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Vahle B, Heilmann L, Schauer A, Augstein A, Jarabo MEP, Barthel P, Mangner N, Labeit S, Bowen TS, Linke A, Adams V. Modulation of Titin and Contraction-Regulating Proteins in a Rat Model of Heart Failure with Preserved Ejection Fraction: Limb vs. Diaphragmatic Muscle. Int J Mol Sci 2024; 25:6618. [PMID: 38928324 PMCID: PMC11203682 DOI: 10.3390/ijms25126618] [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: 05/24/2024] [Revised: 06/12/2024] [Accepted: 06/14/2024] [Indexed: 06/28/2024] Open
Abstract
Heart failure with preserved ejection fraction (HFpEF) is characterized by biomechanically dysfunctional cardiomyocytes. Underlying cellular changes include perturbed myocardial titin expression and titin hypophosphorylation leading to titin filament stiffening. Beside these well-studied alterations at the cardiomyocyte level, exercise intolerance is another hallmark of HFpEF caused by molecular alterations in skeletal muscle (SKM). Currently, there is a lack of data regarding titin modulation in the SKM of HFpEF. Therefore, the aim of the present study was to analyze molecular alterations in limb SKM (tibialis anterior (TA)) and in the diaphragm (Dia), as a more central SKM, with a focus on titin, titin phosphorylation, and contraction-regulating proteins. This study was performed with muscle tissue, obtained from 32-week old female ZSF-1 rats, an established a HFpEF rat model. Our results showed a hyperphosphorylation of titin in limb SKM, based on enhanced phosphorylation at the PEVK region, which is known to lead to titin filament stiffening. This hyperphosphorylation could be reversed by high-intensity interval training (HIIT). Additionally, a negative correlation occurring between the phosphorylation state of titin and the muscle force in the limb SKM was evident. For the Dia, no alterations in the phosphorylation state of titin could be detected. Supported by data of previous studies, this suggests an exercise effect of the Dia in HFpEF. Regarding the expression of contraction regulating proteins, significant differences between Dia and limb SKM could be detected, supporting muscle atrophy and dysfunction in limb SKM, but not in the Dia. Altogether, these data suggest a correlation between titin stiffening and the appearance of exercise intolerance in HFpEF, as well as a differential regulation between different SKM groups.
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Affiliation(s)
- Beatrice Vahle
- Heart Center Dresden, Laboratory of Molecular and Experimental Cardiology, TU Dresden, 01307 Dresden, Germany; (B.V.); (L.H.); (A.S.); (A.A.); (M.-E.P.J.); (P.B.); (N.M.); (A.L.)
| | - Leonard Heilmann
- Heart Center Dresden, Laboratory of Molecular and Experimental Cardiology, TU Dresden, 01307 Dresden, Germany; (B.V.); (L.H.); (A.S.); (A.A.); (M.-E.P.J.); (P.B.); (N.M.); (A.L.)
| | - Antje Schauer
- Heart Center Dresden, Laboratory of Molecular and Experimental Cardiology, TU Dresden, 01307 Dresden, Germany; (B.V.); (L.H.); (A.S.); (A.A.); (M.-E.P.J.); (P.B.); (N.M.); (A.L.)
| | - Antje Augstein
- Heart Center Dresden, Laboratory of Molecular and Experimental Cardiology, TU Dresden, 01307 Dresden, Germany; (B.V.); (L.H.); (A.S.); (A.A.); (M.-E.P.J.); (P.B.); (N.M.); (A.L.)
| | - Maria-Elisa Prieto Jarabo
- Heart Center Dresden, Laboratory of Molecular and Experimental Cardiology, TU Dresden, 01307 Dresden, Germany; (B.V.); (L.H.); (A.S.); (A.A.); (M.-E.P.J.); (P.B.); (N.M.); (A.L.)
| | - Peggy Barthel
- Heart Center Dresden, Laboratory of Molecular and Experimental Cardiology, TU Dresden, 01307 Dresden, Germany; (B.V.); (L.H.); (A.S.); (A.A.); (M.-E.P.J.); (P.B.); (N.M.); (A.L.)
| | - Norman Mangner
- Heart Center Dresden, Laboratory of Molecular and Experimental Cardiology, TU Dresden, 01307 Dresden, Germany; (B.V.); (L.H.); (A.S.); (A.A.); (M.-E.P.J.); (P.B.); (N.M.); (A.L.)
| | - Siegfried Labeit
- DZHK Partner Site Mannheim-Heidelberg, Medical Faculty Mannheim, University of Heidelberg, 68169 Mannheim, Germany;
- Myomedix GmbH, 69151 Neckargemünd, Germany
| | - T. Scott Bowen
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK;
| | - Axel Linke
- Heart Center Dresden, Laboratory of Molecular and Experimental Cardiology, TU Dresden, 01307 Dresden, Germany; (B.V.); (L.H.); (A.S.); (A.A.); (M.-E.P.J.); (P.B.); (N.M.); (A.L.)
| | - Volker Adams
- Heart Center Dresden, Laboratory of Molecular and Experimental Cardiology, TU Dresden, 01307 Dresden, Germany; (B.V.); (L.H.); (A.S.); (A.A.); (M.-E.P.J.); (P.B.); (N.M.); (A.L.)
