<p>Heparan sulfate (HS) is a linear polysaccharide, located on the surface and in the extracellular matrix of most cells, that regulates functions of numerous proteins. HS-protein interaction is mainly mediated by sulfate groups found in N-sulfated (NS) regions of the HS, but may also involve rare HS substituents such as N-unsubstituted glucosamine (GlcNH<sub>2</sub>) residues. The location of GlcNH<sub>2</sub> in an HS-epitope recognized by the monoclonal antibody 10E4, that specifically stains the prion lesions in scrapie-infected murine brain, suggests an involvement of GlcNH<sub>2</sub> in prion disease and other amyloid-related disorders. HS in general is strongly associated with amyloidosis, including Alzheimer’s disease (AD). Therefore, the aims of this thesis were to structurally characterize GlcNH<sub>2</sub>-containing HS sequences found in native tissues, to further study HS epitopes recognized by 10E4, and to investigate the possible role(s) of GlcNH<sub>2</sub> and other HS structures in binding to amyloid β peptide (Aβ) (core material in AD plaque lesions, also stained by 10E4).</p><p>The GlcNH<sub>2</sub> content (0.7-4% of total disaccharide units) varied between HS from different tissues. Most GlcNH<sub>2</sub> units were found in poorly modified N-acetylated (NA-) or NA/NS-domains, located toward the polysaccharide-protein linkage region.</p><p>Binding of human cerebral cortex HS to Aβ(1–40) monomers requires N-, 2- and 6-O-sulfation of HS, while binding to Aβ fibrils requires N- and 2-O-sulfation only. GlcNH<sub>2</sub> units do not appreciably contribute to interaction with Aβ. Aβ fibril-binding HS domains also bind to fibroblast growth factor 2 (FGF-2), indicating that Aβ (neurotoxic) and FGF-2 (neuroprotective) may compete for common binding sites in HS. However, Aβ had no effect on FGF-2-induced MAPK signaling in NIH 3T3 fibroblasts.</p><p>Continued studies on 10E4-antigenic HS epitope(s) showed that binding of 10E4 to the previously identified antigenic tetrasaccharide, ∆UA-GlcNH<sub>2</sub>-GlcA-GlcNAc, requires the nonreducing hexuronic acid (∆UA) to be 4,5 unsaturated (induced by lyase cleavage), and thus is artificial. Further studies are needed to clarify the potential involvement of GlcNH<sub>2</sub> in 10E4-recognition of the native HS epitope(s).</p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:uu-3866 |
| Date | January 2003 |
| Creators | Westling, Camilla |
| Publisher | Uppsala University, Department of Medical Biochemistry and Microbiology, Uppsala : Acta Universitatis Upsaliensis |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Doctoral thesis, comprehensive summary, text |
| Relation | Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, 0282-7476 ; 1313 |
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