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1.
J Neurosci ; 44(23)2024 Jun 05.
Article in English | MEDLINE | ID: mdl-38839340

ABSTRACT

A decade ago, in 2013, and over the course of 4 summer months, three separate observations were reported that each shed light independently on a new molecular organization that fundamentally reshaped our perception of excitatory synaptic transmission (Fukata et al., 2013; MacGillavry et al., 2013; Nair et al., 2013). This discovery unveiled an intricate arrangement of AMPA-type glutamate receptors and their principal scaffolding protein PSD-95, at synapses. This breakthrough was made possible, thanks to advanced super-resolution imaging techniques. It fundamentally changed our understanding of excitatory synaptic architecture and paved the way for a brand-new area of research. In this Progressions article, the primary investigators of the nanoscale organization of synapses have come together to chronicle the tale of their discovery. We recount the initial inquiry that prompted our research, the preceding studies that inspired our work, the technical obstacles that were encountered, and the breakthroughs that were made in the subsequent decade in the realm of nanoscale synaptic transmission. We review the new discoveries made possible by the democratization of super-resolution imaging techniques in the field of excitatory synaptic physiology and architecture, first by the extension to other glutamate receptors and to presynaptic proteins and then by the notion of trans-synaptic organization. After describing the organizational modifications occurring in various pathologies, we discuss briefly the latest technical developments made possible by super-resolution imaging and emerging concepts in synaptic physiology.


Subject(s)
Receptors, AMPA , Synapses , Receptors, AMPA/metabolism , Receptors, AMPA/chemistry , Synapses/metabolism , Synapses/ultrastructure , Animals , Humans , Synaptic Transmission/physiology , Nanostructures/chemistry
2.
Methods Cell Biol ; 187: 57-72, 2024.
Article in English | MEDLINE | ID: mdl-38705630

ABSTRACT

Correlative light and electron microscopy (CLEM) can provide valuable information about a biological sample by giving information on the specific localization of a molecule of interest within an ultrastructural context. In this work, we describe a simple CLEM method to obtain high-resolution images of neurotransmitter receptor distribution in synapses by electron microscopy (EM). We use hippocampal organotypic slices from a previously reported mouse model expressing a modified AMPA receptor (AMPAR) subunit that binds biotin at the surface (Getz et al., 2022). This tag can be recognized by StreptAvidin-Fluoronanogold™ conjugates (SA-FNG), which reach receptors at synapses (synaptic cleft is 50-100nm thick). By using pre-embedding labeling, we found that SA-FNG reliably bind synaptic receptors and penetrate around 10-15µm in depth in live tissue. However, the silver enhancement was only reaching the surface of the slices. We show that permeabilization with triton is highly effective at increasing the in depth-gold amplification and that the membrane integrity is well preserved. Finally, we also apply high-resolution electron tomography, thus providing important information about the 3D organization of surface AMPA receptors in synapses at the nanoscale.


Subject(s)
Hippocampus , Receptors, AMPA , Synapses , Animals , Mice , Hippocampus/metabolism , Hippocampus/cytology , Receptors, AMPA/metabolism , Synapses/metabolism , Synapses/ultrastructure , Membrane Proteins/metabolism , Gold/chemistry , Microscopy, Electron/methods , Fluorescent Dyes/chemistry , Fluorescent Dyes/metabolism
3.
Mol Pain ; 20: 17448069241258110, 2024.
Article in English | MEDLINE | ID: mdl-38744422

ABSTRACT

Recent studies using different experimental approaches demonstrate that silent synapses may exist in the adult cortex including the sensory cortex and anterior cingulate cortex (ACC). The postsynaptic form of long-term potentiation (LTP) in the ACC recruits some of these silent synapses and the activity of calcium-stimulated adenylyl cyclases (ACs) is required for such recruitment. It is unknown if the chemical activation of ACs may recruit silent synapses. In this study, we found that activation of ACs contributed to synaptic potentiation in the ACC of adult mice. Forskolin, a selective activator of ACs, recruited silent responses in the ACC of adult mice. The recruitment was long-lasting. Interestingly, the effect of forskolin was not universal, some silent synapses did not undergo potentiation or recruitment. These findings suggest that these adult cortical synapses are not homogenous. The application of a selective calcium-permeable AMPA receptor inhibitor 1-naphthyl acetyl spermine (NASPM) reversed the potentiation and the recruitment of silent responses, indicating that the AMPA receptor is required. Our results strongly suggest that the AC-dependent postsynaptic AMPA receptor contributes to the recruitment of silent responses at cortical LTP.


