Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 27
Filter
Add more filters










Publication year range
1.
Front Pharmacol ; 13: 750554, 2022.
Article in English | MEDLINE | ID: mdl-35444539

ABSTRACT

Network communication in the CNS relies upon multiple neuronal and glial signaling pathways. In addition to synaptic transmission, other organelles such as mitochondria play roles in cellular signaling. One highly conserved mitochondrial signaling mechanism involves the 18 kDa translocator protein (TSPO) of the outer mitochondrial membrane. Originally, TSPO was identified as a binding site for benzodiazepines in the periphery. It was later discovered that TSPO is found in mitochondria, including in CNS cells. TSPO is implicated in multiple cellular processes, including the translocation of cholesterol and steroidogenesis, porphyrin transport, cellular responses to stress, inflammation, and tumor progression. Yet the impacts of modulating TSPO signaling on network activity and behavioral performance have not been characterized. In the present study, we assessed the effects of TSPO modulators PK11195, Ro5-4864, and XBD-173 via electroencephalography (EEG) and the open field test (OFT) at low to moderate doses. Cortical EEG recordings revealed increased power in the δ and θ frequency bands after administration of each of the three modulators, as well as compound- and dose-specific changes in α and γ. Behaviorally, these compounds reduced locomotor activity in the OFT in a dose-dependent manner, with XBD-173 having the subtlest behavioral effects while still strongly modulating the EEG. These findings indicate that TSPO modulators, despite their diversity, exert similar effects on the EEG while displaying a range of sedative/hypnotic effects at moderate to high doses. These findings bring us one step closer to understanding the functions of TSPO in the brain and as a target in CNS disease.

2.
Mol Psychiatry ; 27(3): 1729-1741, 2022 03.
Article in English | MEDLINE | ID: mdl-35169261

ABSTRACT

Intellectual disability (ID) is a common neurodevelopmental disorder that can arise from genetic mutations ranging from trisomy to single nucleotide polymorphism. Mutations in a growing number of single genes have been identified as causative in ID, including ARHGEF9. Evaluation of 41 ARHGEF9 patient reports shows ubiquitous inclusion of ID, along with other frequently reported symptoms of epilepsy, abnormal baseline EEG activity, behavioral symptoms, and sleep disturbances. ARHGEF9 codes for the Cdc42 Guanine Nucleotide Exchange Factor 9 collybistin (Cb), a known regulator of inhibitory synapse function via direct interaction with the adhesion molecule neuroligin-2 and the α2 subunit of GABAA receptors. We mutate the Cb binding motif within the large intracellular loop of α2 replacing it with the binding motif for gephyrin from the α1 subunit (Gabra2-1). The Gabra2-1 mutation causes a strong downregulation of Cb expression, particularly at cholecystokinin basket cell inhibitory synapses. Gabra2-1 mice have deficits in working and recognition memory, as well as hyperactivity, anxiety, and reduced social preference, recapitulating the frequently reported features of ARHGEF9 patients. Gabra2-1 mice also have spontaneous seizures during postnatal development which can lead to mortality, and baseline abnormalities in low-frequency wavelengths of the EEG. EEG abnormalities are vigilance state-specific and manifest as sleep disturbance including increased time in wake and a loss of free-running rhythmicity in the absence of light as zeitgeber. Gabra2-1 mice phenocopy multiple features of human ARHGEF9 mutation, and reveal α2 subunit-containing GABAA receptors as a druggable target for treatment of this complex ID syndrome.


Subject(s)
Intellectual Disability , Mutation , Receptors, GABA-A , Rho Guanine Nucleotide Exchange Factors , Animals , Humans , Intellectual Disability/genetics , Mice , Receptors, GABA-A/genetics , Receptors, GABA-A/metabolism , Rho Guanine Nucleotide Exchange Factors/genetics , Rho Guanine Nucleotide Exchange Factors/metabolism , Syndrome , gamma-Aminobutyric Acid/genetics , gamma-Aminobutyric Acid/metabolism
3.
Int J Mol Sci ; 22(8)2021 Apr 08.
Article in English | MEDLINE | ID: mdl-33917718

ABSTRACT

BACKGROUND: Brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) play a critical role in neurodevelopment, where breast milk is a significant dietary source. The impact of previous COVID-19 infection and mastitis on the concentration of BDNF and NGF in human milk was investigated. METHODS: Concentrations of BDNF and NGF were measured via ELISA in human milk samples collected from 12 mothers with a confirmed COVID-19 PCR, 13 mothers with viral symptoms suggestive of COVID-19, and 22 unexposed mothers (pre-pandemic Ctl-2018). These neurotrophins were also determined in 12 mothers with previous mastitis and 18 mothers without mastitis. RESULTS: The NGF concentration in human milk was lower in the COVID-19 PCR and viral symptoms groups than in the unexposed group, but BDNF did not differ significantly. Within the COVID-19 group, BDNF was higher in mothers who reported headaches or loss of smell/taste when compared with mothers without the respective symptom. BDNF was lower in mothers with mastitis than in mothers without mastitis. CONCLUSIONS: Previous COVID-19 and mastitis infections changed differently the secretion of NGF and BDNF in human milk. Whether the changes in NGF and BDNF levels in milk from mothers with infection influence their infant's development remains to be investigated.


