Familial hypertrophic cardiomyopathy mutations in troponin I (K183Δ, G203S, K206Q) enhance filament sliding

2003 ◽  
Vol 14 (2) ◽  
pp. 117-128 ◽  
Author(s):  
Jan Köhler ◽  
Ying Chen ◽  
Bernhard Brenner ◽  
Albert M. Gordon ◽  
Theresia Kraft ◽  
...  
Keyword(s):  
Hypertrophic Cardiomyopathy ◽  
Troponin I ◽  
Isometric Force ◽  
Familial Hypertrophic Cardiomyopathy ◽  
In Vitro Assays ◽  
Maximum Speed ◽  
Exchange Method ◽  
In Vitro Motility ◽  
Maximum Isometric Force

A major cause of familial hypertrophic cardiomyopathy (FHC) is dominant mutations in cardiac sarcomeric genes. Linkage studies identified FHC-related mutations in the COOH terminus of cardiac troponin I (cTnI), a region with unknown function in Ca2+ regulation of the heart. Using in vitro assays with recombinant rat troponin subunits, we tested the hypothesis that mutations K183Δ, G203S, and K206Q in cTnI affect Ca2+ regulation. All three mutants enhanced Ca2+ sensitivity and maximum speed ( smax) of filament sliding of in vitro motility assays. Enhanced smax (pCa 5) was observed with rabbit skeletal and rat cardiac (α-MHC or β-MHC) heavy meromyosin (HMM). We developed a passive exchange method for replacing endogenous cTn in permeabilized rat cardiac trabeculae. Ca2+ sensitivity and maximum isometric force did not differ between preparations exchanged with cTn(cTnI,K206Q) or wild-type cTn. In both trabeculae and motility assays, there was no loss of inhibition at pCa 9. These results are consistent with COOH terminus of TnI modulating actomyosin kinetics during unloaded sliding, but not during isometric force generation, and implicate enhanced cross-bridge cycling in the cTnI-related pathway(s) to hypertrophy.

scholarly journals Facilitated Cross-Bridge Interactions with Thin Filaments by Familial Hypertrophic Cardiomyopathy Mutations inα-Tropomyosin

2011 ◽  
Vol 2011 ◽  
pp. 1-12 ◽  
Author(s):  
Fang Wang ◽  
Nicolas M. Brunet ◽  
Justin R. Grubich ◽  
Ewa A. Bienkiewicz ◽  
Thomas M. Asbury ◽  
...  
Keyword(s):  
Hypertrophic Cardiomyopathy ◽  
Molecular Mechanisms ◽  
Helical Structure ◽  
Familial Hypertrophic Cardiomyopathy ◽  
Maximum Speed ◽  
Sliding Speed ◽  
Thin Filaments ◽  
In Vitro Motility ◽  
Cardiac Sarcomeres

Familial hypertrophic cardiomyopathy (FHC) is a disease of cardiac sarcomeres. To identify molecular mechanisms underlying FHC pathology, functional and structural differences in three FHC-related mutations in recombinantα-Tm (V95A, D175N, and E180G) were characterized using both conventional and modified in vitro motility assays and circular dichroism spectroscopy. Mutant Tm's exhibited reducedα-helical structure and increased unordered structure. When thin filaments were fully occupied by regulatory proteins, little or no motion was detected at pCa 9, and maximum speed (pCa 5) was similar for all tropomyosins. Ca2+-responsiveness of filament sliding speed was increased either by increasedpCa50(V95A), reduced cooperativityn(D175N), or both (E180G). When temperature was increased, thin filaments with E180G exhibited dysregulation at temperatures ~10°C lower, and much closer to body temperature, than WT. When HMM density was reduced, thin filaments with D175N required fewer motors to initiate sliding or achieve maximum sliding speed.

scholarly journals Impact of familial hypertrophic cardiomyopathy-linked mutations in the NH2 terminus of the RLC on β-myosin cross-bridge mechanics

