TY - JOUR
T1 - Mutations in troponin T associated with Hypertrophic Cardiomyopathy increase Ca2+-sensitivity and suppress the modulation of Ca2+-sensitivity by troponin I phosphorylation
AU - Messer, Andrew E.
AU - Bayliss, Christopher R.
AU - El-mezgueldi, Mohammed
AU - Redwood, Charles S.
AU - Ward, Douglas G.
AU - Leung, Man-ching
AU - Papadaki, Maria
AU - Dos Remedios, Cristobal
AU - Marston, Steven B.
PY - 2016/6/4
Y1 - 2016/6/4
N2 - 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.
AB - 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.
KW - Hypertrophic Cardiomyopathy
KW - Troponin T
KW - Phosphorylation of troponin I
KW - Ca2+ regulation of contractility
KW - In vitro motility assay
U2 - 10.1016/j.abb.2016.03.027
DO - 10.1016/j.abb.2016.03.027
M3 - Article
SN - 0003-9861
VL - 601
SP - 113
EP - 120
JO - Archives of Biochemistry and Biophysics
JF - Archives of Biochemistry and Biophysics
ER -