Global disruption of cell cycle progression and nutrient response by the antifungal agent amiodarone

The antiarrhythmic drug amiodarone has fungicidal activity against a broad range of fungi. In Saccharomyces cerevisiae, it elicits an immediate influx of Ca²⁺ followed by mitochondrial fragmentation and eventual cell death. To dissect the mechanism of its toxicity, we assessed the transcriptional response of S. cerevisiae to amiodarone by DNA microarray. Consistent with the drug-induced calcium burst, more than half of the differentially transcribed genes were induced by high levels of CaCl₂. Amiodarone also caused rapid nuclear accumulation of the calcineurin-regulated Crz1. The majority of genes induced by amiodarone within 10 min were involved in utilization of alternative carbon and nitrogen sources and in mobilizing energy reserves. The similarity to nutrient starvation responses seen in stationary phase cells, rapamycin treatment, and late stages of shift to diauxic conditions and nitrogen depletion suggests that amiodarone may interfere with nutrient sensing and regulatory networks. Transcription of a set of nutrient-responsive genes was affected by amiodarone but not CaCl₂, indicating that activation of the starvation response was independent of Ca²⁺. Genes down-regulated by amiodarone were involved in all stages of cell cycle control. A moderate dose of amiodarone temporarily delayed cell cycle progression at G₁, S, and G₂/M phases, with the Swe1-mediated delay in G ₂/Mphase being most prominent in a calcineurin-dependent manner. Overall, the transcriptional responses to amiodarone revealed by this study were found to be distinct from other classes of antifungals, including the azole drugs, pointing toward a novel target pathway in combating fungal pathogenesis.