title: Fc receptor gamma chain residues at the interface of the cytoplasmic and transmembrane domains affect association with FcalphaRI, surface expression, and function.
abstract: The assembly of multiple subunit immunoreceptors is dependent on transmembrane interactions. The Fc receptor gamma (FcR-gamma) chain is a ubiquitous immune receptor tyrosine-based activation motif-containing dimeric subunit, gamma(2), which in humans associates with both the activating members of the leukocyte receptor cluster, including the IgA receptor FcalphaRI, and the classical Fc receptors, including the IgE receptor FcepsilonRI. This study identifies a new site in the transmembrane region of FcR-gamma that affects receptor assembly and surface expression with FcalphaRI but not with FcepsilonRI. The wild type complex, FcalphaRI-gamma(2)WT, remains robustly associated in both Brij-96 and Thesit detergent conditions. However, mutation of either Tyr(25) or Cys(26) of FcR-gamma, near the interface of the transmembrane and cytoplasmic regions, resulted in impaired FcR-gamma association with FcalphaRI. This association was disrupted in the presence of the detergent Brij-96 but was preserved in milder conditions using the detergent Thesit. Ligand-mediated cross-linking of the FcalphaRI-gamma(2)Y25F mutant receptor resulted in diminished signal transduction, including an abnormal calcium response, compared with the FcalphaRI-gamma(2)WT receptor. Furthermore, the FcalphaRI-gamma(2)Y25F mutant receptor was expressed at the cell surface at approximately 10% of that of the wild type, whereas the surface expression of FcepsilonRI-gamma(2)Y25F was not significantly different from the wild type. In contrast, although the FcalphaRI-gamma(2)C26S mutant was also less stably associated, it was not reduced in surface expression or function. Thus, these TM residues of FcR-gamma are important for association with FcalphaRI and probably other activating LRC members but not with the classical FcR, FcepsilonRI.
authors.affiliation: Helen Macpherson Smith Trust Inflammatory Disease Laboratory, Austin Research Institute, Austin Repatriation Medical Centre, Studley Road, Heidelberg, Victoria, 3084, Australia. b.wines@ari.unimelb.edu.au
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Wines
authors.forename: Halina M
authors.initials: HM
authors.lastname: Trist
authors.forename: Renato C
authors.initials: RC
authors.lastname: Monteiro
authors.forename: Cees
authors.initials: C
authors.lastname: Van Kooten
authors.forename: P Mark
authors.initials: PM
authors.lastname: Hogarth
mesh_terms: D020816:Amino Acid Motifs; D015703:Antigens, CD / Q000737:chemistry*; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D002469:Cell Separation; D003432:Cross-Linking Reagents / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism*; D018076:DNA, Complementary / Q000378:metabolism; D003902:Detergents / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D005434:Flow Cytometry; D049452:Green Fluorescent Proteins; D006801:Humans; D007070:Immunoglobulin A / Q000737:chemistry; D007073:Immunoglobulin E / Q000737:chemistry; D008024:Ligands; D008164:Luminescent Proteins / Q000378:metabolism; D009154:Mutation; D010766:Phosphorylation; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011961:Receptors, Fc / Q000737:chemistry*; D017455:Receptors, IgE / Q000737:chemistry; D011994:Recombinant Proteins / Q000737:chemistry; D013997:Time Factors
chemical_list: D015703:Antigens, CD; D003432:Cross-Linking Reagents; D018076:DNA, Complementary; D003902:Detergents; C036832:Fc(alpha) receptor; C045281:IgA receptor; D007070:Immunoglobulin A; D008024:Ligands; D008164:Luminescent Proteins; D011961:Receptors, Fc; D017455:Receptors, IgE; D011994:Recombinant Proteins; D049452:Green Fluorescent Proteins; D007073:Immunoglobulin E; D002118:Calcium