1
|
Boccaccio A, Finol-Urdaneta RK. Redox Bridling of GIRK Channel Activity. FUNCTION 2023; 4:zqad027. [PMID: 37342411 PMCID: PMC10278978 DOI: 10.1093/function/zqad027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2023] [Revised: 05/30/2023] [Accepted: 05/31/2023] [Indexed: 06/22/2023] Open
Affiliation(s)
- Anna Boccaccio
- Institute of Biophysics, National Research Council, Via De Marini 6, 16149 Genoa, Italy
| | | |
Collapse
|
2
|
Lee SJ, Maeda S, Gao J, Nichols CG. Oxidation Driven Reversal of PIP 2-dependent Gating in GIRK2 Channels. FUNCTION 2023; 4:zqad016. [PMID: 37168492 PMCID: PMC10165546 DOI: 10.1093/function/zqad016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Revised: 03/24/2023] [Accepted: 04/03/2023] [Indexed: 05/13/2023] Open
Abstract
Physiological activity of G protein gated inward rectifier K+ (GIRK, Kir3) channel, dynamically regulated by three key ligands, phosphoinositol-4,5-bisphosphate (PIP2), Gβγ, and Na+, underlies cellular electrical response to multiple hormones and neurotransmitters in myocytes and neurons. In a reducing environment, matching that inside cells, purified GIRK2 (Kir3.2) channels demonstrate low basal activity, and expected sensitivity to the above ligands. However, under oxidizing conditions, anomalous behavior emerges, including rapid loss of PIP2 and Na+-dependent activation and a high basal activity in the absence of any agonists, that is now paradoxically inhibited by PIP2. Mutagenesis identifies two cysteine residues (C65 and C190) as being responsible for the loss of PIP2 and Na+-dependent activity and the elevated basal activity, respectively. The results explain anomalous findings from earlier studies and illustrate the potential pathophysiologic consequences of oxidation on GIRK channel function, as well as providing insight to reversed ligand-dependence of Kir and KirBac channels.
Collapse
Affiliation(s)
- Sun-Joo Lee
- Department of Cell Biology and Physiology and the Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Shoji Maeda
- Department of Pharmacology, Medical School, University of Michigan, Ann Arbor, Michigan, USA
| | - Jian Gao
- Department of Cell Biology and Physiology and the Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Colin G Nichols
- Department of Cell Biology and Physiology and the Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri, USA
| |
Collapse
|
3
|
Encephalopathy-causing mutations in Gβ 1 ( GNB1) alter regulation of neuronal GIRK channels. iScience 2021; 24:103018. [PMID: 34522861 PMCID: PMC8426278 DOI: 10.1016/j.isci.2021.103018] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 08/04/2021] [Accepted: 08/18/2021] [Indexed: 11/24/2022] Open
Abstract
Mutations in the GNB1 gene, encoding the Gβ1 subunit of heterotrimeric G proteins, cause GNB1 Encephalopathy. Patients experience seizures, pointing to abnormal activity of ion channels or neurotransmitter receptors. We studied three Gβ1 mutations (K78R, I80N and I80T) using computational and functional approaches. In heterologous expression models, these mutations did not alter the coupling between G protein-coupled receptors to Gi/o, or the Gβγ regulation of the neuronal voltage-gated Ca2+ channel CaV2.2. However, the mutations profoundly affected the Gβγ regulation of the G protein-gated inwardly rectifying potassium channels (GIRK, or Kir3). Changes were observed in Gβ1 protein expression levels, Gβγ binding to cytosolic segments of GIRK subunits, and in Gβγ function, and included gain-of-function for K78R or loss-of-function for I80T/N, which were GIRK subunit-specific. Our findings offer new insights into subunit-dependent gating of GIRKs by Gβγ, and indicate diverse etiology of GNB1 Encephalopathy cases, bearing a potential for personalized treatment. GIRK channels are key players affected by GNB1 mutations under study (K78R and I80N/T) Effects of mutations (LoF or GoF) are channel subunit composition-specific The findings help to understand the GNB1 encephalopathy and to devise treatments The results yield new insights into mechanisms of Gβγ regulation of GIRKs
Collapse
|
4
|
Bizzarri B, Botta L, Aversa D, Mercuri NB, Poli G, Barbieri A, Berretta N, Saladino R. L-DOPA-quinone Mediated Recovery from GIRK Channel Firing Inhibition in Dopaminergic Neurons. ACS Med Chem Lett 2019; 10:431-436. [PMID: 30996775 PMCID: PMC6466524 DOI: 10.1021/acsmedchemlett.8b00477] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Accepted: 01/09/2019] [Indexed: 01/07/2023] Open
