RESUMEN
Plasticity related gene-1 (PRG-1) is a brain-specific membrane protein related to lipid phosphate phosphatases, which acts in the hippocampus specifically at the excitatory synapse terminating on glutamatergic neurons. Deletion of prg-1 in mice leads to epileptic seizures and augmentation of EPSCs, but not IPSCs. In utero electroporation of PRG-1 into deficient animals revealed that PRG-1 modulates excitation at the synaptic junction. Mutation of the extracellular domain of PRG-1 crucial for its interaction with lysophosphatidic acid (LPA) abolished the ability to prevent hyperexcitability. As LPA application in vitro induced hyperexcitability in wild-type but not in LPA(2) receptor-deficient animals, and uptake of phospholipids is reduced in PRG-1-deficient neurons, we assessed PRG-1/LPA(2) receptor-deficient animals, and found that the pathophysiology observed in the PRG-1-deficient mice was fully reverted. Thus, we propose PRG-1 as an important player in the modulatory control of hippocampal excitability dependent on presynaptic LPA(2) receptor signaling.
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Proteoglicanos/metabolismo , Sinapsis/metabolismo , Proteínas de Transporte Vesicular/metabolismo , Animales , Electroencefalografía , Hipocampo/química , Hipocampo/citología , Hipocampo/metabolismo , Lisofosfolípidos/metabolismo , Ratones , Ratones Noqueados , Proteoglicanos/análisis , Proteoglicanos/genética , Receptores AMPA/metabolismo , Receptores del Ácido Lisofosfatídico/metabolismo , Transducción de Señal , Proteínas de Transporte Vesicular/análisis , Proteínas de Transporte Vesicular/genéticaRESUMEN
BACKGROUND: Plasticity-related genes (Prgs/PRGs) or lipid phosphate phosphatase-related proteins (LPPRs) comprise five known members, which have been linked to neuronal differentiation processes, such as neurite outgrowth, axonal branching, or dendritic spine formation. PRGs are highly brain-specific and belong to the lipid phosphate phosphatases (LPPs) superfamily, which influence lipid metabolism by dephosphorylation of bioactive lipids. PRGs, however, do not possess enzymatic activity, but modify lipid metabolism in a way that is still under investigation. RESULTS: We analyzed mRNA expression levels of all Prgs during mouse brain development, in the hippocampus, neocortex, olfactory bulbs, and cerebellum. We found different spatio-temporal expression patterns for each of the Prgs, and identified a high expression of the uncharacterized Prg4 throughout brain development. Unlike its close family members PRG3 and PRG5, PRG4 did not induce filopodial outgrowth in non-neuronal cell lines, and does not localize to the plasma membrane of filopodia. CONCLUSION: We showed PRG4 to be highly expressed in the developing and the adult brain, suggesting that it is of vital importance for normal brain function. Despite its similarities to other family members, it seems not to be involved in changes of cell morphology; instead, it is more likely to be associated with intracellular signaling.
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Encéfalo , Monoéster Fosfórico Hidrolasas , Animales , Encéfalo/metabolismo , Membrana Celular/metabolismo , Hipocampo/metabolismo , Ratones , Monoéster Fosfórico Hidrolasas/genética , Monoéster Fosfórico Hidrolasas/metabolismo , Proteoglicanos/metabolismo , SeudópodosRESUMEN
Loss of active synapses and alterations in membrane lipids are crucial events in physiological aging as well as in neurodegenerative disorders. Both are related to the abnormal aggregation of amyloid-beta (Aß) species, generally known as amyloidosis. There are two major known human Aß species: Aß(1-40) and Aß(1-42). However, which of these species have more influence on active synapses and membrane lipids is still poorly understood. Additionally, the time-dependent effect of Aß species on alterations in membrane lipids of hippocampal neurones and glial cells remains unknown. Therefore, our study contributes to a better understanding of the role of Aß species in the loss of active synapses and the dysregulation of membrane lipids in vitro. We showed that Aß(1-40) or Aß(1-42) treatment influences membrane lipids before synaptic loss appears and that the loss of active synapses is not dependent on the Aß species. Our lipidomic data analysis showed early changes in specific lipid classes such as sphingolipid and glycerophospholipid neurones. Our results underscore the potential role of lipids as a possible early diagnostic biomarker in amyloidosis-related disorders.
