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EGF receptor residues Leu 679 , Leu 680 mediate selective sorting of ligand‐receptor complexes in early endosomal compartments
Author(s) -
Kil Song Jae,
Carlin Cathleen
Publication year - 2000
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/1097-4652(200010)185:1<47::aid-jcp4>3.0.co;2-o
Subject(s) - endosome , endocytic cycle , internalization , microbiology and biotechnology , receptor , biology , lysosome , endocytosis , mutant , ligand (biochemistry) , intracellular , biochemistry , gene , enzyme
Dileucine‐based motifs have been shown to regulate endosomal sorting of a number of membrane proteins. Previously, we have shown that the dileucine motif Leu 679 , Leu 680 in the juxtamembrane domain of the human epidermal growth factor receptor is involved in the endosome‐to‐lysosome transport of ligand‐receptor complexes. Substitution of alanine residues for Leu 679 , Leu 680 led to a reduction in ligand‐induced receptor degradation without affecting internalization. In the current study, we have further characterized ligand‐dependent intracellular sorting of EGF receptors containing a L679A, L680A. Immunocytochemical studies reveal that although mutant receptors redistribute from the cell surface to transferrin receptor‐positive endocytic vesicles similar to wild‐type following ligand stimulation, their accumulation in Lamp‐1‐positive late endosomes/lysosomes is retarded compared to wild‐type. Kinetic analysis of 125 I‐EGF trafficking shows that reduced accumulation of internalized mutant receptors in Lamp‐1–positive vesicles is due to rapid recycling of ligand‐receptor complexes from early endocytic compartments. In addition, the fraction of intracellular 125 I‐EGF that is transported to late endocytic compartments in cells with mutant receptors is not as efficiently degraded as it is in cells with wild‐type receptors. Furthermore, wild‐type receptors in endocytic vesicles isolated by Percoll gradient fractionation are more resistant to in vitro digestion with proteinase K than mutant receptors. We propose that mutant receptors interact inefficiently with lysosomal sorting machinery, leading to their increased recycling. Our results are consistent with a model in which the Leu 679 , Leu 680 signal facilitates sequestration of ligand‐receptor complexes into internal vesicles of multivesicular endosome‐to‐lysosome transport intermediates. J. Cell. Physiol. 185:47–60, 2000. © 2000 Wiley‐Liss, Inc.