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International Journal of Molecular... Sep 2023Glutamate ionotropic receptors mediate fast excitation processes in the central nervous system of vertebrates and play an important role in synaptic plasticity,...
Glutamate ionotropic receptors mediate fast excitation processes in the central nervous system of vertebrates and play an important role in synaptic plasticity, learning, and memory. Here, we describe the action of two azobenene-containing compounds, AAQ (acrylamide-azobenzene-quaternary ammonium) and QAQ (quaternary ammonium-azobenzene-quaternary ammonium), which produced rapid and fully reversible light-dependent inhibition of glutamate ionotropic receptors. The compounds demonstrated voltage-dependent inhibition with only minor voltage-independent allosteric action. Calcium-impermeable AMPA receptors had weaker sensitivity compared to NMDA and calcium-permeable AMPA receptors. We further revealed that the compounds bound to NMDA and calcium-permeable AMPA receptors in different modes. They were able to enter the wide selectivity filter of AMPA receptors, and strong negative voltages caused permeation into the cytoplasm. The narrow selectivity filter of the NMDA receptors did not allow the molecules to bypass them; therefore, QAQ and AAQ bound to the shallow channel site and prevented channel closure by a foot-in-the-door mechanism. Computer simulations employing available AMPA and NMDA receptor structures readily reproduced the experimental findings, allowing for the structure-based design of more potent and selective drugs in the future. Thus, our work creates a framework for the development of light-sensitive blockers of calcium-permeable AMPA receptors, which are desirable tools for neuroscience.
Topics: Animals; Receptors, AMPA; Receptors, Ionotropic Glutamate; Ammonium Compounds; N-Methylaspartate; Calcium; Receptors, Glutamate; Receptors, N-Methyl-D-Aspartate; Glutamates
PubMed: 37762075
DOI: 10.3390/ijms241813773 -
BioEssays : News and Reviews in... Jul 2024Long-term potentiation (LTP) of excitatory synapses is a leading model to explain the concept of information storage in the brain. Multiple mechanisms contribute to LTP,... (Review)
Review
Long-term potentiation (LTP) of excitatory synapses is a leading model to explain the concept of information storage in the brain. Multiple mechanisms contribute to LTP, but central amongst them is an increased sensitivity of the postsynaptic membrane to neurotransmitter release. This sensitivity is predominantly determined by the abundance and localization of AMPA-type glutamate receptors (AMPARs). A combination of AMPAR structural data, super-resolution imaging of excitatory synapses, and an abundance of electrophysiological studies are providing an ever-clearer picture of how AMPARs are recruited and organized at synaptic junctions. Here, we review the latest insights into this process, and discuss how both cytoplasmic and extracellular receptor elements cooperate to tune the AMPAR response at the hippocampal CA1 synapse.
Topics: Receptors, AMPA; Animals; Humans; Synapses; Long-Term Potentiation; Synaptic Transmission; CA1 Region, Hippocampal
PubMed: 38693811
DOI: 10.1002/bies.202400006 -
Cellular and Molecular Neurobiology Aug 2023Abelson non-receptor tyrosine kinases (Abl1 and Abl2) are established cellular signaling proteins, implicated in cytoskeletal reorganization essential for modulation of...
Abelson non-receptor tyrosine kinases (Abl1 and Abl2) are established cellular signaling proteins, implicated in cytoskeletal reorganization essential for modulation of cell morphology and motility. During development of the central nervous system, Abl kinases play fundamental roles in neurulation and neurite outgrowth, relaying information from axon guidance cues and growth factor receptors to promote cytoskeletal rearrangements. In mature neurons, Abl kinases localize to pre- and postsynaptic compartments and are involved in regulation of synaptic stability and plasticity. Although emerging evidence indicates interchangeability of these isoforms in managing of cellular functions, in healthy adult neurons, Abl1 contribution is less elucidated, while Abl2 is required for optimal synaptic functioning. Our previous study demonstrated compartmentalization of Abl1 to the presynapse and Abl2 to the postsynapse and characterized their modulatory effect on spontaneous excitatory synaptic transmission. Here, we further delineate the role of Abl2 on regulation of the postsynaptic component of miniature excitatory postsynaptic current (mEPSC). Our findings show that both acute and prolonged activation of Abl2, in line with reduction of mEPSC amplitude, also decrease AMPA and NMDA current amplitudes. In contrast with the current-detrimental effect, prolonged Abl2 activity stabilizes spines, particularly contributing to maintenance of active synapses at distal (perhaps apical) segments of dendrites. Hence, we propose that attenuation of ion currents via ionotropic glutamatergic receptors by Abl2 kinase derives from either reduction of the receptor sensitivity for glutamate or is due to alteration of channel gating mechanisms. Abl2 and excitatory postsynapses: Abl2 expression level affects active excitatory synapse density on distal dendrites, while Abl2 activity impacts current density through AMPA and NMDA receptors.
