Ellagic Acid Combined with Tacrolimus Showed Synergistic Cell Growth Inhibition in Fission Yeast

Calcineurin (CN) is a conserved Ca²⁺-calmodulin activated protein phosphatase, which plays important roles in immune regulation, cardiac hypertrophy, and apoptosis in humans. In pathogenic fungi, CN is essential for stress survival, sexual development, and virulence. The immunosuppressant tacrolimus (FK506) is a specific inhibitor of CN in humans and fungi including nonpathogenic fission yeast. Although calcineurin inhibition by FK506 or CN deletion in fission yeast does not induce growth defects, treatment with some anti-fungal drugs such as micafungin and valproic acid, induced synthetic lethality with calcineurin inhibition. Here, we searched for the compounds that induce synthetic growth defects with CN inhibition in fission yeast. We found that ellagic acid (EA) preferentially induced growth inhibition in CN deletion cells. Consistently, co-treatment with EA and FK506 induced severe growth inhibition in the wild-type cells, whereas neither of the single treatment with each compound did so. Moreover, deletion of the calcineurin-regulated transcription factor Prz1 also induced a marked EA sensitivity. Intriguingly, EA also enhanced the growth inhibitory effect of other anti-fungal drugs, including micafungin and miconazole. Thus, our data suggesting the synergistic growth inhibitory effect of the calcineurin inhibitor FK506 and EA may be useful to understand the mechanism to overcome the antifungal resistance.