Biology subjects

Todi, S. V.

Publications and source records attributed to Todi, S. V..

14 recordsLinked to original sources

bioRxiv2026

Androgen Receptor SUMO site mutations ameliorate toxicity in Drosophila models of SBMA

Spinal and bulbar muscular atrophy (SBMA) is an X-linked neurodegenerative disorder caused by a CAG trinucleotide repeat expansion in the androgen receptor (AR) gene that produces a toxic, polyglutamine-expanded protein. SBMA is part of a broader class of polyglutamine (polyQ) diseases characterized by protein misfolding, aggregation, and progressive neuronal dysfunction, for which no disease-modifying therapies exist. Post-translational modification of AR, including SUMOylation, is an important regulator of its transcriptional activity, stability, and cellular localization. Disease protein modification by SUMO is implicated in various neurodegenerative diseases and can influence protein aggregation and toxicity in polyQ disorders. Prior studies suggest that preventing AR SUMOylation positively modifies disease phenotypes. Here, we generated Drosophila models expressing polyQ-expanded human AR in which the canonical SUMO acceptor lysine sites were mutated into arginines to prevent SUMOylation of AR. Using tissue-specific expression in neurons and muscle, we assessed effects on lifespan, motor behavior, AR localization, and gene expression. Mutation of AR SUMOylation sites leads to improvements in longevity when expressed in muscle. Effects on motor performance were more limited. Transcriptomic analysis revealed tissue-specific effects of AR SUMO-site mutation, with enrichment of immune, metabolic, and defense-related processes in heads, but limited enrichment in thoraces. In both tissues, a subset of genes altered by AR SUMO-site mutation showed expression changes opposing those associated with polyQ expansion. These findings support a modulatory role for SUMOylation in SBMA pathogenesis and highlight post-translational regulation of AR as a potential therapeutic avenue requiring further investigation.

neuroscience↗

bioRxiv2026

Polyglutamine-expanded TBP rewires neuronal and muscle proteomes beyond transcription in a Drosophila model of SCA17

Spinocerebellar ataxia type 17 (SCA17) is an age-related neurodegenerative disorder caused by polyglutamine expansion in the TATA-binding protein (TBP). TBP is a core transcription factor, but pathogenic polyglutamine expansion likely rewires cellular programs beyond transcription. Here, we utilized Drosophila strains that express wild-type (WT) or pathogenic (SCA17) TBP in neurons or skeletal muscle, which we analyzed vs. controls via TMT mass spectrometry, profiling of eight post-translational modifications, and RNA-seq. Shared TBP-WT and TBP-SCA17 responses predominated, impacting ribosomes and mitochondria while repressing innate immunity. Disease-specific effects were narrower and tissue-dependent: SCA17 activated xenobiotic, retinoid, and glutathione-redox pathways in the CNS, but attenuated anabolism in muscle compared to TBP-WT. Many proteomic changes occurred independently of mRNA changes, implicating post-transcriptional mechanisms. Knockdown of select SCA17-regulated proteins reduced cytotoxicity, validating omics-identified modifiers of SCA17 pathology. These findings distinguish shared TBP dosage effects from disease-linked, tissue-specific polyglutamine responses and identify evolutionarily conserved targets for SCA17.

neuroscience↗

bioRxiv2026

Chronic alpha-Synuclein Over-Expression and Ceruloplasmin Challenge Promote Distinct Iron and Redox Responses in M17 Cells

