Ezrin is a scaffolding
protein that is involved in
oncogenesis by linking cytoskeletal and
membrane proteins.
Ezrin interacts with
epidermal growth factor receptor (EGFR) in the cell membrane, but little is known about the effects of this interaction on EGFR signaling pathway. In this study, we established the
biological and functional significance of
ezrin-EGFR interaction in
non-small cell lung cancer (NSCLC) cells. Endogenous
ezrin and EGRF interaction was confirmed by co-immunoprecipitation and immunofluorescent staining. When expression of
ezrin was inhibited, EGFR activity and phosphorylation levels of downstream signaling pathway
proteins ERK and STAT3 were decreased. Cell fractionation experiments revealed that nuclear EGFR was significantly diminished in
ezrin-knockdown cells. Consequently,
mRNA levels of EGFR target genes
AURKA, COX-2,
cyclin D1, and iNOS were decreased in
ezrin-depleted cells. A small molecule inhibitor of
ezrin,
NSC305787, reduced
EGF-induced phosphorylation of EGFR and downstream target
proteins, EGFR nuclear translocation, and
mRNA levels of nuclear EGFR target genes similar to
ezrin suppression.
NSC305787 showed synergism with
erlotinib in wild-type EGFR-expressing NSCLC cells, whereas no synergy was observed in EGFR-null cells. Phosphorylation of
ezrin on Y146 was found as an enhancer of
ezrin-EGFR interaction and required for increased proliferation, colony formation, and drug resistance to
erlotinib. These findings suggest that
ezrin-EGFR interaction augments oncogenic functions of EGFR and that targeting
ezrin may provide a potential novel approach to overcome
erlotinib resistance in NSCLC cells.