2014 ◽  
Vol 117 (12) ◽  
pp. 1471-1477 ◽  
Author(s):  
Gerrie P. Farman ◽  
Priya Muthu ◽  
Katarzyna Kazmierczak ◽  
Danuta Szczesna-Cordary ◽  
Jeffrey R. Moore
Keyword(s):  
Hypertrophic Cardiomyopathy ◽  
Familial Hypertrophic Cardiomyopathy ◽  
Sarcomeric Proteins ◽  
Motion Generation ◽  
In Vitro Motility Assay ◽  
In Vitro Motility ◽  
Cross Bridge ◽  
Significant Difference ◽  
The Impact

Familial hypertrophic cardiomyopathy (HCM) is associated with mutations in sarcomeric proteins, including the myosin regulatory light chain (RLC). Here we studied the impact of three HCM mutations located in the NH2 terminus of the RLC on the molecular mechanism of β-myosin heavy chain (MHC) cross-bridge mechanics using the in vitro motility assay. To generate mutant β-myosin, native RLC was depleted from porcine cardiac MHC and reconstituted with mutant (A13T, F18L, and E22K) or wild-type (WT) human cardiac RLC. We characterized the mutant myosin force and motion generation capability in the presence of a frictional load. Compared with WT, all three mutants exhibited reductions in maximal actin filament velocity when tested under low or no frictional load. The actin-activated ATPase showed no significant difference between WT and HCM-mutant-reconstituted myosins. The decrease in velocity has been attributed to a significantly increased duty cycle, as was measured by the dependence of actin sliding velocity on myosin surface density, for all three mutant myosins. These results demonstrate a mutation-induced alteration in acto-myosin interactions that may contribute to the pathogenesis of HCM.

scholarly journals Hypertrophic cardiomyopathy R403Q mutation in rabbit β-myosin reduces contractile function at the molecular and myofibrillar levels

2018 ◽  
Vol 115 (44) ◽  
pp. 11238-11243 ◽  
Author(s):  
Susan Lowey ◽  
Vera Bretton ◽  
Peteranne B. Joel ◽  
Kathleen M. Trybus ◽  
James Gulick ◽  
...  
Keyword(s):  
Hypertrophic Cardiomyopathy ◽  
Contractile Function ◽  
Isometric Force ◽  
Single Point ◽  
Rabbit Model ◽  
Familial Hypertrophic Cardiomyopathy ◽  
Single Point Mutation ◽  
Loss Of Function ◽  
Transgenic Rabbits

In 1990, the Seidmans showed that a single point mutation, R403Q, in the human β-myosin heavy chain (MHC) of heart muscle caused a particularly malignant form of familial hypertrophic cardiomyopathy (HCM) [Geisterfer-Lowrance AA, et al. (1990) Cell 62:999–1006.]. Since then, more than 300 mutations in the β-MHC have been reported, and yet there remains a poor understanding of how a single missense mutation in the MYH7 gene can lead to heart disease. Previous studies with a transgenic mouse model showed that the myosin phenotype depended on whether the mutation was in an α- or β-MHC backbone. This led to the generation of a transgenic rabbit model with the R403Q mutation in a β-MHC backbone. We find that the in vitro motility of heterodimeric R403Q myosin is markedly reduced, whereas the actin-activated ATPase activity of R403Q subfragment-1 is about the same as myosin from a nontransgenic littermate. Single myofibrils isolated from the ventricles of R403Q transgenic rabbits and analyzed by atomic force microscopy showed reduced rates of force development and relaxation, and achieved a significantly lower steady-state level of isometric force compared with nontransgenic myofibrils. Myofibrils isolated from the soleus gave similar results. The force–velocity relationship determined for R403Q ventricular myofibrils showed a decrease in the velocity of shortening under load, resulting in a diminished power output. We conclude that independent of whether experiments are performed with isolated molecules or with ordered molecules in the native thick filament of a myofibril, there is a loss-of-function induced by the R403Q mutation in β-cardiac myosin.

