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Hashmi SK, Ceron RH, Heuckeroth RO. Visceral myopathy: clinical syndromes, genetics, pathophysiology, and fall of the cytoskeleton. Am J Physiol Gastrointest Liver Physiol 2021; 320:G919-G935. [PMID: 33729000 PMCID: PMC8285581 DOI: 10.1152/ajpgi.00066.2021] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Visceral smooth muscle is a crucial component of the walls of hollow organs like the gut, bladder, and uterus. This specialized smooth muscle has unique properties that distinguish it from other muscle types and facilitate robust dilation and contraction. Visceral myopathies are diseases where severe visceral smooth muscle dysfunction prevents efficient movement of air and nutrients through the bowel, impairs bladder emptying, and affects normal uterine contraction and relaxation, particularly during pregnancy. Disease severity exists along a spectrum. The most debilitating defects cause highly dysfunctional bowel, reduced intrauterine colon growth (microcolon), and bladder-emptying defects requiring catheterization, a condition called megacystis-microcolon-intestinal hypoperistalsis syndrome (MMIHS). People with MMIHS often die early in childhood. When the bowel is the main organ affected and microcolon is absent, the condition is known as myopathic chronic intestinal pseudo-obstruction (CIPO). Visceral myopathies like MMIHS and myopathic CIPO are most commonly caused by mutations in contractile apparatus cytoskeletal proteins. Here, we review visceral myopathy-causing mutations and normal functions of these disease-associated proteins. We propose molecular, cellular, and tissue-level models that may explain clinical and histopathological features of visceral myopathy and hope these observations prompt new mechanistic studies.
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Affiliation(s)
- Sohaib Khalid Hashmi
- 1Department of Pediatrics, The Children’s Hospital
of Philadelphia Research Institute and the Perelman School of Medicine at the University of Pennsylvania, Abramson Research Center, Philadelphia, Pennsylvania,2Department of Bioengineering, The University of Pennsylvania School of Engineering and Applied Science, Philadelphia, Pennsylvania
| | - Rachel Helen Ceron
- 1Department of Pediatrics, The Children’s Hospital
of Philadelphia Research Institute and the Perelman School of Medicine at the University of Pennsylvania, Abramson Research Center, Philadelphia, Pennsylvania,3Department of Physiology, The University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania
| | - Robert O. Heuckeroth
- 1Department of Pediatrics, The Children’s Hospital
of Philadelphia Research Institute and the Perelman School of Medicine at the University of Pennsylvania, Abramson Research Center, Philadelphia, Pennsylvania
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2
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Issouf M, Vargas A, Boivin R, Lavoie J. SRSF6 is upregulated in asthmatic horses and involved in the MYH11 SMB expression. Physiol Rep 2018; 6:e13896. [PMID: 30350466 PMCID: PMC6198134 DOI: 10.14814/phy2.13896] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Accepted: 09/26/2018] [Indexed: 11/24/2022] Open
Abstract
Smooth muscle has a central role in bronchospasm-induced airway obstruction in asthma. Alternative mRNA splicing of the smooth muscle myosin heavy chain (myh11) gene produces four different isoforms, one of which (SMB) is characterized by the inclusion of the exon5b, which doubles the smooth muscle cells contraction velocity. Deciphering the regulation of the expression levels of the SMB isoform would represent a major step for the understanding of the triggers and pathways leading to airway smooth muscle contraction in asthma. Our objective was therefore, to study the splicing regulation mechanisms of the exon5b in airway smooth muscle cells. Bioinformatics analysis was performed to identify the cis-regulatory elements present in the exon5b using HSF finder 3 tool. The expression of the corresponding serine/arginine rich protein (SR) genes thus identified was evaluated by quantitative RT-PCR (qPCR). SRSF1, SRSF6, and hnRNPA1 cis-acting elements were identified by in silico analysis of the exon5b sequence as splicing regulator candidates. QPCR analyses showed that SRSF1 and SRSF6 are upregulated in ASM cells from asthmatic horses in exacerbation (n = 5) compared to controls (n = 5). The inhibition of the identified splicing factors by small interfering RNA allowed identifying the regulation of the SMB isoform by SRSF6. Our results implicate for the first time the upregulation of SRSF6 and SRSF1 in the asthmatic ASM cells and indicate that SRSF6 induces the exon5b inclusion. This study provides an important first step for the understanding of the triggers and pathways leading to ASM hypercontraction and identifies a possible new target for asthma.
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Affiliation(s)
- Mohamed Issouf
- Department of Clinical SciencesFaculty of Veterinary MedicineUniversité de MontréalSaint‐HyacintheQuebecCanada
| | - Amandine Vargas
- Department of Clinical SciencesFaculty of Veterinary MedicineUniversité de MontréalSaint‐HyacintheQuebecCanada
| | - Roxane Boivin
- Department of Clinical SciencesFaculty of Veterinary MedicineUniversité de MontréalSaint‐HyacintheQuebecCanada
| | - Jean‐Pierre Lavoie
- Department of Clinical SciencesFaculty of Veterinary MedicineUniversité de MontréalSaint‐HyacintheQuebecCanada
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3
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Brozovich FV, Nicholson CJ, Degen CV, Gao YZ, Aggarwal M, Morgan KG. Mechanisms of Vascular Smooth Muscle Contraction and the Basis for Pharmacologic Treatment of Smooth Muscle Disorders. Pharmacol Rev 2016; 68:476-532. [PMID: 27037223 PMCID: PMC4819215 DOI: 10.1124/pr.115.010652] [Citation(s) in RCA: 298] [Impact Index Per Article: 37.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The smooth muscle cell directly drives the contraction of the vascular wall and hence regulates the size of the blood vessel lumen. We review here the current understanding of the molecular mechanisms by which agonists, therapeutics, and diseases regulate contractility of the vascular smooth muscle cell and we place this within the context of whole body function. We also discuss the implications for personalized medicine and highlight specific potential target molecules that may provide opportunities for the future development of new therapeutics to regulate vascular function.
