{"title":"The effect of muscle length on post-tetanic potentiation of C57BL/6 and skMLCK<sup>-/-</sup> mouse EDL muscles.","authors":"Angelos Angelidis, Rene Vandenboom","doi":"10.1007/s10974-022-09620-6","DOIUrl":null,"url":null,"abstract":"<p><p>Post-tetanic potentiation of fast-twitch skeletal muscle is dependent on muscle length, with greater potentiation observed at shorter compared to longer lengths. The structural effects of the primary potentiation mechanism, phosphorylation of the regulatory light chain (RLC) of myosin, are thought to explain this relationship. The purpose of these experiments was to determine whether the length-dependence of potentiation would be attenuated in the absence of RLC phosphorylation. To this end, we compared isometric twitch potentiation of mouse extensor digitorum longus (EDL) muscles with (wildtype, WT) and without (skeletal myosin light chain kinase knockout, skMLCK<sup>-/-</sup>) phosphorylation. Force was measured at five muscle lengths (0.90 L<sub>o</sub>, 0.95 L<sub>o</sub>, L<sub>o</sub>, 1.05 L<sub>o</sub>, 1.10 L<sub>o</sub>, where L<sub>o</sub> refers to optimal length) prior to and following a tetanic train. In accordance with prior findings, potentiation was dependent on muscle length, with greater values observed at short (e.g., 44.3 ± 4.6% for WT, 33.5 ± 6.2% for skMLCK<sup>-/-</sup>, at 0.90 L<sub>o</sub>) compared to long lengths (e.g., 16.9 ± 1.3% for WT, 9.1 ± 1.8% for skMLCK<sup>-/-</sup>, at 1.10 L<sub>o</sub>) in both genotypes. WT muscles displayed greater potentiation compared to their skMLCK<sup>-/-</sup> counterparts across lengths (e.g., 16.9 ± 1.6% vs 7.3 ± 1.5% at L<sub>o</sub>). However, the relationship between potentiation and muscle length was not different between genotypes. Thus, the alternative mechanisms of potentiation, present in the skMLCK<sup>-/-</sup> EDL, display a length-dependence of post-tetanic potentiation similar to RLC phosphorylation-dominant potentiation. Additional mechanisms may be required to explain the length-dependence of potentiation.</p>","PeriodicalId":16422,"journal":{"name":"Journal of Muscle Research and Cell Motility","volume":"43 3","pages":"99-111"},"PeriodicalIF":1.8000,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Muscle Research and Cell Motility","FirstCategoryId":"99","ListUrlMain":"https://doi.org/10.1007/s10974-022-09620-6","RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"2022/6/30 0:00:00","PubModel":"Epub","JCR":"Q4","JCRName":"CELL BIOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
Post-tetanic potentiation of fast-twitch skeletal muscle is dependent on muscle length, with greater potentiation observed at shorter compared to longer lengths. The structural effects of the primary potentiation mechanism, phosphorylation of the regulatory light chain (RLC) of myosin, are thought to explain this relationship. The purpose of these experiments was to determine whether the length-dependence of potentiation would be attenuated in the absence of RLC phosphorylation. To this end, we compared isometric twitch potentiation of mouse extensor digitorum longus (EDL) muscles with (wildtype, WT) and without (skeletal myosin light chain kinase knockout, skMLCK-/-) phosphorylation. Force was measured at five muscle lengths (0.90 Lo, 0.95 Lo, Lo, 1.05 Lo, 1.10 Lo, where Lo refers to optimal length) prior to and following a tetanic train. In accordance with prior findings, potentiation was dependent on muscle length, with greater values observed at short (e.g., 44.3 ± 4.6% for WT, 33.5 ± 6.2% for skMLCK-/-, at 0.90 Lo) compared to long lengths (e.g., 16.9 ± 1.3% for WT, 9.1 ± 1.8% for skMLCK-/-, at 1.10 Lo) in both genotypes. WT muscles displayed greater potentiation compared to their skMLCK-/- counterparts across lengths (e.g., 16.9 ± 1.6% vs 7.3 ± 1.5% at Lo). However, the relationship between potentiation and muscle length was not different between genotypes. Thus, the alternative mechanisms of potentiation, present in the skMLCK-/- EDL, display a length-dependence of post-tetanic potentiation similar to RLC phosphorylation-dominant potentiation. Additional mechanisms may be required to explain the length-dependence of potentiation.
期刊介绍：
The Journal of Muscle Research and Cell Motility has as its main aim the publication of original research which bears on either the excitation and contraction of muscle, the analysis of any one of the processes involved therein, the processes underlying contractility and motility of animal and plant cells, the toxicology and pharmacology related to contractility, or the formation, dynamics and turnover of contractile structures in muscle and non-muscle cells. Studies describing the impact of pathogenic mutations in genes encoding components of contractile structures in humans or animals are welcome, provided they offer mechanistic insight into the disease process or the underlying gene function. The policy of the Journal is to encourage any form of novel practical study whatever its specialist interest, as long as it falls within this broad field. Theoretical essays are welcome provided that they are concise and suggest practical ways in which they may be tested. Manuscripts reporting new mutations in known disease genes without validation and mechanistic insight will not be considered. It is the policy of the journal that cells lines, hybridomas and DNA clones should be made available by the developers to any qualified investigator. Submission of a manuscript for publication constitutes an agreement of the authors to abide by this principle.
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