Biology subjects

Gonzalez-Billault, C.

Publications and source records attributed to Gonzalez-Billault, C..

11 recordsLinked to original sources

bioRxiv2025

Bcl-xL interaction with VDAC1 reduces mitochondrial Ca2+ uptake, allowing the establishment of Therapy-Induced Senescence.

Cellular senescence, a state of irreversible growth arrest, is characterized by various phenotypic changes, including altered mitochondrial function. While the role of mitochondria in senescence is well-established, the mechanisms underlying their involvement remain unclear. Here, we investigate the early stages of therapy-induced senescence (TIS) and identify a novel anti-apoptotic mechanism mediated by Bcl-xL and VDAC1, two key regulators of mitochondrial calcium (Ca{superscript 2}) homeostasis. We find that Bcl-xL expression increases in early TIS cells and localizes to the mitochondria, where it interacts with the voltage-dependent anion channel 1 (VDAC1). This interaction dampens mitochondrial Ca{superscript 2} uptake, thereby preventing Ca{superscript 2} overload and apoptosis. Disrupting this interaction using the BH3 mimetic ABT-263 or Bcl-xL-targeting siRNA increases mitochondrial Ca{superscript 2} uptake, leading to apoptosis and blocking the formation of senescent cells. These findings uncover a previously unrecognized role of the Bcl-xL-VDAC1 axis in regulating mitochondrial Ca{superscript 2} dynamics during the onset of senescence. Our work provides mechanistic insight into how senescent cells evade apoptosis,highlighting potential therapeutic targets for selectively eliminating them in cancer and age-related diseases.

cell biology↗

bioRxiv2025

Glutamate and early functional NMDA Receptors promote axonal elongation modulating both actin cytoskeleton dynamics and H2O2 production dependent on Rac1 activity

NMDA Receptors (NMDARs) have essential functions in the nervous system, including neuronal maturation, neurotransmission, synaptic plasticity, learning, and memory. Following membrane depolarization and glutamate activation, NMDARs mediate Ca2+ influx into neurons, activating Ca2+ signaling cascades with key roles in neuronal function. However, no studies have been reported on the roles of glutamate and NMDARs during early neuronal development. Although NMDARs classically act at the postsynaptic membrane, the present results indicate that neurons express functional NMDARs during polarity acquisition and localize them in the axonal compartment early in development; at this stage, cultured neurons spontaneously release glutamate. In addition, pharmacological and genetic experiments for NMDARs loss- and gain-of-function modulated neuronal polarization and axonal elongation antagonistically. An intracellular mechanism involving Ca2+ release from the endoplasmic reticulum, activation of the Rho GTPase Rac1, and actin cytoskeleton rearrangements at the axonal growth cone couples these morphological changes. Moreover, NMDAR activity regulates the physiological intracellular production of hydrogen peroxide (H2O2) via a Rac1/NADPH oxidase complex to support neuronal development. Optogenetic Rac1 activation simultaneously promoted lamellipodia formation and H2O2 production suggesting functional coupling between these seemingly unconnected events. The mechanism presented here involves a dual function for the Rac1 protein that depends on glutamate and NMDAR activity. Based on these findings, we suggest that early physiological and spontaneous glutamate release activates NMDARs to promote early neuronal development before synapse formation, indicating that glutamate is necessary for neurotransmission, early neuronal development, and axonal growth.

cell biology↗

bioRxiv2024

Local Synthesis of Reticulon-1C Lessens the Outgrowth of Injured Axons by Controlling Spastin Activity

The regenerative potential of developing cortical axons depends on intrinsic mechanisms, such as axon-autonomous protein synthesis, that are still not fully understood. An emerging factor in this regenerative response is the bi-directional interplay between microtubule dynamics and the axonal endoplasmic reticulum (ER). We hypothesize that locally synthesized ER proteins regulate microtubule dynamics and the regeneration of cortical axons. RNA data-mining identified the ER-shaping protein Reticulon-1 as a relevant candidate across eight axonal transcriptomes. Using microfluidic chambers, we demonstrate that local knockdown of Reticulon-1 synthesis increases the outgrowth of injured cortical axons while reducing their distal tubulin levels. Furthermore, we show by live-cell imaging that axonal Reticulon-1 knockdown restores the microtubule growth rate and track length modified by injury. Interestingly, local inhibition of the microtubule- severing protein Spastin prevents the axonal knockdown-mediated effects over outgrowth and tubulin levels. We demonstrate that the Reticulon-1C isoform is locally synthesized within axons and support its isoform-specific role in attenuating Spastin-mediated microtubule severing. These findings uncover a mechanism by which axonal protein synthesis finely controls microtubule dynamics and outgrowth upon injury.

