Overall Sulfation of Heparan Sulfate from Pancreatic Islet β-TC3 Cells Increases Maximal Fibril Formation but Does Not Determine Binding to the Amyloidogenic Peptide Islet Amyloid Polypeptide

• Published in: The Journal of biological chemistry 2012-10, Vol.287 (44), p.37154-37164
• Main Authors: Hull, Rebecca L., Peters, Michael J., Perigo, Susan Potter, Chan, Christina K., Wight, Thomas N., Kinsella, Michael G.
• Format: Article
• Language: English
• Subjects: Amyloid; Amyloid - chemistry; Animals; Benzothiazoles; Beta Cell; Carbohydrate Conformation; Cell Line; Chromatography, Gel; Culture Media, Conditioned; Diabetes; Fluorescent Dyes - chemistry; Glycobiology and Extracellular Matrices; Heparan Sulfate; Heparin Lyase - chemistry; Heparitin Sulfate - chemistry; Heparitin Sulfate - metabolism; Humans; Immobilized Proteins - chemistry; Insulin-Secreting Cells - metabolism; Islet; Islet Amyloid Polypeptide - chemistry; Mice; Nitrous Acid - chemistry; Polysaccharide-Lyases - chemistry; Protein Binding; Protein Multimerization; Proteoglycans - chemistry; Proteoglycans - isolation & purification; Thiazoles - chemistry
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M112.409847

Islet amyloid, a pathologic feature of type 2 diabetes, contains the islet β-cell peptide islet amyloid polypeptide (IAPP) as its unique amyloidogenic component. Islet amyloid also contains heparan sulfate proteoglycans (HSPGs) that may contribute to amyloid formation by binding IAPP via their heparan sulfate (HS) chains. We hypothesized that β-cells produce HS that bind IAPP via regions of highly sulfated disaccharides. Unexpectedly, HS from the β-cell line β-TC3 contained fewer regions of highly sulfated disaccharides compared with control normal murine mammary gland (NMuMG) cells. The proportion of HS that bound IAPP was similar in both cell lines (∼65%). The sulfation pattern of IAPP-bound versus non-bound HS from β-TC3 cells was similar. In contrast, IAPP-bound HS from NMuMG cells contained frequent highly sulfated regions, whereas the non-bound material demonstrated fewer sulfated regions. Fibril formation from IAPP was stimulated equally by IAPP-bound β-TC3 HS, non-bound β-TC3 HS, and non-bound NMuMG HS but was stimulated to a greater extent by the highly sulfated IAPP-bound NMuMG HS. Desulfation of HS decreased the ability of both β-TC3 and NMuMG HS to stimulate IAPP maximal fibril formation, but desulfated HS from both cell types still accelerated fibril formation relative to IAPP alone. In summary, neither binding to nor acceleration of fibril formation from the amyloidogenic peptide IAPP is dependent on overall sulfation in HS synthesized by β-TC3 cells. This information will be important in determining approaches to reduce HS-IAPP interactions and ultimately prevent islet amyloid formation and its toxic effects in type 2 diabetes. Background: Stimulation of amyloid fibril formation by heparan sulfate is likely mediated by the extent of sulfation. Results: Islet β-cell heparan sulfate is poorly sulfated but still binds islet amyloid polypeptide (IAPP) and accelerates fibril formation. Conclusion: The degree of sulfation does not determine all aspects of heparan sulfate-mediated amyloid fibril formation. Significance: This information will be important for designing amyloid inhibitors targeting peptide-heparan sulfate interactions.