The Mac-2 antigen is a galactose-specific lectin that binds IgE.
The Mac-2 antigen is a galactose-specific lectin that binds IgE.
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DOI：
10.1084/jem.170.6.1959
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发表时间：
1989-12-01
期刊：
影响因子：
--
通讯作者：
Pillai S
中科院分区：
文献类型：
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作者：
Cherayil BJ;Weiner SJ;Pillai S
编码Mac-2抗原的基因已通过免疫筛选获得克隆。Mac-2抗原是由硫代乙醇酸诱导的巨噬细胞高表达的一种表面标志。该基因的核苷酸序列与碳水化合物结合蛋白35的核苷酸序列相同，后者是一种在成纤维细胞中发现的半乳糖特异性凝集素，与嗜碱性白血病细胞中的大鼠IgE结合蛋白高度同源。体外合成的Mac-2蛋白显示出预期的碳水化合物和IgE结合特性。通过脉冲追逐分析和亚细胞分级研究，发现Mac-2蛋白存在于胞浆中，但也可在细胞外培养基中积累。考虑到该基因不编码信号肽或跨膜结构域，后一项发现令人惊讶。还发现了一个选择性剪接的cDNA，它可能编码一个NH2末端延伸的Mac-2蛋白，在其NH2末端有一段疏水氨基酸，但尚不清楚它是否是细胞外Mac-2的来源。基于其凝集素和IgE结合特性，讨论了Mac-2蛋白的可能功能。
A cDNA encoding the Mac-2 antigen, a surface marker highly expressed by thioglycollate-elicited macrophages, has been cloned by immunoscreening of a lambda gt11-P388D1 expression library. The nucleotide sequence of the cDNA is identical to that of carbohydrate-binding protein 35, a galactose-specific lectin found in fibroblasts and highly homologous to a rat IgE-binding protein from basophilic leukemia cells. The in vitro synthesized Mac-2 protein displayed the expected carbohydrate- and IgE- binding properties. By pulse-chase analysis and subcellular fractionation studies, the Mac-2 protein was found in the cytosol but was also seen to accumulate in the extracellular medium. The latter finding was surprising in view of the fact that the cDNA did not encode a signal peptide or transmembrane domain. An alternatively spliced cDNA with the potential to encode a NH2 terminally extended Mac-2 protein with a stretch of hydrophobic amino acids at its NH2 terminus was also found, but it is not clear whether it is the source of the extracellular Mac-2. Possible functions for the Mac-2 protein based on its lectin- and IgE-binding properties are discussed.