Biology subjects

Teixeira-Castro, A.

Publications and source records attributed to Teixeira-Castro, A..

7 recordsLinked to original sources

bioRxiv2026

PRO-FitS: a novel phenotypic assay to identify enhancers of proteostasis in C. elegans

The prevalence of neurodegenerative diseases (NDs) continues to rise with the aging of populations worldwide, representing a pressing need for the establishment of therapeutic strategies. Maintaining proteostasis is crucial for healthy aging, as the accumulation of misfolded and aggregated proteins is a key contributor to age-related cellular dysfunction and disease. This study introduces a novel phenotypic assay using Caenorhabditis elegans to screen for small molecule enhancers of proteostasis, aiming at mitigating the proteotoxic stress associated with NDs. This new methodology- PRO-FitS- uses C. elegans motor activity as a proxy for the PROteome Fitness State upon a noxious protein-denaturating stimulus, while allowing a fast and experimenter-free readout. We demonstrate the efficacy of the assay by validating the role of pharmacological mTOR inhibition and serotonergic signaling activation in reducing heat shock-induced proteotoxic damage at the whole-organism level. PRO-FitS will allow the identification of novel compounds that alleviate protein aggregation disorders, potentially revealing new pathways and cellular targets not previously implicated in proteotoxicity. Significance StatementNeurodegenerative diseases remain without effective cures, in part due to the lack of scalable methods to identify compounds that improve proteostasis. We developed PRO-FitS, a whole-organism, automated phenotypic assay in C. elegans that uses motor activity recovery as a proxy for proteome fitness after proteotoxic stress. This platform enables rapid, unbiased screening of small molecules and genetic modifiers, bridging the gap between cellular assays and complex animal models. By demonstrating the assays robustness in both wild-type and disease-relevant contexts, we establish PRO-FitS as a versatile tool for discovering therapeutic candidates and uncovering novel pathways relevant to protein aggregation disorders.

neuroscience↗

bioRxiv2026

Understanding corticosterone fluctuations and HPA-axis regulation in a mouse model of Spinocerebellar ataxia type 3

Spinocerebellar ataxia type 3 (SCA3) or Machado-Joseph Disease (MJD) is a neurodegenerative disease caused by a CAG triplet expansion in the ATXN3 gene, primarily characterized by motor impairments. However, SCA3/MJD also includes mood-related comorbidities that affect both patients and their caregivers. Current treatments focus on symptom management and supportive care, as no disease-modifying therapies are available. Previously, we have demonstrated decreased glucocorticoid receptor (GR) expression in post-mortem SCA3 human and mouse brains and elevated peripheral corticosterone (CORT) levels in SCA3 mice at late disease stages. Impaired GR signaling is typically associated with hypothalamic-pituitary-adrenal (HPA) axis dysfunction, common in stress-related psychiatric diseases. Our study aimed to dissect the HPA-axis (dys)function and the effect of stress exposure on SCA3/MJD progression. Using the CMVMJD135 mouse model, we evaluated HPA-axis regulation in SCA3/MJD by measuring CORT levels throughout disease progression (6 to 34 weeks of age) under basal conditions and after acute stress. At week 35, these mice underwent a dexamethasone injection to challenge the HPA-axis, and the CORT levels were measured at different timepoints to evaluate the axis response. Additionally, we applied a 6-week chronic unpredictable stress (CUS) protocol in another cohort of mice starting at an early symptomatic stage to assess stress effects on the progression of motor impairments. Our findings indicate that serum CORT levels in SCA3 mice begin to rise between 26 to 30 weeks of age, with no impairment in the physiological response to acute stress. SCA3 mice were also able to normalize CORT levels after dexamethasone challenge, suggesting normal HPA-axis function. While CUS exposure had a transient negative impact on the motor phenotype, this effect did not persist throughout disease progression. In conclusion, stressful events, either acute or chronic, do not seem to be major determinants of disease severity in SCA3 mice.

neuroscience↗

bioRxiv2025

iPSC derived MSC secretome activates distinct neuroprotective pathways in a preclinical model of Parkinsons disease

