Troponin T and Ca2+Dependence of the Distance between Cys48 and Cys133 of Troponin I in the Ternary Troponin Complex and Reconstituted Thin Filaments†

AbstractBACKGROUNDThe measurement of cardiac isoforms of troponin I (cTnI) and troponin T (cTnT) is widely used for the diagnosis of acute myocardial infarction (AMI). However, there are conflicting data regarding what forms of cTnI and cTnT are present in the blood of AMI patients. We investigated cTnI and cTnT as components of troponin complexes in the blood of AMI patients.METHODSGel filtration techniques, sandwich fluoroimmunoassays, and Western blotting were used.RESULTSPlasma samples from patients with AMI contained the following troponin complexes: (a) a cTnI-cTnT-TnC complex (ITC) composed of full-size cTnT of 37 kDa or its 29-kDa fragment and full-size cTnI of 29 kDa or its 27-kDa fragments; (b) ITC with lower molecular weight (LMW-ITC) in which cTnT was truncated to the 14-kDa C-terminal fragments; and (c) a binary cTnI-cTnC complex composed of truncated cTnI of approximately 14 kDa. During the progression of the disease, the amount of ITC in AMI samples decreased, whereas the amounts of LMW-ITC and short 16- to 20-kDa cTnT central fragments increased. Almost all full-size cTnT and a 29-kDa cTnT fragment in AMI plasma samples were the components of ITC. No free full-size cTnT was found in AMI plasma samples. Only 16- to 27-kDa central fragments of cTnT were present in a free form in patient blood.CONCLUSIONSA ternary troponin complex exists in 2 forms in the blood of patients with AMI: full-size ITC and LMW-ITC. The binary cTnI-cTnC complex and free cTnT fragments are also present in patient blood.

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Cardiac Troponin Complex: Cardiac Troponin C (TNNC1), Cardiac Troponin I (TNNI3), and Cardiac Troponin T (TNNT2)

Encyclopedia of Signaling Molecules ◽

10.1007/978-1-4614-6438-9_101901-1 ◽

2016 ◽

pp. 1-10

Author(s):

Zabed Mahmud ◽

Peter M. Hwang

Keyword(s):

Cardiac Troponin ◽

Troponin I ◽

Troponin T ◽

Troponin C ◽

Cardiac Troponin I ◽

Cardiac Troponin T ◽

Cardiac Troponin C ◽

Troponin Complex

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Troponin Variants as Markers of Skeletal Muscle Health and Diseases

Frontiers in Physiology ◽

10.3389/fphys.2021.747214 ◽

2021 ◽

Vol 12 ◽

Author(s):

Monica Rasmussen ◽

Jian-Ping Jin

Keyword(s):

Skeletal Muscle ◽

Troponin I ◽

Striated Muscle ◽

Troponin T ◽

Muscle Quality ◽

Striated Muscles ◽

Thin Filaments ◽

Age Related ◽

Development And Aging ◽

Regulation Of Muscle Contraction

Ca2+-regulated contractility is a key determinant of the quality of muscles. The sarcomeric myofilament proteins are essential players in the contraction of striated muscles. The troponin complex in the actin thin filaments plays a central role in the Ca2+-regulation of muscle contraction and relaxation. Among the three subunits of troponin, the Ca2+-binding subunit troponin C (TnC) is a member of the calmodulin super family whereas troponin I (TnI, the inhibitory subunit) and troponin T (TnT, the tropomyosin-binding and thin filament anchoring subunit) are striated muscle-specific regulatory proteins. Muscle type-specific isoforms of troponin subunits are expressed in fast and slow twitch fibers and are regulated during development and aging, and in adaptation to exercise or disuse. TnT also evolved with various alternative splice forms as an added capacity of muscle functional diversity. Mutations of troponin subunits cause myopathies. Owing to their physiological and pathological importance, troponin variants can be used as specific markers to define muscle quality. In this focused review, we will explore the use of troponin variants as markers for the fiber contents, developmental and differentiation states, contractile functions, and physiological or pathophysiological adaptations of skeletal muscle. As protein structure defines function, profile of troponin variants illustrates how changes at the myofilament level confer functional qualities at the fiber level. Moreover, understanding of the role of troponin modifications and mutants in determining muscle contractility in age-related decline of muscle function and in myopathies informs an approach to improve human health.

