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The atypical antipsychotic aripiprazole is a Food and Drug Administration-approved drug for the treatment of psychotic, mood, and other psychiatric disorders. Previous drug discovery efforts pinpointed aripiprazole as an effective suppressor of Machado–Joseph disease (MJD) pathogenesis, as its administration resulted in a reduced abundance and aggregation of mutant Ataxin-3 (ATXN3) proteins. Dopamine partial agonism and functional selectivity have been proposed as the main pharmacological mechanism of action of aripiprazole in the treatment of psychosis; however, this mechanism remains to be determined in the context of MJD. Here, we focus on confirming the efficacy of aripiprazole to reduce motor dysfunction in vivo, using a Caenorhabditis elegans (C. elegans) model of MJD, and on unveiling the drug targets required for its positive action against mutant ATXN3 pathogenesis. We employed pharmacogenetics and pharmacological approaches to identify which dopamine and serotonin receptors are critical for aripiprazole-mediated improvements in motor function. We demonstrated that dopamine D2-like and serotonin 5-HT1A and 5-HT2A receptors play important roles in this process. Our findings strengthen the relevance of dopaminergic and serotoninergic signaling modulation against mutant ATXN3-mediated pathogenesis. The identification of aripiprazole’s cellular targets, relevant for MJD and perhaps other neurodegenerative diseases, may pave the way for prospective drug discovery and development campaigns aiming to improve the features of this prototypical compound and reduce side effects not negligible in the case of aripiprazole.

Hemerocallis citrina is an herbaceous perennial plant used in Asian cuisine and Traditional Chinese Medicine. Here, we tested the therapeutic potential of extracts (HCE30%, HCE50%, and HCN) in vivo, using models of two human genetic neurodegenerative diseases—Machado–Joseph Disease/Spinocerebellar Ataxia type 3 (MJD/SCA3) and Frontotemporal Dementia with Parkinsonism associated to chromosome 17 (FTDP-17). Chronic treatment with HCE30% extract ameliorated the motor deficits typically observed in these models. Interestingly, we found that the effect on the motor phenotype of the MJD/SCA3 model was dependent on serotonergic signaling and on the action of the HLH-30/TFEB transcription factor, known to regulate the cellular response to amino acid starvation, the autophagy and mitophagy pathways, lysosome localization and biogenesis, exocytosis, and mitochondrial biogenesis. Altogether, our findings reinforce the idea that phytochemicals act through the modulation of serotonergic neurotransmission and introduce a novel layer to the HLH-30/TFEB regulatory network. Thus, it also strengthens the use of these pathways as therapeutic targets for protein-related neurodegenerative disorders and confirms the utility of medicinal plants as a source of innovation in the quest for new therapeutic agents.

Aim: Experimental models are a powerful aid in visualizing molecular phenomena. This work reports how the worm Caenorhabditis elegans (C. elegans) can be effectively explored for students to learn how molecular cues dramatically condition axonal guidance and define nervous system structure and behavior at the organism level. Summary of work: A loosely oriented observational activity preceded detailed discussions on molecules implied in axonal migration. C. elegans mutants were used to introduce second-year medical students to the deleterious effects of gene malfunctioning in neuron response to extracellular biochemical cues and to establish links between molecular function, nervous system structure, and animal behavior. Students observed C. elegans cultures and associated animal behavior alterations with the lack of function of specific axon guidance molecules (the soluble cue netrin/UNC-6 or two receptors, DCC/UNC-40 and UNC-5H). Microscopical observations of these strains, in combination with pan-neuronal GFP expression, allowed optimal visualization of severely affected neurons. Once the list of mutated genes in each strain was displayed, students could also relate abnormal patterns in axon migration/ventral and dorsal nerve cord neuron formation in C. elegans with mutated molecular components homologous to those in humans. Summary of results: Students rated the importance and effectiveness of the activity very highly. Ninety-three percent found it helpful to grasp human axonal migration, and all students were surprised with the power of the model in helping to visualize the phenomenon.

