Biology subjects

Mahmoudzadeh, N. H.

Publications and source records attributed to Mahmoudzadeh, N. H..

6 recordsLinked to original sources

bioRxiv2025

Hypoxia-inducible factor 1α is required to establish the larval glycolytic program in Drosophila melanogaster

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 Hif1, 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/Hif1 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 Hif1 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. STRUCTURED ABSTRACTO_ST_ABSObjectivesC_ST_ABSThe 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 the Drosophila ortholog of Hypoxia inducible factor 1 (Hif1) is also required to activate the larval glycolytic program. MethodsCRISPR/Cas9 was used to generate new loss-of-function alleles in the Drosophila gene similar (sima), which encodes the sole fly ortholog of Hif1. The resulting mutant strains were analyzed using a combination of metabolomics and RNAseq for defects in carbohydrate metabolism. ResultsOur 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/Hif1 protein accumulation is mutually dependent, as loss of either transcription factor results in decreased abundance the other protein. ConclusionsThese findings demonstrate that Sima/HIF1 is required during embryogenesis to coordinately up-regulate carbohydrate metabolism in preparation for larval growth. Notably, our study also reveals that the Sima-dependent gene expression profile shares considerable overlap with that observed in dERR mutant, suggesting that Sima/HIF1 and dERR cooperatively regulate embryonic and larval glycolytic gene expression. HIGHLIGHTSO_LIThe Drosophila melanogaster gene similar (sima), which encodes the sole fly ortholog of Hif1, is required to up-regulate glycolysis in preparation for larval growth. C_LIO_LIsima mutant larvae exhibit severe defects in carbohydrate metabolism and die during the second larval instar. C_LIO_LIsima mutant larvae exhibit the same metabolic phenotypes as Drosophila Estrogen Related Receptor (dERR) mutants, suggesting that these two transcription factors coordinately regulate the larval glycolytic program. C_LIO_LISima/Hif1 and dERR accumulation is mutually dependent, as loss of either transcription factor results in decreased abundance of the other. C_LI

developmental biology↗

bioRxiv2024

Renal L-2-hydroxyglutarate dehydrogenase activity promotes hypoxia tolerance and mitochondrial metabolism in Drosophila melanogaster

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. 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 (Malpighian tubules; MTs) 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. Overall, our 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.

genetics↗

bioRxiv2023

Metabolomic analysis of Drosophila melanogaster larvae lacking Pyruvate kinase

Pyruvate kinase (Pyk) is a rate-limiting enzyme that catalyzes the final metabolic reaction in glycolysis. The importance of this enzyme, however, extends far beyond ATP production, as Pyk is also known to regulate tissue growth, cell proliferation, and development. Studies of this enzyme in Drosophila melanogaster, however, are complicated by the fact that the fly genome encodes six Pyk paralogs whose functions remain poorly defined. To address this issue, we used sequence distance and phylogenetic approaches to demonstrate that the gene Pyk encodes the enzyme most similar to the mammalian Pyk orthologs, while the other five Drosophila Pyk paralogs have significantly diverged from the canonical enzyme. Consistent with this observation, metabolomic studies of two different Pyk mutant backgrounds revealed that larvae lacking Pyk exhibit a severe block in glycolysis, with a buildup of glycolytic intermediates upstream of pyruvate. However, our analysis also unexpectedly reveals that steady state pyruvate levels are unchanged in Pyk mutants, indicating that larval metabolism maintains pyruvate pool size despite severe metabolic limitations. Consistent with our metabolomic findings, a complementary RNA-seq analysis revealed that genes involved in lipid metabolism and peptidase activity are elevated in Pyk mutants, again indicating that loss of this glycolytic enzyme induces compensatory changes in other aspects of metabolism. Overall, our study provides both insight into how Drosophila larval metabolism adapts to disruption of glycolytic metabolism as well as immediate clinical relevance, considering that Pyk deficiency is the most common congenital enzymatic defect in humans.

developmental biology↗

bioRxiv2022

Aging and memory are altered by genetically manipulating lactate dehydrogenase in the neurons or glia of flies

