Physical association of Fc receptor gamma chain homodimer with IgA receptor.
The receptor for IgA, Fc alpha R, consists of one IgA-binding alpha chain and a signal-transducing dimeric FcR gamma chain. Immunoprecipitation with an anti-Fc alpha R alpha chain monoclonal antibody from the lysates of U937 cells (human monocytic cell line) revealed an association of 20 kd (unreduced) and 10 kd (reduced) molecules to Fc alpha R alpha chain on sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE). These molecules were confirmed to be FcR gamma chain by immunoblotting probed with anti-FcR gamma chain antibody. A serial immunoprecipitation with both antibodies further ascertained the FcR gamma association with Fc alpha R alpha. The lysates precleared with anti-FcR gamma antibody were subjected to the second immunoprecipitation with an anti-Fc alpha R alpha monoclonal antibody. By this preclearance, FcR gamma disappeared, and the Fc alpha R alpha appeared to be significantly decreased on SDS-PAGE, suggesting that a part of Fc alpha R alpha was co-absorbed with FcR gamma. Therefore, it may be likely that Fc alpha R is expressed in two forms, namely, with or without FcR gamma. We next reconstituted the Fc alpha R alpha-FcR gamma association by introducing both chains into host cells. The expression of Fc alpha R alpha was achieved by introducing Fc alpha R alpha alone, and the cointroduction of FcR gamma did not enhance Fc alpha R alpha expression on the cell surface, suggesting again the occurrence of the two forms of FC alpha R.
Department of Immunology, Juntendo University School of Medicine, Tokyo, Japan.
K
K
Saito
K
K
Suzuki
H
H
Matsuda
K
K
Okumura
C
C
Ra
D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D006801:Humans; D015151:Immunoblotting; D007951:Leukemia, Myeloid / Q000378:metabolism / Q000473:pathology; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D011961:Receptors, Fc / Q000737:chemistry* / Q000378:metabolism*; D017452:Receptors, IgG / Q000737:chemistry* / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D014407:Tumor Cells, Cultured
C045281:IgA receptor; D046911:Macromolecular Substances; D011961:Receptors, Fc; D017452:Receptors, IgG