Dissociation of a BRICHOS trimer into monomers leads to increased inhibitory effect on A beta 42 fibril formation

Abstract

The BRICHOS domain is associated with human amyloid disease, and it efficiently prevents amyloid fibril formation of the amyloid beta-peptide (A beta) 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 Set to Arg mutation expected to interfere with trimer formation. This leads to increased capacity to delay A beta(42) fibril formation. Cross-linking of the BRICHOS trimer with glutaraldehyde, in contrast, renders it unable to affect A beta(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 A beta(42) fibril formation. These results indicate that modulation of the accessibility of the substrate-binding site is a means to regulate BRICHOS activity. (C) 2015 Elsevier B.V. All rights reserved.

Keywords

Molecular chaperone; Alzheimer's disease; Protein structure

Published in

BBA - Proteins and Proteomics
2015, volume: 1854, number: 8, pages: 835-843
Publisher: ELSEVIER SCIENCE BV

SLU Authors

• Hermansson, Erik

  • Karolinska Institute

• Johansson, Jan

  • Department of Animal Biosciences, Swedish University of Agricultural Sciences
    
  • Tallinn University

UKÄ Subject classification

Biochemistry and Molecular Biology

Publication identifier

• DOI: https://doi.org/10.1016/j.bbapap.2015.04.005

Permanent link to this page (URI)

https://res.slu.se/id/publ/75573