Allen L A, Aderem A
Laboratory of Signal Transduction, Rockefeller University, New York, NY 10021, USA.
J Exp Med. 1996 Aug 1;184(2):627-37. doi: 10.1084/jem.184.2.627.
It has long been known from the results of ultrastructural studies that complement- and immunoglobulin G (IgG)-opsonized particles are phagocytosed differently by macrophages (Kaplan. G. 1977. Scand. J. Immunol. 6:797-807). Complement-opsonized particles sink into the cell, whereas IgG-coated particles are engulfed by lamellipodia, which project from the cell surface. The molecular basis for these differences is unknown. We used indirect immunofluorescence and confocal microscopy to examine how cytoskeletal proteins associate with phagosomes containing complement-opsonized zymosan (COZ) particles or IgG beads in phorbol-myristateacetate-treated peritoneal macrophages. During ingestion of COZ, punctate structures rich in F-actin, vinculin, alpha-actinin, paxillin, and phosphotyrosine-containing proteins are distributed over the phagosome surface. These foci are detected beneath bound COZ within 30 s of warming the cells to 37 degrees C, and their formation requires active protein kinase C. By contrast, during Fc receptor-mediated phagocytosis, all proteins examined were uniformly distributed on or near the phagosome surface. Moreover, ingestion of IgG beads was blocked by tyrosine kinase inhibitors, whereas phagocytosis of COZ was not. Thus, the signals required for particle ingestion, and the arrangement of cytoskeletal proteins on the phagosome surface, vary depending upon which phagocytic receptor is engaged. Moreover, complement receptor (CR)-mediated internalization required intact microtubules and was accompanied by the accumulation of vesicles beneath the forming phagosome, suggesting that membrane trafficking plays a key role in CR-mediated phagocytosis.
长期以来，超微结构研究结果表明，补体和免疫球蛋白G（IgG）调理的颗粒被巨噬细胞吞噬的方式不同（卡普兰，G. 1977年。《斯堪的纳维亚免疫学杂志》6:797 - 807）。补体调理的颗粒沉入细胞内，而IgG包被的颗粒则被从细胞表面伸出的片状伪足吞噬。这些差异的分子基础尚不清楚。我们使用间接免疫荧光和共聚焦显微镜来研究细胞骨架蛋白如何与佛波酯 - 肉豆蔻酸乙酸酯处理的腹膜巨噬细胞中含有补体调理的酵母聚糖（COZ）颗粒或IgG珠子的吞噬体相关联。在摄取COZ的过程中，富含F - 肌动蛋白、纽蛋白、α - 辅肌动蛋白、桩蛋白和含磷酸酪氨酸蛋白的点状结构分布在吞噬体表面。在将细胞加热至37摄氏度后30秒内，这些焦点在结合的COZ下方被检测到，并且它们的形成需要活性蛋白激酶C。相比之下，在Fc受体介导的吞噬作用过程中，所有检测的蛋白质均匀地分布在吞噬体表面或其附近。此外，IgG珠子的摄取被酪氨酸激酶抑制剂阻断，而COZ的吞噬作用则不受影响。因此，颗粒摄取所需的信号以及细胞骨架蛋白在吞噬体表面的排列，取决于所参与的吞噬受体而有所不同。此外，补体受体（CR）介导的内化需要完整的微管，并伴随着在形成的吞噬体下方囊泡的积累，这表明膜运输在CR介导的吞噬作用中起关键作用。
