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1.
Nat Commun ; 11(1): 5083, 2020 10 08.
Artigo em Inglês | MEDLINE | ID: mdl-33033259

RESUMO

In hippocampal pyramidal cells, a small subset of dendritic spines contain endoplasmic reticulum (ER). In large spines, ER frequently forms a spine apparatus, while smaller spines contain just a single tubule of smooth ER. Here we show that the ER visits dendritic spines in a non-random manner, targeting spines during periods of high synaptic activity. When we blocked ER motility using a dominant negative approach against myosin V, spine synapses became stronger compared to controls. We were not able to further potentiate these maxed-out synapses, but long-term depression (LTD) was readily induced by low-frequency stimulation. We conclude that the brief ER visits to active spines have the important function of preventing runaway potentiation of individual spine synapses, keeping most of them at an intermediate strength level from which both long-term potentiation (LTP) and LTD are possible.


Assuntos
Espinhas Dendríticas/metabolismo , Retículo Endoplasmático/metabolismo , Sinapses/metabolismo , Animais , Hipocampo/metabolismo , Potenciação de Longa Duração , Miosina Tipo V/metabolismo , Ratos Wistar , Imagem com Lapso de Tempo
2.
Nat Commun ; 11(1): 5076, 2020 10 08.
Artigo em Inglês | MEDLINE | ID: mdl-33033264

RESUMO

Proper threat-reward decision-making is critical to animal survival. Emerging evidence indicates that the motor system may participate in decision-making but the neural circuit and molecular bases for these functions are little known. We found in C. elegans that GABAergic motor neurons (D-MNs) bias toward the reward behavior in threat-reward decision-making by retrogradely inhibiting a pair of premotor command interneurons, AVA, that control cholinergic motor neurons in the avoidance neural circuit. This function of D-MNs is mediated by a specific ionotropic GABA receptor (UNC-49) in AVA, and depends on electrical coupling between the two AVA interneurons. Our results suggest that AVA are hub neurons where sensory inputs from threat and reward sensory modalities and motor information from D-MNs are integrated. This study demonstrates at single-neuron resolution how motor neurons may help shape threat-reward choice behaviors through interacting with other neurons.


Assuntos
Caenorhabditis elegans/fisiologia , Neurônios GABAérgicos/metabolismo , Locomoção/fisiologia , Neurônios Motores/metabolismo , Animais , Aprendizagem da Esquiva , Viés , Proteínas de Caenorhabditis elegans/metabolismo , Quimiotaxia , Fenômenos Eletrofisiológicos , Junções Comunicantes/metabolismo , Glicerol/farmacologia , Interneurônios/metabolismo , Optogenética , Concentração Osmolar , Receptores Colinérgicos/metabolismo , Sinapses/metabolismo
3.
Nat Commun ; 11(1): 5074, 2020 10 08.
Artigo em Inglês | MEDLINE | ID: mdl-33033265

RESUMO

Touch and itch sensations are crucial for evoking defensive and emotional responses, and light tactile touch may induce unpleasant itch sensations (mechanical itch or alloknesis). The neural substrate for touch-to-itch conversion in the spinal cord remains elusive. We report that spinal interneurons expressing Tachykinin 2-Cre (Tac2Cre) receive direct Aß low threshold mechanoreceptor (LTMR) input and form monosynaptic connections with GRPR neurons. Ablation or inhibition markedly reduces mechanical but not acute chemical itch nor noxious touch information. Chemogenetic inhibition of Tac2Cre neurons also displays pronounced deficit in chronic dry skin itch, a type of chemical itch in mice. Consistently, ablation of gastrin-releasing peptide receptor (GRPR) neurons, which are essential for transmitting chemical itch, also abolishes mechanical itch. Together, these results suggest that innocuous touch and chemical itch information converge on GRPR neurons and thus map an exquisite spinal circuitry hard-wired for converting innocuous touch to irritating itch.