Subject(s)
Brain-Derived Neurotrophic Factor/metabolism , COVID-19/metabolism , Mastitis/metabolism , Milk, Human/chemistry , Nerve Growth Factor/metabolism , Adult , Bodily Secretions/chemistry , Brain-Derived Neurotrophic Factor/analysis , COVID-19/complications , Female , Humans , Mastitis/complications , Mothers , Nerve Growth Factor/analysis
4.
Sci Rep ; 11(1): 1925, 2021 01 21.
Article in English | MEDLINE | ID: mdl-33479368

ABSTRACT

Perception, emotion, and mood are powerfully modulated by serotonin receptor (5-HTR) agonists including hallucinogens. The 5-HT2AR subtype has been shown to be central to hallucinogen action, yet the precise mechanisms mediating the response to 5-HT2AR activation remain unclear. Hallucinogens induce the head twitch response (HTR) in rodents, which is the most commonly used behavioral readout of hallucinogen pharmacology. While the HTR provides a key behavioral signature, less is known about the meso level changes that are induced by 5-HT2AR activation. In response to administration of the potent and highly selective 5-HT2AR agonist 25I-NBOH in mice, we observe a disorganization of behavior which includes frequent episodes of behavioral arrest that consistently precede the HTR by a precise interval. By combining behavioral analysis with electroencephalogram (EEG) recordings we describe a characteristic pattern composed of two distinctive EEG waveforms, Phase 1 and Phase 2, that map onto behavioral arrest and the HTR respectively, with the same temporal separation. Phase 1, which underlies behavioral arrest, is a 3.5-4.5 Hz waveform, while Phase 2 is slower at 2.5-3.2 Hz. Nicotine pretreatment, considered an integral component of ritualistic hallucinogen practices, attenuates 25I-NBOH induced HTR and Phase 2 waveforms, yet increases behavioral arrest and Phase 1 waveforms. Our results suggest that in addition to the HTR, behavioral arrest and characteristic meso level slow waveforms are key hallmarks of the response to 5-HT2AR activation. Increased understanding of the response to serotonergic hallucinogens may provide mechanistic insights into perception and hallucinations, as well as regulation of mood.


Subject(s)
Behavior, Animal/physiology , Hallucinogens/pharmacology , Receptor, Serotonin, 5-HT2A/genetics , Serotonin 5-HT2 Receptor Agonists/pharmacology , Animals , Behavior, Animal/drug effects , Electroencephalography , Head Movements/drug effects , Head Movements/physiology , Humans , Mice , Nicotine/pharmacology
5.
Int J Mol Sci ; 21(12)2020 Jun 22.
Article in English | MEDLINE | ID: mdl-32580510

ABSTRACT

The modulation of neuronal cell firing is mediated by the release of the neurotransmitter GABA (γ-aminobuytric acid), which binds to two major families of receptors. The ionotropic GABAA receptors (GABAARs) are composed of five distinct subunits that vary in expression by brain region and cell type. The action of GABA on GABAARs is modulated by a variety of clinically and pharmacologically important drugs such as benzodiazepines and alcohol. Exposure to and abuse of these substances disrupts homeostasis and induces plasticity in GABAergic neurotransmission, often via the regulation of receptor expression. Here, we review the regulation of GABAAR subunit expression in adaptive and pathological plasticity, with a focus on substance use. We examine the factors influencing the expression of GABAAR subunit genes including the regulation of the 5' and 3' untranslated regions, variations in DNA methylation, immediate early genes and transcription factors that regulate subunit expression, translational and post-translational modifications, and other forms of receptor regulation beyond expression. Advancing our understanding of the factors regulating GABAAR subunit expression during adaptive plasticity, as well as during substance use and withdrawal will provide insight into the role of GABAergic signaling in substance use disorders, and contribute to the development of novel targeted therapies.