Topics: alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Synaptic Transmission; Synapses; Neurons; Receptors, N-Methyl-D-Aspartate
PubMed: 36689065
DOI: 10.1007/s10571-023-01317-9 -
EMBO Reports Mar 2024Autoimmune responses against NMDA receptors (NMDAR) and GABA receptors (GABAR) can cause encephalitis, which has been described as feeling like one’s brain is on fire...
Autoimmune responses against NMDA receptors (NMDAR) and GABA receptors (GABAR) can cause encephalitis, which has been described as feeling like one’s brain is on fire (Dalmau et al, 2019). The molecular mechanisms of how the autoantibodies affect neuronal functions are incompletely defined. Hunter et al (2024) now describe effects of autoantibodies from patients against NMDARs and GABARs on the lateral mobility and thereby localization and function of NMDARs and GABARs as well as AMPA receptors (AMPARs), the main glutamatergic receptors that mediate basal synaptic transmission. The study provides evidence for crossover effects of autoantibodies on the opposite receptor that depend on neuronal activity and the interaction of NMDAR with the dopaminergic receptor D.
Topics: Brain; Autoantibodies
PubMed: 38418692
DOI: 10.1038/s44319-024-00094-w -
Biomedicine & Pharmacotherapy =... Dec 2023As a subclass of ionotropic glutamate receptors (iGluRs), α-amino-3-hydroxyl-5-methyl-4-isoxazolepropionic acid (AMPA) receptors have been implicated in various...
As a subclass of ionotropic glutamate receptors (iGluRs), α-amino-3-hydroxyl-5-methyl-4-isoxazolepropionic acid (AMPA) receptors have been implicated in various neurological disorders and neurodegenerative diseases. To further our understanding of AMPA receptor-related disorders in the central nervous system (CNS), it is important to be able to image and quantify AMPA receptors in vivo. In this study, we identified a novel F-containing AMPA positive allosteric modulator (PAM) 6 as a potential lead compound. Molecular docking studies and CNS PET multi-parameter optimization (MPO) analysis were used to predict the absorption, distribution, metabolism, and excretion (ADME) characteristics of 6 as a PET probe. The resulting PET probe, [F]6 (codename [F]AMPA-2109), was successfully radiolabeled and demonstrated excellent blood-brain barrier (BBB) permeability and high brain uptake in rodents and non-human primates. However, [F]6 did not show substantial specific binding in the rodent or non-human primate brain. Further medicinal chemistry efforts are necessary to improve specific binding, and our work may serve as a starting point for the design of novel F-labeled AMPA receptor-targeted PET radioligands aimed for clinical translation.
Topics: Animals; Receptors, AMPA; Thiadiazines; alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Molecular Docking Simulation; Brain; Positron-Emission Tomography; Rodentia
PubMed: 37925936
DOI: 10.1016/j.biopha.2023.115842 -
ELife Jul 2023Pathological loss-of-function mutations in cyclin-dependent kinase-like 5 () cause CDKL5 deficiency disorder (CDD), a rare and severe neurodevelopmental disorder...