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Affiliation(s)
- F V Brozovich
- Department of Health Sciences, Boston University, Boston, Massachusetts (C.J.N., Y.Z.G., M.A., K.G.M.); Department of Medicine, Mayo Clinic, Rochester, Minnesota (F.V.B.); and Paracelsus Medical University Salzburg, Salzburg, Austria (C.V.D.)
| | - C J Nicholson
- Department of Health Sciences, Boston University, Boston, Massachusetts (C.J.N., Y.Z.G., M.A., K.G.M.); Department of Medicine, Mayo Clinic, Rochester, Minnesota (F.V.B.); and Paracelsus Medical University Salzburg, Salzburg, Austria (C.V.D.)
| | - C V Degen
- Department of Health Sciences, Boston University, Boston, Massachusetts (C.J.N., Y.Z.G., M.A., K.G.M.); Department of Medicine, Mayo Clinic, Rochester, Minnesota (F.V.B.); and Paracelsus Medical University Salzburg, Salzburg, Austria (C.V.D.)
| | - Yuan Z Gao
- Department of Health Sciences, Boston University, Boston, Massachusetts (C.J.N., Y.Z.G., M.A., K.G.M.); Department of Medicine, Mayo Clinic, Rochester, Minnesota (F.V.B.); and Paracelsus Medical University Salzburg, Salzburg, Austria (C.V.D.)
| | - M Aggarwal
- Department of Health Sciences, Boston University, Boston, Massachusetts (C.J.N., Y.Z.G., M.A., K.G.M.); Department of Medicine, Mayo Clinic, Rochester, Minnesota (F.V.B.); and Paracelsus Medical University Salzburg, Salzburg, Austria (C.V.D.)
| | - K G Morgan
- Department of Health Sciences, Boston University, Boston, Massachusetts (C.J.N., Y.Z.G., M.A., K.G.M.); Department of Medicine, Mayo Clinic, Rochester, Minnesota (F.V.B.); and Paracelsus Medical University Salzburg, Salzburg, Austria (C.V.D.)
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Nowakowski SG, Kolwicz SC, Korte FS, Luo Z, Robinson-Hamm JN, Page JL, Brozovich F, Weiss RS, Tian R, Murry CE, Regnier M. Transgenic overexpression of ribonucleotide reductase improves cardiac performance. Proc Natl Acad Sci U S A 2013; 110:6187-92. [PMID: 23530224 PMCID: PMC3625337 DOI: 10.1073/pnas.1220693110] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We previously demonstrated that cardiac myosin can use 2-deoxy-ATP (dATP) as an energy substrate, that it enhances contraction and relaxation with minimal effect on calcium-handling properties in vitro, and that contractile enhancement occurs with only minor elevation of cellular [dATP]. Here, we report the effect of chronically enhanced dATP concentration on cardiac function using a transgenic mouse that overexpresses the enzyme ribonucleotide reductase (TgRR), which catalyzes the rate-limiting step in de novo deoxyribonucleotide biosynthesis. Hearts from TgRR mice had elevated left ventricular systolic function compared with wild-type (WT) mice, both in vivo and in vitro, without signs of hypertrophy or altered diastolic function. Isolated cardiomyocytes from TgRR mice had enhanced contraction and relaxation, with no change in Ca(2+) transients, suggesting targeted improvement of myofilament function. TgRR hearts had normal ATP and only slightly decreased phosphocreatine levels by (31)P NMR spectroscopy, and they maintained rate responsiveness to dobutamine challenge. These data demonstrate long-term (at least 5-mo) elevation of cardiac [dATP] results in sustained elevation of basal left ventricular performance, with maintained β-adrenergic responsiveness and energetic reserves. Combined with results from previous studies, we conclude that this occurs primarily via enhanced myofilament activation and contraction, with similar or faster ability to relax. The data are sufficiently compelling to consider elevated cardiac [dATP] as a therapeutic option to treat systolic dysfunction.
