Glycine Binding Sites of Presynaptic NMDA Receptors May Tonically Regulate Glutamate Release in the Rat Visual Cortex

2007 ◽  
Vol 97 (1) ◽  
pp. 817-823 ◽  
Author(s):  
Yan-Hai Li ◽  
Tai-Zhen Han
Keyword(s):  
Visual Cortex ◽  
Binding Site ◽  
Binding Sites ◽  
Pyramidal Neurons ◽  
Glutamate Release ◽  
Excitatory Neurotransmitter ◽  
Aspartate Receptor ◽  
Neurotransmitter Glutamate ◽  
Presynaptic Nmda Receptors ◽  
Nmda Receptor Blocker

In the CNS, activation of N-methyl-d-aspartate receptor (NMDA-R) glycine binding sites is a prerequisite for activation of postsynaptic NMDA-Rs by the excitatory neurotransmitter glutamate. Here we provide electrophysiological evidence that the glycine binding sites of presynaptic NMDA-Rs regulate glutamate release in layer II/III pyramidal neurons of the rat visual cortex. Specifically, our results reveal that the frequency of miniature excitatory postsynaptic currents is significantly reduced by 7-chloro-kynurenic acid (7-Cl KYNA), a NMDA-R glycine binding site antagonist, and glycine or d-serine reverses this effect. Similar results are obtained when the open-channel NMDA receptor blocker, MK-801, is included in the recording pipette. Our data indicate that the glycine binding site of postsynaptic NMDA-Rs is not saturated. Moreover, they suggest that presynaptic NMDA-Rs are located in layer II/III pyramidal neurons of the rat visual cortex and that the glycine binding site of presynaptic NMDA-Rs tonically regulates glutamate release.

scholarly journals Input-specific maturation of NMDAR-mediated transmission onto parvalbumin-expressing interneurons in layers 2/3 of the visual cortex

2018 ◽  
Vol 120 (6) ◽  
pp. 3063-3076 ◽  
Author(s):  
Camilo Ferrer ◽  
Helen Hsieh ◽  
Lonnie P. Wollmuth
Keyword(s):  
Visual Cortex ◽  
Critical Period ◽  
Pyramidal Neurons ◽  
Temporal Integration ◽  
Developmental Changes ◽  
Evoked Responses ◽  
Developmentally Regulated ◽  
Low Frequencies ◽  
Aspartate Receptor ◽  
Synaptic Responses

Parvalbumin-expressing (PV) GABAergic interneurons regulate local circuit dynamics. In terms of the excitation driving PV interneuron activity, the N-methyl-d-aspartate receptor (NMDAR)-mediated component onto PV interneurons tends to be smaller than that onto pyramidal neurons but makes a significant contribution to their physiology and development. In the visual cortex, PV interneurons mature during the critical period. We hypothesize that during the critical period, the NMDAR-mediated signaling and functional properties of glutamatergic synapses onto PV interneurons are developmentally regulated. We therefore compared the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR)- and NMDAR-mediated synaptic responses before (postnatal days 15–20, P15–P20), during (P25–P40), and after (P50–P60) the visual critical period. AMPAR miniature excitatory postsynaptic currents (mEPSCs) showed a developmental decrease in frequency, whereas NMDAR mEPSCs were absent or showed extremely low frequencies throughout development. For evoked responses, we consistently saw a NMDAR-mediated component, suggesting pre- or postsynaptic differences between evoked and spontaneous neurotransmission. Evoked responses showed input-specific developmental changes. For intralaminar inputs, the NMDAR-mediated component significantly decreased with development. This resulted in adult intralaminar inputs almost exclusively mediated by AMPARs, suited for the computation of synaptic inputs with precise timing, and likely having NMDAR-independent forms of plasticity. In contrast, interlaminar inputs maintained a stable NMDAR-mediated component throughout development but had a shift in the AMPAR paired-pulse ratio from depression to facilitation. Adult interlaminar inputs with facilitating AMPAR responses and a substantial NMDAR component would favor temporal integration of synaptic responses and could be modulated by NMDAR-dependent forms of plasticity. NEW & NOTEWORTHY We show for the first time input-specific developmental changes in the N-methyl-d-aspartate receptor component and short-term plasticity of the excitatory drive onto layers 2/3 parvalbumin-expressing (PV) interneurons in the visual cortex during the critical period. These developmental changes would lead to functionally distinct adult intralaminar and interlaminar glutamatergic inputs that would engage PV interneuron-mediated inhibition differently.

