TY - JOUR
T1 - Functional analysis of troponin I regulatory domains in the intact myofilament of adult single cardiac myocytes
AU - Westfall, Margaret V.
AU - Albayya, Faris P.
AU - Metzger, Joseph M.
PY - 1999/8/6
Y1 - 1999/8/6
N2 - Troponin I is the putative molecular switch for Ca2+-activated contraction within the myofilament of striated muscles. To gain insight into functional troponin I domain(s) in the context of the intact myofilament, adenovirus-mediated gene transfer was used to replace endogenous cardiac troponin I within the myofilaments of adult cardiac myocytes with the slow skeletal isoform or a chimera of the slow skeletal and cardiac isoforms. Efficient expression and myofilament incorporation were observed in myocytes with each exogenous troponin I protein without detected changes in the stoichiometry of other contractile proteins and/or sarcomere architecture. Contractile function studies in single, permeabilized myocytes expressing exogenous troponin I provided support for the presence of a Ca2+-sensitive regulatory domain in the carboxyl terminus of troponin I and a second, newly defined Ca2+-sensitive domain residing in the amino terminus of troponin I. Additional experiments demonstrated that the isoform-specific, acidic pH- induced contractile dysfunction in myocytes appears to lie in the carboxyl terminus of troponin I. Functional results obtained from adult cardiac myocytes expressing the chimera or isoforms of troponin I now define multiple troponin I regulatory domains operating in the intact myofilament and provide new insight into the Ca2+-sensitive properties of troponin I during contraction.
AB - Troponin I is the putative molecular switch for Ca2+-activated contraction within the myofilament of striated muscles. To gain insight into functional troponin I domain(s) in the context of the intact myofilament, adenovirus-mediated gene transfer was used to replace endogenous cardiac troponin I within the myofilaments of adult cardiac myocytes with the slow skeletal isoform or a chimera of the slow skeletal and cardiac isoforms. Efficient expression and myofilament incorporation were observed in myocytes with each exogenous troponin I protein without detected changes in the stoichiometry of other contractile proteins and/or sarcomere architecture. Contractile function studies in single, permeabilized myocytes expressing exogenous troponin I provided support for the presence of a Ca2+-sensitive regulatory domain in the carboxyl terminus of troponin I and a second, newly defined Ca2+-sensitive domain residing in the amino terminus of troponin I. Additional experiments demonstrated that the isoform-specific, acidic pH- induced contractile dysfunction in myocytes appears to lie in the carboxyl terminus of troponin I. Functional results obtained from adult cardiac myocytes expressing the chimera or isoforms of troponin I now define multiple troponin I regulatory domains operating in the intact myofilament and provide new insight into the Ca2+-sensitive properties of troponin I during contraction.
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U2 - 10.1074/jbc.274.32.22508
DO - 10.1074/jbc.274.32.22508
M3 - Article
C2 - 10428827
AN - SCOPUS:0033529695
SN - 0021-9258
VL - 274
SP - 22508
EP - 22516
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 32
ER -