Abstract
The oxidative degeneration of dopamine-releasing (DAergic) neurons in the substantia nigra pars compacta (SNc) has attracted much interest in preclinical research, due to its involvement in Parkinson's disease manifestations. Evidence exists on the participation of quinone derivatives in mitochondrial dysfunction, alpha synuclein protein aggregation, and protein degradation. With the aim to investigate the role of L-DOPA-quinone in DAergic neuron functions, we synthesized L-DOPA-quinone by use of 2-iodoxybenzoic acid and measured its activity in recovery from dopamine-mediated firing inhibition of SNc neurons. Noteworthy, L-DOPA-quinone counteracts firing inhibition in SNc DAergic neurons caused by GIRK opening. A possible mechanism to explain the effect of L-DOPA-quinone on GIRK channel has been proposed by computational models. Overall, the study showed the possibility that L-DOPA-quinone stabilizes GIRK in a preopen conformation through formation of a covalent adduct with cysteine-65 on the GIRK2 subunit of the protein.
Collapse
Affiliation(s)
- Bruno
M. Bizzarri
- Dipartimento
di Scienze Ecologiche e Biologiche, Università
della Tuscia, Via S. C. De Lellis 44, 01100 Viterbo, Italy
| | - Lorenzo Botta
- Dipartimento
di Scienze Ecologiche e Biologiche, Università
della Tuscia, Via S. C. De Lellis 44, 01100 Viterbo, Italy
| | - Daniela Aversa
- IRCCS
Fondazione Santa Lucia, Via Ardeatina, 306/354, 00142 Rome, Italy
| | - Nicola B. Mercuri
- IRCCS
Fondazione Santa Lucia, Via Ardeatina, 306/354, 00142 Rome, Italy
- Dipartimento
di Medicina dei Sistemi, Università
di Roma Tor Vergata, Via Montpellier, 1, 00133 Rome, Italy
| | - Giulio Poli
- Dipartimento
di Biotecnologie, Chimica e Farmacia, Università
degli studi di Siena, Via A. Moro 2, 53100 Siena, Italy
| | - Alessandro Barbieri
- Dipartimento
di Biotecnologie, Chimica e Farmacia, Università
degli studi di Siena, Via A. Moro 2, 53100 Siena, Italy
| | - Nicola Berretta
- IRCCS
Fondazione Santa Lucia, Via Ardeatina, 306/354, 00142 Rome, Italy
| | - Raffaele Saladino
- Dipartimento
di Scienze Ecologiche e Biologiche, Università
della Tuscia, Via S. C. De Lellis 44, 01100 Viterbo, Italy
| |
Collapse
|
5
|
Lacin E, Aryal P, Glaaser IW, Bodhinathan K, Tsai E, Marsh N, Tucker SJ, Sansom MSP, Slesinger PA. Dynamic role of the tether helix in PIP 2-dependent gating of a G protein-gated potassium channel. J Gen Physiol 2017; 149:799-811. [PMID: 28720589 PMCID: PMC5560777 DOI: 10.1085/jgp.201711801] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Revised: 06/06/2017] [Accepted: 06/21/2017] [Indexed: 01/21/2023] Open
Abstract
G protein–gated inwardly rectifying potassium (GIRK) channels are activated by the phospholipid phosphatidylinositol 4,5 bisphosphate (PIP2). Using functional and computational experiments, Lacin et al. reveal that PIP2 interacts with the tether helix of the neuronal GIRK channel in a dynamic way. G protein–gated inwardly rectifying potassium (GIRK) channels control neuronal excitability in the brain and are implicated in several different neurological diseases. The anionic phospholipid phosphatidylinositol 4,5 bisphosphate (PIP2) is an essential cofactor for GIRK channel gating, but the precise mechanism by which PIP2 opens GIRK channels remains poorly understood. Previous structural studies have revealed several highly conserved, positively charged residues in the “tether helix” (C-linker) that interact with the negatively charged PIP2. However, these crystal structures of neuronal GIRK channels in complex with PIP2 provide only snapshots of PIP2’s interaction with the channel and thus lack details about the gating transitions triggered by PIP2 binding. Here, our functional studies reveal that one of these conserved basic residues in GIRK2, Lys200 (6′K), supports a complex and dynamic interaction with PIP2. When Lys200 is mutated to an uncharged amino acid, it activates the channel by enhancing the interaction with PIP2. Atomistic molecular dynamic simulations of neuronal GIRK2 with the same 6′ substitution reveal an open GIRK2 channel with PIP2 molecules adopting novel positions. This dynamic interaction with PIP2 may explain the intrinsic low open probability of GIRK channels and the mechanism underlying activation by G protein Gβγ subunits and ethanol.
