RESUMEN
Inactivation of the ubiquitin ligase Ube3a causes the developmental disorder Angelman syndrome, whereas increased Ube3a dosage is associated with autism spectrum disorders. Despite the enriched localization of Ube3a in the axon terminals including presynapses, little is known about the presynaptic function of Ube3a and mechanisms underlying its presynaptic localization. We show that developmental synapse elimination requires presynaptic Ube3a activity in Drosophila neurons. We further identified the domain of Ube3a that is required for its interaction with the kinesin motor. Angelman syndrome-associated missense mutations in the interaction domain attenuate presynaptic targeting of Ube3a and prevent synapse elimination. Conversely, increased Ube3a activity in presynapses leads to precocious synapse elimination and impairs synaptic transmission. Our findings reveal the physiological role of Ube3a and suggest potential pathogenic mechanisms associated with Ube3a dysregulation.
Asunto(s)
Síndrome de Angelman , Trastorno del Espectro Autista , Proteínas de Drosophila , Drosophila melanogaster , Transmisión Sináptica , Ubiquitina-Proteína Ligasas , Animales , Síndrome de Angelman/enzimología , Síndrome de Angelman/genética , Trastorno del Espectro Autista/enzimología , Trastorno del Espectro Autista/genética , Regulación hacia Abajo , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Ubiquitina-Proteína Ligasas/genética , Ubiquitina-Proteína Ligasas/metabolismo , Sinapsis/enzimología , Sinapsis/genéticaRESUMEN
Mutations in leucine-rich repeat kinase 2 (LRRK2) cause Parkinson's disease with a similar clinical presentation and progression to idiopathic Parkinson's disease, and common variation is linked to disease risk. Recapitulation of the genotype in rodent models causes abnormal dopamine release and increases the susceptibility of dopaminergic neurons to insults, making LRRK2 a valuable model for understanding the pathobiology of Parkinson's disease. It is also a promising druggable target with targeted therapies currently in development. LRRK2 mRNA and protein expression in the brain is highly variable across regions and cellular identities. A growing body of work has demonstrated that pathogenic LRRK2 mutations disrupt striatal synapses before the onset of overt neurodegeneration. Several substrates and interactors of LRRK2 have been identified to potentially mediate these pre-neurodegenerative changes in a cell-type-specific manner. This review discusses the effects of pathogenic LRRK2 mutations in striatal neurons, including cell-type-specific and pathway-specific alterations. It also highlights several LRRK2 effectors that could mediate the alterations to striatal function, including Rabs and protein kinase A. The lessons learned from improving our understanding of the pathogenic effects of LRRK2 mutations in striatal neurons will be applicable to both dissecting the cell-type specificity of LRRK2 function in the transcriptionally diverse subtypes of dopaminergic neurons and also increasing our understanding of basal ganglia development and biology. Finally, it will inform the development of therapeutics for Parkinson's disease.
Asunto(s)
Cuerpo Estriado/enzimología , Proteína 2 Quinasa Serina-Treonina Rica en Repeticiones de Leucina/metabolismo , Sinapsis/enzimología , Secuencia de Aminoácidos , Animales , Modelos Animales de Enfermedad , Humanos , Proteína 2 Quinasa Serina-Treonina Rica en Repeticiones de Leucina/química , Proteína 2 Quinasa Serina-Treonina Rica en Repeticiones de Leucina/genética , Modelos Biológicos , Mutación/genéticaRESUMEN
Deleterious genetic variants in POGZ, which encodes the chromatin regulator Pogo Transposable Element with ZNF Domain protein, are strongly associated with autism spectrum disorder (ASD). Although it is a high-confidence ASD risk gene, the neurodevelopmental functions of POGZ remain unclear. Here we reveal the genomic binding of POGZ in the developing forebrain at euchromatic loci and gene regulatory elements (REs). We profile chromatin accessibility and gene expression in Pogz-/- mice and show that POGZ promotes the active chromatin state and transcription of clustered synaptic genes. We further demonstrate that POGZ forms a nuclear complex and co-occupies loci with ADNP, another high-confidence ASD risk gene, and provide evidence that POGZ regulates other neurodevelopmental disorder risk genes as well. Our results reveal a neurodevelopmental function of an ASD risk gene and identify molecular targets that may elucidate its function in ASD.
