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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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2
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Linke WA. Stretching the story of titin and muscle function. J Biomech 2023; 152:111553. [PMID: 36989971 DOI: 10.1016/j.jbiomech.2023.111553] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Accepted: 03/14/2023] [Indexed: 03/29/2023]
Abstract
The discovery of the giant protein titin, also known as connectin, dates almost half a century back. In this review, I recapitulate major advances in the discovery of the titin filaments and the recognition of their properties and function until today. I briefly discuss how our understanding of the layout and interactions of titin in muscle sarcomeres has evolved and review key facts about the titin sequence at the gene (TTN) and protein levels. I also touch upon properties of titin important for the stability of the contractile units and the assembly and maintenance of sarcomeric proteins. The greater part of my discussion centers around the mechanical function of titin in skeletal muscle. I cover milestones of research on titin's role in stretch-dependent passive tension development, recollect the reasons behind the enormous elastic diversity of titin, and provide an update on the molecular mechanisms of titin elasticity, details of which are emerging even now. I reflect on current knowledge of how muscle fibers behave mechanically if titin stiffness is removed and how titin stiffness can be dynamically regulated, such as by posttranslational modifications or calcium binding. Finally, I highlight novel and exciting, but still controversially discussed, insight into the role titin plays in active tension development, such as length-dependent activation and contraction from longer muscle lengths.
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Affiliation(s)
- Wolfgang A Linke
- Institute of Physiology II, University of Münster, Germany; Clinic for Cardiology and Pneumology, University Medical Center Göttingen, Germany; German Centre for Cardiovascular Research, Berlin, Germany.
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3
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Noureddine M, Gehmlich K. Structural and signaling proteins in the Z-disk and their role in cardiomyopathies. Front Physiol 2023; 14:1143858. [PMID: 36935760 PMCID: PMC10017460 DOI: 10.3389/fphys.2023.1143858] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 02/21/2023] [Indexed: 03/06/2023] Open
Abstract
The sarcomere is the smallest functional unit of muscle contraction. It is delineated by a protein-rich structure known as the Z-disk, alternating with M-bands. The Z-disk anchors the actin-rich thin filaments and plays a crucial role in maintaining the mechanical stability of the cardiac muscle. A multitude of proteins interact with each other at the Z-disk and they regulate the mechanical properties of the thin filaments. Over the past 2 decades, the role of the Z-disk in cardiac muscle contraction has been assessed widely, however, the impact of genetic variants in Z-disk proteins has still not been fully elucidated. This review discusses the various Z-disk proteins (alpha-actinin, filamin C, titin, muscle LIM protein, telethonin, myopalladin, nebulette, and nexilin) and Z-disk-associated proteins (desmin, and obscurin) and their role in cardiac structural stability and intracellular signaling. This review further explores how genetic variants of Z-disk proteins are linked to inherited cardiac conditions termed cardiomyopathies.
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Affiliation(s)
- Maya Noureddine
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
- *Correspondence: Maya Noureddine, ; Katja Gehmlich,
| | - Katja Gehmlich
- Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom
- Cardiovascular Medicine, Radcliffe Department of Medicine and British Heart Foundation Centre of Research Excellence Oxford, University of Oxford, Oxford, United Kingdom
- *Correspondence: Maya Noureddine, ; Katja Gehmlich,
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4
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Contributions of Titin and Collagen to Passive Stress in Muscles from mdm Mice with a Small Deletion in Titin’s Molecular Spring. Int J Mol Sci 2022; 23:ijms23168858. [PMID: 36012129 PMCID: PMC9408699 DOI: 10.3390/ijms23168858] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 08/01/2022] [Accepted: 08/07/2022] [Indexed: 12/12/2022] Open
Abstract
Muscular dystrophy with myositis (mdm) is a naturally occurring mutation in the mouse Ttn gene that results in higher passive stress in muscle fibers and intact muscles compared to wild-type (WT). The goal of this study was to test whether alternative splicing of titin exons occurs in mdm muscles, which contain a small deletion in the N2A-PEVK regions of titin, and to test whether splicing changes are associated with an increase in titin-based passive tension. Although higher levels of collagen have been reported previously in mdm muscles, here we demonstrate alternative splicing of titin in mdm skeletal muscle fibers. We identified Z-band, PEVK, and C-terminus Mex5 exons as splicing hotspots in mdm titin using RNA sequencing data and further reported upregulation in ECM-associated genes. We also treated skinned mdm soleus fiber bundles with trypsin, trypsin + KCl, and trypsin + KCL + KI to degrade titin. The results showed that passive stress dropped significantly more after trypsin treatment in mdm fibers (11 ± 1.6 mN/mm2) than in WT fibers (4.8 ± 1 mN/mm2; p = 0.0004). The finding that treatment with trypsin reduces titin-based passive tension more in mdm than in WT fibers supports the hypothesis that exon splicing leads to the expression of a stiffer and shorter titin isoform in mdm fibers. After titin extraction by trypsin + KCl + KI, mdm fibers (6.7 ± 1.27 mN/mm2) had significantly higher collagen-based passive stress remaining than WT fibers (2.6 ± 1.3 mN/mm2; p = 0.0014). We conclude that both titin and collagen contribute to higher passive tension of mdm muscles.
