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Maksudov F, Jones LK, Barsegov V. Statistical Learning from Single-Molecule Experiments: Support Vector Machines and Expectation-Maximization Approaches to Understanding Protein Unfolding Data. J Phys Chem B 2021; 125:5794-5808. [PMID: 34075752 DOI: 10.1021/acs.jpcb.1c02334] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Single-molecule force spectroscopy has become a powerful tool for the exploration of dynamic processes that involve proteins; yet, meaningful interpretation of the experimental data remains challenging. Owing to low signal-to-noise ratio, experimental force-extension spectra contain force signals due to nonspecific interactions, tip or substrate detachment, and protein desorption. Unravelling of complex protein structures results in the unfolding transitions of different types. Here, we test the performance of Support Vector Machines (SVM) and Expectation Maximization (EM) approaches in statistical learning from dynamic force experiments. When the output from molecular modeling in silico (or other studies) is used as a training set, SVM and EM can be applied to understand the unfolding force data. The maximal margin or maximum likelihood classifier can be used to separate experimental test observations into the unfolding transitions of different types, and EM optimization can then be utilized to resolve the statistics of unfolding forces: weights, average forces, and standard deviations. We designed an EM-based approach, which can be directly applied to the experimental data without data classification and division into training and test observations. This approach performs well even when the sample size is small and when the unfolding transitions are characterized by overlapping force ranges.
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Cankaya AO, Pamuk U, Yucesoy CA. The effects of an activation-dependent increase in titin stiffness on whole muscle properties using finite element modeling. J Biomech 2020; 116:110197. [PMID: 33412436 DOI: 10.1016/j.jbiomech.2020.110197] [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: 04/11/2020] [Revised: 11/28/2020] [Accepted: 12/11/2020] [Indexed: 12/31/2022]
Abstract
Active state titin's effects have been studied predominantly in sarcomere or muscle fiber segment level and an understanding of its functional effects in the context of a whole muscle, and the mechanism of those is lacking. By representing experimentally observed calcium induced stiffening and actin-titin interaction induced reduced free spring length effects of active state titin in our linked fiber-matrix mesh finite element model, our aim was to study the mechanism of effects and particularly to determine the functionally more effective active state titin model. Isolated EDL muscle of the rat was modeled and three cases were studied: passive state titin (no change in titin constitutive equation in the active state), active state titin-I (constitutive equation involves a higher stiffness in the active state) and active state titin-II (constitutive equation also involves a strain shift coefficient accounting for titin's reduced free spring length). Isometric muscle lengthening was imposed (initial to long length, lm = 28.7 mm to 32.7 mm). Compared to passive state titin, (i) active state titin-I and II elevates muscle total (lm = 32.7 mm: 14% and 29%, respectively) and active (lm = 32.7 mm: 37.5% and 77.4%, respectively) forces, (ii) active state titin-II also shifts muscle's optimum length to a longer length (lm = 29.6 mm), (iii) active state titin-I and II limits sarcomere shortening (lm = 32.7 mm: up to 10% and 20%, respectively). Such shorter sarcomere effect characterizes active state titin's mechanism of effects. These effects become more pronounced and functionally more effective if not only calcium induced stiffening but also a reduced free spring length of titin is accounted for.
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Affiliation(s)
- Alican O Cankaya
- Institute of Biomedical Engineering, Boğaziçi University, Istanbul, Turkey
| | - Uluç Pamuk
- Institute of Biomedical Engineering, Boğaziçi University, Istanbul, Turkey
| | - Can A Yucesoy
- Institute of Biomedical Engineering, Boğaziçi University, Istanbul, Turkey.
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3
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Tomalka A, Röhrle O, Han JC, Pham T, Taberner AJ, Siebert T. Extensive eccentric contractions in intact cardiac trabeculae: revealing compelling differences in contractile behaviour compared to skeletal muscles. Proc Biol Sci 2019; 286:20190719. [PMID: 31138072 DOI: 10.1098/rspb.2019.0719] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Force enhancement (FE) is a phenomenon that is present in skeletal muscle. It is characterized by progressive forces upon active stretching-distinguished by a linear rise in force-and enhanced isometric force following stretching (residual FE (RFE)). In skeletal muscle, non-cross-bridge (XB) structures may account for this behaviour. So far, it is unknown whether differences between non-XB structures within the heart and skeletal muscle result in deviating contractile behaviour during and after eccentric contractions. Thus, we investigated the force response of intact cardiac trabeculae during and after isokinetic eccentric muscle contractions (10% of maximum shortening velocity) with extensive magnitudes of stretch (25% of optimum muscle length). The different contributions of XB and non-XB structures to the total muscle force were revealed by using an actomyosin inhibitor. For cardiac trabeculae, we found that the force-length dynamics during long stretch were similar to the total isometric force-length relation. This indicates that no (R)FE is present in cardiac muscle while stretching the muscle from 0.75 to 1.0 optimum muscle length. This finding is in contrast with the results obtained for skeletal muscle, in which (R)FE is present. Our data support the hypothesis that titin stiffness does not increase with activation in cardiac muscle.