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Affiliation(s)
| | - Stephen C. Kolwicz
- Mitochondria and Metabolism Center, University of Washington School of Medicine, Seattle, WA 98195
| | - Frederick Steven Korte
- Department of Bioengineering, University of Washington, Seattle, WA 98195
- Center for Cardiovascular Biology, Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA 98195
| | - Zhaoxiong Luo
- Department of Bioengineering, University of Washington, Seattle, WA 98195
| | | | - Jennifer L. Page
- Department of Biomedical Sciences, Cornell University, Ithaca, NY 14853
| | | | - Robert S. Weiss
- Department of Biomedical Sciences, Cornell University, Ithaca, NY 14853
| | - Rong Tian
- Mitochondria and Metabolism Center, University of Washington School of Medicine, Seattle, WA 98195
| | - Charles E. Murry
- Department of Bioengineering, University of Washington, Seattle, WA 98195
- Center for Cardiovascular Biology, Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA 98195
- Department of Pathology, University of Washington, Seattle, WA 98195; and
- Department of Medicine/Cardiology, University of Washington, Seattle, WA 98195
| | - Michael Regnier
- Department of Bioengineering, University of Washington, Seattle, WA 98195
- Center for Cardiovascular Biology, Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA 98195
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Kalganov A, Shalabi N, Zitouni N, Kachmar LH, Lauzon AM, Rassier DE. Forces measured with micro-fabricated cantilevers during actomyosin interactions produced by filaments containing different myosin isoforms and loop 1 structures. Biochim Biophys Acta Gen Subj 2012; 1830:2710-2719. [PMID: 23220701 DOI: 10.1016/j.bbagen.2012.11.022] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Revised: 11/23/2012] [Accepted: 11/26/2012] [Indexed: 10/27/2022]
Abstract
BACKGROUND There is evidence that the actin-activated ATP kinetics and the mechanical work produced by muscle myosin molecules are regulated by two surface loops, located near the ATP binding pocket (loop 1), and in a region that interfaces with actin (loop 2). These loops regulate force and velocity of contraction, and have been investigated mostly in single molecules. There is a lack of information of the work produced by myosin molecules ordered in filaments and working cooperatively, which is the actual muscle environment. METHODS We use micro-fabricated cantilevers to measure forces produced by myosin filaments isolated from mollusk muscles, skeletal muscles, and smooth muscles containing variations in the structure of loop 1 (tonic and phasic myosins). We complemented the experiments with in-vitro assays to measure the velocity of actin motility. RESULTS Smooth muscle myosin filaments produced more force than skeletal and mollusk myosin filaments when normalized per filament overlap. Skeletal muscle myosin propelled actin filaments in a higher sliding velocity than smooth muscle myosin. The values for force and velocity were consistent with previous studies using myosin molecules, and suggest a close correlation with the myosin isoform and structure of surface loop 1. GENERAL SIGNIFICANCE The technique using micro-fabricated cantilevers to measure force of filaments allows for the investigation of the relation between myosin structure and contractility, allowing experiments to be conducted with an array of different myosin isoforms. Using the technique we observed that the work produced by myosin molecules is regulated by amino-acid sequences aligned in specific loops.
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Affiliation(s)
- Albert Kalganov
- Department of Kinesiology and Physical Education, Faculty of Education, McGill University, Canada
| | - Nabil Shalabi
- Department of Mechanical Engineering, Faculty of Engineering McGill University, Canada
| | - Nedjma Zitouni
- Meakins-Christie Laboratories, McGill University, Canada; Department of Experimental Medicine, Faculty of Medicine McGill University, Canada
| | - Linda Hussein Kachmar
- Meakins-Christie Laboratories, McGill University, Canada; Department of Experimental Medicine, Faculty of Medicine McGill University, Canada
| | - Anne-Marie Lauzon
- Meakins-Christie Laboratories, McGill University, Canada; Department of Experimental Medicine, Faculty of Medicine McGill University, Canada; Departments of Physics, Faculty of Science, McGill University, Canada; Department of Physiology, Faculty of Medicine, McGill University, Canada
| | - Dilson E Rassier
- Department of Kinesiology and Physical Education, Faculty of Education, McGill University, Canada; Meakins-Christie Laboratories, McGill University, Canada; Department of Experimental Medicine, Faculty of Medicine McGill University, Canada; Departments of Physics, Faculty of Science, McGill University, Canada; Department of Physiology, Faculty of Medicine, McGill University, Canada.
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6
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Huang Q, Babu GJ, Periasamy M, Eddinger TJ. SMB myosin heavy chain knockout enhances tonic contraction and reduces the rate of force generation in ileum and stomach antrum. Am J Physiol Cell Physiol 2012; 304:C194-206. [PMID: 23135699 DOI: 10.1152/ajpcell.00280.2012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The role of SMA and SMB smooth muscle myosin heavy chain (MHC) isoforms in tonic and phasic contractions was studied in phasic (longitudinal ileum and stomach circular antrum) and tonic (stomach circular fundus) smooth muscle tissues of SMB knockout mice. Knocking out the SMB MHC gene eliminated SMB MHC protein expression and resulted in upregulation of the SMA MHC protein without altering the total MHC protein level. Switching from SMB to SMA MHC protein expression decreased the rate of the force transient and increased the sustained tonic force in SMB((-/-)) ileum and antrum with high potassium (KPSS) but not with carbachol (CCh) stimulation. The increased tonic contraction under the depolarized condition was not through changes in second messenger signaling pathways (PKC/CPI-17 or Rho/ROCK signaling pathway) or LC(20) phosphorylation. Biochemical analyses showed that the expression of contractile regulatory proteins (MLCK, MLCP, PKCδ, and CPI-17) did not change significantly in tissues tested except for PKCα protein expression being significantly decreased in the SMB((-/-)) antrum. However, specifically activating PKCα with phorbol dibutyrate (PDBu) was not significantly different in knockout and wild-type tissues, with total force being a fraction of the force generation with KPSS or CCh stimulation in SMB((-/-)) ileum and antrum. Taken together, these data show removing the SMB MHC protein expression with a compensatory increase in the SMA MHC protein results in enhanced sustained KPSS-induced tonic contraction with a reduced rate of force generation in these phasic tissues.
