Focal Exocytosis of VAMP3-Containing Vesicles at Sites of Phagosome Formation

• Published in: The Journal of cell biology Vol. 149; no. 3; pp. 697 - 705
• Main Authors: Bajno, Lydia, Peng, Xiao-Rong, Schreiber, Alan D., Moore, Hsiao-Ping, Trimble, William S., Grinstein, Sergio
• Format: Journal Article
• Language: English
• Published: United States Rockefeller University Press 01.05.2000; The Rockefeller University Press
• Subjects: Animals; Antibodies; Antigens, CD - metabolism; Cell membranes; Cells; Cellular biology; CHO Cells; Cricetinae; Endosomes; Endosomes - metabolism; Exocytosis; Green Fluorescent Proteins; Luminescent Proteins; Lysosomal Membrane Proteins; Membrane Fusion; Membrane Glycoproteins - metabolism; Membrane Proteins - genetics; Membrane Proteins - metabolism; Membranes; Microscopy, Fluorescence; Original; Phagocytes; Phagocytosis; Phagosomes; Phagosomes - metabolism; Pseudopodia - metabolism; Receptors; Receptors, IgG - metabolism; Recombinant Fusion Proteins - metabolism; Recycling; Transfection; Vesicle-Associated Membrane Protein 3
• ISSN: 0021-9525; 1540-8140
• 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.