Physiological function and pathological significance of 4F2 antigen.

4F2抗原表达在癌细胞和活化的淋巴细胞等增殖细胞的膜上。虽然它是一种由重链和轻链组成的杂二聚体蛋白，但其轻链结构尚不清楚。根据AAS测序分析，该轻链与hnRNP A2/B1(异质性核核糖核蛋白A2/B1)蛋白具有同源性。本研究的目的是阐明4F2抗原的分子结构和功能，特别是其轻下巴的分子结构和功能及其病理意义。首先，为了鉴定轻链，我们构建了标记的hnRNP A2和B1蛋白的cDNA，并将其导入培养的细胞中，证明4F2抗原中只有hnRNP B1蛋白。我们制备了一种针对hnRNP B1的单抗。抗体分析表明，4F2轻链是修饰的hnRNP B1或其另一种异构体。进一步的研究发现：1)hnRNP B1蛋白是后过渡修饰的，即磷酸化的；2)ITS表达在某些细胞的细胞膜上，尽管它主要定位于细胞核；3)它在还原条件下从重链上解离。它的表达受细胞特异性调控，其剪接异构体可能存在于皮肤和睾丸中。由于有报道称SLE等自身免疫性疾病患者存在针对hnRNP A2/B1蛋白的抗体，我们还利用自身免疫病模型小鼠检测了4F2轻链的流变学意义。抗hnRNP A2/B1抗体可能参与了新西兰B/W小鼠肾脏损害的发病过程，而对MRL-LPR/LPR小鼠无明显影响。我们正在进行实验来分析它。

4F2 antigen is expressed on the membrane of proliferating cells such as cancer cells and activated lymphocytes. Although it is a hetrodimer protein composed of heavy and light chains, the structure of its light chain is still unknown. According to the AAs sequencing analysis, the light chain had a homology to hnRNP A2/B1 (heterogeneous nuclear ribonucleoprotein A2/B1) proteins. The purpose of this study is to clarify the molecular structure and function of 4F2 antigen, especially of its light chin, and its pathological significance.First, in order to identify the light chain, we constructed tagged cDNA of hnRNP A2 and B1 proteins, and transfected them in cultured cells, and demonstrated that only the hnRNP B1 protein was incorporated in the 4F2 antigen. We generated a monoclonal antibody specific to hnRNP B1. The analysis using the antibody indicated that 4F2 light chain was whether modified hnRNP B1 or its another isofrom. Further investigation revealed the followings ; 1) hnRNP B1 protein was post-transitionally modified, that is, phosphorylated, 2) its was expressed on the cell membrane of some kind of cells though it was mainly localized in the nucleus, 3) it was dissociated from the heavy chain under reduced condition. Its expression was cell-specifically regulated and its splcing-isoforms possibly exist in the skin and testis.Because its was reported that the patient of auto-immune disease like SLE had antibodies against hnRNP A2/B1 proteins, we also examined the pahological significance of 4F2 light chain using model mice of autoimmune disease. Anti-hnRNP A2/B1 anitbodies possibly participate in the pathogenesis of renal lesion of Newzealand-B/W mice but not in MRL-lpr/lpr mice. We are carring forward the experiment to analyze it.