Altered fucosylation of membrane glycoproteins from cystic fibrosis fibroblasts.

Peripheral membrane glycopeptides isolated from skin fibroblasts of patients with cystic fibrosis (CF) had an altered fucosylation when compared to age, race, and sex-matched controls. Glycopeptides obtained by trypsin treatment of cultured cells, metabolically labeled with L-[3H]fucose, were purified on a Sephadex G-50 column. The neutral monosaccharide composition of the glycopeptides was determined by gas-liquid chromatography of the alditol acetate derivatives. The fucose content of the CF membrane glycopeptides and the molar ratio of fucose to the other monosaccharides were increased when compared with those of controls. The mean fucose content was 2.3 +/- 1.7 (SD) and 0.3 +/- 0.05 (SD) nmol per 10(6) cells for CF control glycopeptides, respectively. Moreover, the specific activity of incorporated L-[3H]fucose was markedly decreased in the CF glycopeptides, 355 +/- 183 (SD) and 2707 +/- 839 (SD) cpm per nmol of fucose for the CF and controls, respectively. The membrane glycopeptides were further purified and characterized by affinity chromatography on immobilized lectins. The decreased specific activity of incorporated fucose was present in CF glycopeptides which bound to immobilized lentil lectin before and after Pronase degradation. Moreover, the CF glycopeptides bound more tightly to lentil lectin. Several classes of glycopeptides bind to lentil lectin and all contain Fuc alpha 1----6GlcNAc at the core. The binding characteristics of the Pronase-digested membrane glycopeptides for immobilized concanavalin A, lentil leukoagglutinating phytohemagglutinin, erythroagglutinating phytohemagglutinin, and serotonin provided information on the structure of the altered CF glycopeptides. Most of these radioactive glycopeptides were of the biantennary type containing at least one sialic acid residue and all containing fucosyl residues at the asparagine core.(ABSTRACT TRUNCATED AT 250 WORDS)