Assuntos
Rede Nervosa/fisiopatologia , Prurido/fisiopatologia , Tato/fisiologia , Animais , Comportamento Animal , Injeções Espinhais , Luz , Potenciais da Membrana , Camundongos Endogâmicos C57BL , Neurônios/metabolismo , Precursores de Proteínas/metabolismo , Proteínas Proto-Oncogênicas c-fos/metabolismo , Receptores da Bombesina/metabolismo , Pele/patologia , Medula Espinal/fisiopatologia , Sinapses/metabolismo , Taquicininas/metabolismo
4.
PLoS Biol ; 18(8): e3000820, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32866173

RESUMO

Mutations in the gene encoding the microtubule-severing protein spastin (spastic paraplegia 4 [SPG4]) cause hereditary spastic paraplegia (HSP), associated with neurodegeneration, spasticity, and motor impairment. Complicated forms (complicated HSP [cHSP]) further include cognitive deficits and dementia; however, the etiology and dysfunctional mechanisms of cHSP have remained unknown. Here, we report specific working and associative memory deficits upon spastin depletion in mice. Loss of spastin-mediated severing leads to reduced synapse numbers, accompanied by lower miniature excitatory postsynaptic current (mEPSC) frequencies. At the subcellular level, mutant neurons are characterized by longer microtubules with increased tubulin polyglutamylation levels. Notably, these conditions reduce kinesin-microtubule binding, impair the processivity of kinesin family protein (KIF) 5, and reduce the delivery of presynaptic vesicles and postsynaptic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. Rescue experiments confirm the specificity of these results by showing that wild-type spastin, but not the severing-deficient and disease-associated K388R mutant, normalizes the effects at the synaptic, microtubule, and transport levels. In addition, short hairpin RNA (shRNA)-mediated reduction of tubulin polyglutamylation on spastin knockout background normalizes KIF5 transport deficits and attenuates the loss of excitatory synapses. Our data provide a mechanism that connects spastin dysfunction with the regulation of kinesin-mediated cargo transport, synapse integrity, and cognition.


Assuntos
Ácido Glutâmico/metabolismo , Cinesina/metabolismo , Transtornos da Memória/metabolismo , Transtornos da Memória/fisiopatologia , Memória de Curto Prazo , Neurônios/metabolismo , Espastina/deficiência , Tubulina (Proteína)/metabolismo , Potenciais de Ação , Animais , Membrana Celular/metabolismo , Espinhas Dendríticas/metabolismo , Espinhas Dendríticas/ultraestrutura , Potenciais Pós-Sinápticos Excitadores , Hipocampo/patologia , Hipocampo/fisiopatologia , Camundongos Knockout , Microtúbulos/metabolismo , Microtúbulos/ultraestrutura , Atividade Motora , Neurônios/patologia , Neurônios/ultraestrutura , Transporte Proteico , Espastina/metabolismo , Sinapses/metabolismo , Sinapses/ultraestrutura , Vesículas Sinápticas/metabolismo
5.
Nat Commun ; 11(1): 4395, 2020 09 02.
Artigo em Inglês | MEDLINE | ID: mdl-32879322

RESUMO

The formation and maintenance of spatial representations within hippocampal cell assemblies is strongly dictated by patterns of inhibition from diverse interneuron populations. Although it is known that inhibitory synaptic strength is malleable, induction of long-term plasticity at distinct inhibitory synapses and its regulation of hippocampal network activity is not well understood. Here, we show that inhibitory synapses from parvalbumin and somatostatin expressing interneurons undergo long-term depression and potentiation respectively (PV-iLTD and SST-iLTP) during physiological activity patterns. Both forms of plasticity rely on T-type calcium channel activation to confer synapse specificity but otherwise employ distinct mechanisms. Since parvalbumin and somatostatin interneurons preferentially target perisomatic and distal dendritic regions respectively of CA1 pyramidal cells, PV-iLTD and SST-iLTP coordinate a reprioritisation of excitatory inputs from entorhinal cortex and CA3. Furthermore, circuit-level modelling reveals that PV-iLTD and SST-iLTP cooperate to stabilise place cells while facilitating representation of multiple unique environments within the hippocampal network.


Assuntos
Hipocampo/fisiologia , Interneurônios/metabolismo , Células Piramidais/fisiologia , Potenciais de Ação , Animais , Região CA1 Hipocampal/citologia , Região CA1 Hipocampal/fisiologia , Canais de Cálcio Tipo T/metabolismo , Channelrhodopsins/metabolismo , Hipocampo/citologia , Camundongos , Optogenética/métodos , Parvalbuminas/metabolismo , Técnicas de Patch-Clamp , Transdução de Sinais , Somatostatina/metabolismo , Sinapses/metabolismo
6.
Neuron ; 107(4): 593-594, 2020 08 19.
Artigo em Inglês | MEDLINE | ID: mdl-32818471

RESUMO

How synapses assemble remains unknown. In this issue of Neuron, Held et al. (2020) demonstrate that Cav2-type voltage-gated calcium channels do not mediate presynaptic assembly. Moreover, the channel-associated protein α2δ localizes independently, suggesting additional functions for this auxiliary protein.


