Cytosolic Phospholipase A2Translocates to Forming Phagosomes during Phagocytosis of Zymosan in Macrophages

Milena Girotti, John H. Evans, Danielle Burke, Christina C. Leslie
2004 Journal of Biological Chemistry  
Resident tissue macrophages mediate early innate immune responses to microbial infection. Cytosolic phospholipase A 2 ␣ (cPLA 2 ␣) is activated in macrophages during phagocytosis of non-opsonized yeast (zymosan) triggering arachidonic acid release and eicosanoid production. cPLA 2 ␣ translocates from cytosol to membrane in response to intracellular calcium concentration ([Ca 2؉ ] i ) increases. Enhanced green fluorescent protein (EGFP)-cPLA 2 ␣ translocated to forming phagosomes, surrounding
more » ... mes, surrounding the zymosan particle by 5 min and completely overlapping with early endosome (Rab5) and plasma membrane (F4/80) markers but only partially overlapping with resident endoplasmic reticulum proteins (GRP78 and cyclooxygenase 2). EGFP-cPLA 2 ␣ also localized to membrane ruffles during phagocytosis. Zymosan induced an initial high amplitude calcium transient that preceded particle uptake followed by a low amplitude sustained calcium increase. Both phases were required for optimal phagocytosis. Extracellular calcium chelation prevented only the sustained phase but allowed a limited number of phagocytic events, which were accompanied by translocation of cPLA 2 ␣ to the phagosome although [Ca 2؉ ] i remained at resting levels. The results demonstrate that cPLA 2 ␣ targets the phagosome membrane, which may serve as a source of arachidonic acid for eicosanoid production.
doi:10.1074/jbc.m313867200 pmid:14963030 fatcat:gny7kzvtczeypopdlozgpcwosu