title: Calumin, a novel Ca2+-binding transmembrane protein on the endoplasmic reticulum.
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 approximately 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.
authors.affiliation: Department of Biological Chemistry, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan.
authors.forename: Miao
authors.initials: M
authors.lastname: Zhang
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Yamazaki
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yazawa
authors.forename: Susan
authors.initials: S
authors.lastname: Treves
authors.forename: Miyuki
authors.initials: M
authors.lastname: Nishi
authors.forename: Machiko
authors.initials: M
authors.lastname: Murai
authors.forename: Eisuke
authors.initials: E
authors.lastname: Shibata
authors.forename: Francesco
authors.initials: F
authors.lastname: Zorzato
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takeshima
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology; D002135:Calcium-Binding Proteins / Q000302:isolation & purification / Q000502:physiology*; D003001:Cloning, Molecular; D004721:Endoplasmic Reticulum / Q000737:chemistry*; D008565:Membrane Proteins / Q000302:isolation & purification / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D008970:Molecular Weight; D018384:Oxidative Stress / Q000502:physiology; D051381:Rats; D019284:Thapsigargin / Q000494:pharmacology; D014415:Tunicamycin / Q000494:pharmacology
chemical_list: D002135:Calcium-Binding Proteins; D008565:Membrane Proteins; D014415:Tunicamycin; D019284:Thapsigargin; D002118:Calcium