Involvement of the AP-1 adaptor complex in early steps of phagocytosis and macropinocytosis.

The best described function of the adaptor complex-1 (AP-1) is to participate in the budding of clathrin-coated vesicles from the trans-Golgi network and endosomes. Here, we show that AP-1 is also localized to phagocytic cups in murine macrophages as well as in Dictyostelium amoebae. AP-1 is recruited to phagosomal membranes at this early stage of phagosome formation and rapidly dissociates from maturing phagosomes. To establish the role of AP-1 in phagocytosis, we made used of Dictyostelium mutant cells (apm1(-) cells) disrupted for AP-1 medium chain. In this mutant, phagocytosis drops by 60%, indicating that AP-1 is necessary for efficient phagocytosis. Furthermore, phagocytosis in apm1(-) cells is more affected for large rather than small particles, and cells exhibiting incomplete engulfment are then often observed. This suggests that AP-1 could participate in the extension of the phagocytic cup. Interestingly, macropinocytosis, a process dedicated to fluid-phase endocytosis and related to phagocytosis, is also impaired in apm1(-) cells. In summary, our data suggest a new role of AP-1 at an early stage of phagosome and macropinosome formation.

Citation

Yaya Lefkir, Marilyne Malbouyres, Daniel Gotthardt, Adrian Ozinsky, Sophie Cornillon, Franz Bruckert, Alan A Aderem, Thierry Soldati, Pierre Cosson, François Letourneur. Involvement of the AP-1 adaptor complex in early steps of phagocytosis and macropinocytosis. Molecular biology of the cell. 2004 Feb;15(2):861-9

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PMID: 14617812

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