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Péptidos beta-Amiloides/metabolismo , Lípidos de la Membrana/metabolismo , Sinapsis/metabolismo , Enfermedad de Alzheimer/metabolismo , Animales , Células Cultivadas , Hipocampo/metabolismo , Ratones , Ratones Endogámicos C57BL , Neuronas/metabolismoRESUMEN
Basophils are key effector cells in atopic diseases, and the signaling sphingolipid Sphigosine-1-phosphate (S1P) is emerging as an important mediator in these conditions. The possible interaction of S1P and basophils and the resulting biological effects have not yet been studied. We hypothesize that S1P influences the function of basophils in atopy and aim to elucidate the modes of interaction. S1P receptor (S1PR) expression in human peripheral blood basophils from atopic and non-atopic patients was assessed through qRT-PCR and flow cytometry analysis. Functional effects of S1P were assessed through a basophil activation test (BAT), calcium flux, apoptosis, and chemotaxis assays. Immunofluorescence staining was performed to visualize intracellular S1P. Human basophils express S1PR1, S1PR2, S1PR3, and S1PR4 on the mRNA level. 0.1 µM S1P have anti-apoptotic, while 10 µM exhibits apoptotic effects on basophils. Basophils from atopic patients show less chemotactic activity in response to S1P than those from healthy donors. Protein expression of S1PR1 is downregulated in atopic patients, and basophils in lesional AD skin possess intracellular S1P. These findings suggest that the interaction of S1P and basophils might be an important factor in the pathophysiology of atopy.
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Basófilos , Receptores de Lisoesfingolípidos , Humanos , Receptores de Lisoesfingolípidos/genética , Receptores de Lisoesfingolípidos/metabolismo , Receptores de Esfingosina-1-Fosfato/metabolismo , Regulación hacia Arriba , Basófilos/metabolismo , Esfingosina/metabolismo , Lisofosfolípidos/metabolismoRESUMEN
The functional importance of neuronal differentiation of the transmembrane proteins' plasticity-related genes 3 (PRG3) and 5 (PRG5) has been shown. Although their sequence is closely related, they promote different morphological changes in neurons. PRG3 was shown to promote neuritogenesis in primary neurons; PRG5 contributes to spine induction in immature neurons and the regulation of spine density and morphology in mature neurons. Both exhibit intracellularly located C-termini of less than 50 amino acids. Varying C-termini suggested that these domains shape neuronal morphology differently. We generated mutant EGFP-fusion proteins in which the C-termini were either swapped between PRG3 and PRG5, deleted, or fused to another family member, plasticity-related gene 4 (PRG4), that was recently shown to be expressed in different brain regions. We subsequently analyzed the influence of overexpression in immature neurons. Our results point to a critical role of the PRG3 and PRG5 C-termini in shaping early neuronal morphology. However, the results suggest that the C-terminus alone might not be sufficient for promoting the morphological effects induced by PRG3 and PRG5.
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Encéfalo , Neuronas , Neuronas/metabolismo , Encéfalo/metabolismo , Hipocampo/metabolismoRESUMEN
Niemann-Pick type C1 (NPC1) disease is characterized by neurodegeneration caused by cholesterol accumulation in the late endosome/lysosome. In this study, a defective basal and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-stimulated internalization of GluR2-containing AMPA receptors in NPC1-/- cortical neurons was detected. Our results show that the amount of cholesterol and group I metabotropic glutamate receptors (mGluR1/5) in lipid rafts of NPC1-/- cortical tissue and neurons are decreased and their downstream signals of p-ERK are defective, which are restored by a rebalance of cholesterol homeostasis through ß-cyclodextrin (ß-CD) treatment. Application of 3,5-dihydroxyphenylglycine (DHPG)-a mGluR1/5 agonist-and ß-CD markedly increases the internalization of AMPA receptors and decreases over-influx of calcium in NPC1-/- neurons, respectively. Furthermore, the defective phosphorylated GluR2 and protein kinase C signals are ameliorated by the treatment with DHPG and ß-CD, respectively, suggesting an involvement of them in internalization dysfunction. Taken together, our data imply that abnormal internalization of AMPA receptors is a critical mechanism for neuronal dysfunction and the correction of dysfunctional mGluR1/5 is a potential therapeutic strategy for NPC1 disease.
