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Wilson JL, Warburton R, Taylor L, Toksoz D, Hill N, Polgar P. Unraveling endothelin-1 induced hypercontractility of human pulmonary artery smooth muscle cells from patients with pulmonary arterial hypertension. PLoS One 2018; 13:e0195780. [PMID: 29649319 PMCID: PMC5897024 DOI: 10.1371/journal.pone.0195780] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Accepted: 03/29/2018] [Indexed: 01/05/2023] Open
Abstract
Contraction of human pulmonary artery smooth muscle cells (HPASMC) isolated from pulmonary arterial hypertensive (PAH) and normal (non-PAH) subject lungs was determined and measured with real-time electrical impedance. Treatment of HPASMC with vasoactive peptides, endothelin-1 (ET-1) and bradykinin (BK) but not angiotensin II, induced a temporal decrease in the electrical impedance profile mirroring constrictive morphological change of the cells which typically was more robust in PAH as opposed to non-PAH cells. Inhibition with LIMKi3 and a cofilin targeted motif mimicking cell permeable peptide (MMCPP) had no effect on ET-1 induced HPASMC contraction indicating a negligible role for these actin regulatory proteins. On the other hand, a MMCPP blocking the activity of caldesmon reduced ET-1 promoted contraction pointing to a regulatory role of this protein and its activation pathway in HPASMC contraction. Inhibition of this MEK/ERK/p90RSK pathway, which is an upstream regulator of caldesmon phosphorylation, reduced ET-1 induced cell contraction. While the regulation of ET-1 induced cell contraction was found to be similar in PAH and non-PAH cells, a key difference was the response to pharmacological inhibitors and to siRNA knockdown of Rho kinases (ROCK1/ROCK2). The PAH cells required much higher concentrations of inhibitors to abrogate ET-1 induced contractions and their contraction was not affected by siRNA against either ROCK1 or ROCK2. Lastly, blocking of L-type and T-type Ca2+ channels had no effect on ET-1 or BK induced contraction. However, inhibiting the activity of the sarcoplasmic reticulum Ca2+ ATPase blunted ET-1 and BK induced HPASMC contraction in both PAH and non-PAH derived HPASMC. In summary, our findings here together with previous communications illustrate similarities and differences in the regulation PAH and non-PAH smooth muscle cell contraction relating to calcium translocation, RhoA/ROCK signaling and the activity of caldesmon. These findings may provide useful tools in achieving the regulation of the vascular hypercontractility taking place in PAH.
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Affiliation(s)
- Jamie L. Wilson
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Tufts Medical Center, Boston, Massachusetts, United States of America
- * E-mail:
| | - Rod Warburton
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Tufts Medical Center, Boston, Massachusetts, United States of America
| | - Linda Taylor
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Tufts Medical Center, Boston, Massachusetts, United States of America
| | - Deniz Toksoz
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Tufts Medical Center, Boston, Massachusetts, United States of America
| | - Nicholas Hill
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Tufts Medical Center, Boston, Massachusetts, United States of America
| | - Peter Polgar
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Tufts Medical Center, Boston, Massachusetts, United States of America
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2
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Brozovich FV, Nicholson CJ, Degen CV, Gao YZ, Aggarwal M, Morgan KG. Mechanisms of Vascular Smooth Muscle Contraction and the Basis for Pharmacologic Treatment of Smooth Muscle Disorders. Pharmacol Rev 2016; 68:476-532. [PMID: 27037223 PMCID: PMC4819215 DOI: 10.1124/pr.115.010652] [Citation(s) in RCA: 298] [Impact Index Per Article: 37.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The smooth muscle cell directly drives the contraction of the vascular wall and hence regulates the size of the blood vessel lumen. We review here the current understanding of the molecular mechanisms by which agonists, therapeutics, and diseases regulate contractility of the vascular smooth muscle cell and we place this within the context of whole body function. We also discuss the implications for personalized medicine and highlight specific potential target molecules that may provide opportunities for the future development of new therapeutics to regulate vascular function.
