Structural aspects of the epidermal growth factor receptor required for transmodulation of erbB-2/neu.
The epidermal growth factor receptor (EGF-R) is known to transmodulate the activity and level of the erbB-2/neu protein in several epithelial cell lines. We therefore determined which structural features of the EGF-R were important in transmodulating erbB-2. We found that the addition of EGF to nontransformed epithelial cells resulted in down-regulation of erbB-2 with the same kinetics and similar extent as the EGF-R. By using cells expressing a series of EGF-R modified by site-directed mutagenesis, we found that EGF-R tyrosine kinase activity was not necessary for down-regulation of erbB-2, but receptor sequences between 899 and 958 in the EGF-R were required. To determine whether transmodulation was associated with activation of erbB-2, tyrosine phosphorylation of erbB-2 was determined following addition of EGF. Again, phosphorylation of erbB-2 following EGF addition did not require the intrinsic tyrosine kinase activity of the EGF-R, but did require sequences between 899 and 958. To determine the localization of EGF-R and erbB-2 following EGF addition, the relative distribution of the two receptors was evaluated by fluorescence microscopy. Surprisingly, the majority of erbB-2 was found in small cytoplasmic vesicles, whereas the EGF-R was predominantly found on the cell surface. Addition of EGF resulted in a redistribution and consequent colocalization of both receptors in endosomal and lysosomal structures. We conclude that activation and transmodulation of erbB-2 does not require intrinsic tyrosine kinase activity of the EGF-R, but does require sequences in the EGF-R which regulate its trafficking.
Worthylake
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Division of Cell Biology and Immunology, Department of Pathology, University of Utah, Salt Lake City, Utah 84132, USA.
Wiley
H S
HS
D000818:Animals; D001940:Breast / Q000166:cytology / Q000378:metabolism; D015536:Down-Regulation; D004815:Epidermal Growth Factor / Q000494:pharmacology; D004848:Epithelium / Q000378:metabolism; D066246:ErbB Receptors / Q000737:chemistry / Q000378:metabolism*; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D008247:Lysosomes / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000166:cytology / Q000378:metabolism; D051379:Mice; D010766:Phosphorylation; D011817:Rabbits; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000737:chemistry / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000378:metabolism
D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D018719:Erb-b2 Receptor Tyrosine Kinases; D014443:Tyrosine