Linking protein N-glycosylation and CF : malfunctioning CFTR and pulmonary infection yield aberrant N-glycosylation of sputum derived proteins of CF individuals

Objectives: Mucins are abundant glycoproteins in human lungs. It is wellestablished that airway mucin O-glycosylation is aberrant in cystic fibrosis (CF) and involved directly or indirectly in the pathogenesis. As the first, we here investigate and establish the link between protein N-glycosylation and CF. Methods: N-glycosylation of crudely isolated sputum non-mucin proteins of five CF and five non-CF individuals with and without pulmonary infection was mapped using liquid chromatography and tandem mass spectrometry based glycomics and glycoproteomics. The resulting glycoprofiles were qualitatively and quantitatively compared between the patient groups. Results: Despite covering different patient characteristics including CFTR genotypes, age, gender and microbial flora, the sputum N-glycomes showed little interperson and longitudinal variation within the patient groups. Inter-group comparisons revealed that lung infection, primarily caused by P. aeruginosa, extensively altered the CF sputum N-glycosylation to paucimannoside rich profiles with simultaneous over-sialylation/fucosylation and under-bisecting GlcNAcylation of the complex N-glycans. The CF genotype in itself yielded fewer sputum N-glycome alterations by slightly increasing the abundance of paucimannose N-glycans in CF relative to pathogen-infected non-CF individuals. Conclusion: We have established that the absence of a functional CFTR and more importantly the bacterial infection of the respiratory tract of CF patients affect their sputum N-glycosylation phenotype. This study provides an important platform to further understand the complex cellular and molecular environment of the respiratory tract in CF.1 page(s