Subject(s)
Adenylyl Cyclases , Colforsin , Gyrus Cinguli , Long-Term Potentiation , Animals , Mice , Gyrus Cinguli/drug effects , Gyrus Cinguli/metabolism , Colforsin/pharmacology , Long-Term Potentiation/drug effects , Adenylyl Cyclases/metabolism , Male , Receptors, AMPA/metabolism , Mice, Inbred C57BL , Synapses/drug effects , Synapses/metabolism , Calcium/metabolism
4.
Neurol Neuroimmunol Neuroinflamm ; 11(4): e200254, 2024 Jul.
Article in English | MEDLINE | ID: mdl-38728609

ABSTRACT

OBJECTIVES: We report on the therapeutic management of early-onset severe neurologic symptoms in cytotoxic T lymphocyte antigen-4 haploinsufficiency (CTLA-4h) and the presence of antibodies to the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) as an important finding. METHODS: This is a case report from a Dutch academic hospital. Repeated clinical examinations, repeated brain MRI and extended diagnostics on serum and CSF were performed. We used the CARE checklist. RESULTS: A 7-year-old boy was diagnosed with CTLA-4h based on family screening. On diagnosis, he had mild chronic diarrhea and autism spectrum disorder, but no abnormalities in extensive laboratory screening. Six months later, he presented with sudden-onset autoimmune encephalitis. Repeated brain MRI revealed no abnormalities, but immunohistochemistry analysis on serum and CSF showed the presence of AMPAR antibodies. Treatment was initially focused on immunomodulation and targeted CTLA-4 replacement therapy. Because of the persistent fluctuating cerebellar and neuropsychiatric symptoms and the potential clinical significance of the AMPAR antibodies, treatment was intensified with repetition of first-line immunomodulation and rituximab. This combined therapy resulted in sustained clinical improvement and served as a bridge to curative hematopoietic stem cell transplantation. DISCUSSION: This case illustrates the rare early onset of autoimmune encephalitis and presence of AMPAR antibodies in CTLA-4h. Targeted CTLA-4 replacement therapy resulted in a partial response. However, awaiting its optimal therapeutic effect, refractory CNS symptoms required intensification of immunomodulation. The identification of AMPAR antibodies guided our treatment decisions. CLASSIFICATION OF EVIDENCE: This provides Class IV evidence. It is a single observational study without controls.


Subject(s)
Autoantibodies , CTLA-4 Antigen , Encephalitis , Haploinsufficiency , Hashimoto Disease , Receptors, AMPA , Humans , Male , Child , Encephalitis/diagnosis , Encephalitis/drug therapy , Encephalitis/immunology , Hashimoto Disease/diagnosis , Hashimoto Disease/drug therapy , Autoantibodies/blood , Autoantibodies/cerebrospinal fluid , Receptors, AMPA/immunology , Rituximab/administration & dosage , Rituximab/therapeutic use , Immunologic Factors
5.
ACS Chem Neurosci ; 15(11): 2334-2349, 2024 Jun 05.
Article in English | MEDLINE | ID: mdl-38747411

ABSTRACT

Parkinson's disease (PD) is a significant health issue because it gradually damages the nervous system. α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors play a significant role in the development of PD. The current investigation employed hybrid benzodioxole-propanamide (BDZ-P) compounds to get information on AMPA receptors, analyze their biochemical and biophysical properties, and assess their neuroprotective effects. Examining the biophysical characteristics of all the subunits of the AMPA receptor offers insights into the impact of BDZ-P on the desensitization and deactivation rate. It demonstrates a partial improvement in the locomotor capacities in a mouse model of Parkinson's disease. In addition, the in vivo experiment assessed the locomotor activity by utilizing the open-field test. Our findings demonstrated that BDZ-P7 stands out with its remarkable potency, inhibiting the GluA2 subunit nearly 8-fold with an IC50 of 3.03 µM, GluA1/2 by 7.5-fold with an IC50 of 3.14 µM, GluA2/3 by nearly 7-fold with an IC50 of 3.19 µM, and GluA1 by 6.5-fold with an IC50 of 3.2 µM, significantly impacting the desensitization and deactivation rate of the AMPA receptor. BDZ-P7 showed an in vivo impact of partially reinstating locomotor abilities in a mouse model of PD. The results above suggest that the BDZ-P7 compounds show great promise as top contenders for the development of novel neuroprotective therapies.


Subject(s)
Neuroprotective Agents , Receptors, AMPA , Receptors, AMPA/metabolism , Receptors, AMPA/drug effects , Animals , Neuroprotective Agents/pharmacology , Mice , Parkinson Disease/drug therapy , Parkinson Disease/metabolism , Mice, Inbred C57BL , Male , Humans , Disease Models, Animal
6.
Article in English | MEDLINE | ID: mdl-38692472

ABSTRACT

Stress exposure can lead to post-traumatic stress disorder (PTSD) in male and female rats. Social-Single Prolonged Stress (SPS) protocol has been considered a potential PTSD model. This study aimed to pharmacologically validate the Social-SPS as a PTSD model in male and female rats. Male and female Wistar rats (60-day-old) were exposed to Social-SPS protocol and treated with fluoxetine (10 mg/Kg) or saline solution intraperitoneally 24 h before euthanasia. Two cohorts of animals were used; for cohort 1, male and female rats were still undisturbed until day 7 post-Social-SPS exposure, underwent locomotor and conditioned fear behaviors, and were euthanized on day 9. Animals of cohort 2 were subjected to the same protocol but were re-exposed to contextual fear behavior on day 14. Results showed that fluoxetine-treated rats gained less body weight than control and Social-SPS in both sexes. Social-SPS effectively increased the freezing time in male and female rats on day eight but not on day fourteen. Fluoxetine blocked the increase of freezing in male and female rats on day 8. Different mechanisms for fear behavior were observed in males, such as Social-SPS increased levels of glucocorticoid receptors and Beclin-1 in the amygdala. Social-SPS was shown to increase the levels of NMDA2A, GluR-1, PSD-95, and CAMKII in the amygdala of female rats. No alterations were observed in the amygdala of rats on day fourteen. The study revealed that Social-SPS is a potential PTSD protocol applicable to both male and female rats.