scholarly journals Mechanism and potential sites of potassium interaction with glutamate transporters

2020 ◽  
Vol 152 (10) ◽  
Author(s):  
Jiali Wang ◽  
Kaiqi Zhang ◽  
Puja Goyal ◽  
Christof Grewer
Keyword(s):  
Binding Site ◽  
Binding Sites ◽  
Glutamate Release ◽  
Indirect Evidence ◽  
Md Simulations ◽  
Glutamate Transporters ◽  
Site Directed Mutagenesis ◽  
Regulatory Function ◽  
Amino Acid Residues ◽  
Extracellular Side

In the mammalian glutamate transporters, countertransported intracellular K+ is essential for relocating the glutamate binding site to the extracellular side of the membrane. This K+-dependent process is believed to be rate limiting for the transport cycle. In contrast, extracellular K+ induces glutamate release upon transporter reversal. Here, we analyzed potential K+ binding sites using molecular dynamics (MD) simulations and site-directed mutagenesis. Two candidate sites were identified by spontaneous K+ binding in MD simulations, one site (K1 site) overlapping with the Na1 Na+ binding site and the K2 site being localized under hairpin loop 2 (HP2). Mutations to conserved amino acid residues in these sites resulted in several transporters that were defective in K+-induced reverse transport and which bound K+ with reduced apparent affinity compared with the wild-type transporter. However, external K+ interaction was abolished in only one mutant transporter EAAC1D454A in the K1 site. Our results, for the first time, directly demonstrate effects of K1-site mutations on K+ binding, in contrast to previous reports on K+ binding sites based on indirect evidence. We propose that K+ binding to the K1 site is responsible for catalyzing the relocation step, whereas binding to the K2 site may have an as-of-yet unidentified regulatory function.

Substrates for Coincidence Detection and Calcium Signaling for Induction of Synaptic Potentiation in the Neonatal Visual Cortex

2004 ◽  
Vol 91 (6) ◽  
pp. 2747-2764 ◽  
Author(s):  
Laura A. Schrader ◽  
Stephen P. Perrett ◽  
Lan Ye ◽  
Michael J. Friedlander
Keyword(s):  
Visual Cortex ◽  
Glutamate Receptors ◽  
Metabotropic Glutamate Receptors ◽  
Pyramidal Neurons ◽  
Glutamate Release ◽  
Long Term Potentiation ◽  
Coincidence Detection ◽  
Detection Mechanism ◽  
Group I ◽  
Layer 2

Regulation of the efficacy of synaptic transmission by activity-dependent processes has been implicated in learning and memory as well as in developmental processes. We previously described transient potentiation of excitatory synapses onto layer 2/3 pyramidal neurons in the visual cortex that is induced by coincident presynaptic stimulation and postsynaptic depolarization. In the adult visual cortex, activation of N-methyl-d-aspartate (NMDA) glutamate receptors is necessary to induce this plasticity. These receptors act as coincidence detectors, sensing presynaptic glutamate release and postsynaptic depolarization, and cause an influx of Ca2+ that is necessary for the potentiation. In the neurons of the neonatal visual cortex, on the other hand, coincident presynaptic stimulation and postsynaptic depolarization induce stable long-term potentiation (LTP). In addition, reduced but significant LTP can be induced in many neurons in the presence of the NMDA receptor (NMDAR) antagonist, 2-amino-5-phosphonovaleric acid despite the Ca2+ requirement. Therefore there must be an alternative postsynaptic Ca2+ source and coincidence detection mechanism linked to the LTP induction mechanism in the neonatal cortex operating in addition to NMDARs. In this study, we find that in layer 2/3 pyramidal neurons, release of Ca2+ from inositol trisphosphate (InsP3) receptor-mediated intracellular stores and influx through voltage-gated Ca2+ channels (VGCCs) provide alternative postsynaptic Ca2+ sources. We hypothesize that InsP3Rs are coincidence detectors, sensing presynaptic glutamate release through linkage with group I metabotropic glutamate receptors (mGluRs), and depolarization, through VGCCs. We also find that the downstream protein kinases, PKA and PKC, have a role in potentiation in layer 2/3 pyramidal neurons of the neonatal visual cortex.

