title: Dissociation of a BRICHOS trimer into monomers leads to increased inhibitory effect on Aβ42 fibril formation.
abstract: The BRICHOS domain is associated with human amyloid disease, and it efficiently prevents amyloid fibril formation of the amyloid β-peptide (Aβ) in vitro and in vivo. Recombinant human prosurfactant protein C (proSP-C) BRICHOS domain forms a homotrimer as observed by x-ray crystallography, analytical ultracentrifugation, native polyacrylamide gel electrophoresis, analytical size exclusion chromatography and electrospray mass spectrometry. It was hypothesized that the trimer is an inactive storage form, as a putative substrate-binding site identified in the monomer, is buried in the subunit interface of the trimer. We show here increased dissociation of the BRICHOS trimer into monomers, by addition of detergents or of bis-ANS, known to bind to the putative substrate-binding site, or by introducing a Ser to Arg mutation expected to interfere with trimer formation. This leads to increased capacity to delay Aβ(42) fibril formation. Cross-linking of the BRICHOS trimer with glutaraldehyde, in contrast, renders it unable to affect Aβ(42) fibril formation. Moreover, proSP-C BRICHOS expressed in HEK293 cells is mainly monomeric, as detected by proximity ligation assay. Finally, proteolytic cleavage of BRICHOS in a loop region that is cleaved during proSP-C biosynthesis results in increased capacity to delay Aβ(42) fibril formation. These results indicate that modulation of the accessibility of the substrate-binding site is a means to regulate BRICHOS activity.
authors.affiliation: Karolinska Institutet, Department of NVS, Center for Alzheimer Research, Division of Neurogeriatrics, 141 57 Huddinge, Sweden. Electronic address: henrik.biverstal@ki.se.
authors.forename: Henrik
authors.initials: H
authors.lastname: Biverstål
authors.affiliation: Karolinska Institutet, Department of NVS, Center for Alzheimer Research, Division of Neurogeriatrics, 141 57 Huddinge, Sweden.
authors.forename: Lisa
authors.initials: L
authors.lastname: Dolfe
authors.affiliation: Karolinska Institutet, Department of NVS, Center for Alzheimer Research, Division of Neurogeriatrics, 141 57 Huddinge, Sweden.
authors.forename: Erik
authors.initials: E
authors.lastname: Hermansson
authors.affiliation: Karolinska Institutet, Department of NVS, Center for Alzheimer Research, Division of Neurogeriatrics, 141 57 Huddinge, Sweden.
authors.forename: Axel
authors.initials: A
authors.lastname: Leppert
authors.affiliation: Karolinska Institutet, Department of NVS, Center for Alzheimer Research, Division of Neurogeriatrics, 141 57 Huddinge, Sweden.
authors.forename: Mara
authors.initials: M
authors.lastname: Reifenrath
authors.affiliation: Karolinska Institutet, Department of NVS, Center for Alzheimer Research, Division of Neurogeriatrics, 141 57 Huddinge, Sweden.
authors.forename: Bengt
authors.initials: B
authors.lastname: Winblad
authors.affiliation: Karolinska Institutet, Department of NVS, Center for Alzheimer Research, Division of Neurogeriatrics, 141 57 Huddinge, Sweden.
authors.forename: Jenny
authors.initials: J
authors.lastname: Presto
authors.affiliation: Karolinska Institutet, Department of NVS, Center for Alzheimer Research, Division of Neurogeriatrics, 141 57 Huddinge, Sweden; Department of Anatomy, Physiology and Biochemistry, The Biomedical Centre, Swedish University of Agricultural Sciences, Box 575, 751 23 Uppsala, Sweden; Institute of Mathematics and Natural Sciences, Tallinn University, Narva mnt 25, Tallinn 101 20, Estonia.
authors.forename: Jan
authors.initials: J
authors.lastname: Johansson
mesh_terms: D016229:Amyloid beta-Peptides / Q000737:chemistry / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism*; D066263:Protein Aggregation, Pathological / Q000378:metabolism*; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D037721:Pulmonary Surfactant-Associated Protein C / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: D016229:Amyloid beta-Peptides; D010446:Peptide Fragments; D037721:Pulmonary Surfactant-Associated Protein C; D011994:Recombinant Proteins; C489679:SFTPC protein, human; C075222:amyloid beta-protein (1-42)
keywords: Alzheimer's disease; Molecular chaperone; Protein structure