neuroscience↗

bioRxiv2024

The Neuroactive Potential of the Elderly Human Gut Microbiome is Associated with Mental Health Status

Ageing is usually associated with physiological decline, increased mental health issues, and cognitive deterioration, alongside specific changes in the gut microbiome. However, the relationship between the neuroactive potential of the gut microbiome and mental health and cognition among the elderly remains less explored. This study examines a cohort of 153 older Chilean adults with cognitive complaints, assessing anthropometric data, mental health via five distinct tests, and gut microbiome composition through 16SV4 sequencing. Our findings reveal associations between anthropometric factors and depression scores in mental tests of participants with their gut microbiome composition. Notably, depression was associated with changes in the abundance of Lachnospiraceae Eubacterium xylanophilum group and Fusobacteriaceae Fusobacterium. Additionally, bacterial pathways involved in metabolising neuroactive compounds such as tryptophan, short-chain fatty acids, p-cresol, glutamate, and nitric oxide were associated with participant age, sex, and cognitive performance. Moreover, participants sex was associated with the neuroactive potential of specific bacteria, suggesting a role of the gut microbiome in sex-related mental health differences in the elderly. Together, to the best of our knowledge, this study demonstrates for the first time the association between the neuroactive potential of the human gut microbiome and mental health status in older individuals with cognitive complaints.

animal behavior and cognition↗

bioRxiv2024

Impact of cardiometabolic factors and blood beta-amyloid on the volume of white matter hyperintensities in dementia-free subjects with cognitive complaints

IntroductionWhite matter hyperintensities (WMH) in Alzheimers disease (AD) have traditionally been associated with cerebrovascular diseases. Amyloid {beta} (A{beta}) deposition reportedly contributes to WMHs; however, this relationship remains unclear in dementia-free subjects with cognitive complaints (CC). Here, we explored the relationship between WMHs and cardiometabolic and A{beta} blood biomarkers in a community-based cohort of Latin American CC participants. MethodsWe recruited 112 individuals with CC (69 - 92 YO, 90 females) with available plasma A{beta} biomarkers and cardiometabolic markers (systolic - diastolic blood pressure and glycaemia). WMHs were quantified using a lesion segmentation tool based on SPM12 and segmented using the John Hopkins University (JHU) Atlas and ALVIN segmentation for periventricular and subcortical white matter. Linear multiple regression models were fitted to assess total WMH lesions and the segmented tract, using demographics, cardiometabolic, and A{beta} blood biomarker measures as independent variables. ResultsAfter multiple comparison corrections, diastolic blood pressure was associated with WMHs, specifically in the right anterior thalamic radiation, left cingulum, minor forceps, and subcortical ALVIN segmentation. Glycaemia was associated with WMH volume in forceps major, forceps minor, and right fronto-occipital fasciculi. Conversely, A{beta} blood biomarkers and systolic blood pressure showed no association with WMH overall or in specific tracts. ConclusionOur findings suggest that, in dementia-free CC individuals, WMH volume was more related to cardiometabolic factors, whereas A{beta} blood biomarkers might be of less relevance. Dementia prevention strategies in individuals might be a useful focus for managing high peripheral vessel resistance and endothelial damage due to hypertension and hyperglycaemia.

neuroscience↗

bioRxiv2024

Calcium (Ca2+) fluxes at Mitochondria-ER Contact Sites (MERCS) are a new target of senolysis in Therapy-Induced Senescence (TIS).

O_LIThis study investigates the state of calcium (Ca2+) flux and Mitochondria-ER contact sites (MERCS) on Therapy-Induced Senescence (TIS). C_LIO_LITIS cells-induced by Doxorubicin and Etoposide increase their MERCS contact surface but exhibit a decreased ER-mitochondria Ca2+ flux. C_LIO_LITIS cells show decreased levels of IP3R isoforms and a decreased interaction between type 1 IP3R isoform and VDAC1. C_LIO_LIThe ER-mitochondria Ca2+ flux is essential to maintain the viability of senescence cells. C_LIO_LIInhibition of ER-mitochondria Ca2+ flux rise as a new target of senolysis in vitro and in vivo. C_LI

cell biology↗

bioRxiv2023

Ketogenic diet administration later in life improves memory and regulates the synaptic cortical proteome through the cAMP/PKA signaling pathway in aging mice.

