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We investigated the effect of 7 Hypertrophic Cardiomyopathy (HCM)-causing mutations in troponin T (TnT) on troponin function in thin filaments reconstituted with actin and human cardiac tropomyosin. We used the quantitative in vitro motility assay to study Ca(2+)-regulation of unloaded movement and its modulation by troponin I phosphorylation. Troponin from a patient with the K280N TnT mutation showed no difference in Ca(2+)-sensitivity when compared with donor heart troponin and the Ca(2+)-sensitivity was also independent of the troponin I phosphorylation level (uncoupled). The recombinant K280N TnT mutation increased Ca(2+)-sensitivity 1.7-fold and was also uncoupled. The R92Q TnT mutation in troponin from transgenic mouse increased Ca(2+)-sensitivity and was also completely uncoupled. Five TnT mutations (Δ14, Δ28 + 7, ΔE160, S179F and K273E) studied in recombinant troponin increased Ca(2+)-sensitivity and were all fully uncoupled. Thus, for HCM-causing mutations in TnT, Ca(2+)-sensitisation together with uncoupling in vitro is the usual response and both factors may contribute to the HCM phenotype. We also found that Epigallocatechin-3-gallate (EGCG) can restore coupling to all uncoupled HCM-causing TnT mutations. In fact the combination of Ca(2+)-desensitisation and re-coupling due to EGCG completely reverses both the abnormalities found in troponin with a TnT HCM mutation suggesting it may have therapeutic potential.

Original publication

DOI

10.1016/j.abb.2016.03.027

Type

Journal article

Journal

Arch Biochem Biophys

Publication Date

01/07/2016

Volume

601

Pages

113 - 120

Keywords

Ca(2+) regulation of contractility, Hypertrophic Cardiomyopathy, In vitro motility assay, Phosphorylation of troponin I, Troponin T, Actin Cytoskeleton, Animals, Calcium, Cardiomyopathy, Dilated, Cardiomyopathy, Hypertrophic, Catechin, Dose-Response Relationship, Drug, Heart, Humans, Mice, Mice, Transgenic, Mutation, Myocardial Contraction, Phosphorylation, Recombinant Proteins, Troponin I, Troponin T