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Micromechanical Thermal Assays of Ca 2+ -Regulated Thin-Filament Function and Modulation by Hypertrophic Cardiomyopathy Mutants of Human Cardiac Troponin

2012; Hindawi Publishing Corporation; Volume: 2012; Linguagem: Inglês

10.1155/2012/657523

1110-7251

Nicolas M. Brunet, Goran Mihajlović, Khaled Aledealat, Fang Wang, Peng Xiong, Stephan von Molnár, P. Bryant Chase,

Muscle Physiology and Disorders

Microfabricated thermoelectric controllers can be employed to investigate mechanisms underlying myosin-driven sliding of Ca 2+ -regulated actin and disease-associated mutations in myofilament proteins. Specifically, we examined actin filament sliding—with or without human cardiac troponin (Tn) and α-tropomyosin (Tm)—propelled by rabbit skeletal heavy meromyosin, when temperature was varied continuously over a wide range (∼20–63 C ° ). At the upper end of this temperature range, reversible dysregulation of thin filaments occurred at pCa 9 and 5; actomyosin function was unaffected. Tn-Tm enhanced sliding speed at pCa 5 and increased a transition temperature ( T t ) between a high activation energy ( E a ) but low temperature regime and a low E a but high temperature regime. This was modulated by factors that alter cross-bridge number and kinetics. Three familial hypertrophic cardiomyopathy (FHC) mutations, cTnI R145G, cTnI K206Q, and cTnT R278C, cause dysregulation at temperatures ∼5–8 C ° lower; the latter two increased speed at pCa 5 at all temperatures.