Superoxide dismutases and mitochondrial oxidative stress in Candida albicans.

 描述（由申请人提供）：从细菌到人类，超氧化物歧化酶（SOD）通过催化超氧化物分解为氧气和过氧化氢，在抗氧化应激中发挥重要作用。典型的真核细胞含有Cu/Zn SOD 1，其主要存在于细胞质中，小部分定位于线粒体的膜间隙（IMS），而线粒体基质含有独特的锰SOD 2。铜和锰SOD的这种分配在整个进化过程中一直很保守，但在人类真菌病原体白色念珠菌中可以看到一个惊人的偏差。C.白色念珠菌在相同的胞质区室中独特地表达含锰和铜的SOD。Culotta实验室最近表明，这两种SOD根据生长状态和铜的差异表达。随着快速分裂的细胞和丰富的铜，Cu/Zn SOD 1占主导地位，而在长期稳定期，当铜变得有限，细胞从Cu/Zn SOD 1切换到Mn SOD 3。这种转变在实验室培养的C.白色念珠菌以及播散性念珠菌病的感染模型。然而，这种SOD酶转换的生物学原理是完全未知的。如果病原体对铜的降解敏感，为什么它保留了Cu/Zn SOD 1？我的假设是Cu/ZnSOD 1而不是MnSOD 3保护C。白色念珠菌线粒体氧化应激时，细胞迅速分裂。有趣的是，C。白色念珠菌经历线粒体呼吸的转换，似乎伴随着SOD酶的转换。快速分裂的细胞利用传统的铜依赖性细胞色素C氧化酶（考克斯）驱动的呼吸，预计会产生ROS;稳定期细胞使用替代氧化酶（AOX），不需要铜，预计会产生低ROS。我预测，在考克斯呼吸，铜/锌SOD 1进入线粒体，以防止线粒体ROS，而在AOX呼吸，有较少的需要，为IMS SOD和锰SOD 3保持胞质。SOD 1、SOD 3与线粒体呼吸和氧化应激之间可能存在的联系将被解决如下：目的1：了解C. SOD 1和SOD 3与线粒体呼吸的关系。将优化考克斯和AOX呼吸的条件，并将在这些条件下分离线粒体用于探测线粒体IMS中的SOD 1和SOD 3。我们还将测试高和低细胞内铜对线粒体呼吸和线粒体摄取SOD 1和SOD 3的影响。目的2：探讨SOD 1和SOD 3在线粒体氧化应激保护中的作用。我们将比较考克斯与AOX呼吸中产生的全细胞和线粒体ROS。我们将通过监测蛋白质氧化和线粒体功能来研究SOD 1和SOD 3在线粒体氧化应激保护中的作用。结合这些关于SOD酶和线粒体生物学的基础科学研究，白色念珠菌可以提供重要的见解，这种致病酵母如何适应和生存在人类宿主长期。

 DESCRIPTION (provided by applicant): From bacteria to humans, the superoxide dismutases (SODs) enzymes play important roles in oxidative stress resistance by catalyzing the disproportionation of superoxide to oxygen and hydrogen peroxide. A typical eukaryotic cell contains a Cu/Zn SOD1 that resides largely in the cytosol with a small fraction localized to the intermembrane space (IMS) of the mitochondria, while the mitochondrial matrix contains a distinct manganese SOD2. Such partitioning of copper and manganese SODs has been well conserved throughout evolution but a striking deviation can be seen with the human fungal pathogen, Candida albicans. C. albicans uniquely expresses both a manganese and copper containing SOD in the same cytosolic compartment. The Culotta lab has recently shown that these two SODs are differentially expressed according to growth state and copper. With rapidly dividing cells and abundant copper, Cu/Zn SOD1 predominates, while in long-term stationary phase when copper becomes limiting, cells switch from Cu/Zn SOD1 to Mn SOD3. This switch is evident in laboratory cultures of C. albicans as well as in infection models for disseminated candidiasis. However, the biological rationale for this switch in SOD enzymes is completely unknown. If the pathogen is susceptible to copper depravation, why has it retained Cu/Zn SOD1? My hypothesis is that Cu/Zn SOD1 but not Mn SOD3, protects C. albicans from mitochondrial oxidative stress when cells are rapidly dividing. Interestingly, C. albicans undergoes a switch in mitochondrial respiration that appears to accompany the switch in SOD enzymes. Rapidly dividing cells utilize the conventional copper dependent cytochrome C oxidase (COX) driven respiration that is predicted to generate ROS; stationary phase cells use an alternative oxidase (AOX) that does not require copper and is predicted to generate low ROS. I predict that during COX respiration, Cu/Zn SOD1 enters the mitochondria to guard against mitochondrial ROS, while during AOX respiration, there is less need for an IMS SOD and Mn SOD3 remains cytosolic. This possible connection between SOD1, SOD3 and mitochondrial respiration and oxidative stress will be addressed as follows: Aim 1: To understand the connection between C. albicans SOD1 and SOD3 and mitochondrial respiration. Conditions for COX and AOX respiration will be optimized and isolation of mitochondria during these conditions will be used to probe for SOD1 and SOD3 in the IMS of the mitochondria. We will also test the effects of high and low intracellular copper on mitochondrial respiration and mitochondrial uptake of SOD1 and SOD3. Aim 2: To determine the role of SOD1 and SOD3 in mitochondrial oxidative stress protection. We will compare whole cell and mitochondrial ROS produced in COX versus AOX respiration. We will investigate a role for SOD1 and SOD3 in mitochondrial oxidative stress protection by monitoring protein oxidation and mitochondrial function. Together these basic science studies on SOD enzymes and mitochondrial biology in C. albicans can provide important insight as to how this pathogenic yeast can adapt and survive long term in a human host.