Spinocerebellar ataxia type 3 (SCA3) is an adult-onset neurodegenerative disease caused by a polyglutamine expansion in the ataxin-3 (ATXN3) gene. No effective treatment is available for this disorder, other than symptom-directed approaches. Bile acids have shown therapeutic efficacy in neurodegenerative disease models. Here, we pinpointed tauroursodeoxycholic acid (TUDCA) as an efficient therapeutic, improving the motor and neuropathological phenotype of SCA3 nematode and mouse models. Surprisingly, transcriptomic and functional in vivo data showed that TUDCA acts in neuronal tissue through the glucocorticoid receptor (GR), but independently of its canonical receptor, the farnesoid X receptor (FXR). TUDCA was predicted to bind to the GR, in a similar fashion to corticosteroid molecules. GR levels were decreased in disease-affected brain regions, likely due to increased protein degradation as a consequence of ATXN3 dysfunction being restored by TUDCA treatment. Analysis of a SCA3 clinical cohort showed intriguing correlations between the peripheral expression of GR and the predicted age at disease onset in presymptomatic subjects and FKBP5 expression with disease progression, suggesting this pathway as a potential source of biomarkers for future study. We have established a novel in vivo mechanism for the neuroprotective effects of TUDCA in SCA3 and propose this readily available drug for clinical trials in SCA3 patients.

Spinocerebellar Ataxia Type‐3 Therapies The molecular tweezer CLR01 binds an allosteric site on the Josephin domain of ataxin‐3, reducing conformational flexibility and limiting motions that expose the aggregation‐prone region. Concentric circles evoke the ripple of allosteric modulation extending across biological scales, delaying amyloid formation and disease progression in neurons, C. elegans, and mouse models. More details can be found in the Research Article by Patrícia Maciel, Sandra Macedo‐Ribeiro, and co‐workers (DOI: 10.1002/advs.202502216). Artwork by Weronika Przekorzynska.

Spinocerebellar ataxia type 3 (SCA3) is a rare neurodegenerative disorder caused by the expansion of a polyglutamine (polyQ) repeat in ataxin‐3 (Atx3) for which no disease‐modifying therapies are available. The presence of protein inclusions enriched in polyQ‐expanded Atx3 in neurons suggests that inhibiting its self‐assembly may provide targeted therapies. Here, it is demonstrated that the supramolecular tweezer CLR01 binds to a lysine residue on a positively charged patch of the Atx3 catalytic Josephin domain, decreasing conformational fluctuations of the distal helical hairpin, without altering its ubiquitin hydrolase activity. This reduces exposure of the aggregation‐prone region that initiates Atx3 self‐assembly, ultimately delaying Atx3 amyloid fibril formation and reducing the secondary nucleation rate, a process linked to fibril proliferation and toxicity. CLR01's effects translate into the reversal of synapse loss in SCA3 cultured cortical neuron model, improve locomotor function in a Caenorhabditis elegans SCA3 model, and delay disease onset with reduced severity of motor symptoms in a SCA3 mouse model. These insights reveal a novel allosteric site for developing CLR01‐inspired therapies targeting pathological aggregation while preserving essential functional sites. They also highlight that targeting allosteric sites in amyloid‐forming proteins may provide new opportunities for safe therapeutic strategies for various protein misfolding disorders. This study uncovers a new allosteric site in the Josephin domain of ataxin‐3 targeted by the molecular tweezer CLR01, which modulates protein aggregation, improves synaptic function in neuronal cells, and delays motor dysfunction in animal models. This highlights allosteric modulation as a promising strategy for spinocerebellar ataxia type 3 and related protein‐misfolding diseases. Image created in BioRender (https://BioRender.com/oepqx3w).

Aim: Experimental models are a powerful aid in visualizing molecular phenomena. This work reports how the worm Caenorhabditis elegans (C. elegans) can be effectively explored for students to learn how molecular cues dramatically condition axonal guidance and define nervous system structure and behavior at the organism level. Summary of work: A loosely oriented observational activity preceded detailed discussions on molecules implied in axonal migration. C. elegans mutants were used to introduce second-year medical students to the deleterious effects of gene malfunctioning in neuron response to extracellular biochemical cues and to establish links between molecular function, nervous system structure, and animal behavior. Students observed C. elegans cultures and associated animal behavior alterations with the lack of function of specific axon guidance molecules (the soluble cue netrin/UNC-6 or two receptors, DCC/UNC-40 and UNC-5H). Microscopical observations of these strains, in combination with pan-neuronal GFP expression, allowed optimal visualization of severely affected neurons. Once the list of mutated genes in each strain was displayed, students could also relate abnormal patterns in axon migration/ventral and dorsal nerve cord neuron formation in C. elegans with mutated molecular components homologous to those in humans. Summary of results: Students rated the importance and effectiveness of the activity very highly. Ninety-three percent found it helpful to grasp human axonal migration, and all students were surprised with the power of the model in helping to visualize the phenomenon.

