Novel Azole Resistance Mechanisms in Candida albicans

C.白色念珠菌是一种机会性人类真菌病原体，其引起粘膜、皮肤和全身感染，包括口咽念珠菌病（OPC），这是AIDS患者中最常见的机会性感染。氟康唑和其他唑类抗真菌药物已被证明在OPC的管理有效;然而，随着这些药物的使用增加，治疗失败的发生与唑类耐药菌株的出现有关。白色念珠菌虽然使用高效抗逆转录病毒疗法（HAART）已经降低了美国艾滋病患者的OPC频率，但在不发达国家，这种疗法的有限使用，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。虽然已经描述了唑类耐药的几种机制，但这些机制不足以解释许多临床分离株的这种特性。我们发现了编码MDR 1外排泵基因转录调控因子的MRR 1，它是念珠菌唑类抗真菌药耐药的中心调控因子。白色念珠菌MRR 1基因的功能获得性突变导致该转录因子的组成性激活、MDR 1的上调和氟康唑耐药性的增加。在目前的提案中概述的具体目标代表了实现我们的总体目标的下一步，即了解Mrr 1 p如何影响C的唑类耐药性。白色念珠菌我们将确定Mrr 1 p的直接和间接靶基因，阐明其顺式作用元件，并确定这些基因影响Mrr 1 p介导的唑类耐药。我们还将鉴定与Mrr 1 p相关的辅助蛋白，并确定这些辅助蛋白是否影响Mrr 1 p介导的唑类耐药性。这些研究将进一步阐明唑类抗真菌药物耐药的分子基础，并最终指出预测治疗失败，克服唑类耐药，并改善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.