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Affiliation(s)
- Qian Huang
- Department of Biological Sciences, Marquette University, Milwaukee, WI, 53201, USA
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7
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Guvenc B, Ustunel C, Ozturk N, Brozovich FV. A dynamic approach reveals non-muscle myosin influences the overall smooth muscle cross-bridge cycling rate. FEBS Lett 2010; 584:2862-6. [PMID: 20447398 DOI: 10.1016/j.febslet.2010.04.070] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2010] [Accepted: 04/27/2010] [Indexed: 11/16/2022]
Abstract
Recent evidence suggests that non-muscle myosin IIB (NMIIB) contributes to smooth muscle contraction. This study was designed to determine the effects of NMIIB on the cross-bridge cycling rate. The cross-bridge cycling rate was investigated using sinusoidal analysis. Frequency analysis revealed two asymptotes in the Bode plot of the data; and the intersection of the asymptotes (corner frequency) was higher for the B(+/-) strain (8.73+/-1.10 Hz vs 16.56+/-1.26 Hz, P<0.05), consistent with a higher overall cross-bridge cycling rate in heterozygous NMIIB KO (B(+/-)) vs WT mice. These results demonstrate that because of their long duty cycle, NMIIB cross-bridges act as an internal load on smooth muscle myosin to decrease the overall cross-bridge cycling rate and muscle V(max) during force maintenance.
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Affiliation(s)
- Bilge Guvenc
- Department of Biomedical Engineering and Physiology, Mayo Medical School, Rochester, MN, USA
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8
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Yuen SL, Ogut O, Brozovich FV. Nonmuscle myosin is regulated during smooth muscle contraction. Am J Physiol Heart Circ Physiol 2009; 297:H191-9. [PMID: 19429828 DOI: 10.1152/ajpheart.00132.2009] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The participation of nonmuscle myosin in force maintenance is controversial. Furthermore, its regulation is difficult to examine in a cellular context, as the light chains of smooth muscle and nonmuscle myosin comigrate under native and denaturing electrophoresis techniques. Therefore, the regulatory light chains of smooth muscle myosin (SM-RLC) and nonmuscle myosin (NM-RLC) were purified, and these proteins were resolved by isoelectric focusing. Using this method, intact mouse aortic smooth muscle homogenates demonstrated four distinct RLC isoelectric variants. These spots were identified as phosphorylated NM-RLC (most acidic), nonphosphorylated NM-RLC, phosphorylated SM-RLC, and nonphosphorylated SM-RLC (most basic). During smooth muscle activation, NM-RLC phosphorylation increased. During depolarization, the increase in NM-RLC phosphorylation was unaffected by inhibition of either Rho kinase or PKC. However, inhibition of Rho kinase blocked the angiotensin II-induced increase in NM-RLC phosphorylation. Additionally, force for angiotensin II stimulation of aortic smooth muscle from heterozygous nonmuscle myosin IIB knockout mice was significantly less than that of wild-type littermates, suggesting that, in smooth muscle, activation of nonmuscle myosin is important for force maintenance. The data also demonstrate that, in smooth muscle, the activation of nonmuscle myosin is regulated by Ca(2+)-calmodulin-activated myosin light chain kinase during depolarization and a Rho kinase-dependent pathway during agonist stimulation.
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Affiliation(s)
- Samantha L Yuen
- Cardiovascular Diseases, Mayo Medical School, Rochester, MN 55905, USA
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9
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Hypolite JA, Chang S, LaBelle E, Babu GJ, Periasamy M, Wein AJ, Chacko S. Deletion of SM-B, the high ATPase isoform of myosin, upregulates the PKC-mediated signal transduction pathway in murine urinary bladder smooth muscle. Am J Physiol Renal Physiol 2008; 296:F658-65. [PMID: 19052105 DOI: 10.1152/ajprenal.90221.2008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Detrusor smooth muscle (DSM) hypertrophy induced by partial bladder outlet obstruction (PBOO) is associated with changes in the NH2-terminal myosin heavy chain isoform from predominantly SM-B to SM-A, alteration in the Ca2+ sensitization pathway, and the contractile characteristics from phasic to tonic in rabbits. We utilized the SM-B knockout (KO) mouse to determine whether a shift from SM-B to SM-A without PBOO is associated with changes in the signal transduction pathway mediated via PKC and CPI-17, which keeps the myosin phosphorylation (MLC20) level high by inhibiting the myosin phosphatase. DSM strips from SM-B KO mice generated more force in response to electrical field stimulation, KCl, carbachol, and phorbol 12,13-dibutyrate than that of age-matched wild-type mice. There was no difference in the ED50 for carbachol but the maximum response was greater for the SM-B KO mice. DSM from SM-B KO mice revealed increased mass and hypertrophy. The KO mice also showed an overexpression of PKC-alpha, increased levels of phospho-CPI-17, and an elevated level of IP3 and DAG upon stimulation with carbachol. Two-dimensional gel electrophoresis revealed an increased level of MLC20 phosphorylation in response to carbachol. Together, these changes may be responsible for the higher level of force generation and maintenance by the DSM from the SM-B KO bladders. In conclusion, our data show that ablation of SM-B is associated with alteration of PKC-mediated signal transduction and CPI-17-mediated Ca2+ sensitization pathway that regulate smooth muscle contraction. Interestingly, similar changes are also present in PBOO-induced DSM compensatory response in the rabbit model in which SM-B is downregulated.
