Ligand-independent dimer formation of epidermal growth factor receptor (EGFR) is a step separable from ligand-induced EGFR signaling.
Dimerization and phosphorylation of the epidermal growth factor (EGF) receptor (EGFR) are the initial and essential events of EGF-induced signal transduction. However, the mechanism by which EGFR ligands induce dimerization and phosphorylation is not fully understood. Here, we demonstrate that EGFRs can form dimers on the cell surface independent of ligand binding. However, a chimeric receptor, comprising the extracellular and transmembrane domains of EGFR and the cytoplasmic domain of the erythropoietin receptor (EpoR), did not form a dimer in the absence of ligands, suggesting that the cytoplasmic domain of EGFR is important for predimer formation. Analysis of deletion mutants of EGFR showed that the region between (835)Ala and (918)Asp of the EGFR cytoplasmic domain is required for EGFR predimer formation. In contrast to wild-type EGFR ligands, a mutant form of heparin-binding EGF-like growth factor (HB2) did not induce dimerization of the EGFR-EpoR chimeric receptor and therefore failed to activate the chimeric receptor. However, when the dimerization was induced by a monoclonal antibody to EGFR, HB2 could activate the chimeric receptor. These results indicate that EGFR can form a ligand-independent inactive dimer and that receptor dimerization and activation are mechanistically distinct and separable events.
Institute of Life Science, Kurume University, Kurume, Fukuoka 839-0861, Japan.
Xiaochun
X
Yu
Kailash D
KD
Sharma
Tsuyoshi
T
Takahashi
Ryo
R
Iwamoto
Eisuke
E
Mekada
D000818:Animals; D000906:Antibodies / Q000378:metabolism; D002460:Cell Line; D003432:Cross-Linking Reagents / Q000378:metabolism; D019281:Dimerization; D004815:Epidermal Growth Factor / Q000235:genetics / Q000378:metabolism; D066246:ErbB Receptors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017930:Genes, Reporter; D066257:Heparin-binding EGF-like Growth Factor; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D008024:Ligands; D017467:Receptors, Erythropoietin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D013388:Succinimides / Q000378:metabolism
D000906:Antibodies; D003432:Cross-Linking Reagents; C587883:HBEGF protein, human; D066257:Heparin-binding EGF-like Growth Factor; D036341:Intercellular Signaling Peptides and Proteins; D008024:Ligands; D017467:Receptors, Erythropoietin; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D013388:Succinimides; D004815:Epidermal Growth Factor; C035759:3,3'-dithiobis(sulfosuccinimidyl propionate); D066246:ErbB Receptors