Group V secretory phospholipase A2 translocates to the phagosome after zymosan stimulation of mouse peritoneal macrophages and regulates phagocytosis

We have previously reported that group V secretory phospholipase A(2) (sPLA(2)) amplifies the action of cytosolic phospholipase A2 (cPLA(2)) alpha in regulating eicosanoid biosynthesis by mouse peritoneal macrophages stimulated with zymosan (Satake, Y., Diaz, B. L., Balestrieri, B., Lam, B. K., Kanaoka, Y., Grusby, M. J., and Arm, J. P. ( 2004) J. Biol. Chem. 279, 16488 - 16494). To further understand the role of group V sPLA2, we studied its localization in resting mouse peritoneal macrophages before and after stimulation with zymosan and the effect of deletion of the gene encoding group V sPLA2 on phagocytosis of zymosan. We report that group V sPLA2 is present in the Golgi apparatus and recycling endosome in the juxtanuclear region of resting peritoneal macrophages. Upon ingestion of zymosan by mouse peritoneal macrophages, group V sPLA(2) is recruited to the phagosome. There it co-localizes with cPLA(2) alpha, 5-lipoxygenase, 5-lipoxygenase-activating protein, and leukotriene C-4 synthase. Using immunostaining for the cysteinyl leukotrienes in carbodiimide-fixed cells, we show, for the first time, that the phagosome is a site of cysteinyl leukotriene formation. Furthermore, peritoneal macrophages from group V sPLA(2)-null mice demonstrated a> 50% attenuation in phagocytosis of zymosan particles, which was restored by adenoviral expression of group V sPLA(2) but not group IIA sPLA(2). These data demonstrate that group V sPLA(2) contributes to the innate immune response both through regulation of eicosanoid generation in response to a phagocytic stimulus and also as a component of the phagocytic machinery.