Bajno L, Peng X R, Schreiber A D, Moore H P, Trimble W S, Grinstein S
Cell Biology Programme, Research Institute, The Hospital for Sick Children and Department of Biochemistry, University of Toronto, Toronto, M5G 1X8 Ontario, Canada.
J Cell Biol. 2000 May 1;149(3):697-706. doi: 10.1083/jcb.149.3.697.
Phagocytosis involves the receptor-mediated extension of plasmalemmal protrusions, called pseudopods, which fuse at their tip to engulf a particle. Actin polymerizes under the nascent phagosome and may propel the protrusion of pseudopods. Alternatively, membrane extension could result from the localized insertion of intracellular membranes into the plasmalemma next to the particle. Here we show focal accumulation of VAMP3-containing vesicles, likely derived from recycling endosomes, in the vicinity of the nascent phagosome. Using green fluorescent protein (GFP) as both a fluorescent indicator and an exofacial epitope tag, we show that polarized fusion of VAMP3 vesicles precedes phagosome sealing. It is therefore likely that targeted delivery of endomembranes contributes to the elongation of pseudopods. In addition to mediating pseudopod formation, receptor-triggered focal secretion of endosomes may contribute to polarized membrane extension in processes such as lamellipodial elongation or chemotaxis.
吞噬作用涉及受体介导的质膜突起（称为伪足）的延伸，伪足在其尖端融合以吞噬颗粒。肌动蛋白在新生吞噬体下聚合，并可能推动伪足的突出。或者，膜的延伸可能是由于细胞内膜在颗粒旁边局部插入质膜所致。在这里，我们展示了含VAMP3的囊泡（可能源自回收内体）在新生吞噬体附近的局部积累。使用绿色荧光蛋白（GFP）作为荧光指示剂和外表面表位标签，我们表明VAMP3囊泡的极化融合先于吞噬体的封闭。因此，内膜的靶向递送可能有助于伪足的伸长。除了介导伪足形成外，受体触发的内体局部分泌可能在诸如片状伪足伸长或趋化作用等过程中促进极化膜的延伸。