Collapse
Affiliation(s)
- Emre Lacin
- Fishberg Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Prafulla Aryal
- Department of Biochemistry, University of Oxford, Oxford, England, UK.,OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford, England, UK
| | - Ian W Glaaser
- Fishberg Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY
| | | | - Eric Tsai
- Fishberg Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Nidaa Marsh
- Fishberg Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Stephen J Tucker
- OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford, England, UK.,Department of Physics, University of Oxford, Oxford, England, UK
| | - Mark S P Sansom
- Department of Biochemistry, University of Oxford, Oxford, England, UK.,OXION Initiative in Ion Channels and Disease, University of Oxford, Oxford, England, UK
| | - Paul A Slesinger
- Fishberg Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY .,Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| |
Collapse
|
6
|
Dual activation of neuronal G protein-gated inwardly rectifying potassium (GIRK) channels by cholesterol and alcohol. Sci Rep 2017; 7:4592. [PMID: 28676630 PMCID: PMC5496853 DOI: 10.1038/s41598-017-04681-x] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Accepted: 05/18/2017] [Indexed: 12/20/2022] Open
Abstract
Activation of G protein-gated inwardly rectifying potassium (GIRK) channels leads to a hyperpolarization of the neuron’s membrane potential, providing an important component of inhibition in the brain. In addition to the canonical G protein-activation pathway, GIRK channels are activated by small molecules but less is known about the underlying gating mechanisms. One drawback to previous studies has been the inability to control intrinsic and extrinsic factors. Here we used a reconstitution strategy with highly purified mammalian GIRK2 channels incorporated into liposomes and demonstrate that cholesterol or intoxicating concentrations of ethanol, i.e., >20 mM, each activate GIRK2 channels directly, in the absence of G proteins. Notably, both activators require the membrane phospholipid PIP2 but appear to interact independently with different regions of the channel. Elucidating the mechanisms underlying G protein-independent pathways of activating GIRK channels provides a unique strategy for developing new types of neuronal excitability modulators.
Collapse
|
7
|
Inanobe A, Nakagawa A, Kurachi Y. Interactions of cations with the cytoplasmic pores of inward rectifier K(+) channels in the closed state. J Biol Chem 2011; 286:41801-41811. [PMID: 21982822 PMCID: PMC3308888 DOI: 10.1074/jbc.m111.278531] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Revised: 10/06/2011] [Indexed: 12/25/2022] Open
Abstract
Ion channels gate at membrane-embedded domains by changing their conformation along the ion conduction pathway. Inward rectifier K(+) (Kir) channels possess a unique extramembrane cytoplasmic domain that extends this pathway. However, the relevance and contribution of this domain to ion permeation remain unclear. By qualitative x-ray crystallographic analysis, we found that the pore in the cytoplasmic domain of Kir3.2 binds cations in a valency-dependent manner and does not allow the displacement of Mg(2+) by monovalent cations or spermine. Electrophysiological analyses revealed that the cytoplasmic pore of Kir3.2 selectively binds positively charged molecules and has a higher affinity for Mg(2+) when it has a low probability of being open. The selective blocking of chemical modification of the side chain of pore-facing residues by Mg(2+) indicates that the mode of binding of Mg(2+) is likely to be similar to that observed in the crystal structure. These results indicate that the Kir3.2 crystal structure has a closed conformation with a negative electrostatic field potential at the cytoplasmic pore, the potential of which may be controlled by conformational changes in the cytoplasmic domain to regulate ion diffusion along the pore.
