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Creso JG, Campbell SG. Potential impacts of the cardiac troponin I mobile domain on myofilament activation and relaxation. J Mol Cell Cardiol 2021; 155:50-57. [PMID: 33647310 DOI: 10.1016/j.yjmcc.2021.02.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 01/13/2021] [Accepted: 02/22/2021] [Indexed: 10/22/2022]
Abstract
The cardiac thin filament is regulated in a Ca2+-dependent manner through conformational changes of troponin and tropomyosin (Tm). It has been generally understood that under conditions of low Ca2+ the inhibitory peptide domain (IP) of troponin I (TnI) binds to actin and holds Tm over the myosin binding sites on actin to prevent crossbridge formation. More recently, evidence that the C-terminal mobile domain (MD) of TnI also binds actin has made for a more complex scenario. This study uses a computational model to investigate the consequences of assuming that TnI regulates Tm movement via two actin-binding domains rather than one. First, a 16-state model of the cardiac thin filament regulatory unit was created with TnI-IP as the sole regulatory domain. Expansion of this to include TnI-MD formed a 24-state model. Comparison of these models showed that assumption of a second actin-binding site allows the individual domains to have a lower affinity for actin than would be required for IP acting alone. Indeed, setting actin affinities of the IP and MD to 25% of that assumed for the IP in the single-site model was sufficient to achieve precisely the same degree of Ca2+ regulation. We also tested the 24-state model's ability to represent steady-state experimental data in the case of disruption of either the IP or MD. We were able to capture qualitative changes in several properties that matched what was seen in the experimental data. Lastly, simulations were run to examine the effect of disruption of the IP or MD on twitch dynamics. Our results suggest that both domains are required to keep diastolic cross-bridge activity to a minimum and accelerate myofilament relaxation. Overall, our analyses support a paradigm in which two domains of TnI bind with moderate affinity to actin, working in tandem to complete Ca2+-dependent regulation of the thin filament.
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Affiliation(s)
- Jenette G Creso
- Department of Biomedical Engineering, Yale University, 55 Prospect St, New Haven, CT 06511, USA.
| | - Stuart G Campbell
- Department of Biomedical Engineering, Yale University, 55 Prospect St, New Haven, CT 06511, USA; Department of Cellular and Molecular Physiology, Yale School of Medicine, 333 Cedar St, New Haven, CT 06510, USA.
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Feng HZ, Jin JP. High efficiency preparation of skinned mouse cardiac muscle strips from cryosections for contractility studies. Exp Physiol 2020; 105:1869-1881. [PMID: 32857888 DOI: 10.1113/ep088521] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2020] [Accepted: 08/26/2020] [Indexed: 12/18/2022]
Abstract
NEW FINDINGS What is the central question of this study? Can frozen cardiac papillary muscles and cryosectioning be used to reliably obtain uniform cardiac muscle strips with high yields? What is the main finding and its importance? A new method was developed using frozen cardiac papillary muscles and cryosectioning to reliably obtain uniform cardiac muscle strips with high yields. Experimental results demonstrate that this new methodology significantly increases the efficiency and application of quantitative biomechanical studies using skinned muscle fibres with an additional advantage of no need for transferring live animals. ABSTRACT Skinned cardiac muscle preparations are widely used to study contractile function of myofilament proteins and pathophysiological changes. The current methods applied in these biomechanical studies include detergent permeabilization of freshly isolated papillary muscle, ventricular trabeculae, surgically dissected ventricular muscle strips, mechanically blended cardiac muscle bundles or myocytes, and enzymatically isolated single cardiomyocytes. To facilitate and expand the skinned cardiac muscle approach, we have developed an efficient and readily practical method for mechanical studies of skinned mouse cardiac papillary muscle strips prepared from cryosections. Longitudinal papillary muscle strips of 120-150 µm width cut from 35-70 µm-thick cryosections are mounted to a force transducer and chemically skinned for the studies of force-pCa and sarcomere length-tension relationship and rate of tension redevelopment. In addition to more effective skinning and perfusion than with whole papillary muscle and much higher yield of useful preparations than that from trabeculae, this new methodology has two more major advantages. One is to allow for the use of frozen cardiac muscle in storage to maximize the value of muscle samples, facilitating resource sharing among research institutions without the need of transferring live animals or fresh biopsies. The other is that the integrity of the muscle strips is well preserved during the preparation and mechanical studies, allowing coupled characterization of myofilament proteins. The combined power of biomechanics and protein biochemistry can provide novel insights into integrative physiological and pathophysiological mechanisms of cardiac muscle contraction while the high yield of high-quality muscle strips also provides an efficient platform for development of therapeutic reagents.
