The human pathogenic fungus Candida albicans causes severe invasive candidiasis. C. albicans infection requires the virulence factor Candidalysin (CL). CL damages the plasma membrane to facilitate the infection of target cells. However, the molecular mechanism that CL uses to damage membranes is poorly understood. Here we employ a combination of biophysical, microscopy, and cell biology methods to reveal that CL forms membrane pores using a unique molecular mechanism. We observed that CL readily assembles into linear polymers in solution. The basic unit in polymer formation is a CL octamer, which is sequentially added into a string configuration. Finally, the linear polymers close into a loop. Our data indicate that CL rings loops can spontaneously insert into the membrane to establish membrane pores. The identification of CL mutations that either promote or inhibit formation of polymers in solution allowed to establish the notion that polymerization in solution is a necessary step for membrane damage. Analysis of thousands of CL pores by atomic force microscopy revealed the co-existence of simple pores with more complex pores showing protrusions. Imaging and modeling indicate that the two types of pores are formed by CL molecules in alternate conformations. We propose that this structural rearrangement represents a maturation mechanism that stabilizes pore formation, and might achieve more robust cellular damage. The results show that CL uses a previously unknown mechanism to damage membranes, whereby pre-assembly of CL loops in solution leads to formation of membrane pores. Our investigation not only unravels a new paradigm for pore formation, but additionally identifies CL polymerization as a novel therapeutic target to treat candidiasis.

C. albicans virulence factor Candidalysin must assemble into polymers in solution to form the membrane pores

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.