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Cardiac Troponin Mutations and Restrictive Cardiomyopathy

Journal of Biomedicine and Biotechnology ◽

10.1155/2010/350706 ◽

2010 ◽

Vol 2010 ◽

pp. 1-9 ◽

Cited By ~ 30

Author(s):

Michelle S. Parvatiyar ◽

Jose Renato Pinto ◽

David Dweck ◽

James D. Potter

Keyword(s):

Cardiac Troponin ◽

Troponin I ◽

Diastolic Pressure ◽

Troponin T ◽

Restrictive Cardiomyopathy ◽

Clinical Findings ◽

Sarcomeric Proteins ◽

Functional Studies ◽

Skinned Muscle ◽

Troponin Complex

Mutations in sarcomeric proteins have recently been established as heritable causes of Restrictive Cardiomyopathy (RCM). RCM is clinically characterized as a defect in cardiac diastolic function, such as, impaired ventricular relaxation, reduced diastolic volume and increased end-diastolic pressure. To date, mutations have been identified in the cardiac genes for desmin,α-actin, troponin I and troponin T. Functional studies in skinned muscle fibers reconstituted with troponin mutants have established phenotypes consistent with the clinical findings which include an increase in myofilamentCa2+sensitivity and basal force. Moreover, when RCM mutants are incorporated into reconstituted myofilaments, the ability to inhibit the ATPase activity is reduced. A majority of the mutations cluster in specific regions of cardiac troponin and appear to be mutational “hot spots”. This paper highlights the functional and clinical characteristics of RCM linked mutations within the troponin complex.

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Anti–Cardiac Troponin Autoantibodies Are Specific to the Conformational Epitopes Formed by Cardiac Troponin I and Troponin T in the Ternary Troponin Complex

Clinical Chemistry ◽

10.1373/clinchem.2016.261602 ◽

2017 ◽

Vol 63 (1) ◽

pp. 343-350 ◽

Cited By ~ 15

Author(s):

Alexandra V Vylegzhanina ◽

Alexander E Kogan ◽

Ivan A Katrukha ◽

Olga V Antipova ◽

Andrey N Kara ◽

...

Keyword(s):

Cardiac Troponin ◽

Complex I ◽

Troponin I ◽

Troponin T ◽

Early Stage ◽

Gel Filtration ◽

Inhibitory Effect ◽

Cardiac Troponin I ◽

Blood Samples ◽

Troponin Complex

Abstract BACKGROUND Autoantibodies to cardiac troponins (TnAAbs) could negatively affect cardiac troponin I (cTnI) measurements by TnAAbs-sensitive immunoassays. We investigated the epitope specificity of TnAAbs and its influence on cTnI immunodetection in patients with acute myocardial infarction (AMI). METHODS The specificity of TnAAbs was studied in immunoassays and gel-filtration experiments. The influence of TnAAbs on endogenous troponin measurements was studied in 35 plasma samples from 15 patients with AMI. RESULTS The inhibitory effect of TnAAbs on the cTnI immunodetection was observed only for the ternary cardiac troponin complex (I–T–C) and not for the binary cardiac troponin complex (I–C) or free cTnI. In the same TnAAbs-containing samples, the immunodetection of cardiac troponin T (cTnT) added in the form of I–T–C (but not free cTnT) was also inhibited in the assays that used monoclonal antibodies (mAbs) specific to the 223–242 epitope. The negative effects of TnAAbs on the measurements of endogenous cTnI in AMI samples were less than on the measurements of isolated I–T–C and decreased with time after the onset of symptoms. Early AMI blood samples might contain a mixture of the I–T–C and I–C complexes with the ratio gradually changing with the progression of the disease in favor of I–C. CONCLUSIONS The investigated TnAAbs are specific to the structural epitopes formed by cTnI and cTnT molecules in the I–T–C complex. AMI blood samples contain a mixture of I–C and I–T–C complexes. The concentrations of total cTnI at the early stage of AMI could be underestimated in approximately 5%–10% of patients if measured by TnAAbs-sensitive immunoassays.

