Biology subjects

Umemori, J.

Publications and source records attributed to Umemori, J..

8 recordsLinked to original sources

bioRxiv2024

Cleavage of the TrkB-FL Receptor During Epileptogenesis: Insights from a Kainic Acid-Induced Model of Epilepsy and Human Samples

AO_SCPLOWBSTRACTC_SCPLOWBrain-derived neurotrophic factor (BDNF) is essential for neuronal survival, differentiation, and plasticity. In epilepsy, BDNF exhibits a dual role, exerting both antiepileptic and pro-epileptic effects. The cleavage of its main receptor, full-length tropomyosin-related kinase B (TrkB-FL), was suggested to occur in status epilepticus (SE) in vitro. Moreover, under excitotoxic conditions, TrkB-FL was found to be cleaved, resulting in the formation of a new intracellular fragment, TrkB-ICD. Thus, we hypothesized that TrkB-FL cleavage and TrkB-ICD formation could represent an uncovered mechanism in epilepsy. We used a rat model of mesial temporal lobe epilepsy (mTLE) induced by kainic acid (KA) to investigate TrkB-FL cleavage and TrkB-ICD formation during SE and established epilepsy (EE). Animals treated with 10 mg/kg of KA exhibited TrkB-FL cleavage during SE, with hippocampal levels of TrkB-FL and TrkB-ICD correlating with seizure severity. Notably, TrkB-FL cleavage and TrkB-ICD formation were also detected in animals with EE, which exhibited spontaneous recurrent convulsive seizures, neuronal death, mossy fiber sprouting, and long-term memory impairment. Importantly, hippocampal samples from patients with refractory epilepsy also showed TrkB-FL cleavage with increased TrkB-ICD levels. Additionally, overexpression of TrkB-ICD in the hippocampus of healthy rodents resulted in long-term memory impairment. Our findings suggest that TrkB-FL cleavage and the subsequent TrkB-ICD production occur throughout epileptogenesis, with the extent of cleavage correlating positively with seizure occurrence. Moreover, we found that TrkB-ICD impairs memory. This work uncovers a novel mechanism in epileptogenesis that could serve as a potential therapeutic target in mTLE, with implications for preserving cognitive function.

neuroscience↗

bioRxiv2024

Chronic treatment with fluoxetine downregulates mitochondrial activity in parvalbumin interneurons of prefrontal cortex

Chronic treatment with fluoxetine, a widely prescribed selective serotonin reuptake inhibitor (SSRI), is known to promote neural plasticity. The role of fluoxetine in plasticity has been particularly tied to parvalbumin-positive interneurons (PV-INs), which are critical regulators of inhibitory tone and synaptic plasticity. Our previous studies have highlighted behavioral plasticity and gene expression changes in the visual cortex and hippocampus after chronic treatment with fluoxetine. However, the impact of fluoxetine treatment on gene expression and neuronal function in the prefrontal cortex (PFC) remains unclear. This study aimed to investigate the effects of chronic fluoxetine treatment on PV-INs in the PFC. Using Translating Ribosome Affinity Purification (TRAP), we found that fluoxetine treatment downregulated pathways involved in mitochondrial energy production, including multiple steps of the respiratory chain. Upregulated genes were associated with phosphatase activity, voltage-gated potassium channels, and amino acid transmembrane transport. Mitochondrial analysis for sorted cells demonstrated mitochondrial membrane potential was reduced in PV-INs, but increased in non-PV-INs in the PFC. These observations indicate altered mitochondrial dynamics between the cell types and reduced mitochondrial activity in PV-INs, potentially contributing to their disinhibition. Immunohistochemical analyses further demonstrated reduced PV expression and weakened perineuronal nets in specific PFC regions, suggesting elevated plasticity, and potentially explaining the modulation of fear and anxiety-related behaviors that were previously observed. Our results underscore the differential impact of chronic fluoxetine on gene expression and mitochondrial function in PV-INs, suggesting region-specific disinhibition and enhanced synaptic plasticity in the PFC.

neuroscience↗

bioRxiv2024

The BDNF/TrkB pathway in Somatostatin-expressing neurons suppresses cocaine-seeking behaviour

