scholarly journals Modulatory Actions of the Glycine Receptor β Subunit on the Positive Allosteric Modulation of Ethanol in α2 Containing Receptors

2021 ◽  
Vol 14 ◽  
Author(s):  
Braulio Muñoz ◽  
Trinidad Mariqueo ◽  
Pablo Murath ◽  
Christian Peters ◽  
Gonzalo E. Yevenes ◽  
...  
Keyword(s):  
Glycine Receptor ◽  
Basic Amino Acid ◽  
Brain Regions ◽  
Allosteric Modulation ◽  
Β Subunit ◽  
Ethanol Sensitivity ◽  
Intracellular Loop ◽  
Concentration Effects ◽  
Hek 293

Alpha1-containing glycine receptors (GlyRs) are major mediators of synaptic inhibition in the spinal cord and brain stem. Recent studies reported the presence of α2-containing GlyRs in other brain regions, such as nucleus accumbens and cerebral cortex. GlyR activation decreases neuronal excitability associated with sensorial information, motor control, and respiratory functions; all of which are significantly altered during ethanol intoxication. We evaluated the role of β GlyR subunits and of two basic amino acid residues, K389 and R390, located in the large intracellular loop (IL) of the α2 GlyR subunit, which are important for binding and functional modulation by Gβγ, the dimer of the trimeric G protein conformation, using HEK-293 transfected cells combined with patch clamp electrophysiology. We demonstrate a new modulatory role of the β subunit on ethanol sensitivity of α2 subunits. Specifically, we found a differential allosteric modulation in homomeric α2 GlyRs compared with the α2β heteromeric conformation. Indeed, while α2 was insensitive, α2β GlyRs were substantially potentiated by ethanol, GTP-γ-S, propofol, Zn2+ and trichloroethanol. Furthermore, a Gβγ scavenger (ct-GRK2) selectively attenuated the effects of ethanol on recombinant α2β GlyRs. Mutations in an α2 GlyR co-expressed with the β subunit (α2AAβ) specifically blocked ethanol sensitivity, but not propofol potentiation. These results show a selective mechanism for low ethanol concentration effects on homomeric and heteromeric conformations of α2 GlyRs and provide a new mechanism for ethanol pharmacology, which is relevant to upper brain regions where α2 GlyRs are abundantly expressed.

scholarly journals Glycine receptors in GtoPdb v.2021.3

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Joseph. W. Lynch ◽  
Lucia G. Sivilotti ◽  
Trevor G. Smart
Keyword(s):  
Single Channel ◽  
Glycine Receptor ◽  
Chloride Concentration ◽  
Molecular Structures ◽  
Β Subunit ◽  
Glycine Receptors ◽  
Intracellular Loop ◽  
Mrna Editing ◽  
Α Subunit ◽  
Loop Region

The inhibitory glycine receptor (nomenclature as agreed by the NC-IUPHAR Subcommittee on Glycine Receptors) is a member of the Cys-loop superfamily of transmitter-gated ion channels that includes the zinc activated channels, GABAA, nicotinic acetylcholine and 5-HT3 receptors and Zn2+- activated channels. The receptor is expressed either as a homo-pentamer of α subunits, or a complex now thought to harbour 2α and 3β subunits [33, 7], that contain an intrinsic anion channel. Four differentially expressed isoforms of the α-subunit (α1-α4) and one variant of the β-subunit (β1, GLRB, P48167) have been identified by genomic and cDNA cloning. Further diversity originates from alternative splicing of the primary gene transcripts for α1 (α1INS and α1del), α2 (α2A and α2B), α3 (α3S and α3L) and β (βΔ7) subunits and by mRNA editing of the α2 and α3 subunit [83, 93, 21]. Both α2 splicing and α3 mRNA editing can produce subunits (i.e., α2B and α3P185L) with enhanced agonist sensitivity. Predominantly, the adult form of the receptor contains α1 (or α3) and β subunits whereas the immature form is mostly composed of only α2 subunits. The &a;pha;4 subunit is a pseudogene in humans. High resolution molecular structures are available for the α1 and α3 homomeric receptors [50, 20]. As in other Cys-loop receptors, the orthosteric binding site for agonists and the competitive antagonist strychnine is formed at the interfaces between the subunits’ extracellular domains. Inclusion of the β-subunit in the pentameric glycine receptor contributes to agonist binding, reduces single channel conductance and alters pharmacology. The β-subunit also anchors the receptor, via an amphipathic sequence within the large intracellular loop region, to gephyrin. This a cytoskeletal attachment protein that binds to a number of subsynaptic proteins involved in cytoskeletal structure and thus clusters and anchors hetero-oligomeric receptors to the synapse [56, 54, 88]. G protein βγ subunits enhance the open state probability of native and recombinant glycine receptors by association with domains within the large intracellular loop [124, 123]. Intracellular chloride concentration modulates the kinetics of native and recombinant glycine receptors [96]. Intracellular Ca2+ appears to increase native and recombinant glycine receptor affinity, prolonging channel open events, by a mechanism that does not involve phosphorylation [27]. Extracellular Zn2+ potentiates GlyR function at nanomolar concentrations [86]. and causes inhibition at higher micromolar concentrations (17).