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Stroik D, Gregorich ZR, Raza F, Ge Y, Guo W. Titin: roles in cardiac function and diseases. Front Physiol 2024; 15:1385821. [PMID: 38660537 PMCID: PMC11040099 DOI: 10.3389/fphys.2024.1385821] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Accepted: 03/25/2024] [Indexed: 04/26/2024] Open
Abstract
The giant protein titin is an essential component of muscle sarcomeres. A single titin molecule spans half a sarcomere and mediates diverse functions along its length by virtue of its unique domains. The A-band of titin functions as a molecular blueprint that defines the length of the thick filaments, the I-band constitutes a molecular spring that determines cell-based passive stiffness, and various domains, including the Z-disk, I-band, and M-line, serve as scaffolds for stretch-sensing signaling pathways that mediate mechanotransduction. This review aims to discuss recent insights into titin's functional roles and their relationship to cardiac function. The role of titin in heart diseases, such as dilated cardiomyopathy and heart failure with preserved ejection fraction, as well as its potential as a therapeutic target, is also discussed.
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Affiliation(s)
- Dawson Stroik
- Cellular and Molecular Pathology Program, Department of Pathology and Laboratory Medicine, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, United States
- Department of Animal and Dairy Sciences, College of Agriculture and Life Science, University of Wisconsin-Madison, Madison, WI, United States
| | - Zachery R. Gregorich
- Department of Animal and Dairy Sciences, College of Agriculture and Life Science, University of Wisconsin-Madison, Madison, WI, United States
| | - Farhan Raza
- Department of Medicine, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, United States
| | - Ying Ge
- Department of Cell and Regenerative Biology, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, United States
| | - Wei Guo
- Cellular and Molecular Pathology Program, Department of Pathology and Laboratory Medicine, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI, United States
- Department of Animal and Dairy Sciences, College of Agriculture and Life Science, University of Wisconsin-Madison, Madison, WI, United States
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3
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Eccentric muscle contractions: from single muscle fibre to whole muscle mechanics. Pflugers Arch 2023; 475:421-435. [PMID: 36790515 PMCID: PMC10011336 DOI: 10.1007/s00424-023-02794-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 01/24/2023] [Accepted: 02/01/2023] [Indexed: 02/16/2023]
Abstract
Eccentric muscle loading encompasses several unique features compared to other types of contractions. These features include increased force, work, and performance at decreased oxygen consumption, reduced metabolic cost, improved energy efficiency, as well as decreased muscle activity. This review summarises explanatory approaches to long-standing questions in terms of muscular contraction dynamics and molecular and cellular mechanisms underlying eccentric muscle loading. Moreover, this article intends to underscore the functional link between sarcomeric components, emphasising the fundamental role of titin in skeletal muscle. The giant filament titin reveals versatile functions ranging from sarcomere organisation and maintenance, providing passive tension and elasticity, and operates as a mechanosensory and signalling platform. Structurally, titin consists of a viscoelastic spring segment that allows activation-dependent coupling to actin. This titin-actin interaction can explain linear force increases in active lengthening experiments in biological systems. A three-filament model of skeletal muscle force production (mediated by titin) is supposed to overcome significant deviations between experimental observations and predictions by the classic sliding-filament and cross-bridge theories. Taken together, this review intends to contribute to a more detailed understanding of overall muscle behaviour and force generation-from a microscopic sarcomere level to a macroscopic multi-joint muscle level-impacting muscle modelling, the understanding of muscle function, and disease.
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Interdomain Linker Effect on the Mechanical Stability of Ig Domains in Titin. Int J Mol Sci 2022; 23:ijms23179836. [PMID: 36077234 PMCID: PMC9456048 DOI: 10.3390/ijms23179836] [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] [Received: 07/30/2022] [Revised: 08/24/2022] [Accepted: 08/26/2022] [Indexed: 11/17/2022] Open
Abstract
Titin is the largest protein in humans, composed of more than one hundred immunoglobulin (Ig) domains, and plays a critical role in muscle’s passive elasticity. Thus, the molecular design of this giant polyprotein is responsible for its mechanical function. Interestingly, most of these Ig domains are connected directly with very few interdomain residues/linker, which suggests such a design is necessary for its mechanical stability. To understand this design, we chose six representative Ig domains in titin and added nine glycine residues (9G) as an artificial interdomain linker between these Ig domains. We measured their mechanical stabilities using atomic force microscopy-based single-molecule force spectroscopy (AFM-SMFS) and compared them to the natural sequence. The AFM results showed that the linker affected the mechanical stability of Ig domains. The linker mostly reduces its mechanical stability to a moderate extent, but the opposite situation can happen. Thus, this effect is very complex and may depend on each particular domain’s property.
