RESUMEN
Ca(2+)-triggered neurotransmitter release is characterized by two kinetically distinct components: a fast synchronous phase and a slow asynchronous phase. Yao et al. (2011) now report that double C2 domain (Doc2) proteins function as high-affinity Ca(2+) sensors to specifically regulate the asynchronous component of neurotransmitter release.
RESUMEN
Peroxisome biogenesis disorders (PBD) are a group of multi-system human diseases due to mutations in the PEX genes that are responsible for peroxisome assembly and function. These disorders lead to global defects in peroxisomal function and result in severe brain, liver, bone and kidney disease. In order to study their pathogenesis we undertook a systematic genetic and biochemical study of Drosophila pex16 and pex2 mutants. These mutants are short-lived with defects in locomotion and activity. Moreover these mutants exhibit severe morphologic and functional peroxisomal defects. Using metabolomics we uncovered defects in multiple biochemical pathways including defects outside the canonical specialized lipid pathways performed by peroxisomal enzymes. These included unanticipated changes in metabolites in glycolysis, glycogen metabolism, and the pentose phosphate pathway, carbohydrate metabolic pathways that do not utilize known peroxisomal enzymes. In addition, mutant flies are starvation sensitive and are very sensitive to glucose deprivation exhibiting dramatic shortening of lifespan and hyperactivity on low-sugar food. We use bioinformatic transcriptional profiling to examine gene co-regulation between peroxisomal genes and other metabolic pathways and we observe that the expression of peroxisomal and carbohydrate pathway genes in flies and mouse are tightly correlated. Indeed key steps in carbohydrate metabolism were found to be strongly co-regulated with peroxisomal genes in flies and mice. Moreover mice lacking peroxisomes exhibit defective carbohydrate metabolism at the same key steps in carbohydrate breakdown. Our data indicate an unexpected link between these two metabolic processes and suggest metabolism of carbohydrates could be a new therapeutic target for patients with PBD.
Asunto(s)
Metabolismo de los Hidratos de Carbono , Trastorno Peroxisomal/genética , Peroxisomas/metabolismo , Animales , Drosophila/genética , Drosophila/metabolismo , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Glucosa/metabolismo , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Ratones , Mutación , Factor 2 de la Biogénesis del Peroxisoma , Peroxisomas/genética , TranscriptomaRESUMEN
Hedgehog (Hh) signaling regulates multiple aspects of metazoan development and tissue homeostasis, and is constitutively active in numerous cancers. We identified Ubr3, an E3 ubiquitin ligase, as a novel, positive regulator of Hh signaling in Drosophila and vertebrates. Hh signaling regulates the Ubr3-mediated poly-ubiquitination and degradation of Cos2, a central component of Hh signaling. In developing Drosophila eye discs, loss of ubr3 leads to a delayed differentiation of photoreceptors and a reduction in Hh signaling. In zebrafish, loss of Ubr3 causes a decrease in Shh signaling in the developing eyes, somites, and sensory neurons. However, not all tissues that require Hh signaling are affected in zebrafish. Mouse UBR3 poly-ubiquitinates Kif7, the mammalian homologue of Cos2. Finally, loss of UBR3 up-regulates Kif7 protein levels and decreases Hh signaling in cultured cells. In summary, our work identifies Ubr3 as a novel, evolutionarily conserved modulator of Hh signaling that boosts Hh in some tissues.
