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

• 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
• 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

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，在美国每年估计发生63，000例侵袭性念珠菌病，费用估计为20 - 40亿美元。尽管从临床样本中分离出了多种致病真菌，但念珠菌属的酵母菌是机会性真菌感染的主要原因，白色念珠菌是流行的病原体，估计造成40%的真菌血症病例。在过去的十年中，念珠菌感染已被有效地治疗卡泊芬净，一种主要的抗真菌剂的棘白菌素类，干扰细胞壁的合成。由于这种药物使用的增加，卡泊芬净耐药菌株感染的报告数量增加，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在不久的将来成为主要问题。然而，与C.白念珠菌对氟康唑的耐药性，关于卡泊芬净耐药性的机制知之甚少。有一种公认的卡泊芬净临床耐药机制涉及编码1，3-β-内酰胺酶亚基的FKS 1（orf19.2929）基因的点突变。葡聚糖合成酶是葡聚糖正常合成所必需的，葡聚糖是细胞壁的主要成分。FKS 1突变的形成总是与治疗失败相关。许多来自患者的其他分离株含有重塑的细胞壁，并且在实验室实验中显示对卡泊芬净的耐药性增加。这种所谓的细胞壁挽救机制与加强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，通过多种分子机制可以获得对卡泊芬净的实验室耐药性。培养C.在卡泊芬净存在下，我们观察到Ch 5单体抗性菌株的出现，表明抗性的负调节因子存在于该染色体上。单体Ch 5导致细胞壁中葡聚糖减少和几丁质增加。克隆和鉴定参与该调节机制的Ch 5连锁基因将有助于阐明卡泊芬净耐药的关键分子途径。此外，在初步研究中，我们获得的证据表明，Ch 5单体性涉及FKS 1（见上文）或GSL 2基因的两倍下调，分别位于Ch 1和ChR上，并为细胞壁葡聚糖的正常合成所需。基于我们的研究结果，我们假设Ch 5携带细胞壁成分正常合成所需的多个基因。一个Ch 5的丢失导致对棘白菌素类药物的实验室耐药性增加。为了支持这一假设，我们的初步分析揭示了Ch 5上的两个候选基因，它们可能参与单体菌株中卡泊芬净耐药的机制。在这里，我们建议启动对编码卡泊芬净耐药性负调节因子的基因的研究。我们的研究结果将对临床医生和研究人员调查耐药现象的C。白色念珠菌。