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Golgi-associated PKC-? is delivered to phagocytic cups: Role of PI4P1 #MMPMID28539432
Hanes CM; D'Amico AE; Ueyama T; Wong AC; Zhang X; Hynes WF; Barroso MM; Cady NC; Trebak M; Saito N; Lennartz MR
J Immunol 2017[Jul]; 199 (1): 271-7 PMID28539432show ga
PKC-? concentration at phagocytic cups mediates the membrane fusion necessary for efficient IgG-mediated phagocytosis. The C1B and pseudosubstrate (?PS) domains are necessary and sufficient for this concentration. C1B binds diacylglycerol; the docking partner for ?PS is unknown. Liposome assays revealed that the ?PS binds phosphatidylinositol 4-phosphate (PI4P) and PI(3,5)P2. Wortmannin, but not LY294002, inhibits PKC-? concentration at cups and significantly reduces the rate of phagocytosis. As Wortmannin inhibits PI4 kinase, we hypothesized that PI4P mediates the PKC-? concentration at cups and the rate of phagocytosis. PKC-? co-localizes with the Trans Golgi network PI4P reporter the P4M, suggesting its' tethering at the TGN. Real time imaging of GFP-PKC-? expressing macrophages revealed a loss of Golgi-associated PKC-? during phagocytosis, consistent with a Golgi-to-phagosome translocation. Treatment with PIK93, a PI4K inhibitor, reduces PKC-? at both the TGN and the cup, decreases phagocytosis, and prevents the increase in capacitance that accompanies membrane fusion. Finally, expression of the Golgi-directed PI4P phosphatase, hSac1-K2A, recapitulates the PIK93 phenotype, confirming that Golgi-associated PI4P is critical for efficient phagocytosis. Together these data are consistent with a model in which PKC-? is tethered to the TGN via an ?PS-PI4P interaction. The TGN-associated pool of PKC-? concentrates at the phagocytic cup where it mediates the membrane fusion necessary for phagocytosis. The novelty of these data lies in the demonstration that ?PS binds PI4P and PI(3,5)P2 and that PI4P is necessary for PKC-? localization at the TGN, its translocation to the phagocytic cup, and the membrane fusion required for efficient Fc?R-mediated phagocytosis.