Role of junctin protein interactions in cellular dynamics of calsequestrin polymer upon calcium perturbation

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Title
Role of junctin protein interactions in cellular dynamics of calsequestrin polymer upon calcium perturbation
Author(s)
K W Lee; J S Maeng; Jung Yi Choi; Y R Lee; Chae Young Hwang; Sung Sup Park; Hyun Kyu Park; Bong Hyun Chung; Seung Goo Lee; Y S Kim; H Jeon; S H Eom; C H Kang; D H Kim; Ki Sun Kwon
Bibliographic Citation
Journal of Biological Chemistry, vol. 287, no. 13, pp. 1679-1687
Publication Year
2012
Abstract
Calsequestrin (CSQ), the major intrasarcoplasmic reticulum calcium storage protein, undergoes dynamic polymerization and depolymerization in a Ca 2+-dependent manner. However, no direct evidence of CSQ depolymerization in vivo with physiological relevance has been obtained. In the present study, live cell imaging analysis facilitated characterization of the in vivo dynamics of the macromolecular CSQ structure. CSQ2 appeared as speckles in the presence of normal sarcoplasmic reticulum (SR) Ca 2+ that were decondensed upon Ca 2+ depletion. Moreover, CSQ2 decondensation occurred only in the stoichiometric presence of junctin (JNT). When expressed alone, CSQ2 speckles remained unchanged, even after Ca 2+ depletion. FRET analysis revealed constant interactions between CSQ2 and JNT, regardless of the SR Ca 2+ concentration, implying that JNT is an essential component of the CSQ scaffold. In vitro solubility assay, electron microscopy, and atomic force microscopy studies using purified recombinant proteins confirmed Ca 2+and JNT-dependent disassembly of the CSQ2 polymer. Accordingly, we conclude that reversible polymerization and depolymerization of CSQ are critical in SR Ca 2+ homeostasis.
ISSN
0021-9258
Publisher
Amer Soc Biochemistry Molecular Biology Inc
DOI
http://dx.doi.org/10.1074/jbc.M111.254045
Type
Article
Appears in Collections:
Aging Convergence Research Center > 1. Journal Articles
Synthetic Biology and Bioengineering Research Institute > 1. Journal Articles
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