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Péptidos y Proteínas de Señalización Intracelular/genética , Receptores AMPA/metabolismo , Receptores de Ácido Kaínico/metabolismo , Receptores de Glutamato Metabotrópico/metabolismo , Animales , Calcio/metabolismo , Células Cultivadas , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Ratones Transgénicos , Neuronas/fisiología , Proteína Niemann-Pick C1RESUMEN
The lysosomal storage disorder Fabry disease is characterized by a deficiency of the lysosomal enzyme α-Galactosidase A. The observation that missense variants in the encoding GLA gene often lead to structural destabilization, endoplasmic reticulum retention and proteasomal degradation of the misfolded, but otherwise catalytically functional enzyme has resulted in the exploration of alternative therapeutic approaches. In this context, we have investigated proteostasis regulators (PRs) for their potential to increase cellular enzyme activity, and to reduce the disease-specific accumulation of the biomarker globotriaosylsphingosine in patient-derived cell culture. The PRs also acted synergistically with the clinically approved 1-deoxygalactonojirimycine, demonstrating the potential of combination treatment in a therapeutic application. Extensive characterization of the effective PRs revealed inhibition of the proteasome and elevation of GLA gene expression as paramount effects. Further analysis of transcriptional patterns of the PRs exposed a variety of genes involved in proteostasis as potential modulators. We propose that addressing proteostasis is an effective approach to discover new therapeutic targets for diseases involving folding and trafficking-deficient protein mutants.
Asunto(s)
Enfermedad de Fabry/genética , Enfermedades por Almacenamiento Lisosomal/genética , Proteostasis/genética , alfa-Galactosidasa/genética , 1-Desoxinojirimicina/análogos & derivados , 1-Desoxinojirimicina/uso terapéutico , Biomarcadores/metabolismo , Retículo Endoplásmico/genética , Retículo Endoplásmico/metabolismo , Enfermedad de Fabry/tratamiento farmacológico , Enfermedad de Fabry/enzimología , Enfermedad de Fabry/patología , Fibroblastos/efectos de los fármacos , Fibroblastos/metabolismo , Regulación Enzimológica de la Expresión Génica/efectos de los fármacos , Humanos , Enfermedades por Almacenamiento Lisosomal/tratamiento farmacológico , Enfermedades por Almacenamiento Lisosomal/enzimología , Enfermedades por Almacenamiento Lisosomal/patología , Lisosomas/enzimología , Lisosomas/genética , Lisosomas/metabolismo , Mutación Missense/genética , Complejo de la Endopetidasa Proteasomal/genética , Complejo de la Endopetidasa Proteasomal/metabolismo , Transporte de Proteínas/efectos de los fármacos , Esfingosina/análogos & derivados , Esfingosina/metabolismoRESUMEN
BACKGROUND: Interferon-γ (IFN-γ, a type II IFN) is present in the central nervous system (CNS) under various conditions. Evidence is emerging that, in addition to its immunological role, IFN-γ modulates neuronal morphology, function, and development in several brain regions. Previously, we have shown that raising levels of IFN-ß (a type I IFN) lead to increased neuronal excitability of neocortical layer 5 pyramidal neurons. Because of shared non-canonical signaling pathways of both cytokines, we hypothesized a similar neocortical role of acutely applied IFN-γ. METHODS: We used semi-quantitative RT-PCR, immunoblotting, and immunohistochemistry to analyze neuronal expression of IFN-γ receptors and performed whole-cell patch-clamp recordings in layer 5 pyramidal neurons to investigate sub- and suprathreshold excitability, properties of hyperpolarization-activated cyclic nucleotide-gated current (Ih), and inhibitory neurotransmission under the influence of acutely applied IFN-γ. RESULTS: We show that IFN-γ receptors are present in the membrane of rat's neocortical layer 5 pyramidal neurons. As expected from this and the putative overlap in IFN type I and II alternative signaling pathways, IFN-γ diminished Ih, mirroring the effect of type I IFNs, suggesting a likewise activation of protein kinase C (PKC). In contrast, IFN-γ did neither alter subthreshold nor suprathreshold neuronal excitability, pointing to augmented inhibitory transmission by IFN-γ. Indeed, IFN-γ increased electrically evoked inhibitory postsynaptic currents (IPSCs) on neocortical layer 5 pyramidal neurons. Furthermore, amplitudes of spontaneous IPSCs and miniature IPSCs were elevated by IFN-γ, whereas their frequency remained unchanged. CONCLUSIONS: The expression of IFN-γ receptors on layer 5 neocortical pyramidal neurons together with the acute augmentation of inhibition in the neocortex by direct application of IFN-γ highlights an additional interaction between the CNS and immune system. Our results strengthen our understanding of the role of IFN-γ in neocortical neurotransmission and emphasize its impact beyond its immunological properties, particularly in the pathogenesis of neuropsychiatric disorders.
