Key Points
- To identify and functionally characterize troponin I regulatory domains that govern calcium-activated contraction within the intact myofilaments of single adult cardiac myocytes.
- Replaced endogenous cardiac troponin I in adult cardiac myocytes via adenovirus-mediated gene transfer with slow skeletal troponin I or a skeletal-cardiac chimera.
- Evaluated contractile mechanics and calcium sensitivity in single, permeabilized myocytes under physiological and acidic pH conditions.
- Exogenous troponin I isoforms incorporated efficiently into myofilaments without altering overall sarcomere structure or the stoichiometry of other contractile proteins.
- Contractile analysis identified two distinct calcium-sensitive regulatory domains located at the amino terminus and the carboxyl terminus of troponin I.
- Isoform-dependent contractile dysfunction induced by acidic pH localized selectively to the carboxyl terminus of the troponin I protein.
Structured PICO
PPopulationAdult single cardiac myocytes
IInterventionAdenovirus-mediated gene transfer to replace endogenous cardiac troponin I with the slow skeletal isoform or a chimera of the slow skeletal and cardiac isoforms
OOutcomeContractile function (Ca(2+)-sensitive properties and acidic pH-induced contractile dysfunction)surrogate
This study defines multiple regulatory domains of troponin I operating in the intact myofilament, providing new insights into its Ca(2+)-sensitive properties during contraction.