Subject(s)
Amygdala , Fear , Fluoxetine , Rats, Wistar , Stress, Psychological , Animals , Male , Female , Fear/drug effects , Fear/physiology , Fluoxetine/pharmacology , Amygdala/drug effects , Amygdala/metabolism , Stress, Psychological/metabolism , Rats , Disease Models, Animal , Stress Disorders, Post-Traumatic/metabolism , Stress Disorders, Post-Traumatic/psychology , Conditioning, Classical/drug effects , Conditioning, Classical/physiology , Conditioning, Psychological/drug effects , Conditioning, Psychological/physiology , Selective Serotonin Reuptake Inhibitors/pharmacology , Disks Large Homolog 4 Protein , Receptors, AMPA
7.
Cell Rep ; 43(4): 114025, 2024 Apr 23.
Article in English | MEDLINE | ID: mdl-38564333

ABSTRACT

Type I spiral ganglion neurons (SGNs) convey sound information to the central auditory pathway by forming synapses with inner hair cells (IHCs) in the mammalian cochlea. The molecular mechanisms regulating the formation of the post-synaptic density (PSD) in the SGN afferent terminals are still unclear. Here, we demonstrate that brain-specific angiogenesis inhibitor 1 (BAI1) is required for the clustering of AMPA receptors GluR2-4 (glutamate receptors 2-4) at the PSD. Adult Bai1-deficient mice have functional IHCs but fail to transmit information to the SGNs, leading to highly raised hearing thresholds. Despite the almost complete absence of AMPA receptor subunits, the SGN fibers innervating the IHCs do not degenerate. Furthermore, we show that AMPA receptors are still expressed in the cochlea of Bai1-deficient mice, highlighting a role for BAI1 in trafficking or anchoring GluR2-4 to the PSDs. These findings identify molecular and functional mechanisms required for sound encoding at cochlear ribbon synapses.


Subject(s)
Cochlea , Hearing , Post-Synaptic Density , Receptors, AMPA , Receptors, G-Protein-Coupled , Spiral Ganglion , Animals , Receptors, AMPA/metabolism , Mice , Spiral Ganglion/metabolism , Hearing/physiology , Cochlea/metabolism , Post-Synaptic Density/metabolism , Mice, Knockout , Hair Cells, Auditory, Inner/metabolism , Mice, Inbred C57BL , Synapses/metabolism
8.
Sci Signal ; 17(834): eadj6603, 2024 Apr 30.
Article in English | MEDLINE | ID: mdl-38687825

ABSTRACT

The localization, number, and function of postsynaptic AMPA-type glutamate receptors (AMPARs) are crucial for synaptic plasticity, a cellular correlate for learning and memory. The Hippo pathway member WWC1 is an important component of AMPAR-containing protein complexes. However, the availability of WWC1 is constrained by its interaction with the Hippo pathway kinases LATS1 and LATS2 (LATS1/2). Here, we explored the biochemical regulation of this interaction and found that it is pharmacologically targetable in vivo. In primary hippocampal neurons, phosphorylation of LATS1/2 by the upstream kinases MST1 and MST2 (MST1/2) enhanced the interaction between WWC1 and LATS1/2, which sequestered WWC1. Pharmacologically inhibiting MST1/2 in male mice and in human brain-derived organoids promoted the dissociation of WWC1 from LATS1/2, leading to an increase in WWC1 in AMPAR-containing complexes. MST1/2 inhibition enhanced synaptic transmission in mouse hippocampal brain slices and improved cognition in healthy male mice and in male mouse models of Alzheimer's disease and aging. Thus, compounds that disrupt the interaction between WWC1 and LATS1/2 might be explored for development as cognitive enhancers.