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Interferón gamma/metabolismo , Neocórtex/metabolismo , Neuroinmunomodulación/fisiología , Células Piramidales/metabolismo , Receptores de Interferón/metabolismo , Animales , Interferón gamma/farmacología , Masculino , Neocórtex/efectos de los fármacos , Neocórtex/inmunología , Células Piramidales/efectos de los fármacos , Células Piramidales/inmunología , Ratas , Ratas WistarRESUMEN
BACKGROUND: LPA is a small bioactive phospholipid that acts as an extracellular signaling molecule and is involved in cellular processes, including cell proliferation, migration, and differentiation. LPA acts by binding and activating at least six known G protein-coupled receptors: LPA1-6 . In recent years, LPA has been suggested to play an important role both in normal neuronal development and under pathological conditions in the nervous system. RESULTS: We show the expression pattern of LPA receptors during mouse brain development by using qRT-PCR, in situ hybridization, and immunocytochemistry. Only LPA 1 , LPA 2, LPA 4, and LPA 6 mRNA transcripts were detected throughout development stages from embryonic day 16 until postnatal day 30 of hippocampus, neocortex, cerebellum, and bulbus olfactorius in our experiments, while expression of LPA 3 and LPA 5 genes was below detection level. In addition to our qRT-PCR results, we also analyzed the cellular protein expression of endogenous LPA receptors, with focus on LPA1 and LPA2 within postnatal brain slices and primary neuron differentiation with and without cytoskeleton stabilization and destabilization. CONCLUSIONS: The expression of LPA receptors changes depends on the developmental stage in mouse brain and in cultured hippocampal primary neurons. Interestingly, we found that commercially available antibodies for LPA receptors are largely unspecific.
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Encéfalo/crecimiento & desarrollo , Receptores del Ácido Lisofosfatídico/metabolismo , Animales , Encéfalo/metabolismo , Células Cultivadas , Hipocampo/citología , Ratones , Neuronas/citología , ARN Mensajero/análisis , Receptores del Ácido Lisofosfatídico/genéticaRESUMEN
BACKGROUND: Niemann-Pick disease type C1 (NPC1) is an autosomal-recessive lipid-storage disorder with an estimated minimal incidence of 1/120,000 live births. Besides other neuronal and visceral symptoms, NPC1 patients develop spleen dysfunction, isolated spleno- or hepatosplenomegaly and infections. The mechanisms of splenomegaly and alterations of lipid metabolism-related genes in NPC1 disease are still poorly understood. METHODS: Here, we used an NPC1 mouse model to study a splenoprotective effect of a treatment with miglustat, 2-hydroxypropyl-ß-cyclodextrin and allopregnanolone and showed that this treatment has a positive effect on spleen morphology and lipid metabolism. RESULTS: Disease progress can be halted and blocked at the molecular level. Mutant Npc1 (Npc1-/-) mice showed increased spleen weight and increased lipid accumulation that could be avoided by our treatment. Also, FACS analyses showed that the increased number of splenic myeloid cells in Npc1-/- mice was normalized by the treatment. Treated Npc1-/- mice showed decreased numbers of cytotoxic T cells and increased numbers of T helper cells. CONCLUSIONS: In summary, the treatment promotes normal spleen morphology, stabilization of lipid homeostasis and blocking of inflammation, but alters the composition of T cell subtypes.
