Novel Azole Resistance Mechanisms in Candida albicans

白念珠菌是一种机会性的人类真菌病原体，可引起黏膜、皮肤和全身感染，包括口咽部念珠菌病(OPC)，这是艾滋病患者中最常见的机会性感染。氟康唑和其他唑类抗真菌药已被证明在治疗OPC方面有效；然而，随着这些药物的使用增加，出现了与耐药白念珠菌株相关的治疗失败。虽然高效抗逆转录病毒疗法(HAART)的使用减少了美国艾滋病患者的OPC频率，但不发达国家获得此类治疗的机会有限、依从性差以及与HAART相关的毒性可能会导致全球艾滋病患者中这一问题的增加。虽然已经描述了几种唑类耐药性的机制，但这些机制不足以解释许多临床分离株的这一特征。我们已经发现了编码mdr1外排泵基因转录调节因子的MRR1，它是白念珠菌对唑类真菌耐药的中心调节因子。MRR1基因的功能获得突变导致该转录因子的结构性激活，mdr1上调，并增加了对氟康唑的耐药性。当前提案中概述的具体目标代表着实现我们的总体目标的下一步，即了解mr1p如何影响白念珠菌的唑类耐药性。我们将鉴定mr1p的直接和间接靶基因，阐明它们的顺式作用元件，并确定这些基因中哪些影响mr1p介导的唑类耐药性。我们还将确定与mr1p相关的辅助蛋白，并确定这些辅助蛋白是否会影响mr1p介导的唑类耐药性。这些研究将进一步阐明唑类抗真菌耐药性的分子基础，并最终指向预测治疗失败、克服唑类耐药性和改进这类患者的抗真菌药物治疗的新策略。

C. albicans is an opportunistic human fungal pathogen that causes mucosal, cutaneous, and systemic infections including oropharyngeal candidiasis (OPC), the most frequent opportunistic infection among patients suffering from AIDS. Fluconazole and other azole antifungal agents have proven effective in the management of OPC; however, with increased use of these agents, treatment failures have occurred that have been associated with the emergence of azole-resistant strains of C. albicans. While the use of highly active antiretroviral therapy (HAART) has reduced the frequency of OPC among AIDS patients in the United States, limited access to such therapy in underdeveloped countries, poor compliance, and toxicity associated with HAART will likely contribute to an increase in this problem among AIDS patients world-wide. While several mechanisms of azole resistance have been described, these are not sufficient to explain this trait in many clinical isolates. We have discovered MRR1 which encodes the transcriptional regulator of the MDR1 efflux pump gene and is a central regulator or azole antifungal resistance in C. albicans. Gain-of-function mutations in the MRR1 gene result in the constitutive activation of this transcription factor, up-regulation of MDR1, and increased fluconazole resistance. The specific aims outlined in the current proposal represent the next steps towards achieving our overall goal of understanding how Mrr1p influences azole resistance in C. albicans. We will identify direct and indirect target genes of Mrr1p, elucidate their cis-acting elements, and determine which of these genes influence Mrr1p-mediated azole resistance. We will also identify accessory proteins that associate with Mrr1p and determine if these accessory proteins influence Mrr1p-mediated azole resistance. These studies will further elucidate the molecular basis for azole antifungal resistance and will ultimately point to novel strategies for predicting treatment failure, overcoming azole resistance, and improving antifungal pharmacotherapy in this patient population.