Deletion of the titin N2B region accelerates myofibrillar force development but does not alter relaxation kinetics.
J Cell Sci
; 127(Pt 17): 3666-74, 2014 Sep 01.
Article
em En
| MEDLINE
| ID: mdl-24982444
ABSTRACT
Cardiac titin is the main determinant of sarcomere stiffness during diastolic relaxation. To explore whether titin stiffness affects the kinetics of cardiac myofibrillar contraction and relaxation, we used subcellular myofibrils from the left ventricles of homozygous and heterozygous N2B-knockout mice which express truncated cardiac titins lacking the unique elastic N2B region. Compared with myofibrils from wild-type mice, myofibrils from knockout and heterozygous mice exhibit increased passive myofibrillar stiffness. To determine the kinetics of Ca(2+)-induced force development (rate constant kACT), myofibrils from knockout, heterozygous and wild-type mice were stretched to the same sarcomere length (2.3 µm) and rapidly activated with Ca(2+). Additionally, mechanically induced force-redevelopment kinetics (rate constant kTR) were determined by slackening and re-stretching myofibrils during Ca(2+)-mediated activation. Myofibrils from knockout mice exhibited significantly higher kACT, kTR and maximum Ca(2+)-activated tension than myofibrils from wild-type mice. By contrast, the kinetic parameters of biphasic force relaxation induced by rapidly reducing [Ca(2+)] were not significantly different among the three genotypes. These results indicate that increased titin stiffness promotes myocardial contraction by accelerating the formation of force-generating cross-bridges without decelerating relaxation.
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Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Sarcômeros
/
Deleção de Sequência
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Conectina
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Relaxamento Muscular
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Contração Miocárdica
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Miofibrilas
Limite:
Animals
Idioma:
En
Revista:
J Cell Sci
Ano de publicação:
2014
Tipo de documento:
Article
País de afiliação:
Alemanha