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Affiliation(s)
- F V Brozovich
- Department of Health Sciences, Boston University, Boston, Massachusetts (C.J.N., Y.Z.G., M.A., K.G.M.); Department of Medicine, Mayo Clinic, Rochester, Minnesota (F.V.B.); and Paracelsus Medical University Salzburg, Salzburg, Austria (C.V.D.)
| | - C J Nicholson
- Department of Health Sciences, Boston University, Boston, Massachusetts (C.J.N., Y.Z.G., M.A., K.G.M.); Department of Medicine, Mayo Clinic, Rochester, Minnesota (F.V.B.); and Paracelsus Medical University Salzburg, Salzburg, Austria (C.V.D.)
| | - C V Degen
- Department of Health Sciences, Boston University, Boston, Massachusetts (C.J.N., Y.Z.G., M.A., K.G.M.); Department of Medicine, Mayo Clinic, Rochester, Minnesota (F.V.B.); and Paracelsus Medical University Salzburg, Salzburg, Austria (C.V.D.)
| | - Yuan Z Gao
- Department of Health Sciences, Boston University, Boston, Massachusetts (C.J.N., Y.Z.G., M.A., K.G.M.); Department of Medicine, Mayo Clinic, Rochester, Minnesota (F.V.B.); and Paracelsus Medical University Salzburg, Salzburg, Austria (C.V.D.)
| | - M Aggarwal
- Department of Health Sciences, Boston University, Boston, Massachusetts (C.J.N., Y.Z.G., M.A., K.G.M.); Department of Medicine, Mayo Clinic, Rochester, Minnesota (F.V.B.); and Paracelsus Medical University Salzburg, Salzburg, Austria (C.V.D.)
| | - K G Morgan
- Department of Health Sciences, Boston University, Boston, Massachusetts (C.J.N., Y.Z.G., M.A., K.G.M.); Department of Medicine, Mayo Clinic, Rochester, Minnesota (F.V.B.); and Paracelsus Medical University Salzburg, Salzburg, Austria (C.V.D.)
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3
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Theillet FX, Smet-Nocca C, Liokatis S, Thongwichian R, Kosten J, Yoon MK, Kriwacki RW, Landrieu I, Lippens G, Selenko P. Cell signaling, post-translational protein modifications and NMR spectroscopy. JOURNAL OF BIOMOLECULAR NMR 2012; 54:217-36. [PMID: 23011410 PMCID: PMC4939263 DOI: 10.1007/s10858-012-9674-x] [Citation(s) in RCA: 140] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Accepted: 09/07/2012] [Indexed: 05/13/2023]
Abstract
Post-translationally modified proteins make up the majority of the proteome and establish, to a large part, the impressive level of functional diversity in higher, multi-cellular organisms. Most eukaryotic post-translational protein modifications (PTMs) denote reversible, covalent additions of small chemical entities such as phosphate-, acyl-, alkyl- and glycosyl-groups onto selected subsets of modifiable amino acids. In turn, these modifications induce highly specific changes in the chemical environments of individual protein residues, which are readily detected by high-resolution NMR spectroscopy. In the following, we provide a concise compendium of NMR characteristics of the main types of eukaryotic PTMs: serine, threonine, tyrosine and histidine phosphorylation, lysine acetylation, lysine and arginine methylation, and serine, threonine O-glycosylation. We further delineate the previously uncharacterized NMR properties of lysine propionylation, butyrylation, succinylation, malonylation and crotonylation, which, altogether, define an initial reference frame for comprehensive PTM studies by high-resolution NMR spectroscopy.