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Affiliation(s)
- André Tomalka
- 1 Department of Motion and Exercise Science, University of Stuttgart , Stuttgart , Germany
| | - Oliver Röhrle
- 2 Institute of Applied Mechanics (Civil Engineering), University of Stuttgart , Stuttgart , Germany.,3 Cluster of Excellence for Simulation Technology (SimTech) , Stuttgart , Germany
| | - June-Chiew Han
- 4 Auckland Bioengineering Institute, The University of Auckland , Auckland , New Zealand
| | - Toan Pham
- 5 Department of Physiology, The University of Auckland , Auckland , New Zealand
| | - Andrew J Taberner
- 4 Auckland Bioengineering Institute, The University of Auckland , Auckland , New Zealand.,6 Department of Engineering Science, The University of Auckland , Auckland , New Zealand
| | - Tobias Siebert
- 1 Department of Motion and Exercise Science, University of Stuttgart , Stuttgart , Germany
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4
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Yakupova EI, Vikhlyantsev IM, Lobanov MY, Galzitskaya OV, Bobylev AG. Amyloid Properties of Titin. BIOCHEMISTRY (MOSCOW) 2018. [PMID: 29523065 DOI: 10.1134/s0006297917130077] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
This review considers data on structural and functional features of titin, on the role of this protein in determination of mechanical properties of sarcomeres, and on specific features of regulation of the stiffness and elasticity of its molecules, amyloid aggregation of this protein in vitro, and possibilities of formation of intramolecular amyloid structure in vivo. Molecular mechanisms are described of protection of titin against aggregation in muscle cells. Based on the data analysis, it is supposed that titin and the formed by it elastic filaments have features of amyloid.
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Affiliation(s)
- E I Yakupova
- Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia.
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5
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DuVall MM, Jinha A, Schappacher-Tilp G, Leonard TR, Herzog W. Differences in titin segmental elongation between passive and active stretch in skeletal muscle. ACTA ACUST UNITED AC 2017; 220:4418-4425. [PMID: 28970245 DOI: 10.1242/jeb.160762] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 09/26/2017] [Indexed: 12/25/2022]
Abstract
Since the 1950s, muscle contraction has been explained using a two-filament system in which actin and myosin exclusively dictate active force in muscle sarcomeres. Decades later, a third filament called titin was discovered. This titin filament has recently been identified as an important regulator of active force, but has yet to be incorporated into contemporary theories of muscle contraction. When sarcomeres are actively stretched, a substantial and rapid increase in force occurs, which has been suggested to arise in part from titin-actin binding that is absent in passively stretched sarcomeres. However, there is currently no direct evidence for such binding within muscle sarcomeres. Therefore, we aimed to determine whether titin binds to actin in actively but not in passively stretched sarcomeres by observing length changes of proximal and distal titin segments in the presence and absence of calcium. We labeled I-band titin with fluorescent F146 antibody in rabbit psoas myofibrils and tracked segmental elongations during passive (no calcium) and active (high calcium) stretch. Without calcium, proximal and distal segments of titin elongated as expected based on their free spring properties. In contrast, active stretch differed statistically from passive stretch, demonstrating that calcium activation increases titin segment stiffness, but not in an actin-dependent manner. The consistent elongation of the proximal segment was contrary to what was expected if titin's proximal segment was attached to actin. This rapid calcium-dependent change in titin stiffness likely contributes to active muscle force regulation in addition to actin and myosin.