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Atomic Force Microscopy (AFM) Applications in Arrhythmogenic Cardiomyopathy. Int J Mol Sci 2022; 23:ijms23073700. [PMID: 35409059 PMCID: PMC8998711 DOI: 10.3390/ijms23073700] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Revised: 03/22/2022] [Accepted: 03/23/2022] [Indexed: 02/06/2023] Open
Abstract
Arrhythmogenic cardiomyopathy (ACM) is an inherited heart muscle disorder characterized by progressive replacement of cardiomyocytes by fibrofatty tissue, ventricular dilatation, cardiac dysfunction, arrhythmias, and sudden cardiac death. Interest in molecular biomechanics for these disorders is constantly growing. Atomic force microscopy (AFM) is a well-established technic to study the mechanobiology of biological samples under physiological and pathological conditions at the cellular scale. However, a review which described all the different data that can be obtained using the AFM (cell elasticity, adhesion behavior, viscoelasticity, beating force, and frequency) is still missing. In this review, we will discuss several techniques that highlight the potential of AFM to be used as a tool for assessing the biomechanics involved in ACM. Indeed, analysis of genetically mutated cells with AFM reveal abnormalities of the cytoskeleton, cell membrane structures, and defects of contractility. The higher the Young’s modulus, the stiffer the cell, and it is well known that abnormal tissue stiffness is symptomatic of a range of diseases. The cell beating force and frequency provide information during the depolarization and repolarization phases, complementary to cell electrophysiology (calcium imaging, MEA, patch clamp). In addition, original data is also presented to emphasize the unique potential of AFM as a tool to assess fibrosis in cardiac tissue.
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Bang ML, Bogomolovas J, Chen J. Understanding the molecular basis of cardiomyopathy. Am J Physiol Heart Circ Physiol 2022; 322:H181-H233. [PMID: 34797172 PMCID: PMC8759964 DOI: 10.1152/ajpheart.00562.2021] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 11/16/2021] [Accepted: 11/16/2021] [Indexed: 02/03/2023]
Abstract
Inherited cardiomyopathies are a major cause of mortality and morbidity worldwide and can be caused by mutations in a wide range of proteins located in different cellular compartments. The present review is based on Dr. Ju Chen's 2021 Robert M. Berne Distinguished Lectureship of the American Physiological Society Cardiovascular Section, in which he provided an overview of the current knowledge on the cardiomyopathy-associated proteins that have been studied in his laboratory. The review provides a general summary of the proteins in different compartments of cardiomyocytes associated with cardiomyopathies, with specific focus on the proteins that have been studied in Dr. Chen's laboratory.
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Affiliation(s)
- Marie-Louise Bang
- Institute of Genetic and Biomedical Research (IRGB), National Research Council (CNR), Milan Unit, Milan, Italy
- IRCCS Humanitas Research Hospital, Rozzano (Milan), Italy
| | - Julius Bogomolovas
- Division of Cardiovascular Medicine, Department of Medicine Cardiology, University of California, San Diego, La Jolla, California
| | - Ju Chen
- Division of Cardiovascular Medicine, Department of Medicine Cardiology, University of California, San Diego, La Jolla, California
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van der Pijl RJ, Domenighetti AA, Sheikh F, Ehler E, Ottenheijm CAC, Lange S. The titin N2B and N2A regions: biomechanical and metabolic signaling hubs in cross-striated muscles. Biophys Rev 2021; 13:653-677. [PMID: 34745373 PMCID: PMC8553726 DOI: 10.1007/s12551-021-00836-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 08/23/2021] [Indexed: 02/07/2023] Open
Abstract
Muscle specific signaling has been shown to originate from myofilaments and their associated cellular structures, including the sarcomeres, costameres or the cardiac intercalated disc. Two signaling hubs that play important biomechanical roles for cardiac and/or skeletal muscle physiology are the N2B and N2A regions in the giant protein titin. Prominent proteins associated with these regions in titin are chaperones Hsp90 and αB-crystallin, members of the four-and-a-half LIM (FHL) and muscle ankyrin repeat protein (Ankrd) families, as well as thin filament-associated proteins, such as myopalladin. This review highlights biological roles and properties of the titin N2B and N2A regions in health and disease. Special emphasis is placed on functions of Ankrd and FHL proteins as mechanosensors that modulate muscle-specific signaling and muscle growth. This region of the sarcomere also emerged as a hotspot for the modulation of passive muscle mechanics through altered titin phosphorylation and splicing, as well as tethering mechanisms that link titin to the thin filament system.