scholarly journals Glycine receptors (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database

2019 ◽  
Vol 2019 (4) ◽  
Author(s):  
Joseph. W. Lynch ◽  
Lucia G. Sivilotti ◽  
Trevor G. Smart
Keyword(s):  
Single Channel ◽  
Glycine Receptor ◽  
Chloride Concentration ◽  
Anion Channel ◽  
Β Subunit ◽  
Glycine Receptors ◽  
Intracellular Loop ◽  
Mrna Editing ◽  
Α Subunit ◽  
Loop Region

The inhibitory glycine receptor (nomenclature as agreed by the NC-IUPHAR Subcommittee on Glycine Receptors) is a member of the Cys-loop superfamily of transmitter-gated ion channels that includes the zinc activated channels, GABAA, nicotinic acetylcholine and 5-HT3 receptors [63]. The receptor is expressed either as a homo-pentamer of α subunits, or a complex now thought to harbour 2α and 3β subunits [30, 7], that contain an intrinsic anion channel. Four differentially expressed isoforms of the α-subunit (α1-α4) and one variant of the β-subunit (β1, GLRB, P48167) have been identified by genomic and cDNA cloning. Further diversity originates from alternative splicing of the primary gene transcripts for α1 (α1INS and α1del), α2 (α2A and α2B), α3 (α3S and α3L) and β (βΔ7) subunits and by mRNA editing of the α2 and α3 subunit [80, 91, 18]. Both α2 splicing and α3 mRNA editing can produce subunits (i.e., α2B and α3P185L) with enhanced agonist sensitivity. Predominantly, the mature form of the receptor contains α1 (or α3) and β subunits while the immature form is mostly composed of only α2 subunits. RNA transcripts encoding the α4-subunit have not been detected in adult humans. The N-terminal domain of the α-subunit contains both the agonist and strychnine binding sites that consist of several discontinuous regions of amino acids. Inclusion of the β-subunit in the pentameric glycine receptor contributes to agonist binding, reduces single channel conductance and alters pharmacology. The β-subunit also anchors the receptor, via an amphipathic sequence within the large intracellular loop region, to gephyrin. The latter is a cytoskeletal attachment protein that binds to a number of subsynaptic proteins involved in cytoskeletal structure and thus clusters and anchors hetero-oligomeric receptors to the synapse [86, 51, 53]. G-protein βγ subunits enhance the open state probability of native and recombinant glycine receptors by association with domains within the large intracellular loop [122, 121]. Intracellular chloride concentration modulates the kinetics of native and recombinant glycine receptors [94]. Intracellular Ca2+ appears to increase native and recombinant glycine receptor affinity, prolonging channel open events, by a mechanism that does not involve phosphorylation [24].

scholarly journals Glycine receptors (version 2020.4) in the IUPHAR/BPS Guide to Pharmacology Database

2020 ◽  
Vol 2020 (4) ◽  
Author(s):  
Joseph. W. Lynch ◽  
Lucia G. Sivilotti ◽  
Trevor G. Smart
Keyword(s):  
Single Channel ◽  
Glycine Receptor ◽  
Chloride Concentration ◽  
Molecular Structures ◽  
Β Subunit ◽  
Glycine Receptors ◽  
Intracellular Loop ◽  
Mrna Editing ◽  
Α Subunit ◽  
Loop Region