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Affiliation(s)
- Michael M DuVall
- Human Performance Lab., University of Calgary, Calgary, AB, Canada T2N 1N4 .,Center for Bioengineering Innovation, Northern Arizona University, Flagstaff, AZ 86011, USA
| | - Azim Jinha
- Human Performance Lab., University of Calgary, Calgary, AB, Canada T2N 1N4
| | - Gudrun Schappacher-Tilp
- Department of Mathematics and Scientific Computing, Karl-Franzens-Universitat Graz, 8010 Graz, Austria
| | - Timothy R Leonard
- Human Performance Lab., University of Calgary, Calgary, AB, Canada T2N 1N4
| | - Walter Herzog
- Human Performance Lab., University of Calgary, Calgary, AB, Canada T2N 1N4
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Patel S, Rauf A, Khan H, Meher BR, Hassan SSU. A holistic review on the autoimmune disease vitiligo with emphasis on the causal factors. Biomed Pharmacother 2017; 92:501-508. [PMID: 28575807 DOI: 10.1016/j.biopha.2017.05.095] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Revised: 05/12/2017] [Accepted: 05/22/2017] [Indexed: 12/25/2022] Open
Abstract
Vitiligo is an idiopathic systemic autoimmune disease affecting skin, hair and oral mucosa. This genetic yet acquired disease characterized by melanin loss is a cause of morbidity across all races. Though thyroid disturbance has been recognized as a key trigger of this pathology, an array of other factors plays critical role in its manifestation. Multiple hormones (corticotropin-releasing hormone, adrenocorticotropic hormone, α-melanocyte-stimulating hormone, melatonin, calcitriol, testosterone, estrogen), genes (Human leukocyte antigen (HLA), Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), Forkhead box D3 (FOXD3), Cluster of differentiation 117 (CD117), Estrogen receptor (ESR) 1, Cyclooxygenase-2 (COX2), Vitiligo-associated protein 1 (VIT1)), and lifestyle choices (stress, diet, cosmetic products, and medications) have been suspected as drivers of this disorder. The pathological mechanisms have been understood in recent times, with the aid of genomic studies; however a universally-effective therapy is yet to be achieved. This review discusses these under-investigated facets of vitiligo onset and progression; hence, it is expected to enrich vitiligo research.
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Affiliation(s)
- Seema Patel
- Bioinformatics and Medical Informatics Research Center, San Diego State University, 5500 Campanile Dr, San Diego, 92182, USA.
| | - Abdur Rauf
- Department of Chemistry, University of Swabi, Anbar, 23561, K.P.K, Pakistan.
| | - Haroon Khan
- Department of Pharmacy, Abdul Wali Khan University, Mardan, 23200, Pakistan
| | - Biswa Ranjan Meher
- Centre for Life Sciences, Central University of Jharkhand, Brambe, Ranchi, 835205, Jharkhand, India
| | - Syed Shams Ul Hassan
- Department of Marine Chemistry and Natural Products, Ocean College, Zhejiang University, Hangzhou, 310058, PR China
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7
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Does weightlifting increase residual force enhancement? J Biomech 2016; 49:2047-2052. [DOI: 10.1016/j.jbiomech.2016.05.017] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Revised: 05/09/2016] [Accepted: 05/15/2016] [Indexed: 10/21/2022]
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8
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Akhlaq A, Mehmood MH, Rehman A, Ashraf Z, Syed S, Bawany SA, Gilani AH, Ilyas M, Siddiqui BS. The Prokinetic, Laxative, and Antidiarrheal Effects of Morus nigra: Possible Muscarinic, Ca(2+) Channel Blocking, and Antimuscarinic Mechanisms. Phytother Res 2016; 30:1362-76. [PMID: 27230535 DOI: 10.1002/ptr.5641] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Revised: 04/15/2016] [Accepted: 04/19/2016] [Indexed: 01/14/2023]
Abstract
Morus nigra Linn. (black mulberry) is used in gastrointestinal ailments. This study demonstrates gut modulatory properties of M. nigra. The prokinetic, laxative, and antidiarrheal activities of M. nigra were assessed in mice, while isolated rabbit jejunum and guinea-pig ileum were used to explore insight into mechanism(s). At 30 and 70 mg/kg, the crude extract of M. nigra (Mn.Cr) exhibited atropine-sensitive prokinetic and laxative effects, similar to carbachol (CCh). While at higher doses (100, 300, and 500 mg/kg), Mn.Cr offered protection against castor oil-induced diarrhea. In rabbit jejunum, Mn.Cr and its chloroform fraction inhibited CCh-induced contractions more potently compared with high K(+) (80 mm). Conversely, petroleum fraction was more potent against high-K(+) -induced contractions. At 0.01 mg/mL, Mn.Cr caused a parallel shift in acetylcholine concentration-response curves (CRCs) followed by a non-parallel shift at 0.03 mg/mL, similar to dicyclomine. At further tested concentrations, Mn.Cr (0.1 and 0.3 mg/mL) and petroleum fraction suppressed Ca(2+) CRCs, similar to verapamil. In guinea-pig ileum, Mn.Cr, its aqueous and ethyl acetate fractions exhibited atropine-sensitive gut stimulant activity along with additional uncharacterized excitatory response in the aqueous fraction only. These results suggest that black mulberry possesses prokinetic, laxative, and antidiarrheal effects, putatively mediated through cholinomimetic, antimuscarinic, and Ca(2+) antagonist mechanisms, respectively. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Anam Akhlaq
- Natural Products Research Division, Department of Biological and Biomedical Sciences, Aga Khan University, PO Box 3500, Stadium Road, Karachi, 74800, Sindh, Pakistan
| | - Malik Hassan Mehmood
- Natural Products Research Division, Department of Biological and Biomedical Sciences, Aga Khan University, PO Box 3500, Stadium Road, Karachi, 74800, Sindh, Pakistan
| | - Abdul Rehman
- Natural Products Research Division, Department of Biological and Biomedical Sciences, Aga Khan University, PO Box 3500, Stadium Road, Karachi, 74800, Sindh, Pakistan.,Internal Medicine Section, Department of Medicine, Hamad Medical Corporation, PO Box 3050, Doha, Qatar
| | - Zohaib Ashraf
- Natural Products Research Division, Department of Biological and Biomedical Sciences, Aga Khan University, PO Box 3500, Stadium Road, Karachi, 74800, Sindh, Pakistan
| | - Sadia Syed
- Natural Products Research Division, Department of Biological and Biomedical Sciences, Aga Khan University, PO Box 3500, Stadium Road, Karachi, 74800, Sindh, Pakistan
| | - Samira Ahmed Bawany
- Natural Products Research Division, Department of Biological and Biomedical Sciences, Aga Khan University, PO Box 3500, Stadium Road, Karachi, 74800, Sindh, Pakistan
| | - Anwarul-Hassan Gilani
- Natural Products Research Division, Department of Biological and Biomedical Sciences, Aga Khan University, PO Box 3500, Stadium Road, Karachi, 74800, Sindh, Pakistan.,Pakistan Council for Science and Technology, G-5/2, Islamabad, Pakistan
| | - Maimoona Ilyas
- H.E.J. Research Institute of Chemistry, International Centre for Chemical and Biological Sciences, University of Karachi, Karachi, Sindh, 75270, Pakistan
| | - Bina Shaheen Siddiqui
- H.E.J. Research Institute of Chemistry, International Centre for Chemical and Biological Sciences, University of Karachi, Karachi, Sindh, 75270, Pakistan
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9
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Heidlauf T, Klotz T, Rode C, Altan E, Bleiler C, Siebert T, Röhrle O. A multi-scale continuum model of skeletal muscle mechanics predicting force enhancement based on actin-titin interaction. Biomech Model Mechanobiol 2016; 15:1423-1437. [PMID: 26935301 DOI: 10.1007/s10237-016-0772-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Accepted: 02/17/2016] [Indexed: 10/22/2022]
Abstract
Although recent research emphasises the possible role of titin in skeletal muscle force enhancement, this property is commonly ignored in current computational models. This work presents the first biophysically based continuum-mechanical model of skeletal muscle that considers, in addition to actin-myosin interactions, force enhancement based on actin-titin interactions. During activation, titin attaches to actin filaments, which results in a significant reduction in titin's free molecular spring length and therefore results in increased titin forces during a subsequent stretch. The mechanical behaviour of titin is included on the microscopic half-sarcomere level of a multi-scale chemo-electro-mechanical muscle model, which is based on the classic sliding-filament and cross-bridge theories. In addition to titin stress contributions in the muscle fibre direction, the continuum-mechanical constitutive relation accounts for geometrically motivated, titin-induced stresses acting in the muscle's cross-fibre directions. Representative simulations of active stretches under maximal and submaximal activation levels predict realistic magnitudes of force enhancement in fibre direction. For example, stretching the model by 20 % from optimal length increased the isometric force at the target length by about 30 %. Predicted titin-induced stresses in the muscle's cross-fibre directions are rather insignificant. Including the presented development in future continuum-mechanical models of muscle function in dynamic situations will lead to more accurate model predictions during and after lengthening contractions.