Subject(s)
Gene Expression Regulation , Receptors, GABA-A/metabolism , Substance-Related Disorders/pathology , Synaptic Transmission , gamma-Aminobutyric Acid/metabolism , Animals , Humans , Protein Subunits , Receptors, GABA-A/classification , Receptors, GABA-A/genetics , Substance-Related Disorders/metabolism
6.
Front Pharmacol ; 10: 983, 2019.
Article in English | MEDLINE | ID: mdl-31551785

ABSTRACT

Route of administration is well-known to impact factors ranging from absorption and distribution, up through the subjective effects of active ingredients. Different routes of administration confer specific advantages, such as more rapid absorption resulting from intravenous injection, or increased convenience with oral administration, but a combination of both rapid and convenient delivery is highly desirable. QuickStrip™ was designed as a rapidly dissolving thin film matrix that contains active ingredients, which may be promising for rapid and convenient delivery via the oral mucosa. To assess the delivery of QuickStrip™, we administered the well-characterized active ingredient caffeine to mice and compared QuickStrip™ to standard oral gavage delivery at an equivalent dose of 20 mg kg-1. Using HPLC assessment of serum concentrations of caffeine, we found that QuickStrip™ delivery resulted in higher serum levels of caffeine at 1, 10, and 30 min following administration compared to gavage. QuickStrip™ also produced greater bioavailability compared to gavage, as demonstrated by area under the curve analysis. Caffeine delivered by QuickStrip™ produced robust behavioral activation of locomotion, consistent with gavage caffeine. Electroencephalographic (EEG) assessment of central nervous system effects demonstrated that both gavage and QuickStrip™ caffeine produced suppression of delta and theta, consistent with prior literature on the effects of caffeine. In addition, QuickStrip™ produced a more rapid onset of EEG suppression, supporting the more rapid absorption demonstrated in the serum studies. Collectively, these studies suggest that QuickStrip™ may provide a balance between convenience and rapid onset, offering new options for delivery of therapeutics.

7.
Cell Rep ; 28(3): 670-681.e8, 2019 07 16.
Article in English | MEDLINE | ID: mdl-31315046

ABSTRACT

The fidelity of inhibitory neurotransmission is dependent on the accumulation of γ-aminobutyric acid type A receptors (GABAARs) at the appropriate synaptic sites. Synaptic GABAARs are constructed from α(1-3), ß(1-3), and γ2 subunits, and neurons can target these subtypes to specific synapses. Here, we identify a 15-amino acid inhibitory synapse targeting motif (ISTM) within the α2 subunit that promotes the association between GABAARs and the inhibitory scaffold proteins collybistin and gephyrin. Using mice in which the ISTM has been introduced into the α1 subunit (Gabra1-2 mice), we show that the ISTM is critical for axo-axonic synapse formation, the efficacy of GABAergic neurotransmission, and seizure sensitivity. The Gabra1-2 mutation rescues seizure-induced lethality in Gabra2-1 mice, which lack axo-axonic synapses due to the deletion of the ISTM from the α2 subunit. Taken together, our data demonstrate that the ISTM plays a critical role in promoting inhibitory synapse formation, both in the axonic and somatodendritic compartments.


Subject(s)
Amino Acid Motifs/genetics , Axons/metabolism , GABAergic Neurons/metabolism , Receptors, GABA-A/metabolism , Seizures/metabolism , Synapses/metabolism , Animals , Axons/physiology , Cells, Cultured , GABAergic Neurons/physiology , Membrane Proteins/genetics , Membrane Proteins/metabolism , Mice , Mice, Knockout , Receptors, GABA-A/genetics , Rho Guanine Nucleotide Exchange Factors/genetics , Rho Guanine Nucleotide Exchange Factors/metabolism , Seizures/genetics , Seizures/mortality , Synapses/genetics , Synaptic Transmission/physiology
8.
Front Mol Neurosci ; 12: 154, 2019.
Article in English | MEDLINE | ID: mdl-31297048

ABSTRACT

The diversity of inhibitory interneurons allows for the coordination and modulation of excitatory principal cell firing. Interneurons that release GABA (γ-aminobutyric acid) onto the soma and axon exert powerful control by virtue of proximity to the site of action potential generation at the axon initial segment (AIS). Here, we review and examine the cellular and molecular regulation of soma and axon targeting GABAergic synapses in the cortex and hippocampus. We also describe their role in controlling network activity in normal and pathological states. Recent studies have demonstrated a specific role for postsynaptic dystroglycan in the formation and maintenance of cholecystokinin positive basket cell terminals contacting the soma, and postsynaptic collybistin in parvalbumin positive chandelier cell contacts onto the AIS. Unique presynaptic molecular contributors, LGI2 and FGF13, expressed in parvalbumin positive basket cells and chandelier cells, respectively, have also recently been identified. Mutations in the genes encoding proteins critical for somatic and AIS inhibitory synapses have been associated with human disorders of the nervous system. Dystroglycan dysfunction in some congenital muscular dystrophies is associated with developmental brain malformations, intellectual disability, and rare epilepsy. Collybistin dysfunction has been linked to hyperekplexia, epilepsy, intellectual disability, and developmental disorders. Both LGI2 and FGF13 mutations are implicated in syndromes with epilepsy as a component. Advancing our understanding of the powerful roles of somatic and axonic GABAergic contacts in controlling activity patterns in the cortex and hippocampus will provide insight into the pathogenesis of epilepsy and other nervous system disorders.

