Mutations in troponin T associated with Hypertrophic Cardiomyopathy increase Ca2+-sensitivity and suppress the modulation of Ca2+-sensitivity by troponin I phosphorylation

Journal article

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 Ca2+-regulation of unloaded movement and its modulation by troponin I phosphorylation. Troponin from a patient with the K280N TnT mutation showed no difference in Ca2+-sensitivity when compared with donor heart troponin and the Ca2+-sensitivity was also independent of the troponin I phosphorylation level (uncoupled). The recombinant K280N TnT mutation increased Ca2+-sensitivity 1.7-fold and was also uncoupled. The R92Q TnT mutation in troponin from transgenic mouse increased Ca2+-sensitivity and was also completely uncoupled. Five TnT mutations (Δ14, Δ28 + 7, ΔE160, S179F and K273E) studied in recombinant troponin increased Ca2+-sensitivity and were all fully uncoupled. Thus, for HCM-causing mutations in TnT, Ca2+-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 Ca2+-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: Messer, A; Bayliss, C; El-Mezgueldi, M; Redwood, C; Ward, D

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Elsevier
• Journal: Archives of Biochemistry and Biophysics
• Volume: 601
• Pages: 113-120
• Publication date: 2016-03-29
• Acceptance date: 2016-03-26
• DOI: 10.1016/j.abb.2016.03.027
• EISSN: 1096-0384
• ISSN: 0003-9861
• Pmid: 27036851
• Language: English
• Keywords: in vitro motility assay; phosphorylation of troponin I; troponin T; hypertrophic cardiomyopathy; Ca(2+) regulation of contractility