Sialyl Lewis X modification of the epidermal growth factor receptor regulates receptor function during airway epithelial wound repair

Summary Background Epidermal growth factor receptor (EGFR) is a major regulator of airway epithelial cell (AEC) functions such as migration, proliferation and differentiation, which play an essential role in epithelial repair. EGFR is a glycoprotein with 12 potential N ‐glycosylation sites in its extracellular domain. Glycosylation of EGFR has been shown to modulate its function. Previously, our laboratory demonstrated an important role of the carbohydrate structure sialyl Lewis x (sLe x ) in airway epithelial repair. Objective To examine whether an sLe x decoration of EGFR can modulate receptor function during AEC repair. Methods Primary normal human bronchial epithelial (NHBE) cells were cultured in vitro . Co‐localization of sLe x and EGFR was examined using confocal microscopy. Expressions of RNA and protein were analysed using RT‐PCR and Western blotting. The final step in the synthesis of sLe x was catalysed by a specific α‐1,3‐fucosyltransferase (FucT‐IV). To evaluate the role of sLe x in EGFR activation, a knockdown of the FucT‐IV gene with small interfering RNA (siRNA) and an inhibitory anti‐sLe x antibody (KM‐93) was used. Results We demonstrated a co‐localization of sLe x with EGFR on NHBE cells using confocal microscopy. Using a blocking antibody for sLe x after a mechanical injury, we observed a reduction in EGFR phosphorylation and epithelial repair following injury. FucT‐IV demonstrates a temporal expression coordinate with epithelial repair. Down‐regulation of FucT‐IV expression in NHBE by specific siRNA suppressed sLe x expression. The use of FucT‐IV siRNA significantly reduced phosphorylation of EGFR and prevented epithelial repair. An immunohistochemical analysis of human normal and asthmatic airways showed a significant reduction in sLe x and tyrosine‐phosphorylated EGFR (pY 845 ‐EGFR) in the epithelium of asthmatic subjects compared with that of normal subjects. Conclusion The present data demonstrate that sLe x , in association with EGFR, in NHBE is coordinate with repair. This glycosylation is important in modulating EGFR activity to affect the repair of normal primary AEC. Cite this as : S. Allahverdian, A. Wang, G. K. Singhera, B. W. Wong and D. R. Dorscheid, Clinical & Experimental Allergy , 2010 (40) 607–618.