title: Phospholipase A2IVα regulates phagocytosis independent of its enzymatic activity.
abstract: Group IVα phospholipase A(2) (PLA(2)IVα) is a lipolytic enzyme that catalyzes the hydrolysis of membrane phospholipids to generate precursors of potent inflammatory lipid mediators. Here, the role of PLA(2)IVα in Fc receptor (FcR)-mediated phagocytosis was investigated, demonstrating that PLA(2)IVα is selectively activated upon FcR-mediated phagocytosis in macrophages and that it rapidly translocates to the site of the nascent phagosome. Moreover, pharmacological inhibition of PLA(2)IVα by pyrrophenone reduces particle internalization by up to 50%. In parallel, fibroblasts from PLA(2)IVα knock-out mice overexpressing FcγRIIA and able to internalize IgG-opsonized beads show 50% lower phagocytosis, compared with wild-type cells, and transfection of PLA(2)IVα fully recovers this impaired function. Interestingly, transfection of the catalytically inactive deleted PLA(2)IVα mutant (PLA(2)IVα(1-525)) and point mutant (PLA(2)IVα-S228C) also promotes recovery of this impaired function. Finally, transfection of the PLA(2)IVα C2 domain (which is directly involved in PLA(2)IVα membrane binding), but not of PLA(2)IVα-D43N (which cannot bind to membranes), rescues FcR-mediated phagocytosis. These data unveil a new mechanism of action for PLA(2)IVα, which demonstrates that the membrane binding, and not the enzymatic activity, is required for PLA(2)IVα modulation of FcR-mediated phagocytosis.
authors.affiliation: Institute of Protein Biochemistry, National Research Council, Via Pietro Castellino 111, 80131 Naples, Italy.
authors.forename: Pasquale
authors.initials: P
authors.lastname: Zizza
authors.forename: Cristiano
authors.initials: C
authors.lastname: Iurisci
authors.forename: Matteo
authors.initials: M
authors.lastname: Bonazzi
authors.forename: Pascale
authors.initials: P
authors.lastname: Cossart
authors.forename: Christina C
authors.initials: CC
authors.lastname: Leslie
authors.forename: Daniela
authors.initials: D
authors.lastname: Corda
authors.forename: Stefania
authors.initials: S
authors.lastname: Mariggiò
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D002461:Cell Line, Transformed; D002462:Cell Membrane / Q000201:enzymology* / Q000235:genetics; D005347:Fibroblasts / Q000166:cytology / Q000201:enzymology; D054513:Group IV Phospholipases A2 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008264:Macrophages / Q000166:cytology / Q000201:enzymology*; D051379:Mice; D018345:Mice, Knockout; D020125:Mutation, Missense; D010587:Phagocytosis / Q000187:drug effects / Q000502:physiology*; D010588:Phagosomes / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D011759:Pyrrolidines / Q000494:pharmacology; D017452:Receptors, IgG / Q000235:genetics / Q000378:metabolism
chemical_list: C080568:Fc gamma receptor IIA; D011759:Pyrrolidines; D017452:Receptors, IgG; C455981:pyrrophenone; D054513:Group IV Phospholipases A2