Abstract
Candida albicans adhesins have amyloid-forming sequences. In Als5p, these amyloid sequences cluster cell surface adhesins to create high avidity surface adhesion nanodomains. Such nanodomains form after force is applied to the cell surface by atomic force microscopy or laminar flow. Here we report centrifuging and resuspending S. cerevisiae cells expressing Als5p led to 1.7-fold increase in initial rate of adhesion to ligand coated beads. Furthermore, mechanical stress from vortex-mixing of Als5p cells or C. albicans cells also induced additional formation of amyloid nanodomains and consequent activation of adhesion. Vortex-mixing for 60 seconds increased the initial rate of adhesion 1.6-fold. The effects of vortex-mixing were replicated in heat-killed cells as well. Activation was accompanied by increases in thioflavin T cell surface fluorescence measured by flow cytometry or by confocal microscopy. There was no adhesion activation in cells expressing amyloid-impaired Als5pV326N or in cells incubated with inhibitory concentrations of anti-amyloid dyes. Together these results demonstrated the activation of cell surface amyloid nanodomains in yeast expressing Als adhesins, and further delineate the forces that can activate adhesion in vivo. Consequently there is quantitative support for the hypothesis that amyloid forming adhesins act as both force sensors and effectors.
Highlights
Yeast cell surface adhesins, such as the Candida albicans adhesin Als5p and Saccharomyces cerevisiae flocculins Flo1p and Flo11p, mediate cell-to-cell aggregation and cell-to-surface adhesion
Mechanical extension force applied with the tip of an atomic force microscope (AFM) activates the clustering of Als5p molecules into nanodomains and the clusters propagate across the cell surface
We looked for increases in cell-to-bead adhesion and cell-to-cell aggregation of Als5pWT-expressing cells with ligand-coated beads [20]
Summary
Yeast cell surface adhesins, such as the Candida albicans adhesin Als5p and Saccharomyces cerevisiae flocculins Flo1p and Flo11p, mediate cell-to-cell aggregation and cell-to-surface adhesion. Mechanical extension force applied with the tip of an atomic force microscope (AFM) activates the clustering of Als5p (hereafter designated Als5pWT) molecules into nanodomains and the clusters propagate across the cell surface. This clustering is mediated by the amyloid-forming sequence, because the clustering response is absent from a non-amyloid-forming mutant of the protein Als5pV326N [2,4,5]. Hydrodynamic shear from laminar flow can activate the yeast surface amyloids to increase surface binding, cell-cell aggregation, and formation of mechanically robust biofilms [7] These changes are consistent with observations that C. albicans biofilms grown under flow are more extensive and include more hyphae [8]
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