9.
Nat Commun ; 9(1): 3130, 2018 08 07.
Article in English | MEDLINE | ID: mdl-30087324

ABSTRACT

Fast inhibitory synaptic transmission is mediated by γ-aminobutyric acid type A receptors (GABAARs) that are enriched at functionally diverse synapses via mechanisms that remain unclear. Using isothermal titration calorimetry and complementary methods we demonstrate an exclusive low micromolar binding of collybistin to the α2-subunit of GABAARs. To explore the biological relevance of collybistin-α2-subunit selectivity, we generate mice with a mutation in the α2-subunit-collybistin binding region (Gabra2-1). The mutation results in loss of a distinct subset of inhibitory synapses and decreased amplitude of inhibitory synaptic currents. Gabra2-1 mice have a striking phenotype characterized by increased susceptibility to seizures and early mortality. Surviving Gabra2-1 mice show anxiety and elevations in electroencephalogram δ power, which are ameliorated by treatment with the α2/α3-selective positive modulator, AZD7325. Taken together, our results demonstrate an α2-subunit selective binding of collybistin, which plays a key role in patterned brain activity, particularly during development.


Subject(s)
Receptors, GABA-A/metabolism , Rho Guanine Nucleotide Exchange Factors/metabolism , Seizures/drug therapy , Seizures/mortality , Animals , Brain/metabolism , Electroencephalography , HEK293 Cells , Heterocyclic Compounds, 2-Ring/pharmacology , Humans , Mice , Mice, Inbred C57BL , Mutation , Peptides/chemistry , Phenotype , Protein Binding , Protein Domains , Receptors, GABA-A/genetics , Synapses/metabolism , Synaptic Transmission
10.
Front Mol Neurosci ; 11: 132, 2018.
Article in English | MEDLINE | ID: mdl-29740280

ABSTRACT

The term neurodevelopmental disorder (NDD) is an umbrella term used to group together a heterogeneous class of disorders characterized by disruption in cognition, emotion, and behavior, early in the developmental timescale. These disorders are heterogeneous, yet they share common behavioral symptomatology as well as overlapping genetic contributors, including proteins involved in the formation, specialization, and function of synaptic connections. Advances may arise from bridging the current knowledge on synapse related factors indicated from both human studies in NDD populations, and in animal models. Mounting evidence has shown a link to inhibitory synapse formation, specialization, and function among Autism, Angelman, Rett and Dravet syndromes. Inhibitory signaling is diverse, with numerous subtypes of inhibitory interneurons, phasic and tonic modes of inhibition, and the molecular and subcellular diversity of GABAA receptors. We discuss common ribs of inhibitory synapse dysfunction in the umbrella of NDD, highlighting alterations in the developmental switch to inhibitory GABA, dysregulation of neuronal activity patterns by parvalbumin-positive interneurons, and impaired tonic inhibition. Increasing our basic understanding of inhibitory synapses, and their role in NDDs is likely to produce significant therapeutic advances in behavioral symptom alleviation for interrelated NDDs.

11.
J Neurosci Res ; 96(6): 978-988, 2018 06.
Article in English | MEDLINE | ID: mdl-29315754

ABSTRACT

The brain is the most metabolically active organ in the body. This high metabolic demand is apparent in that 60% of the brain is comprised of mitochondria-enriched cells. A disruption of the brain's ability to meet this immense metabolic demand is central to the pathogenesis of a multitude of neurological disorders, which range from depression to Alzheimer's disease. Central to these pathologies are glial signaling and energy metabolism cascades regulating apoptosis and inflammation. Thus, diseases causing inflammation and disruption of metabolism can be correlated with glial reactivity. Acutely, reactive gliosis provides a mechanism for limiting the progression of a disease. Following chronic activation, the ability of reactive gliosis to limit disease progression decreases and, in some cases, transitions into a harmful state. The necessity for a noninvasive biomarker of disease in the brain has linked reactive gliosis with an upregulation of translocator protein (TSPO). TSPO is an 18kDa protein that is both a therapeutic target for multiple acute and chronic neuroinflammatory diseases and the leading biomarker for Alzheimer's disease. Although a central function of TSPO is not well known, the protein was named for its ability to translocate cholesterol. Increased TSPO expression is an indicator of disrupted metabolic activity and increased reactive oxygen production. The changes in TSPO expression levels both temporally and spatially relate to the pathogenesis of stroke, Alzheimer's disease, traumatic brain injury, and depression. Therefore, research into the basic function and potential therapeutics targeting TSPO will have broad implications for many diseases of the brain.