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5
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Filomena MC, Yamamoto DL, Carullo P, Medvedev R, Ghisleni A, Piroddi N, Scellini B, Crispino R, D'Autilia F, Zhang J, Felicetta A, Nemska S, Serio S, Tesi C, Catalucci D, Linke WA, Polishchuk R, Poggesi C, Gautel M, Bang ML. Myopalladin knockout mice develop cardiac dilation and show a maladaptive response to mechanical pressure overload. eLife 2021; 10:e58313. [PMID: 34558411 PMCID: PMC8547954 DOI: 10.7554/elife.58313] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Accepted: 09/23/2021] [Indexed: 12/13/2022] Open
Abstract
Myopalladin (MYPN) is a striated muscle-specific immunoglobulin domain-containing protein located in the sarcomeric Z-line and I-band. MYPN gene mutations are causative for dilated (DCM), hypertrophic, and restrictive cardiomyopathy. In a yeast two-hybrid screening, MYPN was found to bind to titin in the Z-line, which was confirmed by microscale thermophoresis. Cardiac analyses of MYPN knockout (MKO) mice showed the development of mild cardiac dilation and systolic dysfunction, associated with decreased myofibrillar isometric tension generation and increased resting tension at longer sarcomere lengths. MKO mice exhibited a normal hypertrophic response to transaortic constriction (TAC), but rapidly developed severe cardiac dilation and systolic dysfunction, associated with fibrosis, increased fetal gene expression, higher intercalated disc fold amplitude, decreased calsequestrin-2 protein levels, and increased desmoplakin and SORBS2 protein levels. Cardiomyocyte analyses showed delayed Ca2+ release and reuptake in unstressed MKO mice as well as reduced Ca2+ spark amplitude post-TAC, suggesting that altered Ca2+ handling may contribute to the development of DCM in MKO mice.
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Affiliation(s)
- Maria Carmela Filomena
- Institute of Genetic and Biomedical Research (IRGB) - National Research Council (CNR), Milan unitMilanItaly
- IRCCS Humanitas Research HospitalMilanItaly
| | - Daniel L Yamamoto
- Institute of Genetic and Biomedical Research (IRGB) - National Research Council (CNR), Milan unitMilanItaly
| | - Pierluigi Carullo
- Institute of Genetic and Biomedical Research (IRGB) - National Research Council (CNR), Milan unitMilanItaly
- IRCCS Humanitas Research HospitalMilanItaly
| | - Roman Medvedev
- IRCCS Humanitas Research HospitalMilanItaly
- Department of Cardiac Surgery, University of VeronaVeronaItaly
| | - Andrea Ghisleni
- Randall Centre for Cell and Molecular Biophysics, King's College London BHF Centre of Research ExcellenceLondonUnited Kingdom
| | - Nicoletta Piroddi
- Department of Experimental and Clinical Medicine, University of FlorenceFlorenceItaly
| | - Beatrice Scellini
- Department of Experimental and Clinical Medicine, University of FlorenceFlorenceItaly
| | - Roberta Crispino
- Telethon Institute of Genetics and Medicine (TIGEM)PozzuoliItaly
| | | | - Jianlin Zhang
- Department of Medicine, University of California, San DiegoLa JollaUnited States
| | - Arianna Felicetta
- IRCCS Humanitas Research HospitalMilanItaly
- Humanitas UniversityPieve EmanueleItaly
| | | | | | - Chiara Tesi
- Department of Experimental and Clinical Medicine, University of FlorenceFlorenceItaly
| | | | - Wolfgang A Linke
- Institute of Physiology II, University of MuensterMuensterGermany
| | - Roman Polishchuk
- Telethon Institute of Genetics and Medicine (TIGEM)PozzuoliItaly
| | - Corrado Poggesi
- Department of Experimental and Clinical Medicine, University of FlorenceFlorenceItaly
| | - Mathias Gautel
- Randall Centre for Cell and Molecular Biophysics, King's College London BHF Centre of Research ExcellenceLondonUnited Kingdom
| | - Marie-Louise Bang
- Institute of Genetic and Biomedical Research (IRGB) - National Research Council (CNR), Milan unitMilanItaly
- IRCCS Humanitas Research HospitalMilanItaly
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6
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Uapinyoying P, Goecks J, Knoblach SM, Panchapakesan K, Bonnemann CG, Partridge TA, Jaiswal JK, Hoffman EP. A long-read RNA-seq approach to identify novel transcripts of very large genes. Genome Res 2020; 30:885-897. [PMID: 32660935 PMCID: PMC7370890 DOI: 10.1101/gr.259903.119] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Accepted: 05/22/2020] [Indexed: 12/15/2022]
Abstract
RNA-seq is widely used for studying gene expression, but commonly used sequencing platforms produce short reads that only span up to two exon junctions per read. This makes it difficult to accurately determine the composition and phasing of exons within transcripts. Although long-read sequencing improves this issue, it is not amenable to precise quantitation, which limits its utility for differential expression studies. We used long-read isoform sequencing combined with a novel analysis approach to compare alternative splicing of large, repetitive structural genes in muscles. Analysis of muscle structural genes that produce medium (Nrap: 5 kb), large (Neb: 22 kb), and very large (Ttn: 106 kb) transcripts in cardiac muscle, and fast and slow skeletal muscles identified unannotated exons for each of these ubiquitous muscle genes. This also identified differential exon usage and phasing for these genes between the different muscle types. By mapping the in-phase transcript structures to known annotations, we also identified and quantified previously unannotated transcripts. Results were confirmed by endpoint PCR and Sanger sequencing, which revealed muscle-type-specific differential expression of these novel transcripts. The improved transcript identification and quantification shown by our approach removes previous impediments to studies aimed at quantitative differential expression of ultralong transcripts.
