Extracellular mutations of non-obese diabetic mouse FcgammaRI modify surface expression and ligand binding.
The non-obese diabetic mouse (NOD) expresses a unique form of the high affinity receptor for IgG (FcgammaRI), containing multiple mutations that result in substitutions and insertions of amino acids and a truncated cytoplasmic tail. As a result of these major changes, receptor affinity for IgG increases 10-fold over that of wild-type FcgammaRI from BALB/c mice, while the specificity for ligand is retained. Kinetic analysis revealed that while the association rate of IgG with FcgammaRI from NOD mice (FcgammaRI-NOD) and FcgammaRI from BALB/c mice (FcgammaRI-BALB) is similar, IgG bound much more tightly to FcgammaRI-NOD as revealed by a profoundly diminished dissociation rate. Transfection studies demonstrated that FcgammaRI-NOD was expressed at one-tenth of the level of FcgammaRI-BALB. Although mouse FcgammaRI was previously not known to associate with the FcepsilonRI gamma-subunit, transfection of COS-7 cells demonstrates that like human FcgammaRI, mouse FcgammaRI is also able to associate with this signaling subunit. Furthermore, expression levels of FcgammaRI-NOD were not restored by the presence of the FcepsilonRI gamma-subunit. The difference in the levels of expression was mapped to mutations in the extracellular region of FcgammaRI-NOD as replacement of the extracellular domains with those of human FcgammaRI or FcgammaRI-BALB restored expression to that of human FcgammaRI or FcgammaRI-BALB.
Gavin
A L
AL
Austin Research Institute, Austin Hospital, Heidelberg, Victoria 3084, Australia.
Hamilton
J A
JA
Hogarth
P M
PM
D000595:Amino Acid Sequence; D000818:Animals; D001853:Bone Marrow / Q000276:immunology; D001854:Bone Marrow Cells; D002460:Cell Line; D002522:Chlorocebus aethiops; D017931:DNA Primers; D018076:DNA, Complementary; D003922:Diabetes Mellitus, Type 1 / Q000235:genetics / Q000276:immunology; D005434:Flow Cytometry; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism*; D007700:Kinetics; D008024:Ligands; D008264:Macrophages / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D016688:Mice, Inbred NOD; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D016133:Polymerase Chain Reaction; D017452:Receptors, IgG / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013154:Spleen / Q000276:immunology; D013379:Substrate Specificity; D014162:Transfection
D017931:DNA Primers; D018076:DNA, Complementary; D007074:Immunoglobulin G; D008024:Ligands; D017452:Receptors, IgG; D011993:Recombinant Fusion Proteins