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1-Desoxinojirimicina/análogos & derivados , 2-Hidroxipropil-beta-Ciclodextrina/uso terapéutico , Pregnanolona/uso terapéutico , Bazo/metabolismo , 1-Desoxinojirimicina/uso terapéutico , Animales , Separación Celular , Modelos Animales de Enfermedad , Citometría de Flujo , Genotipo , Metabolismo de los Lípidos/efectos de los fármacos , Ratones , Enfermedad de Niemann-Pick Tipo C , Bazo/efectos de los fármacosRESUMEN
Rare diseases are a heterogeneous group of very different clinical syndromes. Their most common causes are defects in the hereditary material, and they can therefore be passed on to descendants. Rare diseases become manifest in almost all organs and often have a systemic expressivity, i.e., they affect several organs simultaneously. An effective causal therapy is often not available and can only be developed when the underlying causes of the disease are understood. In this review, we focus on Niemann-Pick disease type C1 (NPC1), which is a rare lipid-storage disorder. Lipids, in particular phospholipids, are a major component of the cell membrane and play important roles in cellular functions, such as extracellular receptor signaling, intracellular second messengers and cellular pressure regulation. An excessive storage of fats, as seen in NPC1, can cause permanent damage to cells and tissues in the brain and peripheral nervous system, but also in other parts of the body. Here, we summarize the impact of NPC1 pathology on several organ systems, as revealed in experimental animal models and humans, and give an overview of current available treatment options.
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Enfermedad de Niemann-Pick Tipo C/etiología , Enfermedad de Niemann-Pick Tipo C/metabolismo , Animales , Transporte Biológico , Modelos Animales de Enfermedad , Susceptibilidad a Enfermedades , Humanos , Metabolismo de los Lípidos , Ratones , Enfermedad de Niemann-Pick Tipo C/diagnóstico , Enfermedad de Niemann-Pick Tipo C/terapia , Especificidad de ÓrganosRESUMEN
Glucosylceramide and glucosylsphingosine are the two major storage products in Gaucher disease (GD), an inherited metabolic disorder caused by a deficiency of the lysosomal enzyme glucocerebrosidase. The build-up of glucosylceramide in the endoplasmic reticulum and prominent accumulation in cell lysosomes of tissue macrophages results in decreased blood cell and platelet counts, and skeletal abnormalities. The pathological role of the deacylated form of glucosylceramide, glucosylsphingosine (lyso-Gb1), a recently identified sensitive and specific biomarker for GD, is not well investigated. We established a long-term infusion model in C57BL/6JRj mice to examine the effect of lyso-Gb1 on representative hallmark parameters of GD. Mice received lyso-Gb1 at a dosage of 10 mg·kg-1 per day as a continuous subcutaneous administration, and were routinely checked for blood lyso-Gb1 levels using liquid chromatography-multiple reaction monitoring mass spectrometry (LC/MRM-MS) measurements at four-weekly intervals throughout treatment. The C57BL/6JRj mice showed a stable increase of lyso-Gb1 up to->500-fold greater than the normal reflecting concentrations seen in moderately to severely affected patients. Furthermore, lyso-Gb1 accumulated in peripheral tissues. The mice developed hematological symptoms such as reduced hemoglobin and hematocrit, increased spleen weights and a slight inflammatory tissue response after eight weeks of treatment. The above findings indicate a measurable visceral and hematological response in treated mice that suggests a role for lyso-Gb1 in the development of peripheral signs of GD.