BackgroundWhile -synuclein (-syn) accumulation and iron dysregulation are hallmarks of Parkinsons Disease, the adaptations that enable neuronal survival under chronic protein stress remain unclear. Here, we investigated how -syn overexpression and ceruloplasmin (Cp)-mediated iron modulation alters iron and redox homeostasis. MethodsWe utilized human BE(2)-M17 neuroblastoma cell lines stably expressing different levels of -syn to examine the interplay between -syn, Ceruloplasmin (Cp)-mediated iron modulation, and the cellular response to oxidative stress. Analyses included Western blotting, immunofluorescence staining, soluble/insoluble fractionation, glutathione, reactive oxygen species (ROS) and hydrogen peroxide (H2O2) quantification, lipid peroxidation, ferrous iron, and cell viability. ResultsOur data suggest an unexpected relationship between chronic -syn expression and cellular redox regulation. Despite carrying a greater -syn burden, cells with higher -syn expression exhibit lower basal ROS, H2O2, and lipid peroxidation compared to control cells. These changes are not accompanied by activation of canonical antioxidant pathways suggesting that the reduced oxidative profile arises through alternative mechanisms. Besides, -syn over-expressing cells display significant remodeling of iron-handling pathways, including altered expression of ferritin heavy chain, transferrin receptor, and ferroportin, suggesting that chronically high -syn levels are associated with changes in iron homeostasis. In addition, this phenotype is not maintained following Cp overexpression. Although Cp reduces Fe{superscript 2} levels, it also induces substantial increases in ROS and H2O2 without corresponding changes in GPX4, glutathione, or related antioxidant systems. Thus, the reduced basal oxidative profile observed in -syn-over-expressing cells does not reflect enhanced canonical antioxidant capacity. Instead, chronically high -syn levels appear to be associated with adaptive remodeling of iron and redox pathways that become sensitive to oxidative imbalance. ConclusionChronic -syn over-expression promotes adaptive remodeling of iron and redox homeostasis, associated with reduced basal oxidative stress but increased sensitivity to Cp-mediated perturbation. These data link -syn burden to iron metabolism and stress-dependent vulnerability in synucleinopathies. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=140 SRC="FIGDIR/small/732494v1_ufig1.gif" ALT="Figure 1"> View larger version (50K): org.highwire.dtl.DTLVardef@9ab785org.highwire.dtl.DTLVardef@186a200org.highwire.dtl.DTLVardef@1f5c13forg.highwire.dtl.DTLVardef@162249e_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2025

Disrupted Transcriptional Networks by Mutant Atrophin-1 in a Cell Culture Model of Dentatorubral-Pallidoluysian Atrophy

Dentatorubral-Pallidoluysian Atrophy (DRPLA) is a dominant neurodegenerative disease caused by CAG triplet repeat expansion in ATN1, which encodes the transcriptional co-repressor Atrophin-1. DRPLA features motor, cognitive, and epileptic symptoms and shares pathogenic mechanisms with other polyglutamine (polyQ) disorders, including protein misfolding, impaired autophagy, and transcriptional dysregulation. To understand disease mechanisms, we performed RNA-seq on HEK293T cells stably expressing wild-type or polyQ-expanded ATN1. Cells expressing pathogenic ATN1 exhibited a distinct transcriptomic profile, including disruptions in synaptic organization, extracellular matrix remodeling, ion channel expression, and neurotransmission. Several genes tied to neurodevelopmental, neurodegenerative, and oncogenic pathways were fully activated or silenced. Dysregulated pathways also included inflammation, chromatin remodeling, stress responses, and redox imbalance. Heat shock protein expression changes suggested proteotoxic stress and impaired protein quality control, with some findings conserved in a previously reported Drosophila melanogaster model of DRPLA. These transcriptomic signatures expand our understanding of molecular events related to degeneration in DRPLA and may lead to the identification of therapeutic targets.

neuroscience↗

bioRxiv2025

Regulation of polyamine interconversion enzymes affects α-Synuclein levels and toxicity in a Drosophila model of Parkinsons disease

Parkinson's Disease (PD) is a prevalent neurodegenerative disorder with the accumulation and aggregation of alpha-synuclein (&[alpha]-Syn) as a central pathological hallmark. Misfolding and aggregation of &[alpha]-Syn disrupts cellular homeostasis, hinders mitochondrial function, and activates neuroinflammatory responses, ultimately resulting in neuronal death. Recent biomarker research indicated a notable increase in the serum concentrations of three L-ornithine-derived polyamines (PAs): putrescine, spermidine, and spermine, each correlating with the progression of PD and its clinical subtypes. However, the role of PA pathways in PD pathology is poorly understood; it is unclear whether elevated PA concentrations are linked to PD pathology or whether they represent a secondary effect. In this study, we targeted PAs through RNAi knockdown of different PA-interconversion enzymes (PAIE) in a Drosophila melanogaster model of PD that overexpresses human, wild-type &[alpha]-Syn. Our findings reveal a significant impact on both the lifespan and motility of PD-model flies when crucial PAIE, such as ornithine decarboxylase 1 (ODC1), spermidine synthase (SRM), spermidine/spermine N1-acetyltransferase 1 (SAT1), and spermine oxidase (SMOX), are targeted. The overexpression of SAT1 and SMOX in this PD model had positive, enduring effects on fly lifespan. Additionally, we noted significant alterations in &[alpha]-Syn protein levels when PAIE are either knocked down or overexpressed. These findings underscore the role of PA pathways in PD and their potential targeting to modulate &[alpha]-Syn levels and mitigate neurodegeneration in PD.

neuroscience↗

bioRxiv2024

Insights into Dentatorubral-Pallidoluysian Atrophy from a new Drosophila model of disease

