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A single EGF molecule activates a preformed EGFR dimer: a single‐molecule multi‐color TIRF microscopy study
Author(s) -
Saita Eiichiro,
Mong Dingze,
Maruyama Ichiro N
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.615.5
Subject(s) - dimer , epidermal growth factor , epidermal growth factor receptor , total internal reflection fluorescence microscope , biophysics , microbiology and biotechnology , fluorescence microscope , chemistry , ligand (biochemistry) , receptor , biology , fluorescence , biochemistry , physics , organic chemistry , quantum mechanics , membrane
Epidermal growth factor receptor (EGFR) plays roles in cell proliferation, inhibition of apoptosis and angiogenesis among others. It has long been thought that binding of the ligand induces the dimer formation of monomeric EGFR (the “ligand‐induced dimerization model”). Tyrosine residues in the C‐terminal tail of active EGFR are phosphorylated, which triggers activation of downstream signaling cascades by recruiting effector proteins such as Shc1. However, many recent studies indicate that EGFR exists in a form of dimer (preformed dimer). To understand the molecular mechanism underlying activation of EGFR, we visualized the activation of EGFR by ligand binding at the single‐molecule level. Using a multi‐color TIRF microscope, we directly observed interaction among EGFR, EGF labeled with two different fluorescent dyes, and GFP‐tagged Shc1. Within 30 seconds of application of the dye‐conjugated EGF to cultured cells, three different fluorescent spots of EGF and Shc1 appeared on the cell surface. Unexpectedly, two different fluorescent colors derived from EGF do not co‐localize, and instead, single‐colored EGF binding induces Shc1 recruitment to EGFR. These results suggest that binding of single EGF molecule can activate preformed EGFR dimer, and are consistent with negative co‐operative binding between EGF to EGFR. Support or Funding Information This work was partly supported by funding to the Information Processing Biology Unit from the Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan.