Fungal Pheromone Receptors in Host-Pathogen Interactions

G蛋白偶联受体（GPCR）形成细胞表面受体的超家族，其在真核生物分类群中发现，例如仅在人类中就有>800种独特的GPCR。真菌的Step2 p和Step 3 p GPCR介导交配反应，通过信息素刺激受体，导致记录良好的信号转导事件，细胞周期停滞和细胞融合。然而，最近的一些研究结果表明，这些信息素受体的相关性和相关机制可能比这更广泛。一方面，最近的一份报告暗示了Step2 p参与了病原真菌对宿主的过氧化物酶介导的化学吸引。另一方面，发现了"偏置信号“，其中单个GPCR可以被多种不同的配体刺激，每种配体刺激不同的G亚基和抑制蛋白。我们自己最近的工作已经产生了证据，突出了酵母Ste 2 p在经典细胞周期停滞与下游细胞壁降解/突起形成中的偏倚功能的可能性，以及抑制蛋白在介导这些后者反应中的可能作用。这些发现共同提出了这样的假设，即宿主-病原体化学吸引的Ste 2 p相关机制在致病真菌中是保守的，并且刺激反应的配体的性质是过氧化物酶修饰的细胞壁组分，其选择性地刺激抑制蛋白相关的偏置信号传导途径。 我们将通过真菌遗传实验，半靶向代谢组学，并在长期的组合，经典的重组分析结合定点诱变功能测定和结构研究来测试这一假设。这项研究计划将使3个硕士和2个博士研究生在遗传学，细胞生物学和生物化学（包括）领域的培训。代谢组学和计算/结构生物学）。真菌感染是一个广泛的问题，影响人类和牲畜的健康以及大多数农作物的生产力。该提案针对的是禾谷镰刀菌，这是谷类作物中镰刀菌头枯病（FHB）的病原体，包括有害真菌毒素的沉积。仅在加拿大，FHB每年就造成数百万美元的经济损失，并更广泛地威胁世界粮食供应。 常用的抗真菌药通常都是通过靶向真菌细胞膜的可塑性来起作用的。然而，耐药性正在发展，目前缺乏特异性会影响环境中的其他生物。当务之急是开发具有替代作用模式的新的更特异性的抗真菌药。为了实现这一点，我们必须完全了解真菌感染的基础。

G-protein Coupled Receptors (GPCRs) form a superfamily of cell surface receptors that are found across eukaryotic taxa, with, for example >800 unique GPCRs in humans alone. The fungal Ste2p and Ste3p GPCRs mediate mating responses, with stimulation of the receptors by pheromones leading to well-documented signal transduction events, cell-cycle arrest and cellular fusion. However a number of recent findings suggest the relevance and associated mechanisms of these pheromone receptors may be much broader than this. On the one hand, a recent report has implicated Ste2p in the peroxidase-mediated chemo-attraction of pathogenic fungi to hosts. On the other hand, is the discovery of biased-signalling' where individual GPCRs can be stimulated by multiple different ligands, each stimulating different G subunits and arrestins. Our own recent work has yielded evidence highlighting the possibility of biased' functionalities for yeast Ste2p in classical cell cycle arrest versus downstream cell wall degradation/projection formation, and a possible role for arrestins in mediating these latter responses.****Together these findings raise the hypothesis that the Ste2p associated mechanism of host-pathogen chemo-attraction is conserved across pathogenic fungi, and that the nature of the ligand stimulating the response is a peroxidase-modified cell wall component selectively stimulating an arrestin-associated biased-signaling pathway. We will test this hypothesis through a combination of fungal genetic experiments, semi-targeted metabolomics, and in the longer-term, classical recombinant analyses combining site directed mutagenesis with functional assays and structural investigations. This program of research will enable the training of 3 MSc and 2 PhD graduate students in the fields of genetics, cell biology and biochemistry (incl. metabolomics and computational/structural biology).****Fungal infection is a broad-spectrum problem, affecting the health of humans and livestock as well as the productivity of most agricultural crops. Targeted in this proposal is Fusarium graminearum, the causative agent of Fusarium Head Blight (FHB) in cereal crops, which includes deposition of hazardous mycotoxins. FHB causes $ 100's of millions in economic losses annually in Canada alone, and threatens world food supplies more broadly. Commonly used antifungals generally all work by targeting the plasticity of the fungal cell membrane. However resistance is developing, and the current lack of specificity impacts other organisms in the environment. It is imperative that new more specific antifungals, with alternate modes of action, are developed. To enable this, it is essential that we have a complete understanding of the basis of fungal infection.*********