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Heparin Promotes the Rapid Fibrillization of a Peptide with Low Intrinsic Amyloidogenicity

DOI: 10.1021/bi401231u DOI Help

Authors: Jill Madine (University of Liverpool) , Hannah Davies (University of Liverpool) , Eleri Hughes (Lancaster University) , David Middleton (University of Liverpool)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Biochemistry , VOL 52 (50) , PAGES 8984 - 8992

State: Published (Approved)
Published: December 2013
Diamond Proposal Number(s): 509088

Abstract: Amyloid deposits in vivo are complex mixtures composed of protein fibrils and nonfibrillar components, including polysaccharides of the glycosaminoglycan (GAG) class. It has been widely documented that GAGs influence the initiation and progress of self-assembly by several disease-associated amyloidogenic proteins and peptides in vitro. Here we investigated whether the GAG heparin can serve as a cofactor to induce amyloid-like fibril formation in a peptide predicted to have a weak propensity to aggregate and not associated with amyloid disorders. We selected the 23-residue peptide PLB(1–23), which corresponds to the acetylated cytoplasmic domain of the phospholamban transmembrane protein. PLB(1–23) remains unfolded in aqueous solution for >24 h and does not bind thioflavin T over this time period, in agreement with computer predictions that the peptide has a very low intrinsic amyloidogenicity. In the presence of low-molecular mass (5 kDa) heparin, which binds PLB(1–23) with micromolar affinity, the peptide undergoes spontaneous and rapid assembly into amyloid-like fibrils, the effect being more pronounced at pH 5.5 than at pH 7.4. At the lower pH, peptide aggregation is accompanied by a transition to a ?-sheet rich structure. These results are consistent with the polyanionic heparin serving as a scaffold to enhance aggregation by aligning the peptide molecules in the correct orientation and with the appropriate periodicity. PLB(1–23) is toxic to cells when added in isolation, and promotion of fibril formation by heparin can reduce the toxicity of this peptide, consistent with the notion that amyloid-like fibrils represent a benign end stage of fibrillization. This work provides insight into the role that heparin and other glycosaminoglycans may play in amyloid formation and provides therapeutic avenues targeting the reduction of cytotoxicity of species along the amyloid formation pathway.

Journal Keywords: Amyloid; Aggregation; Heparin

Subject Areas: Biology and Bio-materials, Chemistry


Instruments: B23-Circular Dichroism

Other Facilities: No

Added On: 20/03/2014 16:46

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