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Affiliation(s)
- Francois-Xavier Theillet
- Department of NMR-Supported Structural Biology, Leibniz Institute of Molecular Pharmacology (FMP Berlin), In-cell NMR Group, Robert-Roessle Strasse 10, 13125 Berlin, German
| | - Caroline Smet-Nocca
- CNRS UMR 8576, Universite Lille Nord de France, 59655 Villeneuve d’Ascq, France
| | - Stamatios Liokatis
- Department of NMR-Supported Structural Biology, Leibniz Institute of Molecular Pharmacology (FMP Berlin), In-cell NMR Group, Robert-Roessle Strasse 10, 13125 Berlin, German
| | - Rossukon Thongwichian
- Department of NMR-Supported Structural Biology, Leibniz Institute of Molecular Pharmacology (FMP Berlin), In-cell NMR Group, Robert-Roessle Strasse 10, 13125 Berlin, German
| | - Jonas Kosten
- Department of NMR-Supported Structural Biology, Leibniz Institute of Molecular Pharmacology (FMP Berlin), In-cell NMR Group, Robert-Roessle Strasse 10, 13125 Berlin, German
| | - Mi-Kyung Yoon
- Department of Structural Biology, St. Jude Children’s Research Hospital, Memphis, TN, USA
| | - Richard W. Kriwacki
- Department of Structural Biology, St. Jude Children’s Research Hospital, Memphis, TN, USA
| | - Isabelle Landrieu
- CNRS UMR 8576, Universite Lille Nord de France, 59655 Villeneuve d’Ascq, France
| | - Guy Lippens
- CNRS UMR 8576, Universite Lille Nord de France, 59655 Villeneuve d’Ascq, France
| | - Philipp Selenko
- Department of NMR-Supported Structural Biology, Leibniz Institute of Molecular Pharmacology (FMP Berlin), In-cell NMR Group, Robert-Roessle Strasse 10, 13125 Berlin, German
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4
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Roberts RE. The extracellular signal-regulated kinase (ERK) pathway: a potential therapeutic target in hypertension. J Exp Pharmacol 2012; 4:77-83. [PMID: 27186119 PMCID: PMC4863547 DOI: 10.2147/jep.s28907] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Hypertension is a risk factor for myocardial infarction, stroke, renal failure, heart failure, and peripheral vascular disease. One feature of hypertension is a hyperresponsiveness to contractile agents, and inhibition of vasoconstriction forms the basis of some of the treatments for hypertension. Hypertension is also associated with an increase in the growth and proliferation of vascular smooth muscle cells, which can lead to a thickening of the smooth muscle layer of the blood vessels and a reduction in lumen diameter. Targeting both the enhanced contractile responses, and the increased vascular smooth muscle cell growth could potentially be important pharmacological treatment of hypertension. Extracellular signal-regulated kinase (ERK) is a member of the mitogen-activated protein kinase family that is involved in both vasoconstriction and vascular smooth muscle cell growth and this, therefore, makes it attractive therapeutic target for treatment of hypertension. ERK activity is raised in vascular smooth muscle cells from animal models of hypertension, and inhibition of ERK activation reduces both vascular smooth muscle cell growth and vasoconstriction. This review discusses the potential for targeting ERK activity in the treatment of hypertension.
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Affiliation(s)
- Richard E Roberts
- School of Biomedical Sciences, University of Nottingham, Nottingham, United Kingdom
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Mayanagi T, Sobue K. Diversification of caldesmon-linked actin cytoskeleton in cell motility. Cell Adh Migr 2011; 5:150-9. [PMID: 21350330 DOI: 10.4161/cam.5.2.14398] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The actin cytoskeleton plays a key role in regulating cell motility. Caldesmon (CaD) is an actin-linked regulatory protein found in smooth muscle and non-muscle cells that is conserved among a variety of vertebrates. It binds and stabilizes actin filaments, as well as regulating actin-myosin interaction in a calcium (Ca2+)/calmodulin (CaM)- and/or phosphorylation-dependent manner. CaD function is regulated qualitatively by Ca2+/CaM and by its phosphorylation state and quantitatively at the mRNA level, by three different transcriptional regulation of the CALD1 gene. CaD has numerous functions in cell motility, such as migration, invasion, and proliferation, exerted via the reorganization of the actin cytoskeleton. Here we will outline recent findings regarding CaD's structural features and functions.
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Affiliation(s)
- Taira Mayanagi
- Department of Neuroscience, Osaka University Graduate School of Medicine, Osaka, Japan
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6
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Kudryashova TV, Rutkevich PN, Shevelev AY, Vlasik TN, Vorotnikov AV. Caldesmon affects actin organization at the leading edge and inhibits cell migration. Biophysics (Nagoya-shi) 2008. [DOI: 10.1134/s0006350908060110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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7
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Noda Y, Horikawa S, Kanda E, Yamashita M, Meng H, Eto K, Li Y, Kuwahara M, Hirai K, Pack C, Kinjo M, Okabe S, Sasaki S. Reciprocal interaction with G-actin and tropomyosin is essential for aquaporin-2 trafficking. ACTA ACUST UNITED AC 2008; 182:587-601. [PMID: 18678705 PMCID: PMC2500142 DOI: 10.1083/jcb.200709177] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Trafficking of water channel aquaporin-2 (AQP2) to the apical membrane and its vasopressin and protein kinase A (PKA)–dependent regulation in renal collecting ducts is critical for body water homeostasis. We previously identified an AQP2 binding protein complex including actin and tropomyosin-5b (TM5b). We show that dynamic interactions between AQP2 and the actin cytoskeleton are critical for initiating AQP2 apical targeting. Specific binding of AQP2 to G-actin in reconstituted liposomes is negatively regulated by PKA phosphorylation. Dual color fluorescence cross-correlation spectroscopy reveals local AQP2 interaction with G-actin in live epithelial cells at single-molecule resolution. Cyclic adenosine monophosphate signaling and AQP2 phosphorylation release AQP2 from G-actin. In turn, AQP2 phosphorylation increases its affinity to TM5b, resulting in reduction of TM5b bound to F-actin, subsequently inducing F-actin destabilization. RNA interference–mediated knockdown and overexpression of TM5b confirm its inhibitory role in apical trafficking of AQP2. These findings indicate a novel mechanism of channel protein trafficking, in which the channel protein itself critically regulates local actin reorganization to initiate its movement.
