期刊
JOURNAL OF EXPERIMENTAL BIOLOGY
卷 220, 期 5, 页码 828-836出版社
COMPANY OF BIOLOGISTS LTD
DOI: 10.1242/jeb.139717
关键词
Titin; Connectin; Muscle activation; Muscular; dystrophy with myositis (mdm); Elastic recoil
类别
资金
- National Science Foundation [IOS-1025806, IOS-1456868]
- W.M. Keck Foundation
- Division Of Integrative Organismal Systems
- Direct For Biological Sciences [1456868] Funding Source: National Science Foundation
- Division Of Integrative Organismal Systems
- Direct For Biological Sciences [1731917] Funding Source: National Science Foundation
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.
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