Subject(s)
Gliosis/metabolism , Neuroglia/metabolism , Receptors, GABA/metabolism , Animals , Brain Diseases/metabolism , Brain Diseases/pathology , Gliosis/pathology , Humans , Inflammation/metabolism , Inflammation/pathology , Neuroglia/pathology
12.
Proc Natl Acad Sci U S A ; 112(11): 3523-8, 2015 Mar 17.
Article in English | MEDLINE | ID: mdl-25733865

ABSTRACT

The K(+)/Cl(-) cotransporter (KCC2) allows adult neurons to maintain low intracellular Cl(-) levels, which are a prerequisite for efficient synaptic inhibition upon activation of γ-aminobutyric acid receptors. Deficits in KCC2 activity are implicated in epileptogenesis, but how increased neuronal activity leads to transporter inactivation is ill defined. In vitro, the activity of KCC2 is potentiated via phosphorylation of serine 940 (S940). Here we have examined the role this putative regulatory process plays in determining KCC2 activity during status epilepticus (SE) using knockin mice in which S940 is mutated to an alanine (S940A). In wild-type mice, SE induced by kainate resulted in dephosphorylation of S940 and KCC2 internalization. S940A homozygotes were viable and exhibited comparable basal levels of KCC2 expression and activity relative to WT mice. However, exposure of S940A mice to kainate induced lethality within 30 min of kainate injection and subsequent entrance into SE. We assessed the effect of the S940A mutation in cultured hippocampal neurons to explore the mechanisms underlying this phenotype. Under basal conditions, the mutation had no effect on neuronal Cl(-) extrusion. However, a selective deficit in KCC2 activity was seen in S940A neurons upon transient exposure to glutamate. Significantly, whereas the effects of glutamate on KCC2 function could be ameliorated in WT neurons with agents that enhance S940 phosphorylation, this positive modulation was lost in S940A neurons. Collectively our results suggest that phosphorylation of S940 plays a critical role in potentiating KCC2 activity to limit the development of SE.


Subject(s)
Status Epilepticus/metabolism , Status Epilepticus/pathology , Symporters/metabolism , Animals , Chlorides/metabolism , Endocytosis , Gene Knock-In Techniques , Glutamates/pharmacology , Mice , Mice, Neurologic Mutants , Mutant Proteins/metabolism , Mutation/genetics , Phosphorylation , Phosphoserine/metabolism , Protein Phosphatase 1/antagonists & inhibitors , Protein Phosphatase 1/metabolism , Symporters/genetics , gamma-Aminobutyric Acid/metabolism , K Cl- Cotransporters
13.
Neuropsychopharmacology ; 39(8): 1805-15, 2014 Jul.
Article in English | MEDLINE | ID: mdl-24553732

ABSTRACT

Despite long-standing concerns regarding the abuse liability of benzodiazepines, the mechanisms underlying properties of benzodiazepines that may be relevant to abuse are still poorly understood. Earlier studies showed that compounds selective for α1-containing GABAA receptors (α1GABAARs) are abused by humans and self-administered by animals, and that these receptors may underlie a preference for benzodiazepines as well as neuroplastic changes observed in the ventral tegmental area following benzodiazepine administration. There is some evidence, however, that even L-838, 417, a compound with antagonistic properties at α1GABAARs and agonistic properties at the other three benzodiazepine-sensitive GABAA receptor subtypes, is self-administered, and that the α2GABAARs may have a role in benzodiazepine-induced reward enhancement. Using a two-bottle choice drinking paradigm to evaluate midazolam preference and an intracranial self-stimulation (ICSS) paradigm to evaluate the impact of midazolam on reward enhancement, we demonstrated that mice carrying a histidine-to-arginine point mutation in the α2 subunit which renders it insensitive to benzodiazepines (α2(H101R) mice) did not prefer midazolam and did not show midazolam-induced reward enhancement in ICSS, in contrast to wild-type controls, suggesting that α2GABAARs are necessary for the reward enhancing effects and preference for oral benzodiazepines. Through a viral-mediated knockdown of α2GABAARs in the nucleus accumbens (NAc), we demonstrated that α2 in the NAc is necessary for the preference for midazolam. Findings imply that α2GABAARs in the NAc are involved in at least some reward-related properties of benzodiazepines, which might partially underlie repeated drug-taking behavior.