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Affiliation(s)
- Yumi Noda
- Department of Nephrology, Graduate School of Medicine, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113-8519, Japan.
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8
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Hu J, Zhao YF, Li YM. The Effects of Reversible Phosphorylation on Peptide and Protein Local Structure. PHOSPHORUS SULFUR 2008. [DOI: 10.1080/10426500701734141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
- Jia Hu
- a Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology (Ministry of Education), Department of Chemistry , Tsinghua University , Beijing, P. R. China
| | - Yu-Fen Zhao
- a Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology (Ministry of Education), Department of Chemistry , Tsinghua University , Beijing, P. R. China
| | - Yan-Mei Li
- a Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology (Ministry of Education), Department of Chemistry , Tsinghua University , Beijing, P. R. China
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9
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Role of tropomyosin in the regulation of contraction in smooth muscle. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 644:110-23. [PMID: 19209817 DOI: 10.1007/978-0-387-85766-4_9] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Smooth muscle contraction is due to the interaction ofmyosin filaments with thin filaments. Thin filaments are composed of actin, tropomyosin, caldesmon and calmodulin in ratios 14:2:1:1. Tissue specific isoforms of act and beta tropomyosin are expressed in smooth muscle. Compared with skeletal muscle tropomyosin, the cooperative activation of actomyosin is enhanced by smooth muscle tropomyosin: cooperative unit size is 10 and the equilibrium between on and off states is shifted towards the on state. The smooth muscle-specific actin-bindingprotein caldesmon, together with calmodulin regulates the activity of the thin filament in response to Ca2+. Caldesmon and calmodulin control the tropomyosin-mediated transition between on and offactivity states.
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10
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Du JT, Li YM, Wei W, Wu GS, Zhao YF, Kanazawa K, Nemoto T, Nakanishi H. Low-barrier hydrogen bond between phosphate and the amide group in phosphopeptide. J Am Chem Soc 2006; 127:16350-1. [PMID: 16305194 DOI: 10.1021/ja054568p] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
As the conversion between the monoionic (1) and diionic (2) form of the phosphate occurs, the phosphorylated peptides or proteins can not only cause the formation of a hydrogen bond between the phosphate group and the amide group but also change the strength of the hydrogen bond to form low-barrier hydrogen bonds (LBHBs). This reversible protonation of the phosphate group, which changes both the electrostatic properties of the phosphate group and the strength of the hydrogen bond, provides a possible mechanism in regulating protein function.
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Affiliation(s)
- Jin-Tang Du
- Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing 100084, PR China
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11
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Huang R, Wang CLA. A caldesmon peptide activates smooth muscle via a mechanism similar to ERK-mediated phosphorylation. FEBS Lett 2005; 580:63-6. [PMID: 16343491 DOI: 10.1016/j.febslet.2005.11.047] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2005] [Revised: 11/16/2005] [Accepted: 11/18/2005] [Indexed: 10/25/2022]
Abstract
Caldesmon (CaD) is thought to regulate smooth muscle contraction, because it binds actin and inhibits actomyosin interactions. A synthetic actin-binding peptide (GS17C) corresponding to Gly666-Ser682 of chicken gizzard CaD has been shown to induce force development in permeabilized smooth muscle cells. The mechanism of GS17C's action remains unclear, although a structural effect was postulated. By photo-crosslinking and fluorescence quenching experiments with a gizzard CaD fragment (H32K; Met563-Pro771) and its mutants, we showed that GS17C indeed dissociated the C-terminal region of H32K from actin, in a manner similar to extracellular signal-regulated kinase-mediated phosphorylation, thereby reversing the CaD-imposed inhibition and enabling the actomyosin interaction.