Assuntos
Canais de Cálcio Tipo N , Cálcio , Cálcio/metabolismo , Canais de Cálcio Tipo N/genética , Neurônios/metabolismo , Sinapses/metabolismo
7.
PLoS Comput Biol ; 16(7): e1008099, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32706788

RESUMO

Next-generation sequencing (NGS) technology has become a powerful tool for dissecting the molecular and pathological signatures of a variety of human diseases. However, the limited availability of biological samples from different disease stages is a major hurdle in studying disease progressions and identifying early pathological changes. Deep learning techniques have recently begun to be applied to analyze NGS data and thereby predict the progression of biological processes. In this study, we applied a deep learning technique called generative adversarial networks (GANs) to predict the molecular progress of Alzheimer's disease (AD). We successfully applied GANs to analyze RNA-seq data from a 5xFAD mouse model of AD, which recapitulates major AD features of massive amyloid-ß (Aß) accumulation in the brain. We examined how the generator is featured to have specific-sample generation and biological gene association. Based on the above observations, we suggested virtual disease progress by latent space interpolation to yield the transition curves of various genes with pathological changes from normal to AD state. By performing pathway analysis based on the transition curve patterns, we identified several pathological processes with progressive changes, such as inflammatory systems and synapse functions, which have previously been demonstrated to be involved in the pathogenesis of AD. Interestingly, our analysis indicates that alteration of cholesterol biosynthesis begins at a very early stage of AD, suggesting that it is the first effect to mediate the cholesterol metabolism of AD downstream of Aß accumulation. Here, we suggest that GANs are a useful tool to study disease progression, leading to the identification of early pathological signatures.


Assuntos
Doença de Alzheimer/fisiopatologia , RNA-Seq , Algoritmos , Doença de Alzheimer/genética , Precursor de Proteína beta-Amiloide/genética , Animais , Encéfalo/metabolismo , Córtex Cerebral/metabolismo , Colesterol/metabolismo , Análise por Conglomerados , Aprendizado Profundo , Modelos Animais de Doenças , Progressão da Doença , Humanos , Inflamação , Camundongos , Modelos Genéticos , RNA Mensageiro/metabolismo , Sinapses/metabolismo , Lobo Temporal/metabolismo , Sequenciamento Completo do Exoma
8.
PLoS Pathog ; 16(7): e1008654, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32673372

RESUMO

Prion protein (PrP) mutations are linked to genetic prion diseases, a class of phenotypically heterogeneous neurodegenerative disorders with invariably fatal outcome. How mutant PrP triggers neurodegeneration is not known. Synaptic dysfunction precedes neuronal loss but it is not clear whether, and through which mechanisms, disruption of synaptic activity ultimately leads to neuronal death. Here we show that mutant PrP impairs the secretory trafficking of AMPA receptors (AMPARs). Specifically, intracellular retention of the GluA2 subunit results in synaptic exposure of GluA2-lacking, calcium-permeable AMPARs, leading to increased calcium permeability and enhanced sensitivity to excitotoxic cell death. Mutant PrPs linked to different genetic prion diseases affect AMPAR trafficking and function in different ways. Our findings identify AMPARs as pathogenic targets in genetic prion diseases, and support the involvement of excitotoxicity in neurodegeneration. They also suggest a mechanistic explanation for how different mutant PrPs may cause distinct disease phenotypes.


Assuntos
Cálcio/metabolismo , Neurônios/metabolismo , Proteínas PrPSc/metabolismo , Receptores de AMPA/metabolismo , Sinapses/metabolismo , Animais , Morte Celular/fisiologia , Camundongos , Permeabilidade , Transporte Proteico/fisiologia
9.
Nat Commun ; 11(1): 3594, 2020 07 17.
Artigo em Inglês | MEDLINE | ID: mdl-32681011

RESUMO

Circular RNAs (circRNAs) are abundant in mammalian brain and some show age-dependent expression patterns. Here, we report that circGRIA1, a conserved circRNA isoform derived from the genomic loci of α-mino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor subunit Gria1, shows an age-related and male-specific increase in expression in the rhesus macaque prefrontal cortex and hippocampus. We show circGRIA1 is predominantly localized to the nucleus, and find an age-related increase in its association with the promoter region of Gria1 gene, suggesting it has a regulatory role in Gria1 transcription. In vitro and in vivo manipulation of circGRIA1 negatively regulates Gria1 mRNA and protein levels. Knockdown of circGRIA1 results in an age-related improvement of synaptogenesis, and GluR1 activity-dependent synaptic plasticity in the hippocampal neurons in males. Our findings underscore the importance of circRNA regulation and offer an insight into the biology of brain aging.