Covalent-Fragment Screening of Brd4 Identifies a Ligandable Site Orthogonal to the Acetyl-Lysine Binding Sites

2019 ◽  
Author(s):  
Michael Olp ◽  
Daniel Sprague ◽  
Stefan Kathman ◽  
Ziyang Xu ◽  
Alexandar Statsyuk ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Binding Site ◽  
Binding Sites ◽  
Computational Prediction ◽  
Chemical Probes ◽  
Computational Docking ◽  
Fragment Screening ◽  
Covalent Inhibitors ◽  
Bet Protein ◽  
Proof Of Principle

<p>Brd4, a member of the bromodomain and extraterminal domain (BET) family, has emerged as a promising epigenetic target in cancer and inflammatory disorders. All reported BET family ligands bind within the bromodomain acetyl-lysine binding sites and competitively inhibit BET protein interaction with acetylated chromatin. Alternative chemical probes that act orthogonally to the highly-conserved acetyl-lysine binding sites may exhibit selectivity within the BET family and avoid recently reported toxicity in clinical trials of BET bromodomain inhibitors. Here, we report the first identification of a ligandable site on a bromodomain outside the acetyl-lysine binding site. Inspired by our computational prediction of hotspots adjacent to non-homologous cysteine residues within the <i>C</i>-terminal Brd4 bromodomain (Brd4-BD2), we performed a mid-throughput mass spectrometry screen to identify cysteine-reactive fragments that covalently and selectively modify Brd4. Subsequent mass spectrometry, NMR and computational docking analyses of electrophilic fragment hits revealed a novel ligandable site near Cys356 that is unique to Brd4 among all human bromodomains. This site is orthogonal to the Brd4-BD2 acetyl-lysine binding site as Cys356 modification did not impact binding of the pan-BET bromodomain inhibitor JQ1 in fluorescence polarization assays. Finally, we tethered covalent fragments to JQ1 and performed NanoBRET assays to provide proof of principle that this orthogonal site can be covalently targeted in intact human cells. Overall, we demonstrate the potential of targeting sites orthogonal to bromodomain acetyl-lysine binding sites to develop bivalent and covalent inhibitors that displace Brd4 from chromatin.</p>

Effects of Multiple Binding Sites on Studies of Hydrogen Bonding between Nitroxide Radicals and Solvent Molecules

1993 ◽  
Vol 58 (1) ◽  
pp. 47-52 ◽  
Author(s):  
Imad Al-Bala'a ◽  
Richard D. Bates
Keyword(s):  
Hydrogen Bonding ◽  
Magnetic Resonance ◽  
Binding Site ◽  
Binding Sites ◽  
Hyperfine Coupling Constant ◽  
Hydrogen Donor ◽  
Complex Formation Constants ◽  
Multiple Binding Sites ◽  
Multiple Binding ◽  
Solvent Molecules

The role of more than one binding site on a nitroxide free radical in magnetic resonance determinations of the properties of the complex formed with a hydrogen donor is examined. The expression that relates observed hyperfine couplings in EPR spectra to complex formation constants and concentrations of each species in solution becomes much more complex when multiple binding sites are present, but reduces to a simpler form when binding at the two sites occurs independently and the binding at the non-nitroxide site does not produce significant differences in the hyperfine coupling constant in the complexed radical. Effects on studies of hydrogen bonding between multiple binding site nitroxides and hydrogen donor solvent molecules by other magnetic resonance methods are potentially more extreme.

Tuning of Electronic Properties in Conducting Polymers

2001 ◽  
Vol 66 (8) ◽  
pp. 1208-1218 ◽  
Author(s):  
Guofeng Li ◽  
Mira Josowicz ◽  
Jiří Janata
Keyword(s):  
Hydrogen Bonding ◽  
Binding Site ◽  
Binding Sites ◽  
Polymer Chains ◽  
Electronic Transitions ◽  
Weakly Bound ◽  
Ordered Structures ◽  
Doped Polymer ◽  
Positively Charged ◽  
Repeated Cycling

Structural and electronic transitions in poly(thiophenyleneiminophenylene), usually referred to as poly(phenylenesulfidephenyleneamine) (PPSA) upon electrochemical doping with LiClO4 have been investigated. The unusual electrochemical behavior of PPSA indicates that the dopant anions are bound in two energetically different sites. In the so-called "binding site", the ClO4- anion is Coulombically attracted to the positively charged S or N sites on one chain and simultaneously hydrogen-bonded with the N-H group on a neighboring polymer chain. This strong interaction causes a re-organization of the polymer chains, resulting in the formation of a networked structure linked together by these ClO4- Coulombic/hydrogen bonding "bridges". However, in the "non-binding site", the ClO4- anion is very weakly bound, involves only the electrostatic interaction and can be reversibly exchanged when the doped polymer is reduced. In the repeated cycling, the continuous and alternating influx and expulsion of ClO4- ions serves as a self-organizing process for such networked structures, giving rise to a diminishing number of available "non-binding" sites. The occurrence of these ordered structures has a major impact on the electrochemical activity and the morphology of the doped polymer. Also due to stabilization of the dopant ions, the doped polymer can be kept in a stable and desirable oxidation state, thus both work function and conductivity of the polymer can be electrochemically controlled.

scholarly journals Genes encoding components of the olfactory signal transduction cascade contain a DNA binding site that may direct neuronal expression.