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Affiliation(s)
- Prech Uapinyoying
- Center for Genetic Medicine Research, Children's Research Institute, Children's National Health System, Washington, D.C. 20010, USA.,Department of Genomics and Precision Medicine, The George Washington University School of Medicine and Health Sciences, Washington, D.C. 20052, USA.,Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Jeremy Goecks
- Computational Biology Program, Oregon Health and Science University, Portland, Oregon 97239, USA
| | - Susan M Knoblach
- Center for Genetic Medicine Research, Children's Research Institute, Children's National Health System, Washington, D.C. 20010, USA.,Department of Genomics and Precision Medicine, The George Washington University School of Medicine and Health Sciences, Washington, D.C. 20052, USA
| | - Karuna Panchapakesan
- Center for Genetic Medicine Research, Children's Research Institute, Children's National Health System, Washington, D.C. 20010, USA
| | - Carsten G Bonnemann
- Center for Genetic Medicine Research, Children's Research Institute, Children's National Health System, Washington, D.C. 20010, USA.,Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Terence A Partridge
- Center for Genetic Medicine Research, Children's Research Institute, Children's National Health System, Washington, D.C. 20010, USA.,Department of Genomics and Precision Medicine, The George Washington University School of Medicine and Health Sciences, Washington, D.C. 20052, USA
| | - Jyoti K Jaiswal
- Center for Genetic Medicine Research, Children's Research Institute, Children's National Health System, Washington, D.C. 20010, USA.,Department of Genomics and Precision Medicine, The George Washington University School of Medicine and Health Sciences, Washington, D.C. 20052, USA
| | - Eric P Hoffman
- Center for Genetic Medicine Research, Children's Research Institute, Children's National Health System, Washington, D.C. 20010, USA.,Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, Binghamton University, Binghamton, New York 13902, USA
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7
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Shen Z, Wang Y, Guo Z, Tan T, Zhang Y. Novel tyrosinase inhibitory peptide with free radical scavenging ability. J Enzyme Inhib Med Chem 2020; 34:1633-1640. [PMID: 31496313 PMCID: PMC6746264 DOI: 10.1080/14756366.2019.1661401] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Tyrosinase is a key enzyme involved in melanin synthesis. Therefore, various tyrosinase inhibitors have been screened by researchers in recent years. In the present study, we discovered a novel tyrosinase inhibitor, a peptide ECGYF (named EF-5), with free radical scavenging ability. The effect of tyrosinase inhibition by EF-5 was stronger than that of arbutin and glutathione, when analyzed both in vitro (IC50: 0.46 mM) and in vivo. The UV-Vis absorption and circular dichroism spectroscopies indicated that EF-5 interacted with tyrosinase in a different way as that of glutathione. The results of molecular docking showed that the binding between EF-5 and tyrosinase was determined majorly by hydrogen bonds and hydrophobic interactions. EF-5 had also retained its ability to scavenge both hydroxyl and superoxide radicals in vitro and was found to be nontoxic to cells, as revealed by the MTT assay. These features suggested that the EF-5 peptide may serve as a safe and effective alternative as a tyrosinase inhibitor.
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Affiliation(s)
- Zhiwei Shen
- Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences , Shanghai , China.,University of Chinese Academy of Sciences , Beijing , China
| | - Yujiao Wang
- Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences , Shanghai , China.,University of Chinese Academy of Sciences , Beijing , China
| | - Zhen Guo
- Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences , Shanghai , China.,University of Chinese Academy of Sciences , Beijing , China
| | - Tingyuan Tan
- Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences , Shanghai , China.,University of Chinese Academy of Sciences , Beijing , China
| | - Yi Zhang
- Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences , Shanghai , China.,Zhangjiang Lab, Shanghai Advanced Research Institute, Chinese Academy of Sciences , Shanghai , China
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8
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Wang S, Sha X, Yu S, Zhao Y. Nanocalorimeters for biomolecular analysis and cell metabolism monitoring. BIOMICROFLUIDICS 2020; 14:011503. [PMID: 32038739 PMCID: PMC6994269 DOI: 10.1063/1.5134870] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Accepted: 01/10/2020] [Indexed: 05/28/2023]
Abstract
Nanocalorimeters, or microfabricated calorimeters, provide a promising way to characterize the thermal process of biological processes, such as biomolecule interactions and cellular metabolic activities. They enabled miniaturized heat measurement onto a chip device with potential benefits including low sample consumption, low cost, portability, and high throughput. Over the past few decades, researchers have tried to improve nanocalorimeters' performance, in terms of sensitivity, accuracy, and detection resolution, by exploring different sensing methods, thermal insulation techniques, and liquid handling methods. The enhanced devices resulted in new applications in recent years, and here we have summarized the performance parameters and applications based on categories. Finally, we have listed the current technical difficulties in nanocalorimeter research and hope for future solutions to overcome them.
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Affiliation(s)
- Shuyu Wang
- Department of Control Engineering, Northeastern University, Qinhuangdao, Hebei 066001, People’s Republic of China
| | - Xiaopeng Sha
- Department of Control Engineering, Northeastern University, Qinhuangdao, Hebei 066001, People’s Republic of China
| | - Shifeng Yu
- Department of Mechanical Engineering, Columbia University, New York, New York 10027, USA
| | - Yuliang Zhao
- Department of Control Engineering, Northeastern University, Qinhuangdao, Hebei 066001, People’s Republic of China
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9
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Ciferri A, Crumbliss AL. A Supramolecular Polymerization Approach to the Growth of the Myofibril. Front Chem 2019; 7:487. [PMID: 31380341 PMCID: PMC6646515 DOI: 10.3389/fchem.2019.00487] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Accepted: 06/25/2019] [Indexed: 11/13/2022] Open
Abstract
Extended linear structures self-assemble by the multi-stage-open-association mechanism of supramolecular polymerization (MSOA). Application of the model requires the identification of a repeating unit, the main-chain supramolecular bond, and the binding constant. The strength of the bond and the degree of polymerization become extremely large when multiple sites for non-covalent interactions occur. These expectations had been previously verified in the case of the neuronal axon, for which the above parameters were assessed from its known molecular structure. The more complex case of the myofibril is analyzed here. The specific interactions that connect neighboring sarcomers have been a matter of debate. Recent work has focused on the bond between titin and α-actinin localized at the terminal Z-zones of each sarcomer. Elaboration of literature data suggests that titin-α-actinin interactions do bridge neighboring sarcomers, promoting the polymerization of myofibrils that attain macroscopic dimensions consistently with the MSOA predictions. The rationale for the complex structuration of single sarcomers is discussed.