Assuntos
Encéfalo/fisiologia , Macaca mulatta/metabolismo , Plasticidade Neuronal , RNA Circular/metabolismo , Receptores de AMPA/genética , Sinapses/metabolismo , Fatores Etários , Envelhecimento , Animais , Feminino , Hipocampo/metabolismo , Macaca mulatta/genética , Macaca mulatta/crescimento & desenvolvimento , Masculino , RNA Circular/genética , Receptores de AMPA/metabolismo , Sinapses/genética
10.
PLoS One ; 15(7): e0236478, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32716967

RESUMO

CaMKII is an important mediator of forms of synaptic plasticity that are thought to underly learning and memory. The CaMKII mutants K42M and K42R have been used interchangeably as research tools, although some reported phenotypic differences suggest that they may differ in the extent to which they impair ATP binding. Here, we directly compared the two mutations at the high ATP concentrations that exist within cells (~4 mM). We found that both mutations equally blocked GluA1 phosphorylation in vitro and GluN2B binding within cells. Both mutations also reduced but did not completely abolish CaMKII T286 autophosphorylation in vitro or CaMKII movement to excitatory synapses in neurons. Thus, despite previously suggested differences, both mutations appear to interfere with ATP binding to the same extent.


Assuntos
Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/genética , Mutação/genética , Animais , Cálcio/metabolismo , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/química , Células Cultivadas , Feminino , Ácido Glutâmico/farmacologia , Células HEK293 , Hipocampo/citologia , Humanos , Masculino , Movimento , Fosforilação , Ratos Sprague-Dawley , Receptores de N-Metil-D-Aspartato/metabolismo , Sinapses/metabolismo
11.
Nature ; 583(7818): 813-818, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32699410

RESUMO

Most sensory information destined for the neocortex is relayed through the thalamus, where considerable transformation occurs1,2. One means of transformation involves interactions between excitatory thalamocortical neurons that carry data to the cortex and inhibitory neurons of the thalamic reticular nucleus (TRN) that regulate the flow of those data3-6. Although the importance of the TRN has long been recognised7-9, understanding of its cell types, their organization and their functional properties has lagged behind that of the thalamocortical systems they control. Here we address this by investigating the somatosensory and visual circuits of the TRN in mice. In the somatosensory TRN we observed two groups of genetically defined neurons that are topographically segregated and physiologically distinct, and that connect reciprocally with independent thalamocortical nuclei through dynamically divergent synapses. Calbindin-expressing cells-located in the central core-connect with the ventral posterior nucleus, the primary somatosensory thalamocortical relay. By contrast, somatostatin-expressing cells-which reside along the surrounding edges of the TRN-synapse with the posterior medial thalamic nucleus, a higher-order structure that carries both top-down and bottom-up information10-12. The two TRN cell groups process their inputs in pathway-specific ways. Synapses from the ventral posterior nucleus to central TRN cells transmit rapid excitatory currents that depress deeply during repetitive activity, driving phasic spike output. Synapses from the posterior medial thalamic nucleus to edge TRN cells evoke slower, less depressing excitatory currents that drive more persistent spiking. Differences in the intrinsic physiology of TRN cell types, including state-dependent bursting, contribute to these output dynamics. The processing specializations of these two somatosensory TRN subcircuits therefore appear to be tuned to the signals they carry-a primary central subcircuit tuned to discrete sensory events, and a higher-order edge subcircuit tuned to temporally distributed signals integrated from multiple sources. The structure and function of visual TRN subcircuits closely resemble those of the somatosensory TRN. These results provide insights into how subnetworks of TRN neurons may differentially process distinct classes of thalamic information.


