scholarly journals Artemisinin-treatment in pre-symptomatic APP-PS1 mice increases gephyrin phosphorylation at Ser270: a modification regulating postsynaptic GABAAR density

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Eva Kiss ◽  
Stefan Kins ◽  
Karin Gorgas ◽  
Maret Orlik ◽  
Carolin Fischer ◽  
...  
Keyword(s):  
Hippocampal Neurons ◽  
Sesquiterpene Lactones ◽  
Phosphorylation Sites ◽  
Additional Increase ◽  
Antimalarial Agents ◽  
Gabaergic Synapses ◽  
Protein Density ◽  
Activity Dependent ◽  
The Brain

Abstract Artemisinins, a group of plant-derived sesquiterpene lactones, are efficient antimalarial agents. They also share anti-inflammatory and anti-viral activities and were considered for treatment of neurodegenerative disorders like Alzheimer’s disease (AD). Additionally, artemisinins bind to gephyrin, the multifunctional scaffold of GABAergic synapses, and modulate inhibitory neurotransmission in vitro. We previously reported an increased expression of gephyrin and GABAA receptors in early pre-symptomatic stages of an AD mouse model (APP-PS1) and in parallel enhanced CDK5-dependent phosphorylation of gephyrin at S270. Here, we studied the effects of artemisinin on gephyrin in the brain of young APP-PS1 mice. We detected an additional increase of gephyrin protein level, elevated gephyrin phosphorylation at Ser270, and an increased amount of GABAAR-γ2 subunits after artemisinin-treatment. Interestingly, the CDK5 activator p35 was also upregulated. Moreover, we demonstrate decreased density of postsynaptic gephyrin and GABAAR-γ2 immunoreactivities in cultured hippocampal neurons expressing gephyrin with alanine mutations at two CDK5 phosphorylation sites. In addition, the activity-dependent modulation of synaptic protein density was abolished in neurons expressing gephyrin lacking one or both of these phosphorylation sites. Thus, our results reveal that artemisinin modulates expression as well as phosphorylation of gephyrin at sites that might have important impact on GABAergic synapses in AD.

scholarly journals Ps in the (Channel) Pod Are Not Alike …

2007 ◽  
Vol 7 (5) ◽  
pp. 136-137
Author(s):  
Yoav Noam ◽  
Tallie Z. Baram
Keyword(s):  
Neuronal Activity ◽  
Hippocampal Neurons ◽  
Neuronal Excitability ◽  
Phosphorylation Sites ◽  
Voltage Dependent ◽  
Activity Dependent ◽  
Stimulation Of ◽  
Cultured Hippocampal Neurons

Bidirectional Activity-Dependent Regulation of Neuronal Ion Channel Phosphorylation. Misonou H, Menegola M, Mohapatra DP, Guy LK, Park KS, Trimmer JS. J Neurosci 2006;26(52):13505–13514. Activity-dependent dephosphorylation of neuronal Kv2.1 channels yields hyperpolarizing shifts in their voltage-dependent activation and homoeostatic suppression of neuronal excitability. We recently identified 16 phosphorylation sites that modulate Kv2.1 function. Here, we show that in mammalian neurons, compared with other regulated sites, such as serine (S)563, phosphorylation at S603 is supersensitive to calcineurin-mediated dephosphorylation in response to kainate-induced seizures in vivo, and brief glutamate stimulation of cultured hippocampal neurons. In vitro calcineurin digestion shows that supersensitivity of S603 dephosphorylation is an inherent property of Kv2.1. Conversely, suppression of neuronal activity by anesthetic in vivo causes hyperphosphorylation at S603 but not S563. Distinct regulation of individual phosphorylation sites allows for graded and bidirectional homeostatic regulation of Kv2.1 function. S603 phosphorylation represents a sensitive bidirectional biosensor of neuronal activity.

scholarly journals Regulation of GABAergic synapse formation and plasticity by GSK3β-dependent phosphorylation of gephyrin

