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Lee E, May H, Kazmierczak K, Liang J, Nguyen N, Hill JA, Gillette TG, Szczesna-Cordary D, Chang AN. The MYPT2-regulated striated muscle-specific myosin light chain phosphatase limits cardiac myosin phosphorylation in vivo. J Biol Chem 2024; 300:105652. [PMID: 38224947 PMCID: PMC10851227 DOI: 10.1016/j.jbc.2024.105652] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2023] [Revised: 01/02/2024] [Accepted: 01/04/2024] [Indexed: 01/17/2024] Open
Abstract
The physiological importance of cardiac myosin regulatory light chain (RLC) phosphorylation by its dedicated cardiac myosin light chain kinase has been established in both humans and mice. Constitutive RLC-phosphorylation, regulated by the balanced activities of cardiac myosin light chain kinase and myosin light chain phosphatase (MLCP), is fundamental to the biochemical and physiological properties of myofilaments. However, limited information is available on cardiac MLCP. In this study, we hypothesized that the striated muscle-specific MLCP regulatory subunit, MYPT2, targets the phosphatase catalytic subunit to cardiac myosin, contributing to the maintenance of cardiac function in vivo through the regulation of RLC-phosphorylation. To test this hypothesis, we generated a floxed-PPP1R12B mouse model crossed with a cardiac-specific Mer-Cre-Mer to conditionally ablate MYPT2 in adult cardiomyocytes. Immunofluorescence microscopy using the gene-ablated tissue as a control confirmed the localization of MYPT2 to regions where it overlaps with a subset of RLC. Biochemical analysis revealed an increase in RLC-phosphorylation in vivo. The loss of MYPT2 demonstrated significant protection against pressure overload-induced hypertrophy, as evidenced by heart weight, qPCR of hypertrophy-associated genes, measurements of myocyte diameters, and expression of β-MHC protein. Furthermore, mantATP chase assays revealed an increased ratio of myosin heads distributed to the interfilament space in MYPT2-ablated heart muscle fibers, confirming that RLC-phosphorylation regulated by MLCP, enhances cardiac performance in vivo. Our findings establish MYPT2 as the regulatory subunit of cardiac MLCP, distinct from the ubiquitously expressed canonical smooth muscle MLCP. Targeting MYPT2 to increase cardiac RLC-phosphorylation in vivo may improve baseline cardiac performance, thereby attenuating pathological hypertrophy.
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Affiliation(s)
- Eunyoung Lee
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Herman May
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Katarzyna Kazmierczak
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, Florida, USA
| | - Jingsheng Liang
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, Florida, USA
| | - Nhu Nguyen
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Joseph A Hill
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Thomas G Gillette
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Danuta Szczesna-Cordary
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, Florida, USA
| | - Audrey N Chang
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA; Pak Center for Mineral Metabolism and Clinical Research, UTSW Medical Center, Dallas, Texas, USA.
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2
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Prieto-Ruiz F, Gómez-Gil E, Martín-García R, Pérez-Díaz AJ, Vicente-Soler J, Franco A, Soto T, Pérez P, Madrid M, Cansado J. Myosin II regulatory light chain phosphorylation and formin availability modulate cytokinesis upon changes in carbohydrate metabolism. eLife 2023; 12:83285. [PMID: 36825780 PMCID: PMC10005788 DOI: 10.7554/elife.83285] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Accepted: 02/23/2023] [Indexed: 02/25/2023] Open
Abstract
Cytokinesis, the separation of daughter cells at the end of mitosis, relies in animal cells on a contractile actomyosin ring (CAR) composed of actin and class II myosins, whose activity is strongly influenced by regulatory light chain (RLC) phosphorylation. However, in simple eukaryotes such as the fission yeast Schizosaccharomyces pombe, RLC phosphorylation appears dispensable for regulating CAR dynamics. We found that redundant phosphorylation at Ser35 of the S. pombe RLC homolog Rlc1 by the p21-activated kinases Pak1 and Pak2, modulates myosin II Myo2 activity and becomes essential for cytokinesis and cell growth during respiration. Previously, we showed that the stress-activated protein kinase pathway (SAPK) MAPK Sty1 controls fission yeast CAR integrity by downregulating formin For3 levels (Gómez-Gil et al., 2020). Here, we report that the reduced availability of formin For3-nucleated actin filaments for the CAR is the main reason for the required control of myosin II contractile activity by RLC phosphorylation during respiration-induced oxidative stress. Thus, the restoration of For3 levels by antioxidants overrides the control of myosin II function regulated by RLC phosphorylation, allowing cytokinesis and cell proliferation during respiration. Therefore, fine-tuned interplay between myosin II function through Rlc1 phosphorylation and environmentally controlled actin filament availability is critical for a successful cytokinesis in response to a switch to a respiratory carbohydrate metabolism.
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Affiliation(s)
- Francisco Prieto-Ruiz
- Yeast Physiology Group. Department of Genetics and Microbiology. Campus de Excelencia Internacional de Ámbito Regional (CEIR) Campus Mare Nostrum, Universidad de MurciaMurciaSpain
| | - Elisa Gómez-Gil
- Yeast Physiology Group. Department of Genetics and Microbiology. Campus de Excelencia Internacional de Ámbito Regional (CEIR) Campus Mare Nostrum, Universidad de MurciaMurciaSpain
- The Francis Crick InstituteLondonUnited Kingdom
| | - Rebeca Martín-García
- Instituto de Biología Funcional y Genómica (IBFG), Consejo Superior de Investigaciones Científicas, Universidad de SalamancaSalamancaSpain
| | - Armando Jesús Pérez-Díaz
- Yeast Physiology Group. Department of Genetics and Microbiology. Campus de Excelencia Internacional de Ámbito Regional (CEIR) Campus Mare Nostrum, Universidad de MurciaMurciaSpain
| | - Jero Vicente-Soler
- Yeast Physiology Group. Department of Genetics and Microbiology. Campus de Excelencia Internacional de Ámbito Regional (CEIR) Campus Mare Nostrum, Universidad de MurciaMurciaSpain
| | - Alejandro Franco
- Yeast Physiology Group. Department of Genetics and Microbiology. Campus de Excelencia Internacional de Ámbito Regional (CEIR) Campus Mare Nostrum, Universidad de MurciaMurciaSpain
| | - Teresa Soto
- Yeast Physiology Group. Department of Genetics and Microbiology. Campus de Excelencia Internacional de Ámbito Regional (CEIR) Campus Mare Nostrum, Universidad de MurciaMurciaSpain
| | - Pilar Pérez
- Instituto de Biología Funcional y Genómica (IBFG), Consejo Superior de Investigaciones Científicas, Universidad de SalamancaSalamancaSpain
| | - Marisa Madrid
- Yeast Physiology Group. Department of Genetics and Microbiology. Campus de Excelencia Internacional de Ámbito Regional (CEIR) Campus Mare Nostrum, Universidad de MurciaMurciaSpain
| | - José Cansado
- Yeast Physiology Group. Department of Genetics and Microbiology. Campus de Excelencia Internacional de Ámbito Regional (CEIR) Campus Mare Nostrum, Universidad de MurciaMurciaSpain
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3
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Sobieszek A. Self-assembly of smooth muscle myosin filaments: adaptation of filament length by telokin and Mg·ATP. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2022; 51:449-463. [PMID: 35821526 DOI: 10.1007/s00249-022-01608-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 08/11/2021] [Accepted: 06/14/2022] [Indexed: 06/15/2023]
Abstract
The contractile apparatus of smooth muscle is malleable to accommodate stress and strain exerted on the muscle cell and to maintain optimal contractility. Structural lability of smooth muscle myosin filaments is believed to play an important role in the cell's malleability. However, the mechanism and regulation of myosin filament formation is still poorly understood. In the present in vitro study, using a static light scattering method, length distributions were obtained from suspensions of short myosin filaments (SFs) formed by rapid dilution or long ones (LFs) formed by slow dialysis. The distributions indicated the presence of dynamic equilibriums between soluble myosin and the SFs; i.e.: trimers, hexamers and mini filaments, covering the range up to 0.75 µm. The LFs were more stable, exhibiting favorable sizes at about 1.25, 2.4 and 4.5 µm. More distinct distributions were obtained from filaments adsorbed to a glass surface, by evanescent wave scattering and local electric field enhancement. Addition of telokin (TL) to the suspensions of unphosphorylated SFs resulted in widening of the soluble range, while in the case of the LFs this shift was larger, and accompanied by reduced contribution of the soluble myosin species. Such changes were largely absent in the case of phosphorylated myosin. In contrast, the presence of Mg·ATP resulted in elongation of the filaments and clear separation of filaments from soluble myosin species. Thus, TL and Mg·ATP appeared to modify the distribution of myosin filament lengths, i.e., increasing the lengths in preparing for phosphorylation, or reducing it to aid dephosphorylation.
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Affiliation(s)
- Apolinary Sobieszek
- Austrian Academy of Sciences, Dr. Iganz-Seipel-Platz 2, 1010, Vienna, Austria.
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4
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Heissler SM, Arora AS, Billington N, Sellers JR, Chinthalapudi K. Cryo-EM structure of the autoinhibited state of myosin-2. SCIENCE ADVANCES 2021; 7:eabk3273. [PMID: 34936462 PMCID: PMC8694606 DOI: 10.1126/sciadv.abk3273] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Accepted: 11/05/2021] [Indexed: 05/20/2023]
Abstract
We solved the near-atomic resolution structure of smooth muscle myosin-2 in the autoinhibited state (10S) using single-particle cryo–electron microscopy. The 3.4-Å structure reveals the precise molecular architecture of 10S and the structural basis for myosin-2 regulation. We reveal the position of the phosphorylation sites that control myosin autoinhibition and activation by phosphorylation of the regulatory light chain. Further, we present a previously unidentified conformational state in myosin-2 that traps ADP and Pi produced by the hydrolysis of ATP in the active site. This noncanonical state represents a branch of the myosin enzyme cycle and explains the autoinhibition of the enzyme function of 10S along with its reduced affinity for actin. Together, our structure defines the molecular mechanisms that drive 10S formation, stabilization, and relief by phosphorylation of the regulatory light chain.