Asunto(s)
Trastorno Autístico/enzimología , Encéfalo/enzimología , Proteínas de Ciclo Celular/fisiología , Ensamble y Desensamble de Cromatina , Proteínas de Unión al ADN/fisiología , Eucromatina/metabolismo , Sinapsis/enzimología , Transposasas/metabolismo , Animales , Trastorno Autístico/genética , Trastorno Autístico/fisiopatología , Sitios de Unión , Encéfalo/crecimiento & desarrollo , Proteínas de Ciclo Celular/genética , Elementos Transponibles de ADN , Proteínas de Unión al ADN/genética , Elementos de Facilitación Genéticos , Eucromatina/genética , Femenino , Regulación del Desarrollo de la Expresión Génica , Predisposición Genética a la Enfermedad , Proteínas de Homeodominio/genética , Proteínas de Homeodominio/metabolismo , Masculino , Ratones Endogámicos C57BL , Ratones Noqueados , Proteínas del Tejido Nervioso/genética , Proteínas del Tejido Nervioso/metabolismo , Neurogénesis , Regiones Promotoras Genéticas , Sinapsis/genética , Transposasas/genéticaRESUMEN
Autism spectrum disorder (ASD) is a highly heritable neurodevelopmental disorder, causing defects of social interaction and repetitive behaviors. Here, we identify a de novo heterozygous gene-truncating mutation of the Sentrin-specific peptidase1 (SENP1) gene in people with ASD without neurodevelopmental delay. We find that Senp1+/- mice exhibit core autistic-like symptoms such as social deficits and repetitive behaviors but normal learning and memory ability. Moreover, we find that inhibitory and excitatory synaptic functions are severely affected in the retrosplenial agranular (RSA) cortex of Senp1+/- mice. Lack of Senp1 leads to increased SUMOylation and degradation of fragile X mental retardation protein (FMRP), also implicated in syndromic ASD. Importantly, re-introducing SENP1 or FMRP specifically in RSA fully rescues the defects of synaptic function and autistic-like symptoms of Senp1+/- mice. Together, these results demonstrate that disruption of the SENP1-FMRP regulatory axis in the RSA causes autistic symptoms, providing a candidate region for ASD pathophysiology.
Asunto(s)
Trastorno del Espectro Autista/enzimología , Conducta Animal , Cisteína Endopeptidasas/metabolismo , Giro del Cíngulo/enzimología , Sinapsis/enzimología , Animales , Trastorno del Espectro Autista/genética , Trastorno del Espectro Autista/fisiopatología , Trastorno del Espectro Autista/psicología , Estudios de Casos y Controles , Células Cultivadas , Cisteína Endopeptidasas/genética , Modelos Animales de Enfermedad , Potenciales Postsinápticos Excitadores , Femenino , Proteína de la Discapacidad Intelectual del Síndrome del Cromosoma X Frágil/metabolismo , Predisposición Genética a la Enfermedad , Aseo Animal , Giro del Cíngulo/fisiopatología , Haploinsuficiencia , Humanos , Potenciales Postsinápticos Inhibidores , Locomoción , Masculino , Aprendizaje por Laberinto , Ratones Endogámicos C57BL , Ratones Noqueados , Mutación , Fenotipo , Conducta Social , SumoilaciónRESUMEN
Cholinesterases are fundamental players in the peripheral and central nervous systems [...].