Collapse
Affiliation(s)
- Atsushi Inanobe
- Department of Pharmacology, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan; Center for Advanced Medical Engineering and Informatics, Osaka University, Osaka 565-0871, Japan.
| | - Atsushi Nakagawa
- Laboratory of Supramolecular Crystallography, Institute for Protein Research, Osaka University, Osaka 565-0871, Japan
| | - Yoshihisa Kurachi
- Department of Pharmacology, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan; Center for Advanced Medical Engineering and Informatics, Osaka University, Osaka 565-0871, Japan.
| |
Collapse
|
8
|
Inanobe A, Matsuura T, Nakagawa A, Kurachi Y. Inverse agonist-like action of cadmium on G-protein-gated inward-rectifier K+ channels. Biochem Biophys Res Commun 2011; 407:366-71. [DOI: 10.1016/j.bbrc.2011.03.025] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2011] [Accepted: 03/03/2011] [Indexed: 11/28/2022]
|
9
|
Bendahhou S, Fournier E, Gallet S, Ménard D, Larroque MM, Barhanin J. Corticosteroid-exacerbated symptoms in an Andersen's syndrome kindred. Hum Mol Genet 2007; 16:900-6. [PMID: 17324964 DOI: 10.1093/hmg/ddm034] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Periodic paralysis, cardiac arrhythmia and bone features are the hallmark of Andersen's syndrome (AS), a rare disorder caused by mutations in the KCNJ2 gene that encodes for the inward rectifier K(+)-channel Kir2.1. Rest following strenuous physical activity, carbohydrate ingestion, emotional stress and exposure to cold are the precipitating triggers. Most of the mutations act in a dominant-negative fashion, either through a trafficking dysfunction or through Kir2.1-phosphatidyl inositol bisphosphate binding defect. We have identified two families that were diagnosed with periodic paralysis and cardiac abnormalities, but only discrete development features. The proband in one of the two families reported having his symptoms occurring twice within the day following corticosteroids ingestion, and alleviated after stopping the corticosteroid treatment. Electromyographic evaluations pointed out to a typical hypokalemic periodic paralysis pattern. Molecular screening of the KCNJ2 gene identified two mutations leading to C54F and T305P substitutions in the Kir2.1 protein. Functional expression in mammalian cells revealed a loss-of-function of the mutated channels and a dominant-negative effect when both mutants and wild-type channels are present in the same cell. However, channel trafficking and assembly are not affected. Substitutions at these residues may interfere with phosphatidyl inositol bisphosphate binding to Kir2.1 channels. Sensitivity of our patients to multiple corticosteroid administrations shows that care must be taken in the use of such treatments in AS patients. Taken together, our data suggest the inclusion of the KCNJ2 gene in the molecular screening of patients with periodic paralysis, even when the classical AS dysmorphic features are not present.
Collapse
Affiliation(s)
- Saïd Bendahhou
- Institut de Pharmacologie Moléculaire et Cellulaire, UMR 6097 CNRS, Université de Nice Sophia Antipolis, France.
