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Sulfatide promotes the folding of proinsulin, preserves insulin crystals, and mediates its monomerization

Research output: Contribution to journalArticle

Author(s)

  • T Osterbye
  • K H Jorgensen
  • P Fredman
  • J Tranum-Jensen
  • A Kaas
  • J Brange
  • J L Whittingham
  • K Buschard

Department/unit(s)

Publication details

JournalGLYCOBIOLOGY
DatePublished - Jun 2001
Issue number6
Volume11
Number of pages7
Pages (from-to)473-479
Original languageEnglish

Abstract

Sulfatide is a glycolipid that has been associated with insulin-dependent diabetes mellitus, It is present in the islets of Langerhans and follows the same intracellular route as insulin. However, the role of sulfatide in the beta cell has been unclear. Here we present evidence suggesting that sulfatide promotes the folding of reduced proinsulin, indicating that sulfatide possesses molecular chaperone activity. Sulfatide associates with insulin by binding to the insulin domain AS-BIG and most likely by interacting with the hydrophobic side chains of the dimer-forming part of the insulin B-chain, Sulfatide has a dual effect on insulin. It substantially reduces deterioration of insulin hexamer crystals at pH 5.5, conferring stability comparable to those in beta cell granules. Sulfatide also mediates the conversion of insulin hexamers to the biological active monomers at neutral pH, the pH at the beta-cell surface. Finally, we report that inhibition of sulfatide synthesis with chloroquine and fumonisine B1 leads to inhibition of insulin granule formation in vivo. Our observations suggest that sulfatide plays a key role in the folding of proinsulin, in the maintenance of insulin structure, and in the monomerization process.

    Research areas

  • sulfatide, insulin, molecular chaperone, islets of Langerhans, secretory granules, MOLECULAR CHAPERONES, DIABETES-MELLITUS, SECRETORY GRANULE, BETA-CELLS, PROTEIN, ANTIBODIES, LANGERHANS, ISLETS, MATURATION, TRANSPORT

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