Aging is a complex biological process that compromises brain function and neuronal network activity, leading to cognitive decline and synaptic dysregulation. In recent years, a cyclic Ketogenic Diet (KD) has emerged as a potential treatment to ameliorate cognitive decline by improving memory in aged mice after long-term administration. However, the molecular mechanisms that govern such changes remains unclear. Additionally, whether short-term cyclic KD administration later in life preserves memory has not been addressed in detail. Accordingly, here we investigated how a short-term cyclic KD starting at 20-23 months-old regulates brain function of aged mice. Behavioral testing and long-term potentiation (LTP) recordings revealed that a cyclic KD improves working memory and hippocampal LTP in 24-27 months-old mice after 16 weeks of treatment. Moreover, the diet also promotes higher dendritic arborization complexity and dendritic spine density in the prefrontal cortex. Furthermore, to elucidate the molecular mechanisms underlying the memory improvements elicited by a cyclic KD, cortical synaptosomes of aged mice fed with this diet for 1 year were analyzed by mass spectrometry. Bioinformatics analysis revealed that long-term cyclic KD administration predominantly modulates the presynaptic compartment by inducing changes in the cAMP/PKA signaling pathway, the synaptic vesicle cycle, and the actin/microtubule cytoskeleton. To test these findings in vivo, synaptic proteins from cortices of 24-27-month-old mice fed with control or cyclic KD for 16 weeks were analyzed by western blot. Interestingly, increased Brain Derived Neurotrophic Factor abundance, MAP2 phosphorylation and PKA activity were observed. Overall, we show that a cyclic KD regulates brain function and memory even when it is administered at late mid-life and significantly triggers several molecular features of long-term administration, including the PKA signaling pathway and cytoskeleton dynamics, thus promoting synaptic plasticity at advanced age.

neuroscience↗

bioRxiv2022

Metabolic switch in the aging astrocyte evidenced via integrative approach comprising network and transcriptome analyses

Dysregulated central-energy metabolism is a hallmark of brain aging. Supplying enough energy for neurotransmission relies on the neuron-astrocyte metabolic network. To identify genes contributing to age-associated brain functional decline, we formulated an approach to analyze the metabolic network by integrating flux, network structure and transcriptomic databases of neurotransmission and aging. Our findings support that during brain aging: 1) The astrocyte undergoes a metabolic switch from aerobic glycolysis to oxidative phosphorylation, decreasing lactate supply to the neuron, while the neuron suffers intrinsic energetic deficit by downregulation of Krebs cycle genes, including mdh1 and mdh2 (Malate-Aspartate Shuttle); 2) Branched-chain amino acid degradation genes were downregulated, identifying dld as a central regulator; 3) Ketone body synthesis increases in the neuron, while the astrocyte increases their utilization, in line with neuronal energy deficit in favor of astrocytes. We identified candidates for preclinical studies targeting energy metabolism to prevent age-associated cognitive decline.

neuroscience↗

bioRxiv2021

Akkermansia muciniphila secretome promotes α-synuclein aggregation in enteroendocrine cells.

The notion that the gut microbiota play a role in neurodevelopment, behavior and outcome of neurodegenerative disorders is recently taking place. A number of studies have consistently reported a greater abundance of Akkermansia muciniphila in Parkinsons disease (PD) fecal samples. Nevertheless, a functional link between A.muciniphila and sporadic PD remained unexplored. Here, we investigated whether A.muciniphila secretome could initiate the misfolding process of -synuclein (Syn) in enteroendocrine cells (EECs), which are part of the gut epithelium and possess many neuron-like properties. We found that A.muciniphila secretome is directly modulated by mucin, induces intracellular calcium (Ca2+) release, and causes increased mitochondrial Ca2+ uptake in EECs, which in turn leads to production of reactive oxygen species (ROS) and Syn aggregation. However, these events were efficiently inhibited once we buffered mitochondrial Ca2+. Thereby, these molecular insights provided here offer evidence that bacterial secretome is capable of inducing Syn aggregation in enteroendocrine cells. SYNOPSIS FIGURE DESCRIPTIONThe secretome isolated from the commensal gut bacterium Akkermansia muciniphila triggers intracellular Ca2+ signaling in enteroendocrine cells, leading to increased mitochondrial Ca2+ uptake. Mitochondrial Ca2+ overload leads to ROS generation culminating with Syn phosphorylation and aggregation (left panel). All these events were inhibited once mitochondrial Ca2+ is buffered (right panel). O_LIGram-negative gut bacterium Akkermansia muciniphila is consistently found more abundant in Parkinsons disease patients. C_LIO_LIAkkermansia muciniphila protein secretome composition is directly modulated by mucin and induces an IP3-independent endoplasmic reticulum (ER)-calcium release in enteroendocrine cells. C_LIO_LIThis Ca2+ release is triggered by direct activation of Ryanodine Receptors leading to increased mitochondrial Ca2+ uptake. C_LIO_LIMitochondrial Ca2+ overload leads to ROS generation culminating with Syn aggregation. C_LIO_LIBuffering mitochondrial Ca2+ efficiently inhibits A.muciniphila-induced Syn aggregation in enteroendocrine cells. C_LI

