Colley N J, Clark V M, Hall M O
Exp Eye Res. 1987 Mar;44(3):377-92. doi: 10.1016/s0014-4835(87)80172-0.
Proteases have been used as a tool to investigate the role of cell-surface molecules of cultured retinal pigment epithelial cells (RPE) in the phagocytosis of rod outer segments (ROS). Proteolytic digestion of RPE cells by pronase, thermolysin and Staphylococcus aureus V8 protease (V8 protease) inhibited the phagocytosis of ROS without affecting the viability of the RPE cells. A particular feature of RPE cell proteolysis was that those macromolecules responsible for ROS ingestion were susceptible, while those macromolecules that mediated ROS binding were resistant to cleavage by all three proteases. By taking advantage of this phenomenon, ROS were used as affinity particles to obtain a plasma membrane-enriched fraction of RPE cells before and after proteolytic digestion. All three proteases partially or completely removed several glycoproteins from the cell surfaces. Removal of these glycoproteins was correlated with a loss in phagocytic ability by RPE cells. Two high-molecular-weight (MW) glycoproteins of MWs 160,000 and 214,000 were consistently removed by all proteases tested. Protease-treated RPE cells restored their phagocytic capabilities and normal glycoprotein composition within 24 hr after proteolytic treatment. These data suggest that glycoproteins located on the surfaces of RPE cells may be involved in mediating the phagocytosis of ROS by these cells.
蛋白酶已被用作一种工具，用于研究培养的视网膜色素上皮细胞（RPE）的细胞表面分子在视杆细胞外段（ROS）吞噬作用中的作用。用链霉蛋白酶、嗜热菌蛋白酶和金黄色葡萄球菌V8蛋白酶（V8蛋白酶）对RPE细胞进行蛋白水解消化，可抑制ROS的吞噬作用，而不影响RPE细胞的活力。RPE细胞蛋白水解的一个特殊特征是，那些负责ROS摄取的大分子易受影响，而那些介导ROS结合的大分子对所有三种蛋白酶的切割具有抗性。利用这一现象，在蛋白水解消化前后，将ROS用作亲和颗粒，以获得RPE细胞富含质膜的部分。所有三种蛋白酶都部分或完全去除了细胞表面的几种糖蛋白。这些糖蛋白的去除与RPE细胞吞噬能力的丧失相关。所有测试的蛋白酶都一致地去除了两种分子量分别为160,000和214,000的高分子量（MW）糖蛋白。经蛋白酶处理的RPE细胞在蛋白水解处理后24小时内恢复了其吞噬能力和正常的糖蛋白组成。这些数据表明，位于RPE细胞表面的糖蛋白可能参与介导这些细胞对ROS的吞噬作用。
