title: Oligomerization-function relationship of EGFR on living cells detected by the coiled-coil labeling and FRET microscopy.
abstract: The epidermal growth factor receptor (EGFR) is a well-studied receptor tyrosine kinase and an important anticancer therapeutic target. The activity of EGFR autophosphorylation and transphosphorylation, which induces several cell signaling pathways, has been suggested to be related to its oligomeric state. However, the oligomeric states of EGFRs induced by EGF binding and the receptor-ligand stoichiometry required for its activation are still controversial. In the present study, we performed Förster resonance energy transfer (FRET) measurements by combining the coiled-coil tag-probe labeling method and spectral imaging to quantitatively analyze EGFR oligomerization on living CHO-K1 cell membranes at physiological expression levels. In the absence of its ligands, EGFRs mainly existed as monomers with a small fraction of predimers (~10%), whereas ~70% of the EGFRs formed dimers after being stimulated with the ligand EGF. Ligand-induced dimerization was not significantly affected by the perturbation of membrane components (cholesterol or monosialoganglioside GM3). We also investigated both dose and time dependences of EGF-dependent EGFR dimerization and autophosphorylation. The formation of dimers occurred within 20s of the ligand stimulation and preceded its autophosphorylation, which reached a plateau 90 s after the stimulation. The EGF concentration needed to evoke half-maximum dimerization (~1 nM) was lower than that for half-maximum autophosphorylation (~8 nM), which suggested the presence of an inactive dimer binding a single EGF molecule.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Yamashita
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Yano
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Kawano
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan. Electronic address: mkatsumi@pharm.kyoto-u.ac.jp.
authors.forename: Katsumi
authors.initials: K
authors.lastname: Matsuzaki
mesh_terms: D000818:Animals; D016466:CHO Cells; D002470:Cell Survival; D006224:Cricetinae; D003412:Cricetulus; D004815:Epidermal Growth Factor / Q000494:pharmacology; D066246:ErbB Receptors / Q000737:chemistry* / Q000378:metabolism*; D031541:Fluorescence Resonance Energy Transfer; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D018613:Microscopy, Confocal; D010766:Phosphorylation / Q000187:drug effects; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D051381:Rats; D013997:Time Factors
chemical_list: D008565:Membrane Proteins; D004815:Epidermal Growth Factor; D066246:ErbB Receptors
keywords: Dimerization; FRET; Live-cell imaging