Subject(s)
Choice Behavior/drug effects , GABA Modulators/pharmacology , Midazolam/pharmacology , Nucleus Accumbens/drug effects , Receptors, GABA-A/physiology , Reward , Animals , Male , Mice , Mice, Transgenic
14.
Proc Natl Acad Sci U S A ; 110(41): 16628-33, 2013 Oct 08.
Article in English | MEDLINE | ID: mdl-24043839

ABSTRACT

In schizophrenia, cognitive dysfunction is highly predictive of poor patient outcomes and is not responsive to current medications. Postmortem studies have suggested that cognitive deficits in schizophrenia are correlated with modifications in the number and size of inhibitory synapses. To test if these modifications lead to cognitive deficits, we have created a dominant-negative virus [adeno-associated (AAV)-DN1] that disrupts the clustering of γ-aminobutyric acid type A receptors (GABA(A)Rs) at postsynaptic inhibitory specializations. When injected into the frontal cortex of mice, AAV-DN1 impairs GABA(A)R α2 subunit and GABA transporter 1 (GAT-1) clustering, but increases GABA(A)R α1 subunit clustering on the perisomatic region, with no influence on axon-initial segment clustering. Mice expressing AAV-DN1 have prepulse inhibition deficits and impairments in working memory. Significantly, these behavioral deficits are paralleled by a reduction in electroencephalography γ-power. Collectively, our study provides functional evidence revealing that GABAergic synapses in the prefrontal cortex directly contribute to cognition and γ-power.


Subject(s)
Cognition/physiology , Dependovirus/genetics , Disease Models, Animal , Frontal Lobe/metabolism , Receptors, GABA-A/metabolism , Schizophrenia/metabolism , Animals , Electroencephalography , GABA Plasma Membrane Transport Proteins/metabolism , Genetic Engineering/methods , Genetic Vectors/genetics , Immunohistochemistry , Mice , Schizophrenia/pathology , Signal Transduction/physiology
15.
J Neurosci ; 33(39): 15567-77, 2013 Sep 25.
Article in English | MEDLINE | ID: mdl-24068823

ABSTRACT

Brain-derived neurotrophic factor (BDNF) is a potent regulator of neuronal activity, neurogenesis, and depressive-like behaviors; however, downstream effectors by which BDNF exerts these varying actions remain to be determined. Here we reveal that BDNF induces long-lasting enhancements in the efficacy of synaptic inhibition by stabilizing γ2 subunit-containing GABA(A) receptors (GABA(A)Rs) at the cell surface, leading to persistent reductions in neuronal excitability. This effect is dependent upon enhanced phosphorylation of tyrosines 365 and 367 (Y365/7) in the GABA(A)R γ2 subunit as revealed using mice in which these residues have been mutated to phenyalanines (Y365/7F). Heterozygotes for this mutation exhibit an antidepressant-like phenotype, as shown using behavioral-despair models of depression. In addition, heterozygous Y365/7F mice show increased levels of hippocampal neurogenesis, which has been strongly connected with antidepressant action. Both the antidepressant phenotype and the increased neurogenesis seen in these mice are insensitive to further modulation by BDNF, which produces robust antidepressant-like activity and neurogenesis in wild-type mice. Collectively, our results suggest a critical role for GABA(A)R γ2 subunit Y365/7 phosphorylation and function in regulating the effects of BDNF.


Subject(s)
Brain-Derived Neurotrophic Factor/pharmacology , Depression/drug therapy , Neurogenesis/drug effects , Neurons/metabolism , Receptors, GABA-A/metabolism , Animals , Brain-Derived Neurotrophic Factor/therapeutic use , Depression/genetics , Heterozygote , Hippocampus/cytology , Hippocampus/metabolism , Hippocampus/physiology , Inhibitory Postsynaptic Potentials/drug effects , Inhibitory Postsynaptic Potentials/genetics , Mice , Mutation, Missense , Neurogenesis/genetics , Neurons/cytology , Neurons/physiology , Phenotype , Phosphorylation , Protein Subunits/genetics , Protein Subunits/metabolism , Protein Transport/drug effects , Receptors, GABA-A/genetics , Tyrosine/genetics , Tyrosine/metabolism
16.
PLoS One ; 8(3): e60388, 2013.
Article in English | MEDLINE | ID: mdl-23555964