Asunto(s)
Acetilcolinesterasa/metabolismo , Butirilcolinesterasa/metabolismo , Sistema Nervioso Central/enzimología , Enfermedades Neurodegenerativas/enzimología , Neuronas/enzimología , Sistema Nervioso Periférico/enzimología , Acetilcolinesterasa/genética , Animales , Butirilcolinesterasa/genética , Sistema Nervioso Central/citología , Sistema Nervioso Central/efectos de los fármacos , Inhibidores de la Colinesterasa/uso terapéutico , Proteínas Ligadas a GPI/genética , Proteínas Ligadas a GPI/metabolismo , Expresión Génica , Humanos , Enfermedades Neurodegenerativas/tratamiento farmacológico , Enfermedades Neurodegenerativas/genética , Enfermedades Neurodegenerativas/patología , Neuronas/citología , Neuronas/efectos de los fármacos , Fármacos Neuroprotectores/uso terapéutico , Sistema Nervioso Periférico/citología , Sistema Nervioso Periférico/efectos de los fármacos , Sinapsis/efectos de los fármacos , Sinapsis/enzimología , Transmisión SinápticaRESUMEN
Neurofibrillary tangles composed of hyperphosphorylated tau and synaptic dysfunction are characteristics of Alzheimer's disease (AD). However, the underlying molecular mechanisms remain poorly understood. Here, we identified Amphiphysin I mediates both tau phosphorylation and synaptic dysfunction in AD. Amphiphysin I is cleaved by a cysteine proteinase asparagine endopeptidase (AEP) at N278 in the brains of AD patients. The amount of AEP-generated N-terminal fragment of Amphiphysin I (1-278) is increased with aging. Amphiphysin I (1-278) inhibits clathrin-mediated endocytosis and induces synaptic dysfunction. Furthermore, Amphiphysin I (1-278) binds p35 and promotes its transition to p25, thus activates CDK5 and enhances tau hyperphosphorylation. Overexpression of Amphiphysin I (1-278) in the hippocampus of Tau P301S mice induces synaptic dysfunction, tau hyperphosphorylation, and cognitive deficits. However, overexpression of the N278A mutant Amphiphysin I, which resists the AEP-mediated cleavage, alleviates the pathological and behavioral defects. These findings suggest a mechanism of tau hyperphosphorylation and synaptic dysfunction in AD.
Asunto(s)
Enfermedad de Alzheimer/enzimología , Encéfalo/enzimología , Cisteína Endopeptidasas/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Neuronas/enzimología , Sinapsis/enzimología , Proteínas tau/metabolismo , Enfermedad de Alzheimer/genética , Enfermedad de Alzheimer/patología , Enfermedad de Alzheimer/fisiopatología , Animales , Conducta Animal , Encéfalo/fisiopatología , Encéfalo/ultraestructura , Células COS , Estudios de Casos y Controles , Chlorocebus aethiops , Cognición , Quinasa 5 Dependiente de la Ciclina/metabolismo , Cisteína Endopeptidasas/genética , Modelos Animales de Enfermedad , Células HEK293 , Humanos , Aprendizaje por Laberinto , Ratones Endogámicos C57BL , Ratones Transgénicos , Proteínas del Tejido Nervioso/genética , Neuronas/ultraestructura , Fosforilación , Ratas , Sinapsis/ultraestructura , Proteínas tau/genéticaRESUMEN
Phosphodiesterase-10A (PDE10A) hydrolyse the secondary messengers cGMP and cAMP, two molecules playing important roles in neurodevelopment and brain functions. PDE10A is associated to progression of neurodegenerative diseases like Alzheimer's, Parkinson's, Huntington's diseases, and a critical role in cognitive functions. The present study was undertaken to determine the possible neuroprotective effects and the associated mechanism of papaverine (PAP), a PDE10A isoenzyme inhibitor, against quinolinic acid (QUIN)-induced excitotoxicity using human primary cortical neurons. Cytotoxicity potential of PAP was analysed using MTS assay. Reactive oxygen species (ROS) and mitochondrial membrane potential were measured by DCF-DA and JC10 staining, respectively. Caspase 3/7 and cAMP levels were measured using ELISA kits. Effect of PAP on the CREB, BNDF and synaptic proteins such as SAP-97, synaptophysin, synapsin-I, and PSD-95 expression was analysed by Western blot. Pre-treatment with PAP increased intracellular cAMP and nicotinamide adenine dinucleotide (NAD+) levels, restored mitochondrial membrane potential (ΔΨm), and decreased ROS and caspase 3/7 content in QUIN exposed neurons. PAP up-regulated CREB and BDNF, and synaptic protein expression. In summary, these data indicate that PDE10A is involved in QUIN-mediated synaptotoxicity and its inhibition elicit neuroprotection by reducing the oxidative stress and protecting synaptic proteins via up-regulation of cAMP signalling cascade.
