Browsing by Author "D’Alessandro, Angelo"

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    Hypoxia-inducible factor 1α is required to establish the larval glycolytic program in Drosophila melanogaster
    (bioRxiv, 2025-01-08) Heidarian, Yasaman; Fasteen, Tess D.; Mungcal, Liam; Buddika, Kasun; Mahmoudzadeh, Nader H.; Nemkov, Travis; D’Alessandro, Angelo; Tennessen, Jason M.; Medicine, School of Medicine
    The rapid growth that occurs during Drosophila larval development requires a dramatic rewiring of central carbon metabolism to support biosynthesis. Larvae achieve this metabolic state, in part, by coordinately up-regulating the expression of genes involved in carbohydrate metabolism. The resulting metabolic program exhibits hallmark characteristics of aerobic glycolysis and establishes a physiological state that supports growth. To date, the only factor known to activate the larval glycolytic program is the Drosophila Estrogen-Related Receptor (dERR). However, dERR is dynamically regulated during the onset of this metabolic switch, indicating that other factors must be involved. Here we discover that Sima, the Drosophila ortholog of Hif1α, is also essential for establishing the larval glycolytic program. Using a multi-omics approach, we demonstrate that sima mutants fail to properly activate aerobic glycolysis and die during larval development with metabolic defects that phenocopy dERR mutants. Moreover, we demonstrate that dERR and Sima/Hif1α protein accumulation is mutually dependent, as loss of either transcription factor results in decreased abundance of the other protein. Considering that the mammalian homologs of ERR and Hif1α also cooperatively regulate aerobic glycolysis in cancer cells, our findings establish the fly as a powerful genetic model for studying the interaction between these two key metabolic regulators.
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    Hypoxia-inducible factor 1α is required to establish the larval glycolytic program in Drosophila melanogaster
    (Elsevier, 2025) Heidarian, Yasaman; Fasteen, Tess D.; Mungcal, Liam; Buddika, Kasun; Mahmoudzadeh, Nader H.; Nemkov, Travis; D’Alessandro, Angelo; Tennessen, Jason M.; Biology, School of Science
    Objectives: The rapid growth that occurs during Drosophila larval development requires a dramatic rewiring of central carbon metabolism to support biosynthesis. Larvae achieve this metabolic state, in part, by coordinately up-regulating the expression of genes involved in carbohydrate metabolism. The resulting metabolic program exhibits hallmark characteristics of aerobic glycolysis and establishes a physiological state that supports growth. To date, the only factor known to activate the larval glycolytic program is the Drosophila Estrogen-Related Receptor (dERR). However, dERR is dynamically regulated during the onset of this metabolic switch, indicating that other factors must be involved. Here we examine the possibility that the Drosophila ortholog of Hypoxia inducible factor 1α (Hif1α) is also required to activate the larval glycolytic program. Methods: CRISPR/Cas9 was used to generate new loss-of-function alleles in the Drosophila gene similar (sima), which encodes the sole fly ortholog of Hif1α. The resulting mutant strains were analyzed using a combination of metabolomics and RNAseq for defects in carbohydrate metabolism. Results: Our studies reveal that sima mutants fail to activate aerobic glycolysis and die during larval development with metabolic phenotypes that mimic those displayed by dERR mutants. Moreover, we demonstrate that dERR and Sima/Hif1α protein accumulation is mutually dependent, as loss of either transcription factor results in decreased abundance of the other protein. Conclusions: These findings demonstrate that Sima/HIF1α is required during embryogenesis to coordinately up-regulate carbohydrate metabolism in preparation for larval growth. Notably, our study also reveals that the Sima/HIF1α-dependent gene expression program shares considerable overlap with that observed in dERR mutant, suggesting that Sima/HIF1α and dERR cooperatively regulate embryonic and larval glycolytic gene expression.
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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.