title: The Human Disease-Associated Aβ Amyloid Core Sequence Forms Functional Amyloids in a Fungal Adhesin.
abstract: There is increasing evidence that many amyloids in living cells have physiological functions. On the surfaces of fungal cells, amyloid core sequences in adhesins can aggregate into 100- to 1,000-nm-wide patches to form high-avidity adhesion nanodomains on the cell surface. The nanodomains form through interactions that have amyloid-like properties: binding of amyloid dyes, perturbation by antiamyloid agents, and interaction with homologous sequences. To test whether these functional interactions are mediated by typical amyloid interactions, we substituted an amyloid core sequence, LVFFA, from human Aβ protein for the native sequence IVIVA in the 1,419-residue Candida albicans adhesin Als5p. The chimeric protein formed cell surface nanodomains and mediated cellular aggregation. The native sequence and chimeric adhesins responded similarly to the amyloid dye thioflavin T and to amyloid perturbants. However, unlike the native protein, the nanodomains formed by the chimeric protein were not force activated and formed less-robust aggregates under flow. These results showed the similarity of amyloid interactions in the amyloid core sequences of native Als5p and Aβ, but they also highlighted emergent properties of the native sequence. Also, a peptide composed of the Aβ amyloid sequence flanked by amino acids from the adhesin formed two-dimensional sheets with sizes similar to the cell surface patches of the adhesins. These results inform an initial model for the structure of fungal cell surface amyloid nanodomains.
  
  
  OBJECTIVE
  Protein amyloid aggregates are markers of neurodegenerative diseases such as Alzheimer's and Parkinsonism. Nevertheless, there are also functional amyloids, including biofilm-associated amyloids in bacteria and fungi. In fungi, glycoprotein adhesins aggregate into cell surface patches through amyloid-like interactions, and the adhesin clustering strengthens cell-cell binding. These fungal surface amyloid nanodomains mediate biofilm persistence under flow, and they also moderate host inflammatory responses in fungal infections. To determine whether the amyloid-like properties of fungal surface nanodomains are sequence specific, we ask whether a disease-associated amyloid core sequence has properties equivalent to those of the native sequence in a fungal adhesin. A chimeric adhesin with an amyloid sequence from the Alzheimer's disease protein Aβ instead of its native sequence effectively clustered the adhesins on the cell surface, but it showed a different response to hydrodynamic shear. These results begin an analysis of the sequence dependence for newly discovered activities for fungal surface amyloid nanodomains.
authors.affiliation: Biology Department, Brooklyn College, City University of New York, Brooklyn, New York, USA Biology PhD Program, The Graduate Center, City University of New York, New York, New York, USA.
authors.forename: Rachele D
authors.initials: RD
authors.lastname: Rameau
authors.affiliation: Biology Department, Brooklyn College, City University of New York, Brooklyn, New York, USA Biology PhD Program, The Graduate Center, City University of New York, New York, New York, USA.
authors.forename: Desmond N
authors.initials: DN
authors.lastname: Jackson
authors.affiliation: Institute of Life Sciences, Université Catholique de Louvain, Louvain-la-Neuve, Belgium.
authors.forename: Audrey
authors.initials: A
authors.lastname: Beaussart
authors.affiliation: Institute of Life Sciences, Université Catholique de Louvain, Louvain-la-Neuve, Belgium.
authors.forename: Yves F
authors.initials: YF
authors.lastname: Dufrêne
authors.affiliation: Biology Department, Brooklyn College, City University of New York, Brooklyn, New York, USA Biology PhD Program, The Graduate Center, City University of New York, New York, New York, USA plipke@brooklyn.cuny.edu.
authors.forename: Peter N
authors.initials: PN
authors.lastname: Lipke
mesh_terms: D016229:Amyloid beta-Peptides / Q000235:genetics* / Q000378:metabolism*; D002176:Candida albicans / Q000166:cytology / Q000235:genetics / Q000502:physiology; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000235:genetics* / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D008853:Microscopy; D055503:Protein Multimerization; D011993:Recombinant Fusion Proteins / Q000235:genetics* / Q000378:metabolism*
chemical_list: C109455:ALA1 protein, Candida albicans; D016229:Amyloid beta-Peptides; D015815:Cell Adhesion Molecules; D005656:Fungal Proteins; D011993:Recombinant Fusion Proteins