Cocaine addiction is a highly debilitating condition consisting of compulsive self-administration and seek for the substance of abuse, and its most challenging feature is the high rate of relapse. Addiction and relapse share similarities with neural plasticity which acts through the Brain-Derived Neurotrophic Factor and its receptor TrkB. Somatostatin (SST) expressing interneurons are involved in neuronal plasticity and are important in modulating cocaine-seeking behaviour in mice. We tested the role of TrkB in Somatostatin (SST)-expressing neurons in the extinction of cocaine-seeking behaviour, using mice in which TrkB has been knocked out specifically in SST neurons. We have observed that in these mice, once a cocaine-conditioned place preference is acquired, its extinction through seven days of extinction training is impaired, showing how this process relies on neural plasticity in SST neurons. When we promoted plasticity during extinction training using a light-activable TrkB in SST neurons in the prefrontal cortex of cocaine-conditioned mice, relapse of cocaine-seeking was prevented. Our data identify the critical role of TrkB-mediated plasticity within SST neurons in the extinction of and relapse to cocaine addiction.

neuroscience↗

bioRxiv2023

Somatostatin-expressing neurons in the ventral tegmental area innervate specific forebrain regions and are involved in the stress response

Expanding knowledge about the cellular composition of subcortical brain regions demonstrates large heterogeneity and differences from the cortical architecture. Recently, we described three subtypes of somatostatin-expressing (Sst) neurons in the mouse ventral tegmental area (VTA) and showed their local inhibitory action on the neighbouring dopaminergic neurons (Nagaeva et al., 2020). Here, we report that VTA Sst neurons especially from the anterolateral part also project far outside the VTA and innervate several forebrain regions that are mainly involved in the regulation of emotional behaviour. Deletion of these VTA Sst neurons affected several behaviours and drug responses, such as home cage activity, sensitization of locomotor activity to morphine, fear conditioning responses, and reactions to inescapable stress of forced swimming, often in a sex-dependent manner. Together, these data demonstrate that VTA Sst neurons have selective projection targets, which are distinct from the main targets of VTA dopamine neurons and involved in the regulation of a variety of behaviours mostly associated with the stress response. This, makes Sst neurons a meaningful addition to the remote VTA circuit and stress-related neuronal network.

neuroscience↗

bioRxiv2022

Activation of TrkB in Parvalbumin interneurons is required for the promotion of reversal learning in spatial and fear memory by antidepressants

Critical period-like plasticity (iPlasticity) can be reinstated in the adult brain by several interventions, including drugs and optogenetic modifications. We have demonstrated that a combination of iPlasticity with optimal training improves behaviors related to neuropsychiatric disorders. In this context, the activation of TrkB, a receptor for BDNF, in Parvalbumin positive (PV+) interneurons has a pivotal role in cortical network changes. However, it is unknown if the activation of TrkB in PV+ interneurons is important for other plasticity-related behaviors, especially for learning and memory. Here, using mice with heterozygous conditional TrkB deletion in PV+ interneurons (PV-TrkB hCKO) in Intellicage and fear erasure paradigms, we show that chronic treatment with fluoxetine, a widely prescribed antidepressant drug that is known to promote the activation of TrkB, enhances behavioral flexibility in spatial and fear memory, largely depending on the expression of the TrkB receptor in PV+ interneurons. In addition, hippocampal long-term potentiation (LTP) was enhanced by chronic treatment with fluoxetine in wild-type mice, but not in PV-TrkB hCKO mice. Transcriptomic analysis of PV+ interneurons after fluoxetine treatment indicated intrinsic changes in synaptic formation and downregulation of enzymes involved in perineuronal net (PNN) formation. Consistently, immunohistochemistry has shown that the fluoxetine treatment alters PV expression and reduces PNNs in PV+ interneurons, and here we show that TrkB expression in PV+ interneurons is required for these effects. Together, our results provide molecular and network mechanisms for the induction of critical period-like plasticity in adulthood.

neuroscience↗

bioRxiv2021

Optical activation of TrkB neurotrophin receptor in mouse ventral hippocampus promotes plasticity and facilitates fear extinction

Successful extinction of traumatic memories depends on neuronal plasticity in the fear extinction network. However, the mechanisms involved in the extinction process remain poorly understood. Here, we investigated the fear extinction network by using a new optogenetic technique that allows temporal and spatial control of neuronal plasticity in vivo. We optimized an optically inducible TrkB (CKII-optoTrkB), the receptor of the brain-derived neurotrophic factor, which can be activated upon blue light exposure to increase plasticity specifically in pyramidal neurons. The activation of CKII-optoTrkB facilitated the induction of LTP in Schaffer collateral-CA1 synapses after brief theta-burst stimulation and increased the expression of FosB in the pyramidal neurons of the ventral hippocampus, indicating enhanced plasticity in that brain area. We showed that optical stimulation of the CA1 region of the ventral hippocampus during fear extinction training led to an attenuated conditioned fear memory. This was a specific effect only observed when combining extinction training with CKII-optoTrkB activation, and not when using either intervention alone. Thus, TrkB activation in ventral CA1 pyramidal neurons promotes a state of neuronal plasticity that allows extinction training to guide neuronal network remodeling to overcome fear memories. Our methodology is a powerful tool to induce neuronal network remodeling in the adult brain, and can attenuate neuropsychiatric symptoms caused by malfunctioning networks.