Pathological loss-of-function mutations in cyclin-dependent kinase-like 5 () cause CDKL5 deficiency disorder (CDD), a rare and severe neurodevelopmental disorder associated with severe and medically refractory early-life epilepsy, motor, cognitive, visual, and autonomic disturbances in the absence of any structural brain pathology. Analysis of genetic variants in CDD has indicated that CDKL5 kinase function is central to disease pathology. encodes a serine-threonine kinase with significant homology to GSK3β, which has also been linked to synaptic function. Further, knock-out rodents have increased GSK3β activity and often increased long-term potentiation (LTP). Thus, development of a specific CDKL5 inhibitor must be careful to exclude cross-talk with GSK3β activity. We synthesized and characterized specific, high-affinity inhibitors of CDKL5 that do not have detectable activity for GSK3β. These compounds are very soluble in water but blood-brain barrier penetration is low. In rat hippocampal brain slices, acute inhibition of CDKL5 selectively reduces postsynaptic function of AMPA-type glutamate receptors in a dose-dependent manner. Acute inhibition of CDKL5 reduces hippocampal LTP. These studies provide new tools and insights into the role of CDKL5 as a newly appreciated key kinase necessary for synaptic plasticity. Comparisons to rodent knock-out studies suggest that compensatory changes have limited the understanding of the roles of CDKL5 in synaptic physiology, plasticity, and human neuropathology.
Topics: Animals; Mice; Humans; Glycogen Synthase Kinase 3 beta; Mice, Knockout; Protein Serine-Threonine Kinases; Hippocampus; Cyclin-Dependent Kinases
PubMed: 37490324
DOI: 10.7554/eLife.88206 -
The Journal of Physiology Sep 2023Kinesin family member 2C (KIF2C)/mitotic centromere-associated kinesin (MCAK), is thought to be oncogenic as it is involved in tumour progression and metastasis....
Kinesin family member 2C (KIF2C)/mitotic centromere-associated kinesin (MCAK), is thought to be oncogenic as it is involved in tumour progression and metastasis. Moreover, it also plays a part in neurodegenerative conditions like Alzheimer's disease and psychiatric disorders such as suicidal schizophrenia. Our previous study conducted on mice demonstrated that KIF2C is widely distributed in various regions of the brain, and is localized in synaptic spines. Additionally, it regulates microtubule dynamic properties through its own microtubule depolymerization activity, thereby affecting AMPA receptor transport and cognitive behaviour in mice. In this study, we show that KIF2C regulates the transport of mGlu1 receptors in Purkinje cells by binding to Rab8. KIF2C deficiency in Purkinje cells results in abnormal gait, reduced balance ability and motor incoordination in male mice. These data suggest that KIF2C is essential for maintaining normal transport and synaptic function of mGlu1 and motor coordination in mice. KEY POINTS: KIF2C is localized in synaptic spines of hippocampus neurons, and regulates excitatory transmission, synaptic plasticity and cognitive behaviour. KIF2C is extensively expressed in the cerebellum, and we investigated its functions in development and synaptic transmission of cerebellar Purkinje cells. KIF2C deficiency in Purkinje cells alters the expression of metabotropic glutamate receptor 1 (mGlu1) and the AMPA receptor GluA2 subunit at Purkinje cell synapses, and changes excitatory synaptic transmission, but not inhibitory transmission. KIF2C regulates the transport of mGlu1 receptors in Purkinje cells by binding to Rab8. KIF2C deficiency in Purkinje cells affects motor coordination, but not social behaviour in male mice.
Topics: Male; Animals; Mice; Purkinje Cells; Receptors, AMPA; Kinesins; Receptors, Metabotropic Glutamate; Cerebellum; Carrier Proteins; Synapses; Cell Cycle Proteins
PubMed: 37431690
DOI: 10.1113/JP284214 -
Stem Cell Reports Nov 2023Mechanisms that underlie homeostatic plasticity have been extensively investigated at single-cell levels in animal models, but are less well understood at the network...
Mechanisms that underlie homeostatic plasticity have been extensively investigated at single-cell levels in animal models, but are less well understood at the network level. Here, we used microelectrode arrays to characterize neuronal networks following induction of homeostatic plasticity in human induced pluripotent stem cell (hiPSC)-derived glutamatergic neurons co-cultured with rat astrocytes. Chronic suppression of neuronal activity through tetrodotoxin (TTX) elicited a time-dependent network re-arrangement. Increased expression of AMPA receptors and the elongation of axon initial segments were associated with increased network excitability following TTX treatment. Transcriptomic profiling of TTX-treated neurons revealed up-regulated genes related to extracellular matrix organization, while down-regulated genes related to cell communication; also astrocytic gene expression was found altered. Overall, our study shows that hiPSC-derived neuronal networks provide a reliable in vitro platform to measure and characterize homeostatic plasticity at network and single-cell levels; this platform can be extended to investigate altered homeostatic plasticity in brain disorders.
