Orlando R A, Kerjaschki D, Kurihara H, Biemesderfer D, Farquhar M G
Division of Cellular and Molecular Medicine, University of California, San Diego, La Jolla 92093.
Proc Natl Acad Sci U S A. 1992 Aug 1;89(15):6698-702. doi: 10.1073/pnas.89.15.6698.
Using antibodies isolated from glomeruli of nephritic rats we have previously identified a 330-kDa cell surface glycoprotein (gp330) as a major pathogenic antigen of Heymann nephritis (HN), an experimental model of human membranous glomerulonephritis. Recently, we have isolated a cDNA clone, C14, encoding a polypeptide that contains a pathogenic epitope of HN responsible for the initiation of the disease. Subsequently, another protein, alpha 2-macroglobulin receptor-associated protein (alpha 2-MRAP), which is a subunit of the receptor for human alpha 2-macroglobulin/low density lipoprotein receptor-related protein (LRP), was shown to possess a high degree of sequence homology to the C14 protein (C14p). In this report, we have investigated the relationship between gp330, C14p, and alpha 2-MRAP. Immunoprecipitation studies demonstrate that gp330 forms a heterodimeric association with a 44-kDa polypeptide that is stable to detergent extraction and long-term centrifugation. Further, immunoblotting analysis on the purified complex indicates that the 44-kDa associated protein shares immunological identity to C14p and alpha 2-MRAP. In addition, antibodies eluted from glomeruli of HN rats and antibodies to a C14 fusion protein immunoprecipitated gp330 and the 44-kDa protein, demonstrating that the epitopes responsible for the initial events of HN are accessible within the complex. Based on these data, three models are proposed to explain how pathogenic epitopes in the gp330-44-kDa, HN antigenic complex may be presented at the cell surface and initiate the onset of HN.
利用从患肾炎大鼠肾小球中分离出的抗体，我们先前已鉴定出一种330 kDa的细胞表面糖蛋白（gp330）是海曼肾炎（HN）的主要致病抗原，HN是人类膜性肾小球肾炎的一种实验模型。最近，我们分离出了一个cDNA克隆C14，它编码一种含有引发该疾病的HN致病表位的多肽。随后，另一种蛋白质，α2-巨球蛋白受体相关蛋白（α2-MRAP），它是人类α2-巨球蛋白/低密度脂蛋白受体相关蛋白（LRP）受体的一个亚基，被证明与C14蛋白（C14p）具有高度的序列同源性。在本报告中，我们研究了gp330、C14p和α2-MRAP之间的关系。免疫沉淀研究表明，gp330与一种44 kDa的多肽形成异二聚体结合，这种结合对去污剂提取和长期离心稳定。此外，对纯化复合物的免疫印迹分析表明，这种44 kDa的相关蛋白与C14p和α2-MRAP具有免疫同一性。此外，从HN大鼠肾小球洗脱的抗体和针对C14融合蛋白的抗体免疫沉淀了gp33 和44 kDa的蛋白，表明在复合物中可获得负责HN初始事件的表位。基于这些数据，提出了三种模型来解释gp330 - 44 kDa的HN抗原复合物中的致病表位如何在细胞表面呈现并引发HN的发病。
