Discovery of Cercosporamide, a Known Antifungal Natural Product, as a Selective Pkc1 Kinase Inhibitor through High-Throughput Screening

The Pkc1-mediated cell wall integrity-signaling pathway is highly conserved in fungi and is essential for fungal growth. We thus explored the potential of targeting the Pkc1 protein kinase for developing broad-spectrum fungicidal antifungal drugs through a Candida albicans Pkc1-based high-throughput screening. We discovered that cercosporamide, a broad-spectrum natural antifungal compound, but previously with an unknown mode of action, is actually a selective and highly potent fungal Pkc1 kinase inhibitor. This finding provides a molecular explanation for previous observations in which Saccharomyces cerevisiae cell wall mutants were found to be highly sensitive to cercosporamide. Indeed, S. cerevisiae mutant cells with reduced Pkc1 kinase activity become hypersensitive to cercosporamide, and this sensitivity can be suppressed under high-osmotic growth conditions. Together, the results demonstrate that cercosporamide acts selectively on Pkc1 kinase and, thus, they provide a molecular mechanism for its antifungal activity. Furthermore, cercosporamide and a β-1,3-glucan synthase inhibitor echinocandin analog, by targeting two different key components of the cell wall biosynthesis pathway, are highly synergistic in their antifungal activities. The synergistic antifungal activity between Pkc1 kinase and β-1,3-glucan synthase inhibitors points to a potential highly effective combination therapy to treat fungal infections

Development and calibration of a passive sampler for perfluorinated alkyl carboxylates and sulfonates in water

Perfluorinated chemicals (PFCs) are emerging environmental contaminants with a global distribution. Due to their moderate water solubility, the majority of the environmental burden is assumed to be in the water phase. This work describes the application of the first passive sampler for the quantitative assessment of concentrations of perfluorinated alkylcarboxylates (PFCAs) and sulfonates (PFSAs) in water. The sampler is based on a modified Polar Organic Chemical Integrative Sampler (POCIS) with a weak anion exchange sorbent as a receiving phase. Sampling rates were between 0.16 and 0.37 L d(-1), and the duration of the kinetic sampling stage was between 2.2 and 13 d. A field deployment in the most urbanized estuary in Australia (Sydney Harbour) showed trace level concentrations from passive samplers (0.1-12 ng L-1), in good agreement with parallel grab sampling (0.2-16 ng L-1). A separate field comparison of the modified POCIS with standard POCIS suggests the latter may have application for PFC sampling, but with a more limited range of analytes than the modified POCIS which contains a sorbent with a mixed mode of action