Dentatorubral-pallidoluysian atrophy (DRPLA) is a neurodegenerative disorder that presents with ataxia, dementia and epilepsy. As a member of the polyglutamine family of diseases, DRPLA is caused by abnormal CAG triplet expansion beyond 48 repeats in the protein-coding region of ATROPHIN 1 (ATN1), a transcriptional co-repressor. To better understand DRPLA, we generated new Drosophila lines that express full-length, human ATN1 with a normal (Q7) or pathogenic (Q88) repeat. Expression of ATN1 is toxic, with the polyglutamine-expanded version being consistently more problematic than wild-type ATN1. Fly motility, longevity and internal structures are negatively impacted by pathogenic ATN1. RNA-seq identified altered protein quality control and immune pathways in the presence of pathogenic ATN1. Based on these data, we conducted genetic experiments that confirmed the role of protein quality control components that ameliorate or exacerbate ATN1 toxicity. Hsc70-3, a chaperone, arose as a likely suppressor of toxicity. VCP (a proteasome-related AAA ATPase), Rpn11 (a proteasome-related deubiquitinase) and select DnaJ proteins (co-chaperones) were inconsistently protective, depending on the tissues where they were expressed. Lastly, informed by RNA-seq data that exercise-related genes may also be involved in this model of DRPLA, we conducted short-term exercise, which improved overall fly motility. This new model of DRPLA will prove important to understanding this understudied disease and will help to identify therapeutic targets for it.

neuroscience↗

bioRxiv2024

Linear ubiquitin chains remodel the proteome and influence the levels of hundreds of regulators in Drosophila

Ubiquitin controls many cellular processes via its post-translational conjugation onto substrates. Its use is highly variable due to its ability to form poly-ubiquitin with various topologies. Among them, linear chains have emerged as important regulators of immune responses and protein degradation. Previous studies in Drosophila melanogaster found that expression of linear poly-ubiquitin that cannot be dismantled into single moieties leads to their own ubiquitination and degradation or, alternatively, to their conjugation onto proteins. However, it remains largely unknown which proteins are sensitive to linear poly-ubiquitin. To address this question, here we expanded the toolkit to modulate linear chains and conducted ultra-deep coverage proteomics from flies that express non-cleavable, linear chains comprising 2, 4, or 6 moieties. We found that these chains regulate shared and distinct cellular processes in Drosophila by impacting hundreds of proteins. Our results provide key insight into the proteome subsets and cellular pathways that are influenced by linear poly-ubiquitin with distinct lengths and suggest that the ubiquitin system is exceedingly pliable.

cell biology↗

bioRxiv2023

Progressive degeneration in a new Drosophila model of Spinocerebellar Ataxia type 7

Spinocerebellar ataxia type 7 (SCA7) is a progressive neurodegenerative disorder resulting from abnormal expansion of polyglutamine (polyQ) in its disease protein, ataxin-7 (ATXN7). ATXN7 is part of Spt-Ada-Gcn5 acetyltransferase (SAGA), an evolutionarily conserved transcriptional coactivation complex with critical roles in chromatin remodeling, cell signaling, neurodifferentiation, mitochondrial health and autophagy. SCA7 is dominantly inherited and characterized by genetic anticipation and high repeat-length instability. Patients with SCA7 experience progressive ataxia, atrophy, spasticity, and blindness. There is currently no cure for SCA7, and therapies are aimed at alleviating symptoms to increase quality of life. Here, we report novel Drosophila lines of SCA7 with polyQ repeats in wild-type and human disease patient range. We find that ATXN7 expression has age- and polyQ repeat length-dependent reduction in survival and retinal instability, concomitant with increased ATXN7 protein aggregation. These new lines will provide important insight on disease progression that can be used in the future to identify therapeutic targets for SCA7 patients.

neuroscience↗

bioRxiv2023

Lysine 117 on ataxin-3 modulates toxicity in Drosophila models of Spinocerebellar Ataxia Type 3