Asunto(s)
Corteza Cerebral/efectos de los fármacos , Papaverina/farmacología , Inhibidores de Fosfodiesterasa/farmacología , Hidrolasas Diéster Fosfóricas , Ácido Quinolínico/toxicidad , Sinapsis/efectos de los fármacos , Supervivencia Celular/efectos de los fármacos , Supervivencia Celular/fisiología , Células Cultivadas , Corteza Cerebral/citología , Corteza Cerebral/enzimología , Relación Dosis-Respuesta a Droga , Humanos , Neuronas/efectos de los fármacos , Neuronas/enzimología , Hidrolasas Diéster Fosfóricas/metabolismo , Sinapsis/enzimologíaRESUMEN
Ubiquitination is a key posttranslational modification for the controlled protein degradation and proteostasis. The substrate specificity is determined by a family of E3 ubiquitin ligases, which are encoded by more than 600 genes in the mammalian genome. Gain- or loss-of-function of a number of E3 genes results in neurodegeneration or neurodevelopmental disorders, affecting synapse function. This implies that the specific ubiquitination of synaptic substrates are of crucial importance for the normal neuronal network. In this review, we will summarize the history, current topics, and challenges in the field of ubiquitination-dependent regulations of synaptogenesis and synaptic transmission.
Asunto(s)
Encéfalo/enzimología , Proteínas del Tejido Nervioso/fisiología , Sinapsis/enzimología , Ubiquitina-Proteína Ligasas/fisiología , Ubiquitinación , Animales , Encéfalo/patología , Humanos , Ratones , Familia de Multigenes , Degeneración Nerviosa/enzimología , Trastornos del Neurodesarrollo/enzimología , Trastornos del Neurodesarrollo/genética , Plasticidad Neuronal , Enfermedad de Parkinson/enzimología , Complejo de la Endopetidasa Proteasomal/metabolismo , Procesamiento Proteico-Postraduccional , Proteostasis , Dominios RING Finger , Transmisión Sináptica , Ubiquitina-Proteína Ligasas/clasificación , Ubiquitina-Proteína Ligasas/genéticaRESUMEN
Emerging evidence suggests that epigenetic mechanisms regulate aberrant gene transcription in stress-associated mental disorders. However, it remains to be elucidated about the role of DNA methylation and its catalyzing enzymes, DNA methyltransferases (DNMTs), in this process. Here, we found that male rats exposed to chronic (2-week) unpredictable stress exhibited a substantial reduction of Dnmt3a after stress cessation in the prefrontal cortex (PFC), a key target region of stress. Treatment of unstressed control rats with DNMT inhibitors recapitulated the effect of chronic unpredictable stress on decreased AMPAR expression and function in PFC. In contrast, overexpression of Dnmt3a in PFC of stressed animals prevented the loss of glutamatergic responses. Moreover, the stress-induced behavioral abnormalities, including the impaired recognition memory, heightened aggression, and hyperlocomotion, were partially attenuated by Dnmt3a expression in PFC of stressed animals. Finally, we found that there were genome-wide DNA methylation changes and transcriptome alterations in PFC of stressed rats, both of which were enriched at several neural pathways, including glutamatergic synapse and microtubule-associated protein kinase signaling. These results have therefore recognized the potential role of DNA epigenetic modification in stress-induced disturbance of synaptic functions and cognitive and emotional processes.
Asunto(s)
ADN Metiltransferasa 3A/metabolismo , Locomoción/fisiología , Corteza Prefrontal/enzimología , Estrés Psicológico/enzimología , Estrés Psicológico/psicología , Sinapsis/enzimología , Animales , Enfermedad Crónica , ADN Metiltransferasa 3A/antagonistas & inhibidores , Conducta Exploratoria/efectos de los fármacos , Conducta Exploratoria/fisiología , Locomoción/efectos de los fármacos , Masculino , Ratones , Ftalimidas/farmacología , Corteza Prefrontal/efectos de los fármacos , Ratas , Ratas Sprague-Dawley , Triptófano/análogos & derivados , Triptófano/farmacologíaRESUMEN
Here we describe mechanistically distinct enzymes (a kinase, a guanosine triphosphatase, and a ubiquitin protein hydrolase) that function in disparate biochemical pathways and can also act in concert to mediate a series of redox reactions. Each enzyme manifests a second, noncanonical function-transnitrosylation-that triggers a pathological biochemical cascade in mouse models and in humans with Alzheimer's disease (AD). The resulting series of transnitrosylation reactions contributes to synapse loss, the major pathological correlate to cognitive decline in AD. We conclude that enzymes with distinct primary reaction mechanisms can form a completely separate network for aberrant transnitrosylation. This network operates in the postreproductive period, so natural selection against such abnormal activity may be decreased.