2010 ◽  
Vol 108 (1) ◽  
pp. 379-384 ◽  
Author(s):  
Shiva K. Tyagarajan ◽  
Himanish Ghosh ◽  
Gonzalo E. Yévenes ◽  
Irina Nikonenko ◽  
Claire Ebeling ◽  
...  
Keyword(s):  
Synaptic Plasticity ◽  
Hippocampal Neurons ◽  
Glycogen Synthase ◽  
Phosphorylation Site ◽  
Scaffolding Protein ◽  
Scaffolding Proteins ◽  
Gabaergic Synapse ◽  
Gabaergic Synapses

Postsynaptic scaffolding proteins ensure efficient neurotransmission by anchoring receptors and signaling molecules in synapse-specific subcellular domains. In turn, posttranslational modifications of scaffolding proteins contribute to synaptic plasticity by remodeling the postsynaptic apparatus. Though these mechanisms are operant in glutamatergic synapses, little is known about regulation of GABAergic synapses, which mediate inhibitory transmission in the CNS. Here, we focused on gephyrin, the main scaffolding protein of GABAergic synapses. We identify a unique phosphorylation site in gephyrin, Ser270, targeted by glycogen synthase kinase 3β (GSK3β) to modulate GABAergic transmission. Abolishing Ser270 phosphorylation increased the density of gephyrin clusters and the frequency of miniature GABAergic postsynaptic currents in cultured hippocampal neurons. Enhanced, phosphorylation-dependent gephyrin clustering was also induced in vitro and in vivo with lithium chloride. Lithium is a GSK3β inhibitor used therapeutically as mood-stabilizing drug, which underscores the relevance of this posttranslational modification for synaptic plasticity. Conversely, we show that gephyrin availability for postsynaptic clustering is limited by Ca2+-dependent gephyrin cleavage by the cysteine protease calpain-1. Together, these findings identify gephyrin as synaptogenic molecule regulating GABAergic synaptic plasticity, likely contributing to the therapeutic action of lithium.

scholarly journals MyD88-5 links mitochondria, microtubules, and JNK3 in neurons and regulates neuronal survival

2007 ◽  
Vol 204 (9) ◽  
pp. 2063-2074 ◽  
Author(s):  
Younghwa Kim ◽  
Ping Zhou ◽  
Liping Qian ◽  
Jen-Zen Chuang ◽  
Jessica Lee ◽  
...  
Keyword(s):  
Hippocampal Neurons ◽  
Artificial Chromosome ◽  
Adaptor Proteins ◽  
Innate Immune ◽  
Molecular Structures ◽  
Endogenous Expression ◽  
Microbial Products ◽  
The Brain ◽  
Deficient Mice

The innate immune system relies on evolutionally conserved Toll-like receptors (TLRs) to recognize diverse microbial molecular structures. Most TLRs depend on a family of adaptor proteins termed MyD88s to transduce their signals. Critical roles of MyD88-1–4 in host defense were demonstrated by defective immune responses in knockout mice. In contrast, the sites of expression and functions of vertebrate MyD88-5 have remained elusive. We show that MyD88-5 is distinct from other MyD88s in that MyD88-5 is preferentially expressed in neurons, colocalizes in part with mitochondria and JNK3, and regulates neuronal death. We prepared MyD88-5/GFP transgenic mice via a bacterial artificial chromosome to preserve its endogenous expression pattern. MyD88-5/GFP was detected chiefly in the brain, where it associated with punctate structures within neurons and copurified in part with mitochondria. In vitro, MyD88-5 coimmunoprecipitated with JNK3 and recruited JNK3 from cytosol to mitochondria. Hippocampal neurons from MyD88-5–deficient mice were protected from death after deprivation of oxygen and glucose. In contrast, MyD88-5–null macrophages behaved like wild-type cells in their response to microbial products. Thus, MyD88-5 appears unique among MyD88s in functioning to mediate stress-induced neuronal toxicity.

scholarly journals TBK1 interacts with tau and enhances neurodegeneration in tauopathy

2020 ◽  
Author(s):  
Measho H. Abreha ◽  
Shamsideen Ojelade ◽  
Eric B. Dammer ◽  
Zachary T. McEachin ◽  
Duc M. Duong ◽  
...  
Keyword(s):  
Neuronal Loss ◽  
Postmortem Brain ◽  
Chromosome 17 ◽  
Phosphorylation Sites ◽  
Tau Hyperphosphorylation ◽  
Reciprocal Effect ◽  
Full Complement ◽  
The Brain ◽  
Brain Tissues