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Affiliation(s)
- Alberto Ciferri
- Chemistry Department, Duke University, Durham, NC, United States
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10
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Abstract
Myotilin is a component of the sarcomere where it plays an important role in organisation and maintenance of Z-disk integrity. This involves direct binding to F-actin and filamin C, a function mediated by its Ig domain pair. While the structures of these two individual domains are known, information about their relative orientation and flexibility remains limited. We set on to characterise the Ig domain pair of myotilin with emphasis on its molecular structure, dynamics and phylogeny. First, sequence conservation analysis of myotilin shed light on the molecular basis of myotilinopathies and revealed several motifs in Ig domains found also in I-band proteins. In particular, a highly conserved Glu344 mapping to Ig domain linker, was identified as a critical component of the inter-domain hinge mechanism. Next, SAXS and molecular dynamics revealed that Ig domain pair exists as a multi-conformation species with dynamic exchange between extended and compact orientations. Mutation of AKE motif to AAA further confirmed its impact on inter-domain flexibility. We hypothesise that the conformational plasticity of the Ig domain pair in its unbound form is part of the binding partner recognition mechanism.
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11
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α-Actinin/titin interaction: A dynamic and mechanically stable cluster of bonds in the muscle Z-disk. Proc Natl Acad Sci U S A 2017; 114:1015-1020. [PMID: 28096424 DOI: 10.1073/pnas.1612681114] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Stable anchoring of titin within the muscle Z-disk is essential for preserving muscle integrity during passive stretching. One of the main candidates for anchoring titin in the Z-disk is the actin cross-linker α-actinin. The calmodulin-like domain of α-actinin binds to the Z-repeats of titin. However, the mechanical and kinetic properties of this important interaction are still unknown. Here, we use a dual-beam optical tweezers assay to study the mechanics of this interaction at the single-molecule level. A single interaction of α-actinin and titin turns out to be surprisingly weak if force is applied. Depending on the direction of force application, the unbinding forces can more than triple. Our results suggest a model where multiple α-actinin/Z-repeat interactions cooperate to ensure long-term stable titin anchoring while allowing the individual components to exchange dynamically.
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12
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Haywood NJ, Wolny M, Rogers B, Trinh CH, Shuping Y, Edwards TA, Peckham M. Hypertrophic cardiomyopathy mutations in the calponin-homology domain of ACTN2 affect actin binding and cardiomyocyte Z-disc incorporation. Biochem J 2016; 473:2485-93. [PMID: 27287556 PMCID: PMC4980809 DOI: 10.1042/bcj20160421] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Revised: 06/06/2016] [Accepted: 06/09/2016] [Indexed: 11/17/2022]
Abstract
α-Actinin-2 (ACTN2) is the only muscle isoform of α-actinin expressed in cardiac muscle. Mutations in this protein have been implicated in mild to moderate forms of hypertrophic cardiomyopathy (HCM). We have investigated the effects of two mutations identified from HCM patients, A119T and G111V, on the secondary and tertiary structure of a purified actin binding domain (ABD) of ACTN2 by circular dichroism and X-ray crystallography, and show small but distinct changes for both mutations. We also find that both mutants have reduced F-actin binding affinity, although the differences are not significant. The full length mEos2 tagged protein expressed in adult cardiomyocytes shows that both mutations additionally affect Z-disc localization and dynamic behaviour. Overall, these two mutations have small effects on structure, function and behaviour, which may contribute to a mild phenotype for this disease.
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Affiliation(s)
- Natalie J Haywood
- Astbury Centre for Structural Molecular Biology and the School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, U.K
| | - Marcin Wolny
- Astbury Centre for Structural Molecular Biology and the School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, U.K
| | - Brendan Rogers
- Astbury Centre for Structural Molecular Biology and the School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, U.K
| | - Chi H Trinh
- Astbury Centre for Structural Molecular Biology and the School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, U.K
| | - Yu Shuping
- Astbury Centre for Structural Molecular Biology and the School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, U.K
| | - Thomas A Edwards
- Astbury Centre for Structural Molecular Biology and the School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, U.K
| | - Michelle Peckham
- Astbury Centre for Structural Molecular Biology and the School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, U.K.
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13
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Thompson PM, Beck MR, Campbell SL. Protein-protein interaction analysis by nuclear magnetic resonance spectroscopy. Methods Mol Biol 2015; 1278:267-279. [PMID: 25859955 DOI: 10.1007/978-1-4939-2425-7_16] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Nuclear magnetic resonance (NMR) has continued to evolve as a powerful method, with an increase in the number of pulse sequences and techniques available to study protein-protein interactions. In this chapter, a straightforward method to map a protein-protein interface and design a structural model is described, using chemical shift perturbation, paramagnetic relaxation enhancement, and data-driven docking.
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Affiliation(s)
- Peter M Thompson
- Department of Biochemistry and Biophysics, University of North Carolina, 120 Mason Farm Road, CB # 7260, 3100A-C Genetic Medicine, Chapel Hill, NC, 27599, USA
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14
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Abstract
Circular dichroism (CD) spectroscopy is a useful technique for studying protein-protein interactions in solution. CD in the far ultraviolet region (178-260 nm) arises from the amides of the protein backbone and is sensitive to the conformation of the protein. Thus, CD can determine whether there are changes in the conformation of proteins when they interact. Changes in the conformation of the protein complexes as a function of temperature or added denaturants, compared to the individual proteins, can be used to determine binding constants. CD bands in the near ultraviolet (350-260 nm) and visible regions arise from aromatic amino acid side chains and prosthetic groups. There are often changes in these regions when proteins bind to each other. Because CD is a quantitative technique, these changes are directly proportional to the amount of the protein-protein complexes formed and thus also can be used to estimate binding constants.