The inhibitory glycine receptor (nomenclature as agreed by the NC-IUPHAR Subcommittee on Glycine Receptors) is a member of the Cys-loop superfamily of transmitter-gated ion channels that includes the zinc activated channels, GABAA, nicotinic acetylcholine and 5-HT3 receptors and Zn2+- activated channels. The receptor is expressed either as a homo-pentamer of α subunits, or a complex now thought to harbour 2α and 3β subunits [32, 7], that contain an intrinsic anion channel. Four differentially expressed isoforms of the α-subunit (α1-α4) and one variant of the β-subunit (β1, GLRB, P48167) have been identified by genomic and cDNA cloning. Further diversity originates from alternative splicing of the primary gene transcripts for α1 (α1INS and α1del), α2 (α2A and α2B), α3 (α3S and α3L) and β (βΔ7) subunits and by mRNA editing of the α2 and α3 subunit [82, 92, 20]. Both α2 splicing and α3 mRNA editing can produce subunits (i.e., α2B and α3P185L) with enhanced agonist sensitivity. Predominantly, the adult form of the receptor contains α1 (or α3) and β subunits whereas the immature form is mostly composed of only α2 subunits. The &a;pha;4 subunit is a pseudogene in humans. High resolution molecular structures are available for the α1 and α3 homomeric receptors [49, 19]. As in other Cys-loop receptors, the orthosteric binding site for agonists and the competitive antagonist strychnine is formed at the interfaces between the subunits’ extracellular domains. Inclusion of the β-subunit in the pentameric glycine receptor contributes to agonist binding, reduces single channel conductance and alters pharmacology. The β-subunit also anchors the receptor, via an amphipathic sequence within the large intracellular loop region, to gephyrin. This a cytoskeletal attachment protein that binds to a number of subsynaptic proteins involved in cytoskeletal structure and thus clusters and anchors hetero-oligomeric receptors to the synapse [55, 53, 87]. G protein βγ subunits enhance the open state probability of native and recombinant glycine receptors by association with domains within the large intracellular loop [123, 122]. Intracellular chloride concentration modulates the kinetics of native and recombinant glycine receptors [95]. Intracellular Ca2+ appears to increase native and recombinant glycine receptor affinity, prolonging channel open events, by a mechanism that does not involve phosphorylation [26]. Extracellular Zn2+ potentiates GlyR function at nanomolar concentrations [85]. and causes inhibition at higher micromolar concentrations (17).

Role of CXCR3 carboxyl terminus and third intracellular loop in receptor-mediated migration, adhesion and internalization in response to CXCL11

Blood ◽  
2006 ◽  
Vol 107 (10) ◽  
pp. 3821-3831 ◽  
Author(s):  
Michal Dagan-Berger ◽  
Rotem Feniger-Barish ◽  
Shani Avniel ◽  
Hanna Wald ◽  
Eithan Galun ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Actin Polymerization ◽  
Inflammatory Responses ◽  
Carboxyl Terminus ◽  
Intracellular Loop ◽  
T Helper 1 ◽  
Hek 293 ◽  
The Third ◽  
Third Intracellular Loop

The chemokine receptor CXCR3 is predominantly expressed on activated T and natural killer (NK) cells. CXCR3 and its ligands, CXCL11, CXCL10, and CXCL9, play a major role in T-helper 1 (Th1)–dependent inflammatory responses. CXCL11 is the most dominant physiological inducer of adhesion, migration, and internalization of CXCR3. To study the role of CXCR3 carboxyl-terminus and the third intracellular (3i) loop in chemokine-mediated migration, adhesion, and CXCR3 internalization, we generated CXCR3 receptors mutated in their distal (Ser-Thr domain) or proximal (trileucine domain) membrane carboxyl terminus, and/or the third intracellular loop. We found that migration of CXCR3-expressing HEK 293 cells toward CXCL11 was pertussis toxin–dependent and required the membrane proximal carboxyl terminus of CXCR3. Internalization induced by CXCL11 and protein kinase C (PKC) activation was also regulated by the membrane proximal carboxyl terminus; however, only CXCL11-induced internalization required the LLL motif of this region. Internalization and Ca2+ flux induced by CXCL11 were independent of the 3i loop S245, whereas migration at high CXCL11 concentrations, integrin-dependent adhesion, and actin polymerization were S245 dependent. Our findings indicate that CXCL11-dependent CXCR3 internalization and cell migration are regulated by the CXCR3 membrane proximal carboxyl terminus, whereas adhesion is regulated by the 3i loop S245. Thus, distinct conformational changes induced by a given CXCR3 ligand trigger different downstream effectors of adhesion, motility, and CXCR3 desensitization.

scholarly journals Species-Specific Regulation of TRPM2 by PI(4,5)P2 via the Membrane Interfacial Cavity

