title: Differences in endocytosis mediated by FcγRIIA and FcγRIIB2.
abstract: An important function of Fcγ receptors is the removal of IgG-containing immune complexes from the circulation. The activating receptor FcγRIIA and inhibitory receptor FcγRIIB2 are both expressed on human myeloid cells, and are both capable of mediating endocytosis of immune complexes. We studied endocytosis of these two receptors expressed by transfection in ts20 Chinese hamster fibroblasts. We find that while FcγRIIA-mediated endocytosis requires the participation of the ubiquitin-conjugating system, the endocytosis of FcγRIIB2 does not. Little if any ubiquitylation of FcγRIIB2 was observed in response to immune complex binding. FcγRIIB2 mediates internalization of immune complexes at a faster rate than FcγRIIA, and facilitates the endocytosis of FcγRIIA upon co-engagement of both receptors. This may represent a novel mechanism by which the inhibitory receptor can reduce signalling from the activating Fcγ receptor.
authors.affiliation: Department of Immunology, University of Toronto, Toronto, Ontario, Canada M5S 1A8.
authors.forename: Christine Y
authors.initials: CY
authors.lastname: Zhang
authors.forename: James W
authors.initials: JW
authors.lastname: Booth
mesh_terms: D000818:Animals; D000936:Antigen-Antibody Complex / Q000378:metabolism; D015153:Blotting, Western; D006224:Cricetinae; D003412:Cricetulus; D004705:Endocytosis / Q000502:physiology*; D006801:Humans; D047468:Immunoprecipitation; D008856:Microscopy, Fluorescence; D017452:Receptors, IgG / Q000378:metabolism*; D014162:Transfection; D054875:Ubiquitination
chemical_list: D000936:Antigen-Antibody Complex; C080568:Fc gamma receptor IIA; C080571:Fc gamma receptor IIB; D017452:Receptors, IgG