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Affiliation(s)
| | - Andrea A. Domenighetti
- Shirley Ryan AbilityLab, Chicago, IL USA
- Department of Physical Medicine and Rehabilitation, Northwestern University, Chicago, IL USA
| | - Farah Sheikh
- Division of Cardiology, School of Medicine, UC San Diego, La Jolla, CA USA
| | - Elisabeth Ehler
- Randall Centre for Cell and Molecular Biophysics, School of Cardiovascular Medicine and Sciences, King’s College London, London, UK
| | - Coen A. C. Ottenheijm
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ USA
- Department of Physiology, Amsterdam University Medical Centers, Amsterdam, The Netherlands
| | - Stephan Lange
- Division of Cardiology, School of Medicine, UC San Diego, La Jolla, CA USA
- Department of Molecular and Clinical Medicine, University of Gothenburg, Gothenburg, Sweden
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Kelly C, Gage MJ. Protein Unfolding: Denaturant vs. Force. Biomedicines 2021; 9:biomedicines9101395. [PMID: 34680512 PMCID: PMC8533514 DOI: 10.3390/biomedicines9101395] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Revised: 09/20/2021] [Accepted: 09/28/2021] [Indexed: 11/16/2022] Open
Abstract
While protein refolding has been studied for over 50 years since the pioneering work of Christian Anfinsen, there have been a limited number of studies correlating results between chemical, thermal, and mechanical unfolding. The limited knowledge of the relationship between these processes makes it challenging to compare results between studies if different refolding methods were applied. Our current work compares the energetic barriers and folding rates derived from chemical, thermal, and mechanical experiments using an immunoglobulin-like domain from the muscle protein titin as a model system. This domain, I83, has high solubility and low stability relative to other Ig domains in titin, though its stability can be modulated by calcium. Our experiments demonstrated that the free energy of refolding was equivalent with all three techniques, but the refolding rates exhibited differences, with mechanical refolding having slightly faster rates. This suggests that results from equilibrium-based measurements can be compared directly but care should be given comparing refolding kinetics derived from refolding experiments that used different unfolding methods.
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Affiliation(s)
- Colleen Kelly
- Department of Chemistry, University of Massachusetts Lowell, Lowell, MA 01854, USA;
| | - Matthew J. Gage
- Department of Chemistry, University of Massachusetts Lowell, Lowell, MA 01854, USA;
- UMass Movement Center (UMOVE), University of Massachusetts Lowell, Lowell, MA 01854, USA
- Correspondence:
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Bogomolovas J, Fleming JR, Franke B, Manso B, Simon B, Gasch A, Markovic M, Brunner T, Knöll R, Chen J, Labeit S, Scheffner M, Peter C, Mayans O. Titin kinase ubiquitination aligns autophagy receptors with mechanical signals in the sarcomere. EMBO Rep 2021; 22:e48018. [PMID: 34402565 PMCID: PMC8490993 DOI: 10.15252/embr.201948018] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 07/07/2021] [Accepted: 07/19/2021] [Indexed: 12/13/2022] Open
Abstract
Striated muscle undergoes remodelling in response to mechanical and physiological stress, but little is known about the integration of such varied signals in the myofibril. The interaction of the elastic kinase region from sarcomeric titin (A168-M1) with the autophagy receptors Nbr1/p62 and MuRF E3 ubiquitin ligases is well suited to link mechanosensing with the trophic response of the myofibril. To investigate the mechanisms of signal cross-talk at this titin node, we elucidated its 3D structure, analysed its response to stretch using steered molecular dynamics simulations and explored its functional relation to MuRF1 and Nbr1/p62 using cellular assays. We found that MuRF1-mediated ubiquitination of titin kinase promotes its scaffolding of Nbr1/p62 and that the process can be dynamically down-regulated by the mechanical unfolding of a linker sequence joining titin kinase with the MuRF1 receptor site in titin. We propose that titin ubiquitination is sensitive to the mechanical state of the sarcomere, the regulation of sarcomere targeting by Nbr1/p62 being a functional outcome. We conclude that MuRF1/Titin Kinase/Nbr1/p62 constitutes a distinct assembly that predictably promotes sarcomere breakdown in inactive muscle.
