Most proteins destined for secretion or incorporation into cell surfaces or basement membranes become glycosylated during their formation. The biosynthesis of glycoprotains requires an elaborate enzymatic machinery which functions at pre-, co- and post-translational stages to yield a variety of carbohydrate units which are well suited to serve as recognition signals in diverse biological interactions. Numerous sites for regulation are afforded by saccharide unit assembly and the possibilities for malfunction are many and may be operative in diseases like diabetes, neoplasia and cystic fibrosis. It is the objective of this research proposal to undertake a multifaceted investigation involving several aspects of the biosynthesis of asparagine-linked carbohydrate units, the sulfation and recycling of cell surface glycoproteins and the biogenesis of the glycoprotein components of basement membranes and regulation thereof. Studies on N-linked saccharides in thyroid and liver will seek to accomplish the following: isolation and characterization with defined exogenous acceptors of the glucosyltransferases involved in the formation of the dolichyl pyrophosphoryl-linked precursor oligosaccharide; delineation of the mechanism and energetics involved in the transmembrane (endoplasmic reticulum) passage of the activated glucose needed for these reactions; purification of the oligosaccharyltransferase responsible for N-glycosylation and evaluation of the hypothesis that this enzyme has an oligosaccharide-lipid hydrolysis function of potential regulatory importance; exploration, through studies with microsomal vesicles and isolation of enzymes, of the alternate routes of carbohydrate unit processing which occur in the endoplasmic reticulum; definition of the physiological role of endo-Beta-N-acetylglucosaminidase by determining with pulse-chase experiments the origin of the released glucosylated and unglucosylated polymannose-GlcNAc oligosaccharides. Furthermore information about the mechanism and subcellular site of sulfation steps will be sought from an investigation of the biosynthesis of the well-defined sulfated thyroid cell surface glycoproteins. These glycoproteins will also be the subject of studies dealing with the internalization and recycling of cell surface molecules and for this purpose their strong reactivity with B. Simplicifolia lectin will be utilized. Biosynthesis of basement membrane glycoproteins will be studied by immunochemical and radiolabeling procedures in cultured lens epithelial cells and in a kidney mRNA translation system. The effect of diabetes and the influence of glucose concentration and various hormones on the production of the basement membrane components will be evaluated.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK017477-16
Application #
3225756
Study Section
Physiological Chemistry Study Section (PC)
Project Start
1974-09-01
Project End
1989-08-31
Budget Start
1988-09-01
Budget End
1989-08-31
Support Year
16
Fiscal Year
1988
Total Cost
Indirect Cost
Name
Joslin Diabetes Center
Department
Type
DUNS #
071723084
City
Boston
State
MA
Country
United States
Zip Code
02215
Spiro, Robert G (2002) Protein glycosylation: nature, distribution, enzymatic formation, and disease implications of glycopeptide bonds. Glycobiology 12:43R-56R
Spiro, M J; Spiro, R G (2001) Release of polymannose oligosaccharides from vesicular stomatitis virus G protein during endoplasmic reticulum-associated degradation. Glycobiology 11:803-11
Spiro, M J; Spiro, R G (2000) Sulfation of the N-linked oligosaccharides of influenza virus hemagglutinin: temporal relationships and localization of sulfotransferases. Glycobiology 10:1235-42
Karaivanova, V K; Spiro, R G (2000) Effect of proteasome inhibitors on the release into the cytosol of free polymannose oligosaccharides from glycoproteins. Glycobiology 10:727-35
Zuber, C; Spiro, M J; Guhl, B et al. (2000) Golgi apparatus immunolocalization of endomannosidase suggests post-endoplasmic reticulum glucose trimming: implications for quality control. Mol Biol Cell 11:4227-40
Spiro, M J; Spiro, R G (2000) Use of recombinant endomannosidase for evaluation of the processing of N-linked oligosaccharides of glycoproteins and their oligosaccharide-lipid precursors. Glycobiology 10:521-9
Spiro, R G; Bhoyroo, V D (1998) Characterization of a spleen sulphotransferase responsible for the 6-O-sulphation of the galactose residue in sialyl-N-acetyl-lactosamine sequences. Biochem J 331 ( Pt 1):265-71
Chandra, N C; Spiro, M J; Spiro, R G (1998) Identification of a glycoprotein from rat liver mitochondrial inner membrane and demonstration of its origin in the endoplasmic reticulum. J Biol Chem 273:19715-21
Karaivanova, V K; Spiro, R G (1998) Sulphation of N-linked oligosaccharides of vesicular stomatitis and influenza virus envelope glycoproteins: host cell specificity, subcellular localization and identification of substituted saccharides. Biochem J 329 ( Pt 3):511-8
Karaivanova, V K; Luan, P; Spiro, R G (1998) Processing of viral envelope glycoprotein by the endomannosidase pathway: evaluation of host cell specificity. Glycobiology 8:725-30

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