Molecular mechanisms of caspofungin resistance in the pathogen Candida albicans

白色念珠菌病原体卡泊芬净耐药的分子机制

基本信息

批准号：
8903703
负责人：
ELENA RUSTCHENKO
金额：
$ 34.54万
依托单位：
UNIVERSITY OF ROCHESTER
依托单位国家：
美国
项目类别：
财政年份：
2014
资助国家：
美国
起止时间：
2014-08-15 至 2017-07-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8903703
关键词：
Anabolism Antifungal Agents Biogenesis Biological Candida Candida albicans Candida albicans resistance Candidate Disease Gene Candidiasis Carbon Caspofungin Catalytic Domain Cell Wall Chitin Chitin Synthase Chitinase Chromosomes Chromosomes, Human, Pair 5 Clinic Clinical Cloning Complement DNA DNA Library Data Diploidy Down-Regulation Drug resistance Drug usage Environment Failure Fluconazole resistance Fungemia Future Gene Dosage Gene Expression Genes Genetic Genome Glucans Goals Growth Health Human Industrial fungicide Infection Laboratories Lead Libraries Link Molecular Monosomy Mutation Mycoses Pathway interactions Patients Pharmaceutical Preparations Point Mutation Predisposition Proteins Regulation Reporting Research Research Personnel Resistance Role Sampling Series Source Testing Therapeutic Trisomy United States Yeasts base cell killing clinically relevant cost dosage experience fungus glucan synthase mutant overexpression pathogen polyglucosan research study resistance mechanism resistant strain

项目摘要

DESCRIPTION (provided by applicant): Candidiasis is the most common fungal infection, with an estimated 63,000 episodes of invasive candidiasis per year occurring in the United States, with a cost estimated at $2-4 billion. Although a diverse selection of pathogenic fungi have been isolated from clinical samples, the yeast species of the genus Candida are the predominant cause of opportunistic fungal infections, with Candida albicans the prevalent pathogen, causing an estimated 40% of cases of fungemia. For the last decade, Candida infections have been effectively treated with caspofungin, a major antifungal of the echinocandin class that interferes with cell wall synthesis. As antici- pated based on increased use of this drug, the number of reports of infections with caspofungin-resistant strains has increased, from 0.5% in 2001 to 3.1% in 2009, and so caspofungin resistance is expected to be- come a major concern in the near future. However, in contrast to the numerous and well-understood mecha- nisms of C. albicans resistance to fluconazole, little is known regarding the mechanism(s) of resistance to cas- pofungin. There is one recognized mechanism of caspofungin clinical resistance that involves point mutations in the FKS1 (orf19.2929) gene encoding a subunit of 1,3-?-D-glucan synthase required for normal synthesis of glucan, a major component of the cell wall. Formation of FKS1 mutations is always associated with therapeutic failure. Many other isolates from patients contain remodeled cell wall and show increase of resistance to cas- pofungin in laboratory experiments. This co-called cell wall salvage mechanism is associated with reversible alterations that strengthen the cell wall, particularly increased chitin. Our own data show that laboratory resistance to caspofungin can be attained via multiple molecular mech- anisms. When culturing C. albicans in the presence of caspofungin, we have observed the emergence of re- sistant strains monosomic for Ch5, indicating that negative regulators of resistance are resident on this chro- mosome. Monosomic Ch5 leads to decreased glucan and increased chitin in the cell wall. Cloning and charac- terization of the Ch5-linked genes involved in this regulator mechanism will help elucidate key molecular pathways of caspofungin resistance. Moreover, in preliminary studies, we have obtained evidence that Ch5 monosomy involves two-fold downregulation of the FKS1 (see above) or GSL2 genes, residing on Ch1 and ChR, respectively, and required for normal synthesis of cell wall glucan. Based on our findings, we hypothesize that Ch5 carries multiple genes required for normal synthesis of cell wall components. Loss of one Ch5 leads to increased laboratory resistance to drugs of the echinocandin class. In support of this hypothesis, our initial analyses have revealed two candidate genes on Ch5 that are likely to be involved in the mechanism of caspofungin resistance in monosomic strains. Here, we propose to initiate the study of the genes that encode negative regulators of caspofungin resistance. Our findings will be of high significance to clinicians and researchers investigating the phenomenon of drug resistance in C. albicans.

描述（由申请人提供）：念珠菌病是最常见的真菌感染，估计美国每年发生 63,000 起侵袭性念珠菌病，造成的损失估计为 2-40 亿美元。尽管从临床样本中分离出多种病原真菌，但念珠菌属酵母菌是机会性真菌感染的主要原因，其中白色念珠菌是常见病原体，估计导致 40% 的真菌血症病例。在过去的十年中，卡泊芬净可以有效治疗念珠菌感染，卡泊芬净是棘白菌素类的主要抗真菌药物，可干扰细胞壁的合成。正如预期的那样，随着该药物使用的增加，卡泊芬净耐药菌株感染的报告数量有所增加，从 2001 年的 0.5% 增加到 2009 年的 3.1%，因此卡泊芬净耐药性预计将成为一个主要问题在不久的将来。然而，与白色念珠菌对氟康唑耐药的众多且众所周知的机制相比，人们对卡泊芬净的耐药机制知之甚少。卡泊芬净临床耐药性有一种公认的机制，涉及 FKS1 (orf19.2929) 基因的点突变，该基因编码正常合成葡聚糖（细胞壁的主要成分）所需的 1,3-β-D-葡聚糖合酶亚基。。 FKS1 突变的形成总是与治疗失败相关。许多其他来自患者的分离物含有重塑的细胞壁，并且在实验室实验中显示出对卡泊芬净的耐药性增加。这种所谓的细胞壁挽救机制与强化细胞壁的可逆改变有关，特别是增加几丁质。我们自己的数据表明，实验室对卡泊芬净的耐药性可以通过多种分子机制实现。当在卡泊芬净存在下培养白色念珠菌时，我们观察到 Ch5 单体抗性菌株的出现，表明抗性负调节因子驻留在该染色体上。单体 Ch5 导致细胞壁中葡聚糖减少和几丁质增加。克隆和表征参与该调节机制的 Ch5 相关基因将有助于阐明卡泊芬净耐药性的关键分子途径。此外，在初步研究中，我们已经获得证据表明 Ch5 单体涉及 FKS1（见上文）或 GSL2 基因的两倍下调，这些基因分别位于 Ch1 和 ChR 上，是细胞壁葡聚糖正常合成所必需的。根据我们的发现，我们假设 Ch5 携带细胞壁成分正常合成所需的多个基因。丢失一个 Ch5 会导致实验室对棘白菌素类药物的耐药性增加。为了支持这一假设，我们的初步分析揭示了 Ch5 上的两个候选基因，它们可能参与单体菌株的卡泊芬净耐药机制。在这里，我们建议开始研究编码卡泊芬净耐药性负调节因子的基因。我们的研究结果对于临床医生和研究白色念珠菌耐药现象的研究人员具有重要意义。