Calumin, a novel Ca2+-binding transmembrane protein on the endoplasmic reticulum - Monoclonal Antibodies

Calumin, a novel Ca2+-binding transmembrane protein on the endoplasmic reticulum
Received 21 June 2006; revised 10 October 2006; accepted 22 November 2006. Available online 3 January 2007
Miao Zhanga, b, 1, Tetsuo Yamazakic, 1, Masayuki Yazawaa, b, Susan Trevesd, Miyuki Nishia, b, Machiko Muraib, Eisuke Shibatab, Francesco Zorzatod and Hiroshi Takeshimaa, b
Cell Calcium
Volume 42, Issue 1, July 2007
ScienceDirect
Copyright ? 2006 Elsevier Ltd All rights reserved.
aDepartment of Biological Chemistry, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan
bDepartment of Medical Chemistry, Graduate School of Medicine, Tohoku University, Miyagi 980-8575, Japan
cThe 21st Century Center of Excellence Program, Graduate School of Medicine, Tohoku University, Miyagi 980-8575, Japan
dDepartment of Anesthesiology and Research, University of Basel Kantosspital, Basel, Switzerland
Abstract
We have identified a novel endoplasmic reticulum (ER)-resident protein, named ?calumin?, which is expressed in various tissues. This protein has a molecular mass of 60 kDa and is composed of an ER-luminal domain rich in acidic residues, a single transmembrane segment, and a large cytoplasmic domain. Biochemical experiments demonstrated that the amino-terminal luminal domain is capable of binding Ca2+ with a high capacity and moderate affinity. In embryonic fibroblasts derived from calumin-knockout mice exhibiting embryonic and neonatal lethality, fluorometric Ca2+ imaging detected insufficient Ca2+ contents in intracellular stores and attenuated store-operated Ca2+ entry. Moreover, the mutant fibroblasts were highly sensitive to cell death induced by ER stress. These observations suggest that calumin plays an essential role in ER Ca2+ handling and is also implicated in signaling from the ER, which is closely associated with cell-fate decision.
Keywords: Ca2+-binding protein; ER stress; Intracellular Ca2+ store; Knockout mouse; Store-operated Ca2+ entry
Abbreviations: ATF, activation of transcription factor; [Ca2+]i, intracellular [Ca2+]; CNX, calnexin; CBB, Coomassie brilliant blue; CPA, cyclopiazonic acid; CRT, calreticulin; eIF, eukaryotic translation initiation factor; ER, endoplasmic reticulum; GST, glutathione S-transferase; IRE, inositol-requiring transmembrane kinase; JNK, c-Jun N-terminal kinase; mAb, monoclonal antibody; MEF, mouse embryonic fibroblast; NFAT, nuclear factor of activated T cells; PERK, protein kinase like ER kinase; PCR, polymerase chain reaction; PDI, protein disulfide isomerase; SERCA, sarcoplasmic/endoplasmic Ca2+-Mg2+ ATPase; STS, staurosporine; SR, sarcoplasmic reticulum; TRAF, tumor necrosis factor-associated factor; TG, thapsigargin; TNF, tumor necrosis factor; TM, tunicamycin; UPR, unfold protein response; xbp, X-box-binding protein
Corresponding author at: Department of Biological Chemistry, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan. Tel.: +81 75 753 4572; fax: +81 75 753 4605.
1 Contributed equally to this work.
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