Effects of activation on the elastic properties of intact soleus muscles with a deletion in titin

Jenna A. Monroy, Krysta L. Powers, Cinnamon M. Pace, Theodore Uyeno, Kiisa C Nishikawa

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

Titin has long been known to contribute to muscle passive tension. Recently, it was also demonstrated that titin-based stiffness increases upon Ca2+ activation of wild-type mouse psoas myofibrils stretched beyond overlap of the thick and thin filaments. In addition, this increase in titin-based stiffness was impaired in single psoas myofibrils from mdm mice, characterized by a deletion in the N2A region of the Ttn gene. Here, we investigated the effects of activation on elastic properties of intact soleus muscles from wild-type and mdm mice to determine whether titin contributes to active muscle stiffness. Using load-clamp experiments, we compared the stress-strain relationships of elastic elements in active and passive muscles during unloading, and quantified the change in stiffness upon activation. Results from wild-type muscles show that upon activation, the elastic modulus increases, elastic elements develop force at 15% shorter lengths, and there was a 2.9-fold increase in the slope of the stress-strain relationship. These results are qualitatively and quantitatively similar to results from single wild-type psoas myofibrils. In contrast, mdm soleus showed no effect of activation on the slope or intercept of the stress-strain relationship, which is consistent with impaired titin activation observed in single mdm psoas myofibrils. Therefore, it is likely that titin plays a role in the increase of active muscle stiffness during rapid unloading. These results are consistent with the idea that, in addition to the thin filaments, titin is activated upon Ca2+ influx in skeletal muscle.

Original languageEnglish (US)
Pages (from-to)828-836
Number of pages9
JournalJournal of Experimental Biology
Volume220
Issue number5
DOIs
StatePublished - Mar 1 2017

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Keywords

  • Connectin
  • Elastic recoil
  • Muscle activation
  • Muscular dystrophy with myositis (mdm)
  • Titin

ASJC Scopus subject areas

  • Medicine(all)
  • Physiology
  • Ecology, Evolution, Behavior and Systematics
  • Aquatic Science
  • Molecular Biology
  • Animal Science and Zoology
  • Insect Science

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