Regulation of FcgammaR-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...

Macrophages phagocytose particles to resolve infections and remove apoptotic cells. Phosphoinositide 3-kinase generates phosphatidylinositol-3,4,5-trisphosphate (PtdIns(3,4,5)P3) which is restricted to the phagocytic cup, promoting phagocytosis. The PtdIns(3,4,5)P3 5-phosphatase (5-ptase) SHIP1 inhibits phagocytosis. We report here another PtdIns(3,4,5)P3-5-ptase, the 72 kDa-5-phosphatase (72-5ptase), inhibits FcgammaR but not complement-receptor 3 (CR3)-mediated phagocytosis, affecting pseudopod extension and phagosome closure. siRNA knock-down of the 72-5ptase increased FcgammaR but not CR3-stimulated phagocytosis. In contrast SHIP1 inhibited FcgammaR and CR3-phagocytosis with greater effects on CR3-stimulated phagocytosis. The 72-5ptase and SHIP1 were both dynamically recruited to FcgammaR-stimulated phagocytic cups, but only SHIP1 was recruited to the cup in response to complement. To determine if 5-ptases focally degrade PtdIns(3,4,5)P3 at the phagocytic cup following specific stimuli, time-lapse imaging of specific biosensors was performed. Transfection of dominant-negative 72-5ptase, or 72-5ptase siRNA resulted in amplified and prolonged PtdIns(3,4,5)P3 at the phagocytic cup, in response to FcgammaR but not CR3 activation. In contrast macrophages from SHIP1(-/-)/AktPH-GFP transgenic mice exhibited increased and sustained PtdIns(3,4,5)P3 at the cup in response to CR3 activation, with minimal changes to FcgammaR activation. Therefore 72-5ptase and SHIP1 exhibit specificity in regulating FcgammaR versus CR3-stimulated phagocytosis by controlling the amplitude and duration of PtdIns(3,4,5)P3 at the phagocytic cup.