A human CR1-like transcript containing sequence for a binding protein for iC4 is expressed in hematopoietic and fetal lymphoid tissue.
A human CR1-like transcript containing sequence for a binding protein for iC4 is expressed in hematopoietic and fetal lymphoid tissue.
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含有 iC4 结合蛋白序列的人类 CR1 样转录物在造血和胎儿淋巴组织中表达。
DOI：
10.1016/j.molimm.2003.09.010
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发表时间：
2004
影响因子：
3.6
通讯作者：
Birmingham,DanielJ
中科院分区：
文献类型：
--
作者：
Logar,ChristineM;Chen,Wei;Schmitt,Holly;Yu,ChackYung;Birmingham,DanielJ
灵长类动物免疫粘附受体是红细胞补体受体（E-CR），对循环免疫复合物（IC）的清除有积极影响。人类E-CR是一种1型补体受体（CR 1），最常表达为220 kDa蛋白，含有30个短共有重复序列（SCR）。黑猩猩E-CR是由8个SCR组成的75 kDa蛋白质，由人类CR 1-like（CR 1 L）的直系同源物编码，CR 1 L是与CR 1相关的遗传元件。人类CR 1 L先前从预测7个SCR的外显子的基因组克隆中鉴定，并且没有CR 1 L表达的报道。本研究的目的是确定人CR 1 L是否表达。用CR 1/CR 1 L特异性引物扩增人骨髓cDNA，得到与黑猩猩CR 1 L编码序列相似的产物。前6.5个SCR与预测的人类CR 1 L序列100%匹配，而SCR 7的后半部分与可比较的黑猩猩CR 1 L序列同源，但具有终止密码子。在COS-7细胞中的表达产生了约50 kDa的人CR 1 L蛋白，其表现出对iC 4而不是对iC 3的结合特异性。人骨髓的北方或蛋白质印迹分析均未显示CR 1 L转录物或蛋白质的存在。然而，各种其他淋巴组织的北方印迹分析在人胎肝中鉴定了候选CR 1 L转录物。人胎儿组织的cDNA组的PCR扩增证实了CR 1 L转录物在胎儿肝脏中的存在，并且在较小程度上在胎儿脾脏和胸腺中存在。因此，CR 1 L转录本的表达似乎仅限于造血和胎儿淋巴组织。
Primate immune adherence receptors are erythrocyte complement receptors (E-CR) that favorably influence the clearance of circulating immune complexes (IC). The human E-CR is the type one complement receptor (CR1), most commonly expressed as a 220kDa protein containing 30 short consensus repeats (SCRs). The chimpanzee E-CR is a 75kDa protein composed of eight SCRs, and is encoded by an ortholog of human CR1-like (CR1L), a genetic element related to CR1. Human CR1L was previously identified from genomic clones that predict exons for seven SCRs, and there have been no reports of CR1L expression. The purpose of this study was to determine if human CR1L is expressed. Amplification of human bone marrow cDNA using primers specific for CR1/CR1L yielded a product similar to chimp CR1L encoding sequence. The first 6.5 SCRs matched 100% with the predicted human CR1L sequence, while the second half of SCR 7 was homologous to the comparable chimp CR1L sequence but with a stop codon. Expression in COS-7 cells yielded a human CR1L protein of approximately 50kDa that exhibited binding specificity for iC4 but not for iC3. Neither northern nor western blot analysis of human bone marrow revealed the presence of the CR1L transcript or protein. However, northern blot analysis of various other lymphoid tissue identified a candidate CR1L transcript in human fetal liver. PCR amplification of a cDNA panel of human fetal tissue confirmed the presence of the CR1L transcript in fetal liver, and to a lesser extent in fetal spleen and thymus. Thus, expression of the CR1L transcript appears to be limited to hematopoietic and fetal lymphoid tissue.