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

2005 ◽  
Vol 386 (1) ◽  
pp. 145-152 ◽  
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.

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

1998 ◽  
Vol 143 (5) ◽  
pp. 1201-1213 ◽  
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.

scholarly journals Muscle abnormalities in Drosophila melanogaster heldup mutants are caused by missing or aberrant troponin-I isoforms.

1991 ◽  
Vol 114 (5) ◽  
pp. 941-951 ◽  
Author(s):  
C J Beall ◽  
E Fyrberg
Keyword(s):  
Drosophila Melanogaster ◽  
Thin Filament ◽  
Null Allele ◽  
Troponin I ◽  
Chain Gene ◽  
Muscle Degeneration ◽  
Thin Filaments ◽  
Functional Defect ◽  
Flight Muscles ◽  
Molecular Bases

We have investigated the molecular bases of muscle abnormalities in four Drosophila melanogaster heldup mutants. We find that the heldup gene encodes troponin-I, one of the principal regulatory proteins associated with skeletal muscle thin filaments. heldup3, heldup4, and heldup5 mutants, all of which have grossly abnormal flight muscle myofibrils, lack mRNAs encoding one or more troponin-I isoforms. In contrast, heldup2, an especially interesting mutant wherein flight muscles are atrophic, synthesizes the complete mRNA complement. By sequencing mutant troponin-I cDNAs we demonstrate that the molecular basis for muscle degeneration in heldup2 is conversion of an invariant alanine residue to valine. We finally show that degeneration of heldup2 thin filament/Z-disc networks can be prevented by eliminating thick filaments from flight muscles using a null allele of the sarcomeric myosin heavy chain gene. This latter observation suggests that actomyosin interactions exacerbate the structural or functional defect resulting from the troponin-I mutation.

Functional and evolutionary relationships of troponin C

2007 ◽  
Vol 32 (1) ◽  
pp. 16-27 ◽  
Author(s):  
Todd E. Gillis ◽  
Christian R. Marshall ◽  
Glen F. Tibbits
Keyword(s):  
Functional Properties ◽  
Thin Filament ◽  
Troponin I ◽  
Striated Muscle ◽  
Troponin T ◽  
Extensive Study ◽  
Troponin C ◽  
High Conservation ◽  
Cross Bridges ◽  
And Function

Striated muscle contraction is initiated when, following membrane depolarization, Ca2+ binds to the low-affinity Ca2+ binding sites of troponin C (TnC). The Ca2+ activation of this protein results in a rearrangement of the components (troponin I, troponin T, and tropomyosin) of the thin filament, resulting in increased interaction between actin and myosin and the formation of cross bridges. The functional properties of this protein are therefore critical in determining the active properties of striated muscle. To date there are 61 known TnCs that have been cloned from 41 vertebrate and invertebrate species. In vertebrate species there are also distinct fast skeletal muscle and cardiac TnC proteins. While there is relatively high conservation of the amino acid sequence of TnC homologs between species and tissue types, there is wide variation in the functional properties of these proteins. To date there has been extensive study of the structure and function of this protein and how differences in these translate into the functional properties of muscles. The purpose of this work is to integrate these studies of TnC with phylogenetic analysis to investigate how changes in the sequence and function of this protein, integrate with the evolution of striated muscle.

scholarly journals Cardiac muscle thin filament structures reveal calcium regulatory mechanism

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Yurika Yamada ◽  
Keiichi Namba ◽  
Takashi Fujii
Keyword(s):  
Cardiac Muscle ◽  
Actin Filament ◽  
Conformational Changes ◽  
Thin Filament ◽  
Structural Changes ◽  
Troponin I ◽  
Regulatory Mechanism ◽  
Troponin T ◽  
Terminal Region ◽  
Muscle Thin Filament

AbstractContraction of striated muscles is driven by cyclic interactions of myosin head projecting from the thick filament with actin filament and is regulated by Ca2+ released from sarcoplasmic reticulum. Muscle thin filament consists of actin, tropomyosin and troponin, and Ca2+ binding to troponin triggers conformational changes of troponin and tropomyosin to allow actin-myosin interactions. However, the structural changes involved in this regulatory mechanism remain unknown. Here we report the structures of human cardiac muscle thin filament in the absence and presence of Ca2+ by electron cryomicroscopy. Molecular models in the two states built based on available crystal structures reveal the structures of a C-terminal region of troponin I and an N-terminal region of troponin T in complex with the head-to-tail junction of tropomyosin together with the troponin core on actin filament. Structural changes of the thin filament upon Ca2+ binding now reveal the mechanism of Ca2+ regulation of muscle contraction.

