PP2C磷酸酶Ptc2在真菌应答二氧化碳信号中的功能和作用机制研究

条件致病性真菌白念珠菌可以在人体不同部位定殖，致病过程中能够侵染皮肤和深层组织。在整个生命周期里，其生境中的CO2水平是不断变化的，因此感受CO2并作出恰当的应答对白念珠菌至关重要。尽管腺苷酸环化酶在真菌中具有传递CO2信号的功能，但很多对CO2的应答并不受其调控，暗示存在CO2感受新途径。我们在前期研究中发现白念珠菌PP2C磷酸酶Ptc2的活性直接被CO2激活，并调控菌丝延长、白灰转换和碳酸酐酶表达。而且Ptc2在酿酒酵母和新生隐球菌中同样作为CO2感受器起调控作用。本项目将揭示Ptc2调控白灰转换的分子机制；通过定量磷酸化蛋白质组和功能基因组学等研究绘制出Ptc2通过下游底物应答CO2信号的调控网络，并明确Ptc2对致病性的影响；然后对Ptc2的结构和功能在真菌中的保守性进行分析。本项目在真菌中鉴定出由Ptc2掌控的CO2感受新机制，为真菌如何感受气体微环境提供新见解。

The opportunistic pathogenic fungus Candida albicans colonizes multiple sites of humans, it can also infect sites ranging from skin to deep tissues during pathogenesis. During the whole life cycle, it encounters fluctuating carbon dioxide levels, so the capacity to sense and response to changing carbon dioxide levels is crucial for C. albicans. Although adenylyl cyclase has been shown to transmit CO2 signal in fungi, it is not required for many CO2-responses, implying that a novel CO2 sensing mechanism may exist in fungi. Our previous work found that the activity of Ptc2, a type 2C protein phosphatase, was stimulated directly by CO2 in C. albicans to regulate CO2-responsive expression of carbonic anhydrase, hyphal elongation and white-opaque switch. Ptc2 also acts as a CO2 sensor in Saccharomyces cerevisiae and Cryptococcus neoformans to regulate CO2 responses. In this project, we will elucidate the mechanism by which Ptc2 regulates white-opaque switch. We will then map out the network in which Ptc2 regulates diverse CO2-responses through different downstream substrates using quantitative phosphorylation proteomics and functional genomics, as well as clarify its impact on pathogenicity. Next, we will analyze the conservation of structure and function of Ptc2 in fungi. In this project, we identify a new CO2 sensing mechanism governed by Ptc2 in fungi, which provides new insights on how fungi sense gas microenvironment.