Asunto(s)
Proteínas de Drosophila/genética , Ojo/metabolismo , Cinesinas/genética , Ubiquitina-Proteína Ligasas/genética , Animales , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/genética , Drosophila melanogaster/crecimiento & desarrollo , Ojo/crecimiento & desarrollo , Proteínas Hedgehog/genética , Cinesinas/metabolismo , Ratones , Células Fotorreceptoras/metabolismo , Poliubiquitina , Proteolisis , ARN Interferente Pequeño , Transducción de Señal , Ubiquitina-Proteína Ligasas/metabolismo , Ubiquitinación , Pez Cebra/genéticaRESUMEN
Using a Drosophila model of Alzheimer's disease (AD), we systematically evaluated 67 candidate genes based on AD-associated genomic loci (P < 10(-4)) from published human genome-wide association studies (GWAS). Genetic manipulation of 87 homologous fly genes was tested for modulation of neurotoxicity caused by human Tau, which forms neurofibrillary tangle pathology in AD. RNA interference (RNAi) targeting 9 genes enhanced Tau neurotoxicity, and in most cases reciprocal activation of gene expression suppressed Tau toxicity. Our screen implicates cindr, the fly ortholog of the human CD2AP AD susceptibility gene, as a modulator of Tau-mediated disease mechanisms. Importantly, we also identify the fly orthologs of FERMT2 and CELF1 as Tau modifiers, and these loci have been independently validated as AD susceptibility loci in the latest GWAS meta-analysis. Both CD2AP and FERMT2 have been previously implicated with roles in cell adhesion, and our screen additionally identifies a fly homolog of the human integrin adhesion receptors, ITGAM and ITGA9, as a modifier of Tau neurotoxicity. Our results highlight cell adhesion pathways as important in Tau toxicity and AD susceptibility and demonstrate the power of model organism genetic screens for the functional follow-up of human GWAS.
Asunto(s)
Enfermedad de Alzheimer/genética , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Proteínas tau/genética , Animales , Animales Modificados Genéticamente , Antígeno CD11b/genética , Modelos Animales de Enfermedad , Proteínas de Drosophila/metabolismo , Técnicas de Silenciamiento del Gen , Estudios de Asociación Genética , Predisposición Genética a la Enfermedad , Humanos , Integrinas/genética , Interferencia de ARNRESUMEN
Notch signaling is an evolutionarily conserved pathway that plays a central role in numerous developmental and disease processes. The versatility of the Notch pathway relies on the activity of context-dependent regulators. These include rab11, sec15, arp3 and Drosophila EHBP1 (dEHBP1), which control Notch signaling and cell fate acquisition in asymmetrically dividing mechanosensory lineages by regulating the trafficking of the ligand Delta. Here, we show that dEHBP1 also controls the specification of R8 photoreceptors, as its loss results in the emergence of supernumerary R8 photoreceptors. Given the requirements for Notch signaling during lateral inhibition, we propose that dEHBP1 regulates distinct aspects of Notch signaling in different developmental contexts. We show that dEHBP1 regulates the exocytosis of Scabrous, a positive regulator of Notch signaling. In conclusion, dEHBP1 provides developmental versatility of intercellular signaling by regulating the trafficking of distinct Notch signaling components.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales/metabolismo , Proteínas de Drosophila/metabolismo , Proteínas de la Membrana/genética , Receptores Notch/metabolismo , Proteínas Adaptadoras Transductoras de Señales/genética , Animales , Diferenciación Celular/fisiología , Drosophila , Proteínas de Drosophila/genética , Hormonas de Insectos/biosíntesis , Hormonas de Insectos/genética , Proteínas de la Membrana/biosíntesis , Células Fotorreceptoras de Invertebrados/metabolismo , Unión Proteica , Receptores Notch/genética , Transducción de SeñalRESUMEN
bHLH-O proteins are a subfamily of the basic-helix-loop-helix transcription factors characterized by an 'Orange' protein-protein interaction domain. Typical members are the Hairy/E(spl), or Hes, proteins, well studied in their ability, among others, to suppress neuronal differentiation in both invertebrates and vertebrates. Hes proteins are often effectors of Notch signalling. In vertebrates, another bHLH-O protein group, the Hey proteins, have also been shown to be Notch targets and to interact with Hes. We have studied the single Drosophila Hey orthologue. We show that it is primarily expressed in a subset of newly born neurons, which receive Notch signalling during their birth. Unlike in vertebrates, however, Hey is not expressed in precursor cells and does not block neuronal differentiation. It rather promotes one of two alternative fates that sibling neurons adopt at birth. Although in the majority of cases Hey is a Notch target, it is also expressed independently of Notch in some lineages, most notably the larval mushroom body. The availability of Hey as a Notch readout has allowed us to study Notch signalling during the genesis of secondary neurons in the larval central nervous system.
