The novel family of superoxide dismutase enzymes in Candida albicans

描述（由申请人提供）：传染性酵母菌白色念珠菌仍然是公共卫生的一个重要问题，特别是对免疫功能低下的个体。一组C.白色念珠菌包括一个含铜的超氧化物歧化酶（SOD）家族，其抑制有毒的超氧化物自由基。尽管它们在毒力方面的重要性已被证实，但实际上对C.白色念珠菌SOD或这些酶如何通过插入铜辅因子在细胞中被激活。在本研究应用中，我们计划开发新的系统来监测宿主对胞内铜和含铜SOD的影响。白色念珠菌C.将检查白色念珠菌：胞质溶胶中的Cu/Zn SOD（SOD 1），以及通过GPI锚附着于细胞壁的Cu/Zn SOD家族的细胞外成员（SOD 5）。两者都是重要的毒力，在我们的初步分析，都表现出一些独特的功能，没有看到其他铜/锌SOD。例如，在正常（非感染性）的实验室生长条件下，细胞内的SOD 1蛋白是无活性的，而酵母则使用一种不寻常的胞质锰SOD 3来去除超氧化物。细胞外SOD 5也是独特的，因为它似乎只结合铜，并且缺乏锌位点，而锌位点在细胞外SOD 5中是不变的。 其他真核Cu/Zn SOD。我们建议，这些不寻常的Cu-SOD已经发展到利用主机对金属的影响。在感染过程中，巨噬细胞吞噬溶酶体使病原体缺乏锰、锌和铁，同时试图用高水平的铜和活性氧杀死病原体。宿主的这种特定环境似乎是激活铜需要SOD的理想环境。我们假设，在感染过程中，细胞内的SOD 1和细胞外的SOD 5立即与铜，代表了第一道防线，对氧化爆发的主机。我们将开始通过开发系统来测试这一假设，在该系统中，我们可以监测发生在C.白色念珠菌感染期间的巨噬细胞。我们还将开发一种系统，用于从细胞壁或酵母分泌的酶活性SOD 5，这是一种在巨噬细胞感染期间监测细胞外SOD激活的宝贵工具。通过对重组SOD 5的金属分析，我们将讨论这种酶是否真的是一种仅含铜的SOD。这些研究处于探索性、试验开发阶段。这项为期2年的计划的发现和新系统将促进我们更长期的机制研究，旨在了解宿主对病原体金属和SOD酶的影响。这些基础研究有可能为开发针对铜和防止C激活的新疗法奠定基础。白念珠菌SOD对毒力至关重要。

DESCRIPTION (provided by applicant): The infectious yeast Candida albicans remains an important concern in public health, particularly with immune-compromised individuals. One set of virulence factors for C. albicans includes a family of copper containing superoxide dismutase (SOD) enzymes that scavenge toxic superoxide free radicals. In spite of their established importance in virulence, virtually nothing is known about the biochemistry of C. albicans SODs or how these enzymes are activated in cells through insertion of the copper co-factor. In this research application, we plan to develop new systems for monitoring the effects of the host on intracellular copper and copper containing SODs of C. albicans . Two types of Cu-containing SODs in C. albicans will be examined: a Cu/Zn SOD in the cytosol (SOD1), and an extracellular member of the Cu/Zn SOD family attached to the cell wall through GPI anchors (SOD5). Both are important for virulence and in our preliminary analyses, both exhibit some distinctive features not seen in other Cu/Zn SODs. For example, under normal (non-infectious) laboratory growth conditions, the intracellular SOD1 protein is inactive and the yeast instead uses an unusual cytosolic manganese-SOD3 to remove superoxide. The extracellular SOD5 is also unique in that it appears to bind only copper, and is lacking the zinc site that is invariant among other eukaryotic Cu/Zn SODs. We propose that these unusual Cu-SODs have evolved to exploit the host effects on metals. During infection, the macrophage phagolysosome starves pathogens of manganese, zinc and iron, while attempting to kill pathogens with high levels of copper and reactive oxygen. This particular environment of the host seems ideal for activating copper requiring SODs. We hypothesize that during infection, both the intracellular SOD1 and extracellular SOD5 are immediately charged with copper, representing the first line of defense against the oxidative burst of the host. We will begin to test this hypothesis by developing systems in which we can monitor changes in intracellular copper and Cu/Zn SOD activity that occur in C. albicans during infection of macrophages. We will also develop a system for recovering enzymatically active SOD5 from the cell wall or secreted from yeast, a tool that will prove invaluable for monitoring extracellular SOD activation during macrophage infection. Through metal analysis of recombinant SOD5, we will address whether this enzyme is truly a copper-only SOD. These studies are in the exploratory, assay-development phase. The findings and new systems that stem from this 2 year program will foster our more long-term mechanistic studies geared towards understanding host effects on pathogen metals and SOD enzymes. These basic research studies have the potential to seed development of new therapies that target copper and prevent activation of the C. albicans SODs essential for virulence.