Long-Range Effects of Familial Hypertrophic Cardiomyopathy Mutations E180G and D175N on the Properties of Tropomyosin

Citations Over TimeTop 10% of 2012 papers

Abstract

Cardiac α-tropomyosin (Tm) single-site mutations D175N and E180G cause familial hypertrophic cardiomyopathy (FHC). Previous studies have shown that these mutations increase both Ca(2+) sensitivity and residual contractile activity at low Ca(2+) concentrations, which causes incomplete relaxation during diastole resulting in hypertrophy and sarcomeric disarray. However, the molecular basis for the cause and the difference in the severity of the manifested phenotypes of disease are not known. In this work we have (1) used ATPase studies using reconstituted thin filaments in solution to show that these FHC mutants result in an increase in Ca(2+) sensitivity and an increased residual level of ATPase, (2) shown that both FHC mutants increase the rate of cleavage at R133, ~45 residues N-terminal to the mutations, when free and bound to actin, (3) shown that for Tm-E180G, the increase in the rate of cleavage is greater than that for D175N, and (4) shown that for E180G, cleavage also occurs at a new site 53 residues C-terminal to E180G, in parallel with cleavage at R133. The long-range decreases in dynamic stability due to these two single-site mutations suggest increases in flexibility that may weaken the ability of Tm to inhibit activity at low Ca(2+) concentrations for D175N and to a greater degree for E180G, which may contribute to differences in the severity of FHC.

Related Papers

• → Thin filament dysfunctions caused by mutations in tropomyosin Tpm3.12 and Tpm1.1(2019)39 cited
• → A role for actin flexibility in thin filament-mediated contractile regulation and myopathy(2020)27 cited
• → Several Aspects of Calcium Regulator Mechanisms Linked to Troponin(2003)3 cited
• → Molecular basis of stiff patient syndrome caused by mutations in ACTA1 and TPM3(2015)
• → Tropomyosin Translocation on F-Actin Revealed by Molecular Dynamics Simulations(2018)