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Affiliation(s)
- Sarah M. Heissler
- Department of Physiology and Cell Biology, Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Amandeep S. Arora
- Department of Physiology and Cell Biology, Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Neil Billington
- Laboratory of Molecular Physiology, National Heart, Lung, and Blood Institute, Bethesda, MD, USA
| | - James R. Sellers
- Laboratory of Molecular Physiology, National Heart, Lung, and Blood Institute, Bethesda, MD, USA
| | - Krishna Chinthalapudi
- Department of Physiology and Cell Biology, Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University College of Medicine, Columbus, OH, USA
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5
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Xiang X, Qiu R. Cargo-Mediated Activation of Cytoplasmic Dynein in vivo. Front Cell Dev Biol 2020; 8:598952. [PMID: 33195284 PMCID: PMC7649786 DOI: 10.3389/fcell.2020.598952] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Accepted: 10/07/2020] [Indexed: 12/12/2022] Open
Abstract
Cytoplasmic dynein-1 is a minus-end-directed microtubule motor that transports a variety of cargoes including early endosomes, late endosomes and other organelles. In many cell types, dynein accumulates at the microtubule plus end, where it interacts with its cargo to be moved toward the minus end. Dynein binds to its various cargoes via the dynactin complex and specific cargo adapters. Dynactin and some of the coiled-coil-domain-containing cargo adapters not only link dynein to cargo but also activate dynein motility, which implies that dynein is activated by its cellular cargo. Structural studies indicate that a dynein dimer switches between the autoinhibited phi state and an open state; and the binding of dynactin and a cargo adapter to the dynein tails causes the dynein motor domains to have a parallel configuration, allowing dynein to walk processively along a microtubule. Recently, the dynein regulator LIS1 has been shown to be required for dynein activation in vivo, and its mechanism of action involves preventing dynein from switching back to the autoinhibited state. In this review, we will discuss our current understanding of dynein activation and point out the gaps of knowledge on the spatial regulation of dynein in live cells. In addition, we will emphasize the importance of studying a complete set of dynein regulators for a better understanding of dynein regulation in vivo.
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Affiliation(s)
- Xin Xiang
- Department of Biochemistry and Molecular Biology, The Uniformed Services University of the Health Sciences - F. Edward Hébert School of Medicine, Bethesda, MD, United States
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6
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Platenkamp A, Detmar E, Sepulveda L, Ritz A, Rogers SL, Applewhite DA. The Drosophila melanogaster Rab GAP RN-tre cross-talks with the Rho1 signaling pathway to regulate nonmuscle myosin II localization and function. Mol Biol Cell 2020; 31:2379-2397. [PMID: 32816624 PMCID: PMC7851959 DOI: 10.1091/mbc.e20-03-0181] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
To identify novel regulators of nonmuscle myosin II (NMII) we performed an image-based RNA interference screen using stable Drosophila melanogaster S2 cells expressing the enhanced green fluorescent protein (EGFP)-tagged regulatory light chain (RLC) of NMII and mCherry-Actin. We identified the Rab-specific GTPase-activating protein (GAP) RN-tre as necessary for the assembly of NMII RLC into contractile actin networks. Depletion of RN-tre led to a punctate NMII phenotype, similar to what is observed following depletion of proteins in the Rho1 pathway. Depletion of RN-tre also led to a decrease in active Rho1 and a decrease in phosphomyosin-positive cells by immunostaining, while expression of constitutively active Rho or Rho-kinase (Rok) rescues the punctate phenotype. Functionally, RN-tre depletion led to an increase in actin retrograde flow rate and cellular contractility in S2 and S2R+ cells, respectively. Regulation of NMII by RN-tre is only partially dependent on its GAP activity as overexpression of constitutively active Rabs inactivated by RN-tre failed to alter NMII RLC localization, while a GAP-dead version of RN-tre partially restored phosphomyosin staining. Collectively, our results suggest that RN-tre plays an important regulatory role in NMII RLC distribution, phosphorylation, and function, likely through Rho1 signaling and putatively serving as a link between the secretion machinery and actomyosin contractility.
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Affiliation(s)
| | - Elizabeth Detmar
- Department of Biology & Integrative Program for Biological and Genome Sciences, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280
| | - Liz Sepulveda
- Department of Biology, Reed College, Portland, OR 97202
| | - Anna Ritz
- Department of Biology, Reed College, Portland, OR 97202
| | - Stephen L Rogers
- Department of Biology & Integrative Program for Biological and Genome Sciences, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280
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7
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Cao Y, Lei Y, Luo Y, Tan T, Du B, Zheng Y, Sun L, Liang Q. The actomyosin network is influenced by NMHC IIA and regulated by Crp F46, which is involved in controlling cell migration. Exp Cell Res 2018; 373:119-131. [PMID: 30336116 DOI: 10.1016/j.yexcr.2018.10.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2018] [Revised: 10/08/2018] [Accepted: 10/09/2018] [Indexed: 10/28/2022]
Abstract
When a cell migrates, the centrosome positions between the nucleus and the leading edge of migration via the microtubule system. The protein CrpF46 (centrosome-related protein F46) has a known role during mitosis and centrosome duplication. However, how CrpF46 efficiently regulates centrosome-related cell migration is unclear. Here, we report that knockdown of CrpF46 resulted in the disruption of microtubule arrangement, with impaired centrosomal reorientation, and slowed down cell migration. In cells that express low levels of CrpF46, stress fibers were weakened, which could be rescued by recovering Flag-CrpF46. We also found that CrpF46 interacted with non-muscle myosin high chain IIA (NMHC IIA) and that its three coiled-coil domains are pivotal for its binding to NMHC IIA. Additionally, analyses of phosphorylation of NMHC IIA and RLC (regulatory light chain) demonstrated that CrpF46 was associated with myosin IIA during filament formation. Indirect immunofluorescence images indicated that NM IIA filaments were inhibited when CrpF46 was under-expressed. Thus, CrpF46 regulates cell migration by centrosomal reorientation and altering the function of the actomyosin network by controlling specific phosphorylation of myosin.
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Affiliation(s)
- Yang Cao
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing 100875, PR China; Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education, College of Life Sciences, Beijing Normal University, Beijing 100875, PR China
| | - Yan Lei
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing 100875, PR China; Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education, College of Life Sciences, Beijing Normal University, Beijing 100875, PR China
| | - Yang Luo
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing 100875, PR China
| | - Tan Tan
- School of Pharmacology and Biology, University of South China, Hunan Province Cooperative innovation Center for Molecular Target New Drug Study, Hengyang 421001, PR China
| | - Baochen Du
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing 100875, PR China
| | - Yanbo Zheng
- The Institute of Medical Biotechnology (IMB) of the Chinese Academy of Medical Sciences, Beijing 100050, PR China
| | - Le Sun
- AbMax Biotechnology Co., Beijing 101111, PR China
| | - Qianjin Liang
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing 100875, PR China; Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education, College of Life Sciences, Beijing Normal University, Beijing 100875, PR China.
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8
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Takeya K, Kaneko T, Miyazu M, Takai A. Addition of urea and thiourea to electrophoresis sample buffer improves efficiency of protein extraction from TCA/acetone-treated smooth muscle tissues for phos-tag SDS-PAGE. Electrophoresis 2017; 39:326-333. [PMID: 29072784 DOI: 10.1002/elps.201700394] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Accepted: 10/18/2017] [Indexed: 01/04/2023]
Abstract
Phosphorylation analysis by using phos-tag technique has been reported to be suitable for highly sensitive quantification of smooth muscle myosin regulatory light chain (LC20 ) phosphorylation. However, there is another factor that will affect the sensitivity of phosphorylation analysis, that is, protein extraction. Here, we optimized the conditions for total protein extraction out of trichloroacetic acid (TCA)-fixed tissues. Standard SDS sample buffer extracted less LC20 , actin and myosin phosphatase targeting subunit 1 (MYPT1) from TCA/acetone treated ciliary muscle strips. On the other hand, sample buffer containing urea and thiourea in addition to lithium dodecyl sulfate (LDS) or SDS extracted those proteins more efficiently, and thus increased the detection sensitivity up to 4-5 fold. Phos-tag SDS-PAGE separated dephosphorylated and phosphorylated LC20 s extracted in LDS/urea/thiourea sample buffer to the same extent as those in standard SDS buffer. We have concluded that LDS (or SDS) /urea/thiourea sample buffer is suitable for highly sensitive phosphorylation analysis in smooth muscle, especially when it is treated with TCA/acetone.
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Affiliation(s)
- Kosuke Takeya
- Department of Physiology, Asahikawa Medical University, Hokkaido, Japan
| | - Toshiyuki Kaneko
- Department of Physiology, Asahikawa Medical University, Hokkaido, Japan
| | - Motoi Miyazu
- Department of Physiology, Asahikawa Medical University, Hokkaido, Japan
| | - Akira Takai
- Department of Physiology, Asahikawa Medical University, Hokkaido, Japan
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9
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Takeya K. Highly sensitive myosin phosphorylation analysis in the renal afferent arteriole. J Smooth Muscle Res 2017; 52:45-55. [PMID: 27375035 PMCID: PMC5137254 DOI: 10.1540/jsmr.52.45] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The regulation of smooth muscle contraction and relaxation involves phosphorylation and
dephosphorylation of regulatory proteins, particularly myosin. To elucidate the regulatory
mechanisms, analyzing the phosphorylation signal transduction is crucial. Although a
pharmacological approach with selective inhibitors is sensitive and a useful technique, it
leads to speculation regarding a signaling pathway but does not provide direct evidence of
changes at a molecular level. We developed a highly sensitive biochemical technique to
analyze phosphorylation by adapting Phos-tag SDS-PAGE. With this technique, we
successfully analyzed myosin light chain (LC20) phosphorylation in tiny renal
afferent arterioles. In the rat afferent arterioles, endothelin-1 (ET-1) induced
diphosphorylation of LC20 at Ser19 and Thr18 as well as monophosphorylation at
Ser19 via ETB receptor activation. Considering that LC20
diphosphorylation can decrease the rate of dephosphorylation and thus relaxation, we
concluded that LC20 diphosphorylation contributes, at least in part, to the
prolonged contraction induced by ET-1 in the renal afferent arteriole.
