The nuclear accumulation of a variant epidermal growth factor receptor (EGFR) lacking the transmembrane domain requires coexpression of a full-length EGFR.
Both the epidermal growth factor (EGF) and its receptor (EGFR) accumulate in the nucleoplasm during liver regeneration. This localization in a nonmembraneous compartment presents a challenge in that the standard form of EGFR is a transmembrane protein and suggests the existence of a variant, soluble form of EGFR. To investigate the localization of such a putative EGFR splice variant, we generated a transmembrane-devoid form of EGFR. We placed this transmembrane-negative [TM(-)] EGFR construct and full-length wild-type (wt) EGFR either in a retroviral transfection vector or in an inducible expression vector. Mouse 3T3 cells, which express endogenous EGFR, were transfected with the TM(-) EGFR construct. The expression of these TM(-) EGFR, detected with a specific antibody against human EGFR using a confocal laser-scanning microscope, was predominantly found in the cytoplasm with no nuclear localization. After an overnight incubation with EGF the TM(-) EGFR accumulated in the nucleus. In mouse NR6 cells, which lack endogenous EGFR, transfected TM(-) EGFR were found in the cytoplasm, but incubation with EGF did not result in a nuclear accumulation of TM(-) EGFR. However, NR6 cells transfected with both TM(-) EGFR and wt EGFR showed nuclear accumulation after EGF treatment. These results suggest that both the wt EGFR and the TM(-) EGFR are required for nuclear accumulation of TM(-) EGFR and may implicate a model of homotypic recognition and translocation of a splice variant of EGFR.
Marti
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Endocrine and Diabetes Division, Department of Clincal Chemistry, University Hospital, Bern, CH-3010, Switzerland. ulrich.marti@dkf2.unibe.ch
Wells
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A
D016475:3T3 Cells; D017398:Alternative Splicing; D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066246:ErbB Receptors / Q000096:biosynthesis* / Q000737:chemistry; D005822:Genetic Vectors / Q000378:metabolism; D006801:Humans; D051379:Mice; D018613:Microscopy, Confocal; D016296:Mutagenesis; D009173:Mycophenolic Acid / Q000494:pharmacology; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D014162:Transfection
D004791:Enzyme Inhibitors; D020033:Protein Isoforms; D066246:ErbB Receptors; D009173:Mycophenolic Acid