Metabolic isotopic labelling of plasma membrane glycoproteins from normal, Glanzmann's and Bernard-Soulier platelets
Apitz-Castro, R.; Michelena, V.; Sorribes, V.; Rodríguez, P.
Thrombosis Research 16(5-6): 715-725
1979
ISSN/ISBN: 0049-3848 PMID: 524318 Document Number: 150495
Normal, Glanzmann and Bernard-Soulier platelets were incubated in homologous plasma with 14C-labeled glucosamine (GLU), galactose (GAL) or mannose (MAN). Time-dependence of sugar uptake by the whole cells, plasma membrane incorporation of the individual sugars, the electrophoretic pattern of the metabolically labeled plasma membrane glycoproteins and the activity of the galactosyl- and mannosyl-transferases were compared. Results showed moderate decrease in MAN uptake by Glanzmann platelets, while uptake of either GLU or GAL was similar to controls. Bernard-Soulier platelets showed a significant increase in GLU and MAN uptake, while moderate increase was observed for GAL. Plasma membrane incorporation of all 3 sugars was markedly decreased in Bernard-Soulier, only MAN incorporation was decreased in Glanzmann. SDS-PAGE [sodium dodecyl sulfate-polyacrylamide gel electrophoresis] (reduced) of plasma membranes resolves from 10 to 14 labeled glycopeptides. For most resolved glycopeptides marked quantitative differences were found between Glanzmann, Bernard-Soulier and normal platelets. Galactosyl- and mannosyltransferase activity towards endogenous substrates was greatly diminished in platelet disorders. Instead of the lack of 4 or 2 specific glycoproteins, as had been reported, a more general perturbation of glycoprotein synthesis centered on the glycosylating enzymes apparently seemed to be the molecular basis for platelet malfunction in Glanzmann disease and Bernard-Soulier syndrome.