Asunto(s)
Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismo , Proteínas de Drosophila/metabolismo , Drosophila/embriología , Neurogénesis/fisiología , Neuronas/metabolismo , Receptores Notch/metabolismo , Animales , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/genética , Proteínas de Drosophila/genética , Embrión no Mamífero , Regulación del Desarrollo de la Expresión Génica , Inmunohistoquímica , Hibridación in Situ , Larva/citología , Larva/crecimiento & desarrollo , Larva/metabolismo , Neurogénesis/genética , Neuroglía/metabolismo , Neuronas/citologíaRESUMEN
The adult Drosophila external sensory organ (ESO), comprising the hair, socket, neuron, sheath and glia cells, arises through the asymmetric division of sensory organ precursor cells (SOPs). In a mosaic screen designed to identify new components in ESO development, we isolated mutations in sequoia, which encodes a putative zinc-finger transcription factor that has previously been shown to have a role in dendritogenesis. Here, we show that adult clones mutant for seq exhibit a loss of hair cells and a gain of socket cells. We propose that the seq mutant phenotype arises, in part, owing to the loss of several crucial transcription factors known to be important in peripheral nervous system development such as D-Pax2, Prospero and Hamlet. Thus, Sequoia is a new upstream regulator of genes that orchestrates cell fate specification during development of the adult ESO lineage.
Asunto(s)
Linaje de la Célula , Proteínas de Unión al ADN/metabolismo , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/citología , Drosophila melanogaster/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Órganos de los Sentidos/citología , Órganos de los Sentidos/metabolismo , Animales , Mutación/genética , Fenotipo , Receptores Notch/metabolismo , Transducción de SeñalRESUMEN
In an unbiased genetic screen designed to isolate mutations that affect synaptic transmission, we have isolated homozygous lethal mutations in Drosophila importin 13 (imp13). Imp13 is expressed in and around nuclei of both neurons and muscles. At the larval neuromuscular junction (NMJ), imp13 affects muscle growth and formation of the subsynaptic reticulum without influencing any presynaptic structural features. In the absence of imp13, the probability of release of neurotransmitter and quantal content is increased, yet the abundance of the postsynaptic receptors and the amplitude of miniature excitatory junctional potentials are not affected. Interestingly, imp13 is required in the muscles to control presynaptic release. Thus, imp13 is a novel factor that affects neurotransmitter release at the fly NMJ. Its role in the context of synaptic homeostasis is discussed.
Asunto(s)
Proteínas de Drosophila/fisiología , Carioferinas/fisiología , Unión Neuromuscular/metabolismo , Neurotransmisores/metabolismo , Animales , Proteínas de Drosophila/genética , Drosophila melanogaster , Carioferinas/genética , Larva/genética , Larva/fisiología , Mutación , Unión Neuromuscular/genética , Unión Neuromuscular/ultraestructura , Neurotransmisores/genéticaRESUMEN
Many Alzheimer's disease (AD) genes including Apolipoprotein E (APOE) are found to be expressed in blood-derived macrophages and thus may alter blood protein levels. We measured 91 neuro-proteins in plasma from 316 participants of the Rotterdam Study (incident AD = 161) using Proximity Extension Ligation assay. We studied the association of plasma proteins with AD in the overall sample and stratified by APOE. Findings from the Rotterdam study were replicated in 186 AD patients of the BioFINDER study. We further evaluated the correlation of these protein biomarkers with total tau (t-tau), phosphorylated tau (p-tau) and amyloid-beta (Aß) 42 levels in cerebrospinal fluid (CSF) in the Amsterdam Dementia Cohort (N = 441). Finally, we conducted a genome-wide association study (GWAS) to identify the genetic variants determining the blood levels of AD-associated proteins. Plasma levels of the proteins, CDH6 (ß = 0.638, P = 3.33 × 10-4) and HAGH (ß = 0.481, P = 7.20 × 10-4), were significantly elevated in APOE ε4 carrier AD patients. The findings in the Rotterdam Study were replicated in the BioFINDER study for both CDH6 (ß = 1.365, P = 3.97 × 10-3) and HAGH proteins (ß = 0.506, P = 9.31 × 10-7) when comparing cases and controls in APOE ε4 carriers. In the CSF, CDH6 levels were positively correlated with t-tau and p-tau in the total sample as well as in APOE ε4 stratum (P < 1 × 10-3). The HAGH protein was not detected in CSF. GWAS of plasma CDH6 protein levels showed significant association with a cis-regulatory locus (rs111283466, P = 1.92 × 10-9). CDH6 protein is implicated in cell adhesion and synaptogenesis while HAGH protein is related to the oxidative stress pathway. Our findings suggest that these pathways may be altered during presymptomatic AD and that CDH6 and HAGH may be new blood-based biomarkers.
