title: Engineered troponin C constructs correct disease-related cardiac myofilament calcium sensitivity.
abstract: Aberrant myofilament Ca(2+) sensitivity is commonly observed with multiple cardiac diseases, especially familial cardiomyopathies. Although the etiology of the cardiomyopathies remains unclear, improving cardiac muscle Ca(2+) sensitivity through either pharmacological or genetic approaches shows promise of alleviating the disease-related symptoms. Due to its central role as the Ca(2+) sensor for cardiac muscle contraction, troponin C (TnC) stands out as an obvious and versatile target to reset disease-associated myofilament Ca(2+) sensitivity back to normal. To test the hypothesis that aberrant myofilament Ca(2+) sensitivity and its related function can be corrected through rationally engineered TnC constructs, three thin filament protein modifications representing different proteins (troponin I or troponin T), modifications (missense mutation, deletion, or truncation), and disease subtypes (familial or acquired) were studied. A fluorescent TnC was utilized to measure Ca(2+) binding to TnC in the physiologically relevant biochemical model system of reconstituted thin filaments. Consistent with the pathophysiology, the restrictive cardiomyopathy mutation, troponin I R192H, and ischemia-induced truncation of troponin I (residues 1-192) increased the Ca(2+) sensitivity of TnC on the thin filament, whereas the dilated cardiomyopathy mutation, troponin T ΔK210, decreased the Ca(2+) sensitivity of TnC on the thin filament. Rationally engineered TnC constructs corrected the abnormal Ca(2+) sensitivities of the thin filament, reconstituted actomyosin ATPase activity, and force generation in skinned trabeculae. Thus, the present study provides a novel and versatile therapeutic strategy to restore diseased cardiac muscle Ca(2+) sensitivity.
authors.affiliation: Department of Physiology and Cell Biology, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Bin
authors.initials: B
authors.lastname: Liu
authors.forename: Ryan S
authors.initials: RS
authors.lastname: Lee
authors.forename: Brandon J
authors.initials: BJ
authors.lastname: Biesiadecki
authors.forename: Svetlana B
authors.initials: SB
authors.lastname: Tikunova
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Davis
mesh_terms: D000818:Animals; D002118:Calcium / Q000737:chemistry / Q000378:metabolism*; D009202:Cardiomyopathies / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D009154:Mutation; D009200:Myocardial Contraction; D009210:Myofibrils / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015202:Protein Engineering; D051381:Rats; D019209:Troponin C / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D019209:Troponin C; D002118:Calcium