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Affiliation(s)
- Thomas Heidlauf
- Institute of Applied Mechanics (CE), Pfaffenwaldring 7, 70569, Stuttgart, Germany.
| | - Thomas Klotz
- Institute of Applied Mechanics (CE), Pfaffenwaldring 7, 70569, Stuttgart, Germany
| | - Christian Rode
- Institute of Motion Science, Friedrich-Schiller-University, Seidelstr. 20, 07749, Jena, Germany
| | - Ekin Altan
- Institute of Applied Mechanics (CE), Pfaffenwaldring 7, 70569, Stuttgart, Germany
| | - Christian Bleiler
- Institute of Applied Mechanics (CE), Pfaffenwaldring 7, 70569, Stuttgart, Germany
| | - Tobias Siebert
- Department of Sport and Motion Science, University of Stuttgart, Allmandring 28, 70569, Stuttgart, Germany
| | - Oliver Röhrle
- Institute of Applied Mechanics (CE), Pfaffenwaldring 7, 70569, Stuttgart, Germany
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10
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Vikhlyantsev IM, Podlubnaya ZA. New titin (connectin) isoforms and their functional role in striated muscles of mammals: facts and suppositions. BIOCHEMISTRY (MOSCOW) 2013; 77:1515-35. [PMID: 23379526 DOI: 10.1134/s0006297912130093] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
This review summarizes results of our studies on titin isoform composition in vertebrate striated muscles under normal conditions, during hibernation, real and simulated microgravity, and under pathological conditions (stiff-person syndrome, post-apoplectic spasticity, dilated cardiomyopathy, cardiac hypertrophy). Experimental evidence for the existence in mammalian striated muscles of higher molecular weight isoforms of titin (NT-isoforms) in addition to the known N2A-, N2BA-, and N2B-titin isoforms was obtained. Comparative studies of changes in titin isoform composition and structure-functional properties of human and animal striated muscles during adaptive and pathological processes led to a conclusion about the key role of NT-isoforms of titin in maintenance of sarcomere structure and contractile function of these muscles.
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Affiliation(s)
- I M Vikhlyantsev
- Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia.
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11
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Abstract
Myofascial pain syndrome (MPS) is described as the sensory, motor, and autonomic symptoms caused by myofascial trigger points (TrPs). Knowing the potential causes of TrPs is important to prevent their development and recurrence, but also to inactivate and eliminate existing TrPs. There is general agreement that muscle overuse or direct trauma to the muscle can lead to the development of TrPs. Muscle overload is hypothesized to be the result of sustained or repetitive low-level muscle contractions, eccentric muscle contractions, and maximal or submaximal concentric muscle contractions. TrPs may develop during occupational, recreational, or sports activities when muscle use exceeds muscle capacity and normal recovery is disturbed.
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Affiliation(s)
- Carel Bron
- Scientific Institute for Quality of Healthcare, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
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12
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Rode C, Siebert T, Blickhan R. Titin-induced force enhancement and force depression: a 'sticky-spring' mechanism in muscle contractions? J Theor Biol 2009; 259:350-60. [PMID: 19306884 DOI: 10.1016/j.jtbi.2009.03.015] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2008] [Revised: 03/02/2009] [Accepted: 03/04/2009] [Indexed: 10/21/2022]
Abstract
The sliding filament and crossbridge theories do not suffice to explain a number of muscle experiments. For example, from the entire muscle to myofibrils, predictions of these theories were shown to underestimate the force output during and after active tissue stretch. The converse applies to active tissue shortening. In addition to the crossbridge cycle, we propose that another molecular mechanism is effective in sarcomere force generation. We suggest that, when due to activation, myosin binding sites are available on actin, the giant protein titin's PEVK region attaches itself to the actin filament at those sites. As a result, the molecular spring length is dramatically reduced. This leads to increased passive force when the sarcomere is stretched and to decreased or even negative passive force when the sarcomere shortens. Moreover, during shortening, the proposed mechanism interferes with active-force production by inhibiting crossbridges. Incorporation of a simple 'sticky-spring' mechanism model into a Hill-type model of sarcomere dynamics offers explanations for several force-enhancement and force-depression effects. For example, the increase of the sarcomere force compared to the force predicted solely by the sliding filament and crossbridge theories depends on the stretch amplitude and on the working range. The same applies to the decrease of sarcomere force during and after shortening. Using only literature data for its parameterization, the model predicts forces similar to experimental results.