ABSTRACT

The innate immune receptor Toll-like 4 (TLR4) is the receptor activated by lipopolysaccharide (LPS), and TLR4-LPS interaction is well known to induce an innate immune response, triggering sickness behavior. Within the brain, TLR4 is highly expressed in brain microglia, and excessive inflammation resulting from activation of this pathway in the brain has been implicated in depressive disorders and neurodegenerative pathologies. We hypothesized that blocking LPS-induced activation of TLR4 would prevent downstream immune signaling in the brain and suppress the induction of sickness behavior. We used interfering peptides to block TLR4 activation and confirmed their efficacy in preventing second messenger activation and cytokine production normally induced by LPS treatment. Further, these peptides blocked morphological changes in microglia that are typically induced by LPS. We also demonstrated that intraperitoneal (i.p.) injection of Tat-TLR4 interfering peptides prevented LPS-induced sickness behavior, as assessed in home cage behavior and with the intracranial self-stimulation paradigm. These newly synthesised peptides inhibit TLR4 signaling thereby preventing changes in behavior and motivation caused by inflammatory stimuli. These peptides highlight the roll of TLR4 and microglia morphology changes in sickness behavior, and thus may be of therapeutic value in limiting the deleterious impact of excessive inflammation in specific CNS pathologies.


Subject(s)
Cytokines/immunology , Illness Behavior/drug effects , Lipopolysaccharides/immunology , Microglia/drug effects , Peptides/pharmacology , Toll-Like Receptor 4/antagonists & inhibitors , Toll-Like Receptor 4/immunology , Amino Acid Sequence , Animals , Brain/drug effects , Brain/immunology , Brain/pathology , Humans , Immunity, Innate/drug effects , Mice , Microglia/immunology , Microglia/pathology , Molecular Sequence Data , Peptides/chemistry , Signal Transduction/drug effects
17.
J Neurosci ; 33(17): 7264-73, 2013 Apr 24.
Article in English | MEDLINE | ID: mdl-23616535

ABSTRACT

Intravenous anesthetics exert a component of their actions via potentiating inhibitory neurotransmission mediated by γ-aminobutyric type-A receptors (GABAARs). Phasic and tonic inhibition is mediated by distinct populations of GABAARs, with the majority of phasic inhibition by subtypes composed of α1-3ßγ2 subunits, whereas tonic inhibition is dependent on subtypes assembled from α4-6ßδ subunits. To explore the contribution that these distinct forms of inhibition play in mediating intravenous anesthesia, we have used mice in which tyrosine residues 365/7 within the γ2 subunit are mutated to phenyalanines (Y365/7F). Here we demonstrate that this mutation leads to increased accumulation of the α4 subunit containing GABAARs in the thalamus and dentate gyrus of female Y365/7F but not male Y365/7F mice. Y365/7F mice exhibited a gender-specific enhancement of tonic inhibition in the dentate gyrus that was more sensitive to modulation by the anesthetic etomidate, together with a deficit in long-term potentiation. Consistent with this, female Y365/7F, but not male Y365/7F, mice exhibited a dramatic increase in the duration of etomidate- and propofol-mediated hypnosis. Moreover, the amnestic actions of etomidate were selectively potentiated in female Y365/7F mice. Collectively, these observations suggest that potentiation of tonic inhibition mediated by α4 subunit containing GABAARs contributes to the hypnotic and amnestic actions of the intravenous anesthetics, etomidate and propofol.


Subject(s)
Amnesia/chemically induced , Etomidate/administration & dosage , Hypnotics and Sedatives/administration & dosage , Long-Term Potentiation/drug effects , Neural Inhibition/drug effects , Propofol/administration & dosage , Amnesia/physiopathology , Anesthetics, Intravenous/administration & dosage , Animals , Female , Hippocampus/drug effects , Hippocampus/physiology , Long-Term Potentiation/physiology , Male , Mice , Mice, Inbred C57BL , Mice, Transgenic , Neural Inhibition/physiology , Organ Culture Techniques , Random Allocation
18.
Curr Opin Neurobiol ; 22(3): 552-8, 2012 Jun.
Article in English | MEDLINE | ID: mdl-22036769

ABSTRACT

Inhibitory neurotransmission is primarily governed by γ-aminobutyric acid (GABA) type A receptors (GABAARs). GABAARs are heteropentameric ligand-gated channels formed by the combination of 19 possible subunits. GABAAR subunits are subject to multiple types of regulation, impacting the localization, properties, and function of assembled receptors. GABAARs mediate both phasic (synaptic) and tonic (extrasynaptic) inhibition. While the regulatory mechanisms governing synaptic receptors have begun to be defined, little is known about the regulation of extrasynaptic receptors. We examine the contributions of GABAARs to the pathogenesis of neurodevelopmental disorders, schizophrenia, depression, epilepsy, and stroke, with particular focus on extrasynaptic GABAARs. We suggest that extrasynaptic GABAARs are attractive targets for the treatment of these disorders, and that research should be focused on delineating the mechanisms that regulate extrasynaptic GABAARs, promoting new therapeutic approaches.