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Affiliation(s)
- Julius Bogomolovas
- Department of MedicineSchool of MedicineUniversity of CaliforniaSan Diego, La JollaCAUSA
- Department of Cognitive and Clinical NeuroscienceCentral Institute of Mental HealthMedical Faculty MannheimHeidelberg UniversityMannheimGermany
- Department of Integrative PathophysiologyMedical Faculty MannheimUniversity of HeidelbergMannheimGermany
| | | | - Barbara Franke
- Department of BiologyUniversity of KonstanzKonstanzGermany
| | - Bruno Manso
- Department of BiologyUniversity of KonstanzKonstanzGermany
| | - Bernd Simon
- Structural and Computational Biology UnitEMBLHeidelbergGermany
| | - Alexander Gasch
- Department of Integrative PathophysiologyMedical Faculty MannheimUniversity of HeidelbergMannheimGermany
| | | | - Thomas Brunner
- Department of BiologyUniversity of KonstanzKonstanzGermany
| | - Ralph Knöll
- Integrated Cardio Metabolic Centre (ICMC)Heart and Vascular ThemeUniversity Hospital, MedHKarolinska InstitutetHuddingeSweden
- Bioscience, CardiovascularRenal & MetabolismBioPharmaceuticalsR&D, AstraZenecaGothenburgSweden
| | - Ju Chen
- Department of MedicineSchool of MedicineUniversity of CaliforniaSan Diego, La JollaCAUSA
| | - Siegfried Labeit
- Department of Integrative PathophysiologyMedical Faculty MannheimUniversity of HeidelbergMannheimGermany
| | | | - Christine Peter
- Department of ChemistryUniversity of KonstanzKonstanzGermany
| | - Olga Mayans
- Department of BiologyUniversity of KonstanzKonstanzGermany
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Alegre-Cebollada J. Protein nanomechanics in biological context. Biophys Rev 2021; 13:435-454. [PMID: 34466164 PMCID: PMC8355295 DOI: 10.1007/s12551-021-00822-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Accepted: 07/05/2021] [Indexed: 12/20/2022] Open
Abstract
How proteins respond to pulling forces, or protein nanomechanics, is a key contributor to the form and function of biological systems. Indeed, the conventional view that proteins are able to diffuse in solution does not apply to the many polypeptides that are anchored to rigid supramolecular structures. These tethered proteins typically have important mechanical roles that enable cells to generate, sense, and transduce mechanical forces. To fully comprehend the interplay between mechanical forces and biology, we must understand how protein nanomechanics emerge in living matter. This endeavor is definitely challenging and only recently has it started to appear tractable. Here, I introduce the main in vitro single-molecule biophysics methods that have been instrumental to investigate protein nanomechanics over the last 2 decades. Then, I present the contemporary view on how mechanical force shapes the free energy of tethered proteins, as well as the effect of biological factors such as post-translational modifications and mutations. To illustrate the contribution of protein nanomechanics to biological function, I review current knowledge on the mechanobiology of selected muscle and cell adhesion proteins including titin, talin, and bacterial pilins. Finally, I discuss emerging methods to modulate protein nanomechanics in living matter, for instance by inducing specific mechanical loss-of-function (mLOF). By interrogating biological systems in a causative manner, these new tools can contribute to further place protein nanomechanics in a biological context.
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The Sarcomeric Spring Protein Titin: Biophysical Properties, Molecular Mechanisms, and Genetic Mutations Associated with Heart Failure and Cardiomyopathy. Curr Cardiol Rep 2021; 23:121. [PMID: 34269900 DOI: 10.1007/s11886-021-01550-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 04/07/2021] [Indexed: 01/06/2023]
Abstract
PURPOSE OF REVIEW The giant protein titin forms the "elastic" filament of the sarcomere, essential for the mechanical compliance of the heart muscle. Titin serves a biological spring, and therefore structural modifications of titin affect function of the myocardium and are associated with heart failure and cardiomyopathy. RECENT FINDINGS In this review, we discuss the current understanding of titin's biophysical properties and how modifications contribute to cardiac function and heart failure. In addition, we review the most recent data on the clinical impact and phenotype heterogeneity of TTN truncating variants, including diseases involving striated muscles, and prospects for future therapies. Because of the giant structure of the titin protein and the complexity of its function, titin's role in health and disease is not yet completely understood. Future research efforts need to focus on novel therapeutic approaches able to modulate titin transcriptional and post-translational modification.
