title: Fc receptor isoforms exhibit distinct abilities for coated pit localization as a result of cytoplasmic domain heterogeneity.
abstract: Mouse macrophages and lymphocytes express two distinct isoforms of a single class of Fc receptor for IgG. The macrophage isoform (FcRII-B2) is identical to the lymphocyte isoform (FcRII-B1) except for an inframe insertion in the cytoplasmic tail of FcRII-B1 that increases its length from 47 to 94 amino acids. To determine the functional significance of this cytoplasmic domain variation, presumably the result of alternative mRNA splicing, we expressed both isoforms in receptor-negative fibroblasts. While FcRII-B2 mediated the efficient ligand internalization and delivery to lysosomes, endocytosis via FcRII-B1--and via a tailminus mutant--was relatively inefficient. This difference reflected the inability of FcRII-B1 (and the tailminus mutant) to accumulate in clathrin-coated pits. Thus, the FcRII-B2 cytoplasmic tail contains a domain needed for accumulation in coated pits, and this domain is disrupted by the 47 amino acid insertion in FcRII-B1.
authors.affiliation: Department of Pathology, Yale University School of Medicine, New Haven, Connecticut 06510.
authors.forename: H M
authors.initials: HM
authors.lastname: Miettinen
authors.forename: J K
authors.initials: JK
authors.lastname: Rose
authors.forename: I
authors.initials: I
authors.lastname: Mellman
mesh_terms: D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000032:analysis / Q000648:ultrastructure; D002478:Cells, Cultured; D003034:Coated Pits, Cell-Membrane / Q000032:analysis*; D006224:Cricetinae; D003412:Cricetulus; D003593:Cytoplasm / Q000032:analysis*; D004705:Endocytosis; D011992:Endosomes / Q000032:analysis*; D007074:Immunoglobulin G / Q000032:analysis; D008214:Lymphocytes / Q000166:cytology / Q000502:physiology / Q000648:ultrastructure; D008264:Macrophages / Q000166:cytology / Q000502:physiology / Q000648:ultrastructure; D051379:Mice; D009865:Oocytes / Q000378:metabolism / Q000502:physiology / Q000648:ultrastructure; D011961:Receptors, Fc / Q000032:analysis* / Q000378:metabolism / Q000502:physiology; D014162:Transfection
chemical_list: D007074:Immunoglobulin G; D011961:Receptors, Fc