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Affiliation(s)
- Kosuke Takeya
- Department of Physiology, Asahikawa Medical University, Hokkaido, Japan
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10
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Pfister K, Shook DR, Chang C, Keller R, Skoglund P. Molecular model for force production and transmission during vertebrate gastrulation. Development 2016; 143:715-27. [PMID: 26884399 DOI: 10.1242/dev.128090] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Vertebrate embryos undergo dramatic shape changes at gastrulation that require locally produced and anisotropically applied forces, yet how these forces are produced and transmitted across tissues remains unclear. We show that depletion of myosin regulatory light chain (RLC) levels in the embryo blocks force generation at gastrulation through two distinct mechanisms: destabilizing the myosin II (MII) hexameric complex and inhibiting MII contractility. Molecular dissection of these two mechanisms demonstrates that normal convergence force generation requires MII contractility and we identify a set of molecular phenotypes correlated with both this failure of convergence force generation in explants and of blastopore closure in whole embryos. These include reduced rates of actin movement, alterations in C-cadherin dynamics and a reduction in the number of polarized lamellipodia on intercalating cells. By examining the spatial relationship between C-cadherin and actomyosin we also find evidence for formation of transcellular linear arrays incorporating these proteins that could transmit mediolaterally oriented tensional forces. These data combine to suggest a multistep model to explain how cell intercalation can occur against a force gradient to generate axial extension forces. First, polarized lamellipodia extend mediolaterally and make new C-cadherin-based contacts with neighboring mesodermal cell bodies. Second, lamellipodial flow of actin coalesces into a tension-bearing, MII-contractility-dependent node-and-cable actin network in the cell body cortex. And third, this actomyosin network contracts to generate mediolateral convergence forces in the context of these transcellular arrays.
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Affiliation(s)
- Katherine Pfister
- Biology Department, University of Virginia, Charlottesville, VA 22903, USA
| | - David R Shook
- Biology Department, University of Virginia, Charlottesville, VA 22903, USA
| | - Chenbei Chang
- Department of Cell Biology, University of Alabama, Birmingham, AL 35294, USA
| | - Ray Keller
- Biology Department, University of Virginia, Charlottesville, VA 22903, USA
| | - Paul Skoglund
- Biology Department, University of Virginia, Charlottesville, VA 22903, USA
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11
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Abstract
The myosin holoenzyme is a multimeric protein complex consisting of heavy chains and light chains. Myosin light chains are calmodulin family members which are crucially involved in the mechanoenzymatic function of the myosin holoenzyme. This review examines the diversity of light chains within the myosin superfamily, discusses interactions between the light chain and the myosin heavy chain as well as regulatory and structural functions of the light chain as a subunit of the myosin holoenzyme. It covers aspects of the myosin light chain in the localization of the myosin holoenzyme, protein-protein interactions and light chain binding to non-myosin binding partners. Finally, this review challenges the dogma that myosin regulatory and essential light chain exclusively associate with conventional myosin heavy chains while unconventional myosin heavy chains usually associate with calmodulin.
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Affiliation(s)
- Sarah M Heissler
- a Laboratory of Molecular Physiology; National Heart, Lung, and Blood Institute; National Institutes of Health ; Bethesda , MD USA
| | - James R Sellers
- a Laboratory of Molecular Physiology; National Heart, Lung, and Blood Institute; National Institutes of Health ; Bethesda , MD USA
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12
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Heissler SM, Sellers JR. Kinetic Adaptations of Myosins for Their Diverse Cellular Functions. Traffic 2016; 17:839-59. [PMID: 26929436 DOI: 10.1111/tra.12388] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Revised: 02/25/2016] [Accepted: 02/25/2016] [Indexed: 12/18/2022]
Abstract
Members of the myosin superfamily are involved in all aspects of eukaryotic life. Their function ranges from the transport of organelles and cargos to the generation of membrane tension, and the contraction of muscle. The diversity of physiological functions is remarkable, given that all enzymatically active myosins follow a conserved mechanoenzymatic cycle in which the hydrolysis of ATP to ADP and inorganic phosphate is coupled to either actin-based transport or tethering of actin to defined cellular compartments. Kinetic capacities and limitations of a myosin are determined by the extent to which actin can accelerate the hydrolysis of ATP and the release of the hydrolysis products and are indispensably linked to its physiological tasks. This review focuses on kinetic competencies that - together with structural adaptations - result in myosins with unique mechanoenzymatic properties targeted to their diverse cellular functions.
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Affiliation(s)
- Sarah M Heissler
- Laboratory of Molecular Physiology, National Heart, Lung, and Blood Institute, National Institutes of Health, 50 South Drive, B50/3523, Bethesda, MD 20892-8015, USA
| | - James R Sellers
- Laboratory of Molecular Physiology, National Heart, Lung, and Blood Institute, National Institutes of Health, 50 South Drive, B50/3523, Bethesda, MD 20892-8015, USA
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13
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Heissler SM, Sellers JR. Various Themes of Myosin Regulation. J Mol Biol 2016; 428:1927-46. [PMID: 26827725 DOI: 10.1016/j.jmb.2016.01.022] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Revised: 01/12/2016] [Accepted: 01/19/2016] [Indexed: 10/24/2022]
Abstract
Members of the myosin superfamily are actin-based molecular motors that are indispensable for cellular homeostasis. The vast functional and structural diversity of myosins accounts for the variety and complexity of the underlying allosteric regulatory mechanisms that determine the activation or inhibition of myosin motor activity and enable precise timing and spatial aspects of myosin function at the cellular level. This review focuses on the molecular basis of posttranslational regulation of eukaryotic myosins from different classes across species by allosteric intrinsic and extrinsic effectors. First, we highlight the impact of heavy and light chain phosphorylation. Second, we outline intramolecular regulatory mechanisms such as autoinhibition and subsequent activation. Third, we discuss diverse extramolecular allosteric mechanisms ranging from actin-linked regulatory mechanisms to myosin:cargo interactions. At last, we briefly outline the allosteric regulation of myosins with synthetic compounds.
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Affiliation(s)
- Sarah M Heissler
- Laboratory of Molecular Physiology, National Heart, Lung and Blood Institute, National Institutes of Health, 50 South Drive, B50/3529, Bethesda, MD 20892-8015, USA.
| | - James R Sellers
- Laboratory of Molecular Physiology, National Heart, Lung and Blood Institute, National Institutes of Health, 50 South Drive, B50/3529, Bethesda, MD 20892-8015, USA
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14
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Haldeman BD, Brizendine RK, Facemyer KC, Baker JE, Cremo CR. The kinetics underlying the velocity of smooth muscle myosin filament sliding on actin filaments in vitro. J Biol Chem 2015; 289:21055-70. [PMID: 24907276 DOI: 10.1074/jbc.m114.564740] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Actin-myosin interactions are well studied using soluble myosin fragments, but little is known about effects of myosin filament structure on mechanochemistry. We stabilized unphosphorylated smooth muscle myosin (SMM) and phosphorylated smooth muscle myosin (pSMM) filaments against ATP-induced depolymerization using a cross-linker and attached fluorescent rhodamine (XL-Rh-SMM). Electron micrographs showed that these side polar filaments are very similar to unmodified filaments. They are ~0.63 μm long and contain ~176 molecules. Rate constants for ATP-induced dissociation and ADP release from acto-myosin for filaments and S1 heads were similar. Actin-activated ATPases of SMM and XL-Rh-SMM were similarly regulated. XL-Rh-pSMM filaments moved processively on F-actin that was bound to a PEG brush surface. ATP dependence of filament velocities was similar to that for solution ATPases at high [actin], suggesting that both processes are limited by the same kinetic step (weak to strong transition) and therefore are attachment- limited. This differs from actin sliding over myosin monomers, which is primarily detachment-limited. Fitting filament data to an attachment-limited model showed that approximately half of the heads are available to move the filament, consistent with a side polar structure. We suggest the low stiffness subfragment 2 (S2) domain remains unhindered during filament motion in our assay. Actin-bound negatively displaced heads will impart minimal drag force because of S2 buckling. Given the ADP release rate, the velocity, and the length of S2, these heads will detach from actin before slack is taken up into a backwardly displaced high stiffness position. This mechanism explains the lack of detachment- limited kinetics at physiological [ATP]. These findings address how nonlinear elasticity in assemblies of motors leads to efficient collective force generation.
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15
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Guzik-Lendrum S, Heissler SM, Billington N, Takagi Y, Yang Y, Knight PJ, Homsher E, Sellers JR. Mammalian myosin-18A, a highly divergent myosin. J Biol Chem 2013; 288:9532-48. [PMID: 23382379 DOI: 10.1074/jbc.m112.441238] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The Mus musculus myosin-18A gene is expressed as two alternatively spliced isoforms, α and β, with reported roles in Golgi localization, in maintenance of cytoskeleton, and as receptors for immunological surfactant proteins. Both myosin-18A isoforms feature a myosin motor domain, a single predicted IQ motif, and a long coiled-coil reminiscent of myosin-2. The myosin-18Aα isoform, additionally, has an N-terminal PDZ domain. Recombinant heavy meromyosin- and subfragment-1 (S1)-like constructs for both myosin-18Aα and -18β species were purified from the baculovirus/Sf9 cell expression system. These constructs bound both essential and regulatory light chains, indicating an additional noncanonical light chain binding site in the neck. Myosin-18Aα-S1 and -18Aβ-S1 molecules bound actin weakly with Kd values of 4.9 and 54 μm, respectively. The actin binding data could be modeled by assuming an equilibrium between two myosin conformations, a competent and an incompetent form to bind actin. Actin binding was unchanged by presence of nucleotide. Both myosin-18A isoforms bound N-methylanthraniloyl-nucleotides, but the rate of ATP hydrolysis was very slow (<0.002 s(-1)) and not significantly enhanced by actin. Phosphorylation of the regulatory light chain had no effect on ATP hydrolysis, and neither did the addition of tropomyosin or of GOLPH3, a myosin-18A binding partner. Electron microscopy of myosin-18A-S1 showed that the lever is strongly angled with respect to the long axis of the motor domain, suggesting a pre-power stroke conformation regardless of the presence of ATP. These data lead us to conclude that myosin-18A does not operate as a traditional molecular motor in cells.
