Novel Azole Resistance Mechanisms in Candida albicans

白色念珠菌是一种机会性人类真菌病原体，可引起粘膜、皮肤和全身感染，包括口咽念珠菌病（OPC），这是艾滋病患者中最常见的机会性感染。氟康唑和其他含唑类抗真菌药物已被证明对OPC的治疗有效；然而，随着这些药物使用的增加，出现了与耐唑白色念珠菌菌株出现相关的治疗失败。虽然高效抗逆转录病毒疗法（HAART）的使用降低了美国艾滋病患者OPC的频率，但在不发达国家，这种疗法的可及性有限，依从性差，以及与HAART相关的毒性可能会导致世界范围内艾滋病患者OPC问题的增加。虽然已经描述了几种抗唑机制，但这些不足以解释许多临床分离株的这种特征。我们发现了编码MDR1外排泵基因转录调控因子的MRR1，是白色念珠菌抗唑耐药的中心调控因子。MRR1基因的功能获得突变导致该转录因子的组成性激活，MDR1的上调，并增加氟康唑耐药性。当前提案中概述的具体目标代表了实现我们了解Mrr1p如何影响白色念珠菌中唑耐药性的总体目标的下一步。我们将鉴定Mrr1p的直接和间接靶基因，阐明它们的顺式作用元件，并确定哪些基因影响Mrr1p介导的唑类耐药。我们还将鉴定与Mrr1p相关的辅助蛋白，并确定这些辅助蛋白是否影响Mrr1p介导的唑耐药性。这些研究将进一步阐明唑类抗真菌药物耐药的分子基础，并最终为预测治疗失败、克服唑类耐药和改善该患者群体的抗真菌药物治疗提供新的策略。

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.