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Affiliation(s)
- Renjian Huang
- Boston Biomedical Research Institute, Muscle and Motility Group, 64 Grove St., Watertown, MA 02472, USA
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12
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Cuomo ME, Knebel A, Platt G, Morrice N, Cohen P, Mittnacht S. Regulation of microfilament organization by Kaposi sarcoma-associated herpes virus-cyclin.CDK6 phosphorylation of caldesmon. J Biol Chem 2005; 280:35844-58. [PMID: 16115893 DOI: 10.1074/jbc.m503877200] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Kaposi sarcoma-associated herpes virus (KSHV) encodes a D-like cyclin (K-cyclin) that is thought to contribute to the viral oncogenicity. K-cyclin activates cellular cyclin-dependent kinases (CDK) 4 and 6, generating enzymes with a substrate selectivity deviant from CDK4 and CDK6 activated by D-type cyclins, suggesting different biochemical and biological functions. Here we report the identification of the actin- and calmodulin-binding protein caldesmon (CALD1) as a novel K-cyclin.CDK substrate, which is not phosphorylated by D.CDK. CALD1 plays a central role in the regulation of microfilament organization, consequently controlling cell shape, adhesion, cytokinesis and motility. K-cyclin.CDK6 specifically phosphorylates four Ser/Thr sites in the human CALD1 carboxyl terminus, abolishing CALD1 binding to its effector protein, actin, and its regulator protein, calmodulin. CALD1 is hyperphosphorylated in cells following K-cyclin expression and in KSHV-transformed lymphoma cells. Moreover, expression of exogenous K-cyclin results in microfilament loss and changes in cell morphology; both effects are reliant on CDK catalysis and can be reversed by the expression of a phosphorylation defective CALD1. Together, these data strongly suggest that K-cyclin expression modulates the activity of caldesmon and through this the microfilament functions in cells. These results establish a novel link between KSHV infection and the regulation of the actin cytoskeleton.
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MESH Headings
- Actins/chemistry
- Animals
- Calmodulin-Binding Proteins/chemistry
- Calmodulin-Binding Proteins/metabolism
- Catalysis
- Chromatography, Affinity
- Cloning, Molecular
- Cyclin-Dependent Kinase 4/metabolism
- Cyclin-Dependent Kinase 6/metabolism
- Cytoskeleton/metabolism
- Electrophoresis, Polyacrylamide Gel
- Gene Expression Regulation, Viral
- HeLa Cells
- Herpesvirus 8, Human/metabolism
- Humans
- Mass Spectrometry
- Mice
- Microscopy, Fluorescence
- NIH 3T3 Cells
- Peptides/chemistry
- Phosphorylation
- Protein Binding
- Protein Structure, Tertiary
- RNA, Small Interfering/metabolism
- Recombinant Proteins/chemistry
- Retinoblastoma Protein/metabolism
- Sepharose/chemistry
- Serine/chemistry
- Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
- Substrate Specificity
- Threonine/chemistry
- Time Factors
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Affiliation(s)
- Maria Emanuela Cuomo
- Cancer Research UK Centre for Cell and Molecular Biology, Chester Beatty Laboratories, The Institute of Cancer Research, 237 Fulham Road, SW3 6JB London, United Kingdom
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13
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Foster DB, Huang R, Hatch V, Craig R, Graceffa P, Lehman W, Wang CLA. Modes of Caldesmon Binding to Actin. J Biol Chem 2004; 279:53387-94. [PMID: 15456752 DOI: 10.1074/jbc.m410109200] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Smooth muscle caldesmon binds actin and inhibits actomyosin ATPase activity. Phosphorylation of caldesmon by extracellular signal-regulated kinase (ERK) reverses this inhibitory effect and weakens actin binding. To better understand this function, we have examined the phosphorylation-dependent contact sites of caldesmon on actin by low dose electron microscopy and three-dimensional reconstruction of actin filaments decorated with a C-terminal fragment, hH32K, of human caldesmon containing the principal actin-binding domains. Helical reconstruction of negatively stained filaments demonstrated that hH32K is located on the inner portion of actin subdomain 1, traversing its upper surface toward the C-terminal segment of actin, and forms a bridge to the neighboring actin monomer of the adjacent long pitch helical strand by connecting to its subdomain 3. Such lateral binding was supported by cross-linking experiments using a mutant isoform, which was capable of cross-linking actin subunits. Upon ERK phosphorylation, however, the mutant no longer cross-linked actin to polymers. Three-dimensional reconstruction of ERK-phosphorylated hH32K indeed indicated loss of the interstrand connectivity. These results, together with fluorescence quenching data, are consistent with a phosphorylation-dependent conformational change that moves the C-terminal end segment of caldesmon near the phosphorylation site but not the upstream region around Cys(595), away from F-actin, thus neutralizing its inhibitory effect on actomyosin interactions. The binding pattern of hH32K suggests a mechanism by which unphosphorylated, but not ERK-phosphorylated, caldesmon could stabilize actin filaments and resist F-actin severing or depolymerization in both smooth muscle and nonmuscle cells.