Subject(s)
Hippocampus , Intracellular Signaling Peptides and Proteins , Neuronal Plasticity , Phosphoproteins , Protein Serine-Threonine Kinases , Receptors, AMPA , Animals , Protein Serine-Threonine Kinases/metabolism , Protein Serine-Threonine Kinases/genetics , Male , Humans , Receptors, AMPA/metabolism , Receptors, AMPA/genetics , Mice , Neuronal Plasticity/physiology , Hippocampus/metabolism , Hippo Signaling Pathway , Serine-Threonine Kinase 3 , Signal Transduction , Memory/physiology , Tumor Suppressor Proteins/metabolism , Tumor Suppressor Proteins/genetics , Hepatocyte Growth Factor/metabolism , Mice, Inbred C57BL , Alzheimer Disease/metabolism , Phosphorylation , Neurons/metabolism
9.
Science ; 384(6694): 470-475, 2024 Apr 26.
Article in English | MEDLINE | ID: mdl-38662824

ABSTRACT

Behavior is critical for animal survival and reproduction, and possibly for diversification and evolutionary radiation. However, the genetics behind adaptive variation in behavior are poorly understood. In this work, we examined a fundamental and widespread behavioral trait, exploratory behavior, in one of the largest adaptive radiations on Earth, the cichlid fishes of Lake Tanganyika. By integrating quantitative behavioral data from 57 cichlid species (702 wild-caught individuals) with high-resolution ecomorphological and genomic information, we show that exploratory behavior is linked to macrohabitat niche adaptations in Tanganyikan cichlids. Furthermore, we uncovered a correlation between the genotypes at a single-nucleotide polymorphism upstream of the AMPA glutamate-receptor regulatory gene cacng5b and variation in exploratory tendency. We validated this association using behavioral predictions with a neural network approach and CRISPR-Cas9 genome editing.


Subject(s)
Adaptation, Physiological , Behavior, Animal , Cichlids , Exploratory Behavior , Receptors, AMPA , Animals , Adaptation, Physiological/genetics , Cichlids/genetics , Cichlids/physiology , CRISPR-Cas Systems , Ecosystem , Gene Editing , Genotype , Lakes , Polymorphism, Single Nucleotide , Receptors, AMPA/genetics
10.
Proc Natl Acad Sci U S A ; 121(18): e2316819121, 2024 04 30.
Article in English | MEDLINE | ID: mdl-38657042

ABSTRACT

Posttranslational modifications regulate the properties and abundance of synaptic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors that mediate fast excitatory synaptic transmission and synaptic plasticity in the central nervous system. During long-term depression (LTD), protein tyrosine phosphatases (PTPs) dephosphorylate tyrosine residues in the C-terminal tail of AMPA receptor GluA2 subunit, which is essential for GluA2 endocytosis and group I metabotropic glutamate receptor (mGluR)-dependent LTD. However, as a selective downstream effector of mGluRs, the mGluR-dependent PTP responsible for GluA2 tyrosine dephosphorylation remains elusive at Schaffer collateral (SC)-CA1 synapses. In the present study, we find that mGluR5 stimulation activates Src homology 2 (SH2) domain-containing phosphatase 2 (SHP2) by increasing phospho-Y542 levels in SHP2. Under steady-state conditions, SHP2 plays a protective role in stabilizing phospho-Y869 of GluA2 by directly interacting with GluA2 phosphorylated at Y869, without affecting GluA2 phospho-Y876 levels. Upon mGluR5 stimulation, SHP2 dephosphorylates GluA2 at Y869 and Y876, resulting in GluA2 endocytosis and mGluR-LTD. Our results establish SHP2 as a downstream effector of mGluR5 and indicate a dual action of SHP2 in regulating GluA2 tyrosine phosphorylation and function. Given the implications of mGluR5 and SHP2 in synaptic pathophysiology, we propose SHP2 as a promising therapeutic target for neurodevelopmental and autism spectrum disorders.


Subject(s)
Endocytosis , Long-Term Synaptic Depression , Protein Tyrosine Phosphatase, Non-Receptor Type 11 , Receptors, AMPA , Receptors, Metabotropic Glutamate , Receptors, AMPA/metabolism , Animals , Phosphorylation , Endocytosis/physiology , Long-Term Synaptic Depression/physiology , Receptors, Metabotropic Glutamate/metabolism , Protein Tyrosine Phosphatase, Non-Receptor Type 11/metabolism , Protein Tyrosine Phosphatase, Non-Receptor Type 11/genetics , Rats , Tyrosine/metabolism , Receptor, Metabotropic Glutamate 5/metabolism , Synapses/metabolism , Mice , Humans , Neurons/metabolism
11.
Neuropharmacology ; 253: 109963, 2024 Aug 01.
Article in English | MEDLINE | ID: mdl-38657945

ABSTRACT

Valproic acid (VPA) is an effective and commonly prescribed drug for epilepsy and bipolar disorder. However, children born from mothers treated with VPA during pregnancy exhibit an increased incidence of autism spectrum disorder (ASD). Although VPA may impair brain development at the cellular level, the mechanism of VPA-induced ASD has not been completely addressed. A previous study has found that VPA treatment strongly reduces δ-catenin mRNA levels in cultured human neurons. δ-catenin is important for the control of glutamatergic synapses and is strongly associated with ASD. VPA inhibits dendritic morphogenesis in developing neurons, an effect that is also found in neurons lacking δ-catenin expression. We thus hypothesize that prenatal exposure to VPA significantly reduces δ-catenin levels in the brain, which impairs glutamatergic synapses to cause ASD. Here, we found that prenatal exposure to VPA markedly reduced δ-catenin levels in the brain of mouse pups. VPA treatment also impaired dendritic branching in developing mouse cortical neurons, which was partially reversed by elevating δ-catenin expression. Prenatal VPA exposure significantly reduced synaptic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor levels and postsynaptic density 95 (PSD95) in the brain of mouse pups, indicating dysfunctions in glutamatergic synaptic transmission. VPA exposure also significantly altered ultrasonic vocalization (USV) in newly born pups when they were isolated from their nest. Moreover, VPA-exposed pups show impaired hypothalamic response to isolation, which is required to produce animals' USVs following isolation from the nest. Therefore, these results suggest that VPA-induced ASD pathology can be mediated by the loss of δ-catenin functions.