Assuntos
Vias Neurais , Núcleos Talâmicos/citologia , Núcleos Talâmicos/fisiologia , Potenciais de Ação , Animais , Calbindinas/metabolismo , Potenciais Somatossensoriais Evocados , Potenciais Evocados Visuais , Feminino , Cinética , Masculino , Camundongos , Inibição Neural , Neurônios/metabolismo , Somatostatina/metabolismo , Sinapses/metabolismo
12.
Nat Commun ; 11(1): 3208, 2020 06 25.
Artigo em Inglês | MEDLINE | ID: mdl-32587250

RESUMO

Inner hair cells (IHCs) are the primary receptors for hearing. They are housed in the cochlea and convey sound information to the brain via synapses with the auditory nerve. IHCs have been thought to be electrically and metabolically independent from each other. We report that, upon developmental maturation, in mice 30% of the IHCs are electrochemically coupled in 'mini-syncytia'. This coupling permits transfer of fluorescently-labeled metabolites and macromolecular tracers. The membrane capacitance, Ca2+-current, and resting current increase with the number of dye-coupled IHCs. Dual voltage-clamp experiments substantiate low resistance electrical coupling. Pharmacology and tracer permeability rule out coupling by gap junctions and purinoceptors. 3D electron microscopy indicates instead that IHCs are coupled by membrane fusion sites. Consequently, depolarization of one IHC triggers presynaptic Ca2+-influx at active zones in the entire mini-syncytium. Based on our findings and modeling, we propose that IHC-mini-syncytia enhance sensitivity and reliability of cochlear sound encoding.


Assuntos
Cóclea , Células Ciliadas Auditivas Internas , Audição/fisiologia , Animais , Sinalização do Cálcio , Cóclea/citologia , Cóclea/inervação , Nervo Coclear/metabolismo , Tomografia com Microscopia Eletrônica , Células Gigantes , Células Ciliadas Auditivas Internas/citologia , Células Ciliadas Auditivas Internas/fisiologia , Camundongos , Técnicas de Patch-Clamp , Roedores/fisiologia , Sinapses/metabolismo
13.
Neuron ; 107(3): 417-435, 2020 08 05.
Artigo em Inglês | MEDLINE | ID: mdl-32579881

RESUMO

Identifying effective treatments for Alzheimer's disease (AD) has proven challenging and has instigated a shift in AD research focus toward the earliest disease-initiating cellular mechanisms. A key insight has been an increase in soluble Aß oligomers in early AD that is causally linked to neuronal and circuit hyperexcitability. However, other accumulating AD-related peptides and proteins, including those derived from the same amyloid precursor protein, such as Aη or sAPPα, and autonomously, such as tau, exhibit surprising opposing effects on circuit dynamics. We propose that the effects of these on neuronal circuits have profound implications for our understanding of disease complexity and heterogeneity and for the development of personalized diagnostic and therapeutic strategies in AD. Here, we highlight important peptide-specific mechanisms of dynamic pathological disequilibrium of cellular and circuit activity in AD and discuss approaches in which these may be further understood, and theoretically and experimentally leveraged, to elucidate AD pathophysiology.


Assuntos
Doença de Alzheimer/metabolismo , Precursor de Proteína beta-Amiloide/metabolismo , Encéfalo/metabolismo , Neurônios/metabolismo , Convulsões/metabolismo , Proteínas tau/metabolismo , Doença de Alzheimer/fisiopatologia , Secretases da Proteína Precursora do Amiloide/metabolismo , Peptídeos beta-Amiloides/metabolismo , Animais , Astrócitos/metabolismo , Segmento Inicial do Axônio/metabolismo , Encéfalo/fisiopatologia , Humanos , Microglia/metabolismo , Canal de Sódio Disparado por Voltagem NAV1.1/metabolismo , Vias Neurais , Fragmentos de Peptídeos/metabolismo , Receptores de Glutamato/metabolismo , Convulsões/fisiopatologia , Sinapses/metabolismo
14.
J Vis Exp ; (159)2020 05 12.
Artigo em Inglês | MEDLINE | ID: mdl-32478717

