TY - JOUR
T1 - Cytosolic Phospholipase A2 Translocates to Forming Phagosomes during Phagocytosis of Zymosan in Macrophages
AU - Girotti, Milena
AU - Evans, John H.
AU - Burke, Danielle
AU - Leslie, Christina C.
PY - 2004/4/30
Y1 - 2004/4/30
N2 - Resident tissue macrophages mediate early innate immune responses to microbial infection. Cytosolic phospholipase A2α (cPLA 2α) is activated in macrophages during phagocytosis of non-opsonized yeast (zymosan) triggering arachidonic acid release and eicosanoid production. cPLA2α translocates from cytosol to membrane in response to intracellular calcium concentration ([Ca 2+]i) increases. Enhanced green fluorescent protein (EGFP)-cPLA2α translocated to forming phagosomes, 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-cPLA2α 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 2α to the phagosome although [Ca2+]i, remained at resting levels. The results demonstrate that cPLA 2α targets the phagosome membrane, which may serve as a source of arachidonic acid for eicosanoid production.
AB - Resident tissue macrophages mediate early innate immune responses to microbial infection. Cytosolic phospholipase A2α (cPLA 2α) is activated in macrophages during phagocytosis of non-opsonized yeast (zymosan) triggering arachidonic acid release and eicosanoid production. cPLA2α translocates from cytosol to membrane in response to intracellular calcium concentration ([Ca 2+]i) increases. Enhanced green fluorescent protein (EGFP)-cPLA2α translocated to forming phagosomes, 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-cPLA2α 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 2α to the phagosome although [Ca2+]i, remained at resting levels. The results demonstrate that cPLA 2α targets the phagosome membrane, which may serve as a source of arachidonic acid for eicosanoid production.
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U2 - 10.1074/jbc.M313867200
DO - 10.1074/jbc.M313867200
M3 - Article
C2 - 14963030
AN - SCOPUS:2442515338
SN - 0021-9258
VL - 279
SP - 19113
EP - 19121
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 18
ER -