Ataxin-3 (Atxn3) is a deubiquitinase with a polyglutamine (polyQ) repeat tract whose abnormal expansion causes the neurodegenerative disease, Spinocerebellar Ataxia Type 3 (SCA3; also known as Machado-Joseph Disease). The ubiquitin chain cleavage properties of Atxn3 are enhanced when it is ubiquitinated at lysine (K) at position 117. K117-ubiqutinated Atxn3 cleaves poly-ubiquitin more rapidly in vitro compared to its unmodified counterpart and this residue is also important for Atxn3 roles in cell culture and in Drosophila melanogaster. How polyQ expansion causes SCA3 remains unclear. To gather insight into the biology of disease of SCA3, here we posited the question: is K117 important for toxicity caused by Atxn3? We generated transgenic Drosophila lines that express full-length, human, pathogenic Atxn3 with 80 polyQ with an intact or mutated K117. We found that K117 mutation mildly enhances the toxicity and aggregation of pathogenic Atxn3 in Drosophila. An additional transgenic line that expresses Atxn3 without any K residues confirms increased aggregation of pathogenic Atxn3 whose ubiquitination is perturbed. These findings suggest Atxn3 ubiquitination as a regulatory step of SCA3, in part by modulating its aggregation.

neuroscience↗

bioRxiv2023

Phenotypic defects from the expression of wild-type and pathogenic TATA-Binding Proteins in new Drosophila models of Spinocerebellar Ataxia Type 17

Spinocerebellar Ataxia Type 17 (SCA17) is the most recently identified member of the polyglutamine (polyQ) family of disorders, resulting from abnormal CAG/CAA expansion of TATA box binding protein (TBP), an initiation factor essential for of all eukaryotic transcription. A largely autosomal dominant inherited disease, SCA17 is unique in both its heterogeneous clinical presentation and low incidence of genetic anticipation, the phenomenon in which subsequent generations inherit longer polyQ expansions that yield earlier and more severe symptom onset. Like other polyQ disease family members, SCA17 patients experience progressive ataxia and dementia, and treatments are limited to preventing symptoms and increasing quality of life. Here, we report two new Drosophila models that express human TBP with polyQ repeats in either wild-type or SCA17 patient range. We find that TBP expression has age- and tissue-specific effects on neurodegeneration, with polyQ expanded SCA17 protein expression generally having more severe effects. In addition, SCA17 model flies accumulate more aggregation prone TBP, with a greater proportion localizing to the nucleus. These new lines provide a new resource for the biochemical characterization of SCA17 pathology and the future identification of therapeutic targets.

neuroscience↗

bioRxiv2023

A phenotypically robust model of Spinal and Bulbar Muscular Atrophy in Drosophila

Spinal and bulbar muscular atrophy (SBMA) is an X-linked disorder that affects males who inherit the androgen receptor (AR) gene with an abnormal CAG triplet repeat expansion. The resulting protein contains an elongated polyglutamine (polyQ) tract and causes motor neuron degeneration in an androgen-dependent manner. The precise molecular sequelae of SBMA are unclear. To assist with its investigation and the identification of therapeutic options, we report here a new model of SBMA in Drosophila melanogaster. We generated transgenic flies that express the full-length, human AR with a wild-type or pathogenic polyQ repeat. Each transgene is inserted into the same "safe harbor" site on the third chromosome of the fly as a single copy and in the same orientation. Expression of pathogenic AR, but not of its wild-type variant, in neurons or muscles leads to consistent, progressive defects in longevity and motility that are concomitant with polyQ-expanded AR protein aggregation and reduced complexity in neuromuscular junctions. Additional assays show adult fly eye abnormalities associated with the pathogenic AR species. The detrimental effects of pathogenic AR are accentuated by feeding flies the androgen, dihydrotestosterone. This new, robust SBMA model can be a valuable tool towards future investigations of this incurable disease.

neuroscience↗

bioRxiv2023

Regional and age-dependent changes in ubiquitination in cellular and mouse models of Spinocerebellar ataxia type 3

1Spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph disease, is the most common dominantly inherited ataxia. SCA3 is caused by a CAG repeat expansion in the ATXN3 gene that encodes an expanded tract of polyglutamine (polyQ) in the disease protein ataxin-3 (ATXN3). As a deubiquitinating enzyme, ATXN3 regulates numerous cellular processes including proteasome- and autophagy-mediated protein degradation. In SCA3 disease brain, polyQ-expanded ATXN3 accumulates with other cellular constituents, including ubiquitin (Ub)-modified proteins, in select areas like the cerebellum and the brainstem, but whether pathogenic ATXN3 affects the abundance of ubiquitinated species is unknown. Here, in mouse and cellular models of SCA3, we investigated whether elimination of murine Atxn3 or expression of wild-type or polyQ-expanded human ATXN3 alters soluble levels of overall ubiquitination, as well as K48-linked (K48-Ub) and K63-linked (K63-Ub) chains. Levels of ubiquitination were assessed in the cerebellum and brainstem of 7- and 47-week-old Atxn3 knockout and SCA3 transgenic mice, and also in relevant mouse and human cell lines. In older mice, we observed that wild-type ATXN3 impacts the cerebellar levels of K48-Ub proteins. In contrast, pathogenic ATXN3 leads to decreased brainstem abundance of K48-Ub species in younger mice and changes in both cerebellar and brainstem K63-Ub levels in an age-dependent manner: younger SCA3 mice have higher levels of K63-Ub while older mice have lower levels of K63-Ub compared to controls. Human SCA3 neuronal progenitor cells also show a relative increase in K63-Ub proteins upon autophagy inhibition. We conclude that wild-type and mutant ATXN3 differentially impact K48-Ub- and K63-Ub-modified proteins in the brain in a region- and age-dependent manner.