Two mutations in troponin I that cause hypertrophic cardiomyopathy have contrasting effects on cardiac muscle contractility

2002 ◽  
Vol 362 (2) ◽  
pp. 443-451 ◽  
Author(s):  
David BURTON ◽  
Hassan ABDULRAZZAK ◽  
Adam KNOTT ◽  
Kathryn ELLIOTT ◽  
Charles REDWOOD ◽  
...  
Keyword(s):  
Hypertrophic Cardiomyopathy ◽  
Cardiac Troponin ◽  
Troponin I ◽  
Wild Type ◽  
Thin Filaments ◽  
In Vitro Motility ◽  
Inhibitory Function ◽  
Type Protein ◽  
Wild Type Protein

We investigated the effects of two mutations in human cardiac troponin I, Arg145 → Gly and Gly203 → Ser, that are reported to cause familial hypertrophic cardiomyopathy. Mutant and wild-type troponin I, overexpressed in Escherichia coli, were used to reconstitute troponin complexes in vanadate-treated guinea pig cardiac trabeculae skinned fibres, and thin filaments were reconstituted with human cardiac troponin and tropomyosin along with rabbit skeletal muscle actin for in vitro motility and actomyosin ATPase assays. Troponin containing the Arg145 → Gly mutation inhibited force in skinned trabeculae less than did the wild-type, and had almost no inhibitory function in the in vitro motility assay. There was an enhanced inhibitory function with mixtures of 10–30% [Gly145]troponin I with the wild-type protein. Skinned trabeculae reconstituted with troponin I containing the Gly203 → Ser mutation and troponin C produced less Ca2+-activated force (64±8% of wild-type) and demonstrated lower Ca2+ sensitivity [ΔpCa50 (log of the Ca2+ concentration that gave 50% of maximal activation) 0.25 unit (P < 0.05)] compared with wild-type troponin I, but thin filaments containing [Ser203]-troponin I were indistinguishable from those containing the wild-type protein in in vitro motility and ATPase assays. Thus these two mutations each result in hypertrophic cardiomyopathy, but have opposite effects on the overall contractility of the muscle in the systems we investigated, indicating either that we have not yet identified the relevant alteration in contractility for the Gly203 → Ser mutation, or that the disease does not result directly from any particular alteration in contractility.

Injury to skeletal muscle fibers of mice following lengthening contractions

1985 ◽  
Vol 59 (1) ◽  
pp. 119-126 ◽  
Author(s):  
K. K. McCully ◽  
J. A. Faulkner
Keyword(s):  
Skeletal Muscle ◽  
Isometric Force ◽  
Muscle Fibers ◽  
Lengthening Contractions ◽  
Control Value ◽  
Skeletal Muscle Fibers ◽  
Maximum Isometric Force ◽  
Distal Tendon ◽  
Shortening Contractions

We tested the hypothesis that lengthening contractions result in greater injury to skeletal muscle fibers than isometric or shortening contractions. Mice were anesthetized with pentobarbital sodium and secured to a platform maintained at 37 degrees C. The distal tendon of the extensor digitorum longus muscle was attached to a servomotor. A protocol consisting of isometric, shortening, or lengthening contractions was performed. After the contraction protocol the distal tendon was reattached, incisions were closed, and the mice were allowed to recover. The muscles were removed after 1–30 days, and maximum isometric force (Po) was measured in vitro at 37 degrees C. Three days after isometric and shortening contractions and sham operations, histological appearance was not different from control and Po was 80% of the control value. Three days after lengthening contractions, histological sections showed that 37 +/- 4% of muscle fibers degenerated and Po was 22 +/- 3% of the control value. Muscle regeneration, first seen at 4 days, was nearly complete by 30 days, when Po was 84 +/- 3% of the control value. We conclude that, with the protocol used, lengthening, but not isometric or shortening contractions, caused significant injury to muscle fibers.

scholarly journals Transgenic Modeling of a Cardiac Troponin I Mutation Linked to Familial Hypertrophic Cardiomyopathy