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Ca2+-dependent Muscle Dysfunction Caused by Mutation of the Caenorhabditis elegans Troponin T-1 Gene

The Journal of Cell Biology ◽

10.1083/jcb.143.5.1201 ◽

1998 ◽

Vol 143 (5) ◽

pp. 1201-1213 ◽

Cited By ~ 15

Author(s):

Kristen McArdle ◽

Taylor StC. Allen ◽

Elizabeth A. Bucher

Keyword(s):

Caenorhabditis Elegans ◽

Thin Filament ◽

Body Wall ◽

Troponin I ◽

Troponin T ◽

Muscle Dysfunction ◽

Excessive Force ◽

Thin Filaments ◽

Attachment Sites

We have investigated the functions of troponin T (CeTnT-1) in Caenorhabditis elegans embryonic body wall muscle. TnT tethers troponin I (TnI) and troponin C (TnC) to the thin filament via tropomyosin (Tm), and TnT/Tm regulates the activation and inhibition of myosin-actin interaction in response to changes in intracellular [Ca2+]. Loss of CeTnT-1 function causes aberrant muscle trembling and tearing of muscle cells from their exoskeletal attachment sites (Myers, C.D., P.-Y. Goh, T. StC. Allen, E.A. Bucher, and T. Bogaert. 1996. J. Cell Biol. 132:1061–1077). We hypothesized that muscle tearing is a consequence of excessive force generation resulting from defective tethering of Tn complex proteins. Biochemical studies suggest that such defective tethering would result in either (a) Ca2+-independent activation, due to lack of Tn complex binding and consequent lack of inhibition, or (b) delayed reestablishment of TnI/TnC binding to the thin filament after Ca2+ activation and consequent abnormal duration of force. Analyses of animals doubly mutant for CeTnT-1 and for genes required for Ca2+ signaling support that CeTnT-1 phenotypes are dependent on Ca2+ signaling, thus supporting the second model and providing new in vivo evidence that full inhibition of thin filaments in low [Ca2+] does not require TnT.

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Association analysis of TNNI1/XbaI polimorphism on carcass quality in hybrid pigs

Acta Agraria Debreceniensis ◽

10.34101/actaagrar/65/1878 ◽

2015 ◽

pp. 59-62

Author(s):

Andrea Nyilasovits ◽

János Posta ◽

Levente Czeglédi ◽

László Babinszky

Keyword(s):

Troponin I ◽

Striated Muscle ◽

Meat Production ◽

Thin Filaments ◽

Potential Marker ◽

Pcr Rflp ◽

Troponin Complex ◽

Myosin Interaction ◽

Polymerase Chain ◽

Regulation Of Muscle Contraction

The contractile protein, which is encoded by troponin I 1 (TNNI1) gene, is located on the thin filaments of slow fibres in striated muscle. TNNI1 protein is a part of the troponin complex which plays an important role in regulation of muscle contraction by preventing actin-myosin interaction in absence of calcium. According to biological role, this gene can be potential marker for meat production related traits. The aim of this study is to define whether the previously reported gene polymorphism (EU743939:g.5174T>C) is connected with the slaughter traits measured in a standard slaughterhouse of the examined four-line European hybrid. The study included data from 404 gilts and barrows from 2 different samples. The polymorphism was detected using PCR-RFLP (Polymerase Chain Reaction-Restriction Fragment Length Polymorphism) method with XbaI restriction enzyme. In this study the allele frequencies were found as follows: C: 0.84 and 0.808; T: 0.16 and 0.192. Based on result of the present study no significant impact of polymorphisms on production parameters was found.

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Phosphorylation of troponin and the effects of interactions between the components of the complex

Biochemical Journal ◽

10.1042/bj1410733 ◽

1974 ◽

Vol 141 (3) ◽

pp. 733-743 ◽

Cited By ~ 165

Author(s):

Samuel V. Perry ◽

Heather A. Cole

Keyword(s):