neuroscience↗

bioRxiv2021

Endurance exercise ameliorates phenotypes in Drosophila models of Spinocerebellar Ataxias

Endurance exercise is a potent intervention with widespread benefits proven to reduce disease incidence and impact across species. While endurance exercise supports neural plasticity, enhanced memory, and reduced neurodegeneration, less is known about the effect of chronic exercise on the progression of movement disorders such as ataxias. Here, we focused on three different types of ataxias, Spinocerebellar Ataxias Type (SCAs) 2, 3, and 6, belonging to the polyglutamine (polyQ) family of neurodegenerative disorders. In Drosophila models of these SCAs, flies progressively lose motor function. Here, we observe marked protection of speed and endurance in exercised SCA2 flies and modest protection in exercised SCA6 models, while no benefit is observed in SCA3 flies. Causative protein levels are reduced in SCA2 flies after chronic exercise, but not in SCA3 models, linking protein levels to exercise-based benefits. Additional investigations indicate that the exercise-inducible protein, Sestrin (Sesn) suppresses mobility decline and improves early death in SCA2 flies, even without exercise, coincident with disease protein level reduction and increased autophagic flux. These improvements depend on previously established functions of Sesn that reduce oxidative damage and modulate mTOR activity. Our study suggests differential responses of polyQ SCAs to exercise, highlighting the potential for more extensive application of exercise-based therapies in the prevention of polyQ neurodegeneration. Defining the mechanisms by which endurance exercise suppresses polyQ SCAs will open the door for more effective treatment for these diseases.

neuroscience↗

bioRxiv2019

Druggable genome screen identifies new regulators of the abundance and toxicity of ATXN3, the Spinocerebellar Ataxia Type 3 disease protein

BackgroundSpinocerebellar Ataxia type 3 (SCA3, also known as Machado-Joseph disease) is a neurodegenerative disorder caused by a CAG repeat expansion encoding an abnormally long polyglutamine (polyQ) tract in the disease protein, ataxin-3 (ATXN3). No preventive treatment is yet available for SCA3. Because SCA3 is likely caused by a toxic gain of ATXN3 function, a rational therapeutic strategy is to reduce mutant ATXN3 levels by targeting pathways that control its production or stability. Here, we sought to identify genes that modulate ATXN3 levels as potential therapeutic targets in this fatal disorder.\n\nMethodsWe screened a collection of siRNAs targeting 2742 druggable human genes using a cell-based assay based on luminescence readout of polyQ-expanded ATXN3. From 317 candidate genes identified in the primary screen, 100 genes were selected for validation. Among the 33 genes confirmed in secondary assays, 15 were validated in an independent cell model as modulators of pathogenic ATXN3 protein levels. Ten of these genes were then assessed in a Drosophila model of SCA3, and one was confirmed as a key modulator of physiological ATXN3 abundance in SCA3 neuronal progenitor cells.\n\nResultsAmong the 15 genes shown to modulate ATXN3 in mammalian cells, orthologs of CHD4, FBXL3, HR and MC3R regulate mutant ATXN3-mediated toxicity in fly eyes. Further mechanistic studies of one of these genes, FBXL3, encoding a F-box protein that is a component of the SKP1-Cullin-F-box (SCF) ubiquitin ligase complex, showed that it reduces levels of normal and pathogenic ATXN3 in SCA3 neuronal progenitor cells, primarily via a SCF complex-dependent manner. Bioinformatic analysis of the 15 genes revealed a potential molecular network with connections to tumor necrosis factor-/nuclear factor-kappa B (TNF/NF-kB) and extracellular signal-regulated kinases 1 and 2 (ERK1/2) pathways.\n\nConclusionsWe identified 15 druggable genes with diverse functions to be suppressors or enhancers of pathogenic ATXN3 abundance. Among identified pathways highlighted by this screen, the FBXL3/SCF axis represents a novel molecular pathway that regulates physiological levels of ATXN3 protein.

neuroscience↗