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，估计在美国每年发生63,000次入侵性念珠菌病，估计成本为2-4亿美元。尽管已经从临床样本中分离出多种致病真菌选择，但念珠菌属的酵母菌种类是机会真菌感染的主要原因，白色念珠菌是普遍的病原体，估计导致40％的真菌病例。在过去的十年中，念珠菌感染已通过Caspofungin有效治疗，Caspofungin是一种棘手类别的主要抗真菌，会干扰细胞壁合成。随着基于这种药物使用的增加，对抗Caspofungin菌株感染的报告数量的数量已增加，从2001年的0.5％增加到2009年的3.1％，因此预计Caspofungin耐药性将在不久的将来引起主要问题。然而，与白色念珠菌对氟康唑的抗性的众多且众多的机械性相反，关于对cas-pofungin的耐药性的机制知之甚少。 Caspofungin临床耐药性具有一种公认的机制，涉及FKS1（ORF19.2929）基因中的点突变，该基因编码了1,3 - ？ - D-d-Glucan合酶的亚基，需要正常的葡聚糖合成，即细胞壁的主要成分。 FKS1突变的形成始终与治疗衰竭有关。来自患者的许多其他分离株含有重塑的细胞壁，并显示实验室实验中对cas-pofungin的耐药性增加。这种共同称为的细胞壁挽救机制与可逆的变化有关，可增强细胞壁，尤其是几丁质的增加。我们自己的数据表明，可以通过多种分子机械主义实现对Caspofungin的抗性。当在Caspofungin存在的情况下培养白色念珠菌时，我们观察到CH5单体菌株的出现，这表明耐药性负调节剂居住在该杂种中。单子CH5导致细胞壁中葡萄糖的减少和几丁质增加。该调节器机制涉及的CH5连接基因的克隆和特性将有助于阐明Caspofungin抗性的关键分子途径。此外，在初步研究中，我们获得了证据表明，CH5单切开术涉及FKS1（见上文）或GSL2基因的两倍下调，分别属于CH1和CHR，并且需要正常合成细胞壁葡聚糖。根据我们的发现，我们假设CH5带有正常合成细胞壁成分所需的多个基因。损失一个CH5会导致实验室对echinocandin类药物的抵抗力增加。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，它们可能参与了单子体菌株中caspofungin抗性的机理。在这里，我们建议启动编码Caspofungin耐药性负调控因子的基因的研究。我们的发现对于研究白色念珠菌中耐药性现象的临床医生和研究人员将具有很高的意义。