Subject(s)
Animals, Newborn , Prenatal Exposure Delayed Effects , Valproic Acid , Vocalization, Animal , Animals , Valproic Acid/pharmacology , Valproic Acid/toxicity , Pregnancy , Prenatal Exposure Delayed Effects/chemically induced , Prenatal Exposure Delayed Effects/metabolism , Female , Vocalization, Animal/drug effects , Vocalization, Animal/physiology , Mice , Synapses/drug effects , Synapses/metabolism , Catenins/metabolism , Male , Mice, Inbred C57BL , Neurons/drug effects , Neurons/metabolism , Receptors, AMPA/metabolism , Brain/drug effects , Brain/metabolism , Autism Spectrum Disorder/chemically induced , Autism Spectrum Disorder/metabolism
12.
J Cell Sci ; 137(8)2024 Apr 15.
Article in English | MEDLINE | ID: mdl-38668720

ABSTRACT

Amyloid ß (Aß) is a central contributor to neuronal damage and cognitive impairment in Alzheimer's disease (AD). Aß disrupts AMPA receptor-mediated synaptic plasticity, a key factor in early AD progression. Numerous studies propose that Aß oligomers hinder synaptic plasticity, particularly long-term potentiation (LTP), by disrupting GluA1 (encoded by GRIA1) function, although the precise mechanism remains unclear. In this study, we demonstrate that Aß mediates the accumulation of GM1 ganglioside in lipid raft domains of cultured cells, and GluA1 exhibits preferential localization in lipid rafts via direct binding to GM1. Aß enhances the raft localization of GluA1 by increasing GM1 in these areas. Additionally, chemical LTP stimulation induces lipid raft-dependent GluA1 internalization in Aß-treated neurons, resulting in reduced cell surface and postsynaptic expression of GluA1. Consistent with this, disrupting lipid rafts and GluA1 localization in rafts rescues Aß-mediated suppression of hippocampal LTP. These findings unveil a novel functional deficit in GluA1 trafficking induced by Aß, providing new insights into the mechanism underlying AD-associated cognitive dysfunction.


Subject(s)
Alzheimer Disease , Amyloid beta-Peptides , Hippocampus , Long-Term Potentiation , Membrane Microdomains , Receptors, AMPA , Amyloid beta-Peptides/metabolism , Receptors, AMPA/metabolism , Membrane Microdomains/metabolism , Alzheimer Disease/metabolism , Alzheimer Disease/pathology , Animals , Hippocampus/metabolism , G(M1) Ganglioside/metabolism , Humans , Neurons/metabolism , Rats , Mice , Protein Transport
13.
Int Immunopharmacol ; 133: 112080, 2024 May 30.
Article in English | MEDLINE | ID: mdl-38613882

ABSTRACT

Myocardial infarction leads to myocardial inflammation and apoptosis, which are crucial factors leading to heart failure and cardiovascular dysfunction, eventually resulting in death. While the inhibition of AMPA receptors mitigates inflammation and tissue apoptosis, the effectiveness of this inhibition in the pathophysiological processes of myocardial infarction remains unclear. This study investigated the role of AMPA receptor inhibition in myocardial infarction and elucidated the underlying mechanisms. This study established a myocardial infarction model by ligating the left anterior descending branch of the coronary artery in Sprague-Dawley rats. The findings suggested that injecting the AMPA receptor antagonist NBQX into myocardial infarction rats effectively alleviated cardiac inflammation, myocardial necrosis, and apoptosis and improved their cardiac contractile function. Conversely, injecting the AMPA receptor agonist CX546 into infarcted rats exacerbated the symptoms and tissue damage, as reflected by histopathology. This agonist also stimulated the TLR4/NF-κB pathway, further deteriorating cardiac function. Furthermore, the investigations revealed that AMPA receptor inhibition hindered the nuclear translocation of P65, blocking its downstream signaling pathway and attenuating tissue inflammation. In summary, this study affirmed the potential of AMPA receptor inhibition in countering inflammation and tissue apoptosis after myocardial infarction, making it a promising therapeutic target for mitigating myocardial infarction.