The atypical antipsychotic aripiprazole is a Food and Drug Administration-approved drug for the treatment of psychotic, mood, and other psychiatric disorders. Previous drug discovery efforts pinpointed aripiprazole as an effective suppressor of Machado-Joseph disease (MJD) pathogenesis, as its administration resulted in a reduced abundance and aggregation of mutant Ataxin-3 (ATXN3) proteins. Dopamine partial agonism and functional selectivity have been proposed as the main pharmacological mechanism of action of aripiprazole in the treatment of psychosis; however, this mechanism remains to be determined in the context of MJD. Here, we focus on confirming the efficacy of aripiprazole to reduce motor dysfunction in vivo, using a ( ) model of MJD, and on unveiling the drug targets required for its positive action against mutant ATXN3 pathogenesis. We employed pharmacogenetics and pharmacological approaches to identify which dopamine and serotonin receptors are critical for aripiprazole-mediated improvements in motor function. We demonstrated that dopamine D -like and serotonin 5-HT and 5-HT receptors play important roles in this process. Our findings strengthen the relevance of dopaminergic and serotoninergic signaling modulation against mutant ATXN3-mediated pathogenesis. The identification of aripiprazole's cellular targets, relevant for MJD and perhaps other neurodegenerative diseases, may pave the way for prospective drug discovery and development campaigns aiming to improve the features of this prototypical compound and reduce side effects not negligible in the case of aripiprazole.

The laterodorsal tegmentum (LDT) sends critical inputs to distinct reward circuit regions, including the nucleus accumbens (NAc), but their functional role in addiction-related behaviors remains underexplored. Here, we demonstrate that LDT-NAc cholinergic projections undergo cocaine-induced adaptations and modulate cocaine-related behaviors. Using cell type-specific tracing, we show that LDT neurons preferentially innervate NAc medium spiny neurons and cholinergic interneurons. Large-scale in vivo recordings reveal that cocaine pre-exposure induces persistent alterations in both LDT and NAc neuronal dynamics and modifies responses to subsequent cocaine challenge. Remarkably, pre-exposure to cocaine triggers population-specific adaptations in the LDT, selectively enhancing excitability of LDT-NAc-projecting cholinergic neurons while reducing that of non-projecting cholinergic cells. Behaviorally, optogenetic activation of LDT-NAc cholinergic projections enhances cocaine conditioning, whereas their inhibition diminishes reinforcing effects of cocaine. Our findings identify LDT-NAc cholinergic inputs as key substrates of cocaine-induced plasticity, and critical mediators of the rewarding properties of cocaine, introducing a novel component to addiction circuitry.Competing Interest StatementThe authors have declared no competing interest.Footnotes* The author list and their affiliations had to be updatedFunder Information DeclaredFundação para a Ciência e Tecnologia, 2022.02201.PTDC, 2022.01467.PTDC, PTDC/MED-NEU/4804/2020, PTDC/SAU-TOX/6802/2020, UIDB/50026/2020, UIDP/50026/2020 and LA/P/0050/2020, 2023.08896.CEECIND; CEECIND/03898/2020; CEECINST/00077/2018European Research Council, 101003187la caixa foundation, LCF/PR/HR20/52400020Bial Foundation, 175/2020National Research Agency (ANR), ANR-15-IDEX-01Centre National de la Recherche ScientifiqueFédération pour la Recherche sur le Cerveau, and Rotary - Espoir en TêteFRM, FRM EQU202403018036

Spinocerebellar ataxia type 3 (SCA3) is a rare inherited neurodegenerative disease caused by the expansion of a polyglutamine repeat in the protease ataxin-3 (Atx3). Despite extensive knowledge of the downstream pathophysiology, no disease-modifying therapies are currently available to halt disease progression. The accumulation of protein inclusions enriched in the polyQ-expanded Atx3 in neurons suggests that inhibiting its self-assembly may yield targeted therapeutic approaches. Here it is shown that a supramolecular tweezer, CLR01, binds to a lysine residue on a positively charged surface patch of the Atx3 catalytic Josephin domain. At this site, the binding of CLR01 decreases the conformational fluctuations of the distal flexible hairpin. This results in reduced exposure of the nearby aggregation-prone region, which overlaps with the substrate ubiquitin binding site and primes Atx3 self-assembly, ultimately delaying Atx3 amyloid fibril formation and reducing the secondary nucleation rate, a process linked to fibril proliferation and toxicity. These effects translate into the reversal of synapse loss in a SCA3 cultured cortical neuron model, an improved locomotor function in a C. elegans SCA3 model, and a delay in disease onset, accompanied by reduced severity of motor symptoms in a SCA3 mouse model. This study provides critical insights into Atx3 self-assembly, revealing a novel allosteric site for designing CLR01-inspired therapies targeting pathological aggregation pathways while sparing essential functional sites. These findings emphasize that targeting allosteric sites in amyloid-forming proteins may offer unique opportunities to develop safe therapeutic strategies for various protein misfolding disorders.