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 (sLex) in airway epithelial repair.
Objective To examine whether an sLex 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 sLex 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 sLex was catalysed by a specific α-1,3-fucosyltransferase (FucT-IV). To evaluate the role of sLex in EGFR activation, a knockdown of the FucT-IV gene with small interfering RNA (siRNA) and an inhibitory anti-sLex antibody (KM-93) was used.
Results We demonstrated a co-localization of sLex with EGFR on NHBE cells using confocal microscopy. Using a blocking antibody for sLex 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 sLex 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 sLex and tyrosine-phosphorylated EGFR (pY845-EGFR) in the epithelium of asthmatic subjects compared with that of normal subjects.
Conclusion The present data demonstrate that sLex, 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.
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