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Affiliation(s)
- Joseph A Hypolite
- Division of Urology and Department of Pathobiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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Léguillette R, Zitouni NB, Govindaraju K, Fong LM, Lauzon AM. Affinity for MgADP and force of unbinding from actin of myosin purified from tonic and phasic smooth muscle. Am J Physiol Cell Physiol 2008; 295:C653-60. [PMID: 18614813 DOI: 10.1152/ajpcell.00100.2008] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Smooth muscle is unique in its ability to maintain force at low MgATP consumption. This property, called the latch state, is more prominent in tonic than phasic smooth muscle. Studies performed at the muscle strip level have suggested that myosin from tonic muscle has a greater affinity for MgADP and therefore remains attached to actin longer than myosin from phasic muscle, allowing for cross-bridge dephosphorylation and latch-bridge formation. An alternative hypothesis is that after dephosphorylation, myosin reattaches to actin and maintains force. We investigated these fundamental properties of smooth muscle at the molecular level. We used an in vitro motility assay to measure actin filament velocity (nu(max)) when propelled by myosin purified from phasic or tonic muscle at increasing [MgADP]. Myosin was 25% thiophosphorylated and 75% unphosphorylated to approximate in vivo conditions. The slope of nu(max) versus [MgADP] was significantly greater for tonic (-0.51+/-0.04) than phasic muscle myosin (-0.15+/-0.04), demonstrating the greater MgADP affinity of myosin from tonic muscle. We then used a laser trap assay to measure the unbinding force from actin of populations of unphosphorylated tonic and phasic muscle myosin. Both myosin types attached to actin, and their unbinding force (0.092+/-0.022 pN for phasic muscle and 0.084+/-0.017 pN for tonic muscle) was not statistically different. We conclude that the greater affinity for MgADP of tonic muscle myosin and the reattachment of dephosphorylated myosin to actin may both contribute to the latch state.
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Affiliation(s)
- Renaud Léguillette
- Meakins-Christie Laboratories, Department of Medicine, McGill University, 3626 St-Urbain St., Montreal, QC, Canada H2X 2P2
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Kim KY, Kawamoto S, Bao J, Sellers JR, Adelstein RS. The B2 alternatively spliced isoform of nonmuscle myosin II-B lacks actin-activated MgATPase activity and in vitro motility. Biochem Biophys Res Commun 2007; 369:124-34. [PMID: 18060863 DOI: 10.1016/j.bbrc.2007.11.108] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2007] [Accepted: 11/15/2007] [Indexed: 10/24/2022]
Abstract
We report the initial biochemical characterization of an alternatively spliced isoform of nonmuscle heavy meromyosin (HMM) II-B2 and compare it with HMM II-B0, the nonspliced isoform. HMM II-B2 is the HMM derivative of an alternatively spliced isoform of endogenous nonmuscle myosin (NM) II-B, which has 21-amino acids inserted into loop 2, near the actin-binding region. NM II-B2 is expressed in the Purkinje cells of the cerebellum as well as in other neuronal cells [X. Ma, S. Kawamoto, J. Uribe, R.S. Adelstein, Function of the neuron-specific alternatively spliced isoforms of nonmuscle myosin II-B during mouse brain development, Mol. Biol. Cell 15 (2006) 2138-2149]. In contrast to any of the previously described isoforms of NM II (II-A, II-B0, II-B1, II-C0 and II-C1) or to smooth muscle myosin, the actin-activated MgATPase activity of HMM II-B2 is not significantly increased from a low, basal level by phosphorylation of the 20kDa myosin light chain (MLC-20). Moreover, although HMM II-B2 can bind to actin in the absence of ATP and is released in its presence, it cannot propel actin in the sliding actin filament assay following MLC-20 phosphorylation. Unlike HMM II-B2, the actin-activated MgATPase activity of a chimeric HMM with the 21-amino acid II-B2 sequence inserted into the homologous location in the heavy chain of HMM II-C is increased following MLC-20 phosphorylation. This indicates that the effect of the II-B2 insert is myosin heavy chain specific.
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Affiliation(s)
- Kye-Young Kim
- Laboratory of Molecular Cardiology, National Heart, Lung, and Blood Institute, National Institutes of Health Bethesda, MD 20892, USA
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12
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Babu GJ, Celia G, Rhee AY, Yamamura H, Takahashi K, Brozovich FV, Osol G, Periasamy M. Effects of h1-calponin ablation on the contractile properties of bladder versus vascular smooth muscle in mice lacking SM-B myosin. J Physiol 2006; 577:1033-42. [PMID: 16973711 PMCID: PMC1890375 DOI: 10.1113/jphysiol.2006.118828] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2006] [Accepted: 09/07/2006] [Indexed: 12/28/2022] Open
Abstract
The functional significance of smooth muscle-specific h1-calponin up-regulation in the smooth muscle contractility of SM-B null mice was studied by generating double knockout mice lacking both h1-calponin and SM-B myosin. The double knockout mice appear healthy, reproduce well and do not show any smooth muscle pathology. Loss of h1-calponin in the SM-B null mice bladder resulted in increased maximal shortening velocity (V(max)) and steady-state force generation. The force dilatation pressure, which was decreased in the SM-B null mesenteric vessels, was restored to wild-type levels in the double knockout vessels. In contrast, the half-time to maximal constriction was significantly increased in the double knockout vessels similar to that of SM-B null mice and indicating decreased shortening velocity in the double knockout vessels. Biochemical analyses showed that there is a significant reduction in smooth muscle alpha-actin levels, whereas h-caldesmon levels are increased in the double knockout bladder and mesenteric vessels, suggesting that these changes may also partly contribute to the altered contractile function. Taken together, our studies suggest that up-regulation of h1-calponin in the SM-B null mice may be necessary to maintain a reduced level of cross-bridge cycling over time in the absence of SM-B myosin and play an important role in regulating the smooth muscle contraction.