Asunto(s)
Enfermedad de Alzheimer/enzimología , Quinasa 5 Dependiente de la Ciclina/metabolismo , Dinaminas/metabolismo , Óxido Nítrico Sintasa/metabolismo , Óxido Nítrico/metabolismo , Sinapsis/enzimología , Enfermedad de Alzheimer/patología , Péptidos beta-Amiloides/metabolismo , Animales , Cisteína/genética , Cisteína/metabolismo , Modelos Animales de Enfermedad , Células HEK293 , Humanos , Ratones , Ratones Transgénicos , Mutación , Nitroarginina/farmacología , Oxidación-Reducción , Procesamiento Proteico-Postraduccional/efectos de los fármacos , Sinapsis/patología , Ubiquitina Tiolesterasa/genética , Ubiquitina Tiolesterasa/metabolismoRESUMEN
The calcium/calmodulin-dependent protein kinase II (CaMKII) is a ubiquitous and central player in Ca2+ signaling that is best known for its functions in the brain. In particular, the α isoform of CaMKII has been the subject of intense research and it has been established as a central regulator of neuronal plasticity. In contrast, little attention has been paid to CaMKIIß, the other predominant brain isoform that interacts directly with the actin cytoskeleton, and the functions of CaMKIIß in this organ remain largely unexplored. However, recently, the perturbation of CaMKIIß expression has been associated with multiple neuropsychiatric and neurodevelopmental diseases, highlighting CAMK2B as a gene of interest. Herein, after highlighting the main structural and expression differences between the α and ß isoforms, we will review the specific functions of CaMKIIß, as described so far, in neuronal development and plasticity, as well as its potential implication in brain diseases.
Asunto(s)
Encéfalo/enzimología , Proteína Quinasa Tipo 2 Dependiente de Calcio Calmodulina/genética , Trastornos Mentales/genética , Trastornos del Neurodesarrollo/genética , Plasticidad Neuronal/fisiología , Neuronas/enzimología , Animales , Encéfalo/fisiopatología , Proteína Quinasa Tipo 2 Dependiente de Calcio Calmodulina/química , Proteína Quinasa Tipo 2 Dependiente de Calcio Calmodulina/metabolismo , Movimiento Celular , Regulación de la Expresión Génica , Humanos , Isoenzimas/química , Isoenzimas/genética , Isoenzimas/metabolismo , Memoria/fisiología , Trastornos Mentales/enzimología , Trastornos Mentales/fisiopatología , Mutación , Trastornos del Neurodesarrollo/enzimología , Trastornos del Neurodesarrollo/fisiopatología , Neuronas/ultraestructura , Transducción de Señal , Sinapsis/enzimología , Sinapsis/ultraestructuraRESUMEN
Many studies have revealed a central role of p38 MAPK in neuronal plasticity and the regulation of long-term changes in synaptic efficacy, such as long-term potentiation (LTP) and long-term depression (LTD). However, p38 MAPK is classically known as a responsive element to stress stimuli, including neuroinflammation. Specific to the pathophysiology of Alzheimer's disease (AD), several studies have shown that the p38 MAPK cascade is activated either in response to the Aß peptide or in the presence of tauopathies. Here, we describe the role of p38 MAPK in the regulation of synaptic plasticity and its implication in an animal model of neurodegeneration. In particular, recent evidence suggests the p38 MAPK α isoform as a potential neurotherapeutic target, and specific inhibitors have been developed and have proven to be effective in ameliorating synaptic and memory deficits in AD mouse models.
