Mitochondrial Activity and Cyr1 Are Key Regulators of Ras1 Activation of C. albicans Virulence Pathways.
Mitochondrial Activity and Cyr1 Are Key Regulators of Ras1 Activation of C. albicans Virulence Pathways.
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DOI：
10.1371/journal.ppat.1005133
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发表时间：
2015-08
期刊：
影响因子：
6.7
通讯作者：
Hogan DA
中科院分区：
文献类型：
--
作者：
Grahl N;Demers EG;Lindsay AK;Harty CE;Willger SD;Piispanen AE;Hogan DA
白色念珠菌既是一种主要的真菌病原体，也是人体微生物群落的一员。从酵母到菌丝生长的形态转换与疾病相关，并且已知许多环境因素影响酵母到菌丝的转换。Ras1-Cyr1-PKA通路是C.白色念珠菌形态发生以及生物膜形成和白色-不透明转换。以前的研究表明，菌丝生长强烈抑制线粒体抑制剂。在这里，我们发现线粒体抑制剂强烈降低Ras 1 GTP结合和活性在C。在其他念珠菌中观察到类似的效果。与呼吸活性和GTP-Ras1结合之间存在联系一致，缺乏复合物I或复合物IV的突变体在菌丝诱导条件下作为酵母生长，具有较低水平的GTP-Ras1，并且Ras1 GTP结合不受呼吸抑制剂的影响。线粒体干扰剂降低细胞内ATP浓度和不同的呼吸抑制剂生长的细胞的代谢组学分析发现一致的扰动丙酮酸代谢和TCA循环，氧化还原状态的变化，增加脂质的catalysts，并降低甾醇含量，这表明增加AMP激酶活性。生化和遗传实验提供了强有力的证据，在该模型中，Ras1的激活是由ATP水平控制的AMP激酶独立的方式。Ras 1-GTP的减少需要Ras 1 GTPase激活蛋白Ira 2，而不是Ras 1鸟苷酸交换因子Cdc 25，以响应抑制剂介导的ATP水平降低。此外，Cyr 1，一种充分表征的Ras1效应物，参与控制Ras1-GTP结合以响应线粒体活性降低，这表明Ras1和Cyr 1信号传导的修正模型，其中Cyr 1和Ras1相互影响，并且与Ras2一起似乎形成整合不同环境和细胞内信号（包括代谢状态）所必需的主调节复合物，来决定细胞形态的命运 白色念珠菌是一种成功的人类致病真菌。它是一种多态性生物体，从酵母菌转变为菌丝生长的能力与真菌到病原体的转变有关。先前的研究确定Ras 1-cAMP-蛋白激酶A途径是菌丝生长的关键调节因子。在这里，我们报告说，线粒体活性在Ras1激活中起着关键作用，呼吸抑制降低Ras1活性和Ras1依赖性抑制。我们发现，细胞内ATP调节Ras1的活性，通过一个途径，涉及GTP酶激活蛋白cyr2和腺苷酸环化酶Cyr 1。根据我们的数据，在C.白念珠菌需要以这样一种方式进行重组，即Cyr 1不再位于Ras 1的下游，而是与Ras 1和Cyr 2一起位于一个主要的信号节点中。我们的研究表明，细胞的能量状态是决定C。白念珠菌进行酵母菌菌丝转换或表达与菌丝形态相关的基因，因为低细胞内ATP或相关的线索覆盖了几个菌丝诱导信号。未来的研究将表明，如果这些知识可以用来开发治疗，将有利于良性宿主念珠菌相互作用，促进低Ras 1活性。
Candida albicans is both a major fungal pathogen and a member of the commensal human microflora. The morphological switch from yeast to hyphal growth is associated with disease and many environmental factors are known to influence the yeast-to-hyphae switch. The Ras1-Cyr1-PKA pathway is a major regulator of C. albicans morphogenesis as well as biofilm formation and white-opaque switching. Previous studies have shown that hyphal growth is strongly repressed by mitochondrial inhibitors. Here, we show that mitochondrial inhibitors strongly decreased Ras1 GTP-binding and activity in C. albicans and similar effects were observed in other Candida species. Consistent with there being a connection between respiratory activity and GTP-Ras1 binding, mutants lacking complex I or complex IV grew as yeast in hypha-inducing conditions, had lower levels of GTP-Ras1, and Ras1 GTP-binding was unaffected by respiratory inhibitors. Mitochondria-perturbing agents decreased intracellular ATP concentrations and metabolomics analyses of cells grown with different respiratory inhibitors found consistent perturbation of pyruvate metabolism and the TCA cycle, changes in redox state, increased catabolism of lipids, and decreased sterol content which suggested increased AMP kinase activity. Biochemical and genetic experiments provide strong evidence for a model in which the activation of Ras1 is controlled by ATP levels in an AMP kinase independent manner. The Ras1 GTPase activating protein, Ira2, but not the Ras1 guanine nucleotide exchange factor, Cdc25, was required for the reduction of Ras1-GTP in response to inhibitor-mediated reduction of ATP levels. Furthermore, Cyr1, a well-characterized Ras1 effector, participated in the control of Ras1-GTP binding in response to decreased mitochondrial activity suggesting a revised model for Ras1 and Cyr1 signaling in which Cyr1 and Ras1 influence each other and, together with Ira2, seem to form a master-regulatory complex necessary to integrate different environmental and intracellular signals, including metabolic status, to decide the fate of cellular morphology. Candida albicans is a successful fungal commensal and pathogen of humans. It is a polymorphic organism and the ability to switch from yeast to hyphal growth is associated with the commensal-to-pathogen switch. Previous research identified the Ras1-cAMP-protein kinase A pathway as a key regulator of hyphal growth. Here, we report that mitochondrial activity plays a key role in Ras1 activation, as respiratory inhibition decreased Ras1 activity and Ras1-dependent filamentation. We found that intracellular ATP modulates Ras1 activity through a pathway involving the GTPase activating protein Ira2 and the adenylate cyclase Cyr1. Based on our data the canonical Ras1 signaling model in C. albicans needs to be restructured in such a way that Cyr1 is no longer placed downstream of Ras1 but rather in a major signaling node with Ras1 and Ira2. Our studies suggest that the energy status of the cell is the most important signal involved in the decision of C. albicans to undergo the yeast-to-hyphae switch or express genes associated with the hyphal morphology as low intracellular ATP or associated cues override several hypha-inducing signals. Future studies will show if this knowledge can be used to develop therapies that would favor benign host-Candida interactions by promoting low Ras1 activity.