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Affiliation(s)
- D Brian Foster
- Boston Biomedical Research Institute, 64 Grove St., Watertown, MA 02472, USA
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14
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Li Y, Je HD, Malek S, Morgan KG. Role of ERK1/2 in uterine contractility and preterm labor in rats. Am J Physiol Regul Integr Comp Physiol 2004; 287:R328-35. [PMID: 15072963 DOI: 10.1152/ajpregu.00042.2004] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The present study tested the hypothesis that ERK activation is an essential step in the onset of labor in a rat model of preterm labor. The administration of RU-486, an antiprogesterone agent, to rats induced preterm delivery 22.2 +/- 0.24 h after treatment. Changes in basal signaling events were studied in myometrial tissue from CO(2)-euthanized rats. Rats treated with RU-486 displayed a dramatically increased in vitro uterine contractility compared with gestational stage-matched, sham-treated rats. In vitro contractility was not significantly different from that during spontaneous labor. During RU-486-induced preterm labor, as previously described for spontaneous labor, ERK phosphorylation levels increased, as did phosphorylation of caldesmon at Ser(789), an ERK phosphorylation site. Also, a small but significant increase in 20-kDa myosin light chain phosphorylation was seen at a constant intracellular pCa of 7. When rats were chronically treated with an agent that prevents ERK activation, U-0126, the onset of RU-486-induced preterm labor was delayed in a statistically significant manner. Chronic in vivo treatment with U-0126 also significantly inhibited the RU-486-induced increase in in vitro contractility and ERK and caldesmon phosphorylation but did not alter the RU-486-induced increase in 20-kDa myosin light chain phosphorylation. These data indicate that ERK activation is a component of the multiple events leading to the development of labor in this rat model. We suggest that the ERK pathway could possibly be used to identify targets for the development of a novel class of tocolytic agents.
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Affiliation(s)
- Yunping Li
- Department of Anesthesia and Critical Care, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston 02215, USA.
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15
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Huang R, Li L, Guo H, Wang CLA. Caldesmon binding to actin is regulated by calmodulin and phosphorylation via different mechanisms. Biochemistry 2003; 42:2513-23. [PMID: 12614145 DOI: 10.1021/bi0268605] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Smooth muscle caldesmon (CaD) binds F-actin and inhibits actomyosin ATPase activity. The inhibition is reversed by Ca2+/calmodulin (CaM). CaD is also phosphorylated upon stimulation at sites specific for mitogen-activated protein kinases (MAPKs). Because of these properties, CaD is thought to be involved in the regulation of smooth muscle contraction. The molecular mechanism of the reversal of inhibition is not well understood. We have expressed His6-tagged fragments containing the sequence of the C-terminal region of human (from M563 to V793) and chicken (from M563 to P771) CaD as well as a variant of the chicken isoform with a Q766C point mutation. By cleavages with proteases, followed by high-speed cosedimentation with F-actin and mass spectrometry, we found that within the C-terminal region of CaD there are multiple actin contact points forming two clusters. Intramolecular fluorescence resonance energy transfer between probes attached to cysteine residues (the endogenous C595 and the engineered C766) located in these two clusters revealed that the C-terminal region of CaD is elongated, but it becomes more compact when bound to actin. Binding of CaM restores the elongated conformation and facilitates dissociation of the C-terminal CaD fragment from F-actin. When the CaD fragment was phosphorylated with a MAPK, only one of the two actin-binding clusters dissociated from F-actin, whereas the other remained bound. Taken together, these results demonstrate that while both Ca2+/CaM and MAPK phosphorylation govern CaD's function via a conformational change, the regulatory mechanisms are different.
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Affiliation(s)
- Renjian Huang
- Muscle and Motility Group, Boston Biomedical Research Institute, 64 Grove Street, Watertown, Massachusetts 02472, USA
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