Parkinsons disease (PD) is characterized by a progressive loss of dopaminergic neurons, which current therapies fail to address. Mesenchymal stem cells (MSCs) secretome holds promising therapeutic potential; however, the gold standard source - bone marrow (BM) - face scalability limitations. Induced pluripotent stem cells (iPSCs)-derived MSCs (iMSCs) are a rejuvenated and clinically attractive source, yet the effects of their secretome have not been studied in PD. Here, we directly compare the effects of BM-MSCs and iMSCs secretome in a 6-OHDA rat model. Despite few differences in secretome composition, both improved motor function and partially ameliorated anhedonia, but only iMSCs secretome significantly preserved dopaminergic neurons. Proteomic analysis revealed that BM-MSCs secretome activates antioxidant and proteostasis pathways, whereas iMSCs secretome activate broader pro-survival and regenerative pathways, including NRF2-mediated oxidative stress response and mTOR. In addition, iMSC-secretome treatment modulated glutamatergic and GABAergic neurotransmission, suggesting restoration of synaptic homeostasis beyond dopaminergic preservation. These findings demonstrate that iMSCs secretome exerts robust neuroprotective effects and shed light on the mechanisms underlying this scalable and clinically translatable therapy for PD.

neuroscience↗

bioRxiv2025

The 5-HT1A receptor agonist NLX-112 rescues motor swimming deficits in Spinocerebellar Ataxia type 3 mice

IntroductionSpinocerebellar ataxia 3 (SCA3) is a rare neurodegenerative disorder which causes progressive motor disturbances. There is no approved drug treatment but selective activation of serotonin 5-HT1A receptors may be a promising therapeutic strategy to attenuate ataxia symptoms. MethodsNLX-112, a highly selective 5-HT1A full agonist, was tested in the CMVMJD135 transgenic mouse model of SCA3. NLX-112 (1.25 and 5 mg/kg/day) was administered BID intraperitoneally for 14 weeks starting when the mice were 12 weeks of age, i.e., after ataxia signs had become established. The motor swimming test (MST), where mice are required to swim to a raised platform, was used to evaluate the motor behavior of SCA3 mice and their performance was compared with that of wild-type (WT) mice. ResultsBoth doses of NLX-112 were well tolerated by the SCA3 mice, as assessed by welfare parameters. In the MST, the latency of SCA3 mice to reach the platform was significantly longer than that of WT mice. However, when SCA3 mice were treated with either 1.25 or 5 mg/kg/day of NLX-112, they showed robust improvement of motor performance, with swimming latencies which were similar to those of WT mice. This effect of NLX-112 was maintained throughout the period of the study. ConclusionsThe improved motor function of SCA3 mice when treated with NLX-112 supports its investigation as a drug candidate for the treatment of ataxia and related movement disorders. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=84 SRC="FIGDIR/small/674027v1_ufig1.gif" ALT="Figure 1"> View larger version (21K): org.highwire.dtl.DTLVardef@f0a8e1org.highwire.dtl.DTLVardef@1df4d49org.highwire.dtl.DTLVardef@14af6a2org.highwire.dtl.DTLVardef@86096b_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LISpinocerebellar ataxia type 3 (SCA3) is marked by progressive motor disturbances C_LIO_LITargeting the serotonergic system is a promising strategy to treat SCA3 C_LIO_LITransgenic SCA3 mice were treated with NLX-112, a selective 5-HT1A agonist C_LIO_LIChronic NLX-112 normalized performance of mice in the motor swimming test C_LIO_LINLX-112 could constitute a drug candidate for treatment of the ataxia disorders C_LI

neuroscience↗

bioRxiv2025

Efficacy of chronic 5-HT1A receptor agonism by NLX-112 in a mouse model of Spinocerebellar Ataxia type 3