Asunto(s)
Enfermedad de Alzheimer/metabolismo , Apolipoproteína E4/metabolismo , Cadherinas/metabolismo , Tamización de Portadores Genéticos , Tioléster Hidrolasas/metabolismo , Apolipoproteína E4/genética , Biomarcadores/sangre , HumanosRESUMEN
The Alzheimer's disease (AD) susceptibility gene, CD2-associated protein (CD2AP), encodes an actin binding adaptor protein, but its function in the nervous system is largely unknown. Loss of the Drosophila ortholog cindr enhances neurotoxicity of human Tau, which forms neurofibrillary tangle pathology in AD. We show that Cindr is expressed in neurons and present at synaptic terminals. cindr mutants show impairments in synapse maturation and both synaptic vesicle recycling and release. Cindr associates and genetically interacts with 14-3-3ζ, regulates the ubiquitin-proteasome system, and affects turnover of Synapsin and the plasma membrane calcium ATPase (PMCA). Loss of cindr elevates PMCA levels and reduces cytosolic calcium. Studies of Cd2ap null mice support a conserved role in synaptic proteostasis, and CD2AP protein levels are inversely related to Synapsin abundance in human postmortem brains. Our results reveal CD2AP neuronal requirements with relevance to AD susceptibility, including for proteostasis, calcium handling, and synaptic structure and function.
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Proteínas 14-3-3/metabolismo , Proteínas Adaptadoras Transductoras de Señales/metabolismo , Enfermedad de Alzheimer , Proteínas del Citoesqueleto/metabolismo , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/metabolismo , Proteínas de Microfilamentos/metabolismo , Neuronas/metabolismo , Proteostasis , Proteínas 14-3-3/genética , Proteínas Adaptadoras Transductoras de Señales/genética , Animales , Proteínas del Citoesqueleto/genética , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Drosophila melanogaster/crecimiento & desarrollo , Femenino , Humanos , Masculino , Ratones , Proteínas de Microfilamentos/genética , Neuronas/citología , Proteoma/análisis , Proteoma/metabolismo , Transmisión SinápticaRESUMEN
PINK1 and Parkin are established mediators of mitophagy, the selective removal of damaged mitochondria by autophagy. PINK1 and Parkin have been proposed to act as tumor suppressors, as loss-of-function mutations are correlated with enhanced tumorigenesis. However, it is unclear how PINK1 and Parkin act in coordination during mitophagy to influence the cell cycle. Here we show that PINK1 and Parkin genetically interact with proteins involved in cell cycle regulation, and loss of PINK1 and Parkin accelerates cell growth. PINK1- and Parkin-mediated activation of TBK1 at the mitochondria during mitophagy leads to a block in mitosis due to the sequestration of TBK1 from its physiological role at centrosomes during mitosis. Our study supports a diverse role for the far-reaching, regulatory effects of mitochondrial quality control in cellular homeostasis and demonstrates that the PINK1/Parkin pathway genetically interacts with the cell cycle, providing a framework for understanding the molecular basis linking PINK1 and Parkin to mitosis.
