新着情報

○新規小胞体Ca2+結合タンパク質カルミンの分子同定　(2006. 11)

Calumin, a novel Ca2+-binding transmembrane protein on the endoplasmic reticulum Zhang, M., Yamazaki, T., Yazawa, M., Treves, S., Nishi, M., Murai, M., Shibata, E., Zorzato, F. & Takeshima, H. (Cell Calcium 42, 83-90, 2007)

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.

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