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Affiliation(s)
- Stephanie Guzik-Lendrum
- Laboratory of Molecular Physiology, NHLBI, National Institutes of Health, Bethesda, MD 20892-8015, USA
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16
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Liou YM, Watanabe M, Yumoto M, Ishiwata S. Regulatory mechanism of smooth muscle contraction studied with gelsolin-treated strips of taenia caeci in guinea pig. Am J Physiol Cell Physiol 2009; 296:C1024-33. [DOI: 10.1152/ajpcell.00565.2008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
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.
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17
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Mizutani T, Haga H, Kato K, Kawabata K. Wide range scanning probe microscopy for probing mechanical effects on cellular function. ARCHIVES OF HISTOLOGY AND CYTOLOGY 2009; 72:235-43. [PMID: 21471658 DOI: 10.1679/aohc.72.235] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Scanning probe microscopy (SPM) provides a range of strategies for studying biological phenomena due to its ability to image surfaces under liquids. However, some cellular events, such as cell migration, exceed the maximum measurable range of SPM. Recently, we have developed a wide range scanning probe microscope (WR-SPM) to investigate cellular events which exceed the range of the conventional SPM. In this review, we introduce the instrumentation of the WR-SPM, which can measure a sample for 400 µm in the xy directions and 23 µm in the z direction. We then show the application of the WR-SPM to studies of the stiffness response of epithelial cells to an external loading force and demonstrat that the stiffness of the epithelial cells increases under stretched conditions. We also showed the results on the mesh structure on the surface of a melanoma cell as well as the regulatory mechanism of the cellular contractile force by the combined use of topographical and mechanical modes of the WR-SPM. These findings indicate that the WR-SPM is very useful for studying the functions of a cell in relation to the surface structure and mechanical properties of that cell.
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Affiliation(s)
- Takeomi Mizutani
- Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo, Japan.
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18
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Hashimoto M, Matsui T, Iwabuchi K, Date T. PKU-beta/TLK1 regulates myosin II activities, and is required for accurate equaled chromosome segregation. Mutat Res 2008; 657:63-67. [PMID: 18838128 DOI: 10.1016/j.mrgentox.2008.09.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2008] [Accepted: 09/05/2008] [Indexed: 05/26/2023]
Abstract
Tousled-like kinase 1 (or protein kinase ubiquitous, PKU-beta/TLK1) is a serine/threonine protein kinase that is implicated in chromatin remodeling, DNA replication and mitosis. RNAi-mediated PKU-beta/TLK1-depleted human cells showed aneuploidy, and immunofluorescence analysis of these cells revealed the unequal segregation of daughter chromosomes. Immunoblots indicated a substantial reduction in the phosphorylation level of Ser19/Thr18 on the myosin II regulatory light chain (MRLC) in PKU-beta/TLK1-depleted cells, with no change in total MRLC protein. To confirm the relationship between mitotic aberration and MRLC dysfunction, we expressed wild type MRLC or DD-MRLC (mimics diphosphorylation; substitution of both Thr18 and Ser19 with aspartate) in PKU-beta/TLK1-depleted cells. DD-MRLC expression dramatically reduced the unequal segregation of chromosomes. Our data suggest that human PKU-beta/TLK1 plays an important role in chromosome integrity via the regulation of myosin II dynamics by phosphorylating MRLC during mitosis.
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Affiliation(s)
- Mitsumasa Hashimoto
- Department of Biochemistry, Kanazawa Medical University, Uchinada 920-0293, Japan.
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19
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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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20
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Folding and regulation in myosins II and V. J Muscle Res Cell Motil 2008; 28:363-70. [PMID: 18427938 DOI: 10.1007/s10974-008-9134-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2007] [Accepted: 03/04/2008] [Indexed: 10/22/2022]
Abstract
The enzymatic activity of many myosins is regulated by various means including calcium binding, phosphorylation or binding of receptor molecules. In this review we compare and contrast the regulation of smooth muscle myosin II and myosin Va with particular emphasis on the structural basis for the regulation. Both myosins adopt folded compact conformations in their off states, but the details of the conformations are markedly different. In the regulated smooth muscle myosin II, the key feature is an asymmetric interaction between the two heads of the molecule with contributions of specific tail-head interactions. In myosin V the key feature is an interaction between the heads and the globular tail domain.
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21
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Abstract
The study tested the hypothesis that estrogen controls epithelial paracellular resistance through modulation of myosin. The objective was to understand how estrogen modulates nonmuscle myosin-II-B (NMM-II-B), the main component of the cortical actomyosin in human epithelial cervical cells. Experiments used human cervical epithelial cells CaSki as a model, and end points were NMM-II-B phosphorylation, filamentation, and MgATPase activity. The results were as follows: 1) treatment with estrogen increased phosphorylation and MgATPase activity and decreased NMM-II-B filamentation; 2) estrogen effects could be blocked by antisense nucleotides for the estrogen receptor-alpha and by ICI-182,780, tamoxifen, and the casein kinase-II (CK2) inhibitor, 5,6-dichloro-1-beta-(D)-ribofuranosylbenzimidazole and attenuated by AG1478 and PD98059 (inhibitors of epithelial growth factor receptor and ERK/MAPK) but not staurosporine [blocker of protein kinase C (PKC)]; 3) treatments with the PKC activator sn-1,2-dioctanoyl diglyceride induced biphasic effect on NMM-II-B MgATPase activity: an increase at 1 nm to 1 microM and a decrease in activity at more than 1 microM; 4) sn-1,2-dioctanoyl diglyceride also decreased NMM-II-B filamentation in a monophasic and saturable dose dependence (EC(50) 1-10 microM); 5) when coincubated directly with purified NMM-II-B filaments, both CK2 and PKC decreased filamentation and increased MgATPase activity; 6) assays done on disassembled NMM-II-B filaments showed MgATPase activity in filaments obtained from estrogen-treated cells but not estrogen-depleted cells; and 7) incubations in vitro with CK2, but not PKC, facilitated MgATPase activity, even in disassembled NMM-II-B filaments. The results suggest that estrogen, in an effect mediated by estrogen receptor-alpha and CK2 and involving the epithelial growth factor receptor and ERK/MAPK cascades, increases NMM-II-B MgATPase activity independent of NMM-II-B filamentation status.
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Affiliation(s)
- George I Gorodeski
- Department of Reproductive Biology, Case Western Reserve University, Cleveland, Ohio 44106, USA.
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22
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Salzameda B, Facemyer KC, Beck BW, Cremo CR. The N-terminal lobes of both regulatory light chains interact with the tail domain in the 10 S-inhibited conformation of smooth muscle myosin. J Biol Chem 2006; 281:38801-11. [PMID: 17012238 DOI: 10.1074/jbc.m606555200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In the presence of ATP, unphosphorylated smooth muscle myosin can form a catalytically inactive monomer that sediments at 10 Svedbergs (10 S). The tail of 10 S bends into thirds and interacts with the regulatory domain. ADP-P(i) is "trapped" at the active site, and consequently the ATPase activity is extremely low. We are interested in the structural basis for maintenance of this off state. Our prior photocross-linking work with 10 S showed that tail residues 1554-1583 are proximal to position 108 in the C-terminal lobe of one of the two regulatory light chains ( Olney, J. J., Sellers, J. R., and Cremo, C. R. (1996) J. Biol. Chem. 271, 20375-20384 ). These data suggested that the tail interacts with only one of the two regulatory light chains. Here we present data, using a photocross-linker on position 59 on the N-terminal lobe of the regulatory light chain (RLC), demonstrating that both regulatory light chains of a single molecule can cross-link to the light meromyosin portion of the tail. Mass spectrometric data show four specific cross-linked regions spanning residues 1428-1571 in the light meromyosin portion of the tail, consistent with cross-linking two RLC to one light meromyosin. In addition, we find that position 59 can cross-link internally to residues 42-45 within the same RLC subunit. The internal cross-link only forms in 10 S and not in unphosphorylated heavy meromyosin (lacking the light meromyosin), suggesting a structural rearrangement within the RLC attributed to the interaction of the tail with the head.
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Affiliation(s)
- Bridget Salzameda
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Nevada, 1664 N. Virginia Street, Reno, NV 89557, USA
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23
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Rovner AS, Fagnant PM, Trybus KM. Phosphorylation of a single head of smooth muscle myosin activates the whole molecule. Biochemistry 2006; 45:5280-9. [PMID: 16618116 PMCID: PMC2505275 DOI: 10.1021/bi060154c] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Regulatory light chain (RLC) phosphorylation activates smooth and non-muscle myosin II, but it has not been established if phosphorylation of one head turns on the whole molecule. Baculovirus expression and affinity chromatography were used to isolate heavy meromyosin (HMM) containing one phosphorylated and one dephosphorylated RLC (1-P HMM). Motility and steady-state ATPase assays indicated that 1-P HMM is nearly as active as HMM with two phosphorylated heads (2-P HMM). Single-turnover experiments further showed that both the dephosphorylated and phosphorylated heads of 1-P HMM can be activated by actin. Singly phosphorylated full-length myosin was also an active species with two cycling heads. Our results suggest that phosphorylation of one RLC abolishes the asymmetric inhibited state formed by dephosphorylated myosin [Liu, J., et al. (2003) J. Mol. Biol. 329, 963-972], allowing activation of both the phosphorylated and dephosphorylated heads. These findings help explain how smooth muscles are able to generate high levels of stress with low phosphorylation levels.