Reply: The complementary role of cardiac troponin I and cardiac troponin T

2020 ◽  
Vol 78 ◽  
pp. 42
Author(s):  
Sjur H. Tveit ◽  
Peder L. Myhre ◽  
Helge Røsjø ◽  
Torbjørn Omland
Keyword(s):  
Cardiac Troponin ◽  
Troponin I ◽  
Troponin T ◽  
Cardiac Troponin I ◽  
Cardiac Troponin T ◽  
Complementary Role

scholarly journals Atomic resolution probe for allostery in the regulatory thin filament

2016 ◽  
Vol 113 (12) ◽  
pp. 3257-3262 ◽  
Author(s):  
Michael R. Williams ◽  
Sarah J. Lehman ◽  
Jil C. Tardiff ◽  
Steven D. Schwartz
Keyword(s):  
Binding Site ◽  
Human Disease ◽  
Calcium Binding ◽  
Cardiac Troponin ◽  
Thin Filament ◽  
Troponin I ◽  
Troponin T ◽  
Calcium Binding Site

Calcium binding and dissociation within the cardiac thin filament (CTF) is a fundamental regulator of normal contraction and relaxation. Although the disruption of this complex, allosterically mediated process has long been implicated in human disease, the precise atomic-level mechanisms remain opaque, greatly hampering the development of novel targeted therapies. To address this question, we used a fully atomistic CTF model to test both Ca2+ binding strength and the energy required to remove Ca2+ from the N-lobe binding site in WT and mutant troponin complexes that have been linked to genetic cardiomyopathies. This computational approach is combined with measurements of in vitro Ca2+ dissociation rates in fully reconstituted WT and cardiac troponin T R92L and R92W thin filaments. These human disease mutations represent known substitutions at the same residue, reside at a significant distance from the calcium binding site in cardiac troponin C, and do not affect either the binding pocket affinity or EF-hand structure of the binding domain. Both have been shown to have significantly different effects on cardiac function in vivo. We now show that these mutations independently alter the interaction between the Ca2+ ion and cardiac troponin I subunit. This interaction is a previously unidentified mechanism, in which mutations in one protein of a complex indirectly affect a third via structural and dynamic changes in a second to yield a pathogenic change in thin filament function that results in mutation-specific disease states. We can now provide atom-level insight that is potentially highly actionable in drug design.

scholarly journals The nebulin repeat protein Lasp regulates I-band architecture and filament spacing in myofibrils

2014 ◽  
Vol 206 (4) ◽  
pp. 559-572 ◽  
Author(s):  
Isabelle Fernandes ◽  
Frieder Schöck
Keyword(s):  
Thin Filament ◽  
Muscle Protein ◽  
Nemaline Myopathy ◽  
Single Amino Acid ◽  
Actin Binding ◽  
Filament Length ◽  
Thin Filaments ◽  
Single Amino Acid Change ◽  
Filament Spacing

Mutations in nebulin, a giant muscle protein with 185 actin-binding nebulin repeats, are the major cause of nemaline myopathy in humans. Nebulin sets actin thin filament length in sarcomeres, potentially by stabilizing thin filaments in the I-band, where nebulin and thin filaments coalign. However, the precise role of nebulin in setting thin filament length and its other functions in regulating power output are unknown. Here, we show that Lasp, the only member of the nebulin family in Drosophila melanogaster, acts at two distinct sites in the sarcomere and controls thin filament length with just two nebulin repeats. We found that Lasp localizes to the Z-disc edges to control I-band architecture and also localizes at the A-band, where it interacts with both actin and myosin to set proper filament spacing. Furthermore, introducing a single amino acid change into the two nebulin repeats of Lasp demonstrated different roles for each domain and established Lasp as a suitable system for studying nebulin repeat function.