RESUMO

Microtubules (MTs) play critical roles in neuronal development, but many questions remain about the molecular mechanisms of their regulation and function. Furthermore, despite progress in understanding postsynaptic MTs, much less is known about the contributions of presynaptic MTs to neuronal morphogenesis. In particular, studies of in vivo MT dynamics in Drosophila sensory dendrites yielded significant insights into polymer-level behavior. However, the technical and analytical challenges associated with live imaging of the fly neuromuscular junction (NMJ) have limited comparable studies of presynaptic MT dynamics. Moreover, while there are many highly effective software strategies for automated analysis of MT dynamics in vitro and ex vivo, in vivo data often necessitate significant operator input or entirely manual analysis due to inherently inferior signal-to-noise ratio in images and complex cellular morphology.  To address this, this study optimized a new software platform for automated and unbiased in vivo particle detection. Multiparametric analysis of live time-lapse confocal images of EB1-GFP labeled MTs was performed in both dendrites and the NMJ of Drosophila larvae and found striking differences in MT behaviors. MT dynamics were furthermore analyzed following knockdown of the MT-associated protein (MAP) dTACC, a key regulator of Drosophila synapse development, and identified statistically significant changes in MT dynamics compared to wild type. These results demonstrate that this novel strategy for the automated multiparametric analysis of both pre- and postsynaptic MT dynamics at the polymer-level significantly reduces human-in-the-loop criteria. The study furthermore shows the utility of this method in detecting distinct MT behaviors upon dTACC-knockdown, indicating a possible future application for functional screens of factors that regulate MT dynamics in vivo. Future applications of this method may also focus on elucidating cell type and/or compartment-specific MT behaviors, and multicolor correlative imaging of EB1-GFP with other cellular and subcellular markers of interest.


Assuntos
Dendritos/metabolismo , Drosophila melanogaster/metabolismo , Imageamento Tridimensional , Microtúbulos/metabolismo , Junção Neuromuscular/metabolismo , Imagem Individual de Molécula , Sinapses/metabolismo , Animais , Proteínas de Drosophila/metabolismo , Proteínas de Fluorescência Verde/metabolismo , Humanos , Processamento de Imagem Assistida por Computador , Larva/metabolismo , Proteínas Associadas aos Microtúbulos/metabolismo , Interferência de RNA , Software
15.
J Vis Exp ; (159)2020 05 13.
Artigo em Inglês | MEDLINE | ID: mdl-32478750

RESUMO

Drosophila serves as a useful model for assessing synaptic structure and function associated with neurodegenerative diseases. While much work has focused on neuromuscular junctions (NMJs) in Drosophila larvae, assessing synaptic integrity in adult Drosophila has received much less attention. Here we provide a straightforward method for dissection of the dorsal longitudinal muscles (DLMs), which are required for flight ability. In addition to flight as a behavioral readout, this dissection allows for the both DLM synapses and muscle tissue to be amenable to structural analysis using fluorescently labeled antibodies for synaptic markers or proteins of interest. This protocol allows for the evaluation of the structural integrity of synapses in adult Drosophila during aging to model the progressive, age-dependent nature of most neurodegenerative diseases.


Assuntos
Envelhecimento/patologia , Drosophila melanogaster/fisiologia , Degeneração Neural/patologia , Sinapses/metabolismo , Esclerose Amiotrófica Lateral/patologia , Animais , Animais Geneticamente Modificados , Denervação , Dissecação , Congelamento , Humanos , Larva/metabolismo , Junção Neuromuscular/fisiologia , Coloração e Rotulagem , Tórax
16.
Neuron ; 107(3): 509-521.e7, 2020 08 05.
Artigo em Inglês | MEDLINE | ID: mdl-32492366

RESUMO

Post-tetanic potentiation (PTP) is an attractive candidate mechanism for hippocampus-dependent short-term memory. Although PTP has a uniquely large magnitude at hippocampal mossy fiber-CA3 pyramidal neuron synapses, it is unclear whether it can be induced by natural activity and whether its lifetime is sufficient to support short-term memory. We combined in vivo recordings from granule cells (GCs), in vitro paired recordings from mossy fiber terminals and postsynaptic CA3 neurons, and "flash and freeze" electron microscopy. PTP was induced at single synapses and showed a low induction threshold adapted to sparse GC activity in vivo. PTP was mainly generated by enlargement of the readily releasable pool of synaptic vesicles, allowing multiplicative interaction with other plasticity forms. PTP was associated with an increase in the docked vesicle pool, suggesting formation of structural "pool engrams." Absence of presynaptic activity extended the lifetime of the potentiation, enabling prolonged information storage in the hippocampal network.