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Affiliation(s)
- Arthur S Rovner
- Department of Molecular Physiology and Biophysics, Health Sciences Research Facility, University of Vermont, Burlington, Vermont 05405-0068, USA
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24
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Mizutani T, Haga H, Koyama Y, Takahashi M, Kawabata K. Diphosphorylation of the myosin regulatory light chain enhances the tension acting on stress fibers in fibroblasts. J Cell Physiol 2006; 209:726-31. [PMID: 16924661 DOI: 10.1002/jcp.20773] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Regulation of the contractile force is crucial for cell migration, cell proliferation, and maintenance of cell morphology. Phosphorylation of the myosin II regulatory light chain (MRLC) is involved in these processes. To show whether the diphosphorylation of MRLC increases the tension acting on stress fibers, changes in the stiffness of fibroblasts expressing wild-type MRLC and a mutant type, which cannot be diphosphorylated, on treatment with lysophosphatidic acid (LPA) were examined by a mechanical-scanning probe microscope (M-SPM). The LPA treatment increased cellular stiffness in the wild-type MRLC expressing cells, while it had no effect on the mutated cells. Immunostaining showed that LPA stimulation induced the diphosphorylation of MRLC. These results suggest that the diphosphorylation of MRLC enhances the tension acting on stress fibers.
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Affiliation(s)
- Takeomi Mizutani
- Division of Biological Sciences, Graduate School of Science, Hokkaido University, Kita-ku, Sapporo 060-0810, Japan.
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25
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Tama F, Feig M, Liu J, Brooks CL, Taylor KA. The requirement for mechanical coupling between head and S2 domains in smooth muscle myosin ATPase regulation and its implications for dimeric motor function. J Mol Biol 2005; 345:837-54. [PMID: 15588830 DOI: 10.1016/j.jmb.2004.10.084] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2004] [Revised: 10/28/2004] [Accepted: 10/28/2004] [Indexed: 10/26/2022]
Abstract
A combination of experimental structural data, homology modelling and elastic network normal mode analysis is used to explore how coupled motions between the two myosin heads and the dimerization domain (S2) in smooth muscle myosin II determine the domain movements required to achieve the inhibited state of this ATP-dependent molecular motor. These physical models rationalize the empirical requirement for at least two heptads of non-coiled alpha-helix at the junction between the myosin heads and S2, and the dependence of regulation on S2 length. The results correlate well with biochemical data regarding altered conformational-dependent solubility and stability. Structural models of the conformational transition between putative active states and the inhibited state show that torsional flexibility of the S2 alpha-helices is a key mechanical requirement for myosin II regulation. These torsional motions of the myosin heads about their coiled coil alpha-helices affect the S2 domain structure, which reciprocally affects the motions of the myosin heads. This inter-relationship may explain a large body of data on function of molecular motors that form dimers through a coiled-coil domain.
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Affiliation(s)
- Florence Tama
- Department of Molecular Biology, TPC6, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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26
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Formigli L, Meacci E, Vassalli M, Nosi D, Quercioli F, Tiribilli B, Tani A, Squecco R, Francini F, Bruni P, Zecchi Orlandini S. Sphingosine 1-phosphate induces cell contraction via calcium-independent/Rho-dependent pathways in undifferentiated skeletal muscle cells. J Cell Physiol 2003; 198:1-11. [PMID: 14584038 DOI: 10.1002/jcp.10366] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We have previously shown that sphingosine 1-phosphate (S1P) can induce intracellular Ca(2+) mobilization and cell contraction in C2C12 myoblasts and that the two phenomena are temporally unrelated. Although Ca(2+)-independent mechanisms of cell contraction have been the focus of numerous studies on Ca(2+) sensitization of smooth muscle, comparatively less studies have focused on the role that these mechanisms play in the regulation of skeletal muscle contractility. Phosphorylation and activation of myosin by Rho-dependent kinase mediate most of Ca(2+)-independent contractile responses. In the present study, we examined the potential role of Rho/Rho-kinase cascade activation in S1P-induced C2C12 cell contraction. First, we showed that depletion of Ca(2+), by pre-treatment with BAPTA, did not affect S1P-induced myoblastic contractility, whereas it abolished S1P-induced Ca(2+) transients. These results correlated with the absence of troponin C and with the immature cytoskeletal organization of these cells. Experimental evidence demonstrating the involvement of Rho pathway in S1P-stimulated myoblast contraction included: the activation/translocation of RhoA to the membrane in response to agonist-stimulation in cells depleted of Ca(2+) and the inhibition of dynamic changes of the actin cytoskeleton in cells where Rho functions had been inhibited either by overexpression of RhoGDI, a physiological inhibitor of GDP dissociation from Rho proteins, or by pretreatment with Y-27632, a specific Rho kinase inhibitor. Contribution of protein kinase C in this cytoskeletal rearrangement was also evaluated. However, the pretreatment with Gö6976 or rottlerin, specific inhibitors of PKC alpha and PKC delta, respectively, failed to inhibit the agonist-induced myoblastic contraction. Single particle tracking of G-actin fluorescent probe was performed to statistically evaluate actin cytoskeletal dynamics in response to S1P. Stimulation with S1P was also able to increase the phosphorylation level of myosin light chain II. In conclusion, our results strongly suggest that Ca(2+)-independent/Rho-Rho kinase-dependent pathways may exert an important role in S1P-induced myoblastic cell contraction.
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Affiliation(s)
- L Formigli
- Department of Anatomy, Histology, Forensic Medicine, University of Florence, Italy
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27
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Ueda K, Murata-Hori M, Tatsuka M, Hosoya H. Rho-kinase contributes to diphosphorylation of myosin II regulatory light chain in nonmuscle cells. Oncogene 2002; 21:5852-60. [PMID: 12185584 DOI: 10.1038/sj.onc.1205747] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2002] [Revised: 05/31/2002] [Accepted: 06/07/2002] [Indexed: 11/09/2022]
Abstract
Phosphorylation of myosin II regulatory light chain (MRLC) is important for cell motility and cytokinesis in nonmuscle cells. Although the regulation of monophosphorylated MRLC at serine 19 throughout the cell cycle was examined in detail, MRLC diphosphorylation at both threonine 18 and serine 19 is still unclear. Here we found that Rho-kinase has an activity for MRLC diphosphorylation in nonmuscle cells using sequential column chromatographies. Transfection of Rho-kinase-EGFP induced the excess diphosphorylated MRLC and the bundling of the actin filaments. Conversely, the treatment of cells with a specific inhibitor of Rho-kinase, Y-27632, resulted in the decrease of endogenous diphosphorylated MRLC and actin stress fibers. Immunolocalization studies showed that both diphosphorylated MRLC and Rho-kinase accumulated and colocalized at the contractile ring and the midbody in dividing cells. Taken together, it is suggested that Rho-kinase contributes to MRLC diphosphorylation and reorganization of actin filaments in nonmuscle cells.
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Affiliation(s)
- Kozue Ueda
- Department of Biological Science, Graduate School of Science, Hiroshima University, Higashi-Hiroshima, 739-8526, Japan
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28
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Zhang H, Wessels D, Fey P, Daniels K, Chisholm RL, Soll DR. Phosphorylation of the myosin regulatory light chain plays a role in motility and polarity duringDictyosteliumchemotaxis. J Cell Sci 2002; 115:1733-47. [PMID: 11950890 DOI: 10.1242/jcs.115.8.1733] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The myosin regulatory light chain (RLC) of Dictyostelium discoideum is phosphorylated at a single serine site in response to chemoattractant. To investigate the role of the phosphorylation of RLC in both motility and chemotaxis, mutants were generated in which the single phosphorylatable serine was replaced with a nonphosphorylatable alanine. Several independent clones expressing the mutant RLC in the RLC null mutant, mlcR-, were obtained. These S13A mutants were subjected to high resolution computer-assisted motion analysis to assess the basic motile behavior of cells in the absence of a chemotatic signal, and the chemotactic responsiveness of cells to the spatial, temporal and concentration components of natural cAMP waves. In the absence of a cAMP signal, mutant cells formed lateral pseudopods less frequently and crawled faster than wild-type cells. In a spatial gradient of cAMP, mutant cells chemotaxed more efficiently than wild-type cells. In the front of simulated temporal and natural waves of cAMP,mutant cells responded normally by suppressing lateral pseudopod formation. However, unlike wild-type cells, mutant cells did not lose cellular polarity at the peak and in the back of either wave. Since depolarization at the peak and in the descending phase of the natural wave is necessary for efficient chemotaxis, this deficiency resulted in a decrease in the capacity of S13A mutant cells to track natural cAMP waves relayed by wild-type cells, and in the fragmentation of streams late in mutant cell aggregation. These results reveal a regulatory pathway induced by the peak and back of the chemotactic wave that alters RLC phosphorylation and leads to cellular depolarization. We suggest that depolarization requires myosin II rearrangement in the cortex facilitated by RLC phosphorylation, which increases myosin motor function.
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Affiliation(s)
- Hui Zhang
- Department of Biological Sciences, University of Iowa, Iowa City, Iowa 52242, USA
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29
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Cremo CR, Wang F, Facemyer K, Sellers JR. Phosphorylation-dependent regulation is absent in a nonmuscle heavy meromyosin construct with one complete head and one head lacking the motor domain. J Biol Chem 2001; 276:41465-72. [PMID: 11517231 DOI: 10.1074/jbc.m107103200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To understand the domain requirements of phosphorylation-dependent regulation, we prepared three recombinant constructs of nonmuscle heavy meromyosin IIB containing 1) two complete heads, 2) one complete head and one head lacking the motor domain, and 3) one complete head and one head lacking both motor and regulatory domains. Steady-state ATPase measurements showed that phosphorylation did not alter the affinity for actin by more than a factor of 2 for any construct. Phosphorylation increased V(max) by a factor of 10 for construct 1 and 1.5-3 for construct 2 but had no effect for construct 3. Single turnover measurements, a better measure of slow rates inherent to unphosphorylated regulated myosins, showed that the single-headed construct 2, like construct 3 retains less than 1% of the regulatory properties of the double-headed construct 1 (300-fold activation). Therefore, a complete head cannot be down-regulated by a regulatory domain (without the motor domain) on the partner head. Two motor domains are required for regulation. This result is predicted by a structural model (Wendt, T., Taylor, D., Messier, T., Trybus, K. M., and Taylor, K. A. (1999) J. Cell Biol. 147, 1385-1390) showing interaction between the motor domains for unphosphorylated smooth muscle myosin, if motor-motor interaction is the basis for down-regulation.
