USE OF DISTINCT IRON UPTAKE SYSTEMS BY CANDIDA ALBICANS

白色念珠菌使用独特的铁吸收系统

• 批准号: 6723856
• 负责人: ANDREW B. DANCIS
• 金额: $ 35.66万
• 依托单位: UNIVERSITY OF PENNSYLVANIA
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-03-01 至 2009-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6723856
• 关键词: Candida albicans; biological transport; clinical research; gene deletion mutation; genetically modified animals; green fluorescent proteins; human tissue; iron metabolism; laboratory mouse; microarray technology; microorganism metabolism; neutrophil; oxidative stress; phenotype; siderophores; vascular endothelium; virulence

DESCRIPTION (provided by applicant): Candida albicans (Ca) is a common opportunistic fungal pathogen that causes serious infections in immunocompromised patients. Drug resistance is increasing, and there is a need to identify new drug targets. Iron acquisition has been shown to be an important factor for virulence of bacteria, as well as for Ca. Knockout mutants lacking the CaFTR1 iron permease are avirulent in mouse models. We have found that Ca, in fact, uses three genetically and biochemically distinct iron uptake systems. A reductive system, requiring CaFTR1, is able to reduce and release ferric iron chelates, including transferrin chelates. A siderophore system mediates uptake of ferrisiderophore chelates of the ferrichrome type and requires the siderophore transporter CaSIT1. Finally, a heme iron utilization system requires heme oxygenase encoded by CaHMXl. In Aim1 usage of the different systems will be tested under varied types of stress by measuring iron uptake from different substrates and by measuring expression of CaSIT1, CaFTR1 and CaHMX1. Deletion strains lacking in one of the iron uptake systems will be tested for growth properties, phenotypes and sensitivities. In Aim 2, usage of the different uptake systems will be evaluated in model systems that include a model of oropharyngeal (epithelial) candidiasis, endothelial cell invasion, neutrophil interaction and intravenous infection of mice. Knockouts lacking individual uptake systems will be evaluated for their behavior in these model systems, with attention to deficits that may alter virulence. Finally in Aim 3, microarrays will be used to examine the effects of iron uptake from different iron sources (via different uptake systems) on expression of virulence genes. The hypothesis of this work is that different iron acquisition pathways are active in different host environments and may mediate virulent infections in those settings.

描述（由申请人提供）：白色念珠菌（Ca）是一种常见的机会性真菌病原体，可导致免疫功能低下患者严重感染。耐药性不断增加，需要确定新的药物靶点。铁的获取已被证明是细菌毒力以及钙的重要因素。缺乏 CaFTR1 铁通透酶的敲除突变体在小鼠模型中是无毒的。我们发现，事实上，Ca 使用三种遗传和生化上不同的铁吸收系统。需要 CaFTR1 的还原系统能够还原并释放三价铁螯合物，包括转铁蛋白螯合物。铁载体系统介导铁色素型铁铁载体螯合物的摄取，并且需要铁载体转运蛋白 CaSIT1。最后，血红素铁利用系统需要由CaHMX1编码的血红素加氧酶。 在 Aim1 中，将通过测量不同底物的铁吸收以及测量 CaSIT1、CaFTR1 和 CaHMX1 的表达，在不同类型的应激下测试不同系统的使用情况。将测试缺乏铁吸收系统之一的缺失菌株的生长特性、表型和敏感性。在目标 2 中，将在模型系统中评估不同摄取系统的使用，包括口咽（上皮）念珠菌病、内皮细胞侵袭、中性粒细胞相互作用和小鼠静脉感染模型。将评估缺乏个体摄取系统的敲除小鼠在这些模型系统中的行为，并注意可能改变毒力的缺陷。最后，在目标 3 中，微阵列将用于检查不同铁源（通过不同的摄取系统）摄取铁对毒力基因表达的影响。 这项工作的假设是，不同的铁获取途径在不同的宿主环境中活跃，并可能介导这些环境中的有毒感染。