Subject(s)
Nervous System Diseases/metabolism , Nervous System Diseases/pathology , Receptors, GABA/metabolism , Animals , Humans , Receptors, GABA/classification , Synapses/metabolism , Synapses/pathology
19.
Neuron ; 65(2): 178-90, 2010 Jan 28.
Article in English | MEDLINE | ID: mdl-20152125

ABSTRACT

N-methyl-D-aspartate receptor (NMDAR) excitotoxicity is implicated in the pathogenesis of Huntington's disease (HD), a late-onset neurodegenerative disorder. However, NMDARs are poor therapeutic targets, due to their essential physiological role. Recent studies demonstrate that synaptic NMDAR transmission drives neuroprotective gene transcription, whereas extrasynaptic NMDAR activation promotes cell death. We report specifically increased extrasynaptic NMDAR expression, current, and associated reductions in nuclear CREB activation in HD mouse striatum. The changes are observed in the absence of dendritic morphological alterations, before and after phenotype onset, correlate with mutation severity, and require caspase-6 cleavage of mutant huntingtin. Moreover, pharmacological block of extrasynaptic NMDARs with memantine reversed signaling and motor learning deficits. Our data demonstrate elevated extrasynaptic NMDAR activity in an animal model of neurodegenerative disease. We provide a candidate mechanism linking several pathways previously implicated in HD pathogenesis and demonstrate successful early therapeutic intervention in mice.


Subject(s)
Disease Models, Animal , Gene Expression Regulation , Huntington Disease/metabolism , Phenotype , Receptors, N-Methyl-D-Aspartate/biosynthesis , Signal Transduction/physiology , Synapses/metabolism , Action Potentials/genetics , Animals , Huntington Disease/genetics , Mice , Mice, Transgenic , Receptors, N-Methyl-D-Aspartate/genetics , Signal Transduction/genetics , Synapses/chemistry , Synapses/genetics , Synaptic Transmission/genetics , Time Factors
20.
J Biol Chem ; 285(7): 4621-8, 2010 Feb 12.
Article in English | MEDLINE | ID: mdl-19955568

ABSTRACT

The Golgi-specific zinc finger protein GODZ (palmitoyl acyltransferase/DHHC-3) mediates the palmitoylation and post-translational modification of many protein substrates that regulate membrane-protein interactions. Here, we show that GODZ also mediates Ca(2+) transport in expressing Xenopus laevis oocytes. Two-electrode voltage-clamp, fluorescence, and (45)Ca(2+) isotopic uptake determinations demonstrated voltage- and concentration-dependent, saturable, and substrate-inhibitable Ca(2+) transport in oocytes expressing GODZ cRNA but not in oocytes injected with water alone. Moreover, we show that GODZ-mediated Ca(2+) transport is regulated by palmitoylation, as the palmitoyl acyltransferase inhibitor 2-bromopalmitate or alteration of the acyltransferase DHHC motif (GODZ-DHHS) diminished GODZ-mediated Ca(2+) transport by approximately 80%. The GODZ mutation V61R abolished Ca(2+) transport but did not affect palmitoyl acyltransferase activity. Coexpression of GODZ-V61R with GODZ-DHHS restored GODZ-DHHS-mediated Ca(2+) uptake to values observed with wild-type GODZ, excluding an endogenous effect of palmitoylation. Coexpression of an independent palmitoyl acyltransferase (HIP14) with the GODZ-DHHS mutant also rescued Ca(2+) transport. HIP14 did not mediate Ca(2+) transport when expressed alone. Immunocytochemistry studies showed that GODZ and HIP14 co-localized to the Golgi and the same post-Golgi vesicles, suggesting that heteropalmitoylation might play a physiological role in addition to a biochemical function. We conclude that GODZ encodes a Ca(2+) transport protein in addition to its ability to palmitoylate protein substrates.


Subject(s)
Acyltransferases/metabolism , Calcium/metabolism , Golgi Apparatus/metabolism , Membrane Proteins/metabolism , Acyltransferases/chemistry , Acyltransferases/genetics , Adaptor Proteins, Signal Transducing/chemistry , Adaptor Proteins, Signal Transducing/genetics , Adaptor Proteins, Signal Transducing/metabolism , Amino Acid Motifs/genetics , Amino Acid Motifs/physiology , Amino Acid Sequence , Animals , COS Cells , Chlorocebus aethiops , Green Fluorescent Proteins/genetics , Green Fluorescent Proteins/metabolism , Humans , Membrane Proteins/chemistry , Membrane Proteins/genetics , Mice , Microscopy, Confocal , Molecular Sequence Data , Nerve Tissue Proteins/chemistry , Nerve Tissue Proteins/genetics , Nerve Tissue Proteins/metabolism , Oocytes , Protein Transport/genetics , Protein Transport/physiology , Xenopus/genetics , Xenopus/metabolism
SELECTION OF CITATIONS
SEARCH DETAIL
...