Glucan Binding to Azole Drugs: A Novel Resistance Mechanism in Candida albicans

描述（由申请人提供）：白色念珠菌（Ca）是免疫功能低下人群口腔和全身真菌感染以及女性阴道感染的常见原因。念珠菌感染通常用唑类药物治疗，在这些患者群体中经常出现对唑的耐药性。抗唑的主要机制包括外排泵的表达增加和麦角甾醇生物合成酶的改变。然而，在许多耐药临床分离株中尚未发现这些耐药机制。最近，在念珠菌生物膜中发现了第三种抗唑机制——在粘膜表面和植入医疗器械上形成的细胞和细胞外物质基质。在这些生物膜中，高水平的抗唑性是由于细胞壁中（-1,3葡聚糖）的增加与唑类药物结合。我们的假设是(-1,3葡聚糖结合的唑不仅是生物膜耐药的一个组成部分，而且是浮游临床耐药菌株的一个组成部分。氮唑与细胞壁的葡聚糖结合会阻止药物到达细胞质，增加耐药性。总体目标是评估唑结合(-1,3葡聚糖作为念珠菌耐药成分的贡献。具体来说，本研究研究了(-1,3葡聚糖结合如何影响真菌细胞中的药物积累，并评估了临床分离株（-1,3葡聚糖结合）的情况，包括没有已知耐药机制的分离株。本应用程序的具体目的是：1。目的：探讨(-1,3葡聚糖结合对白色念珠菌氟康唑积累的影响。真菌细胞的唑积累可能是几个相互竞争的过程的结果，包括输入和输出（内部积累），也可能是-1,3葡聚糖结合（外部积累）。在改变细胞葡聚糖含量的条件下，将评估细胞中放射性标记的FLC积累。2. 评估临床分离株药物敏感性改变时的(1,3葡聚糖结合。唑结合(-1,3葡聚糖和细胞中的（-1,3葡聚糖）水平将在耐药的临床分离株中进行评估，其中尚未确定已知的耐药机制。在可预见的未来，唑类药物和真菌细胞之间的相互作用将继续成为临床重要问题。(1,3葡聚糖结合的唑类药物是这些相互作用的一个新的和重要的方面。对这一过程的全面描述，以及我们对药物/细胞相互作用的其他方面的理解，有可能有助于改善真菌感染和耐药性的诊断、治疗和预防。致病性白色念珠菌在口腔、阴道和血液中引起重大的人类疾病。本文拟分析抗真菌药物氟康唑与白色念珠菌的相互作用。特别是，它将验证真菌细胞壁像海绵一样吸收药物的假设，从而使细胞在药物存在的情况下持续存在。

DESCRIPTION (provided by applicant): The pathogenic yeast Candida albicans (Ca) is a frequent cause of oral and systemic fungal infections in immune-compromised people and of vaginal infections in women. Candida infections are usually treated with azole drugs, and azole resistance arises frequently in these patient populations. The major mechanisms of azole resistance include increased expression of efflux pumps and alterations in enzymes in ergosterol biosynthesis. However, these mechanisms of resistance have not been identified in many resistant clinical isolates. Recently, a third mechanism of azole resistance has been found in Candida biofilms - matrices of cells and extracellular material that forms on mucosal surfaces and implanted medical devices. The high levels of azole resistance in these biofilms is due to increased production of (-1,3 glucan in the cell wall that binds to azole drugs. Our Hypothesis is that (-1,3 glucan binding of azoles is a component of resistance not only in biofilms, but in planktonic clinically resistant isolates. Glucan binding of azoles to the cell wall would prevent the drug from reaching the cytoplasm, increasing resistance. The Overall Goal is to evaluate the contribution of azole binding to (-1,3 glucan as a component of drug resistance in Candida. Specifically, this proposal investigates how (-1,3 glucan binding affects drug accumulation in fungal cells, and it evaluates (-1,3 glucan binding in a collection of clinical isolates, including isolates with no known resistance mechanisms. The Specific Aims of this application are: 1. To determine the effect of (-1,3 glucan binding on fluconazole accumulation in Candida albicans. Azole accumulation by fungal cells is likely to be the result of several competing processes, including import and efflux (internal accumulation), and possibly (-1,3 glucan binding (external accumulation). Radiolabeled FLC accumulation in cells will be evaluated under conditions that alter the glucan content of the cells. 2. To assess (-1,3 glucan binding in clinical isolates with altered drug susceptibilities. Azole binding to (-1,3 glucans, and (-1,3 glucan levels in the cells will be assessed in resistant clinical isolates in which no known mechanism of resistance has been identified. The interactions between azoles and fungal cells will continue to be clinically significant issues for the foreseeable future. (-1,3 glucan binding of azole drugs is a new and important aspect of these interactions. A full characterization of this process, together with our understanding of the other facets of drug/cell interactions, has the potential to contribute to improvements in diagnosis, treatment and prevention of fungal infections and of resistance. PUBLIC HEALTH RELEVANCE The pathogenic yeast Candida albicans causes significant human disease in the mouth, vagina and blood stream. This proposal will analyze the interaction between the antifungal drug fluconazole and C. albicans. In particular, it will test the hypothesis that the fungal cell wall acts as a sponge, soaking up the drug, thus allowing the cells to persist in the presence of drug.