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 journalArticle

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

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Phosphorylation
Troponin I
Cyclic AMP-Dependent Protein Kinases
Muscle
Myocardium
Chemical activation
Fibers
Troponin C
Sarcomeres
Protein Kinases
Adenosine Triphosphate
Myofibrils
Rats

All Science Journal Classification (ASJC) codes

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology

Cite this

Effect of troponin I phosphorylation by protein kinase A on length-dependence of tension activation in skinned cardiac muscle fibers. / Kajiwara, Hidetoshi; Morimoto, Sachio; Fukuda, Norio; Ohtsuki, Iwao; Kurihara, Satoshi.

In: Biochemical and Biophysical Research Communications, Vol. 272, No. 1, 27.05.2000, p. 104-110.

Research output: Contribution to journalArticle

Kajiwara, Hidetoshi ; Morimoto, Sachio ; Fukuda, Norio ; Ohtsuki, Iwao ; Kurihara, Satoshi. / Effect of troponin I phosphorylation by protein kinase A on length-dependence of tension activation in skinned cardiac muscle fibers. In: Biochemical and Biophysical Research Communications. 2000 ; Vol. 272, No. 1. pp. 104-110.
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