Calcium-Activated-Calcineurin Reduces the In Vitro and In Vivo Sensitivity of Fluconazole to Candida albicans via Rta2p

Due to the emergence of drug-resistance, first-line therapy with fluconazole (FLC) increasingly resulted in clinical failure for the treatment of candidemia. Our previous studies found that in vitro RTA2 was involved in the calcineurin-mediated resistance to FLC in C. albicans. In this study, we found that calcium-activated-calcineurin significantly reduced the in vitro sensitivity of C. albicans to FLC by blocking the impairment of FLC to the plasma membrane via Rta2p. Furthermore, we found that RTA2 itself was not involved in C. albicans virulence, but the disruption of RTA2 dramatically increased the therapeutic efficacy of FLC in a murine model of systemic candidiasis. Conversely, both re-introduction of one RTA2 allele and ectopic expression of RTA2 significantly reduced FLC efficacy in a mammalian host. Finally, we found that calcium-activated-calcineurin, through its target Rta2p, dramatically reduced the efficacy of FLC against candidemia. Given the critical roles of Rta2p in controlling the efficacy of FLC, Rta2p can be a potential drug target for antifungal therapies.

由于耐药性的出现，临床采用氟康唑（fluconazole, FLC）的一线治疗方案在念珠菌血症的治疗中愈发频繁地遭遇失败。我们既往的研究表明，体外实验中RTA2基因参与了白色念珠菌（Candida albicans, C. albicans）钙调磷酸酶（calcineurin）介导的氟康唑耐药过程。本研究中，我们发现钙激活的钙调磷酸酶可通过Rta2p阻断氟康唑对细胞膜的损伤，显著降低白色念珠菌在体外对氟康唑的敏感性。进一步研究显示，RTA2基因本身并不参与白色念珠菌的致病过程，但敲除RTA2基因可显著提升氟康唑在系统性念珠菌病小鼠模型中的治疗疗效。与之相反，重新导入一个RTA2等位基因或异位表达RTA2，均可显著降低氟康唑在哺乳动物宿主体内的治疗疗效。最终我们证实，钙激活的钙调磷酸酶通过其靶蛋白Rta2p，大幅削弱了氟康唑对抗念珠菌血症的疗效。鉴于Rta2p在调控氟康唑疗效中的关键作用，其可作为抗真菌治疗的潜在药物靶点。