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Enfermedad de Gaucher/inducido químicamente , Enfermedad de Gaucher/patología , Psicosina/análogos & derivados , Vísceras/química , Animales , Cromatografía Liquida , Modelos Animales de Enfermedad , Enfermedad de Gaucher/sangre , Hematócrito , Hemoglobinas/análisis , Humanos , Hígado/química , Hígado/efectos de los fármacos , Espectrometría de Masas , Ratones , Ratones Endogámicos C57BL , Tamaño de los Órganos , Psicosina/efectos adversos , Psicosina/sangre , Bazo/química , Bazo/efectos de los fármacos , Vísceras/efectos de los fármacosRESUMEN
The Yin-Yang 2 (YY2) protein is the most recently described member of the family of YY transcription factors. Despite its high structural and functional homology with the well-characterized YY1, less is known about its role in biological processes. In previous studies, we have found differential yy2 mRNA expression levels in various cell types of the murine brain. To investigate the functional implication of yy2 in neurons, we have examined the influence of altered cellular yy2 concentrations during neuronal differentiation. Our results indicate that both the up- and down-regulation of yy2 significantly impairs the outgrowth of the major neurite of primary hippocampal neurons and the numbers of neuronal processes in proximate extensions. Moreover, enhanced expression of wild-type yy2 results in increased cell death, whereas elevated expression levels of a yy2 DNA-binding mutant have no effect on cell viability. Therefore, stringent regulation of the cellular yy2 content might be needed to ensure proper neurite outgrowth and cell vitality.
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Neuritas/metabolismo , Factores de Transcripción/metabolismo , Animales , Regulación hacia Abajo , Femenino , Ratones , Ratones Endogámicos C57BL , Embarazo , Regiones Promotoras Genéticas/genéticaRESUMEN
Central nervous system (CNS) inflammation involves the generation of inducible cytokines such as interferons (IFNs) and alterations in brain activity, yet the interplay of both is not well understood. Here, we show that in vivo elevation of IFNs by viral brain infection reduced hyperpolarization-activated currents (Ih) in cortical pyramidal neurons. In rodent brain slices directly exposed to type I IFNs, the hyperpolarization-activated cyclic nucleotide (HCN)-gated channel subunit HCN1 was specifically affected. The effect required an intact type I receptor (IFNAR) signaling cascade. Consistent with Ih inhibition, IFNs hyperpolarized the resting membrane potential, shifted the resonance frequency, and increased the membrane impedance. In vivo application of IFN-ß to the rat and to the mouse cerebral cortex reduced the power of higher frequencies in the cortical electroencephalographic activity only in the presence of HCN1. In summary, these findings identify HCN1 channels as a novel neural target for type I IFNs providing the possibility to tune neural responses during the complex event of a CNS inflammation.
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Corteza Cerebral/fisiología , Canales Regulados por Nucleótidos Cíclicos Activados por Hiperpolarización/fisiología , Interferón Tipo I/fisiología , Neuronas/fisiología , Canales de Potasio/fisiología , Animales , Western Blotting , Corteza Cerebral/citología , Simulación por Computador , Citocinas/fisiología , Electroencefalografía , Fenómenos Electrofisiológicos/fisiología , Células HEK293 , Humanos , Inmunohistoquímica , Interferón Tipo I/biosíntesis , Interferón beta/farmacología , Masculino , Ratones Endogámicos C57BL , Neocórtex/citología , Neocórtex/metabolismo , Neocórtex/fisiología , Red Nerviosa/citología , Red Nerviosa/fisiología , Técnicas de Placa-Clamp , Ratas , Reacción en Cadena en Tiempo Real de la Polimerasa , Receptores de Interferón/fisiología , Transducción de Señal/fisiología , TransfecciónRESUMEN
Plasticity-related genes (PRGs, Lipid phosphate phosphatase-related proteins LPPRs) are a defined as a subclass of the lipid phosphate phosphatase (LPP) superfamily, comprising so far five brain- and vertebrate-specific membrane-spanning proteins. LPPs interfere with lipid phosphate signaling and are thereby involved in mediating the extracellular concentration and signal transduction of lipid phosphate esters such as lysophosphatidate (LPA) and spingosine-1 phosphate (S1P). LPPs dephosphorylate their substrates through extracellular catalytic domains, thus making them ecto-phosphatases. PRGs/LPPRs are structurally similar to the other LPP family members in general. They are predominantly expressed in the CNS in a subtype specific pattern rather than having a wide tissue distribution. In contrast to LPPs, PRGs/LPPRs may act by modifying bioactive lipids and their signaling pathways, rather than possessing an ecto-phosphatase activity. However, the exact functional roles of PRGs/LPPRs have just begun to be explored. Here, we discuss new findings on the neuron-specific transcriptional regulation of PRG1/LPPR4 and new insights into protein-protein interaction and signaling pathway regulation. Further, we start to shed light on the subcellular localization and the resulting functional modulatory influence of PRG1/LPPR4 expression in excitatory synaptic transmission to the established neural effects such as promotion of filopodia formation, neurite extension, axonal sprouting and reorganization after lesion. This range of effects suggests an involvement in the pathogenesis and/or reparation attempts in disease. Therefore, we summarize available data on the association of PRGs/LPPRs with several neurological and other diseases in humans and experimental animals. Finally we highlight important open questions and emerging future directions of research. This article is part of a Special Issue entitled Advances in Lysophospholipid Research.