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Affiliation(s)
- Norma J Greenfield
- Associate Professor (retired), Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, Rutgers University, 675 Hoes Lane West, Piscataway, NJ, 08854-8021, USA,
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15
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Ribeiro EDA, Pinotsis N, Ghisleni A, Salmazo A, Konarev PV, Kostan J, Sjöblom B, Schreiner C, Polyansky AA, Gkougkoulia EA, Holt MR, Aachmann FL, Zagrović B, Bordignon E, Pirker KF, Svergun DI, Gautel M, Djinović-Carugo K. The structure and regulation of human muscle α-actinin. Cell 2014; 159:1447-60. [PMID: 25433700 PMCID: PMC4259493 DOI: 10.1016/j.cell.2014.10.056] [Citation(s) in RCA: 144] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Revised: 10/01/2014] [Accepted: 10/24/2014] [Indexed: 11/29/2022]
Abstract
The spectrin superfamily of proteins plays key roles in assembling the actin cytoskeleton in various cell types, crosslinks actin filaments, and acts as scaffolds for the assembly of large protein complexes involved in structural integrity and mechanosensation, as well as cell signaling. α-actinins in particular are the major actin crosslinkers in muscle Z-disks, focal adhesions, and actin stress fibers. We report a complete high-resolution structure of the 200 kDa α-actinin-2 dimer from striated muscle and explore its functional implications on the biochemical and cellular level. The structure provides insight into the phosphoinositide-based mechanism controlling its interaction with sarcomeric proteins such as titin, lays a foundation for studying the impact of pathogenic mutations at molecular resolution, and is likely to be broadly relevant for the regulation of spectrin-like proteins. Structure of human α-actinin-2 in an autoinhibited closed conformation Facilitation of PIP2-induced allosteric modulation for opening and titin binding Essentiality of structural flexibility for crosslinking antiparallel F-actin Relevance for the intramolecular pseudoligand regulation mechanism of the spectrin family
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Affiliation(s)
- Euripedes de Almeida Ribeiro
- Department of Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, Campus Vienna Biocenter 5, 1030 Vienna, Austria
| | - Nikos Pinotsis
- Department of Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, Campus Vienna Biocenter 5, 1030 Vienna, Austria
| | - Andrea Ghisleni
- British Heart Foundation Centre of Research Excellence, Randall Division for Cell and Molecular Biophysics and Cardiovascular Division, King's College London, London SE1 1UL, UK
| | - Anita Salmazo
- Department of Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, Campus Vienna Biocenter 5, 1030 Vienna, Austria
| | - Petr V Konarev
- European Molecular Biology Laboratory, Deutsches Elektronen-Synchrotron, Notkestrasse 85, 22603 Hamburg, Germany
| | - Julius Kostan
- Department of Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, Campus Vienna Biocenter 5, 1030 Vienna, Austria
| | - Björn Sjöblom
- Department of Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, Campus Vienna Biocenter 5, 1030 Vienna, Austria
| | - Claudia Schreiner
- Department of Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, Campus Vienna Biocenter 5, 1030 Vienna, Austria
| | - Anton A Polyansky
- Department of Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, Campus Vienna Biocenter 5, 1030 Vienna, Austria; M.M. Shemyakin and Yu.A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow 117997, Russia
| | - Eirini A Gkougkoulia
- Department of Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, Campus Vienna Biocenter 5, 1030 Vienna, Austria
| | - Mark R Holt
- British Heart Foundation Centre of Research Excellence, Randall Division for Cell and Molecular Biophysics and Cardiovascular Division, King's College London, London SE1 1UL, UK
| | - Finn L Aachmann
- Department of Biotechnology, Norwegian University of Science and Technology, Sem Sælands vei 6/8, 7491 Trondheim, Norway
| | - Bojan Zagrović
- Department of Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, Campus Vienna Biocenter 5, 1030 Vienna, Austria
| | - Enrica Bordignon
- Laboratory of Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich, Switzerland; Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Katharina F Pirker
- Division of Biochemistry, Department of Chemistry, University of Natural Resources and Life Sciences, Muthgasse 18, 1190 Vienna, Austria
| | - Dmitri I Svergun
- European Molecular Biology Laboratory, Deutsches Elektronen-Synchrotron, Notkestrasse 85, 22603 Hamburg, Germany
| | - Mathias Gautel
- British Heart Foundation Centre of Research Excellence, Randall Division for Cell and Molecular Biophysics and Cardiovascular Division, King's College London, London SE1 1UL, UK.
| | - Kristina Djinović-Carugo
- Department of Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, Campus Vienna Biocenter 5, 1030 Vienna, Austria; Department of Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, 1000 Ljubljana, Slovenia.
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16
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Garcia-Pavia P, Cobo-Marcos M, Guzzo-Merello G, Gomez-Bueno M, Bornstein B, Lara-Pezzi E, Segovia J, Alonso-Pulpon L. Genetics in dilated cardiomyopathy. Biomark Med 2014; 7:517-33. [PMID: 23905888 DOI: 10.2217/bmm.13.77] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Discoveries made during the last 20 years have revealed a genetic origin in many cases of dilated cardiomyopathy (DCM). Currently, over 40 genes have been associated with the disease. Mutations in DCM-causing genes induce the condition through a variety of different pathological pathways with complex and not completely understood mechanisms. Genes that encode for sarcomeric, cytoskeletal, nuclear membrane, dystrophin-associated glycoprotein complex and desmosomal proteins are the principal genes involved. In this review we discuss the most frequent DCM-causing genes. We propose a classification in which DCM genes are considered as being major or minor genes according to their mutation frequency and the available supporting evidence. The main phenotypic characteristics associated with each gene are discussed.
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Affiliation(s)
- Pablo Garcia-Pavia
- Heart Failure & Cardiomyopathy Unit, Department of Cardiology, Hospital Universitario Puerta de Hierro, Madrid, Spain.
