IgE receptor on human lymphocytes. IV. Further analysis of its structure and of the role of N-linked carbohydrates.
Previous studies have shown that the low affinity receptor for IgE (Fc epsilon R II) on human B lymphocytes was comprised of three components with apparent Mr of 45, 65 to 95, and 37 kDa. The present results indicate that the 37-kDa component is a soluble degradation fragment of the 45-kDa component and they also suggest that the 65- to 95-kDa component is probably made of aggregates of the above components that are formed after solubilization of the cells. The 45-kDa component appears to be a glycoprotein containing several sialic acid residues, O-linked carbohydrates and one N-linked carbohydrate chain that is of the complex type. Partial digestion of the purified 65- to 95-, 45-, and 37-kDa molecules with alpha-chymotrypsin or protease V8 generates several fragments with identical mobility on SDS-PAGE. The 37 kDa is not N-glycosylated but like the IgE-binding factors present in the culture supernatant of Fc epsilon R-bearing cells, it contains sialic acid and O-linked carbohydrates. On incubation with protease inhibitors, the Mr of IgE-binding factors (BF) is shifted from 25-27 to 37 kDa, indicating that IgE-BF are derived from the proteolytic cleavage of the 37-kDa molecule, previously identified as a membrane component of Fc epsilon R. On incubation with N-glycosylation inhibitors, the production of IgE-BF is significantly increased indicating that N-glycosylation inhibits the degradation of Fc epsilon R into IgE-BF. Inasmuch as the effect of glycosylation inhibitors is not prevented by monensin, it is concluded that all the IgE-BF are derived from surface Fc epsilon R and not from their intracellular precursors.
Letellier
M
M
Laboratory for Allergy Research, Notre Dame Hospital, Montreal, Quebec, Canada.
Nakajima
T
T
Delespesse
G
G
D000944:Antigens, Differentiation, B-Lymphocyte / Q000302:isolation & purification* / Q000378:metabolism / Q000502:physiology; D001402:B-Lymphocytes / Q000378:metabolism*; D002236:Carbohydrate Conformation; D002460:Cell Line; D006026:Glycoside Hydrolases; D006031:Glycosylation; D006801:Humans; D007073:Immunoglobulin E / Q000378:metabolism*; D008222:Lymphokines / Q000302:isolation & purification / Q000378:metabolism; D008970:Molecular Weight; D009439:Neuraminidase; D009844:Oligosaccharides / Q000502:physiology*; D010449:Peptide Mapping; D029584:Prostatic Secretory Proteins; D011961:Receptors, Fc / Q000302:isolation & purification* / Q000378:metabolism / Q000502:physiology; D017455:Receptors, IgE; D013329:Structure-Activity Relationship
D000944:Antigens, Differentiation, B-Lymphocyte; D008222:Lymphokines; D009844:Oligosaccharides; D029584:Prostatic Secretory Proteins; D011961:Receptors, Fc; D017455:Receptors, IgE; C043076:beta-microseminoprotein; C013059:immunoglobulin-binding factors; D007073:Immunoglobulin E; D006026:Glycoside Hydrolases; C020668:glycanase; D009439:Neuraminidase