Cytoglobin is a respiratory protein in connective tissue and neurons, which is up-regulated by hypoxia
Cytoglobin is a respiratory protein in connective tissue and neurons, which is up-regulated by hypoxia
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DOI：
10.1074/jbc.m310540200
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发表时间：
2004-02-27
影响因子：
4.8
通讯作者：
Burmester, T
中科院分区：
文献类型：
--
作者：
Schmidt, M;Gerlach, F;Burmester, T
细胞红蛋白是最近发现的一种与肌红蛋白有远亲关系的脊椎动物球蛋白，其功能尚不清楚。在这里，我们首次详细分析了细胞珠蛋白的分布和表达。 Northern 和 Western 印迹实验表明细胞珠蛋白 mRNA 和蛋白质存在于广泛的组织中。定量 PCR 表明，在缺氧条件下（9% 氧气 22 小时和 44 小时），大鼠心脏和肝脏中细胞珠蛋白 mRNA 水平上调。使用针对该蛋白质不同表位的三种抗体进行的免疫荧光研究一致显示结缔组织成纤维细胞以及肝星状细胞中存在细胞珠蛋白。细胞珠蛋白也存在于成软骨细胞和成骨细胞中，并且在分化为软骨细胞和骨细胞时表现出表达水平降低。细胞珠蛋白位于这些细胞类型的细胞质中。最近提出的反对细胞珠蛋白完全核定位的证据也通过使用绿色荧光蛋白融合构建体的转染测定提供，这表明不存在活跃的核输入。细胞珠蛋白的差异表达与该分子的一般呼吸功能相矛盾，而是表明了结缔组织特异性功能。我们假设细胞珠蛋白可能参与胶原蛋白的合成。在中枢和周围神经系统的一些神经元亚群中也观察到细胞珠蛋白表达。令人惊讶的是，细胞珠蛋白定位于神经元的细胞质和细胞核中，表明该蛋白质在神经元组织中可能具有额外的作用。
Cytoglobin is a recently discovered vertebrate globin distantly related to myoglobin, and its function is unknown. Here we present the first detailed analysis of the distribution and expression of cytoglobin. Northern and Western blotting experiments show the presence of cytoglobin mRNA and protein in a broad range of tissues. Quantitative PCR demonstrates an up-regulation of cytoglobin mRNA levels in rat heart and liver under hypoxic conditions (22 and 44 h of 9% oxygen). Immunofluorescence studies with three antibodies directed against different epitopes of the protein consistently show cytoglobin in connective tissue fibroblasts as well as in hepatic stellate cells. Cytoglobin is also present in chondroblasts and osteoblasts and shows a decreased level of expression upon differentiation to chondrocytes and osteocytes. Cytoglobin is located in the cytoplasm of these cell types. Evidence against an exclusively nuclear localization of cytoglobin, as recently proposed, is also provided by transfection assays with green fluorescent protein fusion constructs, which demonstrates the absence of an active nuclear import. The differential expression of cytoglobin argues against a general respiratory function of this molecule, but rather indicates a connective tissue-specific function. We hypothesize that cytoglobin may be involved in collagen synthesis. Cytoglobin expression was also observed in some neuronal subpopulations of the central and the peripheral nervous systems. Surprisingly, cytoglobin is localized in both the cytoplasm and nucleus of neurons, indicating a possible additional role of this protein in neuronal tissues.