The Mechanism Of RTA2Involved In The Reduced Sensitivity To Fluconazole In Candida Albicans

Due to the emergence of drug-resistance, first-line therapy with fluconazole (FLC)increasingly resulted in clinical failure for the treatment of candidemia. Our previousstudies found that in vitro RTA2was involved in the calcineurin-mediated resistance toFLC in C. albicans. In this study, we found that calcium-activated-calcineurin significantlyreduced the in vitro sensitivity of C. albicans to FLC by blocking the impairment of FLCto the plasma membrane via Rta2p. Furthermore, we found that RTA2itself was notinvolved in C. albicans virulence, but the disruption of RTA2dramatically increased thetherapeutic efficacy of FLC in a murine model of systemic candidiasis. Conversely, ectopicexpression of RTA2significantly reduced FLC efficacy in a mammalian host. Finally, wefound that calcium-activated-calcineurin, through its target Rta2p, dramatically reduced theefficacy of FLC against candidemia. Given the critical roles of Rta2p in controlling theefficacy of FLC, Rta2p can be a potential drug target for antifungal therapies.RTA2was a target of the calcineurin signaling pathway, but its regulatory mechanismwas not clear. We used the Renilla Luciferase reporter system to study this subject:We gotfurther evidence of RTA2was a target gene of CaN signaling pathway and whoseexpression levels was regulated by the transcription factor Crzlp;the CDRE(calcineruin-dependent response element)components of RTA2mainly located in-973bp~-920bp upstream of the promoter of RTA2gene,the sequences might be GATGT.The previous study found that1mMCaCl2can activate CaN signaling pathway andincreased the expression level of RTA2to different degrees in clinical Candida albicans.Ca2+-induced-upregulation of RTA2dramatically decreased the therapeutic efficacy ofFLC in a murine model of systemic candidiasis compared with Ca2+-induced-nonupregulation of RTA2. In this study, through the in vitro susceptibility testing andReal-Time PCR experiments: we demonstrate that Ca2+-induced-upregulation of RTA2wascorrelated with the in vitro Ca2+-reduced-sensitivity to fluconazole. The expression level ofRTA2was increased by Ca2+in clinical isolate of0511522.The disruption of RTA2in thisisolate block the in vitro Ca2+-reduced-sensitivity to fluconazole; The relationship betweenCa2+-induced-upregulation of RTA2and in vitro Ca2+-reduced-sensitivity to fluconazolewas also verified in vivo. The disruption of RTA2in0511522can significantly increasedthe therapeutic efficacy of FLC in a murine model of systemic candidiasis. To conclude, invitro and in vivo calcium induced the up-regulation of RTA2gene to makes the clinical isolates reduce its sensitivity to fluconazole.