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Encéfalo/metabolismo , Proteínas del Tejido Nervioso/genética , Plasticidad Neuronal/genética , Monoéster Fosfórico Hidrolasas/genética , Animales , Encéfalo/patología , Humanos , Neoplasias/genética , Neoplasias/patología , Proteínas del Tejido Nervioso/metabolismo , Enfermedades del Sistema Nervioso/genética , Enfermedades del Sistema Nervioso/patología , Enfermedades del Sistema Nervioso/fisiopatología , Monoéster Fosfórico Hidrolasas/metabolismoRESUMEN
The development of the central nervous system is highly complex, involving numerous developmental processes that must take place with high spatial and temporal precision. This requires a series of complex and well-coordinated molecular processes that are tighly controlled and regulated by, for example, a variety of proteins and lipids. Deregulations in these processes, including genetic mutations, can lead to the most severe maldevelopments. The present review provides an overview of the protein family Plasticity-related genes (PRG1-5), including their role during neuronal differentiation, their molecular interactions, and their participation in various diseases. As these proteins can modulate the function of bioactive lipids, they are able to influence various cellular processes. Furthermore, they are dynamically regulated during development, thus playing an important role in the development and function of synapses. First studies, conducted not only in mouse experiments but also in humans, revealed that mutations or dysregulations of these proteins lead to changes in lipid metabolism, resulting in severe neurological deficits. In recent years, as more and more studies have shown their involvement in a broad range of diseases, the complexity and broad spectrum of known and as yet unknown interactions between PRGs, lipids, and proteins make them a promising and interesting group of potential novel therapeutic targets.
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Plasticidad Neuronal , Humanos , Animales , Plasticidad Neuronal/genética , Metabolismo de los Lípidos/genéticaRESUMEN
BACKGROUND: Recently, we and others proposed plasticity-related gene 3 (PRG3) as a novel molecule in neuritogenesis based on PRG3 overexpression experiments in neuronal and non-neuronal cell lines. However, direct information on PRG3 effects in neuronal development and, in particular, its putative spatio-temporal distribution and conditions of action, is sparse. RESULTS: We demonstrate here that PRG3 induces filopodia formation in HEK293 cells depending on its N-glycosylation status. The PRG3 protein was strongly expressed during mouse brain development in vivo from embryonic day 16 to postnatal day 5 (E16 - P5). From P5 on, expression declined. Furthermore, in early, not yet polarized hippocampal cultured neurons, PRG3 was expressed along the neurite shaft. Knock-down of PRG3 in these neurons led to a decreased number of neurites. This phenotype is rescued by expression of an shRNA-resistant PRG3 construct in PRG3 knock-down neurons. After polarization, endogenous PRG3 expression shifted mainly to axons, specifically to the plasma membrane along the neurite shaft. These PRG3 pattern changes appeared temporally and spatially related to ongoing synaptogenesis. Therefore we tested (i) whether dendritic PRG3 re-enhancement influences synaptic currents and (ii) whether synaptic inputs contribute to the PRG3 shift. Our results rendered both scenarios unlikely: (i) PRG3 over-expression had no influence on miniature excitatory postsynaptic currents (mEPSC) and (ii) blocking of incoming signals did not alter PRG3 distribution dynamics. In addition, PRG3 levels did not interfere with intrinsic neuronal properties. CONCLUSION: Taken together, our data indicate that endogenous PRG3 promotes neurite shaft protrusion and therefore contributes to regulating filopodia formation in immature neurons. PRG3 expression in more mature neurons, however, is predominantly localized in the axon. Changes in PRG3 levels did not influence intrinsic or synaptic neuronal properties.
