scholarly journals Mechanical dysfunction of the sarcomere induced by a pathogenic mutation in troponin T drives cellular adaptation

2021 ◽  
Vol 153 (5) ◽  
Author(s):  
Sarah R. Clippinger ◽  
Paige E. Cloonan ◽  
Wei Wang ◽  
Lina Greenberg ◽  
W. Tom Stump ◽  
...  
Keyword(s):  
Troponin T ◽  
Pathogenic Mutation ◽  
Familial Hypertrophic Cardiomyopathy ◽  
Calcium Handling ◽  
Molecular Defect ◽  
Sarcomeric Proteins ◽  
Early Disease ◽  
Mechanical Tension ◽  
Disease Pathogenesis ◽  
Functional Changes

Familial hypertrophic cardiomyopathy (HCM), a leading cause of sudden cardiac death, is primarily caused by mutations in sarcomeric proteins. The pathogenesis of HCM is complex, with functional changes that span scales, from molecules to tissues. This makes it challenging to deconvolve the biophysical molecular defect that drives the disease pathogenesis from downstream changes in cellular function. In this study, we examine an HCM mutation in troponin T, R92Q, for which several models explaining its effects in disease have been put forward. We demonstrate that the primary molecular insult driving disease pathogenesis is mutation-induced alterations in tropomyosin positioning, which causes increased molecular and cellular force generation during calcium-based activation. Computational modeling shows that the increased cellular force is consistent with the molecular mechanism. These changes in cellular contractility cause downstream alterations in gene expression, calcium handling, and electrophysiology. Taken together, our results demonstrate that molecularly driven changes in mechanical tension drive the early disease pathogenesis of familial HCM, leading to activation of adaptive mechanobiological signaling pathways.

Mechanical dysfunction induced by a hypertrophic cardiomyopathy mutation is the primary driver of cellular adaptation

2020 ◽  
Author(s):  
Sarah R. Clippinger ◽  
Paige E. Cloonan ◽  
Wei Wang ◽  
Lina Greenberg ◽  
W. Tom Stump ◽  
...  
Keyword(s):  
Hypertrophic Cardiomyopathy ◽  
Troponin T ◽  
Familial Hypertrophic Cardiomyopathy ◽  
Calcium Handling ◽  
Molecular Defect ◽  
Sarcomeric Proteins ◽  
Mechanical Tension ◽  
Disease Pathogenesis ◽  
Functional Changes ◽  
Primary Driver

AbstractFamilial hypertrophic cardiomyopathy (HCM), a leading cause of sudden cardiac death, is primarily caused by mutations in sarcomeric proteins. The pathogenesis of HCM is complex, with functional changes that span scales from molecules to tissues. This makes it challenging to deconvolve the biophysical molecular defect that drives the disease pathogenesis from downstream changes in cellular function. Here, we examined a HCM mutation in troponin T, R92Q. We demonstrate that the primary molecular insult driving the disease pathogenesis is mutation-induced alterations in tropomyosin positioning, which causes increased molecular and cellular force generation during calcium-based activation. We demonstrate computationally that these increases in force are direct consequences of the initial molecular insult. This altered cellular contractility causes downstream alterations in gene expression, calcium handling, and electrophysiology. Taken together, our results demonstrate that molecularly driven changes in mechanical tension drive the early disease pathogenesis, leading to activation of adaptive mechanobiological signaling pathways.

scholarly journals Temporal and mutation-specific alterations in Ca2+ homeostasis differentially determine the progression of cTnT-related cardiomyopathies in murine models

2009 ◽  
Vol 297 (2) ◽  
pp. H614-H626 ◽  
Author(s):  
Pia J. Guinto ◽  
Todd E. Haim ◽  
Candice C. Dowell-Martino ◽  
Nathaniel Sibinga ◽  
Jil C. Tardiff
Keyword(s):  
Hypertrophic Cardiomyopathy ◽  
Ventricular Myocytes ◽  
Troponin T ◽  
Early Time ◽  
Left Ventricular ◽  
Familial Hypertrophic Cardiomyopathy ◽  
Compensatory Mechanism ◽  
Missense Mutations ◽  
Tail Domain ◽  
Cellular Mechanics

