How Glycosaminoglycans Promote Fibrillation of Salmon Calcitonin.
Glycosaminoglycans (GAGs) bind all known amyloid plaques and help store protein hormones in (acidic) granular vesicles, but the molecular mechanisms underlying these important effects are unclear. Here we investigate GAG interactions with the peptide hormone salmon calcitonin (sCT). GAGs induce fast sCT fibrillation at acidic pH and only bind monomeric sCT at acidic pH, inducing sCT helicity. Increasing GAG sulfation expands the pH range for binding. Heparin, the most highly sulfated GAG, binds sCT in the pH interval 3-7. Small angle x-ray scattering indicates that sCT monomers densely decorate and pack single heparin chains, possibly via hydrophobic patches on helical sCT. sCT fibrillates without GAGs, but heparin binding accelerates the process by decreasing the otherwise long fibrillation lag times at low pH and accelerates fibril growth rates at neutral pH. sCT·heparin complexes form β-sheet-rich heparin-covered fibrils. Solid-state NMR reveals that heparin does not alter the sCT fibrillary core around Lys(11) but makes changes to Val(8) on the exterior side of the β-strand, possibly through contacts to Lys(18) Thus GAGs significantly modulate sCT fibrillation in a pH-dependent manner by interacting with both monomeric and aggregated sCT.
From the Interdisciplinary Nanoscience Center (iNANO) and Center for Insoluble Protein Structures (inSPIN), Aarhus University, Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark, Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10C, DK-8000 Aarhus C, Denmark.
Kirsten Gade
KG
Malmos
From the Interdisciplinary Nanoscience Center (iNANO) and Center for Insoluble Protein Structures (inSPIN), Aarhus University, Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark, Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark.
Morten
M
Bjerring
From the Interdisciplinary Nanoscience Center (iNANO) and Center for Insoluble Protein Structures (inSPIN), Aarhus University, Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark.
Christian Moestrup
CM
Jessen
From the Interdisciplinary Nanoscience Center (iNANO) and Center for Insoluble Protein Structures (inSPIN), Aarhus University, Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark.
Erik Holm Toustrup
EH
Nielsen
Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10C, DK-8000 Aarhus C, Denmark.
Ebbe T
ET
Poulsen
Department of Biomedicine, Aarhus University, Wilhelm Meyers Allé 4, DK-8000 Aarhus, Denmark, and.
Gunna
G
Christiansen
From the Interdisciplinary Nanoscience Center (iNANO) and Center for Insoluble Protein Structures (inSPIN), Aarhus University, Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark, Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark.
Thomas
T
Vosegaard
From the Interdisciplinary Nanoscience Center (iNANO) and Center for Insoluble Protein Structures (inSPIN), Aarhus University, Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark.
Troels
T
Skrydstrup
Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10C, DK-8000 Aarhus C, Denmark.
Jan J
JJ
Enghild
From the Interdisciplinary Nanoscience Center (iNANO) and Center for Insoluble Protein Structures (inSPIN), Aarhus University, Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark, Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark.
Jan Skov
JS
Pedersen
From the Interdisciplinary Nanoscience Center (iNANO) and Center for Insoluble Protein Structures (inSPIN), Aarhus University, Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark, Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10C, DK-8000 Aarhus C, Denmark, dao@inano.au.dk.
Daniel E
DE
Otzen
D000818:Animals; D002116:Calcitonin / Q000737:chemistry*; D029941:Fish Proteins / Q000737:chemistry*; D006025:Glycosaminoglycans / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D019906:Nuclear Magnetic Resonance, Biomolecular; D066329:Protein Aggregates; D012474:Salmon
D029941:Fish Proteins; D006025:Glycosaminoglycans; D066329:Protein Aggregates; D002116:Calcitonin
amyloid; fibril; glycosaminoglycan; heparin; hormone; salmon calcitonin