2021 ◽  
Vol 22 (9) ◽  
pp. 4637
Author(s):  
Daniel Barth ◽  
Andreas Lückhoff ◽  
Frank J. P. Kühn
Keyword(s):  
Amino Acid Residues ◽  
Hek 293 ◽  
Complete Inactivation ◽  
293 Cells ◽  
Activation Mechanisms ◽  
Specific Regulation ◽  
Species Specific ◽  
Inside Out ◽  
Positively Charged

The human apoptosis channel TRPM2 is stimulated by intracellular ADR-ribose and calcium. Recent studies show pronounced species-specific activation mechanisms. Our aim was to analyse the functional effect of phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2), commonly referred to as PIP2, on different TRPM2 orthologues. Moreover, we wished to identify the interaction site between TRPM2 and PIP2. We demonstrate a crucial role of PIP2, in the activation of TRPM2 orthologues of man, zebrafish, and sea anemone. Utilizing inside-out patch clamp recordings of HEK-293 cells transfected with TRPM2, differential effects of PIP2 that were dependent on the species variant became apparent. While depletion of PIP2 via polylysine uniformly caused complete inactivation of TRPM2, restoration of channel activity by artificial PIP2 differed widely. Human TRPM2 was the least sensitive species variant, making it the most susceptible one for regulation by changes in intramembranous PIP2 content. Furthermore, mutations of highly conserved positively charged amino acid residues in the membrane interfacial cavity reduced the PIP2 sensitivity in all three TRPM2 orthologues to varying degrees. We conclude that the membrane interfacial cavity acts as a uniform PIP2 binding site of TRPM2, facilitating channel activation in the presence of ADPR and Ca2+ in a species-specific manner.

scholarly journals The G Protein-Coupled Glutamate Receptors as Novel Molecular Targets in Schizophrenia Treatment—A Narrative Review

2021 ◽  
Vol 10 (7) ◽  
pp. 1475
Author(s):  
Waldemar Kryszkowski ◽  
Tomasz Boczek
Keyword(s):  
Glutamate Receptors ◽  
Metabotropic Glutamate Receptors ◽  
Glutamate Release ◽  
Molecular Targets ◽  
Brain Regions ◽  
Psychotic Symptoms ◽  
Unknown Etiology ◽  
Metabotropic Glutamate ◽  
G Protein Coupled

Schizophrenia is a severe neuropsychiatric disease with an unknown etiology. The research into the neurobiology of this disease led to several models aimed at explaining the link between perturbations in brain function and the manifestation of psychotic symptoms. The glutamatergic hypothesis postulates that disrupted glutamate neurotransmission may mediate cognitive and psychosocial impairments by affecting the connections between the cortex and the thalamus. In this regard, the greatest attention has been given to ionotropic NMDA receptor hypofunction. However, converging data indicates metabotropic glutamate receptors as crucial for cognitive and psychomotor function. The distribution of these receptors in the brain regions related to schizophrenia and their regulatory role in glutamate release make them promising molecular targets for novel antipsychotics. This article reviews the progress in the research on the role of metabotropic glutamate receptors in schizophrenia etiopathology.

scholarly journals The Protective Role of Brain CYP2J in Parkinson’s Disease Models

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Yueran Li ◽  
Jinhua Wu ◽  
Xuming Yu ◽  
Shufang Na ◽  
Ke Li ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Brain Regions ◽  
Protective Role ◽  
Neural Cells ◽  
Endogenous Substrates ◽  
6 Hydroxydopamine ◽  
Myd88 Signaling ◽  
Lps Treatment

CYP2J proteins are present in the neural cells of human and rodent brain regions. The aim of this study was to investigate the role of brain CYP2J in Parkinson’s disease. Rats received right unilateral injection with lipopolysaccharide (LPS) or 6-hydroxydopamine (6-OHDA) in the substantia nigra following transfection with or without the CYP2J3 expression vector. Compared with LPS-treated rats, CYP2J3 transfection significantly decreased apomorphine-induced rotation by 57.3% at day 12 and 47.0% at day 21 after LPS treatment; moreover, CYP2J3 transfection attenuated the accumulation of α-synuclein. Compared with the 6-OHDA group, the number of rotations by rats transfected with CYP2J3 decreased by 59.6% at day 12 and 43.5% at day 21 after 6-OHDA treatment. The loss of dopaminergic neurons and the inhibition of the antioxidative system induced by LPS or 6-OHDA were attenuated following CYP2J3 transfection. The TLR4-MyD88 signaling pathway was involved in the downregulation of brain CYP2J induced by LPS, and CYP2J transfection upregulated the expression of Nrf2 via the inhibition of miR-340 in U251 cells. The data suggest that increased levels of CYP2J in the brain can delay the pathological progression of PD initiated by inflammation or neurotoxins. The alteration of the metabolism of the endogenous substrates (e.g., AA) could affect the risk of neurodegenerative disease.

