title: Differential effect of calsequestrin ablation on structure and function of fast and slow skeletal muscle fibers.
abstract: We compared structure and function of EDL and Soleus muscles in adult (4-6 m) mice lacking both Calsequestrin (CASQ) isoforms, the main SR Ca²⁺-binding proteins. Lack of CASQ induced ultrastructural alterations in ~30% of Soleus fibers, but not in EDL. Twitch time parameters were prolonged in both muscles, although tension was not reduced. However, when stimulated for 2 sec at 100 hz, Soleus was able to sustain contraction, while in EDL active tension declined by 70-80%. The results presented in this paper unmask a differential effect of CASQ1&2 ablation in fast versus slow fibers. CASQ is essential in EDL to provide large amount of Ca²⁺ released from the SR during tetanic stimulation. In contrast, Soleus deals much better with lack of CASQ because slow fibers require lower Ca²⁺ amounts and slower cycling to function properly. Nevertheless, Soleus suffers more severe structural damage, possibly because SR Ca²⁺ leak is more pronounced.
authors.affiliation: CeSI-Center for Research on Ageing & DNI-Department of Neuroscience and Imaging, Università Gabriele d'Annunzio of Chieti, 66100 Chieti, Italy.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Paolini
authors.forename: Marco
authors.initials: M
authors.lastname: Quarta
authors.forename: Laura
authors.initials: L
authors.lastname: D'Onofrio
authors.forename: Carlo
authors.initials: C
authors.lastname: Reggiani
authors.forename: Feliciano
authors.initials: F
authors.lastname: Protasi
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001835:Body Weight; D002135:Calcium-Binding Proteins / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D002155:Calsequestrin / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D005260:Female; D006651:Histocytochemistry; D053208:Kaplan-Meier Estimate; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009119:Muscle Contraction; D018656:Muscle Fibers, Fast-Twitch / Q000737:chemistry / Q000502:physiology*; D018657:Muscle Fibers, Slow-Twitch / Q000737:chemistry / Q000502:physiology*; D053580:Muscle Strength; D009129:Muscle Tonus; D020033:Protein Isoforms
chemical_list: D002135:Calcium-Binding Proteins; D002155:Calsequestrin; C503130:Casq1 protein, mouse; D020033:Protein Isoforms; C514388:casq2 protein, mouse