Similarities in glycosylation and transport between the secreted and plasma membrane forms of the epidermal growth factor receptor in A‐431 cells

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Abstract
We have studied the synthesis and oligosaccharide processing of the 110,000 dalton form of the epidermal growth factor (EGF) receptor that is secreted into the medium of A‐431 cells. Its 90,000 dalton precursor is soluble within the lumen of intracellular membrane vesicles shortly after synthesis, indicating that it lacks a membrane anchor. Analysis of labeled glycopeptides reveals that the glycosylation of the 110,000 dalton, secreted receptor is very similar to that of the 170,000 dalton, plasma membrane receptor. Based on Concanavalin A‐Sepharose elution profiles of its glycopeptides, the secreted receptor has both complex and high‐mannose N‐linked oligosaccharides. Also, like the plasma membrane receptor, the secreted receptor contains N‐acetylgalactosamine residues in its complex chains. Not only are major features of oligosaccharide processing of the soluble and membrane‐bound forms of the receptors similar, but the kinetics of transport to the cell exterior is the same for each. These data indicate that the glycosylation pattern and kinetics of cellular transport of the EGF receptor are determined by factors other than the sequence of its cytoplasmic and transmembrane domains.

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