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17
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Abstract
Giant muscle proteins (e.g., titin, nebulin, and obscurin) play a seminal role in muscle elasticity, stretch response, and sarcomeric organization. Each giant protein consists of multiple tandem structural domains, usually arranged in a modular fashion spanning 500 kDa to 4 MDa. Although many of the domains are similar in structure, subtle differences create a unique function of each domain. Recent high and low resolution structural and dynamic studies now suggest more nuanced overall protein structures than previously realized. These findings show that atomic structure, interactions between tandem domains, and intrasarcomeric environment all influence the shape, motion, and therefore function of giant proteins. In this article we will review the current understanding of titin, obscurin, and nebulin structure, from the atomic level through the molecular level.
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Affiliation(s)
- Logan C Meyer
- Department of Chemistry and Biochemistry, James Madison University Harrisonburg, VA, USA
| | - Nathan T Wright
- Department of Chemistry and Biochemistry, James Madison University Harrisonburg, VA, USA
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18
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Travers T, Shao H, Wells A, Camacho C. Modeling the assembly of the multiple domains of α-actinin-4 and its role in actin cross-linking. Biophys J 2013; 104:705-15. [PMID: 23442921 PMCID: PMC3566466 DOI: 10.1016/j.bpj.2012.12.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2012] [Revised: 12/04/2012] [Accepted: 12/05/2012] [Indexed: 12/30/2022] Open
Abstract
The assembly of proteins into multidomain complexes is critical for their function. In eukaryotic nonmuscle cells, regulation of the homodimeric actin cross-linking protein α-actinin-4 (ACTN4) during cell migration involves signaling receptors with intrinsic tyrosine kinase activity, yet the underlying molecular mechanisms are poorly understood. As a first step to address the latter, we validate here an atomic model for the ACTN4 end region, which corresponds to a ternary complex between the N-terminal actin-binding domain (ABD) and an adjacent helical neck region of one monomer, and the C-terminal calmodulin-like domain of the opposite antiparallel monomer. Mutagenesis experiments designed to disrupt this ternary complex confirm that its formation reduces binding to F-actin. Molecular dynamics simulations show that the phosphomimic mutation Y265E increases actin binding by breaking several interactions that tether the two calponin homology domains into a closed ABD conformation. Simulations also show a disorder-to-order transition in the double phosphomimic mutant Y4E/Y31E of the 45-residue ACTN4 N-terminal region, which can inhibit actin binding by latching both calponin homology domains more tightly. Collectively, these studies provide a starting point for understanding the role of external cues in regulating ACTN4, with different phenotypes resulting from changes in the multidomain assembly of the protein.
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Affiliation(s)
- Timothy Travers
- Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Hanshuang Shao
- Department of Pathology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Alan Wells
- Department of Pathology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Carlos J. Camacho
- Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
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19
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Beck MR, Otey CA, Campbell SL. Structural characterization of the interactions between palladin and α-actinin. J Mol Biol 2011; 413:712-25. [PMID: 21925511 PMCID: PMC3226707 DOI: 10.1016/j.jmb.2011.08.059] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2011] [Revised: 08/29/2011] [Accepted: 08/30/2011] [Indexed: 12/11/2022]
Abstract
The interaction between α-actinin and palladin, two actin-cross-linking proteins, is essential for proper bidirectional targeting of these proteins. As a first step toward understanding the role of this complex in organizing cytoskeletal actin, we have characterized binding interactions between the EF-hand domain of α-actinin (Act-EF34) and peptides derived from palladin and generated an NMR-derived structural model for the Act-EF34/palladin peptide complex. The critical binding site residues are similar to an α-actinin binding motif previously suggested for the complex between Act-EF34 and titin Z-repeats. The structure-based model of the Act-EF34/palladin peptide complex expands our understanding of binding specificity between the scaffold protein α-actinin and various ligands, which appears to require an α-helical motif containing four hydrophobic residues, common to many α-actinin ligands. We also provide evidence that the Family X mutation in palladin, associated with a highly penetrant form of pancreatic cancer, does not interfere with α-actinin binding.
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Affiliation(s)
- Moriah R. Beck
- Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA
| | - Carol A. Otey
- Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA
- Department of Cell and Molecular Physiology, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA
| | - Sharon L. Campbell
- Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA
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20
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Kontrogianni-Konstantopoulos A, Ackermann MA, Bowman AL, Yap SV, Bloch RJ. Muscle giants: molecular scaffolds in sarcomerogenesis. Physiol Rev 2009; 89:1217-67. [PMID: 19789381 PMCID: PMC3076733 DOI: 10.1152/physrev.00017.2009] [Citation(s) in RCA: 186] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Myofibrillogenesis in striated muscles is a highly complex process that depends on the coordinated assembly and integration of a large number of contractile, cytoskeletal, and signaling proteins into regular arrays, the sarcomeres. It is also associated with the stereotypical assembly of the sarcoplasmic reticulum and the transverse tubules around each sarcomere. Three giant, muscle-specific proteins, titin (3-4 MDa), nebulin (600-800 kDa), and obscurin (approximately 720-900 kDa), have been proposed to play important roles in the assembly and stabilization of sarcomeres. There is a large amount of data showing that each of these molecules interacts with several to many different protein ligands, regulating their activity and localizing them to particular sites within or surrounding sarcomeres. Consistent with this, mutations in each of these proteins have been linked to skeletal and cardiac myopathies or to muscular dystrophies. The evidence that any of them plays a role as a "molecular template," "molecular blueprint," or "molecular ruler" is less definitive, however. Here we review the structure and function of titin, nebulin, and obscurin, with the literature supporting a role for them as scaffolding molecules and the contradictory evidence regarding their roles as molecular guides in sarcomerogenesis.