Naturally occurring mutations in cardiac troponin T (cTnT) result in a clinical subset of familial hypertrophic cardiomyopathy. To determine the mechanistic links between thin-filament mutations and cardiovascular phenotypes, we have generated and characterized several transgenic mouse models carrying cTnT mutations. We address two central questions regarding the previously observed changes in myocellular mechanics and Ca2+ homeostasis: 1) are they characteristic of all severe cTnT mutations, and 2) are they primary (early) or secondary (late) components of the myocellular response? Adult left ventricular myocytes were isolated from 2- and 6-mo-old transgenic mice carrying missense mutations at residue 92, flanking the TNT1 NH2-terminal tail domain. Results from R92L and R92W myocytes showed mutation-specific alterations in contraction and relaxation indexes at 2 mo with improvements by 6 mo. Alterations in Ca2+ kinetics remained consistent with mechanical data in which R92L and R92W exhibited severe diastolic impairments at the early time point that improved with increasing age. A normal regulation of Ca2+ kinetics in the context of an altered baseline cTnI phosphorylation suggested a pathogenic mechanism at the myofilament level taking precedence for R92L. The quantitation of Ca2+-handling proteins in R92W mice revealed a synergistic compensatory mechanism involving an increased Ser16 and Thr17 phosphorylation of phospholamban, contributing to the temporal onset of improved cellular mechanics and Ca2+ homeostasis. Therefore, independent cTnT mutations in the TNT1 domain result in primary mutation-specific effects and a differential temporal onset of altered myocellular mechanics, Ca2+ kinetics, and Ca2+ homeostasis, complex mechanisms which may contribute to the clinical variability in cTnT-related familial hypertrophic cardiomyopathy mutations.

Troponins, intrinsic disorder, and cardiomyopathy

2016 ◽  
Vol 397 (8) ◽  
pp. 731-751 ◽  
Author(s):  
Insung Na ◽  
Min J. Kong ◽  
Shelby Straight ◽  
Jose R. Pinto ◽  
Vladimir N. Uversky
Keyword(s):  
Posttranslational Modifications ◽  
Cardiac Troponin ◽  
Troponin I ◽  
Troponin T ◽  
Intrinsic Disorder ◽  
Functional Changes ◽  
Intrinsically Disordered ◽  
Intrinsically Disordered Regions ◽  
Structural And Functional Properties ◽  
Protein Intrinsic Disorder

Abstract Cardiac troponin is a dynamic complex of troponin C, troponin I, and troponin T (TnC, TnI, and TnT, respectively) found in the myocyte thin filament where it plays an essential role in cardiac muscle contraction. Mutations in troponin subunits are found in inherited cardiomyopathies, such as hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM). The highly dynamic nature of human cardiac troponin and presence of numerous flexible linkers in its subunits suggest that understanding of structural and functional properties of this important complex can benefit from the consideration of the protein intrinsic disorder phenomenon. We show here that mutations causing decrease in the disorder score in TnI and TnT are significantly more abundant in HCM and DCM than mutations leading to the increase in the disorder score. Identification and annotation of intrinsically disordered regions in each of the troponin subunits conducted in this study can help in better understanding of the roles of intrinsic disorder in regulation of interactomes and posttranslational modifications of these proteins. These observations suggest that disease-causing mutations leading to a decrease in the local flexibility of troponins can trigger a whole plethora of functional changes in the heart.

Phenotypic Variation of Familial Hypertrophic Cardiomyopathy Caused by the Phe110→Ile Mutation in Cardiac Troponin T

Cardiology ◽  
2000 ◽  
Vol 93 (3) ◽  
pp. 155-162 ◽  
Author(s):  
Tong-Lang Lin ◽  
Sahoko Ichihara ◽  
Yoshiji Yamada ◽  
Tetsuo Nagasaka ◽  
Hitoshi Ishihara ◽  
...  
Keyword(s):  
Hypertrophic Cardiomyopathy ◽  
Phenotypic Variation ◽  
Cardiac Troponin ◽  
Troponin T ◽  
Familial Hypertrophic Cardiomyopathy ◽  
Cardiac Troponin T
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