ABSTRACTOne of the defining pathological features of Alzheimer’s Disease (AD) is the deposition of neurofibrillary tangles (NFTs) composed of hyperphosphorylated tau in the brain. Aberrant activation of kinases in AD has been suggested to enhance phosphorylation and toxicity of tau, making the responsible tau-directed kinases attractive therapeutic targets. The full complement of tau interacting kinases in AD brain and their activity in disease remains incompletely defined. Here, immunoaffinity enrichment coupled with mass spectrometry (MS) identified TANK-binding kinase 1 (TBK1) as a tau-interacting partner in human AD cortical brain tissues. We validated this interaction in both human AD and familial frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17) caused by mutations in MAPT (R406W) postmortem brain tissues as well as human cell lines. Further, we document increased TBK1 activity in both AD and FTDP-17 and map the predominant TBK1 phosphorylation sites on tau based on in vitro kinase assays coupled to MS. Lastly, in a Drosophila tauopathy model, activating expression of a conserved TBK1 ortholog triggers tau hyperphosphorylation and enhanced neurodegeneration, whereas knockdown had the reciprocal effect, suppressing tau toxicity. Collectively, our findings suggest that increased TBK1 activity may promote tau hyperphosphorylation and neuronal loss in AD and related tauopathies.

scholarly journals Functional Implications of Glycogen Synthase Kinase-3-Mediated Tau Phosphorylation

2011 ◽  
Vol 2011 ◽  
pp. 1-11 ◽  
Author(s):  
Diane P. Hanger ◽  
Wendy Noble
Keyword(s):  
Glycogen Synthase ◽  
Regulatory Element ◽  
Tau Phosphorylation ◽  
Glycogen Synthase Kinase ◽  
Glycogen Synthase Kinase 3 ◽  
Phosphorylation Sites ◽  
Pick Bodies ◽  
Functional Implications ◽  
The Brain

Tau is primarily a neuronal microtubule-associated protein that has functions related to the stabilisation of microtubules. Phosphorylation of tau is an important dynamic and regulatory element involved in the binding of tau to tubulin. Thus, highly phosphorylated tau is more likely to be present in the cytosolic compartment of neurons, whereas reduced phosphate burden allows tau to bind to and stabilise the microtubule cytoskeleton. Highly phosphorylated forms of tau are deposited in the brain in a range of neurodegenerative disorders including Alzheimer's disease, progressive supranuclear palsy, and frontotemporal lobar degeneration associated with Pick bodies. A key candidate kinase for both physiological and pathological tau phosphorylation is glycogen synthase kinase-3 (GSK-3). Multiple phosphorylation sites have been identified on tau exposed to GSK-3in vitroand in cells. In this review, we highlight recent data suggesting a role for GSK-3 activity on physiological tau function and on tau dysfunction in neurodegenerative disease.

Roles of glutamine in neurotransmission

2010 ◽  
Vol 6 (4) ◽  
pp. 263-276 ◽  
Author(s):  
Jan Albrecht ◽  
Marta Sidoryk-Węgrzynowicz ◽  
Magdalena Zielińska ◽  
Michael Aschner
Keyword(s):  
Amino Acids ◽  
Significant Proportion ◽  
Brain Slices ◽  
Amino Butyric Acid ◽  
Pathological Conditions ◽  
The Central Nervous System ◽  
Activity Dependent ◽  
The Brain

