Glycoproteins play an important role in the development of the organism. The function of cell-surface glycoproteins and the biological role of their carbohydrate moieties have been studied primarily in mammalian cell culture systems. I have recently extended such studies to Drosophila melanogaster where I have the advantage of genetic analysis to study the function of these molecules during development of the organism.; My thesis work involved the study of N-linked glycoprotein biosynthesis in Drosophila melanogaster using both biochemical and genetic approaches. I have demonstrated that the late processing steps of the N-linked glycoprotein biosynthesis pathway in the fly are similar, but not identical, to the relatively well characterized pathway in vertebrates. Five oligosaccharide processing inhibitors were used to feed and inject embryos prior to the cellularization stage of the Drosophila development. All inhibitors resulted in developmental delay and some lethality, which suggest that glycosidase enzyme activity is important in Drosophila development.; To study the glycosidase in the N-linked glycoprotein biosynthetic pathway, I have developed two sensitive in vitro enzyme assays for both {dollar}alpha{dollar}-glucosidase and {dollar}alpha{dollar}-mannosidase. Enzyme activity is inhibited by its respective inhibitor except castanospermine, which has little effect on fly {dollar}alpha{dollar}-glucosidase activity. The profile of carbohydrate moieties and the monosaccharide constituents of lectin-reactive glycoproteins in fly were analyzed. The results show that the fly uses the same set of monosaccharide to build their carbohydrate moieties as in all other system studied to date. Studies from the FITC-conjugated lectin binding of frozen sections of fly show that Drosophila produces complex-type glycoproteins.; The second major approach I have taken is the genetic analysis of a glycosylation mutant: a tunicamycin-resistant mutant TMR1{dollar}sp{lcub}1C17{rcub}{dollar}. X-ray mutagenesis for generating deficiencies in TMR1{dollar}sp{lcub}1C17{rcub}{dollar} region and a lethal screen for alleles of TMR1{dollar}sp{lcub}1C17{rcub}{dollar} were carried out. I have mapped this locus in between the ra and ca loci to the cytological position 99A-B. Functional analysis of N-linked glycoproteins in the developing visual system has been carried out using genetic mosaicism for tunicamycin-resistance. I have demonstrated that embryogenesis and early first instar stage of development are very critical periods during which glycoprotein synthesis is very important for the survival of the animal.
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