Reduced Cdc14 phosphatase activity impairs septation, hyphal differentiation and pathogenesis and causes echinocandin hypersensitivity inCandida albicans

Abstract

The Cdc14 phosphatase family is highly conserved in fungi. In Saccharomyces cerevisiae, Cdc14 is essential for down-regulation of cyclin-dependent kinase activity at mitotic exit. However, this essential function is not broadly conserved and requires a small fraction of normal Cdc14 activity. It remains unclear what fungal Cdc14 functions require high Cdc14 activity. We identified an invariant motif in the disordered C-terminal tail of fungal Cdc14 enzymes that is required for full enzyme activity. Mutation of this motif reduced Cdc14 catalytic rate and provided a tool for studying the biological significance of high Cdc14 activity. A S. cerevisiae strain expressing the reduced-activity hypomorphic mutant allele (cdc14hm) as the sole source of Cdc14 exhibited an unexpected sensitivity to cell wall stresses, including chitin-binding compounds and echinocandin antifungal drugs. Sensitivity to echinocandins was also observed in Schizosaccharomyces pombe and Candida albicans strains lacking CDC14, suggesting this phenotype reflects a conserved function of Cdc14 orthologs in mediating fungal cell wall integrity. In C. albicans, the orthologous cdc14hm allele was sufficient to elicit echinocandin hypersensitivity and perturb cell wall integrity signaling. It also caused striking abnormalities in septum structure and the same cell separation and hyphal differentiation phenotypes previously observed with cdc14 gene deletions. Since hyphal differentiation is important for C. albicans pathogenesis, we assessed the effect of reducing Cdc14 activity on virulence in Galleria mellonella and mouse models of invasive candidiasis. Partial reduction in Cdc14 activity via cdc14hm mutation severely impaired C. albicans virulence in both assays. Our results reveal that high Cdc14 activity promotes fungal cell wall integrity and, in C. albicans, is needed to orchestrate septation and hyphal differentiation, and for pathogenesis. Cdc14 may therefore be worth future exploration as an antifungal drug target.

Rapid, efficient auxin-inducible protein degradation inCandidapathogens

“…Total protein extracts were prepared as described (Milholland et al, 2022). Proteins were separated on 10% tris-glycine SDS-PAGE gels, transferred to 0.45 µm nitrocellulose membranes (Bio-Rad) and probed overnight at 4°C with mouse anti-HA (1:5,000; Sigma-Aldrich, 12CA5), rabbit anti-V5 (1:5,000; Invitrogen, MA5-15253), mouse anti-c-Myc (1:2,000-1:5,000; Sigma-Aldrich, 9E10), or rabbit anti-PSTAIR (1:5,000; Millipore-Sigma, 06-923).…”

“…The two CDC14-AID*/Δ samples are independent transformants from the degron tag integration. The cdc14 hm allele is our previously characterized hypomorphic mutant with reduced catalytic activity (Milholland et al, 2022). B) The indicated C. albicans strains were grown embedded in YPS agar with or without 150 nM 5-Ad-IAA at 30 °C for 4 days and colonies imaged with a dissecting scope (left) or Cytation 1 imaging plate reader with 4x brightfield objective (right).…”