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12
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Adewale AO, Ahn YH. Titin N2A Domain and Its Interactions at the Sarcomere. Int J Mol Sci 2021; 22:ijms22147563. [PMID: 34299183 PMCID: PMC8305307 DOI: 10.3390/ijms22147563] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Revised: 07/09/2021] [Accepted: 07/12/2021] [Indexed: 12/16/2022] Open
Abstract
Titin is a giant protein in the sarcomere that plays an essential role in muscle contraction with actin and myosin filaments. However, its utility goes beyond mechanical functions, extending to versatile and complex roles in sarcomere organization and maintenance, passive force, mechanosensing, and signaling. Titin’s multiple functions are in part attributed to its large size and modular structures that interact with a myriad of protein partners. Among titin’s domains, the N2A element is one of titin’s unique segments that contributes to titin’s functions in compliance, contraction, structural stability, and signaling via protein–protein interactions with actin filament, chaperones, stress-sensing proteins, and proteases. Considering the significance of N2A, this review highlights structural conformations of N2A, its predisposition for protein–protein interactions, and its multiple interacting protein partners that allow the modulation of titin’s biological effects. Lastly, the nature of N2A for interactions with chaperones and proteases is included, presenting it as an important node that impacts titin’s structural and functional integrity.
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13
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van der Pijl RJ, van den Berg M, van de Locht M, Shen S, Bogaards SJP, Conijn S, Langlais P, Hooijman PE, Labeit S, Heunks LMA, Granzier H, Ottenheijm CAC. Muscle ankyrin repeat protein 1 (MARP1) locks titin to the sarcomeric thin filament and is a passive force regulator. J Gen Physiol 2021; 153:212403. [PMID: 34152365 PMCID: PMC8222902 DOI: 10.1085/jgp.202112925] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Accepted: 05/19/2021] [Indexed: 12/12/2022] Open
Abstract
Muscle ankyrin repeat protein 1 (MARP1) is frequently up-regulated in stressed muscle, but its effect on skeletal muscle function is poorly understood. Here, we focused on its interaction with the titin–N2A element, found in titin’s molecular spring region. We show that MARP1 binds to F-actin, and that this interaction is stronger when MARP1 forms a complex with titin–N2A. Mechanics and super-resolution microscopy revealed that MARP1 “locks” titin–N2A to the sarcomeric thin filament, causing increased extension of titin’s elastic PEVK element and, importantly, increased passive force. In support of this mechanism, removal of thin filaments abolished the effect of MARP1 on passive force. The clinical relevance of this mechanism was established in diaphragm myofibers of mechanically ventilated rats and of critically ill patients. Thus, MARP1 regulates passive force by locking titin to the thin filament. We propose that in stressed muscle, this mechanism protects the sarcomere from mechanical damage.
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Affiliation(s)
- Robbert J van der Pijl
- Department of Physiology, Amsterdam University Medical Centers, Amsterdam, Netherlands.,Department of Cellular and Molecular Medicine, University of Arizona, Tuscon, AZ
| | - Marloes van den Berg
- Department of Physiology, Amsterdam University Medical Centers, Amsterdam, Netherlands.,Department of Cellular and Molecular Medicine, University of Arizona, Tuscon, AZ
| | - Martijn van de Locht
- Department of Physiology, Amsterdam University Medical Centers, Amsterdam, Netherlands
| | - Shengyi Shen
- Department of Cellular and Molecular Medicine, University of Arizona, Tuscon, AZ
| | - Sylvia J P Bogaards
- Department of Physiology, Amsterdam University Medical Centers, Amsterdam, Netherlands
| | - Stefan Conijn
- Department of Physiology, Amsterdam University Medical Centers, Amsterdam, Netherlands
| | - Paul Langlais
- Division of Endocrinology, University of Arizona, Tucson, AZ
| | - Pleuni E Hooijman
- Department of Physiology, Amsterdam University Medical Centers, Amsterdam, Netherlands
| | - Siegfried Labeit
- Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - Leo M A Heunks
- Intensive Care Medicine, Amsterdam University Medical Centers, Amsterdam, Netherlands
| | - Henk Granzier
- Department of Cellular and Molecular Medicine, University of Arizona, Tuscon, AZ
| | - Coen A C Ottenheijm
- Department of Physiology, Amsterdam University Medical Centers, Amsterdam, Netherlands.,Department of Cellular and Molecular Medicine, University of Arizona, Tuscon, AZ
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Zhou T, Fleming JR, Lange S, Hessel AL, Bogomolovas J, Stronczek C, Grundei D, Ghassemian M, Biju A, Börgeson E, Bullard B, Linke WA, Chen J, Kovermann M, Mayans O. Molecular Characterisation of Titin N2A and Its Binding of CARP Reveals a Titin/Actin Cross-linking Mechanism. J Mol Biol 2021; 433:166901. [PMID: 33647290 PMCID: PMC8052292 DOI: 10.1016/j.jmb.2021.166901] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 02/14/2021] [Accepted: 02/22/2021] [Indexed: 12/16/2022]
Abstract
Striated muscle responds to mechanical overload by rapidly up-regulating the expression of the cardiac ankyrin repeat protein, CARP, which then targets the sarcomere by binding to titin N2A in the I-band region. To date, the role of this interaction in the stress response of muscle remains poorly understood. Here, we characterise the molecular structure of the CARP-receptor site in titin (UN2A) and its binding of CARP. We find that titin UN2A contains a central three-helix bundle fold (ca 45 residues in length) that is joined to N- and C-terminal flanking immunoglobulin domains by long, flexible linkers with partial helical content. CARP binds titin by engaging an α-hairpin in the three-helix fold of UN2A, the C-terminal linker sequence, and the BC loop in Ig81, which jointly form a broad binding interface. Mutagenesis showed that the CARP/N2A association withstands sequence variations in titin N2A and we use this information to evaluate 85 human single nucleotide variants. In addition, actin co-sedimentation, co-transfection in C2C12 cells, proteomics on heart lysates, and the mechanical response of CARP-soaked myofibrils imply that CARP induces the cross-linking of titin and actin myofilaments, thereby increasing myofibril stiffness. We conclude that CARP acts as a regulator of force output in the sarcomere that preserves muscle mechanical performance upon overload stress.