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Affiliation(s)
- Gopal J Babu
- Department of Physiology and Cell Biology, The Ohio State University College of Medicine and Public Health, 304 Hamilton Hall, 1645 Neil Avenue, Columbus, OH 43210, USA.
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13
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Ma X, Kawamoto S, Uribe J, Adelstein RS. Function of the neuron-specific alternatively spliced isoforms of nonmuscle myosin II-B during mouse brain development. Mol Biol Cell 2006; 17:2138-49. [PMID: 16481398 PMCID: PMC1446101 DOI: 10.1091/mbc.e05-10-0997] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2005] [Revised: 01/17/2006] [Accepted: 02/06/2006] [Indexed: 11/11/2022] Open
Abstract
We report that the alternatively spliced isoforms of nonmuscle myosin heavy chain II-B (NHMC II-B) play distinct roles during mouse brain development. The B1-inserted isoform of NMHC II-B, which contains an insert of 10 amino acids near the ATP-binding region (loop 1) of the myosin heavy chain, is involved in normal migration of facial neurons. In contrast, the B2-inserted isoform, which contains an insert of 21 amino acids near the actin-binding region (loop 2), is important for postnatal development of cerebellar Purkinje cells. Deletion of the B1 alternative exon, together with reduced expression of myosin II-B, results in abnormal migration and consequent protrusion of facial neurons into the fourth ventricle. This protrusion is associated with the development of hydrocephalus. Restoring the amount of myosin II-B expression to wild-type levels prevents these defects, showing the importance of total myosin activity in facial neuron migration. In contrast, deletion of the B2 alternative exon results in abnormal development of cerebellar Purkinje cells. Cells lacking the B2-inserted isoform show reduced numbers of dendritic spines and branches. Some of the B2-ablated Purkinje cells are misplaced in the cerebellar molecular layer. All of the B2-ablated mice demonstrated impaired motor coordination.
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Affiliation(s)
- Xuefei Ma
- Laboratory of Molecular Cardiology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
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Low R, Léguillette R, Lauzon AM. (+)Insert smooth muscle myosin heavy chain (SM-B): From single molecule to human. Int J Biochem Cell Biol 2006; 38:1862-74. [PMID: 16716643 DOI: 10.1016/j.biocel.2006.03.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2005] [Revised: 03/22/2006] [Accepted: 03/23/2006] [Indexed: 10/24/2022]
Abstract
In smooth muscle, alternative mRNA splicing of a single gene produces four myosin heavy chain (SMMHC) isoforms. Two of these isoforms differ by the presence [(+)insert] or absence [(-)insert] of a seven amino acid insert in the motor domain. This insert enhances the kinetic properties of myosin at the molecular level but its exact role at the cell and tissue levels still has to be elucidated. This review focuses on the expression and biological functions of the (+)insert isoform. Current knowledge is summarized regarding its tissue distribution in animals and humans. Studies at the molecular, cellular and tissue levels that aimed at understanding the contribution of this isoform to smooth muscle mechanical function are presented with a particular focus on velocity of shortening. In addition, the altered expression of the (+)insert isoform in diseases and models of diseases and the compensatory mechanisms that occur when the (+)insert is knocked out are discussed. The need for additional studies on the relationship of this isoform to contractile performance and how expression of this isoform is regulated are also considered.
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Affiliation(s)
- Robert Low
- University of Vermont, Burlington, VT 05405, United States
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15
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Karagiannis P, Babu GJ, Periasamy M, Brozovich FV. Myosin heavy chain isoform expression regulates shortening velocity in smooth muscle: studies using an SMB KO mouse line. J Muscle Res Cell Motil 2005; 25:149-58. [PMID: 15360130 DOI: 10.1023/b:jure.0000035879.87045.4b] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The kinetics of smooth muscle are thought to be partially determined by the level of the expression of the 7 amino acid insert, SMB, in the myosin heavy chain, as SMB is generally expressed at higher levels in faster smooth muscle. In this study, we determined the role of this insert on shortening velocity and force regeneration following rapid reduction in muscle length (k(step)) in bladder tissue from a transgenic mouse line expressing the insert at three different levels: wild type (WT, +/+, SMB/SMB), an SMA homozygous type (SMB KO, -/-), and a heterozygous type (+/-, SMB/SMA). Smooth muscle from +/+ bladder shorten faster than both the +/- and -/- bladder smooth muscle when activated with Ca2+, consistent with SMB determining the shortening velocity of smooth muscle. The addition of Pi to the fully activated skinned bladder strips did not affect the rate of shortening for either the +/+ or -/- bladder types but did significantly decrease the rate of shortening for the +/- type. In contrast, the addition of ADP to fully Ca2+ activated bladder strips increased the rate of shortening for all three bladder types. However after thiophosphorylation, ADP slowed the shortening velocity. These data are consistent with shortening velocity being determined by the level of activation (or crossbridge attachment) in smooth muscle. The rates of force regeneration according to the k(step) protocol showed no differences between bladder types and also proved insensitive to either Pi or ADP. These data suggest that the rates of force regeneration were determined not only by the kinetics of the crossbridge cycle, but also by factors outside the contractile apparatus.
