Earlier studies have shown that the mast cell receptor IgE (FcεRI) is expressed on COS-7 cells transfected with the cDNA for each of the three types of subunits that form the tetrameric, αβγ2, receptor. Although such transfected COS cells fail to exhibit some of the early biochemical perturbations initiated by aggregation of the receptor on normal mast cells and related tumor lines, we show here that other characteristics of the endogenous FcεRI are retained. Thus, the unaggregated transfected wild-type receptors were found to have a restricted translational diffusion similar to that observed for endogenous receptors on mast cells as assessed by fluorescence photobleaching and recovery. Similarly, as with endogenous receptors, the mobility of transfected receptors was sharply reduced when the receptors were aggregated by reaction with small oligomers of IgE. In addition, aggregation of the transfected FcεRI caused them to be internalized by the COS cells by a cytochalasin-sensitive mechanism, albeit at a considerably slower rate than was seen with endogenous receptors on mast cells or with transfected receptors in a line of receptor-deficient mast cells. We also examined the mobility and internalization before and after aggregation, of some 13 different combinations of receptor subunit mutants in which one or more of the five cytoplasmic domains of the receptor had been truncated. Our results show that whatever interactions between the receptor and cellular components may acocunt for the phenomena we studied, such interactions do not critically depend upon the bulk of the cytoplasmic domains of the receptor.
|Original language||English (US)|
|Number of pages||9|
|Journal||Journal of Immunology|
|State||Published - Jan 1 1991|
ASJC Scopus subject areas
- Immunology and Allergy