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21
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Chi RJ, Simon AR, Bienkiewicz EA, Felix A, Keller TCS. Smooth muscle titin Zq domain interaction with the smooth muscle alpha-actinin central rod. J Biol Chem 2008; 283:20959-67. [PMID: 18519573 DOI: 10.1074/jbc.m709621200] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Actin-myosin II filament-based contractile structures in striated muscle, smooth muscle, and nonmuscle cells contain the actin filament-cross-linking protein alpha-actinin. In striated muscle Z-disks, alpha-actinin interacts with N-terminal domains of titin to provide a structural linkage crucial for the integrity of the sarcomere. We previously discovered a long titin isoform, originally smitin, hereafter sm-titin, in smooth muscle and demonstrated that native sm-titin interacts with C-terminal EF hand region and central rod R2-R3 spectrin-like repeat region sites in alpha-actinin. Reverse transcription-PCR analysis of RNA from human adult smooth muscles and cultured rat smooth muscle cells and Western blot analysis with a domain-specific antibody presented here revealed that sm-titin contains the titin gene-encoded Zq domain that may bind to the alpha-actinin R2-R3 central rod domain as well as Z-repeat domains that bind to the EF hand region. We investigated whether the sm-titin Zq domain binds to alpha-actinin R2 and R3 spectrin repeat-like domain loops that lie in proximity with two-fold symmetry on the surface of the central rod. Mutations in alpha-actinin R2 and R3 domain loop residues decreased interaction with expressed sm-titin Zq domain in glutathione S-transferase pull-down and solid phase binding assays. Alanine mutation of a region of the Zq domain with high propensity for alpha-helix formation decreased apparent Zq domain dimer formation and decreased Zq interaction with the alpha-actinin R2-R3 region in surface plasmon resonance assays. We present a model in which two sm-titin Zq domains interact with each other and with the two R2-R3 sites in the alpha-actinin central rod.
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Affiliation(s)
- Richard J Chi
- Department of Biological Science, College of Medicine, Florida State University, Tallahassee, FL 32306, USA
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22
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Delbarre-Ladrat C, Chéret R, Taylor R, Verrez-Bagnis V. Trends in Postmortem Aging in Fish: Understanding of Proteolysis and Disorganization of the Myofibrillar Structure. Crit Rev Food Sci Nutr 2006; 46:409-21. [PMID: 16891212 DOI: 10.1080/10408390591000929] [Citation(s) in RCA: 165] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Postmortem tenderization is caused by enzymatic degradation of key structural proteins in myofibrils as well as in extracellular matrix, and of proteins involved in intermyofibrillar linkages and linkages between myofibrils and the sarcolemma. The function of these proteins is to maintain the structural integrity of myofibrils. Current data indicate that calpains and cathepsins may be responsible for degradation of these proteins. Other phenomena occurring in cells postmortem (pH drop, sarcoplasmic Ca2+ increase, osmotic pressure rise, oxidative processes) may act in synergy with proteases. Our understanding of the underlying mechanisms of muscle degradation should be improved for an accurate evaluation of the postmortem muscle changes and consequently of the fish quality.
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23
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Chi RJ, Olenych SG, Kim K, Keller TCS. Smooth muscle alpha-actinin interaction with smitin. Int J Biochem Cell Biol 2005; 37:1470-82. [PMID: 15833278 DOI: 10.1016/j.biocel.2005.02.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2004] [Accepted: 02/14/2005] [Indexed: 11/19/2022]
Abstract
Actin-myosin II filament-based contractile structures in striated muscle, smooth muscle, and nonmuscle cells also contain the actin filament-crosslinking protein alpha-actinin. In striated muscle sarcomeres, interactions between the myosin-binding protein titin and alpha-actinin in the Z-line provide an important structural linkage. We previously discovered a titin-like protein, smitin, associated with the contractile apparatus of smooth muscle cells. Purified native smooth muscle alpha-actinin binds with nanomolar affinity to smitin in smitin-myosin coassemblies in vitro. Smooth muscle alpha-actinin also interacts with striated muscle titin. In contrast to striated muscle alpha-actinin interaction with titin and smitin, which is significantly enhanced by PIP2, smooth muscle alpha-actinin interacts with smitin and titin equally well in the presence and absence of PIP2. Using expressed regions of smooth muscle alpha-actinin, we have demonstrated smitin-binding sites in the smooth muscle alpha-actinin R2-R3 spectrin-like repeat rod domain and a C-terminal domain formed by cryptic EF-hand structures. These smitin-binding sites are highly homologous to the titin-binding sites of striated muscle alpha-actinin. Our results suggest that direct interaction between alpha-actinin and titin or titin-like proteins is a common feature of actin-myosin II contractile structures in striated muscle and smooth muscle cells and that the molecular bases for alpha-actinin interaction with these proteins are similar, although regulation of these interactions may differ according to tissue.
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Affiliation(s)
- Richard J Chi
- Department of Biological Science, Florida State University, Tallahassee, FL 32306-4370, USA
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24
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Raynaud F, Astier C, Benyamin Y. Evidence for a direct but sequential binding of titin to tropomyosin and actin filaments. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2004; 1700:171-8. [PMID: 15262226 DOI: 10.1016/j.bbapap.2004.05.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2003] [Revised: 03/23/2004] [Accepted: 05/06/2004] [Indexed: 11/23/2022]
Abstract
Titin is a giant molecule that spans half a sarcomere, establishing several specific bindings with both structural and contractile myofibrillar elements. It has been demonstrated that this giant protein plays a major role in striated muscle cell passive tension and contractile filament alignment. The in vitro interaction of titin with a new partner (tropomyosin) reported here is reinforced by our recent in vitro motility study using reconstituted Ca-regulated thin filaments, myosin and a native 800-kDa titin fragment. In the presence of the tropomyosin-troponin complex, the actin filament movement onto coated S1 is improved by the titin fragment. Here, we found that two purified native titin fragments of 150 and 800 kDa, covering respectively the N1-line and the N2-line/PEVK region in the I-band and known to contain actin-binding sites, directly bind tropomyosin in the absence of actin. We have also shown that binding of the 800-kDa fragment with filamentous actin inhibited the subsequent interaction of tropomyosin with actin, as judged by cosedimentation. However, this was not the case if the complex of actin and tropomyosin was formed before the addition of the 800-kDa fragment. We thus conclude that a sequential arrangement of contacts exists between parts of the titin I-band region, tropomyosin and actin in the thin filament.
