LOCALIZATION OF GLYCOPROTEINS CONTAINING TYPE-3 O-LINKED GLYCOSYLATION TO MULTILAMELLAR BODIES IN DICTYOSTELIUM-DISCOIDEUM

Glycosylation of proteins in Dictyostelium discoideum has been recentl y classified into several types based on structural and mutational stu dies. Type 3 O-linked glycosylation contains fucose and N-acetyl-gluco samine and is recognised by the carbohydrate-specific monoclonal antib ody MUD 62. The developmentally regulated cysteine proteinase, ddCP38B , is the major protein recognised by both MUD 62 and a second carbohyd rate-specific monoclonal antibody, MUD 166, in vegetative cells using bacteria as a food source. Using immunofluorescence and immunogold lab elling, glycoproteins carrying the MUD 62 and MUD 166-specific epitope s have been localised intracellularly to the lysosomal network and mul tilamellar bodies of D. discoideum. These bodies contain remnants of u ndigested bacteria and are egested from the cell prior to starvation-i nduced aggregation. These results suggest that extracellular glycoprot eins carrying the Type 3 O-linkage, such as ddCP38B, may not be secret ed via the conventional pathway but may be released into the medium fo llowing targeting to the multilamellar bodies.