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Affiliation(s)
- Christian Rode
- Institute of Motion Science, Friedrich Schiller University, Seidelstr. 20, 07749 Jena, Germany.
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13
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Ponomareva EV, Kravtsova VV, Kachaeva EV, Altaeva EG, Vikhlyantsev IM, Podlubnaya ZA, Krivoi II, Shenkman BS. Contractile properties of the isolated rat soleus muscle and its single skinned soleus fibers at the early stage of gravitational unloading: Facts and hypotheses. Biophysics (Nagoya-shi) 2008. [DOI: 10.1134/s0006350908060274] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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14
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Bullimore SR, MacIntosh BR, Herzog W. Is a parallel elastic element responsible for the enhancement of steady-state muscle force following active stretch? J Exp Biol 2008; 211:3001-8. [DOI: 10.1242/jeb.021204] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
For over 50 years, it has been recognised that muscles from many different species of animals are able to generate a higher steady-state isometric force after active stretch than during a purely isometric contraction at the same length. This is known as `residual force enhancement' (rFE). The mechanism underlying this phenomenon remains controversial. One proposal is that an elastic element parallel to the cross-bridges becomes stiffer, or is engaged,when the muscle is activated and generates force when stretched. If this is indeed the sole mechanism, then rFE should be eliminated by subsequently shortening the muscle by a distance equal to or greater than the initial stretch. We tested this hypothesis using six intact single fibres from frog lumbrical muscle. The fibres were activated and stretched to generate rFE and then rapidly shortened by between 25% and 700% of the initial stretch distance. In contrast to previous reports, we found that rapid shortening induced a depression of subsequent isometric force. We used two methods to account for this force depression when calculating rFE, thereby obtaining upper and lower bounds for the true rFE. With both methods of calculation, rFE was significantly greater than zero when shortening distance was equal to stretch distance (P=0.0004 and P=0.03, respectively). Therefore, our hypothesis was not supported. We conclude that rFE is unlikely to be generated solely by a parallel elastic element.
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Affiliation(s)
- S. R. Bullimore
- Human Performance Lab, Faculty of Kinesiology, University of Calgary,2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4
| | - B. R. MacIntosh
- Human Performance Lab, Faculty of Kinesiology, University of Calgary,2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4
| | - W. Herzog
- Human Performance Lab, Faculty of Kinesiology, University of Calgary,2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4
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15
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Vikhlyantsev IM, Podlubnaya ZA. Structure and functions of titin, a giant protein of skeletal and cardiac muscle: Evidence and suppositions. Biophysics (Nagoya-shi) 2007. [DOI: 10.1134/s0006350907060061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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16
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Shelud'ko NS, Matusovsky OS, Permyakova TV, Matusovskaya GG. "Twitchin-actin linkage hypothesis" for the catch mechanism in molluscan muscles: evidence that twitchin interacts with myosin, myorod, and paramyosin core and affects properties of actomyosin. Arch Biochem Biophys 2007; 466:125-35. [PMID: 17720132 DOI: 10.1016/j.abb.2007.07.014] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2007] [Revised: 07/11/2007] [Accepted: 07/13/2007] [Indexed: 10/23/2022]
Abstract
"Twitchin-actin linkage hypothesis" for the catch mechanism in molluscan smooth muscles postulates in vivo existence of twitchin links between thin and thick filaments that arise in a phosphorylation-dependent manner [N.S. Shelud'ko, G.G. Matusovskaya, T.V. Permyakova, O.S. Matusovsky, Arch. Biochem. Biophys. 432 (2004) 269-277]. In this paper, we proposed a scheme for a possible catch mechanism involving twitchin links and regulated thin filaments. The experimental evidence in support of the scheme is provided. It was found that twitchin can interact not only with mussel myosin and rabbit F-actin but also with the paramyosin core of thick filaments, myorod, mussel thin filaments, "natural" F-actin from mussel, and skeletal myosin from rabbit. No difference was revealed in binding of twitchin with mussel and rabbit myosin. The capability of twitchin to interact with all thick filament proteins suggests that putative twitchin links can be attached to any site of thick filaments. Addition of twitchin to a mixture of actin and paramyosin filaments, or to a mixture of Ca(2+)-regulated actin and myosin filaments under relaxing conditions caused in both cases similar changes in the optical properties of suspensions, indicating an interaction and aggregation of the filaments. The interaction of actin and myosin filaments in the presence of twitchin under relaxing conditions was not accompanied by an appreciable increase in the MgATPase activity. We suggest that in both cases aggregation of filaments was caused by formation of twitchin links between the filaments. We also demonstrate that native thin filaments from the catch muscle of the mussel Crenomytilus grayanus are Ca(2+)-regulated. Twitchin inhibits the ability of thin filaments to activate myosin MgATPase in the presence of Ca(2+). We suggest that twitchin inhibition of the actin-myosin interaction is due to twitchin-induced switching of the thin filaments to the inactive state.
