靶位是Upc2和Cph2信号通路的化合物的鉴定以及对白念珠菌维持麦角固醇平衡的作用研究

白念珠菌是人体主要的致病真菌，对免疫低下的患者会引起严重甚至威胁生命的侵袭性感染。氟康唑是临床使用最多的一种抗真菌药，由于临床广泛长期使用耐药菌株不断出现。其对氟康唑耐药机制有:1)靶酶Erg11基因突变或转录上调;2)多药物转运泵的上调;3)真菌对药物的应激机制。这些机制中任何机制丧失功能会使白念珠菌对药物敏感性增高。Upc2是麦角固醇合成途径中基因的转录调节器，是引起三唑类药物耐药的关键位置。我们初步数据显示Cph2也是麦角固醇合成的调节器。Upc2和Cph2调节异常会改变白念珠菌对药物的敏感性。虽然已经知道麦角固醇体内平衡的转录调节对耐药很重要，但白念珠菌如何调节Upc2 和Cph2 使麦角固醇维持平衡的机制还不清楚。我们假设针对Upc2 和Cph2 活性信号通路的小分子将会使白念珠菌对氟康唑敏感。鉴定这些小分子以及它们的靶位有助于发现调控麦角固醇稳态和氟康唑耐药的新的通路和机制。

Candida albicans is the leading fungal pathogen of humans, causing life-threatening infection in immunocompromised individuals. Fluconazole is the most common one of antifungal drugs in clinical use. They inhibit lanosterol 14-demethylase (Erg11). Its therapeutic efficacy is compromised by the emergence of drug resistant strains, and static rather than cidal activities that block fungal growth but do not eradicate the pathogen population. C. albicans can acquire fluconazole resistance by multiple distinct mechanisms: 1)alteration of the target enzyme Erg11 by mutation or transcriptional up regulation; 2)up-regulation of multidrug transporters; 3) mechanisms to cope with drug-induced cellular stresses. Loss of function in any of the mechanisms leads to elevated drug sensitivity. In particular, Upc2, a transcriptional regulator of ergosterol biosynthesis pathway genes, is critical for resistance to triazoles. Our preliminary data show that Cph2 is also a regulator of ergosterol biosynthesis. The misregulation of Upc2 and Cph2 leads to altered drug sensitivity. Despite the importance of the transcriptional regulation of ergosterol homeostasis in drug resistance, how Upc2 and Cph2 are regulated in C. albicans is unclear. We hypothesize that small molecules targeting the signaling pathways for Upc2 and Cph2 activation will render C. albicans cells sensitive to fluconazole. Identification of small molecules and their targets will lead to the discovery of novel pathways and mechanisms that control ergosterol homeostasis and fluconazole resistance.