Grant: Discovery Grants Program - Individual

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.