Asunto(s)
Ciclo Celular/genética , Mitocondrias/genética , Mitosis/genética , Proteínas Quinasas/genética , Proteínas Serina-Treonina Quinasas/genética , Ubiquitina-Proteína Ligasas/genética , Autofagia/genética , Línea Celular Tumoral , Proliferación Celular/genética , Células HCT116 , Células HEK293 , Células HeLa , Homeostasis/genética , Humanos , Mitofagia/genéticaRESUMEN
Single-cell RNA sequencing (scRNA-seq) is an exciting new technology allowing the analysis of transcriptomes from individual cells, and is ideally suited to address the inherent complexity and dynamics of the central nervous system. scRNA-seq has already been applied to the study of molecular taxonomy of the brain. These works have paved the way to expanding our understanding of the nervous system and provide insights into cellular susceptibilities and molecular mechanisms in neurological and neurodegenerative diseases. We discuss recent progress and challenges in applying this technology to advance our understanding of the brain. We advocate the application of scRNA-seq in the discovery of targets and biomarkers as a new approach in developing novel therapeutics for the treatment of neurodegenerative diseases.
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Secuenciación de Nucleótidos de Alto Rendimiento/métodos , Enfermedades Neurodegenerativas/genética , Enfermedades Neurodegenerativas/metabolismo , Análisis de Secuencia de ARN/métodos , Animales , Biomarcadores/metabolismo , Secuenciación de Nucleótidos de Alto Rendimiento/tendencias , Humanos , Enfermedades Neurodegenerativas/patología , Análisis de Secuencia de ARN/tendenciasRESUMEN
Myosins play essential roles in the development and function of auditory organs and multiple myosin genes are associated with hereditary forms of deafness. Using a forward genetic screen in Drosophila, we identified an E3 ligase, Ubr3, as an essential gene for auditory organ development. Ubr3 negatively regulates the mono-ubiquitination of non-muscle Myosin II, a protein associated with hearing loss in humans. The mono-ubiquitination of Myosin II promotes its physical interaction with Myosin VIIa, a protein responsible for Usher syndrome type IB. We show that ubr3 mutants phenocopy pathogenic variants of Myosin II and that Ubr3 interacts genetically and physically with three Usher syndrome proteins. The interactions between Myosin VIIa and Myosin IIa are conserved in the mammalian cochlea and in human retinal pigment epithelium cells. Our work reveals a novel mechanism that regulates protein complexes affected in two forms of syndromic deafness and suggests a molecular function for Myosin IIa in auditory organs.
Asunto(s)
Cóclea/embriología , Proteínas de Drosophila/metabolismo , Miosinas/metabolismo , Miosina Tipo IIA no Muscular/metabolismo , Ubiquitina-Proteína Ligasas/metabolismo , Animales , Línea Celular , Drosophila , Proteínas de Drosophila/genética , Pruebas Genéticas , Humanos , Miosina VIIa , Ubiquitina-Proteína Ligasas/genéticaRESUMEN
Notch signaling controls a wide range of developmental processes, including proliferation, apoptosis, and cell fate specification during both development and adult tissue homeostasis. The functional versatility of the Notch signaling pathway is tightly linked with the complexity of its regulation in different cellular contexts. To unravel the complexity of Notch signaling, it is important to identify the different components of the Notch signaling pathway. A powerful strategy to accomplish this task is based on genetic screens. Given that the developmental context of signaling is important, these screens should be customized to specific cell populations or tissues. Here, I describe how to perform F1 clonal forward genetic screens in Drosophila to identify novel components of the Notch signaling pathway. These screens combine a classical EMS (ethyl methanesulfonate) chemical mutagenesis protocol along with clonal analysis via FRT-mediated mitotic recombination. These F1 clonal screens allow rapid phenotypic screening within clones of mutant cells induced at specific developmental stages and in tissues of interest, bypassing the pleiotropic effects of isolated mutations. More importantly, since EMS mutations have been notoriously difficult to map to specific genes in the past, I briefly discuss mapping methods that allow rapid identification of the causative mutations.