Halothane Inhibition of Recombinant Cardiac L-type Ca2+ Channels Expressed in HEK-293 Cells

2005 ◽  
Vol 103 (6) ◽  
pp. 1156-1166 ◽  
Author(s):  
Kevin J. Gingrich ◽  
Son Tran ◽  
Igor M. Nikonorov ◽  
Thomas J. Blanck
Keyword(s):  
Charge Transfer ◽  
Calcium Channels ◽  
Dependent Manner ◽  
Current Time ◽  
Hek 293 ◽  
Hek 293 Cells ◽  
293 Cells ◽  
Dependent Inactivation ◽  
Voltage Dependent

Background Volatile anesthetics depress cardiac contractility, which involves inhibition of cardiac L-type calcium channels. To explore the role of voltage-dependent inactivation, the authors analyzed halothane effects on recombinant cardiac L-type calcium channels (alpha1Cbeta2a and alpha1Cbeta2aalpha2/delta1), which differ by the alpha2/delta1 subunit and consequently voltage-dependent inactivation. Methods HEK-293 cells were transiently cotransfected with complementary DNAs encoding alpha1C tagged with green fluorescent protein and beta2a, with and without alpha2/delta1. Halothane effects on macroscopic barium currents were recorded using patch clamp methodology from cells expressing alpha1Cbeta2a and alpha1Cbeta2aalpha2/delta1 as identified by fluorescence microscopy. Results Halothane inhibited peak current (I(peak)) and enhanced apparent inactivation (reported by end pulse current amplitude of 300-ms depolarizations [I300]) in a concentration-dependent manner in both channel types. alpha2/delta1 coexpression shifted relations leftward as reported by the 50% inhibitory concentration of I(peak) and I300/I(peak)for alpha1Cbeta2a (1.8 and 14.5 mm, respectively) and alpha1Cbeta2aalpha2/delta1 (0.74 and 1.36 mm, respectively). Halothane reduced transmembrane charge transfer primarily through I(peak) depression and not by enhancement of macroscopic inactivation for both channels. Conclusions The results indicate that phenotypic features arising from alpha2/delta1 coexpression play a key role in halothane inhibition of cardiac L-type calcium channels. These features included marked effects on I(peak) inhibition, which is the principal determinant of charge transfer reductions. I(peak) depression arises primarily from transitions to nonactivatable states at resting membrane potentials. The findings point to the importance of halothane interactions with states present at resting membrane potential and discount the role of inactivation apparent in current time courses in determining transmembrane charge transfer.

Electroencephalographic Recordings of Focal Seizures in Patients Affected by Periventricular Nodular Heterotopia: Role of the Heterotopic Nodules in the Genesis of Epileptic Discharges

2004 ◽  
Vol 19 (3) ◽  
pp. 369-377
Author(s):  
Giorgio Battaglia ◽  
Silvana Franceschetti ◽  
Luisa Chiapparini ◽  
Elena Freri ◽  
Stefania Bassanini ◽  
...  
Keyword(s):  
Brain Regions ◽  
Periventricular Nodular Heterotopia ◽  
Focal Seizures ◽  
Ictal Eeg ◽  
Epileptic Discharges ◽  
Nodular Heterotopia ◽  
Eeg Recordings ◽  
Drug Resistant Epilepsy ◽  
Video Eeg

Patients affected by periventricular nodular heterotopia are frequently characterized by focal drug-resistant epilepsy. To investigate the role of periventricular nodules in the genesis of seizures, we analyzed the electroencephalographic (EEG) features of focal seizures recorded by means of video-EEG in 10 patients affected by different types of periventricular nodular heterotopia and followed for prolonged periods of time at the epilepsy center of our institute. The ictal EEG recordings with surface electrodes revealed common features in all patients: all seizures originated from the brain regions where the periventricular nodular heterotopia were located; EEG patterns recorded on the leads exploring the periventricular nodular heterotopia were very similar both at the onset and immediately after the seizure's end in all patients. Our data suggest that seizures are generated by abnormal anatomic circuitries, including the heterotopic nodules and adjacent cortical areas. The major role of heterotopic neurons in the genesis and propagation of epileptic discharges must be taken into account when planning surgery for epilepsy in patients with periventricular nodular heterotopia. ( J Child Neurol 2005;20:369—377).

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