Biophysical Society Conference | Tahoe 2022

Molecular Biophysics of Membranes

Poster Abstracts

39-POS Board 10 THE CANDIDA ALBICANS VIRULENCE FACTOR CANDIDALYSIN POLYMERIZES IN SOLUTION TO FORM MEMBRANE PORES AND DAMAGE EPITHELIAL CELLS Charles Russell 1 ; Katherine Schaeffer 2 ; Jordan Pyron 1 ; Amber Gray 3 ; Thanh Do 3 ; Francisco N Barrera 1 ; Gavin King 2 ; 1 University of Tennessee, Biochemistry & Cellular and Molecular Biology, Knoxville, TN, USA 2 University of Missouri, Physics and Astronomy, Columbia, MO, USA 3 University of Tennessee, Chemistry, Knoxville, TN, USA Pathogenic Candida albicans is responsible for infections resulting in high mortality to vulnerable populations. Recently, a novel virulent peptide named Candidalysin (CL) was found to be required for infection. It was proposed that CL promotes infection by permeabilizing cell membranes. However, the specific mechanism by which this occurs is unknown. Atomic force microscopy (AFM) imaging of lipid bilayers treated with CL revealed various pore populations, suggesting that membrane disruption occurs through pore formation. We observed the existence of two types of pores that seem to exist as structural intermediates to efficiently confer cellular toxicity. In the absence of a bilayer, however, CL readily oligomerizes into long chains that form closed-loop structures. Biophysical techniques such as mass photometry, analytical ultracentrifugation, ion-mobility mass spectrometry, and fluorescent dye-release assays suggest that oligomerization in buffer is a prerequisite for pore formation. We tested this by conducting scanning mutagenesis on CL to identify residues necessary for self-assembly and membrane disruption. The effects of these gain and loss-of-function variants in vitro are recapitulated in epithelial cells. Our approach led us to propose a novel mechanism of pore formation that deviates from the mechanisms of other pore forming proteins. CL octamers oligomerize into long chains that eventually close into loops. CL loops insert into the membrane and undergo a conformational change to form a toxic pore structure. Characterizing this model of pore formation has provided insight into unique protein-membrane interactions that will inform innovative avenues to treat C. albicans infections.

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