Asunto(s)
Proteínas de Drosophila/genética , Drosophila/genética , Mutagénesis , Receptores Notch/genética , Transducción de Señal , Animales , Elementos Transponibles de ADN , Drosophila/citología , Mutación , Interferencia de ARNRESUMEN
E proteins are a special class of basic helix-loop-helix (bHLH) proteins that heterodimerize with many bHLH activators to regulate developmental decisions, such as myogenesis and neurogenesis. Daughterless (Da) is the sole E protein in Drosophila and is ubiquitously expressed. We have characterized two transcription activation domains (TADs) in Da, called activation domain 1 (AD1) and loop-helix (LH), and have evaluated their roles in promoting peripheral neurogenesis. In this context, Da heterodimerizes with proneural proteins, such as Scute (Sc), which is dynamically expressed and also contributes a TAD. We found that either one of the Da TADs in the Da/Sc complex is sufficient to promote neurogenesis, whereas the Sc TAD is incapable of doing so. Besides its transcriptional activation role, the Da AD1 domain serves as an interaction platform for E(spl) proteins, bHLH-Orange family repressors which antagonize Da/Sc function. We show that the E(spl) Orange domain is needed for this interaction and strongly contributes to the antiproneural activity of E(spl) proteins. We present a mechanistic model on the interplay of these bHLH factors in the context of neural fate assignment.
Asunto(s)
Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismo , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/metabolismo , Neurogénesis/genética , Proteínas Represoras/metabolismo , Activación Transcripcional , Secuencia de Aminoácidos , Animales , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/genética , Sitios de Unión , Línea Celular , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Drosophila melanogaster/crecimiento & desarrollo , Regulación del Desarrollo de la Expresión Génica , Insectos , Datos de Secuencia Molecular , Plásmidos , Polimerizacion , Unión Proteica , Estructura Secundaria de Proteína , Estructura Terciaria de Proteína , Proteínas Represoras/genética , Transducción de Señal/genética , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , TransfecciónRESUMEN
Notch signaling governs binary cell fate determination in asymmetrically dividing cells. Through a forward genetic screen we identified the fly homologue of Eps15 homology domain containing protein-binding protein 1 (dEHBP1) as a novel regulator of Notch signaling in asymmetrically dividing cells. dEHBP1 is enriched basally and at the actin-rich interface of pII cells of the external mechanosensory organs, where Notch signaling occurs. Loss of function of dEHBP1 leads to up-regulation of Sanpodo, a regulator of Notch signaling, and aberrant trafficking of the Notch ligand, Delta. Furthermore, Sec15 and Rab11, which have been previously shown to regulate the localization of Delta, physically interact with dEHBP1. We propose that dEHBP1 functions as an adaptor molecule for the exocytosis and recycling of Delta, thereby affecting cell fate decisions in asymmetrically dividing cells.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales/fisiología , División Celular Asimétrica/fisiología , Proteínas de Drosophila/fisiología , Drosophila/citología , Exocitosis/fisiología , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Proteínas de la Membrana/metabolismo , Receptores Notch/metabolismo , Proteínas Adaptadoras Transductoras de Señales/genética , Proteínas Adaptadoras Transductoras de Señales/metabolismo , Animales , Drosophila/genética , Drosophila/metabolismo , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Regulación de la Expresión Génica , Proteínas de Microfilamentos/metabolismo , Transducción de Señal , Proteínas de Transporte Vesicular/metabolismo , Proteínas de Unión al GTP rab/metabolismoRESUMEN
Synapses are asymmetric intercellular junctions that mediate neuronal communication. The number, type, and connectivity patterns of synapses determine the formation, maintenance, and function of neural circuitries. The complexity and specificity of synaptogenesis relies upon modulation of adhesive properties, which regulate contact initiation, synapse formation, maturation, and functional plasticity. Disruption of adhesion may result in structural and functional imbalance that may lead to neurodevelopmental diseases, such as autism, or neurodegeneration, such as Alzheimer's disease. Therefore, understanding the roles of different adhesion protein families in synapse formation is crucial for unraveling the biology of neuronal circuit formation, as well as the pathogenesis of some brain disorders. The present review summarizes some of the knowledge that has been acquired in vertebrate and invertebrate genetic model organisms.
