Effect of troponin I phosphorylation by protein kinase A on length-dependence of tension activation in skinned cardiac muscle fibers

Hidetoshi Kajiwara, Sachio Morimoto, Norio Fukuda, Iwao Ohtsuki, Satoshi Kurihara

Research output: Contribution to journalArticlepeer-review

26 Citations (Scopus)

Abstract

We examined the effect of troponin I (TnI) phosphorylation by cAMP-dependent protein kinase (PKA) on the length-dependent tension activation in skinned rat cardiac trabeculae. Increasing sarcomere length shifted the pCa (-log[Ca2+])-tension relation to the left. Treatment with PKA decreased the Ca2+ sensitivity of the myofilament and also decreased the length-dependent shift of the pCa-tension relation. Replacement of endogenous TnI with phosphorylated TnI directly demonstrated that TnI phosphorylation is responsible for the decreased length-dependence. When MgATP concentration was lowered in the absence of Ca2+, tension was elicited through rigorous crossbridge-induced thin filament activation. Increasing sarcomere length shifted the pMgATP (-log[MgATP])-tension relation to the right, and either TnI phosphorylation or partial extraction of troponin C (TnC) abolished this length-dependent shift. We conclude that TnI phosphorylation by PKA attenuates the length-dependence of tension activation in cardiac muscle by decreasing the cross-bridge-dependent thin filament activation through a reduction of the interaction between TnI and TnC. (C) 2000 Academic Press.

Original languageEnglish
Pages (from-to)104-110
Number of pages7
JournalBiochemical and Biophysical Research Communications
Volume272
Issue number1
DOIs
Publication statusPublished - May 27 2000

All Science Journal Classification (ASJC) codes

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology

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