BRICHOS domains efficiently delay fibrillation of amyloid β-peptide.
Amyloid diseases such as Alzheimer, Parkinson, and prion diseases are associated with a specific form of protein misfolding and aggregation into oligomers and fibrils rich in β-sheet structure. The BRICHOS domain consisting of ∼100 residues is found in membrane proteins associated with degenerative and proliferative disease, including lung fibrosis (surfactant protein C precursor; pro-SP-C) and familial dementia (Bri2). We find that recombinant BRICHOS domains from Bri2 and pro-SP-C prevent fibril formation of amyloid β-peptides (Aβ(40) and Aβ(42)) far below the stoichiometric ratio. Kinetic experiments show that a main effect of BRICHOS is to prolong the lag time in a concentration-dependent, quantitative, and reproducible manner. An ongoing aggregation process is retarded if BRICHOS is added at any time during the lag phase, but it is too late to interfere at the end of the process. Results from circular dichroism and NMR spectroscopy, as well as analytical size exclusion chromatography, imply that Aβ is maintained as an unstructured monomer during the extended lag phase in the presence of BRICHOS. Electron microscopy shows that although the process is delayed, typical amyloid fibrils are eventually formed also when BRICHOS is present. Structural BRICHOS models display a conserved array of tyrosine rings on a five-stranded β-sheet, with inter-hydroxyl distances suited for hydrogen-bonding peptides in an extended β-conformation. Our data imply that the inhibitory mechanism is reliant on BRICHOS interfering with molecular events during the lag phase.
Department of Anatomy, Physiology, and Biochemistry, Swedish University of Agricultural Sciences, The Biomedical Centre, 751 23 Uppsala, Sweden.
Hanna
H
Willander
Jenny
J
Presto
Glareh
G
Askarieh
Henrik
H
Biverstål
Birgitta
B
Frohm
Stefan D
SD
Knight
Jan
J
Johansson
Sara
S
Linse
D000682:Amyloid / Q000737:chemistry* / Q000378:metabolism; D016229:Amyloid beta-Peptides / Q000737:chemistry* / Q000378:metabolism; D002942:Circular Dichroism; D006801:Humans; D008958:Models, Molecular; D019636:Neurodegenerative Diseases / Q000378:metabolism; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000737:chemistry* / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011658:Pulmonary Fibrosis / Q000378:metabolism
D000682:Amyloid; D016229:Amyloid beta-Peptides; D010446:Peptide Fragments; C078592:amyloid beta-protein (1-40); C075222:amyloid beta-protein (1-42)