title: Calsequestrin (CASQ1) rescues function and structure of calcium release units in skeletal muscles of CASQ1-null mice.
abstract: Amplitude of Ca(2+) transients, ultrastructure of Ca(2+) release units, and molecular composition of sarcoplasmic reticulum (SR) are altered in fast-twitch skeletal muscles of calsequestrin-1 (CASQ1)-null mice. To determine whether such changes are directly caused by CASQ1 ablation or are instead the result of adaptive mechanisms, here we assessed ability of CASQ1 in rescuing the null phenotype. In vivo reintroduction of CASQ1 was carried out by cDNA electro transfer in flexor digitorum brevis muscle of the mouse. Exogenous CASQ1 was found to be correctly targeted to the junctional SR (jSR), as judged by immunofluorescence and confocal microscopy; terminal cisternae (TC) lumen was filled with electron dense material and its width was significantly increased, as judged by electron microscopy; peak amplitude of Ca(2+) transients was significantly increased compared with null muscle fibers transfected only with green fluorescent protein (control); and finally, transfected fibers were able to sustain cytosolic Ca(2+) concentration during prolonged tetanic stimulation. Only the expression of TC proteins, such as calsequestrin 2, sarcalumenin, and triadin, was not rescued as judged by Western blot. Thus our results support the view that CASQ1 plays a key role in both Ca(2+) homeostasis and TC structure.
authors: Dept. of Experimental Biomedical Sciences, Univ. of Padova, Italy.
authors: Mirta
authors: M
authors: Tomasi
authors: Marta
authors: M
authors: Canato
authors: Cecilia
authors: C
authors: Paolini
authors: Marco
authors: M
authors: Dainese
authors: Carlo
authors: C
authors: Reggiani
authors: Pompeo
authors: P
authors: Volpe
authors: Feliciano
authors: F
authors: Protasi
authors: Alessandra
authors: A
authors: Nori
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D002155:Calsequestrin / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D018076:DNA, Complementary; D056966:Excitation Contraction Coupling; D005260:Female; D049452:Green Fluorescent Proteins / Q000235:genetics; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018485:Muscle Fibers, Skeletal / Q000378:metabolism* / Q000502:physiology / Q000648:ultrastructure*; D009124:Muscle Proteins / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism / Q000502:physiology
chemical_list: D002135:Calcium-Binding Proteins; D002155:Calsequestrin; D002352:Carrier Proteins; C503130:Casq1 protein, mouse; D018076:DNA, Complementary; D008565:Membrane Proteins; D009124:Muscle Proteins; C514388:casq2 protein, mouse; C070048:triadin; C070323:sarcalumenin; D049452:Green Fluorescent Proteins; D002118:Calcium