Cowland Jack B, Carter Daniel, Bjerregaard Malene D, Johnsen Anders H, Borregaard Niels, Lollike Karsten
Department of Hematology, Rigshospitalet, Copenhagen, Denmark.
J Leukoc Biol. 2003 Sep;74(3):379-88. doi: 10.1189/jlb.0203083.
Copines are a recently identified group of proteins characterized by two Ca(2+)-binding C2-domains at the N terminus and an A-domain at the C terminus. Although pEST sequences indicate the existence of at least seven copines in man, only copines I, III, and VI have been identified at protein level. Here, we describe the isolation of copines I and III in the cytosol of human neutrophils by use of Ca(2+)-induced hydrophobic chromatography. This is the first demonstration that copines are coexpressed in the same cell. We found that copine III exists in the cytosol of human neutrophils as a monomer with a blocked N terminus. Copines I and III undergo conformational changes upon Ca(2+) binding that lead to exposure of hydrophobic patches. Examination of RNA from 68 human tissues demonstrated that copines I-III are ubiquitously expressed whereas copines IV-VII each has a more restricted and individual expression profile. Expression of copines I-III was also demonstrated in neutrophil precursors from bone marrow. Copine I was uniformly expressed at all stages of neutrophil differentiation, whereas copine II and even more so, copine III were expressed in the more immature neutrophil precursors, which indicates an individual function of these copines.
伴侣蛋白是最近发现的一类蛋白质，其特征是在N端有两个Ca(2+)结合C2结构域，在C端有一个A结构域。尽管pEST序列表明人类中至少存在七种伴侣蛋白，但在蛋白质水平上仅鉴定出伴侣蛋白I、III和VI。在此，我们描述了利用Ca(2+)诱导的疏水色谱法从人中性粒细胞胞质溶胶中分离伴侣蛋白I和III的方法。这是首次证明伴侣蛋白在同一细胞中共表达。我们发现伴侣蛋白III以N端封闭的单体形式存在于人中性粒细胞的胞质溶胶中。伴侣蛋白I和III在结合Ca(2+)后会发生构象变化，导致疏水区域暴露。对68个人类组织的RNA检测表明，伴侣蛋白I - III广泛表达，而伴侣蛋白IV - VII各有更局限且独特的表达谱。伴侣蛋白I - III在骨髓中性粒细胞前体中也有表达。伴侣蛋白I在中性粒细胞分化的所有阶段均均匀表达，而伴侣蛋白II，尤其是伴侣蛋白III在更不成熟的中性粒细胞前体中表达，这表明这些伴侣蛋白具有独特的功能。