Subject(s)
Apoptosis , Myocardial Infarction , Receptors, AMPA , Signal Transduction , Animals , Humans , Male , Rats , Apoptosis/drug effects , Disease Models, Animal , Inflammation/drug therapy , Myocardial Infarction/drug therapy , Myocardial Infarction/pathology , Myocardial Infarction/metabolism , Myocardium/pathology , Myocardium/metabolism , NF-kappa B/metabolism , Rats, Sprague-Dawley , Receptors, AMPA/antagonists & inhibitors , Receptors, AMPA/metabolism , Signal Transduction/drug effects , Toll-Like Receptor 4/metabolism , Toll-Like Receptor 4/antagonists & inhibitors
14.
J Physiol ; 602(10): 2179-2197, 2024 May.
Article in English | MEDLINE | ID: mdl-38630836

ABSTRACT

Hypertension is a major adverse effect of calcineurin inhibitors, such as tacrolimus (FK506) and cyclosporine, used clinically as immunosuppressants. Calcineurin inhibitor-induced hypertension (CIH) is linked to augmented sympathetic output from the hypothalamic paraventricular nucleus (PVN). GluA2-lacking, Ca2+-permeable AMPA receptors (CP-AMPARs) are a key feature of glutamatergic synaptic plasticity, yet their role in CIH remains elusive. Here, we found that systemic administration of FK506 in rats significantly increased serine phosphorylation of GluA1 and GluA2 in PVN synaptosomes. Strikingly, FK506 treatment reduced GluA1/GluA2 heteromers in both synaptosomes and endoplasmic reticulum-enriched fractions from the PVN. Blocking CP-AMPARs with IEM-1460 induced a larger reduction of AMPAR-mediated excitatory postsynaptic current (AMPAR-EPSC) amplitudes in retrogradely labelled, spinally projecting PVN neurons in FK506-treated rats than in vehicle-treated rats. Furthermore, FK506 treatment shifted the current-voltage relationship of AMPAR-EPSCs from linear to inward rectification in labelled PVN neurons. FK506 treatment profoundly enhanced physical interactions of α2δ-1 with GluA1 and GluA2 in the PVN. Inhibiting α2δ-1 with gabapentin, α2δ-1 genetic knockout, or disrupting α2δ-1-AMPAR interactions with an α2δ-1 C terminus peptide restored GluA1/GluA2 heteromers in the PVN and diminished inward rectification of AMPAR-EPSCs in labelled PVN neurons induced by FK506 treatment. Additionally, microinjection of IEM-1460 or α2δ-1 C terminus peptide into the PVN reduced renal sympathetic nerve discharges and arterial blood pressure elevated in FK506-treated rats but not in vehicle-treated rats. Thus, calcineurin in the hypothalamus constitutively regulates AMPAR subunit composition and phenotypes by controlling GluA1/GluA2 interactions with α2δ-1. Synaptic CP-AMPARs in PVN presympathetic neurons contribute to augmented sympathetic outflow in CIH. KEY POINTS: Systemic treatment with the calcineurin inhibitor increases serine phosphorylation of synaptic GluA1 and GluA2 in the PVN. Calcineurin inhibition enhances the prevalence of postsynaptic Ca2+-permeable AMPARs in PVN presympathetic neurons. Calcineurin inhibition potentiates α2δ-1 interactions with GluA1 and GluA2, disrupting intracellular assembly of GluA1/GluA2 heterotetramers in the PVN. Blocking Ca2+-permeable AMPARs or α2δ-1-AMPAR interactions in the PVN attenuates sympathetic outflow augmented by the calcineurin inhibitor.


Subject(s)
Calcineurin , Neurons , Paraventricular Hypothalamic Nucleus , Rats, Sprague-Dawley , Receptors, AMPA , Tacrolimus , Animals , Receptors, AMPA/metabolism , Receptors, AMPA/physiology , Calcineurin/metabolism , Male , Tacrolimus/pharmacology , Rats , Neurons/physiology , Neurons/drug effects , Neurons/metabolism , Paraventricular Hypothalamic Nucleus/physiology , Paraventricular Hypothalamic Nucleus/metabolism , Paraventricular Hypothalamic Nucleus/drug effects , Calcium/metabolism , Excitatory Postsynaptic Potentials/physiology , Excitatory Postsynaptic Potentials/drug effects , Calcineurin Inhibitors/pharmacology , Synapses/physiology , Synapses/drug effects , Synapses/metabolism
15.
J Chem Neuroanat ; 137: 102417, 2024 04.
Article in English | MEDLINE | ID: mdl-38570170

ABSTRACT

OBJECTIVE: The distribution and role of NMDA receptors is unclear in the afferent signaling complex of the cochlea. The present study aimed to examine the distribution of NMDA receptors in cochlear afferent signaling complex of the adult mouse, and their relationship with ribbon synapses of inner hair cells (IHCs) and GABAergic efferent terminals of the lateral olivocochlear (LOC). METHODS: Immunofluorescence staining in combination with confocal microscopy was used to investigate the distribution of glutamatergic NMDA and AMPA receptors in afferent terminals of SGNs, and their relationship with ribbon synapses of IHCs and GABAergic efferent terminals of LOC. RESULTS: Terminals with AMPA receptors along with Ribbons of IHC formed afferent synapses in the basal pole of IHCs, and those with NMDA receptors were mainly distributed longitudinally in the IHCs nuclei region. Significant difference was found in the distribution of NMDA and AMPA receptors in IHC afferent signaling complex (P<0.05). Some GABAergic terminals colocalized with NMDA receptors at the IHC nucleus region (P>0.05). CONCLUSION: There is significant difference in the distribution of NMDA and AMPA receptors in cochlear afferent signaling complex. NMDA receptors are present in the extra-synaptic region of ribbon synapses of IHCs, and they are related to GABA efferent terminals of the afferent signaling complex.