Asunto(s)
Sinapsis/enzimología , Sinapsis/patología , Proteínas Quinasas p38 Activadas por Mitógenos/metabolismo , Animales , Encéfalo/patología , Humanos , Inflamación/patología , Inhibidores de Proteínas Quinasas/farmacología , Bibliotecas de Moléculas Pequeñas/farmacología , Sinapsis/efectos de los fármacos , Proteínas Quinasas p38 Activadas por Mitógenos/antagonistas & inhibidoresRESUMEN
Excessive excitation is hypothesized to cause motoneuron (MN) degeneration in amyotrophic lateral sclerosis (ALS), but actual proof of hyperexcitation in vivo is missing, and trials based on this concept have failed. We demonstrate, by in vivo single-MN electrophysiology, that, contrary to expectations, excitatory responses evoked by sensory and brainstem inputs are reduced in MNs of presymptomatic mutSOD1 mice. This impairment correlates with disrupted postsynaptic clustering of Homer1b, Shank, and AMPAR subunits. Synaptic restoration can be achieved by activation of the cAMP/PKA pathway, by either intracellular injection of cAMP or DREADD-Gs stimulation. Furthermore, we reveal, through independent control of signaling and excitability allowed by multiplexed DREADD/PSAM chemogenetics, that PKA-induced restoration of synapses triggers an excitation-dependent decrease in misfolded SOD1 burden and autophagy overload. In turn, increased MN excitability contributes to restoring synaptic structures. Thus, the decrease of excitation to MN is an early but reversible event in ALS. Failure of the postsynaptic site, rather than hyperexcitation, drives disease pathobiochemistry.
Asunto(s)
Esclerosis Amiotrófica Lateral/enzimología , Proteínas Quinasas Dependientes de AMP Cíclico/metabolismo , Neuronas Motoras/enzimología , Neuroprotección , Transducción de Señal , Sinapsis/enzimología , Esclerosis Amiotrófica Lateral/genética , Esclerosis Amiotrófica Lateral/patología , Animales , Proteínas Quinasas Dependientes de AMP Cíclico/genética , Humanos , Ratones , Ratones Transgénicos , Neuronas Motoras/patología , Superóxido Dismutasa-1/genética , Superóxido Dismutasa-1/metabolismo , Sinapsis/genética , Sinapsis/patologíaRESUMEN
Structural changes in pre and postsynaptic neurons that accompany synapse formation often temporally and spatially overlap. Thus, it has been difficult to resolve which processes drive patterned connectivity. To overcome this, we use the laminated outer murine retina. We identify the serine/threonine kinase LKB1 as a key driver of synapse layer emergence. The absence of LKB1 in the retina caused a marked mislocalization and delay in synapse layer formation. In parallel, LKB1 modulated postsynaptic horizontal cell refinement and presynaptic photoreceptor axon growth. Mislocalized horizontal cell processes contacted aberrant cone axons in LKB1 mutants. These defects coincided with altered synapse protein organization, and horizontal cell neurites were misdirected to ectopic synapse protein regions. Together, these data suggest that LKB1 instructs the timing and location of connectivity in the outer retina via coordinate regulation of pre and postsynaptic neuron structure and the localization of synapse-associated proteins.
Asunto(s)
Neuritas/enzimología , Neurogénesis , Células Fotorreceptoras/enzimología , Proteínas Serina-Treonina Quinasas/metabolismo , Sinapsis/enzimología , Proteínas Quinasas Activadas por AMP , Animales , Femenino , Masculino , Ratones Noqueados , Mutación , Proteínas Serina-Treonina Quinasas/genética , Transporte de Proteínas , Proteína 1 de Transporte Vesicular de Glutamato/metabolismoRESUMEN
In eukaryotic cells, with the exception of the specialized genomes of mitochondria and plastids, all genetic information is sequestered within the nucleus. This arrangement imposes constraints on how the information can be tailored for different cellular regions, particularly in cells with complex morphologies like neurons. Although messenger RNAs (mRNAs), and the proteins that they encode, can be differentially sorted between cellular regions, the information itself does not change. RNA editing by adenosine deamination can alter the genome's blueprint by recoding mRNAs; however, this process too is thought to be restricted to the nucleus. In this work, we show that ADAR2 (adenosine deaminase that acts on RNA), an RNA editing enzyme, is expressed outside of the nucleus in squid neurons. Furthermore, purified axoplasm exhibits adenosine-to-inosine activity and can specifically edit adenosines in a known substrate. Finally, a transcriptome-wide analysis of RNA editing reveals that tens of thousands of editing sites (>70% of all sites) are edited more extensively in the squid giant axon than in its cell bodies. These results indicate that within a neuron RNA editing can recode genetic information in a region-specific manner.