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Affiliation(s)
- C R Cremo
- Department of Biochemistry, The University of Nevada, Reno, Nevada 89557, USA
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30
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Abstract
Vascular smooth muscle tone is controlled by a balance between the cellular signaling pathways that mediate the generation of force (contraction) and the release of force (relaxation). The signaling events that activate contraction include Ca(2+)-dependent myosin light chain phosphorylation. The signaling events that mediate relaxation include the removal of a contractile agonist (passive relaxation) and activation of cyclic nucleotide-dependent signaling pathways in the continued presence of a contractile agonist (active relaxation). The major questions that remain in contractile physiology include (1) how is tonic force maintained when intracellular Ca(2+) levels and myosin light chain phosphorylation have returned to basal levels; and (2) what is the mechanism of cyclic nucleotide-dependent relaxation? This review focuses on these specific controversies surrounding the molecular mechanisms of contraction and relaxation of vascular smooth muscle.
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Affiliation(s)
- D A Woodrum
- Institute for Molecular Medicine and Genetics, Medical College of Georgia, 1120 15th Street, Augusta, GA, USA
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31
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Halayko AJ, Solway J. Molecular mechanisms of phenotypic plasticity in smooth muscle cells. J Appl Physiol (1985) 2001; 90:358-68. [PMID: 11133929 DOI: 10.1152/jappl.2001.90.1.358] [Citation(s) in RCA: 190] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Morphological, functional, molecular and cell biology studies have revealed a striking multifunctional nature of individual smooth muscle cells (SMC). SMCs manifest phenotypic plasticity in response to changes in environment and functional requirements, acquiring a range of structural and functional properties bounded by two extremes, called "synthetic" and "contractile." Each phenotypic state is characterized by expression of a unique set of structural, contractile, and receptor proteins and isoforms that correlate with differing patterns of gene expression. Recent studies have identified signaling pathways and transcription factors (e.g., RhoA GTPase/ROCK, also known as Rho kinase, and serum response factor) that regulate the transcriptional activities of genes encoding proteins associated with the contractile apparatus. Mechanical plasticity of contractile-state smooth muscle further extends SMC functional diversity. This may also be regulated, in part, by the RhoA GTPase/ROCK pathway, via reorganization of cytoskeletal and contractile proteins. Future studies that define transcriptional and posttranscriptional mechanisms of SMC plasticity are necessary to fully understand the role of SMC in the pathogenesis and morbidity of human diseases of the airways, vasculature, and gastrointestinal tract.
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Affiliation(s)
- A J Halayko
- Department of Physiology and Section of Respiratory Diseases, University of Manitoba, Winnipeg, Manitoba, Canada R3A 1R8.
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32
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Changes in the composition of myosin isoforms in smooth muscle hypertrophy following urinary bladder outlet obstruction. ACTA ACUST UNITED AC 2000. [DOI: 10.1016/s1569-2590(00)08004-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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33
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Liang W, Warrick HM, Spudich JA. A structural model for phosphorylation control of Dictyostelium myosin II thick filament assembly. J Cell Biol 1999; 147:1039-48. [PMID: 10579723 PMCID: PMC2169343 DOI: 10.1083/jcb.147.5.1039] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Myosin II thick filament assembly in Dictyostelium is regulated by phosphorylation at three threonines in the tail region of the molecule. Converting these three threonines to aspartates (3 x Asp myosin II), which mimics the phosphorylated state, inhibits filament assembly in vitro, and 3 x Asp myosin II fails to rescue myosin II-null phenotypes. Here we report a suppressor screen of Dictyostelium myosin II-null cells containing 3 x Asp myosin II, which reveals a 21-kD region in the tail that is critical for the phosphorylation control. These data, combined with new structural evidence from electron microscopy and sequence analyses, provide evidence that thick filament assembly control involves the folding of myosin II into a bent monomer, which is unable to incorporate into thick filaments. The data are consistent with a structural model for the bent monomer in which two specific regions of the tail interact to form an antiparallel tetrameric coiled-coil structure.
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Affiliation(s)
- Wenchuan Liang
- Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305-5307
| | - Hans M. Warrick
- Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305-5307
| | - James A. Spudich
- Department of Biochemistry, Stanford University School of Medicine, Stanford, California 94305-5307
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34
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Hypolite JA, DiSanto ME, Wein AJ, Chacko S. Myosin light chain phosphorylation at resting level and the composition of myosin isoforms in the bladder body and urethra. SCANDINAVIAN JOURNAL OF UROLOGY AND NEPHROLOGY. SUPPLEMENTUM 1999; 201:46-50. [PMID: 10573776 DOI: 10.1080/003655999750042141] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
Bladder filling depends upon the coordinated control of a storage chamber, the bladder body, and its outlet, the bladder base and urethra. Bladder emptying results from development of force in the bladder body and relaxation of the outlet. Muscle strips from bladder body reveal phasic characteristics, whereas the strips from urethral wall are tonic. To determine whether the compositions of myosin heavy chain (MHC) isoforms and the level of myosin light chain (MLC) phosphorylation contribute to the regional variation in the contractile states of the bladder smooth muscle, we analyzed the levels of MLC phosphorylation and the expression of myosin isoforms in smooth muscle tissues from different regions of the urinary bladder. Strips of bladder from the dome, mid body, base of the bladder and urethra were removed and analyzed for the levels of MLC phosphorylation at the resting tone. The expression of MHC isoforms that differ in the C-terminus (SM1 and SM2) and in the N-terminal region (SM-A and SM-B), formed by alternative splicing of the pre-mRNA at either the 3' end or the 5' end, respectively, was analyzed. The expression of these isoforms was characterized at the mRNA and protein levels using reverse transcriptase-polymerase chain reaction (RT-PCR), SDS-PAGE, and Western blotting. The levels of MLC phosphorylation were 35.5 +/- 4.6, 24.7 +/- 2.2, 13.6 +/- 2.1, and 12.8 +/- 2.7 for dome, mid bladder body, base and urethra respectively. Almost 100% of the MHC mRNA in the dome, mid bladder body, and base contains a 7-amino acid insert near the ATP-binding region, whereas the MHC in the urethral smooth muscle is only 81% inserted. Prior studies have shown that inserted myosin has a two-fold higher actin-activated ATPase activity compared to the myosin isoform that lacks the insert, and the maximum velocity of shortening of smooth muscle containing this insert is high compared to muscle that do not contain the insert. The expression of SM1 and SM2 were not significantly different. Our data suggests the presence of a high degree of inserted myosin and LC20 phosphorylation in the bladder dome and mid-body helps to facilitate rapid force development and emptying. Non-inserted myosin and the low level of MLC phosphorylation in the urethra may contribute to slowly or non-cycling myosin cross bridges and the maintenance of a tonic or contracted state during bladder filling.
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Affiliation(s)
- J A Hypolite
- Department of Pathobiology, University of Pennsylvania, Philadelphia 19104, USA
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35
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Woodrum DA, Brophy CM, Wingard CJ, Beall A, Rasmussen H. Phosphorylation events associated with cyclic nucleotide-dependent inhibition of smooth muscle contraction. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:H931-9. [PMID: 10484413 DOI: 10.1152/ajpheart.1999.277.3.h931] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Activation of cyclic nucleotide-dependent signaling pathways leads to relaxation of bovine carotid artery smooth muscle contractions and is associated with increased phosphorylation of the small heat shock-related protein (HSP20). Previous reports have shown that human umbilical artery smooth muscle is uniquely resistant to cyclic nucleotide-dependent relaxation, and HSP20 is not phosphorylated. In this investigation, we determined the phosphorylation events associated with cyclic nucleotide-dependent inhibition of smooth muscle contraction. In carotid artery, activation of cyclic nucleotide-dependent signaling pathways inhibited contractile responses to serotonin but did not inhibit myosin light chain phosphorylation or oxygen consumption. The inhibition of contraction was associated with increases in HSP20 phosphorylation. In umbilical artery, activation of cyclic nucleotide-dependent signaling pathways did not inhibit serotonin-induced contraction or myosin light chain phosphorylation. The lack of contractile inhibition in umbilical artery was not associated with significant increases in HSP20 phosphorylation. In conclusion, cyclic nucleotide-dependent contractile inhibition is independent of the inhibition of myosin light chain phosphorylation or oxygen consumption but does correlate with increased HSP20 phosphorylation.
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Affiliation(s)
- D A Woodrum
- Department of Cell Biology and Anatomy, Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, Georgia 30912, USA
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36
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Murata-Hori M, Suizu F, Iwasaki T, Kikuchi A, Hosoya H. ZIP kinase identified as a novel myosin regulatory light chain kinase in HeLa cells. FEBS Lett 1999; 451:81-4. [PMID: 10356987 DOI: 10.1016/s0014-5793(99)00550-5] [Citation(s) in RCA: 117] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
A novel myosin light chain kinase (MLCK) cDNA was isolated from a HeLa cell cDNA library. The deduced amino acid sequence was identical to that of a zipper-interacting protein kinase (ZIPK) which mediates apoptosis [Kawai et al. (1998) Mol. Cell. Biol. 18, 1642-1651]. Here we found that HeLa ZIPK phosphorylated the regulatory light chain of myosin II (MRLC) at both serine 19 and threonine 18 in a Ca2+/calmodulin independent manner. Phosphorylation of myosin II by HeLa ZIPK resulted in activation of actin-activated MgATPase activity of myosin II. HeLa ZIPK is the first non-muscle MLCK that phosphorylates MRLC at two sites.