Subject(s)
Hair Cells, Auditory, Inner , Receptors, AMPA , Receptors, N-Methyl-D-Aspartate , Synapses , Animals , Hair Cells, Auditory, Inner/metabolism , Mice , Receptors, N-Methyl-D-Aspartate/metabolism , Synapses/metabolism , Receptors, AMPA/metabolism , Cochlea/metabolism , Male
16.
Mol Ther ; 32(6): 1721-1738, 2024 Jun 05.
Article in English | MEDLINE | ID: mdl-38566414

ABSTRACT

Recombinant adeno-associated viruses (AAVs) allow rapid and efficient gene delivery to the nervous system, are widely used in neuroscience research, and are the basis of FDA-approved neuron-targeting gene therapies. Here we find that an innate immune response to the AAV genome reduces dendritic length and complexity and disrupts synaptic transmission in mouse somatosensory cortex. Dendritic loss is apparent 3 weeks after injection of experimentally relevant viral titers, is not restricted to a particular capsid serotype, transgene, promoter, or production facility, and cannot be explained by responses to surgery or transgene expression. AAV-associated dendritic loss is accompanied by a decrease in the frequency and amplitude of miniature excitatory postsynaptic currents and an increase in the proportion of GluA2-lacking, calcium-permeable AMPA receptors. The AAV genome is rich in unmethylated CpG DNA, which is recognized by the innate immunoreceptor Toll-like receptor 9 (TLR9), and acutely blocking TLR9 preserves dendritic complexity and AMPA receptor subunit composition in AAV-injected mice. These results reveal unexpected impacts of an immune response to the AAV genome on neuronal structure and function and identify approaches to improve the safety and efficacy of AAV-mediated gene delivery in the nervous system.


Subject(s)
Dendrites , Dependovirus , Genetic Vectors , Immunity, Innate , Synaptic Transmission , Toll-Like Receptor 9 , Animals , Dependovirus/genetics , Mice , Dendrites/metabolism , Toll-Like Receptor 9/metabolism , Toll-Like Receptor 9/genetics , Genetic Vectors/genetics , Genetic Vectors/administration & dosage , Receptors, AMPA/genetics , Receptors, AMPA/metabolism , Somatosensory Cortex/metabolism , Somatosensory Cortex/immunology , Genome, Viral
17.
Neurobiol Dis ; 194: 106471, 2024 May.
Article in English | MEDLINE | ID: mdl-38461868

ABSTRACT

Emerging evidence has implicated an important role of synapse-associated protein-97 (SAP97)-regulated GluA1-containing AMPARs membrane trafficking in cocaine restate and in contextual episodic memory of schizophrenia. Herein, we investigated the role of SAP97 in neuropathic pain following lumbar 5 spinal nerve transection (SNT) in rats. Our results showed that SNT led to upregulation of SAP97, enhanced the interaction between SAP97 and GluA1, and increased GluA1-containing AMPARs membrane trafficking in the dorsal horn. Microinjection of AAV-EGFP-SAP97 shRNA in lumbar 5 spinal dorsal horn inhibited SAP97 production, decreased SAP97-GluA1 interaction, reduced the membrane trafficking of GluA1-containing AMPARs, and partially attenuated neuropathic pain following SNT. Intrathecal injections of SAP97 siRNA or NASPM, an antagonist of GluA1-containing AMPARs, also partially reversed neuropathic pain on day 7, but not on day 14, after SNT. Spinal overexpression of SAP97 by AAV-EGFP-SAP97 enhanced SAP97-GluA1 interaction, increased the membrane insertion of GluA1-containing AMPARs, and induced abnormal pain in naïve rats. In addition, treatment with SAP97 siRNA or NASPM i.t. injection alleviated SNT-induced allodynia and hyperalgesia and exhibited a longer effect in female rats. Together, our results indicate that the SNT-induced upregulation of SAP97 via promoting GluA1-containing AMPARs membrane trafficking in the dorsal horn contributes to the pathogenesis of neuropathic pain. Targeting spinal SAP97 might be a promising therapeutic strategy to treatment of chronic pain.


