Proximity labeling identification of plasma membrane eisosome proteins in <i>Candida albicans</i>

The ability of Candida albicans to resist stressful conditions in the host and grow invasively into tissues contributes to the virulence of this human fungal pathogen. Plasma membrane subdomains known as the MCC (membrane compartment of Can1) or eisosomes are important for these processes. MCC/eisosome domains are furrow-shaped invaginations of the plasma membrane that are about 250 nm long and 50 nm deep. To identify proteins that localize to these domains, a proximity labeling method was used in which the TurboID variant of the BirA biotin ligase was fused to Sur7 and Lsp1, 2 proteins that localize to eisosomes and are important for virulence. This resulted in biotinylation of nearby proteins, permitting their identification. Analysis of 19 candidate proteins by tagging with the green fluorescent protein identified 7 proteins that detectably overlapped with MCC/eisosomes. Deletion mutant analysis showed that one of these, a poorly studied protein known as Ker1, was important for hyphal growth in liquid culture, invasive growth into agar medium, and resistance to stress caused by copper and cell wall perturbing agents. Altogether, these approaches identified novel MCC/eisosome proteins and show that TurboID can be applied to better define the molecular mechanisms of C. albicans pathogenesis and aid in discovery of targets for novel therapeutic strategies.