Asunto(s)
Adenosina Desaminasa/metabolismo , Neuronas/enzimología , Edición de ARN , Adenosina/metabolismo , Animales , Axones/enzimología , Citoplasma/enzimología , Decapodiformes/enzimología , Células HEK293 , Humanos , Inosina/metabolismo , Canales de Potasio con Entrada de Voltaje/genética , Canales de Potasio con Entrada de Voltaje/metabolismo , Sinapsis/enzimologíaRESUMEN
Nerve agents inhibit acetylcholinesterase (AChE), leading to a build-up of acetylcholine (ACh) and overstimulation at cholinergic synapses. Current post-exposure nerve agent treatment includes atropine to treat overstimulation at muscarinic synapses, a benzodiazepine anti-convulsant, and an oxime to restore the function of AChE. Aside from the oxime, the components do not act directly to reduce the overstimulation at nicotinic synapses. The false transmitters acetylmonoethylcholine (AMECh) and acetyldiethylcholine (ADECh) are analogs of ACh, synthesised similarly at synapses. AMECh and ADECh are partial agonists, with reduced activity compared to ACh, so it was hypothesised the false transmitters could reduce overstimulation. Synthetic routes to AMECh and ADECh, and their precursors, monoethylcholine (MECh) and diethylcholine (DECh), were devised, allowing them to be produced easily on a laboratory-scale. The mechanism of action of the false transmitters was investigated in vitro. AMECh acted as a partial agonist at human muscarinic (M1 and M3) and muscle-type nicotinic receptors, and ADECh was a partial agonist only at certain muscarinic subtypes. Their precursors acted as antagonists at muscle-type nicotinic, but not muscarinic receptors. Administration of MECh and DECh improved neuromuscular function in the soman-exposed guinea-pig hemi-diaphragm preparation. False transmitters may therefore help reduce nerve agent induced overstimulation at cholinergic synapses.
Asunto(s)
Acetilcolina/análogos & derivados , Antídotos/farmacología , Colina/análogos & derivados , Inhibidores de la Colinesterasa/envenenamiento , Diafragma/inervación , Agentes Nerviosos/envenenamiento , Neurotransmisores/farmacología , Intoxicación por Organofosfatos/tratamiento farmacológico , Soman/envenenamiento , Sinapsis/efectos de los fármacos , Acetilcolina/síntesis química , Acetilcolina/metabolismo , Acetilcolina/farmacología , Acetilcolinesterasa/metabolismo , Animales , Antídotos/síntesis química , Células CHO , Línea Celular Tumoral , Colina/síntesis química , Colina/farmacología , Cricetulus , Agonismo Parcial de Drogas , Cobayas , Humanos , Masculino , Neurotransmisores/síntesis química , Intoxicación por Organofosfatos/enzimología , Intoxicación por Organofosfatos/fisiopatología , Receptores Colinérgicos/efectos de los fármacos , Receptores Colinérgicos/genética , Receptores Colinérgicos/metabolismo , Sinapsis/enzimologíaRESUMEN
Central nervous system (CNS) circuit development requires subcellular control of synapse formation and patterning of synapse abundance. We identified the Drosophila membrane-anchored phosphatase of regenerating liver (Prl-1) as an axon-intrinsic factor that promotes synapse formation in a spatially restricted fashion. The loss of Prl-1 in mechanosensory neurons reduced the number of CNS presynapses localized on a single axon collateral and organized as a terminal arbor. Flies lacking all Prl-1 protein had locomotor defects. The overexpression of Prl-1 induced ectopic synapses. In mechanosensory neurons, Prl-1 modulates the insulin receptor (InR) signaling pathway within a single contralateral axon compartment, thereby affecting the number of synapses. The axon branch-specific localization and function of Prl-1 depend on untranslated regions of the prl-1 messenger RNA (mRNA). Therefore, compartmentalized restriction of Prl-1 serves as a specificity factor for the subcellular control of axonal synaptogenesis.