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Regulación del Desarrollo de la Expresión Génica/genética , Neuritas/metabolismo , Neuronas/citología , Análisis de Varianza , Animales , Animales Recién Nacidos , Asparagina/genética , Asparagina/metabolismo , Células Cultivadas , Proteína Mayor Básica del Eosinófilo/genética , Potenciales Postsinápticos Excitadores/genética , Femenino , Glicosilación , Proteínas Fluorescentes Verdes/genética , Células HEK293 , Hipocampo/citología , Humanos , Masculino , Potenciales de la Membrana/genética , Ratones , Ratones Endogámicos C57BL , Neuroglía/citología , Técnicas de Placa-Clamp , Mutación Puntual/genética , Embarazo , Estructura Terciaria de Proteína/genética , Estructura Terciaria de Proteína/fisiología , Seudópodos/genética , ARN Interferente Pequeño/genética , ARN Interferente Pequeño/metabolismo , TransfecciónRESUMEN
During development, axonal projections have a remarkable ability to innervate correct dendritic subcompartments of their target neurons and to form regular neuronal circuits. Altered axonal targeting with formation of synapses on inappropriate neurons may result in neurodevelopmental sequelae, leading to psychiatric disorders. Here we show that altering the expression level of the polysialic acid moiety, which is a developmentally regulated, posttranslational modification of the neural cell adhesion molecule NCAM, critically affects correct circuit formation. Using a chemically modified sialic acid precursor (N-propyl-D: -mannosamine), we inhibited the polysialyltransferase ST8SiaII, the principal enzyme involved in polysialylation during development, at selected developmental time-points. This treatment altered NCAM polysialylation while NCAM expression was not affected. Altered polysialylation resulted in an aberrant mossy fiber projection that formed glutamatergic terminals on pyramidal neurons of the CA1 region in organotypic slice cultures and in vivo. Electrophysiological recordings revealed that the ectopic terminals on CA1 pyramids were functional and displayed characteristics of mossy fiber synapses. Moreover, ultrastructural examination indicated a "mossy fiber synapse"-like morphology. We thus conclude that homeostatic regulation of the amount of synthesized polysialic acid at specific developmental stages is essential for correct synaptic targeting and circuit formation during hippocampal development.
Asunto(s)
Homeostasis , Moléculas de Adhesión de Célula Nerviosa/metabolismo , Ácidos Siálicos/metabolismo , Sinapsis/metabolismo , Animales , Ratones , Ratones Endogámicos C57BLRESUMEN
The retinal degeneration protein RD3 is involved in regulatory processes of photoreceptor cells. Among its main functions is the inhibition of photoreceptor specific membrane guanylate cyclases during trafficking from the inner segment to their final destination in the outer segment. However, any physiological role of RD3 in non-retinal tissue is unsolved at present and specific protein targets outside of retinal tissue have not been identified so far. The family of membrane bound guanylate cyclases share a high homology of their amino acid sequences in their cytoplasmic domains. Therefore, we reasoned that membrane guanylate cyclases that are activated by natriuretic peptides are also regulated by RD3. We analyzed transcript levels of the rd3 gene and natriuretic peptide receptor genes Npr1 and Npr2 in the mouse retina, cerebellum, hippocampus, neocortex, and the olfactory bulb during development from the embryonic to the postnatal stage at P60. The rd3 gene showed a lower expression level than Npr1 and Npr2 (encoding for GC-A and GC-B, respectively) in all tested brain tissues, but was at least one order of magnitude higher in the retina. RD3 and natriuretic peptide receptor GCs co-express in the retina and brain tissue leading to functional tests. We expressed GC-A and GC-B in HEK293T cells and measured the inhibition of GCs by RD3 after activation by natriuretic peptides yielding inhibitory constants around 25 nM. Furthermore, endogenous GCs in astrocytes were inhibited by RD3 to a similar extent. We here show for the first time that RD3 can inhibit two hormone-stimulated GCs, namely GC-A and GC-B indicating a new regulatory feature of these hormone receptors.