title: Mutations in troponin T associated with Hypertrophic Cardiomyopathy increase Ca(2+)-sensitivity and suppress the modulation of Ca(2+)-sensitivity by troponin I phosphorylation.
abstract: 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.
authors.affiliation: Imperial College London, London, UK. Electronic address: a.messer@imperial.ac.uk.
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Messer
authors.affiliation: Imperial College London, London, UK.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Bayliss
authors.affiliation: University of Leicester, Leicester, UK.
authors.forename: Mohammed
authors.initials: M
authors.lastname: El-Mezgueldi
authors.affiliation: University of Oxford, Oxford, UK.
authors.forename: Charles S
authors.initials: CS
authors.lastname: Redwood
authors.affiliation: University of Birmingham, Birmingham, UK.
authors.forename: Douglas G
authors.initials: DG
authors.lastname: Ward
authors.affiliation: Imperial College London, London, UK.
authors.forename: Man-Ching
authors.initials: MC
authors.lastname: Leung
authors.affiliation: Imperial College London, London, UK.
authors.forename: Maria
authors.initials: M
authors.lastname: Papadaki
authors.affiliation: University of Sydney, Sydney, Australia.
authors.forename: Cristobal
authors.initials: C
authors.lastname: Dos Remedios
authors.affiliation: Imperial College London, London, UK.
authors.forename: Steven B
authors.initials: SB
authors.lastname: Marston
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000737:chemistry*; D002311:Cardiomyopathy, Dilated / Q000378:metabolism; D002312:Cardiomyopathy, Hypertrophic / Q000235:genetics* / Q000378:metabolism; D002392:Catechin / Q000031:analogs & derivatives / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D006321:Heart / Q000502:physiology; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation; D009200:Myocardial Contraction; D010766:Phosphorylation; D011994:Recombinant Proteins / Q000737:chemistry; D019210:Troponin I / Q000737:chemistry*; D020107:Troponin T / Q000235:genetics*
chemical_list: D011994:Recombinant Proteins; D019210:Troponin I; D020107:Troponin T; D002392:Catechin; C045651:epigallocatechin gallate; D002118:Calcium
keywords: Ca(2+) regulation of contractility; Hypertrophic Cardiomyopathy; In vitro motility assay; Phosphorylation of troponin I; Troponin T