Assuntos
Memória de Curto Prazo/fisiologia , Fibras Musgosas Hipocampais/metabolismo , Plasticidade Neuronal/fisiologia , Células Piramidais/metabolismo , Sinapses/metabolismo , Vesículas Sinápticas/metabolismo , Potenciais de Ação/fisiologia , Animais , Região CA3 Hipocampal/citologia , Giro Denteado/citologia , Camundongos , Microscopia Eletrônica , Fibras Musgosas Hipocampais/fisiologia , Fibras Musgosas Hipocampais/ultraestrutura , Técnicas de Patch-Clamp , Células Piramidais/fisiologia , Células Piramidais/ultraestrutura , Ratos , Sinapses/fisiologia , Potenciais Sinápticos/fisiologia
17.
Proc Natl Acad Sci U S A ; 117(22): 12428-12434, 2020 06 02.
Artigo em Inglês | MEDLINE | ID: mdl-32424101

RESUMO

Numerous genes whose mutations cause, or increase the risk of, Parkinson's disease (PD) have been identified. An inactivating mutation (R258Q) in the Sac inositol phosphatase domain of synaptojanin 1 (SJ1/PARK20), a phosphoinositide phosphatase implicated in synaptic vesicle recycling, results in PD. The gene encoding Sac2/INPP5F, another Sac domain-containing protein, is located within a PD risk locus identified by genome-wide association studies. Knock-In mice carrying the SJ1 patient mutation (SJ1RQKI) exhibit PD features, while Sac2 knockout mice (Sac2KO) do not have obvious neurologic defects. We report a "synthetic" effect of the SJ1 mutation and the KO of Sac2 in mice. Most mice with both mutations died perinatally. The occasional survivors had stunted growth, died within 3 wk, and showed abnormalities of striatal dopaminergic nerve terminals at an earlier stage than SJ1RQKI mice. The abnormal accumulation of endocytic factors observed at synapses of cultured SJ1RQKI neurons was more severe in double-mutant neurons. Our results suggest that SJ1 and Sac2 have partially overlapping functions and are consistent with a potential role of Sac2 as a PD risk gene.


Assuntos
Inositol Polifosfato 5-Fosfatases/genética , Doença de Parkinson/enzimologia , Animais , Dopamina/metabolismo , Estudo de Associação Genômica Ampla , Humanos , Inositol Polifosfato 5-Fosfatases/deficiência , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Mutação , Terminações Nervosas/metabolismo , Doença de Parkinson/genética , Fenótipo , Sinapses/metabolismo
18.
Nat Commun ; 11(1): 2140, 2020 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-32358586

RESUMO

The trans-synaptic interaction of the cell-adhesion molecules teneurins (TENs) with latrophilins (LPHNs/ADGRLs) promotes excitatory synapse formation when LPHNs simultaneously interact with FLRTs. Insertion of a short alternatively-spliced region within TENs abolishes the TEN-LPHN interaction and switches TEN function to specify inhibitory synapses. How alternative-splicing regulates TEN-LPHN interaction remains unclear. Here, we report the 2.9 Å resolution cryo-EM structure of the TEN2-LPHN3 complex, and describe the trimeric TEN2-LPHN3-FLRT3 complex. The structure reveals that the N-terminal lectin domain of LPHN3 binds to the TEN2 barrel at a site far away from the alternatively spliced region. Alternative-splicing regulates the TEN2-LPHN3 interaction by hindering access to the LPHN-binding surface rather than altering it. Strikingly, mutagenesis of the LPHN-binding surface of TEN2 abolishes the LPHN3 interaction and impairs excitatory but not inhibitory synapse formation. These results suggest that a multi-level coincident binding mechanism mediated by a cryptic adhesion complex between TENs and LPHNs regulates synapse specificity.


Assuntos
Proteínas de Membrana/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Receptores Acoplados a Proteínas-G/metabolismo , Sinapses/metabolismo , Processamento Alternativo/genética , Processamento Alternativo/fisiologia , Sítios de Ligação/genética , Células HEK293 , Humanos , Glicoproteínas de Membrana/química , Glicoproteínas de Membrana/genética , Glicoproteínas de Membrana/metabolismo , Proteínas de Membrana/química , Proteínas de Membrana/genética , Mutação/genética , Proteínas do Tecido Nervoso/química , Proteínas do Tecido Nervoso/genética , Ligação Proteica/genética , Estrutura Secundária de Proteína , Receptores Acoplados a Proteínas-G/química , Receptores Acoplados a Proteínas-G/genética , Receptores de Peptídeos/química , Receptores de Peptídeos/genética , Receptores de Peptídeos/metabolismo , Sinapses/fisiologia
19.
Toxicology ; 440: 152492, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32407874