Asunto(s)
Adhesión Celular , Sinapsis/fisiología , Vertebrados/fisiología , Animales , Cadherinas/metabolismo , Humanos , Leucina/química , Trastornos Mentales/metabolismo , Modelos Biológicos , Enfermedades Neurodegenerativas/metabolismo , Plasticidad Neuronal/fisiología , Neuronas/metabolismo , Transmisión SinápticaRESUMEN
Active zones are the sites of neurotransmitter release, but their assembly mechanisms are poorly understood. In this issue of Neuron, Graf et al. perform a genetic screen in Drosophila and uncover a novel role for the Rab3 GTPase in organizing the active zone at the neuromuscular junction.
Asunto(s)
Proteínas de Drosophila/metabolismo , GTP Fosfohidrolasas , Terminales Presinápticos/metabolismo , Proteínas de Unión al GTP rab3/metabolismo , Animales , Calcio/metabolismo , Drosophila , GTP Fosfohidrolasas/genética , GTP Fosfohidrolasas/metabolismo , Unión Neuromuscular/genética , Unión Neuromuscular/metabolismo , Unión Neuromuscular/ultraestructura , Terminales Presinápticos/ultraestructura , Transducción de Señal/fisiologíaRESUMEN
The zinc-finger transcription factor Senseless is co-expressed with basic helix-loop-helix (bHLH) proneural proteins in Drosophila sensory organ precursors and is required for their normal development. High levels of Senseless synergize with bHLH proteins and upregulate target gene expression, whereas low levels of Senseless act as a repressor in vivo. However, the molecular mechanism for this dual role is unknown. Here, we show that Senseless binds bHLH proneural proteins via its core zinc fingers and is recruited by proneural proteins to their target enhancers to function as a co-activator. Some point mutations in the Senseless zinc-finger region abolish its DNA-binding ability but partially spare the ability of Senseless to synergize with proneural proteins and to induce sensory organ formation in vivo. Therefore, we propose that the structural basis for the switch between the repressor and co-activator functions of Senseless is the ability of its core zinc fingers to interact physically with both DNA and bHLH proneural proteins. As Senseless zinc fingers are approximately 90% identical to the corresponding zinc fingers of its vertebrate homologue Gfi1, which is thought to cooperate with bHLH proteins in several contexts, the Senseless/bHLH interaction might be evolutionarily conserved.
Asunto(s)
Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismo , Proteínas de Drosophila/metabolismo , Neuronas/metabolismo , Proteínas Nucleares/metabolismo , Proteínas Represoras/metabolismo , Transactivadores/metabolismo , Factores de Transcripción/metabolismo , Secuencia de Aminoácidos , Animales , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/genética , Secuencia Conservada , Drosophila/embriología , Drosophila/genética , Drosophila/metabolismo , Proteínas de Drosophila/química , Proteínas de Drosophila/genética , Embrión no Mamífero , Modelos Biológicos , Datos de Secuencia Molecular , Sistema Nervioso/embriología , Proteínas Nucleares/química , Proteínas Nucleares/genética , Mutación Puntual , Estructura Terciaria de Proteína , Órganos de los Sentidos/embriología , Órganos de los Sentidos/metabolismo , Homología de Secuencia de Aminoácido , Factores de Transcripción/química , Factores de Transcripción/genética , TransgenesRESUMEN
Neurogenesis in all animals is triggered by the activity of a group of basic helix-loop-helix transcription factors, the proneural proteins, whose expression endows ectodermal regions with neural potential. The eventual commitment to a neural precursor fate involves the interplay of these proneural transcriptional activators with a number of other transcription factors that fine tune transcriptional responses at target genes. Most prominent among the factors antagonizing proneural protein activity are the HES basic helix-loop-helix proteins. We have previously shown that two HES proteins of Drosophila, E(spl)mgamma and E(spl)m7, interact with the proneural protein Sc and thereby get recruited onto Sc target genes to repress transcription. Using in vivo and in vitro assays we have now discovered an important dual role for the Sc C-terminal domain. On one hand it acts as a transcription activation domain, and on the other it is used to recruit E(spl) proteins. In vivo, the Sc C-terminal domain is required for E(spl) recruitment in an enhancer context-dependent fashion, suggesting that in some enhancers alternative interaction surfaces can be used to recruit E(spl) proteins.