USE OF DISTINCT IRON UPTAKE SYSTEMS BY CANDIDA ALBICANS

描述（由申请方提供）：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发生严重感染。耐药性正在增加，需要确定新的药物靶点。铁的获得已被证明是细菌毒力的重要因素，以及Ca。缺乏CaFTR 1铁通透酶的敲除突变体在小鼠模型中是无毒的。我们已经发现，钙，事实上，使用三个遗传和生化不同的铁吸收系统。需要CaFTR 1的还原系统能够还原和释放三价铁螯合物，包括转铁蛋白螯合物。铁载体系统介导铁色素型铁载体螯合物的摄取，并需要铁载体转运蛋白CaSIT1。最后，血红素铁利用系统需要由CaHMXl编码的血红素加氧酶。 在Aim 1中，将通过测量来自不同底物的铁摄取以及通过测量CaSIT 1、CaFTR 1和CaHMX 1的表达，在不同类型的胁迫下测试不同系统的使用。缺失菌株缺乏铁吸收系统之一，将测试生长特性，表型和敏感性。在目标2中，将在模型系统中评价不同摄取系统的使用，所述模型系统包括口咽（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内感染的模型。将评估缺乏单个摄取系统的敲除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，微阵列将用于检查从不同铁源（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是活跃的，并可能介导这些环境中的毒力感染。

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.