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Affiliation(s)
- Tiankun Zhou
- Department of Biology, University of Konstanz, 78457 Konstanz, Germany
| | | | - Stephan Lange
- Division of Cardiology, School of Medicine, University of California, San Diego 92093, CA, USA; Wallenberg Laboratory, Department of Molecular and Clinical Medicine, Institute of Medicine, University of Gothenburg, Gothenburg 413 45, Sweden
| | - Anthony L Hessel
- Institute of Physiology II, University Hospital Münster, Münster, Germany
| | - Julius Bogomolovas
- School of Medicine, University of California, San Diego, La Jolla, CA 92093, USA; Department of Cognitive and Clinical Neuroscience, Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, 68159 Mannheim, Germany
| | - Chiara Stronczek
- Department of Biology, University of Konstanz, 78457 Konstanz, Germany
| | - David Grundei
- Department of Biology, University of Konstanz, 78457 Konstanz, Germany
| | - Majid Ghassemian
- Department of Chemistry and Biochemistry, University of California, San Diego 92093, CA, USA
| | - Andrea Biju
- Division of Cardiology, School of Medicine, University of California, San Diego 92093, CA, USA
| | - Emma Börgeson
- Wallenberg Laboratory, Department of Molecular and Clinical Medicine, Institute of Medicine, University of Gothenburg, Gothenburg 413 45, Sweden
| | - Belinda Bullard
- Department of Biology, University of York, York YO10 5DD, UK
| | - Wolfgang A Linke
- Institute of Physiology II, University Hospital Münster, Münster, Germany
| | - Ju Chen
- School of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Michael Kovermann
- Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany.
| | - Olga Mayans
- Department of Biology, University of Konstanz, 78457 Konstanz, Germany.
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15
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Stronczek C, Lange S, Bullard B, Wolniak S, Börgeson E, Mayans O, Fleming JR. The N2A region of titin has a unique structural configuration. J Gen Physiol 2021; 153:211969. [PMID: 33836065 PMCID: PMC8042602 DOI: 10.1085/jgp.202012766] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 03/09/2021] [Indexed: 01/04/2023] Open
Abstract
The N2A segment of titin is a main signaling hub in the sarcomeric I-band that recruits various signaling factors and processing enzymes. It has also been proposed to play a role in force production through its Ca2+-regulated association with actin. However, the molecular basis by which N2A performs these functions selectively within the repetitive and extensive titin chain remains poorly understood. Here, we analyze the structure of N2A components and their association with F-actin. Specifically, we characterized the structure of its Ig domains by elucidating the atomic structure of the I81-I83 tandem using x-ray crystallography and computing a homology model for I80. Structural data revealed these domains to present heterogeneous and divergent Ig folds, where I81 and I83 have unique loop structures. Notably, the I81-I83 tandem has a distinct rotational chain arrangement that confers it a unique multi-domain topography. However, we could not identify specific Ca2+-binding sites in these Ig domains, nor evidence of the association of titin N2A components with F-actin in transfected C2C12 myoblasts or C2C12-derived myotubes. In addition, F-actin cosedimentation assays failed to reveal binding to N2A. We conclude that N2A has a unique architecture that predictably supports its selective recruitment of binding partners in signaling, but that its mechanical role through interaction with F-actin awaits validation.