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Affiliation(s)
- Peter Karagiannis
- Department of Physiology and Biophysics and Medicine (Cardiology), Case Western Reserve University, Cleveland OH 44106, USA
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Khromov AS, Webb MR, Ferenczi MA, Trentham DR, Somlyo AP, Somlyo AV. Myosin regulatory light chain phosphorylation and strain modulate adenosine diphosphate release from smooth muscle Myosin. Biophys J 2004; 86:2318-28. [PMID: 15041670 PMCID: PMC1304081 DOI: 10.1016/s0006-3495(04)74289-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The effects of myosin regulatory light chain (RLC) phosphorylation and strain on adenosine diphosphate (ADP) release from cross-bridges in phasic (rabbit bladder (Rbl)) and tonic (femoral artery (Rfa)) smooth muscle were determined by monitoring fluorescence transients of the novel ADP analog, 3'-deac-eda-ADP (deac-edaADP). Fluorescence transients reporting release of 3'-deac-eda-ADP were significantly faster in phasic (0.57 +/- 0.06 s(-1)) than tonic (0.29 +/- 0.03 s(-1)) smooth muscles. Thiophosphorylation of regulatory light chains increased and strain decreased the release rate approximately twofold. The calculated (k-ADP/k+ADP) dissociation constant, Kd of unstrained, unphosphorylated cross-bridges for ADP was 0.6 microM for rabbit bladder and 0.3 microM for femoral artery. The rates of ADP release from rigor bridges and reported values of Pi release (corresponding to the steady-state adenosine triphosphatase (ATPase) rate of actomyosin (AM)) from cross-bridges during a maintained isometric contraction are similar, indicating that the ADP-release step or an isomerization preceding it may be limiting the adenosine triphosphatase rate. We conclude that the strain- and dephosphorylation-dependent high affinity for and slow ADP release from smooth muscle myosin prolongs the fraction of the duty cycle occupied by strongly bound actomyosin.ADP state(s) and contributes to the high economy of force.
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Affiliation(s)
- Alexander S Khromov
- Molecular Physiology and Biological Physics, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908, USA
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Austin JC, Chacko SK, DiSanto M, Canning DA, Zderic SA. A MALE MURINE MODEL OF PARTIAL BLADDER OUTLET OBSTRUCTION REVEALS CHANGES IN DETRUSOR MORPHOLOGY, CONTRACTILITY AND MYOSIN ISOFORM EXPRESSION. J Urol 2004; 172:1524-8. [PMID: 15371884 DOI: 10.1097/01.ju.0000138045.61378.96] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE Mice with gene deletion or targeted over expression are important for understanding the remodeling that follows partial bladder outlet obstruction (PBOO). This condition predominates in males. We produced PBOO in male mice and now report the physiological, histological and molecular consequences. MATERIALS AND METHODS Male C57bl/6 mice were surgically obstructed or subjected to sham surgery and unoperated mice served as controls. Four weeks later the bladders were excised and their function was assessed with in vitro whole bladder cystometry. The optimum volume for pressure generation was determined and isometric pressures were measured for field stimulation and depolarization with KCl. Bladder hypertrophy was classified as severe-bladder mass greater than 50 mg or mild-bladder mass less than 50 mg. The percent muscle fraction was determined by histological analyses. The expression of C-terminal (SM1 and SM2) and N-terminal (SM-B and SM-A) isoforms of myosin heavy chain was analyzed by reverse transcriptase-polymerase chain reaction. RESULTS Severely hypertrophied bladders had larger optimum volume (p >0.001) and generated less pressure in response to field stimulation (p >0.001) and KCl (p >0.01) with a slower rate of pressure generation than controls or sham operated mice. Increased SM1-to-SM2 and SM-A-to-SM-B ratios were noted in severely obstructed bladders relative to controls or sham operated mice (p <0.05). The muscle fraction decreased slightly in the severely hypertrophied group (p not significant). CONCLUSIONS Our male mouse model of PBOO demonstrates an increase in bladder mass, larger capacity and significantly decreased pressure generation in the in vitro whole bladder model. Obstruction induced increases in the expression of C-terminal (SM1) and N-terminal (SM-A) myosin heavy chain isoforms.
