GLYCOSYLATION DIFFERENCES BETWEEN A CYSTIC-FIBROSIS AND RESCUED AIRWAY CELL-LINE ARE NOT CFTR DEPENDENT

Altered glycosylation of mucus and membrane glycoconjugates could expl ain reported differences in binding of bacterial pathogens to cystic f ibrosis (CF) versus normal tissue. However, because bacteria can alter cell surface glycoconjugates, it is not possible to assess the role o f cystic fibrosis transmembrane conductance regulators (CFTR) in glyco sylation in these studies. To address this issue, we have developed qu antitative lectin binding assays to compare cell surface glycosylation in well-matched immortalized CF cells and rescued cell lines. The CF airway bronchial epithelial cell line IB3-1 consistently bound more pe anut agglutinin (PNA) than its clonal derivative S9, which stably expr esses functional wild-type CFTR. Pretreatment with neuraminidase incre ased PNA binding and abolished the difference between the two cell lin es. However, infection of the IB3-1 cells with a replication-deficient recombinant adenovirus encoding CFTR restored CFTR function but did n ot alter PNA binding to cells. In contrast, treatment with the weak ba se ammonium chloride increased PNA binding to both cell lines as expec ted. Our data show that even clonally related CF and rescued cells can exhibit significant differences in carbohydrate processing. Although the differences that we found are consistent with the proposed role fo r CFTR in modulating intraorganellar pH, our data strongly suggest tha t they are CFTR independent. These studies add a cautionary note to th e interpretation of differences in glycosylation between CF and normal primary tissues and immortalized cells.