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Affiliation(s)
- M Murata-Hori
- Department of Biological Science, Faculty of Science, Hiroshima University, Higashi-Hiroshima, Japan
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37
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Abstract
Phosphorylation of the regulatory light chain subunit of smooth muscle myosin is sufficient, but not necessary for muscle contraction. It has been suggested that thin-filament regulation may also contribute to the regulation of contraction. A hallmark feature of regulated thin filaments, previously described for vertebrate skeletal muscle, is the capacity of strong-binding or rigor-like cross bridges to "turn-on" the actin filament. Turned-on thin filaments stimulate cross-bridge attachment even in the absence of calcium. The present study utilized an in vitro sliding-filament motility assay to test for thin-filament regulation of both unphosphorylated and phosphorylated smooth muscle myosins. Regulated thin-filaments were reconstituted from skeletal muscle actin and chicken gizzard smooth muscle tropomyosin (TmCG), and then turned-on either (1) by rigor cross bridges at low concentrations of MgATP, or (2) by adding N-ethyl-maleimide-modified skeletal subfragment S1(NEM-S1), which forms rigor-like bonds in the presence of MgATP. For control actin.TmCG filaments, force production by unphosphorylated myosin was 0.5% of that produced by thiophosphorylated myosin. The force exerted on actin.Tm filaments by both unphosphorylated and phosphorylated myosins was increased by reducing the [MgATP] to 10-100 microM MgATP (rigor-dependent activation). Force was also increased by actin.TmCG filaments that had been turned-on by NEM-S1 binding, with force production by unphosphorylated myosin increased 80-fold vs. 2.3-fold for thiophosphorylated myosin. TmCG was required for increased force production with both low MgATP and NEM-S1. Unloaded filament velocity for NEM-S1-activated thin filaments was 0.72 micron/sec with unphosphorylated myosin compared to 1.24 microns/sec with thiophosphorylated myosin. Taken together, these results suggest that thin-filament regulation may play a role in the activation of both unphosphorylated and phosphorylated smooth muscle myosins and suggest a possible mechanism for activation of slowly cycling unphosphorylated cross bridges (i.e. latch-state) during tonic contractions of smooth muscle.
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Affiliation(s)
- J R Haeberle
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington 05405-0068, USA.
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38
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Abstract
Meat is the edible muscle tissue of animals. The sarcomere is the fundamental functional unit of muscle. Growth and development of muscle is accomplished by the highly ordered accretion and assembly of the constituent proteins in the sarcomere. Primary amino acid sequence elements of the constitutive proteins carry the information necessary for determining the final architecture of the sarcomere. The mechanisms by which the constitutive proteins are assembled and function together to form the sarcomere and produce muscle contraction is just now beginning to be understood. The predominant protein in the sarcomere, found in the thick filament system, is myosin. In physiological buffers purified myosin spontaneously assembles into a synthetic thick filament with a dramatic resemblance to the native thick filament. Some of the amino acid sequence elements contributing to myosin's assembly properties may also be critical to myosin's solubility function, which is so crucial to the manufacture of high quality prepared meat products. This review summarizes recent experimental results contributing to our understanding of the mechanism of sarcomeric muscle myosin assembly.
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Affiliation(s)
- M Wick
- The Ohio State University, Department of Animal Sciences, Columbus 43210, USA.
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39
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Sellers JR. Unphosphorylated crossbridges and latch: smooth muscle regulation revisited. J Muscle Res Cell Motil 1999; 20:347-9. [PMID: 10531615 DOI: 10.1023/a:1005557724418] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- J R Sellers
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892-1762, USA.
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40
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Chacko S, DiSanto M, Menon C, Zheng Y, Hypolite J, Wein AJ. Contractile Protein Changes in Urinary Bladder Smooth Muscle Following Outlet Obstruction. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1999; 462:137-53. [PMID: 10599420 DOI: 10.1007/978-1-4615-4737-2_11] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/14/2023]
Affiliation(s)
- S Chacko
- Department of Pathobiology, University of Pennsylvania, Philadelphia 19104-4274, USA
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41
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He ZH, Ferenczi MA, Brune M, Trentham DR, Webb MR, Somlyo AP, Somlyo AV. Time-resolved measurements of phosphate release by cycling cross-bridges in portal vein smooth muscle. Biophys J 1998; 75:3031-40. [PMID: 9826623 PMCID: PMC1299974 DOI: 10.1016/s0006-3495(98)77744-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The rate of release of inorganic phosphate (Pi) from cycling cross-bridges in rabbit portal-anterior mesenteric vein smooth muscle was determined by following the fluorescence of the Pi-reporter, MDCC-PBP (Brune, M., J. L. Hunter, S. A. Howell, S. R. Martin, T. L. Hazlett, J. E. T. Corrie, and M. R. Webb. 1998. Biochemistry. 37:10370-10380). Cross-bridge cycling was initiated by photolytic release of ATP from caged-ATP in Triton-permeabilized smooth muscles in rigor. When the regulatory myosin light chains (MLC20) had been thiophosphorylated, the rate of Pi release was biphasic with an initial rate of 80 microM s-1 and amplitude 108 microM, decreasing to 13.7 microM s-1. These rates correspond to fast and slow turnovers of 1.8 s-1 and 0.3 s-1, assuming 84% thiophosphorylation of 52 microM myosin heads. Activation by Ca2+-dependent phosphorylation subsequent to ATP release resulted in slower Pi release, paralleling the rate of contraction that was also slower than after thiophosphorylation, and was also biphasic: 51 microM s-1 and 13.2 microM s-1. These rates suggest that the activity of myosin light chain kinase and phosphatase ("pseudo-ATPase") contributes <20% of the ATP usage during cross-bridge cycling. The extracellular "ecto-nucleotidase" activity was reduced eightfold by permeabilization, conditions in which the ecto-ADPase was 17% of the ecto-ATPase. Nevertheless, the remaining ecto-ATPase activity reduced the precision of the estimate of cross-bridge ATPase. We conclude that the transition from fast to slow ATPase rates reflects the properties and forces directly acting on cross-bridges, rather than the result of a time-dependent decrease in activation (MLC20 phosphorylation) occurring in intact smooth muscle. The mechanisms of slowing may include the effect of positive strain on cross-bridges, inhibition of the cycling rate by high affinity Mg-ADP binding, and associated state hydrolysis.
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Affiliation(s)
- Z H He
- National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, United Kingdom
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42
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Rovner AS. A long, weakly charged actin-binding loop is required for phosphorylation-dependent regulation of smooth muscle myosin. J Biol Chem 1998; 273:27939-44. [PMID: 9774407 DOI: 10.1074/jbc.273.43.27939] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Chimeric substitution of the weak actin-binding loop (ABL) from chicken skeletal muscle myosin for that of gizzard smooth muscle heavy meromyosin (HMM) causes activation of the dephosphorylated mutant (SABL HMM; Rovner, A. S., Freyzon, Y., and Trybus, K. M. (1995) J. Biol. Chem. 270, 30260-30263). The present study determined whether this loss of regulation is due to the greater positive charge density (5 versus 3 clustered lysine residues) or lesser length (14 versus 26 residues) of the mutant ABL. Charge augmentation had little effect on regulation of expressed mutants, but elimination of the 12 N-terminal amino acids from the wild-type ABL significantly increased actin-activated ATPase activity of the dephosphorylated relative to the phosphorylated molecule while conferring the ability to move actin filaments in vitro on the former. Addition of the same 12 residues to the SABL mutant increased the ratio of phosphorylated to dephosphorylated ATPase activity while imparting wild type-like regulation to motility. However, full actin activation of dephosphorylated ATPase activity required both the shorter length and greater positive charge density found in the SABL loop. These results demonstrate that, compared with skeletal, both the greater length and lesser positive charge density of the smooth muscle myosin ABL are required for proper phosphorylation-mediated regulation of the molecule.
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Affiliation(s)
- A S Rovner
- Department of Molecular Physiology and Biophysics, University of Vermont College of Medicine, Burlington, Vermont 05405-0068, USA.
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43
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Ren D, Han S, Yan L. Actin and myosin during pollen germination. CHINESE SCIENCE BULLETIN-CHINESE 1998. [DOI: 10.1007/bf02883579] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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44
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Malmqvist U, Trybus KM, Yagi S, Carmichael J, Fay FS. Slow cycling of unphosphorylated myosin is inhibited by calponin, thus keeping smooth muscle relaxed. Proc Natl Acad Sci U S A 1997; 94:7655-60. [PMID: 9207148 PMCID: PMC23878 DOI: 10.1073/pnas.94.14.7655] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/1996] [Accepted: 04/28/1997] [Indexed: 02/04/2023] Open
Abstract
A key unanswered question in smooth muscle biology is whether phosphorylation of the myosin regulatory light chain (RLC) is sufficient for regulation of contraction, or if thin-filament-based regulatory systems also contribute to this process. To address this issue, the endogenous RLC was extracted from single smooth muscle cells and replaced with either a thiophosphorylated RLC or a mutant RLC (T18A/S19A) that cannot be phosphorylated by myosin light chain kinase. The actin-binding protein calponin was also extracted. Following photolysis of caged ATP, cells without calponin that contained a nonphosphorylatable RLC shortened at 30% of the velocity and produced 65% of the isometric force of cells reconstituted with the thiophosphorylated RLC. The contraction of cells reconstituted with nonphosphorylatable RLC was, however, specifically suppressed in cells that contained calponin. These results indicate that calponin is required to maintain cells in a relaxed state, and that in the absence of this inhibition, dephosphorylated cross-bridges can slowly cycle and generate force. These findings thus provide a possible framework for understanding the development of latch contraction, a widely studied but poorly understood feature of smooth muscle.
