned ileal smooth muscle strips with AV25, but not SM-1, potentiated Ca2+-independent, microcystin- and ZIPK-induced contractions. The AV25-induced potentiation was limited to ileal and colonic smooth muscles and was not observed in rat caudal artery. Thus the potentiation of Ca2+-independent contractions by AV25 appeared to be mediated by a mechanism unique to intestinal smooth muscle. AV25 treatment elicited increased phosphorylation of LC20 (both Ser-19 and Thr-18) and myosin phosphatase-targeting subunit (MYPT1, inhibitory Thr-697 site), suggesting involvement of a Ca2+-independent LC20 kinase with coincident inhibition of myosin phosphatase. The phosphorylation of the inhibitor of myosin phosphatase, CPI-17, was not affected. The AV25-induced potentiation was abolished by pretreatment with staurosporine, a broad-specificity kinase inhibitor, but specific inhibitors of Rho-associated kinase, PKC, and MAPK pathways had no effect. When a dominant-negative ZIPK [kinase-dead ZIPK(1–320)-D161A] was added to skinned ileal smooth muscle, the potentiation of microcystin-induced contraction by AV25 was blocked. Furthermore, pretreatment of skinned ileal muscle with SM-1 abolished AV25-induced potentiation. We conclude, therefore, that, even though AV25 is an in vitro inhibitor of ZIPK, activation of the ZIPK pathway occurs following application of AV25 to permeabilized ileal smooth muscle. Finally, we propose a mechanism whereby conformational changes in the pseudosubstrate region of ZIPK permit augmentation of ZIPK activity toward LC20 and MYPT1 in situ. AV25 or molecules based on its structure could be used in therapeutic situations to induce contractility in diseases of the gastrointestinal tract associated with hypomotility.

scholarly journals The effects of wild-type and mutant SOD1 on smooth muscle contraction

2015 ◽  
Vol 67 (1) ◽  
pp. 187-192 ◽  
Author(s):  
Aleksandra Nikolic-Kokic ◽  
Zorana Orescanin-Dusic ◽  
Ivan Spasojevic ◽  
Dusko Blagojevic ◽  
Zorica Stevic ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Muscle Relaxation ◽  
Smooth Muscles ◽  
Smooth Muscle Contraction ◽  
Smooth Muscle Relaxation ◽  
Transgenic Rat ◽  
Wild Type ◽  
Liver Copper ◽  
Ion Conducting ◽  
G93a Sod1

In this work we compared the mutated liver copper zinc-containing superoxide dismutase (SOD1) protein G93A of the transgenic rat model of familial amyotrophic lateral sclerosis (FALS), to wild-type (WT) rat SOD1. We examined their enzymatic activities and effects on isometric contractions of uteri of healthy virgin rats. G93A SOD1 showed a slightly higher activity than WT SOD1 and, in contrast to WT SOD1, G93A SOD1 did not induce smooth muscle relaxation. This result indicates that effects on smooth muscles are not related to SOD1 enzyme activity and suggest that heterodimers of G93A SOD1 form an ion-conducting pore that diminishes the relaxatory effects of SOD1. We propose that this type of pathogenic feedback affects neurons in FALS.

Phosphorylation of caldesmon by ERK MAP kinases in smooth muscle

2000 ◽  
Vol 278 (4) ◽  
pp. C718-C726 ◽  
Author(s):  
Jason C. Hedges ◽  
Brian C. Oxhorn ◽  
Michael Carty ◽  
Leonard P. Adam ◽  
Ilia A. Yamboliev ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Map Kinase ◽  
Map Kinases ◽  
Isometric Force ◽  
Phosphorylation Site ◽  
Smooth Muscle Contraction ◽  
Tracheal Smooth Muscle ◽  
Muscarinic Agonists

Phosphorylation of h-caldesmon has been proposed to regulate airway smooth muscle contraction. Both extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein (MAP) kinases phosphorylate h-caldesmon in vitro. To determine whether both enzymes phosphorylate caldesmon in vivo, phosphorylation-site-selective antibodies were used to assay phosphorylation of MAP kinase consensus sites. Stimulation of cultured tracheal smooth muscle cells with ACh or platelet-derived growth factor increased caldesmon phosphorylation at Ser789 by about twofold. Inhibiting ERK MAP kinase activation with 50 μM PD-98059 blocked agonist-induced caldesmon phosphorylation completely. Inhibiting p38 MAP kinases with 25 μM SB-203580 had no effect on ACh-induced caldesmon phosphorylation. Carbachol stimulation increased caldesmon phosphorylation at Ser789 in intact tracheal smooth muscle, which was blocked by the M2 antagonist AF-DX 116 (1 μM). AF-DX 116 inhibited carbachol-induced isometric contraction by 15 ± 1.4%, thus dissociating caldesmon phosphorylation from contraction. Activation of M2 receptors leads to activation of ERK MAP kinases and phosphorylation of caldesmon with little or no functional effect on isometric force. P38 MAP kinases are also activated by muscarinic agonists, but they do not phosphorylate caldesmon in vivo.

scholarly journals Decreased airway narrowing and smooth muscle contraction in hyperresponsive pigs

2002 ◽  
Vol 93 (4) ◽  
pp. 1296-1300 ◽  
Author(s):  
Debra J. Turner ◽  
Peter B. Noble ◽  
Matthew P. Lucas ◽  
Howard W. Mitchell
Keyword(s):  
Smooth Muscle ◽  
Airway Hyperresponsiveness ◽  
Porcine Model ◽  
Smooth Muscle Contraction ◽  
Airway Wall ◽  
Muscle Contractility ◽  
Smooth Muscle Contractility ◽  
Airway Narrowing

Increased smooth muscle contractility or reduced smooth muscle mechanical loads could account for the excessive airway narrowing and hyperresponsiveness seen in asthma. These mechanisms were investigated by using an allergen-induced porcine model of airway hyperresponsiveness. Airway narrowing to electric field stimulation was measured in isolated bronchial segments, over a range of transmural pressures (0–20 cmH2O). Contractile responses to ACh were measured in bronchial segments and in isolated tracheal smooth muscle strips isolated from control and test (ovalbumin sensitized and challenged) pigs. Test airways narrowed less than controls ( P < 0.0001). Test pigs showed reduced contractility to ACh, both in isolated bronchi ( P < 0.01) and smooth muscle strips ( P < 0.01). Thus isolated airways from pigs exhibiting airway hyperresponsiveness in vivo are hyporesponsive in vitro. The decreased narrowing in bronchi from hyperresponsive pigs may be related to decreased smooth muscle contractility. These data suggest that mechanisms external to the airway wall may be important to the hyperresponsive nature of sensitized lungs.

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