Group V Secretory Phospholipase A2 Modulates Phagosome Maturation and Regulates the Innate Immune Response Against Candida albicans1

Phospholipase A(2) (PLA(2)) hydrolyzes the sn-2 position of cell membrane phospholipids to release fatty acids and lysophospholipids. We have previously reported that group V secretory PLA(2) (sPLA(2)) translocates from the Golgi and recycling endosomes of mouse peritoneal macrophages to newly formed phagosomes and regulates the phagocytosis of zymosan, suggesting a role in innate immunity. Here we report that in macrophages lacking group V sPLA(2), phagosome maturation was reduced 50-60% at early time points while the binding of zymosan was unimpaired. The ability of group V sPLA(2) to regulate phagocytosis extended to phagocytosis of IgG- and complement-opsonized sheep RBC. Moreover, macrophages lacking group V sPLA(2) had delays in phagocytosis, phagosome maturation, and killing of Candida albicans. Cytokine production and eicosanoid generation were not impaired by the lack of group V sPLA(2). Furthermore, in a model of systemic candidiasis, mice lacking group V sPLA(2) had an increased fungal burden in the kidney, liver, and spleen at day 7 postinfection and increased mortality. Thus, group V sPLA(2) regulates phagocytosis through major phagocytic receptors and contributes to the innate immune response against C. albicans by regulating phagocytosis and killing through a mechanism that is likely dependent on phagolysosome fusion.