Browsing by Author "Buddika, Kasun"

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    Renal L-2-hydroxyglutarate dehydrogenase activity promotes hypoxia tolerance and mitochondrial metabolism in Drosophila melanogaster
    (Elsevier, 2024) Mahmoudzadeh, Nader H.; Heidarian, Yasaman; Tourigny, Jason P.; Fitt, Alexander J.; Beebe, Katherine; Li, Hongde; Luhur, Arthur; Buddika, Kasun; Mungcal, Liam; Kundu, Anirban; Policastro, Robert A.; Brinkley, Garrett J.; Zentner, Gabriel E.; Nemkov, Travis; Pepin, Robert; Chawla, Geetanjali; Sudarshan, Sunil; Rodan, Aylin R.; D’Alessandro, Angelo; Tennessen, Jason M.; Medicine, School of Medicine
    Objectives: The mitochondrial enzyme L-2-hydroxyglutarate dehydrogenase (L2HGDH) regulates the abundance of L-2-hydroxyglutarate (L-2HG), a potent signaling metabolite capable of influencing chromatin architecture, mitochondrial metabolism, and cell fate decisions. Loss of L2hgdh activity in humans induces ectopic L-2HG accumulation, resulting in neurodevelopmental defects, altered immune cell function, and enhanced growth of clear cell renal cell carcinomas. To better understand the molecular mechanisms that underlie these disease pathologies, we used the fruit fly Drosophila melanogaster to investigate the endogenous functions of L2hgdh. Methods: L2hgdh mutant adult male flies were analyzed under normoxic and hypoxic conditions using a combination of semi-targeted metabolomics and RNA-seq. These multi-omic analyses were complemented by tissue-specific genetic studies that examined the effects of L2hgdh mutations on the Drosophila renal system (Malpighian tubules; MTs). Results: Our studies revealed that while L2hgdh is not essential for growth or viability under standard culture conditions, L2hgdh mutants are hypersensitive to hypoxia and expire during the reoxygenation phase with severe disruptions of mitochondrial metabolism. Moreover, we find that the fly renal system is a key site of L2hgdh activity, as L2hgdh mutants that express a rescuing transgene within the MTs survive hypoxia treatment and exhibit normal levels of mitochondrial metabolites. We also demonstrate that even under normoxic conditions, L2hgdh mutant MTs experience significant metabolic stress and are sensitized to aberrant growth upon Egfr activation. Conclusions: These findings present a model in which renal L2hgdh activity limits systemic L-2HG accumulation, thus indirectly regulating the balance between glycolytic and mitochondrial metabolism, enabling successful recovery from hypoxia exposure, and ensuring renal tissue integrity.
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    The RNA-binding protein Swm is critical for Drosophila melanogaster intestinal progenitor cell maintenance
    (Oxford University Press, 2022) Ariyapala, Ishara S.; Buddika, Kasun; Hundley, Heather A.; Calvi, Brian R.; Sokol, Nicholas S.; Medicine, School of Medicine
    The regulation of stem cell survival, self-renewal, and differentiation is critical for the maintenance of tissue homeostasis. Although the involvement of signaling pathways and transcriptional control mechanisms in stem cell regulation have been extensively investigated, the role of post-transcriptional control is still poorly understood. Here, we show that the nuclear activity of the RNA-binding protein Second Mitotic Wave Missing is critical for Drosophila melanogaster intestinal stem cells and their daughter cells, enteroblasts, to maintain their progenitor cell properties and functions. Loss of swm causes intestinal stem cells and enteroblasts to stop dividing and instead detach from the basement membrane, resulting in severe progenitor cell loss. swm loss is further characterized by nuclear accumulation of poly(A)+ RNA in progenitor cells. Second Mitotic Wave Missing associates with transcripts involved in epithelial cell maintenance and adhesion, and the loss of swm, while not generally affecting the levels of these Second Mitotic Wave Missing-bound mRNAs, leads to elevated expression of proteins encoded by some of them, including the fly ortholog of Filamin. Taken together, this study indicates a nuclear role for Second Mitotic Wave Missing in adult stem cell maintenance, raising the possibility that nuclear post-transcriptional regulation of mRNAs encoding cell adhesion proteins ensures proper attachment of progenitor cells.