| | | | | | | | | | | |
Collapse
|
10
|
Xia M, Jin Q, Bendahhou S, He Y, Larroque MM, Chen Y, Zhou Q, Yang Y, Liu Y, Liu B, Zhu Q, Zhou Y, Lin J, Liang B, Li L, Dong X, Pan Z, Wang R, Wan H, Qiu W, Xu W, Eurlings P, Barhanin J, Chen Y. A Kir2.1 gain-of-function mutation underlies familial atrial fibrillation. Biochem Biophys Res Commun 2005; 332:1012-9. [PMID: 15922306 DOI: 10.1016/j.bbrc.2005.05.054] [Citation(s) in RCA: 264] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2005] [Accepted: 05/10/2005] [Indexed: 12/20/2022]
Abstract
The inward rectifier K(+) channel Kir2.1 mediates the potassium I(K1) current in the heart. It is encoded by KCNJ2 gene that has been linked to Andersen's syndrome. Recently, strong evidences showed that Kir2.1 channels were associated with mouse atrial fibrillation (AF), therefore we hypothesized that KCNJ2 was associated with familial AF. Thirty Chinese AF kindreds were evaluated for mutations in KCNJ2 gene. A valine-to-isoleucine mutation at position 93 (V93I) of Kir2.1 was found in all affected members in one kindred. This valine and its flanking sequence is highly conserved in Kir2.1 proteins among different species. Functional analysis of the V93I mutant demonstrated a gain-of-function consequence on the Kir2.1 current. This effect is opposed to the loss-of-function effect of previously reported mutations in Andersen's syndrome. Kir2.1 V93I mutation may play a role in initiating and/or maintaining AF by increasing the activity of the inward rectifier K(+) channel.
Collapse
Affiliation(s)
- Min Xia
- Institute of Medical Genetics, Tongji University, Shanghai, China
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Clancy SM, Fowler CE, Finley M, Suen KF, Arrabit C, Berton F, Kosaza T, Casey PJ, Slesinger PA. Pertussis-toxin-sensitive Galpha subunits selectively bind to C-terminal domain of neuronal GIRK channels: evidence for a heterotrimeric G-protein-channel complex. Mol Cell Neurosci 2005; 28:375-89. [PMID: 15691717 DOI: 10.1016/j.mcn.2004.10.009] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2004] [Accepted: 10/25/2004] [Indexed: 11/19/2022] Open
Abstract
Neuronal G-protein-gated inwardly rectifying potassium (Kir3; GIRK) channels are activated by G-protein-coupled receptors that selectively interact with PTX-sensitive (Galphai/o) G proteins. Although the Gbetagamma dimer is known to activate GIRK channels, the role of the Galphai/o subunit remains unclear. Here, we established that Galphao subunits co-immunoprecipitate with neuronal GIRK channels. In vitro binding studies led to the identification of six amino acids in the GIRK2 C-terminal domain essential for Galphao binding. Further studies suggested that the Galphai/obetagamma heterotrimer binds to the GIRK2 C-terminal domain via Galpha and not Gbetagamma. Galphai/o binding-impaired GIRK2 channels exhibited reduced receptor-activated currents, but retained normal ethanol- and Gbetagamma-activated currents. Finally, PTX-insensitive Galphaq or Galphas subunits did not bind to the GIRK2 C-terminus. Together, these results suggest that the interaction of PTX-sensitive Galphai/o subunit with the GIRK2 C-terminal domain regulates G-protein receptor coupling, and may be important for establishing specific Galphai/o signaling pathways.
Collapse
Affiliation(s)
- Sinead M Clancy
- Peptide Biology Laboratory, The Salk Institute for Biological Studies, 10010 N. Torrey Pines Road, La Jolla, CA 92037, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
12
|
Pegan S, Arrabit C, Zhou W, Kwiatkowski W, Collins A, Slesinger PA, Choe S. Cytoplasmic domain structures of Kir2.1 and Kir3.1 show sites for modulating gating and rectification. Nat Neurosci 2005; 8:279-87. [PMID: 15723059 DOI: 10.1038/nn1411] [Citation(s) in RCA: 231] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2004] [Accepted: 01/18/2005] [Indexed: 11/08/2022]
Abstract
N- and C-terminal cytoplasmic domains of inwardly rectifying K (Kir) channels control the ion-permeation pathway through diverse interactions with small molecules and protein ligands in the cytoplasm. Two new crystal structures of the cytoplasmic domains of Kir2.1 (Kir2.1(L)) and the G protein-sensitive Kir3.1 (Kir3.1(S)) channels in the absence of PIP(2) show the cytoplasmic ion-permeation pathways occluded by four cytoplasmic loops that form a girdle around the central pore (G-loop). Significant flexibility of the pore-facing G-loop of Kir2.1(L) and Kir3.1(S) suggests a possible role as a diffusion barrier between cytoplasmic and transmembrane pores. Consistent with this, mutations of the G-loop disrupted gating or inward rectification. Structural comparison shows a di-aspartate cluster on the distal end of the cytoplasmic pore of Kir2.1(L) that is important for modulating inward rectification. Taken together, these results suggest the cytoplasmic domains of Kir channels undergo structural changes to modulate gating and inward rectification.