1993 ◽  
Vol 13 (9) ◽  
pp. 5805-5813 ◽  
Author(s):  
M M Wang ◽  
R Y Tsai ◽  
K A Schrader ◽  
R R Reed
Keyword(s):  
Signal Transduction ◽  
Dna Binding ◽  
Binding Site ◽  
Binding Sites ◽  
Consensus Sequence ◽  
Initiation Site ◽  
Olfactory Neuron ◽  
Promoter Regions ◽  
Transcriptional Initiation ◽  
Genes Encoding

Genes which mediate odorant signal transduction are expressed at high levels in neurons of the olfactory epithelium. The molecular mechanism governing the restricted expression of these genes likely involves tissue-specific DNA binding proteins which coordinately activate transcription through sequence-specific interactions with olfactory promoter regions. We have identified binding sites for the olfactory neuron-specific transcription factor, Olf-1, in the sequences surrounding the transcriptional initiation site of five olfactory neuron-specific genes. The Olf-1 binding sites described define the consensus sequence YTCCCYRGGGAR. In addition, we have identified a second binding site, the U site, in the olfactory cyclic nucleotide gated channel and type III cyclase promoters, which binds factors present in all tissue examined. These experiments support a model in which expression of Olf-1 in the sensory neurons coordinately activates a set of olfactory neuron-specific genes. Furthermore, expression of a subset of these genes may be modulated by additional binding factors.

scholarly journals Study of Endogen Substrates, Drug Substrates and Inhibitors Binding Conformations on MRP4 and Its Variants by Molecular Docking and Molecular Dynamics

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 1051
Author(s):  
Edgardo Becerra ◽  
Giovanny Aguilera-Durán ◽  
Laura Berumen ◽  
Antonio Romo-Mancillas ◽  
Guadalupe García-Alcocer
Keyword(s):  
Molecular Dynamics ◽  
Molecular Docking ◽  
Binding Energy ◽  
Binding Site ◽  
Binding Sites ◽  
Adenosine Monophosphate ◽  
Competitive Inhibitor ◽  
Umbrella Sampling ◽  
Coarse Grained ◽  
Nucleotide Polymorphisms

Multidrug resistance protein-4 (MRP4) belongs to the ABC transporter superfamily and promotes the transport of xenobiotics including drugs. A non-synonymous single nucleotide polymorphisms (nsSNPs) in the ABCC4 gene can promote changes in the structure and function of MRP4. In this work, the interaction of certain endogen substrates, drug substrates, and inhibitors with wild type-MRP4 (WT-MRP4) and its variants G187W and Y556C were studied to determine differences in the intermolecular interactions and affinity related to SNPs using protein threading modeling, molecular docking, all-atom, coarse grained, and umbrella sampling molecular dynamics simulations (AA-MDS and CG-MDS, respectively). The results showed that the three MRP4 structures had significantly different conformations at given sites, leading to differences in the docking scores (DS) and binding sites of three different groups of molecules. Folic acid (FA) had the highest variation in DS on G187W concerning WT-MRP4. WT-MRP4, G187W, Y556C, and FA had different conformations through 25 ns AA-MD. Umbrella sampling simulations indicated that the Y556C-FA complex was the most stable one with or without ATP. In Y556C, the cyclic adenosine monophosphate (cAMP) and ceefourin-1 binding sites are located out of the entrance of the inner cavity, which suggests that both cAMP and ceefourin-1 may not be transported. The binding site for cAMP and ceefourin-1 is quite similar and the affinity (binding energy) of ceefourin-1 to WT-MRP4, G187W, and Y556C is greater than the affinity of cAMP, which may suggest that ceefourin-1 works as a competitive inhibitor. In conclusion, the nsSNPs G187W and Y556C lead to changes in protein conformation, which modifies the ligand binding site, DS, and binding energy.

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