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Affiliation(s)
- Chiara Stronczek
- Department of Biology, University of Konstanz, Konstanz, Germany
| | - Stephan Lange
- Division of Cardiology, School of Medicine, University of California, San Diego, San Diego, CA.,Wallenberg Laboratory, Department of Molecular and Clinical Medicine, Institute of Medicine, University of Gothenburg, Gothenburg, Sweden
| | | | | | - Emma Börgeson
- Wallenberg Laboratory, Department of Molecular and Clinical Medicine, Institute of Medicine, University of Gothenburg, Gothenburg, Sweden
| | - Olga Mayans
- Department of Biology, University of Konstanz, Konstanz, Germany
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16
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Kiss B, Mudra D, Török G, Mártonfalvi Z, Csík G, Herényi L, Kellermayer M. Single-particle virology. Biophys Rev 2020; 12:1141-1154. [PMID: 32880826 PMCID: PMC7471434 DOI: 10.1007/s12551-020-00747-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 08/18/2020] [Indexed: 01/02/2023] Open
Abstract
The development of advanced experimental methodologies, such as optical tweezers, scanning-probe and super-resolved optical microscopies, has led to the evolution of single-molecule biophysics, a field of science that allows direct access to the mechanistic detail of biomolecular structure and function. The extension of single-molecule methods to the investigation of particles such as viruses permits unprecedented insights into the behavior of supramolecular assemblies. Here we address the scope of viral exploration at the level of individual particles. In an era of increased awareness towards virology, single-particle approaches are expected to facilitate the in-depth understanding, and hence combating, of viral diseases.
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Affiliation(s)
- Bálint Kiss
- Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary
| | - Dorottya Mudra
- Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary
| | - György Török
- Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary
| | - Zsolt Mártonfalvi
- Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary
| | - Gabriella Csík
- Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary
| | - Levente Herényi
- Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary
| | - Miklós Kellermayer
- Department of Biophysics and Radiation Biology, Semmelweis University, Budapest, Hungary.
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17
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Sharma S, Subramani S, Popa I. Does protein unfolding play a functional role in vivo? FEBS J 2020; 288:1742-1758. [PMID: 32761965 DOI: 10.1111/febs.15508] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 07/09/2020] [Accepted: 08/03/2020] [Indexed: 12/21/2022]
Abstract
Unfolding and refolding of multidomain proteins under force have yet to be recognized as a major mechanism of function for proteins in vivo. In this review, we discuss the inherent properties of multidomain proteins under a force vector from a structural and functional perspective. We then characterize three main systems where multidomain proteins could play major roles through mechanical unfolding: muscular contraction, cellular mechanotransduction, and bacterial adhesion. We analyze how key multidomain proteins for each system can produce a gain-of-function from the perspective of a fine-tuned quantized response, a molecular battery, delivery of mechanical work through refolding, elasticity tuning, protection and exposure of cryptic sites, and binding-induced mechanical changes. Understanding how mechanical unfolding and refolding affect function will have important implications in designing mechano-active drugs against conditions such as muscular dystrophy, cancer, or novel antibiotics.
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Affiliation(s)
- Sabita Sharma
- Department of Physics, University of Wisconsin-Milwaukee, Milwaukee, WI, USA
| | - Smrithika Subramani
- Department of Physics, University of Wisconsin-Milwaukee, Milwaukee, WI, USA
| | - Ionel Popa
- Department of Physics, University of Wisconsin-Milwaukee, Milwaukee, WI, USA
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18
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N2A Titin: Signaling Hub and Mechanical Switch in Skeletal Muscle. Int J Mol Sci 2020; 21:ijms21113974. [PMID: 32492876 PMCID: PMC7312179 DOI: 10.3390/ijms21113974] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Revised: 05/30/2020] [Accepted: 06/01/2020] [Indexed: 02/06/2023] Open
Abstract
Since its belated discovery, our understanding of the giant protein titin has grown exponentially from its humble beginning as a sarcomeric scaffold to recent recognition of its critical mechanical and signaling functions in active muscle. One uniquely useful model to unravel titin’s functions, muscular dystrophy with myositis (mdm), arose spontaneously in mice as a transposon-like LINE repeat insertion that results in a small deletion in the N2A region of titin. This small deletion profoundly affects hypertrophic signaling and muscle mechanics, thereby providing insights into the function of this specific region and the consequences of its dysfunction. The impact of this mutation is profound, affecting diverse aspects of the phenotype including muscle mechanics, developmental hypertrophy, and thermoregulation. In this review, we explore accumulating evidence that points to the N2A region of titin as a dynamic “switch” that is critical for both mechanical and signaling functions in skeletal muscle. Calcium-dependent binding of N2A titin to actin filaments triggers a cascade of changes in titin that affect mechanical properties such as elastic energy storage and return, as well as hypertrophic signaling. The mdm phenotype also points to the existence of as yet unidentified signaling pathways for muscle hypertrophy and thermoregulation, likely involving titin’s PEVK region as well as the N2A signalosome.
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