Calsequestrin, a calcium sequestering protein localized at the sarcoplasmic reticulum, is not essential for body-wall muscle function in Caenorhabditis elegans.
Calsequestrin is the major calcium-binding protein of cardiac and skeletal muscles whose function is to sequester Ca(2+ )in the lumen of the sarcoplasmic reticulum (SR). Here we describe the identification and functional characterization of a C. elegans calsequestrin gene (csq-1). CSQ-1 shows moderate similarity (50% similarity, 30% identity) to rabbit skeletal calsequestrin. Unlike mammals, which have two different genes encoding cardiac and fast-twitch skeletal muscle isoforms, csq-1 is the only calsequestrin gene in the C. elegans genome. We show that csq-1 is highly expressed in the body-wall muscles, beginning in mid-embryogenesis and maintained through the adult stage. In body-wall muscle cells, CSQ-1 is localized to sarcoplasmic membranes surrounding sarcomeric structures, in the regions where ryanodine receptors (UNC-68) are located. Mutation in UNC-68 affects CSQ-1 localization, suggesting that the two possibly interact in vivo. Genetic analyses of chromosomal deficiency mutants deleting csq-1 show that CSQ-1 is not essential for initiation of embryonic muscle formation and contraction. Furthermore, double-stranded RNA injection resulted in animals completely lacking CSQ-1 in body-wall muscles with no observable defects in locomotion. These findings suggest that although CSQ-1 is one of the major calcium-binding proteins in the body-wall muscles of C. elegans, it is not essential for body-wall muscle formation and contraction.
Cho
J H
JH
Department of Life Science, Kwangju Institute of Science and Technology, Kwangju, Korea.
Oh
Y S
YS
Park
K W
KW
Yu
J
J
Choi
K Y
KY
Shin
J Y
JY
Kim
D H
DH
Park
W J
WJ
Hamada
T
T
Kagawa
H
H
Maryon
E B
EB
Bandyopadhyay
J
J
Ahnn
J
J
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017173:Caenorhabditis elegans / Q000235:genetics / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D002155:Calsequestrin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D017353:Gene Deletion; D017238:Genes, Helminth; D006801:Humans; D008322:Mammals; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000502:physiology*; D011817:Rabbits; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D012519:Sarcoplasmic Reticulum / Q000502:physiology* / Q000648:ultrastructure; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D002155:Calsequestrin; D011994:Recombinant Proteins; D002118:Calcium