Protein Kinase ◽

Troponin I ◽

Troponin T ◽

Troponin C ◽

Phosphorylase Kinase ◽

Significant Extent ◽

Dependent Protein Kinase ◽

Prolonged Incubation ◽

Troponin Complex ◽

Dependent Protein

1. The troponin complex from skeletal muscle contains approximately 1 mol of phosphate/80000g of complex, covalently bound to the troponin T component. 2. On prolonged incubation of the troponin complex or troponin T with phosphorylase kinase the phosphate content of troponin T was increased to approx. 3mol/mol. 3. On prolonged incubation of troponin I with phosphorylase kinase up to 1.6mol of phosphate/mol were incorporated. 4. Phosphorylation of troponin I was greatly inhibited by troponin C owing to the strong interaction between these proteins. Thus in the troponin complex troponin T was the main substrate for phosphorylase kinase. The phosphorylation of isolated troponin T was also inhibited by troponin C. 5. Troponin I was phosphorylated when the troponin complex was incubated with a bovine cardiac 3′:5′-cyclic AMP-dependent protein kinase. Troponin T either in its isolated form or in the troponin complex was not phosphorylated by bovine protein kinase to any significant extent under the conditions used. 6. If the troponin complex was dephosphorylated to 0.2mol/mol, or phosphorylated up to 2.5mol/mol there was no significant effect on the ability of normal concentrations to confer Ca2+sensitivity on the adenosine triphosphatase of densensitized actomyosin.

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Comparison of cardiac troponin T and I in healthy men and in aortic valve replacement

Clinical Chemistry and Laboratory Medicine (CCLM) ◽

10.1515/2004.206 ◽

2004 ◽

Vol 42 (9) ◽

Cited By ~ 2

Author(s):

Eberhard Gurr ◽

Knut Leitz

Keyword(s):

Aortic Valve ◽

Aortic Valve Replacement ◽

Valve Replacement ◽

Cardiac Troponin ◽

Troponin I ◽

Troponin T ◽

Method Comparison ◽

Cardiac Troponin T ◽

Thin Filaments ◽

Healthy Men

AbstractTroponins are of outstanding importance for the diagnosis of myocardial infarction. Cardiac troponin T (cTnT) and the various cardiac troponin I (cTnI) assays differ with respect to method comparison, diagnostic sensitivity and diagnostic specificity. To understand the differences in the diagnostic behavior of troponin assays, AccuTnI and Elecsys Troponin STAT were used in a group of healthy men and in the follow-up of patients with aortic valve replacement (AVR). Within the healthy subjects AccuTnI was able to differentiate two subgroups from each other, whereas the cTnT concentrations of all subjects were below the detection limit. In AVR patients, cTnT and cTnI correlated sufficiently, if the postoperative periods were taken into consideration. There was a rapid increase in cTnI within 24 h. In contrast, a broad peak was evident for cTnT between 48 and 120 h. The results emphasize more the differences in the release of cTnI and cTnT from the cytoplasm and the thin filaments of the cardiomyocytes than the modifications of the troponins circulating in the blood.

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Overexpression of troponin T in Drosophila muscles causes a decrease in the levels of thin-filament proteins

Biochemical Journal ◽

10.1042/bj20041240 ◽

2005 ◽

Vol 386 (1) ◽

pp. 145-152 ◽

Cited By ~ 9

Author(s):

Raquel MARCO-FERRERES ◽

Juan J. ARREDONDO ◽

Benito FRAILE ◽

Margarita CERVERA

Keyword(s):

Thin Filament ◽

Troponin I ◽

Troponin T ◽

Thin Filaments ◽

Muscle Formation ◽

Thin Filament Proteins ◽

Flight Muscles ◽

Transgenic Drosophila ◽

Regulated Thin Filament

Formation of the contractile apparatus in muscle cells requires co-ordinated activation of several genes and the proper assembly of their products. To investigate the role of TnT (troponin T) in the mechanisms that control and co-ordinate thin-filament formation, we generated transgenic Drosophila lines that overexpress TnT in their indirect flight muscles. All flies that overexpress TnT were unable to fly, and the loss of thin filaments themselves was coupled with ultrastructural perturbations of the sarcomere. In contrast, thick filaments remained largely unaffected. Biochemical analysis of these lines revealed that the increase in TnT levels could be detected only during the early stages of adult muscle formation and was followed by a profound decrease in the amount of this protein as well as that of other thin-filament proteins such as tropomyosin, troponin I and actin. The decrease in thin-filament proteins is not only due to degradation but also due to a decrease in their synthesis, since accumulation of their mRNA transcripts was also severely diminished. This decrease in expression levels of the distinct thin-filament components led us to postulate that any change in the amount of TnT transcripts might trigger the down-regulation of other co-regulated thin-filament components. Taken together, these results suggest the existence of a mechanism that tightly co-ordinates the expression of thin-filament genes and controls the correct stoichiometry of these proteins. We propose that the high levels of unassembled protein might act as a sensor in this process.

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