BackgroundSpinocerebellar ataxia type 3 (SCA3) is an autosomal dominant neurodegenerative disorder caused by an elongated polyglutamine (polyQ) sequence in the ataxin-3 protein. This expansion triggers neuropathological events, leading to progressive motor disturbances. Currently, no approved therapy exists for this debilitating condition, but compelling evidence suggests that targeting the serotonergic system can significantly attenuate SCA3 disease progression in animal models. ObjectiveThis study aimed to assess the effects of NLX-112, a highly selective serotonin 1A receptor (5-HT1AR) full agonist, in the CMVMJD135 transgenic mouse model of SCA3. MethodsNLX-112 (0.625 and 5 mg/kg/day) and tandospirone (a 5-HT1AR partial agonist used as a comparator; 20 and 80 mg/kg/day) were administered chronically in drinking water for 34 weeks, starting prior to symptom onset. To evaluate the effects of the drugs on SCA3 mice, motor-related behavioral tests and neuropathological techniques were employed. ResultsTreatment with the higher dose of NLX-112 led to improvements in motor coordination and balance, and slowing of symptom deterioration as the disease progressed. These beneficial effects were not achieved with tandospirone. NLX-112 treatment also elicited neuroprotective effects, reducing dopaminergic (tyrosine hydroxylase-positive) cell loss and astrocyte reactivity in the substantia nigra. ConclusionsNLX-112 treatment, started pre-symptomatically, enhanced motor function, slowed disease progression and elicited neuroprotective effects in SCA3 mice, supporting its further development as a drug candidate for treatment of ataxia and related movement disorders. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/671624v1_ufig1.gif" ALT="Figure 1"> View larger version (69K): org.highwire.dtl.DTLVardef@548b2corg.highwire.dtl.DTLVardef@7d2f51org.highwire.dtl.DTLVardef@ad8ee4org.highwire.dtl.DTLVardef@80213c_HPS_FORMAT_FIGEXP M_FIG C_FIG Key findingsO_LINLX-112 attenuated motor deficits of SCA3 mice, when administered chronically prior to disease onset. C_LIO_LINLX-112 reduced neuropathological biomarkers in SCA3 mice, namely by restoring dopaminergic neuron loss and decreasing astrocyte reactivity. C_LIO_LINLX-112 is a potential candidate for addressing ataxia-related deficits in SCA3 patients. C_LI

neuroscience↗

bioRxiv2025

Allosteric Modulation of Pathological Ataxin-3 Aggregation: A Path to Spinocerebellar Ataxia Type-3 Therapies

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.

biophysics↗

bioRxiv2023

Astrocytic Foxo1 regulates hippocampal spinogenesis and synaptic plasticity to enhance fear memory

Astrocytes are active players in brain circuits, sensing and responding to neuronal activity, impacting behavior production. Activation of astrocytes triggers intracellular calcium elevations displaying complex spatiotemporal properties. Intracellular calcium activity is thought to underlie synaptic transmission, metabolism, and brain homeostasis modulation. However, the calcium-dependent signaling pathways involved in these processes are poorly understood, representing a critical knowledge gap in this field. To reveal calcium-dependent signaling pathways involved in circuit structure and function, we performed a multi-level analysis of the inositol 1,4,5-triphosphate receptor type 2 knockout (IP3R2 KO) mouse model which lacks somatic calcium elevations specifically in astrocytes. We focused on the hippocampus, a brain region responsible for cognitive function and emotional behaviors. The transcriptomic analysis of hippocampal tissue revealed that the lack of astrocytic somatic calcium causes the differential expression of hundreds of genes. Among these, 76 genes are regulated by the astrocyte-specific Foxo1 transcription factor. This transcription factor is over-expressed in the hippocampal astrocytes of this mouse model and regulates the expression of genes involved in spinogenesis and synaptic coverage. A detailed morphological analysis of hippocampal pyramidal neurons revealed dendrites with a shift to a more immature spine profile. This spine profile shift may underlie previously described a reduction of long-term depression and performance in fear memory tasks observed in this mouse model. Indeed, we confirmed that these mice lacking astrocytic somatic calcium display an enhancement of long-term fear memory. To verify a causal relationship between these structural, synaptic, and behavioral observations, we used a viral approach to induce the over-expression of Foxo1 in hippocampal astrocytes in naive C57BL/6J mice. This viral-driven over-expression of Foxo1 in astrocytes of the stratum radiatum replicated the shift to an immature spine profile in dendrites of pyramidal neurons crossing the territory of these astrocytes and led to a reduction of long-term depression in the same region. Finally, this manipulation was sufficient to enhance long-term fear memory. The detailed characterization of the mouse model lacking astrocytic somatic calcium revealed that astrocytes modulate hippocampal circuit structure and function through Foxo1 signaling to enhance fear memory.

neuroscience↗