Asunto(s)
Axones/fisiología , Sistema Nervioso Central/crecimiento & desarrollo , Proteínas de Drosophila/fisiología , Drosophila melanogaster/crecimiento & desarrollo , Proteínas Tirosina Fosfatasas/fisiología , Sinapsis/fisiología , Animales , Axones/enzimología , Sistema Nervioso Central/enzimología , Proteínas de Drosophila/química , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/genética , Locomoción/genética , Locomoción/fisiología , Mecanorreceptores/enzimología , Fosfatidilinositoles/metabolismo , Dominios Proteicos , Proteínas Tirosina Fosfatasas/química , Proteínas Tirosina Fosfatasas/genética , Proteínas Proto-Oncogénicas c-akt/metabolismo , Proteínas Tirosina Quinasas Receptoras/metabolismo , Sinapsis/enzimologíaRESUMEN
During postnatal neurodevelopment, excessive synapses must be eliminated by microglia to complete the establishment of neural circuits in the brain. The lack of synaptic regulation by microglia has been implicated in neurodevelopmental disorders such as autism, schizophrenia, and intellectual disability. Here we suggest that vaccinia-related kinase 2 (VRK2), which is expressed in microglia, may stimulate synaptic elimination by microglia. In VRK2-deficient mice (VRK2KO ), reduced numbers of presynaptic puncta within microglia were observed. Moreover, the numbers of presynaptic puncta and synapses were abnormally increased in VRK2KO mice by the second postnatal week. These differences did not persist into adulthood. Even though an increase in the number of synapses was normalized, adult VRK2KO mice showed behavioral defects in social behaviors, contextual fear memory, and spatial memory.
Asunto(s)
Encéfalo/enzimología , Encéfalo/crecimiento & desarrollo , Microglía/enzimología , Proteínas Serina-Treonina Quinasas/metabolismo , Sinapsis/enzimología , Animales , Encéfalo/citología , Células Cultivadas , Potenciales Postsinápticos Excitadores/fisiología , Miedo/fisiología , Humanos , Masculino , Memoria/fisiología , Ratones Endogámicos C57BL , Ratones Noqueados , Microglía/citología , Potenciales Postsinápticos Miniatura/fisiología , Proteínas Serina-Treonina Quinasas/genética , Conducta Social , Técnicas de Cultivo de TejidosRESUMEN
Axonal extension and synaptic targeting are usually completed during early development, but the axonal length and synaptic integrity need to be actively maintained during later developmental stages and the adult life. Failure in the axonal length maintenance and the subsequent axonal degeneration have been associated with neurological disorders, but currently little is known about the genetic factors controlling this process. Here, we show that regulated intracellular levels of cAMP-dependent protein kinase A (PKA) are critical for the axon maintenance during the transition from the early to the later larval stages in the Drosophila class IV dendritic arborization (da) sensory neurons. Our data indicate that when the intracellular levels of PKA are increased via genetic manipulations, these peripheral neurons initially form synapses with wild-type appearance, at their predicted ventral nerve cord (VNC) target sites (in the first and second instar larval stages), but that their synapses disintegrate, and the axons retract and become fragmented in the subsequent larval stages (third larval stage). The affected axonal endings at the disintegrated synaptic sites still express the characteristic presynaptic and cytoskeletal markers such as Bruchpilot and Fascin, indicating that the synapse had been initially properly formed, but that it later lost its integrity. Finally, the phenotype is significantly more prominent in the axons of the neurons whose cell bodies are located in the posterior body segments. We propose that the reason for this is the fact that during the larval development the posterior neurons face a much greater challenge while trying to keep up with the fast-paced growth of the larval body, and that PKA is critical for this process. Our data reveal PKA as a novel factor in the axonal length and synapse integrity maintenance in sensory neurons. These results could be of help in understanding neurological disorders characterized by destabilized synapses.