Glutamine (Gln) is found abundantly in the central nervous system (CNS) where it participates in a variety of metabolic pathways. Its major role in the brain is that of a precursor of the neurotransmitter amino acids: the excitatory amino acids, glutamate (Glu) and aspartate (Asp), and the inhibitory amino acid, γ-amino butyric acid (GABA). The precursor–product relationship between Gln and Glu/GABA in the brain relates to the intercellular compartmentalization of the Gln/Glu(GABA) cycle (GGC). Gln is synthesized from Glu and ammonia in astrocytes, in a reaction catalyzed by Gln synthetase (GS), which, in the CNS, is almost exclusively located in astrocytes (Martinez-Hernandez et al., 1977). Newly synthesized Gln is transferred to neurons and hydrolyzed by phosphate-activated glutaminase (PAG) to give rise to Glu, a portion of which may be decarboxylated to GABA or transaminated to Asp. There is a rich body of evidence which indicates that a significant proportion of the Glu, Asp and GABA derived from Gln feed the synaptic, neurotransmitter pools of the amino acids. Depolarization-induced-, calcium- and PAG activity-dependent releases of Gln-derived Glu, GABA and Asp have been observed in CNS preparations in vitro and in the brain in situ. Immunocytochemical studies in brain slices have documented Gln transfer from astrocytes to neurons as well as the location of Gln-derived Glu, GABA and Asp in the synaptic terminals. Patch-clamp studies in brain slices and astrocyte/neuron co-cultures have provided functional evidence that uninterrupted Gln synthesis in astrocytes and its transport to neurons, as mediated by specific carriers, promotes glutamatergic and GABA-ergic transmission. Gln entry into the neuronal compartment is facilitated by its abundance in the extracellular spaces relative to other amino acids. Gln also appears to affect neurotransmission directly by interacting with the NMDA class of Glu receptors. Transmission may also be modulated by alterations in cell membrane polarity related to the electrogenic nature of Gln transport or to uncoupled ion conductances in the neuronal or glial cell membranes elicited by Gln transporters. In addition, Gln appears to modulate the synthesis of the gaseous messenger, nitric oxide (NO), by controlling the supply to the cells of its precursor, arginine. Disturbances of Gln metabolism and/or transport contribute to changes in Glu-ergic or GABA-ergic transmission associated with different pathological conditions of the brain, which are best recognized in epilepsy, hepatic encephalopathy and manganese encephalopathy.

scholarly journals Astrocytes regulate brain extracellular pH via a neuronal activity-dependent bicarbonate shuttle

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Shefeeq M. Theparambil ◽  
Patrick S. Hosford ◽  
Iván Ruminot ◽  
Olga Kopach ◽  
James R. Reynolds ◽  
...  
Keyword(s):  
Neuronal Activity ◽  
Extracellular Ph ◽  
Ph Homeostasis ◽  
Sodium Bicarbonate Cotransporter ◽  
Highly Sensitive ◽  
Activity Dependent ◽  
The Brain ◽  
Local Brain

Abstract Brain cells continuously produce and release protons into the extracellular space, with the rate of acid production corresponding to the levels of neuronal activity and metabolism. Efficient buffering and removal of excess H+ is essential for brain function, not least because all the electrogenic and biochemical machinery of synaptic transmission is highly sensitive to changes in pH. Here, we describe an astroglial mechanism that contributes to the protection of the brain milieu from acidification. In vivo and in vitro experiments conducted in rodent models show that at least one third of all astrocytes release bicarbonate to buffer extracellular H+ loads associated with increases in neuronal activity. The underlying signalling mechanism involves activity-dependent release of ATP triggering bicarbonate secretion by astrocytes via activation of metabotropic P2Y1 receptors, recruitment of phospholipase C, release of Ca2+ from the internal stores, and facilitated outward HCO3− transport by the electrogenic sodium bicarbonate cotransporter 1, NBCe1. These results show that astrocytes maintain local brain extracellular pH homeostasis via a neuronal activity-dependent release of bicarbonate. The data provide evidence of another important metabolic housekeeping function of these glial cells.

scholarly journals The small GTPase ARF6 regulates GABAergic synapse development

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Hyeonho Kim ◽  
Hyeji Jung ◽  
Hyunsu Jung ◽  
Seok-Kyu Kwon ◽  
Jaewon Ko ◽  
...  
Keyword(s):  
Membrane Trafficking ◽  
Hippocampal Neurons ◽  
Small Gtpases ◽  
Small Gtpase ◽  
Dependent Manner ◽  
Cellular Functions ◽  
Gabaergic Synapse ◽  
Gabaergic Synapses ◽  
Hippocampal Network ◽  
Activity Dependent