RESUMO

Neurotoxicity induced by exposure to heavy metal lead (Pb) is a concern of utmost importance particularly for countries with industrial-based economies. The developing brain is especially sensitive to exposure to even minute quantities of Pb which can alter neurodevelopmental trajectory with irreversible effects on motor, emotive-social and cognitive attributes even into later adulthood. Chemical synapses form the major pathway of inter-neuronal communications and are prime candidates for higher order brain (motor, memory and behavior) functions and determine the resistance/susceptibility for neurological disorders, including neuropsychopathologies. The synaptic pathways and mechanisms underlying Pb-mediated alterations in neuronal signaling and plasticity are not completely understood. Employing a biochemically isolated synaptosomal fraction which is enriched in synaptic terminals and synaptic mitochondria, this study aimed to analyze the alterations in bioenergetic and redox/antioxidant status of cerebellar synapses induced by developmental exposure to Pb (0.2 %). Moreover, we test the efficacy of vitamin C (ascorbate; 500 mg/kg body weight), a neuroprotective and neuromodulatory antioxidant, in mitigation of Pb-induced neuronal deficits. Our results implicate redox and bioenergetic disruptions as an underlying feature of the synaptic dysfunction observed in developmental Pb neurotoxicity, potentially contributing to consequent deficits in motor, behavioral and psychological attributes of the organisms. In addition, we establish ascorbate as a key ingredient for therapeutic approach against Pb induced neurotoxicity, particularly for early-life exposures.


Assuntos
Antioxidantes/uso terapêutico , Ácido Ascórbico/uso terapêutico , Cerebelo/metabolismo , Metabolismo Energético/efeitos dos fármacos , Intoxicação do Sistema Nervoso por Chumbo/patologia , Sinapses/metabolismo , Animais , Antioxidantes/farmacologia , Ácido Ascórbico/farmacologia , Cerebelo/efeitos dos fármacos , Feminino , Glutationa/metabolismo , Chumbo/sangue , Intoxicação do Sistema Nervoso por Chumbo/psicologia , Masculino , Fármacos Neuroprotetores/farmacologia , Fármacos Neuroprotetores/uso terapêutico , Tamanho do Órgão/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Gravidez , Ratos , Ratos Wistar , Sinapses/efeitos dos fármacos , Sinaptossomos/efeitos dos fármacos , Sinaptossomos/metabolismo
20.
Toxicology ; 440: 152500, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32428529

RESUMO

Autism spectrum disorders (ASD) include neurodevelopmental disorders in which behavioral deficits can result from neuronal imbalance of excitation to inhibition (E/I) in the brain. Here we used RT-qPCR to screen for the expression of 99 genes associated with excitatory (glutamatergic) and inhibitory (GABAergic) neurotransmission in the cerebral cortex, hippocampus and cerebellum of rats in an established VPA model of ASD. The largest changes in the expression of glutamatergic genes were found in the cerebral cortex, where 12 genes including these encoding some of the subunits of the ionotropic glutamate receptors, were upregulated, while 2 genes were downregulated. The expression of genes encoding the presynaptic glutamatergic proteins vGluT1 and mGluR7 and PKA, involved in downstream glutamatergic signaling, was elevated more than 100-fold. Changes in GABAergic gene expression were found in the cortex, cerebellum and hippocampus; 3 genes were upregulated, and 3 were downregulated. In conclusion, these results revealed that, in the ASD model, several glutamatergic genes in the rat cerebral cortex were upregulated, which contrasts with small and balanced changes in the expression of GABAergic genes. The VPA rat model, useful in studying the molecular basis of ASD, may be suitable for testing experimental therapies in these disabilities.


Assuntos
Transtorno Autístico/induzido quimicamente , Transtorno Autístico/genética , Ácido Glutâmico/genética , Ácido Valproico , Ácido gama-Aminobutírico/genética , Animais , Cerebelo/efeitos dos fármacos , Cerebelo/metabolismo , Córtex Cerebral/efeitos dos fármacos , Córtex Cerebral/metabolismo , Feminino , GABAérgicos , Perfilação da Expressão Gênica , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Masculino , Gravidez , Efeitos Tardios da Exposição Pré-Natal , Ratos , Ratos Wistar , Receptores de Glutamato Metabotrópico/biossíntese , Receptores de Glutamato Metabotrópico/genética , Sinapses/efeitos dos fármacos , Sinapses/metabolismo , Proteína Vesicular 1 de Transporte de Glutamato/biossíntese , Proteína Vesicular 1 de Transporte de Glutamato/genética
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