Regulation of FcγR-stimulated phagocytosis by the 72-kDa inositol polyphosphate 5-phosphatase:: SHIP1, but not the 72-kDa 5-phosphatase, regulates complement receptor 3-mediated phagocytosis by differential recruitment of these 5-phosphatases to the phagocytic cup

Macrophages phagocytose particles to resolve infections and remove apoptotic cells. Phosphoinositide 3-kinase generates phosphatidylinositol-3,4,5-trisphosphate [PtdIns(3,4,5)P-3] is restricted to the phagocytic cup, promoting phagocytosis. The PtdIns(3,4,5)P-3 5-phosphatase (5-ptase) Src homology 2 (SH2) domain-containing inositol-5-phosphatase 1 (SHIP1) inhibits phagocytosis. We report here that another PtdIns(3,4,5)P-3-5-ptase, the 72-kDa-5-phosphatase (72-5ptase), inhibits Fc gamma receptor (Fc gamma R)- but not complement receptor 3 (CR3)-mediated phagocytosis, affecting pseudopod extension and phagosome closure. In contrast, SHIP1 inhibited Fc gamma R and CR3 phagocytosis with greater effects on CR3-stimulated phagocytosis. The 72-5ptase and SHIP1 were both dynamically recruited to Fc gamma R-stimulated phagocytic cups, but only SHIP1 was recruited to CR3-stimulated phagocytic cups. To determine whether 5-ptases focally degrade PtdIns(3,4,5)P-3 at the phagocytic cup after specific stimuli, time-lapse imaging of specific biosensors was performed. Transfection of dominant-negative 72-5ptase or 72-5ptase small interfering RNA (siRNA) resulted in amplified and prolonged PtdIns(3,4,5)P-3 at the phagocytic cup in response to Fc-yR- but not CR3-stimulation. In contrast, macrophages from Ship1(-/-)/AktPH-GFP transgenic mice exhibited increased and sustained PtdIns(3,4,5)P-3 at the cup in response to CR3 activation, with minimal changes to Fc gamma R activation. Therefore, 72-5ptase and SHIP1 exhibit specificity in regulating Fc-yR- versus CR3-stimulated phagocytosis by controlling the amplitude and duration of PtdIns(3,4,5)P-3 at the phagocytic cup.