The astrocyte-neuron lactate shuttle hypothesis posits that glial-generated lactate is transported to neurons to fuel metabolic processes required for long-term memory. Although studies in vertebrates have revealed that lactate shuttling is important for cognitive function, it is uncertain if this form of metabolic coupling is conserved in invertebrates or is influenced by age. Lactate dehydrogenase (Ldh) is a rate limiting enzyme that interconverts lactate and pyruvate. Here we genetically manipulated expression of Drosophila melanogaster lactate dehydrogenase (dLdh) in neurons or glia to assess the impact of altered lactate metabolism on invertebrate aging and long-term courtship memory at different ages. We also assessed survival, negative geotaxis, brain neutral lipids (the core component of lipid droplets) and brain metabolites. Both upregulation and downregulation of dLdh in neurons resulted in decreased survival and memory impairment with age. Glial downregulation of dLdh expression caused age-related memory impairment without altering survival, while upregulated glial dLdh expression lowered survival without disrupting memory. Both neuronal and glial dLdh upregulation increased neutral lipid accumulation. We provide evidence that altered lactate metabolism with age affects the tricarboxylic acid (TCA) cycle, 2-hydroxyglutarate (2HG), and neutral lipid accumulation. Collectively, our findings indicate that the direct alteration of lactate metabolism in either glia or neurons affects memory and survival but only in an age-dependent manner. Author SummaryThe brain is composed of metabolically demanding cell types that must remain functional throughout life to maintain cognitive tasks like memory formation. How brain metabolism varies between cell-types across the lifespan is uncertain. It has been suggested that in vertebrate brains glia breakdown sugars to produce lactate and shuttle it to neurons to support long-term memory and survival. Yet, this phenomenon has not been directly tested in invertebrates. In Drosophila melanogaster flies, we genetically manipulated lactate dehydrogenase, a central enzyme in lactate metabolism, specifically within the adult brain. We discovered that shifting lactate metabolism to either higher or lower levels in neurons caused decreased survival and worse long-term memory with age. In contrast, we found increased glial lactate metabolism worsened survival, whereas decreased glial lactate metabolism impaired long-term memory in aged flies. Both increased glial or neuronal lactate metabolism led to increased accumulation of metabolites, such as 2-hydroxyglutarate, mitochondrial metabolites, and neutral lipids, in aged fly brains. These findings provide evidence for the first time in invertebrates that lactate and memory are connected and altered lactate metabolism in neurons and glia differentially impact survival and memory, but only in an age-dependent manner. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=83 SRC="FIGDIR/small/512981v1_ufig1.gif" ALT="Figure 1"> View larger version (17K): org.highwire.dtl.DTLVardef@6b34d7org.highwire.dtl.DTLVardef@5a159forg.highwire.dtl.DTLVardef@41a3f6org.highwire.dtl.DTLVardef@17377ea_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2022

The Drosophila melanogaster enzyme glycerol-3-phosphate dehydrogenase 1 is required for oogenesis, embryonic development, and amino acid homeostasis

As the fruit fly, Drosophila melanogaster, progresses from one life stage to the next, many of the enzymes that compose intermediary metabolism undergo substantial changes in both expression and activity. These predictable shifts in metabolic flux allow the fly meet stage-specific requirements for energy production and biosynthesis. In this regard, the enzyme Glyerol-3-phosphate dehydrogenase (GPDH1) has been the focus of biochemical genetics studies for several decades, and as a result, is one of the most well characterized Drosophila enzymes. Among the findings of these earlier studies is that GPDH1 acts throughout the fly lifecycle to promote mitochondrial energy production and triglyceride accumulation while also serving a key role in maintaining redox balance. Here we expand upon the known roles of GPDH1 during fly development by examining how depletion of both the maternal and zygotic pools of this enzyme influences development, metabolism, and viability. Our findings not only confirm previous observations that Gpdh1 mutants exhibit defects in larval development, lifespan, and fat storage but also reveal that GPDH1 serves essential roles in oogenesis and embryogenesis. Moreover, metabolomics analysis reveals that a Gpdh1 mutant stock maintained in a homozygous state exhibits larval metabolic defects that significantly differ from those observed in the F1 mutant generation. Overall, our findings highlight unappreciated roles for GPDH1 in early development and uncover previously undescribed metabolic adaptations that could allow flies to survive loss of this key enzyme.

developmental biology↗

bioRxiv2020

The oncometabolite L-2-hydroxyglutarate is a common product of Dipteran larval development

The oncometabolite L-2-hydroxyglutarate (L-2HG) is considered an abnormal product of central carbon metabolism that is capable of disrupting chromatin architecture, mitochondrial metabolism, and cellular differentiation. Under most circumstances, mammalian tissues readily dispose of this compound, as aberrant L-2HG accumulation induces neurometabolic disorders and promotes renal cell carcinomas. Intriguingly, Drosophila melanogaster larvae were recently found to accumulate high L-2HG levels under normal growth conditions, raising the possibility that L-2HG plays a unique role in insect metabolism. Here we explore this hypothesis by analyzing L-2HG levels in 18 insect species. While L-2HG was present at low-to-moderate levels in most of these species (<100 pmol/mg; comparable to mouse liver), Dipteran larvae exhibited a tendency to accumulate high L-2HG concentrations (>100 pmol/mg), with the mosquito Aedes aegypti, the blow fly Phormia regina, and three representative Drosophila species harboring concentrations that exceed 1 nmol/mg - levels comparable to those measured in mutant mice that are unable to degrade L-2HG. Overall, our findings suggest that one of the largest groups of animals on earth commonly generate high concentrations of an oncometabolite during juvenile growth, hint at a role for L-2HG in the evolution of Dipteran development, and raise the possibility that L-2HG metabolism could be targeted to restrict the growth of key disease vectors and agricultural pests.

developmental biology↗