Laird D W, Molday R S
Department of Biochemistry, University of British Columbia, Canada.
Invest Ophthalmol Vis Sci. 1988 Mar;29(3):419-28.
The possible role of rhodopsin in the binding and phagocytosis of rod outer segments (ROS) by cultured bovine retinal pigment epithelial (RPE) cells was studied using both quantitative phagocytosis assays and electron microscopy. In inhibition studies an immunoaffinity purified 2-39 N-terminal rhodopsin glycopeptide, a synthetic 1-16 peptide analogue of rhodopsin and purified, unsealed ROS disc membranes were found to be ineffective in inhibiting the binding of 125I-labeled ROS to RPE cells. A two-fold excess of unlabeled intact ROS, however, inhibited 125I-labeled ROS binding to RPE cells by over 40%. In another series of experiments, rhodopsin on the surface of fixed ROS was densely labeled with gold-dextran particles conjugated to an N-terminal-specific (rho 4D2) rhodopsin monoclonal antibody or its F(ab')2 fragment in an effort to block binding and phagocytosis by RPE cells. As visualized by both transmission and scanning electron microscopy using secondary and backscatter electron imaging, these antibody-gold-dextran-labeled ROS were effectively phagocytized by RPE cells. These results provide compelling evidence that rhodopsin in the ROS plasma membrane does not function as the ligand for recognition by RPE cells.
利用定量吞噬试验和电子显微镜，研究了视紫红质在培养的牛视网膜色素上皮（RPE）细胞结合和吞噬视杆细胞外段（ROS）中的可能作用。在抑制研究中，发现免疫亲和纯化的2 - 39 N端视紫红质糖肽、视紫红质的合成1 - 16肽类似物以及纯化的、未封闭的ROS盘膜，在抑制125I标记的ROS与RPE细胞的结合方面无效。然而，两倍过量的未标记完整ROS可抑制125I标记的ROS与RPE细胞的结合达40%以上。在另一系列实验中，用与N端特异性（rho 4D2）视紫红质单克隆抗体或其F(ab')2片段偶联的金葡聚糖颗粒对固定ROS表面的视紫红质进行密集标记，以阻断RPE细胞的结合和吞噬。通过透射电子显微镜和扫描电子显微镜利用二次电子成像和背散射电子成像观察到，这些抗体 - 金葡聚糖标记的ROS被RPE细胞有效吞噬。这些结果提供了令人信服的证据，表明ROS质膜中的视紫红质并非作为RPE细胞识别的配体发挥作用。