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Affiliation(s)
- Nikolay S Shelud'ko
- Department of Cell Biophysics, Institute of Marine Biology, Far East Branch of the Russian Academy of Sciences, Vladivostok 690041, Russia.
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Bianco P, Nagy A, Kengyel A, Szatmári D, Mártonfalvi Z, Huber T, Kellermayer MSZ. Interaction forces between F-actin and titin PEVK domain measured with optical tweezers. Biophys J 2007; 93:2102-9. [PMID: 17513381 PMCID: PMC1959548 DOI: 10.1529/biophysj.107.106153] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Titin is a giant protein that determines the elasticity of striated muscle and is thought to play important roles in numerous regulatory processes. Previous studies have shown that titin's PEVK domain interacts with F-actin, thereby creating viscous forces of unknown magnitude that may modulate muscle contraction. Here we measured, with optical tweezers, the forces necessary to dissociate F-actin from individual molecules of recombinant PEVK fragments rich either in polyE or PPAK motifs. Rupture forces at a stretch rate of 250 nm/s displayed a wide, nonnormal distribution with a peak at approximately 8 pN in the case of both fragments. Dynamic force spectroscopy experiments revealed low spontaneous off-rates that were increased even by low forces. The loading-rate dependence of rupture force was biphasic for polyE in contrast with the monophasic response observed for PPAK. Analysis of the molecular lengths at which rupture occurred indicated that there are numerous actin-binding regions along the PEVK fragments' contour, suggesting that the PEVK domain is a promiscuous actin-binding partner. The complexity of PEVK-actin interaction points to an adaptable viscoelastic mechanism that safeguards sarcomeric structural integrity in the relaxed state and modulates thixotropic behavior during contraction.
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Affiliation(s)
- Pasquale Bianco
- Department of Biophysics, University of Pécs, Faculty of Medicine, Szigeti út 12, Pécs H-7624, Hungary
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Raynaud F, Fernandez E, Coulis G, Aubry L, Vignon X, Bleimling N, Gautel M, Benyamin Y, Ouali A. Calpain 1-titin interactions concentrate calpain 1 in the Z-band edges and in the N2-line region within the skeletal myofibril. FEBS J 2005; 272:2578-90. [PMID: 15885106 DOI: 10.1111/j.1742-4658.2005.04683.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Calpain 1, a ubiquitous calcium-dependent intracellular protease, was recently found in a tight association with myofibrils in skeletal muscle tissue [Delgado EF, Geesink GH, Marchello JA, Goll DE & Koohmaraie M (2001) J Anim Sci79, 2097-2107). Our immunofluorescence and immunoelectron microscopy investigations restrain the protease location at the periphery of the Z-band and at the midpoint of the I-band. Furthermore, calpain 1 is found to localize in myofibril fractures, described as proteolysis sites, in postmortem bovine skeletal red muscles, near the calcium deposits located at the N1 and N2 level. This in situ localization of calpain 1 is substantiated by binding assays with two titin regions covering the I-band region: a native fragment of 150 kDa (identified by mass spectrometry) that includes the N-terminal Z8-I5 region and the N1-line region of titin, and an 800 kDa fragment external to the N1 line that bears the PEVK/N2 region. These two titin fragments are shown to tightly bind calpain 1 in the presence of CaCl(2) and E64, a calpain inhibitor. In the absence of E64, they are cleaved by calpain 1. We conclude that titin affords binding sites to calpain 1, which concentrates the protease in the regions restrained by the Z-band edge and the N1-line as well as at the N2-line level, two sarcomeric regions where early postmortem proteolysis is detected.
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Affiliation(s)
- Fabrice Raynaud
- Cell Motility Laboratory, EPHE, UMR-5539, UM2, Montpellier, France
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