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First published online 3 April 2007
doi: 10.1242/jcs.001016

Journal of Cell Science 120, 1551-1558 (2007)
Published by The Company of Biologists 2007
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Research Article

Functional importance of polymerization and localization of calsequestrin in C. elegans

J. H. Cho1,*, K. M. Ko1,*, Gunasekaran Singaruvelu1, Wonhae Lee1, Gil Bu Kang1, Seong-Hwan Rho1, Byung-Jae Park1, Jae-Ran Yu2, Hiroaki Kagawa3, S. H. Eom1, D. H. Kim1 and Joohong Ahnn1,{ddagger}

1 Department of Life Science, Gwangju Institute of Science and Technology, Gwangju, 500-712, Korea
2 Department of Parasitology, College of Medicine, Kon-Kuk University, Chungju, 380-710, Korea
3 Department of Biology, Faculty of Science, Okayama University, Okayama, 700-8530, Japan

{ddagger} Author for correspondence (e-mail: joohong{at}gist.ac.kr)

Accepted 28 February 2007

Dual roles of calsequestrin (CSQ-1) being the Ca2+ donor and Ca2+ acceptor make it an excellent Ca2+-buffering protein within the sarcoplasmic reticulum (SR). We have isolated and characterized a calsequestrin (csq-1)-null mutant in Caenorhabditis elegans. To our surprise, this mutant csq-1(jh109) showed no gross defects in muscle development or function but, however, is highly sensitive to perturbation of Ca2+ homeostasis. By taking advantage of the viable null mutant, we investigated the domains of CSQ-1 that are important for polymerization and cellular localization, and required for its correct buffering functions. In transgenic animals rescued with various CSQ-1 constructs, the in vivo patterns of polymerization and localization of several mutated calsequestrins were observed to correlate with the structure-function relationship. Our results suggest that polymerization of CSQ-1 is essential but not sufficient for correct cellular localization and function of CSQ-1. In addition, direct interaction between CSQ-1 and the ryanodine receptor (RyR) was found for the first time, suggesting that the cellular localization of CSQ-1 in C. elegans is indeed modulated by RyR through a physical interaction.

Key words: Calsequestrin, Ca2+ buffering, Polymerization, Localization, RyR






© The Company of Biologists Ltd 2007