2000 ◽  
Vol 87 (9) ◽  
pp. 805-811 ◽  
Author(s):  
Jeanne James ◽  
Yan Zhang ◽  
Hanna Osinska ◽  
Atsushi Sanbe ◽  
Raisa Klevitsky ◽  
...  
Keyword(s):  
Hypertrophic Cardiomyopathy ◽  
Cardiac Troponin ◽  
Troponin I ◽  
Cardiac Troponin I ◽  
Familial Hypertrophic Cardiomyopathy

Functional Consequences of the Mutations in Human Cardiac Troponin I Gene Found in Familial Hypertrophic Cardiomyopathy

2001 ◽  
Vol 33 (12) ◽  
pp. 2095-2107 ◽  
Author(s):  
Fumi Takahashi-Yanaga ◽  
Sachio Morimoto ◽  
Keita Harada ◽  
Reiko Minakami ◽  
Fumie Shiraishi ◽  
...  
Keyword(s):  
Hypertrophic Cardiomyopathy ◽  
Cardiac Troponin ◽  
Troponin I ◽  
Cardiac Troponin I ◽  
Familial Hypertrophic Cardiomyopathy ◽  
Functional Consequences ◽  
I Gene

Calpain-1-dependent degradation of troponin I mutants found in familial hypertrophic cardiomyopathy

2003 ◽  
pp. 83-88
Author(s):  
Judit Barta ◽  
Attila Tóth ◽  
Kornelia Jaquet ◽  
Alexander Redlich ◽  
István Édes ◽  
...  
Keyword(s):  
Hypertrophic Cardiomyopathy ◽  
Troponin I ◽  
Familial Hypertrophic Cardiomyopathy

scholarly journals Discrete effects of A57G-myosin essential light chain mutation associated with familial hypertrophic cardiomyopathy

2013 ◽  
Vol 305 (4) ◽  
pp. H575-H589 ◽  
Author(s):  
Katarzyna Kazmierczak ◽  
Ellena C. Paulino ◽  
Wenrui Huang ◽  
Priya Muthu ◽  
Jingsheng Liang ◽  
...  
Keyword(s):  
Hypertrophic Cardiomyopathy ◽  
Light Chain ◽  
Left Ventricular ◽  
Compensatory Hypertrophy ◽  
Familial Hypertrophic Cardiomyopathy ◽  
Heart Weight ◽  
Myocardial Stiffness ◽  
Essential Light Chain

The functional consequences of the familial hypertrophic cardiomyopathy A57G (alanine-to-glycine) mutation in the myosin ventricular essential light chain (ELC) were assessed in vitro and in vivo using previously generated transgenic (Tg) mice expressing A57G-ELC mutant vs. wild-type (WT) of human cardiac ELC and in recombinant A57G- or WT-protein-exchanged porcine cardiac muscle strips. Compared with the Tg-WT, there was a significant increase in the Ca2+ sensitivity of force (ΔpCa50 ≅ 0.1) and an ∼1.3-fold decrease in maximal force per cross section of muscle observed in the mutant preparations. In addition, a significant increase in passive tension in response to stretch was monitored in Tg-A57G vs. Tg-WT strips indicating a mutation-induced myocardial stiffness. Consistently, the hearts of Tg-A57G mice demonstrated a high level of fibrosis and hypertrophy manifested by increased heart weight-to-body weight ratios and a decreased number of nuclei indicating an increase in the two-dimensional size of Tg-A57G vs. Tg-WT myocytes. Echocardiography examination showed a phenotype of eccentric hypertrophy in Tg-A57G mice, enhanced left ventricular (LV) cavity dimension without changes in LV posterior/anterior wall thickness. Invasive hemodynamics data revealed significantly increased end-systolic elastance, defined by the slope of the pressure-volume relationship, indicating a mutation-induced increase in cardiac contractility. Our results suggest that the A57G allele causes disease by means of a discrete modulation of myofilament function, increased Ca2+ sensitivity, and decreased maximal tension followed by compensatory hypertrophy and enhanced contractility. These and other contributing factors such as increased myocardial stiffness and fibrosis most likely activate cardiomyopathic signaling pathways leading to pathologic cardiac remodeling.

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