Increased Ca2+ storage capacity of the skeletal muscle sarcoplasmic reticulum of transgenic mice over-expressing membrane bound calcium binding protein junctate.
Junctate is an integral sarco(endo)plasmic reticulum protein expressed in many tissues including heart and skeletal muscle. Because of its localization and biochemical characteristics, junctate is deemed to participate in the regulation of the intracellular Ca2+ concentration. However, its physiological function in muscle cells has not been investigated yet. In this study we examined the effects of junctate over-expression by generating a transgenic mouse model which over-expresses junctate in skeletal muscle. Our results demonstrate that junctate over-expression induced a significant increase in SR Ca2+ storage capacity which was paralleled by an increased 4-chloro-m-cresol and caffeine-induced Ca2+ release, whereas it did not affect SR Ca2+-dependent ATPase activity and SR Ca2+ loading rates. In addition, junctate over-expression did not affect the expression levels of SR Ca2+ binding proteins such as calsequestrin, calreticulin and sarcalumenin. These findings suggest that junctate over-expression is associated with an increase in the SR Ca2+ storage capacity and releasable Ca2+ content and support a physiological role for junctate in intracellular Ca2+ homeostasis.
Divet
Alexandra
A
Department of Experimental and Diagnostic Medicine, Section of General Pathology, University of Ferrara, Ferrara, Italy.
Paesante
Silvia
S
Grasso
Cristiano
C
Cavagna
Dario
D
Tiveron
Cecilia
C
Paolini
Cecilia
C
Protasi
Feliciano
F
Huchet-Cadiou
Corinne
C
Treves
Susan
S
Zorzato
Francesco
F
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D005838:Genotype; D006706:Homeostasis; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism*; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000502:physiology / Q000648:ultrastructure; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*
D002135:Calcium-Binding Proteins; D008565:Membrane Proteins; D009124:Muscle Proteins; C498841:Asph protein, mouse; D006899:Mixed Function Oxygenases; D000252:Calcium-Transporting ATPases; D002118:Calcium