Postendocytic trafficking of epidermal growth factor-receptor complexes is mediated through saturable and specific endosomal interactions

• Published in: The Journal of biological chemistry 1994-06, Vol.269 (22), p.15749-15755
• Main Authors: French, A R, Sudlow, G P, Wiley, H S, Lauffenburger, D A
• Format: Article
• Language: English
• Subjects: Animals; Cell Membrane - metabolism; Endocytosis; Epidermal Growth Factor - metabolism; ErbB Receptors - biosynthesis; ErbB Receptors - metabolism; Fibroblasts - metabolism; Humans; Kinetics; Ligands; Mathematics; Mice; Models, Biological; Mutagenesis, Site-Directed; Organelles - metabolism; Receptor Protein-Tyrosine Kinases - metabolism; Receptors, Cell Surface - metabolism; Sequence Deletion; Transfection; Transforming Growth Factor alpha - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(17)40744-7

Intracellular trafficking of the epidermal growth factor receptor (EGF-R) is regulated by receptor occupancy. To investigate this, we developed an assay to study endosomal sorting under steady-state conditions. Using a cell line transfected with EGF-R variants, we found that the fraction of internalized EGF.EGF-R complexes sorted to lysosomes was a function of the number of intracellular complexes and required sequences in the cytoplasmic domain of the receptor. As the number of intracellular occupied wild-type receptors increased from 3 x 10(2) to 2 x 10(5)/cell, the fraction of internalized EGF that was degraded dropped from 70 to 20%. Transforming growth factor-alpha, which dissociates from the EGF-R at endosomal pH, was degraded to a uniform extent of approximately 50% at all intracellular ligand concentrations. EGF internalized by receptors lacking a cytoplasmic domain (c'647) was degraded to an extent of only 5-10% independent of the number of intracellular complexes. Mutant receptors truncated either at residues 1022 or 973 displayed sorting patterns intermediate between wild-type and c'647 receptors. Despite large differences in their internalization rates, the fractional sorting patterns of c'1022 and c'973 receptors were indistinguishable. Receptor tyrosine kinase activity appeared to have a small effect on sorting pattern, but only in the context of full-length receptors. Our results indicate that the default pathway of internalized receptors is rapidly recycling and that lysosomal targeting of occupied EGF-R is due to endosomal retention that is both specific and saturable. In addition, internalization and endosomal retention of EGF-R appear to be mediated by distinct structural elements.