Candida Infection Biology – fungal armoury, battlefields ... - FINSysB

Force-dependent activation of functional amyloid domains
increases cell adhesion in C. albicans
Peter N. Lipke 1 , David Alsteens 2 , Cho Tan 1 , Desmond N. Jackson 1 , Caleen
B. Ramsook 1 , Yves F. Dufrêne 2 , and Melissa C. Garcia 1
1 Department of Biology, Brooklyn College of the City University of New York; 2 Institute of
Condensed Matter, Université catholique de Louvain, Louvain-le-Neuve, Belgium
Yeast cell adhesion molecules encoded by diverse gene families have conserved
amyloid-forming sequences, and amyloid formation potentiates cell-cell interactions
(Ramsook et al., 2010 Euk. Cell 9:393-404 ; Alsteens et al., 2010 PNAS 107:20744-
9; Garcia et al., 2011 PLoS ONE 6: e17632. doi:10.1371/journal.pone.0017632 ).
Amyloid formation clusters the cell adhesion molecules, and increases cell-cell
binding by clustering of active sites in the same way that multivalence of antibodies
increases avidity relative to affinity of each site.
We show that amyloid formation is initiated by extension force, and results in
formation of nm-scale amyloid domains on the surface of the cell, with different
protein domains playing distinct roles to facilitate amyloid formation. Atomic force
microscopy of single molecules in situ unfolds successive domains in the Candida
albicans Als adhesins. This unfolding triggers local amyloid formation and
subsequent propagation of amyloid patches around the entire cell surface. Amyloid
formation is accompanied by activation of strong cell-cell and cell-substrate
adhesion. Both amyloid formation and activation of adhesion are inhibited by antiamyloid
dyes and peptides. In addition, a single site mutation in the amyloid core
sequence of Als5p abrogates amyloid formation and activation of adhesion,
although the mutant protein is well-folded and maintains in vitro binding activity.
Amyloid formation is also triggered by forces developed between cells during
assays or by prolonged vortex mixing of cells. The various protein domains in Als
proteins synergize to promote this force-induced amyloid formation. The
consequence is formation of nanoscale patches of amyloid on the cell surface to
potentiate cell interactions by formation of multiple intercellular bonds.
Supported by NIH SCORE grant SC1 GM083756
62