Subject(s)
Neuralgia , Receptors, AMPA , Spermine , Animals , Female , Rats , Hyperalgesia , Rats, Sprague-Dawley , Receptors, AMPA/metabolism , RNA, Small Interfering , Spermine/analogs & derivatives , Spinal Cord Dorsal Horn/metabolism , Spinal Nerves , Up-Regulation
18.
Biochem Biophys Res Commun ; 709: 149803, 2024 May 21.
Article in English | MEDLINE | ID: mdl-38552556

ABSTRACT

Synaptic plasticity is essential for memory encoding and stabilization of neural network activity. Plasticity is impaired in neurodegenerative conditions including Alzheimer disease (AD). A central factor in AD is amyloid precursor protein (APP). Previous studies have suggested APP involvement in synaptic plasticity, but physiological roles of APP are not well understood. Here, we identified combinatorial phosphorylation sites within APP that regulate AMPA receptor trafficking during different forms of synaptic plasticity. Dual phosphorylation sites at threonine-668/serine-675 of APP promoted endocytosis of the GluA2 subunit of AMPA receptors during homeostatic synaptic plasticity. APP was also required for GluA2 internalization during NMDA receptor-dependent long-term depression, albeit via a distinct pair of phosphoresidues at serine-655/threonine-686. These data implicate APP as a central gate for AMPA receptor internalization during distinct forms of plasticity, unlocked by specific combinations of phosphoresidues, and suggest that APP may serve broad functions in learning and memory.


Subject(s)
Alzheimer Disease , Receptors, AMPA , Humans , Receptors, AMPA/metabolism , Amyloid beta-Protein Precursor/metabolism , Phosphorylation , Neuronal Plasticity/physiology , Alzheimer Disease/metabolism , Serine/metabolism , Threonine/metabolism , Synapses/metabolism
19.
Synapse ; 78(2): e22289, 2024 Mar.
Article in English | MEDLINE | ID: mdl-38436644

ABSTRACT

Epileptic seizures are seen as a result of changing excitability balance depending on the deterioration in synaptic plasticity in the brain. Neuroplastin, and its related molecules which are known to play a role in synaptic plasticity, neurotransmitter activities that provide balance of excitability and, different neurological diseases, have not been studied before in epilepsy. In this study, a total of 34 Sprague-Dawley male and female rats, 2 months old, weighing 250-300 g were used. The epilepsy model in rats was made via pentylenetetrazole (PTZ). After the completion of the experimental procedure, the brain tissue of the rats were taken and the histopathological changes in the hippocampus and cortex parts and the brain stem were investigated, as well as the immunoreactivity of the proteins related to the immunohistochemical methods. As a result of the histopathological evaluation, it was determined that neuron degeneration and the number of dilated blood vessels in the hippocampus, frontal cortex, and brain stem were higher in the PTZ status epilepticus (SE) groups than in the control groups. It was observed that neuroplastin and related proteins TNF receptor-associated factor 6 (TRAF6), Gamma amino butyric acid type A receptors [(GABA(A)], and plasma membrane Ca2+ ATPase (PMCA) protein immunoreactivity levels increased especially in the male hippocampus, and only AMPA receptor subunit type 1 (GluA1) immunoreactivity decreased, unlike other proteins. We believe this may be caused by a problem in the mechanisms regulating the interaction of neuroplastin and GluA1 and may cause problems in synaptic plasticity in the experimental epilepsy model. It may be useful to elucidate this mechanism and target GluA1 when determining treatment strategies.


Subject(s)
Epilepsy , Animals , Female , Male , Rats , Brain Stem/metabolism , Epilepsy/chemically induced , Epilepsy/genetics , Hippocampus/metabolism , Pentylenetetrazole , Rats, Sprague-Dawley , Receptors, GABA-A/genetics , TNF Receptor-Associated Factor 6/genetics , Plasma Membrane Calcium-Transporting ATPases/genetics , Receptors, AMPA/genetics , Cerebral Cortex/metabolism
20.
eNeuro ; 11(4)2024 Apr.
Article in English | MEDLINE | ID: mdl-38519128

ABSTRACT

As the global elderly population grows, age-related cognitive decline is becoming an increasingly significant healthcare issue, often leading to various neuropsychiatric disorders. Among the many molecular players involved in memory, AMPA-type glutamate receptors are known to regulate learning and memory, but how their dynamics change with age and affect memory decline is not well understood. Here, we examined the in vivo properties of the AMPA-type glutamate receptor GLR-1 in the AVA interneuron of the Caenorhabditis elegans nervous system during physiological aging. We found that both total and membrane-bound GLR-1 receptor levels decrease with age in wild-type worms, regardless of their location along the axon. Using fluorescence recovery after photobleaching, we also demonstrated that a reduction in GLR-1 abundance correlates with decreased local, synaptic GLR-1 receptor dynamics. Importantly, we found that reduced GLR-1 levels strongly correlate with the age-related decline in short-term associative memory. Genetic manipulation of GLR-1 stability, by either deleting msi-1 or expressing a ubiquitination-defective GLR-1 (4KR) variant, prevented this age-related reduction in receptor abundance and improved the short-term memory performance in older animals, which reached performance levels similar to those of young animals. Overall, our data indicate that AMPA-type glutamate receptor abundance and dynamics are key factors in maintaining memory function and that changes in these parameters are linked to age-dependent short-term memory decline.


Subject(s)
Caenorhabditis elegans Proteins , Animals , alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid , Caenorhabditis elegans/physiology , Caenorhabditis elegans Proteins/metabolism , Memory, Short-Term , Mutation , Receptors, AMPA , Receptors, Glutamate/genetics , Receptors, Glutamate/metabolism
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