Lee, Keun Woo Maeng, Jin-Soo Choi, Jeong Yi Lee, Yu Ran Hwang, Chae Young Park, Sung Sup Park, Hyun Kyu Chung, Bong Hyun Lee, Seung-Goo Kim, Yeon-Soo Jeon, Hyesung Eom, Soo Hyun Kang, ChulHee Kim, Do Han Kwon, Ki-Sun 2024-01-20T15:33:19Z 2024-01-20T15:33:19Z 2021-09-05 2012-01-13 0021-9258 https://pubs.kist.re.kr/handle/201004/129641 Calsequestrin (CSQ), the major intrasarcoplasmic reticulum calcium storage protein, undergoes dynamic polymerization and depolymerization in a Ca2+-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) Ca2+ that were decondensed upon Ca2+ depletion. Moreover, CSQ2decondensation occurred only in the stoichiometric presence of junctin (JNT). When expressed alone, CSQ2 speckles remained unchanged, even after Ca2+ depletion. FRET analysis revealed constant interactions between CSQ2 and JNT, regardless of the SR Ca2+ 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 Ca2+ and JNT-dependent disassembly of the CSQ2 polymer. Accordingly, we conclude that reversible polymerization and depolymerization of CSQ are critical in SR Ca2+ homeostasis. English AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC SKELETAL-MUSCLE CALSEQUESTRIN RYANODINE RECEPTOR BINDING-PROTEIN RELEASE CHANNEL VENTRICULAR-TACHYCARDIA CARDIAC MYOCYTES CA2+ RELEASE CASQ2 CONTRACTILITY TRIADIN Role of Junctin Protein Interactions in Cellular Dynamics of Calsequestrin Polymer upon Calcium Perturbation Article 10.1074/jbc.M111.254045 1 JOURNAL OF BIOLOGICAL CHEMISTRY, v.287, no.3, pp.1679 - 1687 JOURNAL OF BIOLOGICAL CHEMISTRY 287 3 1679 1687 scie scopus 000299321000011 2-s2.0-84862908835 Biochemistry & Molecular Biology Biochemistry & Molecular Biology Article SKELETAL-MUSCLE CALSEQUESTRIN RYANODINE RECEPTOR BINDING-PROTEIN RELEASE CHANNEL VENTRICULAR-TACHYCARDIA CARDIAC MYOCYTES CA2+ RELEASE CASQ2 CONTRACTILITY TRIADIN