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Affiliation(s)
- Han-Zhong Feng
- Physiology Department, School of Medicine, Wayne State University, Detroit, MI, USA
| | - J-P Jin
- Physiology Department, School of Medicine, Wayne State University, Detroit, MI, USA
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A cardiac troponin I photoelectrochemical immunosensor: nitrogen-doped carbon quantum dots–bismuth oxyiodide–flower-like SnO2. Mikrochim Acta 2020; 187:332. [DOI: 10.1007/s00604-020-04302-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Accepted: 04/27/2020] [Indexed: 12/15/2022]
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Chen X, Zeng D, Zhu W, Peng M, Yang C, Li Q, Liu Q, Yang Q, Wang H, Li M, Lin Y, Zhao Y, Chen X. The Penaeus stylirostris densovirus capsid interacts with Litopenaeus vannamei troponin I. FISH & SHELLFISH IMMUNOLOGY 2019; 86:101-106. [PMID: 30447431 DOI: 10.1016/j.fsi.2018.11.034] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Revised: 10/15/2018] [Accepted: 11/14/2018] [Indexed: 06/09/2023]
Abstract
The Penaeus stylirostris densovirus (PstDNV) (also known as infectious hypodermal and hematopoietic necrosis virus, IHHNV), a very small DNA virus, is a major shrimp pathogen. The PstDNV genome encodes only two nonstructural proteins and one capsid protein. This virus is thus an ideal, simple model for the investigation of virus-host interactions. To explore the role of the PstDNV capsid in viral infections, a yeast two-hybrid (Y2H) cDNA library was constructed based on Pacific white shrimp, Litopenaeus vannamei mRNA. The Y2H library was then screened, using the PstDNV capsid protein as bait. We identified a host protein that interacted strongly with the PstDNV capsid as L. vannamei troponin I (LvTnI). An in vitro co-immunoprecipitation experiment further supported this interaction. In addition, an in vivo neutralization experiment showed that the vaccination with anti-LvTnI significantly reduced PstDNV copies in PstDNV-challenged shrimp, indicating that the interaction between the PstDNV capsid and cellular LvTnI is essential for PstDNV infection. This result has important implications for our understanding of the mechanisms by which PstDNV infects shrimp.
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Affiliation(s)
- Xiuli Chen
- Guangxi Key Laboratory of Aquatic Genetic Breeding and Healthy Aquaculture, Guangxi Academy of Fisheries Sciences, Nanning, China
| | - Digang Zeng
- Guangxi Key Laboratory of Aquatic Genetic Breeding and Healthy Aquaculture, Guangxi Academy of Fisheries Sciences, Nanning, China
| | - Weilin Zhu
- Guangxi Key Laboratory of Aquatic Genetic Breeding and Healthy Aquaculture, Guangxi Academy of Fisheries Sciences, Nanning, China
| | - Min Peng
- Guangxi Key Laboratory of Aquatic Genetic Breeding and Healthy Aquaculture, Guangxi Academy of Fisheries Sciences, Nanning, China
| | - Chunling Yang
- Guangxi Key Laboratory of Aquatic Genetic Breeding and Healthy Aquaculture, Guangxi Academy of Fisheries Sciences, Nanning, China
| | - Qiangyong Li
- Guangxi Key Laboratory of Aquatic Genetic Breeding and Healthy Aquaculture, Guangxi Academy of Fisheries Sciences, Nanning, China
| | - Qingyun Liu
- Guangxi Key Laboratory of Aquatic Genetic Breeding and Healthy Aquaculture, Guangxi Academy of Fisheries Sciences, Nanning, China
| | - Qiong Yang
- Guangxi Key Laboratory of Aquatic Genetic Breeding and Healthy Aquaculture, Guangxi Academy of Fisheries Sciences, Nanning, China
| | - Hui Wang
- Guangxi Key Laboratory of Aquatic Genetic Breeding and Healthy Aquaculture, Guangxi Academy of Fisheries Sciences, Nanning, China
| | - Min Li
- Guangxi Key Laboratory of Aquatic Genetic Breeding and Healthy Aquaculture, Guangxi Academy of Fisheries Sciences, Nanning, China
| | - Yong Lin
- Guangxi Key Laboratory of Aquatic Genetic Breeding and Healthy Aquaculture, Guangxi Academy of Fisheries Sciences, Nanning, China
| | - Yongzhen Zhao
- Guangxi Key Laboratory of Aquatic Genetic Breeding and Healthy Aquaculture, Guangxi Academy of Fisheries Sciences, Nanning, China
| | - Xiaohan Chen
- Guangxi Key Laboratory of Aquatic Genetic Breeding and Healthy Aquaculture, Guangxi Academy of Fisheries Sciences, Nanning, China.
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Bohlooli Ghashghaee N, Li KL, Solaro RJ, Dong WJ. Role of the C-terminus mobile domain of cardiac troponin I in the regulation of thin filament activation in skinned papillary muscle strips. Arch Biochem Biophys 2018; 648:27-35. [PMID: 29704484 DOI: 10.1016/j.abb.2018.04.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 04/18/2018] [Accepted: 04/21/2018] [Indexed: 11/19/2022]
Abstract
The C-terminus mobile domain of cTnI (cTnI-MD) is a highly conserved region which stabilizes the actin-cTnI interaction during the diastole. Upon Ca2+-binding to cTnC, cTnI-MD participates in a regulatory switching that involves cTnI to switch from interacting with actin toward interacting with the Ca2+-regulatory domain of cTnC. Despite many studies targeting the cTnI-MD, the role of this region in the length-dependent activation of cardiac contractility is yet to be determined. The present study investigated the functional consequences of losing the entire cTnI-MD in cTnI(1-167) truncation mutant, as it was exchanged for endogenous cTnI in skinned rat papillary muscle fibers. The influence of cTnI-MD truncation on the extent of the N-domain of cTnC hydrophobic cleft opening and the steady-state force as a function of sarcomere length (SL), cross-bridge state, and [Ca2+] was assessed using the simultaneous in situ time-resolved FRET and force measurements at short (1.8 μm) and long (2.2 μm) SLs. Our results show the significant role of cTnI-MD in the length dependent thin filament activation and the coupling between thin and thick filament regulations affected by SL. Our results also suggest that cTnI-MD transmits the effects of SL change to the core of troponin complex.
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Affiliation(s)
- Nazanin Bohlooli Ghashghaee
- The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164, USA
| | - King-Lun Li
- The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164, USA
| | - R John Solaro
- The Department of Physiology and Biophysics, Center for Cardiovascular Research, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - Wen-Ji Dong
- The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164, USA; The Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA 99164, USA.
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