Identifying Gene Functions at Late Endosome and Lysosome in Yeast

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DESCRIPTION (provided by applicant): Correct sorting and vesicular trafficking of molecules to the degradative lysosome is an essential feature of all eukaryotic cells. The late endosome and vacuole of the yeast Saccharomyces cerevisiae are functionally equivalent to the mammalian late endosome and lysosome; its carboxy peptidase Y (CPY)-pathway of vacuolar delivery parallels the mannose-6-phosphate pathway in mammalian cells. Yeast offers the advantage of both conventional and molecular genetics tools; large majority of yeast genes identified in lysosomal trafficking have orthologues in humans. Results of two separate genome wide screens for vacuolar trafficking and function related genes have led us to 1)several previously uncharacterized genes that have a role at endosome and vacuole interface (ENV genes), 2) a small set of genes involved in vacuolar trafficking and function that confer severe hypersensitivity to hygromycin B when deleted (HHY genes). Furthermore, all hhy mutants also showed drug hypersensitivities indicative of defective TOR kinase signaling, a master regulator of cell growth and proliferation through nutrient and growth factor sensing. In this competitive renewal, we propose multifaceted characterization of the novel gene ENV9 which has significant identity to human retinol dehydrogenase RDH12 - a gene implicated in early onset retinal degeneration. We also propose to explore the interface of vacuolar trafficking, TOR kinase signaling, and hygromycin B hypersensitivity by yeast genetics, molecular, and microscopic approaches. Inherent in this AREA proposal, is the aim to continue development of a minority post-doctoral researcher and continue productive research training of undergraduate and Master's students within a comprehensive Hispanic Serving Institute. Mislocalization of lysosomal proteases and cargo is associated with Lysosomal Storage Diseases and Alzheimer's disease (AD). Defects specifically at the late endosome to lysosome stage of trafficking have emerged as the possible underlying mechanism in both juvenile and aging neurodegeneration diseases. Hyper activation of TOR kinase signaling is associated with benign and malignant tumorigenesis, as well as with metabolic diseases including diabetes and obesity. PUBLIC HEALTH RELEVANCE: The proposed research is relevant to public health issues associated with both juvenile and late onset neurodegeneration as manifested in Lysosomal Storage Diseases and Alzheimer's disease, respectively. It is also relevant to public health issues associated with tumorigenesis and metabolic diseases including diabetes and obesity.