Kinetics of high-sensitivity cardiac troponin T or troponin I compared to creatine kinase in patients with revascularized acute myocardial infarction

2015 ◽  
Vol 53 (5) ◽  
Author(s):  
Kamila Solecki ◽  
Anne Marie Dupuy ◽  
Nils Kuster ◽  
Florence Leclercq ◽  
Richard Gervasoni ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Acute Myocardial Infarction ◽  
Cardiac Troponin ◽  
Troponin I ◽  
Troponin T ◽  
High Sensitivity ◽  
Cardiac Troponin T ◽  
Significant Difference ◽  
Kinetics Of

AbstractCardiac biomarkers are the cornerstone of the biological definition of acute myocardial infarction (AMI). The key role of troponins in diagnosis of AMI is well established. Moreover, kinetics of troponin I (cTnI) and creatine kinase (CK) after AMI are correlated to the prognosis. New technical assessment like high-sensitivity cardiac troponin T (hs-cTnT) raises concerns because of its unclear kinetic following the peak. This study aims to compare kinetics of cTnI and hs-cTnT to CK in patients with large AMI successfully treated by percutaneous coronary intervention (PCI).We prospectively studied 62 patients with anterior AMI successfully reperfused with primary angioplasty. We evaluated two consecutive groups: the first one regularly assessed by both CK and cTnI methods and the second group by CK and hs-cTnT. Modeling of kinetics was realized using mixed effects with cubic splines.Kinetics of markers showed a peak at 7.9 h for CK, at 10.9 h (6.9–12.75) for cTnI and at 12 h for hs-cTnT. This peak was followed by a nearly log linear decrease for cTnI and CK by contrast to hs-cTnT which appeared with a biphasic shape curve marked by a second peak at 82 h. There was no significant difference between the decrease of cTnI and CK (p=0.63). CK fell by 79.5% (76.1–99.9) vs. cTnI by 86.8% (76.6–92.7). In the hs-cTnT group there was a significant difference in the decrease by 26.5% (9–42.9) when compared with CK that fell by 79.5% (64.3–90.7).Kinetic of hs-cTnT and not cTnI differs from CK. The role of hs-cTnT in prognosis has to be investigated.

scholarly journals Ubiquitylation by Trim32 causes coupled loss of desmin, Z-bands, and thin filaments in muscle atrophy

2012 ◽  
Vol 198 (4) ◽  
pp. 575-589 ◽  
Author(s):  
Shenhav Cohen ◽  
Bo Zhai ◽  
Steven P. Gygi ◽  
Alfred L. Goldberg
Keyword(s):  
Muscle Atrophy ◽  
Ubiquitin Ligase ◽  
Thin Filament ◽  
Thick Filament ◽  
Myofibrillar Proteins ◽  
Rapid Loss ◽  
Thin Filaments ◽  
Thin Filament Proteins ◽  
Rapid Destruction ◽  
Fiber Atrophy

During muscle atrophy, myofibrillar proteins are degraded in an ordered process in which MuRF1 catalyzes ubiquitylation of thick filament components (Cohen et al. 2009. J. Cell Biol. http://dx.doi.org/10.1083/jcb.200901052). Here, we show that another ubiquitin ligase, Trim32, ubiquitylates thin filament (actin, tropomyosin, troponins) and Z-band (α-actinin) components and promotes their degradation. Down-regulation of Trim32 during fasting reduced fiber atrophy and the rapid loss of thin filaments. Desmin filaments were proposed to maintain the integrity of thin filaments. Accordingly, we find that the rapid destruction of thin filament proteins upon fasting was accompanied by increased phosphorylation of desmin filaments, which promoted desmin ubiquitylation by Trim32 and degradation. Reducing Trim32 levels prevented the loss of both desmin and thin filament proteins. Furthermore, overexpression of an inhibitor of desmin polymerization induced disassembly of desmin filaments and destruction of thin filament components. Thus, during fasting, desmin phosphorylation increases and enhances Trim32-mediated degradation of the desmin cytoskeleton, which appears to facilitate the breakdown of Z-bands and thin filaments.

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