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Affiliation(s)
- U Malmqvist
- Biomedical Imaging Group, Department of Physiology, University of Massachusetts Medical School, Worcester, MA 01605, USA
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45
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Murphy RA, Walker JS, Strauss JD. Myosin isoforms and functional diversity in vertebrate smooth muscle. Comp Biochem Physiol B Biochem Mol Biol 1997; 117:51-60. [PMID: 9180014 DOI: 10.1016/s0305-0491(96)00314-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The expression of fast and slow myosin isoforms in individual cells is associated with differences in shortening velocities and power output in fully differentiated vertebrate striated muscle. This paradigm in which shortening velocity is determined by the myosin isoform (and load) is inappropriate for smooth muscle. Smooth muscle tissues express multiple myosin heavy and light chain isoforms, and it is not currently possible to separate and identify chemically distinct native myosin hexamers (i.e., isoforms). It is not known if different isoforms are localized in subpopulations of cells or in specific cellular domains nor whether they combine preferentially to form a small number of native myosin hexamer isoforms. Potentially, thick filaments are aggregates of many different combinations of heavy and light chain isoforms that may or may not exhibit different kinetics. Shortening velocities in smooth muscle are regulated by Ca(2+)-dependent crossbridge phosphorylation of the myosin regulatory light chains. Much of the observed diversity in power output in smooth muscle may be attributed to regulatory mechanisms modulating crossbridge cycling rates rather than contractile protein isoform expression.
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Affiliation(s)
- R A Murphy
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville 22906-0011, USA.
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46
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Sata M, Stafford WF, Mabuchi K, Ikebe M. The motor domain and the regulatory domain of myosin solely dictate enzymatic activity and phosphorylation-dependent regulation, respectively. Proc Natl Acad Sci U S A 1997; 94:91-6. [PMID: 8990166 PMCID: PMC19241 DOI: 10.1073/pnas.94.1.91] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
While the structures of skeletal and smooth muscle myosins are homologous, they differ functionally from each other in several respects, i.e., motor activities and regulation. To investigate the molecular basis for these differences, we have produced a skeletal/smooth chimeric myosin molecule and analyzed the motor activities and regulation of this myosin. The produced chimeric myosin is composed of the globular motor domain of skeletal muscle myosin (Met1-Gly773) and the C-terminal long alpha-helix domain of myosin subfragment 1 as well as myosin subfragment 2 (Gly773-Ser1104) and light chains of smooth muscle myosin. Both the actin-activated ATPase activity and the actin-translocating activity of the chimeric myosin were completely regulated by light chain phosphorylation. On the other hand, the maximum actin-activated ATPase activity of the chimeric myosin was the same as skeletal myosin and thus much higher than smooth myosin. These results show that the C-terminal light chain-associated domain of myosin head solely confers regulation by light chain phosphorylation, whereas the motor domain determines the rate of ATP hydrolysis. This is the first report, to our knowledge, that directly determines the function of the two structurally separated domains in myosin head.
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Affiliation(s)
- M Sata
- Department of Physiology, University of Massachusetts Medical Center, Worcester 01655-0127, USA
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47
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Smith JL, Silveira LA, Spudich JA. Myosin light chain kinase (MLCK) gene disruption in Dictyostelium: a role for MLCK-A in cytokinesis and evidence for multiple MLCKs. Proc Natl Acad Sci U S A 1996; 93:12321-6. [PMID: 8901579 PMCID: PMC37989 DOI: 10.1073/pnas.93.22.12321] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
We have created a strain of Dictyostelium that is deficient for the Ca2+/calmodulin-independent MLCK-A. This strain undergoes cytokinesis less efficiently than wild type, which results in an increased frequency of multinucleate cells when grown in suspension. The MLCK-A-cells are able, however, to undergo development and to cap crosslinked surface receptors, processes that require myosin heavy chain. Phosphorylated regulatory light chain (RLC) is still present in MLCK-A-cells, indicating that Dictyostelium has one or more additional protein kinases capable of phosphorylating RLC. Concanavalin A treatment was found to induce phosphorylation of essentially all of the RLC in wild-type cells, but RLC phosphorylation levels in MLCK-A-cells are unaffected by concanavalin A. Thus MLCK-A is regulated separately from the other MLCK(s) in the cell.
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Affiliation(s)
- J L Smith
- Department of Biochemistry, Beckman Center, Stanford University Medical Center, CA 94305-5307, USA
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48
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Olney JJ, Sellers JR, Cremo CR. Structure and function of the 10 S conformation of smooth muscle myosin. J Biol Chem 1996; 271:20375-84. [PMID: 8702773 DOI: 10.1074/jbc.271.34.20375] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Smooth myosin regulatory light chain (RLC) was exchanged with RLC labeled with benzophenone-4-iodoacetamide at Cys-108. Irradiation under conditions that favor the folded (10 S) conformation resulted in 10 S cross-linked myosin that could not unfold. Purified 10 S cross-linked myosin was cross-linked between the RLC of one head to light meromyosin between leucine 1554 and glutamate 1583, adjacent to a predicted noncoiled region, approximately 60 nm from the tip of the tail. At high ionic strength without actin, product release from one-half of the heads was slow (like 10 S) whereas the other half were activated. This suggests that tail binding to the RLC carboxyl-terminal domain stabilizes ionic interactions important to slow nucleotide release. With actin, product release from both (un)phosphorylated 10 S cross-linked myosin was from one slow population similar to unphosphorylated filaments. 10 S cross-linked myosin weakly bound actin (dissociation constant > 500 microM) and did not move actin in vitro. Single-headed myosin did not fold or trap nucleotide. These and other data suggest that "trapping" occurs only with both heads and the tail binds to a newly formed site, which includes the RLC carboxyl-terminal domain, once trapping has occurred.
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Affiliation(s)
- J J Olney
- Department of Biochemistry and Biophysics, Washington State University, Pullman, Washington 99164-4660, USA
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Royuela M, García-Anchuelo R, Paz de Miguel M, Arenas MI, Fraile B, Paniagua R. Immunocytochemical electron microscopic study and Western blot analysis of troponin in striated muscle of the fruit fly Drosophila melanogaster and in several muscle cell types of the earthworm Eisenia foetida. Anat Rec (Hoboken) 1996; 244:148-54. [PMID: 8808389 DOI: 10.1002/(sici)1097-0185(199602)244:2<148::aid-ar2>3.0.co;2-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
BACKGROUND There is little information about troponin in invertebrate muscles, and no previous references to this protein in annelid muscles have been found. The aim of this paper was to study the presence and distribution of troponin in different muscle cell types from the earthworm Eisenia foetida (the muscular body wall, and the inner and outer muscular layer of the pseudoheart). These results were compared with those obtained in the transversely striated muscle of Drosophila melanogaster and in skeletal and smooth muscles of the mouse. METHODS Immunocytochemical electron microscopic study and Western blot analysis using anti-TnT antibodies were employed in this study. RESULTS Troponin immunoreaction was detected in the mouse skeletal muscle, the fly flight muscle, and earthworm obliquely striated muscles (body wall musculature and inner muscular layer of the pseudoheart). Immunolabeling for TnT in all these muscle cells appeared in moderate amounts at any point along the sarcomere length, except for the central zone of the A band (H band). This suggests that troponin molecules were located along the thin filaments. The density of immunogold particles was similar in the three muscles, and thus the amount of troponin in each muscle type was proportional to the number and length of actin filaments in each. Troponin was found in neither the mouse smooth muscle nor the outer muscular layer of the earthworm pseudoheart. The latter muscle showed an ultrastructural pattern that was intermediate between obliquely striated and smooth muscle. The estimated molecular weight for TnT in the earthworm was 55 kDa; this is higher than the weight of this protein in the mouse skeletal muscle (40 kDa) but similar to that of the D. melanogaster muscle (52 kDa). CONCLUSIONS Troponin is present in both types of striated muscle (transversely striated and obliquely striated) of the earthworm with a distribution that is very similar to that observed in the mammalian striated muscle. As in vertebrates, troponin is absent in the smooth muscle of the earthworm. Discrepancies in the classification of some invertebrate muscles are common in the literature, and the use of distinctive markers, such as troponin, may improve our understanding of the nature and properties of many invertebrate muscles showing an ultrastructural pattern that does not resemble any of the classic muscle types.
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Affiliation(s)
- M Royuela
- Department of Cell Biology and Genetics, University of Alcalá de Henares, Madrid, Spain
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Rovner AS, Freyzon Y, Trybus KM. Chimeric substitutions of the actin-binding loop activate dephosphorylated but not phosphorylated smooth muscle heavy meromyosin. J Biol Chem 1995; 270:30260-3. [PMID: 8530442 DOI: 10.1074/jbc.270.51.30260] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Regulatory light chain (RLC) phosphorylation is necessary to activate smooth muscle myosin, unlike constitutively active striated muscle myosins. Here we show that an actin-binding surface loop located at the 50/20-kDa junction contributes to this fundamental difference between myosins. Substitution of the native actin-binding loop of smooth muscle heavy meromyosin (HMM) with that from either skeletal or beta-cardiac myosin caused the chimeric HMMs to become unregulated like the myosin from which the loop was derived. Dephosphorylated chimeric HMMs gained the ability to move actin in a motility assay and had 50-70% of the actin-activated ATPase activity of phosphorylated wild-type HMM. Direct binding measurements showed that the affinity of HMM for actin in the presence of MgATP was unaffected by loop substitution; thus the rate of a step other than binding is increased. Phosphorylation of the chimeras did not lead to a higher Vmax than obtained for wild-type HMM. In the absence of actin, a foreign loop did not affect nucleotide trapping. Native regulated molecules have thus evolved a loop sequence which prevents rapid product release by actin when the RLC is dephosphorylated, thereby allowing activity to be controlled by RLC phosphorylation.
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Affiliation(s)
- A S Rovner
- Department of Molecular Physiology and Biophysics, University of Vermont, Burlington 05405, USA
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