title: Micromechanical thermal assays of Ca2+-regulated thin-filament function and modulation by hypertrophic cardiomyopathy mutants of human cardiac troponin.
abstract: 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.
authors.affiliation: Department of Biological Science, The Florida State University, Tallahassee, FL 32306, USA.
authors.forename: Nicolas M
authors.initials: NM
authors.lastname: Brunet
authors.forename: Goran
authors.initials: G
authors.lastname: Mihajlović
authors.forename: Khaled
authors.initials: K
authors.lastname: Aledealat
authors.forename: Fang
authors.initials: F
authors.lastname: Wang
authors.forename: Peng
authors.initials: P
authors.lastname: Xiong
authors.forename: Stephan
authors.initials: S
authors.lastname: von Molnár
authors.forename: P Bryant
authors.initials: PB
authors.lastname: Chase
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism* / Q000502:physiology; D000199:Actins / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D006332:Cardiomegaly / Q000235:genetics / Q000378:metabolism*; D002623:Chemistry Techniques, Analytical; D006801:Humans; D007700:Kinetics; D016014:Linear Models; D008954:Models, Biological; D009154:Mutation; D015879:Myosin Subfragments / Q000378:metabolism; D011817:Rabbits; D011994:Recombinant Proteins / Q000378:metabolism; D013696:Temperature; D014335:Tropomyosin / Q000378:metabolism; D014336:Troponin / Q000235:genetics / Q000378:metabolism*
chemical_list: D000199:Actins; D015879:Myosin Subfragments; D011994:Recombinant Proteins; D014335:Tropomyosin; D014336:Troponin; D002118:Calcium