neuroscience↗

bioRxiv2020

Chondroitinase and antidepressants promote plasticity by releasing TRKB from dephosphorylating control of PTPσ in parvalbumin neurons

Perineuronal nets (PNNs) are an extracellular matrix structure rich in chondroitin sulphate proteoglycans (CSPGs) which preferentially encase parvalbumin-containing (PV+) interneurons. PNNs restrict cortical network plasticity but the molecular mechanisms involved are unclear. We found that reactivation of ocular dominance plasticity in the adult visual cortex induced by chondroitinase (chABC)-mediated PNN removal requires intact signaling by the neurotrophin receptor TRKB in PV+ neurons. Additionally, we demonstrate that chABC increases TRKB phosphorylation (pTRKB), while PNN component aggrecan attenuates BDNF-induced pTRKB in cortical neurons in culture. We further found that protein tyrosine phosphatase sigma (PTP{sigma}, PTPRS), receptor for CSPGs, interacts with TRKB and restricts TRKB phosphorylation. PTP{sigma} deletion increases phosphorylation of TRKB in vitro and in vivo in male and female mice, and juvenile-like plasticity is retained in the visual cortex of adult PTP{sigma} deficient mice (PTP{sigma}+/-). The antidepressant drug fluoxetine, which is known to promote TRKB phosphorylation and reopen critical period-like plasticity in the adult brain, disrupts the interaction between TRKB and PTP{sigma} by binding to the transmembrane domain of TRKB. We propose that both chABC and fluoxetine reopen critical period-like plasticity in the adult visual cortex by promoting TRKB signaling in PV+ neurons through inhibition of TRKB dephosphorylation by the PTP{sigma}-CSPG complex. Significance statementCritical period-like plasticity can be reactivated in the adult visual cortex through disruption of perineuronal nets (PNNs) by chondroitinase treatment, or by chronic antidepressant treatment. We now show that the effects of both chondroitinase and fluoxetine are mediated by the neurotrophin receptor TRKB in parvalbumin-containing (PV+) interneurons. We found that chondroitinase-induced visual cortical plasticity is dependent on TRKB in PV+ neurons. Protein tyrosine phosphatase type S (PTP{sigma}, PTPRS), a receptor for PNNs, interacts with TRKB and inhibits its phosphorylation, and chondroitinase treatment or deletion of PTP{sigma} increases TRKB phosphorylation. Antidepressant fluoxetine disrupts the interaction between TRKB and PTP{sigma}, thereby increasing TRKB phosphorylation. Thus, juvenile-like plasticity induced by both chondroitinase and antidepressant treatment is mediated by TRKB activation in PV+ interneurons.

neuroscience↗

bioRxiv2020

TrkB activation in Parvalbumin interneurons orchestrates cortical plasticity

Activation state of Parvalbumin (PV) interneurons regulates neuronal plasticity, driving the closure of developmental critical periods and alternating between high and low plasticity states in response to experience in adulthood. We now show that PV plasticity states are regulated through the activation of TrkB neurotrophin receptors. Activation of an optically activatable TrkB (optoTrkB) specifically in PV interneurons switches adult cortical networks into a state of elevated plasticity within minutes by decreasing excitability of PV neurons. OptoTrkB activation induces changes in gene expression related to neuronal plasticity and excitability, and increases the phosphorylation of Kv3.1 channels. OptoTrkB activation shifted cortical networks towards a low PV configuration, promoting oscillatory synchrony and ocular dominance plasticity. Visual plasticity induced by fluoxetine was lost in mice lacking TrkB in PV neurons. Our data suggest a novel mechanism that dynamically regulates PV interneurons configuration state and orchestrates cortical networks during adulthood. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=171 SRC="FIGDIR/small/063503v2_ufig1.gif" ALT="Figure 1"> View larger version (54K): org.highwire.dtl.DTLVardef@4c521corg.highwire.dtl.DTLVardef@a2ec04org.highwire.dtl.DTLVardef@353775org.highwire.dtl.DTLVardef@1cc0448_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