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Affiliation(s)
- J Christopher Austin
- Division of Urology Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 19104, USA
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18
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Karim SM, Rhee AY, Given AM, Faulx MD, Hoit BD, Brozovich FV. Vascular reactivity in heart failure: role of myosin light chain phosphatase. Circ Res 2004; 95:612-8. [PMID: 15321927 DOI: 10.1161/01.res.0000142736.39359.58] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Congestive heart failure (CHF) is a clinical syndrome, which is the result of systolic or diastolic ventricular dysfunction. During CHF, vascular tone is regulated by the interplay of neurohormonal mechanisms and endothelial-dependent factors and is characterized by both central and peripheral vasoconstriction as well as a resistance to nitric oxide (NO)-mediated vasodilatation. At the molecular level, vascular tone depends on the level of regulatory myosin light chain phosphorylation, which is determined by the relative activities of myosin light chain kinase and myosin light chain phosphatase (MLCP). The MLCP is a trimeric enzyme with a catalytic, a 20-kDa and a myosin targeting (MYPT1) subunit. Alternative splicing of a 3' exon produces leucine zipper positive and negative (LZ+/-) MYPT1 isoforms. Expression of a LZ+ MYPT1 has been suggested to be required for NO-mediated smooth muscle relaxation. Thus, we hypothesized that the resistance to NO-mediated vasodilatation in CHF could be attributable to a change in the relative expression of LZ+/- MYPT1 isoforms. To test this hypothesis, left coronary artery ligation was used to induce CHF in rats, and both the dose response relationship of relaxation to 8-Br-cGMP in skinned smooth muscle and the relative expression of LZ+/- MYPT1 isoforms were determined. In control animals, the expression of the LZ+ MYPT1 isoform predominated in both the aorta and iliac artery. In CHF rats, LVEF was reduced to 30+/-5% and there was a significant decrease in both the sensitivity to 8-Br-cGMP and expression of the LZ+ MYPT1 isoform. These results indicate that CHF is associated with a decrease in the relative expression of the LZ+ MYPT1 isoform and the sensitivity to 8-Br-cGMP-mediated smooth muscle relaxation. The data suggest that the resistance to NO-mediated relaxation observed during CHF lies at least in part at the level of the smooth muscle and is a consequence of the decrease in the expression of the LZ+ MYPT1 isoform.
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MESH Headings
- Alternative Splicing
- Animals
- Blotting, Western
- Calcium/pharmacology
- Carrier Proteins/genetics
- Carrier Proteins/physiology
- Coronary Vessels
- Cyclic GMP/analogs & derivatives
- Cyclic GMP/pharmacology
- Dose-Response Relationship, Drug
- Heart Failure/diagnostic imaging
- Heart Failure/enzymology
- Heart Failure/etiology
- Heart Failure/physiopathology
- Ligation
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/enzymology
- Myocardial Infarction/complications
- Nitric Oxide/physiology
- Phosphoprotein Phosphatases/deficiency
- Phosphoprotein Phosphatases/genetics
- Phosphoprotein Phosphatases/physiology
- Phosphorylation
- Protein Isoforms/deficiency
- Protein Isoforms/genetics
- Protein Isoforms/physiology
- Protein Phosphatase 1
- Protein Processing, Post-Translational
- RNA, Messenger/biosynthesis
- RNA, Messenger/genetics
- Rats
- Rats, Sprague-Dawley
- Reverse Transcriptase Polymerase Chain Reaction
- Ultrasonography
- Vasodilation/drug effects
- Vasodilation/genetics
- Vasodilation/physiology
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Affiliation(s)
- Syed M Karim
- Department of Physiology, Case Western Reserve Univerisity, Cleveland, Ohio 44106-4970, USA
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19
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Abstract
Smooth muscle is a slow and economical muscle with a large variability in contractile properties. This review describes results regarding the relation between expression of myosin isoforms and the contraction of smooth muscle. The focus of the review is on studies of the organised contractile system in the smooth muscle tissue. The role of the myosin heavy chain variants formed by alternative splicing in the myosin heavy chain tail (SM1, SM2 isoforms) and head (SM-A SM-B isoforms) regions, as well as the role of essential light chains (LC17a, LC17b isoforms) for the variability of contractile properties are discussed. Smooth muscle also has the ability to alter its contractile properties in response to altered functional demands in vivo, e.g. during hypertrophic growth of urinary bladder, intestine, uterus and vessels and in response to altered hormone levels. These alterations involve changes in myosin expression and altered contractile kinetics. Non-muscle myosin has been shown to have a contractile function in some smooth muscle tissues and recent data on the kinetic properties of non-muscle myosin filaments in smooth muscle tissue are described.
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Affiliation(s)
- Anders Arner
- Department of Physiological Sciences, Medical Faculty, Lund University, BMC F11, Tornavägen 10, SE-221 84 Lund, Sweden.
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20
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Morano I. Tuning smooth muscle contraction by molecular motors. J Mol Med (Berl) 2003; 81:481-7. [PMID: 12879150 DOI: 10.1007/s00109-003-0451-x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2003] [Accepted: 05/14/2003] [Indexed: 10/26/2022]
Abstract
As in striated muscle, smooth muscle cells (SMC) contract by Ca2+ activated cyclic interaction between actin and type II myosin. However, smooth muscle maintains tone at basal activating Ca2+ and low energetic cost during sustained activation. This review analyzes the regulation of phasic and tonic contraction of SMC on the molecular level. Type II myosin is the molecular motor also of smooth muscle contraction. Six myosin heavy chain (MHC) isoenzymes (four smooth muscle, two nonmuscle) and five myosin light chain (MLC) isoforms (two 17 kDa, two 20 kDa, one 23 kDa) are expressed in SMC. These myosin subunits could be generated by alternative splicing or by differential gene expression. Thus different myosin isoenzymes are generated which may be modified posttranslationally by phosphorylation, affecting the contractile state of the SMC. Furthermore, they may be part of distinct contractile systems which are targeted by different second messenger cascades and are recruited differentially during activation, electromechanical, and pharmacomechanical coupling. Low energy consumption, shortening velocity, and MLC20 phosphorylation at low Ca2+ activation levels during tone maintenance ("latch") could be explained by a switch from smooth muscle myosin to nonmuscle myosin activation upon prolonged activation.
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Affiliation(s)
- Ingo Morano
- Max Delbrück Centrum for Molecular Medicine and Humboldt University, Johannes Müller Institute for Physiology, Berlin, Germany.
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