cell biology↗

bioRxiv2020

Insulin-like growth factor 2 (IGF2) protects against Huntington's disease through the extracellular disposal of protein aggregates

Impaired neuronal proteostasis is a salient feature of many neurodegenerative diseases, highlighting alterations in the function of the endoplasmic reticulum (ER). We previously reported that targeting the transcription factor XBP1, a key mediator of the ER stress response, delays disease progression and reduces protein aggregation in various models of neurodegeneration. To identify disease-modifier genes that may explain the neuroprotective effects of XBP1 deficiency, we performed gene expression profiling of brain cortex and striatum of these animals and uncovered insulin-like growth factor 2 (Igf2) as the major upregulated gene. Here we studied the impact of IGF2 signaling on protein aggregation in models of Huntingtons disease (HD) as proof-of-concept. Cell culture studies revealed that IGF2 treatment decreases the load of intracellular aggregates of mutant huntingtin and a polyglutamine peptide. These results were validated using induced pluripotent stem cells (iPSC)-derived medium spiny neurons from HD patients. The reduction in the levels of mutant huntingtin was associated with a decrease in the half-life of the intracellular protein. The decrease in the levels of abnormal protein aggregation triggered by IGF2 were independent of the activity of autophagy and the proteasome pathways, the two main routes for mutant huntingtin clearance. Conversely, IGF2 signaling enhanced the secretion of soluble mutant huntingtin species through exosomes and microvesicles involving changes in actin dynamics. Administration of IGF2 into the brain of HD mice using gene therapy led to a significant decrease in the levels of mutant huntingtin in three different animal models. Moreover, analysis of human post-mortem brain tissue, and blood samples from HD patients showed a reduction of IGF2 level. This study identifies IGF2 as a relevant factor deregulated in HD, operating as a disease modifier that buffers the accumulation of abnormal protein aggregates. One sentence summaryIGF2 reduces the load of intracellular protein aggregates through the extracellular disposal of the mutant protein.

neuroscience↗

bioRxiv2019

Tuba activates Cdc42 during neuronal polarization downstream of the small GTPase Rab8a

The acquisition of neuronal polarity is a complex molecular process that involves several different cellular mechanisms that need to be finely coordinated to define the somatodendritic and axonal compartments. Amongst such mechanisms, cytoskeleton and membrane dynamics control both the morphological transitions that define neuronal polarity acquisition as well as provide molecular determinants to specific sites in neurons at a defined time point. Small GTPases from the Rab and Rho families are well known molecular determinants of neuronal differentiation. However, during axon specification, a molecular link that couples proteins from these two families has yet to be identified. In this paper, we describe the role of Tuba, a Cdc42-specific guanine nucleotide-exchange factor (GEF), in neuronal polarity through a Rab8a-dependent mechanism. Rab8a or Tuba gain-of-function generates neurons with supernumerary axons whereas Rab8a or Tuba loss-of-function abrogated axon specification, phenocopying the well-established effect of Cdc42 on neuronal polarity. Neuronal polarization associated to Rab8a is also evidenced in vivo, since a dominant negative version of Rab8a severely impaired neuronal migration. Remarkably, Rab8a activates Cdc42 in a Tuba-dependent manner, and dominant negative mutants of both GTPases reciprocally prevent the effect over polarity acquisition in the gain-of-function scenarios. Our results strongly suggest that a positive feedback loop linking Rab8a and Cdc42 activities via Tuba, is a primary event in neuronal polarization. In addition, we identified the GEF responsible for Cdc42 activation that is essential to specify axons in cultured neurons.

cell biology↗