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Affiliation(s)
- Fabrice Raynaud
- UMR 5539, cc107, University of Montpellier 2 place Eugéne Bataillon, 34090 Montpellier, France.
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25
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Rönty M, Taivainen A, Moza M, Otey CA, Carpén O. Molecular analysis of the interaction between palladin and alpha-actinin. FEBS Lett 2004; 566:30-4. [PMID: 15147863 DOI: 10.1016/j.febslet.2004.04.006] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2004] [Revised: 03/30/2004] [Accepted: 04/02/2004] [Indexed: 12/11/2022]
Abstract
Palladin is a novel component of stress fiber dense regions. Antisense and transient overexpression studies have indicated an important role for palladin in the regulation of actin cytoskeleton. Palladin colocalizes and coimmunoprecipitates with alpha-actinin, a dense region component, but the molecular details and functional significance of the interaction have not been studied. We show here a direct association between the two proteins and have mapped the binding site within a short sequence of palladin and in the carboxy-terminal calmodulin domain of alpha-actinin. Using transfection-based targeting assays, we show that palladin is involved in targeting of alpha-actinin to specific subcellular foci indicating a functional interplay between the two actin-associated proteins.
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Affiliation(s)
- Mikko Rönty
- Biomedicum Helsinki, Department of Pathology, University of Helsinki and Helsinki University Central Hospital, Helsinki, Finland.
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26
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Rünzler D, Huber C, Moll D, Köhler G, Sára M. Biophysical characterization of the entire bacterial surface layer protein SbsB and its two distinct functional domains. J Biol Chem 2003; 279:5207-15. [PMID: 14625307 DOI: 10.1074/jbc.m308819200] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The crystalline bacterial cell surface layer (S-layer) protein SbsB of Geobacillus stearothermophilus PV72/p2 was dissected into an N-terminal part defined by the three consecutive S-layer homologous motifs and the remaining large C-terminal part. Both parts of the mature protein were produced as separate recombinant proteins (rSbsB(1-178) and rSbsB(177-889)) and compared with the full-length form rSbsB(1-889) (rSbsB). Evidence for functional and structural integrity of the two truncated forms was provided by optical spectroscopic methods and electron microscopy. In particular, binding of the secondary cell wall polymer revealed a high affinity dissociation constant of 3 nm and could be assigned solely to the soluble rSbsB(1-178), whereas rSbsB(177-889) self-assembled into the same lattice as the full-length protein. Furthermore, thermal as well as guanidinium hydrochloride induced equilibrium unfolding profiles monitored by intrinsic fluorescence, and circular dichroism spectroscopy allowed characterization of rSbsB(1-178) as an alpha-helical protein with a single cooperative unfolding transition yielding a DeltaG value of 26.5 kJ mol(-1). The C-terminal rSbsB(177-889) could be characterized as a beta-sheet protein with typical multidomain unfolding, which is partially less stable as stand-alone protein. In general, the truncated forms showed identical properties compared with the full-length rSbsB with respect to structure and function. Consequently, rSbsB is characterized by its two functionally and structurally separated parts, the specific secondary cell wall polymer binding rSbsB(1-178) and the larger rSbsB(177-889) responsible for formation of the crystalline array.
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Affiliation(s)
- Dominik Rünzler
- Institute for Theoretical Chemistry and Structural Biology, University of Vienna, Campus Vienna Biocenter 6/1, Vienna 1030, Austria.
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27
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Luther PK, Squire JM. Muscle Z-band ultrastructure: titin Z-repeats and Z-band periodicities do not match. J Mol Biol 2002; 319:1157-64. [PMID: 12079354 DOI: 10.1016/s0022-2836(02)00372-8] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Vertebrate muscle Z-bands show zig-zag densities due to different sets of alpha-actinin cross-links between anti-parallel actin molecules. Their axial extent varies with muscle and fibre type: approximately 50 nm in fast and approximately 100 nm in cardiac and slow muscles, corresponding to the number of alpha-actinin cross-links present. Fish white (fast) muscle Z-bands have two sets of alpha-actinin links, mammalian slow muscle Z-bands have six. The modular structure of the approximately 3 MDa protein titin that spans from M-band to Z-band correlates with the axial structure of the sarcomere; it may form the template for myofibril assembly. The Z-band-located amino-terminal 80 kDa of titin includes 45 residue repeating modules (Z-repeats) that are expressed differentially; heart, slow and fast muscles have seven, four to six and two to four Z-repeats, respectively. Gautel et al. proposed a Z-band model in which each Z-repeat links to one level of alpha-actinin cross-links, requiring that the axial extent of a Z-repeat is the same as the axial separation of alpha-actinin layers, of which there are two in every actin crossover repeat. The span of a Z-repeat in vitro is estimated by Atkinson et al. to be 12 nm or less; much less than half the normal vertebrate muscle actin crossover length of 36 nm. Different actin-binding proteins can change this length; it is reduced markedly by cofilin binding, or can increase to 38.5 nm in the abnormally large nemaline myopathy Z-band. Here, we tested whether in normal vertebrate Z-bands there is a marked reduction in crossover repeat so that it matches twice the apparent Z-repeat length of 12 nm. We found that the measured periodicities in wide Z-bands in slow and cardiac muscles are all very similar, about 39 nm, just like the nemaline myopathy Z-bands. Hence, the 39 nm periodicity is an important conserved feature of Z-bands and either cannot be explained by titin Z-repeats as previously suggested or may correlate with two Z-repeats.
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Affiliation(s)
- Pradeep K Luther
- Biological Structure and Function Section, Biomedical Sciences Division, Faculty of Medicine, Imperial College, Exhibition Road, London SW7 2AZ, UK.
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28
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The Chemistry of Movement. Biochemistry 2001. [DOI: 10.1016/b978-012492543-4/50022-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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