AbstractADP ribosylation factors (ARFs) are a family of small GTPases composed of six members (ARF1–6) that control various cellular functions, including membrane trafficking and actin cytoskeletal rearrangement, in eukaryotic cells. Among them, ARF1 and ARF6 are the most studied in neurons, particularly at glutamatergic synapses, but their roles at GABAergic synapses have not been investigated. Here, we show that a subset of ARF6 protein is localized at GABAergic synapses in cultured hippocampal neurons. In addition, we found that knockdown (KD) of ARF6, but not ARF1, triggered a reduction in the number of GABAergic synaptic puncta in mature cultured neurons in an ARF activity-dependent manner. ARF6 KD also reduced GABAergic synaptic density in the mouse hippocampal dentate gyrus (DG) region. Furthermore, ARF6 KD in the DG increased seizure susceptibility in an induced epilepsy model. Viewed together, our results suggest that modulating ARF6 and its regulators could be a therapeutic strategy against brain pathologies involving hippocampal network dysfunction, such as epilepsy.

scholarly journals Neurite growth kinetics regulation through hydrostatic pressure in a novel triangle-shaped neurofluidic system

2021 ◽  
Author(s):  
B. G. C. Maisonneuve ◽  
A. Batut ◽  
C. Varela ◽  
J. Vieira ◽  
M. Gleyzes ◽  
...  
Keyword(s):  
Hydrostatic Pressure ◽  
Growth Kinetics ◽  
Hippocampal Neurons ◽  
Neurite Growth ◽  
Neurite Length ◽  
Triangular Design ◽  
Kinetics Of ◽  
The Brain

AbstractMicrofluidic neuro-engineering design rules have been widely explored to create in vitro neural networks with the objective to replicate physiologically relevant structures of the brain. Several neurofluidic strategies have been reported to study the connectivity of neurons, either within a population or between two separated populations, through the control of the directionality of their neuronal projections. Yet, the in vitro regulation of the growth kinetics of those projections remains challenging. Here, we describe a new neurofluidic chip with a triangular design that allows the accurate monitoring of neurite growth kinetics in a neuronal culture. This device permits to measure the maximum achievable length of projecting neurites over time and to report variations in neurite length under several conditions. Our results show that, by applying positive or negative hydrostatic pressure to primary rat hippocampal neurons, neurite growth kinetics can be tuned. This work presents a pioneering approach for the precise characterization of neurite length dynamics within an in vitro minimalistic environment.

scholarly journals Iron Overload contributes to General Anesthesia-induced Neurotoxicity and Cognitive Deficits

2020 ◽  
Author(s):  
Jing Wu ◽  
Jian-Jun Yang ◽  
Yan Cao ◽  
Huihui Li ◽  
Hongting Zhao ◽  
...  
Keyword(s):  
Iron Overload ◽  
General Anesthesia ◽  
Iron Metabolism ◽  
Cognitive Deficits ◽  
Hippocampal Neurons ◽  
Iron Homeostasis ◽  
The Impact ◽  
The Brain

Abstract Background: Increasing evidence suggests that multiple or long-time exposure to general anesthesia (GA) could be detrimental to cognitive development in young subjects, and might also contribute to accelerated neurodegeneration in the elderly. Iron is essential for normal neuronal function and excess iron in brain is implicated in several neurodegenerative diseases. However, the role of iron in GA-induced neurotoxicity and cognitive deficits remains elusive. Methods: We used the primary hippocampal neurons and rodents including young rats and aged mice to examine whether GA impacted iron metabolism and whether the impact contributed to neuronal outcomes. In addition, a pharmacological suppression of iron metabolism was performed to explore the molecular mechanism underlying GAs-mediated iron overload in the brain. Results: Our results demonstrated that GA, induced by intravenous ketamine or inhalational sevoflurane, disturbed iron homeostasis and caused iron overload in both in vitro hippocampal neuron culture and in vivo hippocampus. Interestingly, ketamine or sevoflurane-induced cognitive deficits, very likely, resulted from a novel iron-dependent regulated cell death, ferroptosis. Notably, iron chelator deferiprone attenuated the GA-induced mitochondrial dysfunction, ferroptosis, and further cognitive deficits. Moreover, we found that GA-induced iron overload was activated by NMDAR-RASD1 signalling via DMT1 action in the brain. Conclusion: We conclude that disturbed iron metabolism may be involved in the pathogenesis of GA-induced neurotoxicity and cognitive deficits. Our study provides new vision for consideration in GA-associated neurological disorders.

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