Topics: Humans; Rats; Animals; Cells, Cultured; Neuronal Plasticity; Induced Pluripotent Stem Cells; Neurons; Coculture Techniques; Tetrodotoxin
PubMed: 37863044
DOI: 10.1016/j.stemcr.2023.09.011 -
Cell Reports Aug 2023Synaptic zinc signaling modulates synaptic activity and is present in specific populations of cortical neurons, suggesting that synaptic zinc contributes to the...
Synaptic zinc signaling modulates synaptic activity and is present in specific populations of cortical neurons, suggesting that synaptic zinc contributes to the diversity of intracortical synaptic microcircuits and their functional specificity. To understand the role of zinc signaling in the cortex, we performed whole-cell patch-clamp recordings from intratelencephalic (IT)-type neurons and pyramidal tract (PT)-type neurons in layer 5 of the mouse auditory cortex during optogenetic stimulation of specific classes of presynaptic neurons. Our results show that synaptic zinc potentiates AMPA receptor (AMPAR) function in a synapse-specific manner. We performed in vivo 2-photon calcium imaging of the same classes of neurons in awake mice and found that changes in synaptic zinc can widen or sharpen the sound-frequency tuning bandwidth of IT-type neurons but only widen the tuning bandwidth of PT-type neurons. These results provide evidence for synapse- and cell-type-specific actions of synaptic zinc in the cortex.
Topics: Mice; Animals; Auditory Cortex; Receptors, AMPA; Zinc; Neurons; Synapses; Synaptic Transmission
PubMed: 37585291
DOI: 10.1016/j.celrep.2023.112932 -
Frontiers in Molecular Neuroscience 2023Accurate modelling of molecular changes in Alzheimer's disease (AD) dementia is crucial for understanding the mechanisms driving neuronal pathology and for developing...
INTRODUCTION
Accurate modelling of molecular changes in Alzheimer's disease (AD) dementia is crucial for understanding the mechanisms driving neuronal pathology and for developing treatments. Synaptic dysfunction has long been implicated as a mechanism underpinning memory dysfunction in AD and may result in part from changes in adenosine deaminase acting on RNA (ADAR) mediated RNA editing of the GluA2 subunit of AMPA receptors and changes in AMPA receptor function at the post synaptic cleft. However, few studies have investigated changes in proteins which influence RNA editing and notably, AD studies that focus on studying changes in protein expression, rather than changes in mRNA, often use traditional western blotting.
METHODS
Here, we demonstrate the value of automated capillary western blotting to investigate the protein expression of AMPA receptor subunits (GluA1-4), the ADAR RNA editing proteins (ADAR1-3), and proteins known to regulate RNA editing (PIN1, WWP2, FXR1P, and CREB1), in the J20 AD mouse model. We describe extensive optimisation and validation of the automated capillary western blotting method, demonstrating the use of total protein to normalise protein load, in addition to characterising the optimal protein/antibody concentrations to ensure accurate protein quantification. Following this, we assessed changes in proteins of interest in the hippocampus of 44-week-old J20 AD mice.
RESULTS
We observed an increase in the expression of ADAR1 p110 and GluA3 and a decrease in ADAR2 in the hippocampus of 44-week-old J20 mice. These changes signify a shift in the balance of proteins that play a critical role at the synapse. Regression analysis revealed unique J20-specific correlations between changes in AMPA receptor subunits, ADAR enzymes, and proteins that regulate ADAR stability in J20 mice, highlighting potential mechanisms mediating RNA-editing changes found in AD.
DISCUSSION
Our findings in J20 mice generally reflect changes seen in the human AD brain. This study underlines the importance of novel techniques, like automated capillary western blotting, to assess protein expression in AD. It also provides further evidence to support the hypothesis that a dysregulation in RNA editing-related proteins may play a role in the initiation and/or progression of AD.
PubMed: 38299128
DOI: 10.3389/fnmol.2023.1338065