Comparative Transcriptome Analysis of the CO2 Sensing Pathway Via Differential Expression of Carbonic Anhydrase in Cryptococcus neoformans
Comparative Transcriptome Analysis of the CO2 Sensing Pathway Via Differential Expression of Carbonic Anhydrase in Cryptococcus neoformans
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DOI：
10.1534/genetics.110.118315
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发表时间：
2010-08-01
期刊：
影响因子：
3.3
通讯作者：
Bahn, Yong-Sun
中科院分区：
文献类型：
--
作者：
Kim, Min Su;Ko, Young-Joon;Bahn, Yong-Sun
由于自然环境中二氧化碳水平的巨大差异，二氧化碳(CO2)的感知和通过碳酸酐酶(CA)的代谢在感染人类宿主的病原真菌的生存和增殖中发挥着关键作用。在导致致死性真菌性脑膜脑炎的新生隐球菌中，CAN2CA在空气中的细胞生长和病原体的性别分化过程中都起着至关重要的作用。然而，Can2下游的信令网络在很大程度上是未知的。为了解决这个问题，本研究采用比较转录组DNA微阵列分析了一株新生隐孢子菌，在该菌株中，CAN2的表达受CTR4(铜转运蛋白)启动子的人为控制。当CAN2被抑制时，P-CTR4：：CAN2菌株表现出CO2依赖的生长缺陷，而当CAN2过表达时，P-CTR4：：CAN2菌株恢复正常生长。转录组分析确定的CaN2依赖基因包括FAS1(脂肪酸合成酶1)和GPB1(G蛋白β亚基)，支持Can2在脂肪酸生物合成和性别分化中的作用。囊膜结构设计蛋白Cas3也被发现依赖于CaN 2，但不参与CO2介导的囊膜诱导。最值得注意的是，大多数依赖于CAN2的基因是环境胁迫调节(ESR)基因。支持这一点的是，CAN2过表达菌株对氧化和遗传毒性压力以及抗真菌药物(如多烯和唑类药物)高度敏感，这可能是由于膜完整性缺陷造成的。最后，一个氧化应激反应的atf1转录因子也被发现依赖于CaN 2。ATF1不仅在包括耐热性和抗真菌耐药性在内的多种应激反应中发挥重要作用，而且还抑制新生葡萄球菌的黑色素和包膜的产生。综上所述，这项研究为病原真菌中CA/CO2敏感通路协调的全面信号网络提供了洞察力。
Carbon dioxide (CO2) sensing and metabolism via carbonic anhydrases (CAs) play pivotal roles in survival and proliferation of pathogenic fungi infecting human hosts from natural environments due to the drastic difference in CO2 levels. In Cryptococcus neoformans, which causes fatal fungal meningoencephalitis, the Can2 CA plays essential roles during both cellular growth in air and sexual differentiation of the pathogen. However the signaling networks downstream of Can2 are largely unknown. To address this question, the present study employed comparative transcriptome DNA microarray analysis of a C. neoformans strain in which CAN2 expression is artificially controlled by the CTR4 (copper transporter) promoter. The P-CTR4::CAN2 strain showed growth defects in a CO2-dependent manner when CAN2 was repressed but resumed normal growth when CAN2 was overexpressed. The Can2-dependent genes identified by the transcriptome analysis include FAS1 (fatty acid synthase 1) and GPB1 (G-protein beta subunit), supporting the roles of Can2 in fatty acid biosynthesis and sexual differentiation. Cas3, a capsular structure designer protein, was also discovered to be Can2-dependent and yet was not involved in CO2-mediated capsule induction. Most notably, a majority of Can2-dependent genes were environmental stress-regulated (ESR) genes. Supporting this, the CAN2 overexpression strain was hypersensitive to oxidative and genotoxic stress as well as antifungal drugs, such as polyene and azole drugs, potentially due to defective membrane integrity. Finally, an oxidative stress-responsive Atf1 transcription factor was also found to be Can2-dependent. Atf1 not only plays an important role in diverse stress responses, including thermotolerance and antifungal drug resistance, but also represses melanin and capsule production in C. neoformans. In conclusion, this study provides insights into the comprehensive signaling networks orchestrated by CA/CO2-sensing pathways in pathogenic fungi.