A major endothelial plasmalemmal sialoglycoprotein, gp60, is immunologically related to glycophorin.

Glycophorins, the major sialoglycoproteins of red blood cells in many species, are generally considered to be specific to erythroid cells. Using polyclonal antibodies directed against mouse glycophorin (alpha gp), we have identified a glycoprotein antigenically related to glycophorin on the surface of bovine and rat cultured endothelial cells. Immunoblotting with alpha gp identified a single 60-kDa polypeptide on transfers of SDS/polyacrylamide gels of solubilized confluent endothelial monolayers. In addition, a 60-kDa polypeptide was immunoprecipitated by alpha gp from lysates of 125I-labeled intact endothelial cells. Controls with preimmune serum were negative. This antibody interaction was inhibited by murine erythrocyte ghosts and purified glycophorins. Our past work identified several endothelial surface sialoglycoproteins including a 60-kDa glycoprotein (gp60) that (i) interacts with albumin, (ii) binds Limax flavus, Ricinus communis, and Triticum vulgare agglutinins but not other lectins, (iii) is sequentially precipitated from 125I-labeled cell lysates by using R. communis agglutinin followed by T. vulgare agglutinin, and (iv) is sensitive to sialidase digestion. Immunoblotting of such precipitates with alpha gp demonstrates that lectins recognize the same glycoprotein, namely gp60. These results indicate that gp60, a major endothelial surface sialoglycoprotein, shares antigenic epitope(s) with glycophorin. IMAGES:

血型糖蛋白（glycophorins）是多种物种红细胞的主要唾液酸糖蛋白，通常被认为是红系细胞特异性蛋白。本研究使用针对小鼠α-血型糖蛋白（α gp）的多克隆抗体，在牛和大鼠培养的内皮细胞表面鉴定出了一种与血型糖蛋白抗原相关的糖蛋白。通过对溶解的汇合内皮单层细胞进行十二烷基硫酸钠-聚丙烯酰胺凝胶（SDS/聚丙烯酰胺凝胶）电泳转印，采用α gp进行免疫印迹，可检测到一条单一的60 kDa多肽。此外，从碘-125标记的完整内皮细胞裂解物中，α gp可免疫沉淀出一条60 kDa的多肽。预免疫血清对照组结果为阴性。该抗体结合反应可被小鼠红细胞血影及纯化的血型糖蛋白所抑制。本研究团队既往的研究已鉴定出多种内皮细胞表面唾液酸糖蛋白，其中包括一种60 kDa的糖蛋白（gp60），其具备如下特性：(i) 可与白蛋白结合；(ii) 能结合黄蛞蝓（Limax flavus）、蓖麻（Ricinus communis）及小麦胚芽（Triticum vulgare）凝集素，但不结合其他凝集素；(iii) 可通过先用蓖麻凝集素、再用小麦胚芽凝集素从碘-125标记的细胞裂解物中依次沉淀得到；(iv) 对唾液酸酶消化敏感。对上述凝集素沉淀产物采用α gp进行免疫印迹，结果显示凝集素所识别的为同一种糖蛋白，即gp60。本研究结果表明，作为内皮细胞表面主要唾液酸糖蛋白的gp60，与血型糖蛋白共享抗原表位。图片：