Collapse
Affiliation(s)
- Scott Pegan
- Structural Biology, The Salk Institute, La Jolla, California 92037, USA
| | | | | | | | | | | | | |
Collapse
|
13
|
Ivanina T, Varon D, Peleg S, Rishal I, Porozov Y, Dessauer CW, Keren-Raifman T, Dascal N. Gαi1 and Gαi3 Differentially Interact with, and Regulate, the G Protein-activated K+ Channel. J Biol Chem 2004; 279:17260-8. [PMID: 14963032 DOI: 10.1074/jbc.m313425200] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
G protein-activated K(+) channels (GIRKs; Kir3) are activated by direct binding of Gbetagamma subunits released from heterotrimeric G proteins. In native tissues, only pertussis toxin-sensitive G proteins of the G(i/o) family, preferably Galpha(i3) and Galpha(i2), are donors of Gbetagamma for GIRK. How this specificity is achieved is not known. Here, using a pull-down method, we confirmed the presence of Galpha(i3-GDP) binding site in the N terminus of GIRK1 and identified novel binding sites in the N terminus of GIRK2 and in the C termini of GIRK1 and GIRK2. The non-hydrolyzable GTP analog, guanosine 5'-3-O-(thio)triphosphate, reduced the binding of Galpha(i3) by a factor of 2-4. Galpha(i1-GDP) bound to GIRK1 and GIRK2 much weaker than Galpha(i3-GDP). Titrated expression of components of signaling pathway in Xenopus oocytes and their activation by m2 muscarinic receptors revealed that G(i3) activates GIRK more efficiently than G(i1), as indicated by larger and faster agonist-evoked currents. Activation of GIRK by purified Gbetagamma in excised membrane patches was strongly augmented by coexpression of Galpha(i3) and less by Galpha(i1). Differences in physical interactions of GIRK with GDP-bound Galpha subunits, or Galphabetagamma heterotrimers, may dictate different extents of Galphabetagamma anchoring, influence the efficiency of GIRK activation by Gbetagamma, and play a role in determining signaling specificity.
Collapse
MESH Headings
- Amino Acid Sequence
- Animals
- Binding Sites
- Cell Membrane/metabolism
- DNA, Complementary/metabolism
- G Protein-Coupled Inwardly-Rectifying Potassium Channels
- GTP-Binding Protein alpha Subunit, Gi2
- GTP-Binding Protein alpha Subunits, Gi-Go/chemistry
- GTP-Binding Protein alpha Subunits, Gi-Go/metabolism
- GTP-Binding Protein beta Subunits/metabolism
- GTP-Binding Protein gamma Subunits/metabolism
- Glutathione Transferase/metabolism
- Models, Genetic
- Models, Molecular
- Molecular Sequence Data
- Oocytes/metabolism
- Pertussis Toxin/pharmacology
- Potassium Channels/chemistry
- Potassium Channels, Inwardly Rectifying
- Protein Binding
- Protein Structure, Tertiary
- Proto-Oncogene Proteins/chemistry
- Proto-Oncogene Proteins/metabolism
- Receptor, Muscarinic M2/metabolism
- Recombinant Fusion Proteins/metabolism
- Sequence Homology, Amino Acid
- Signal Transduction
- Time Factors
- Xenopus laevis
Collapse
Affiliation(s)
- Tatiana Ivanina
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Ramat Aviv 69978, Israel
| | | | | | | | | | | | | | | |
Collapse
|
14
|
Sadja R, Alagem N, Reuveny E. Gating of GIRK channels: details of an intricate, membrane-delimited signaling complex. Neuron 2003; 39:9-12. [PMID: 12848928 DOI: 10.1016/s0896-6273(03)00402-1] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
G protein-coupled inwardly rectifying potassium channels (GIRK/Kir3) are important elements in controlling cellular excitability. In recent years, tremendous progress has been made toward understanding various components involved in channel activation, modulation, and signaling specificity. In this review, we summarize these recent findings and attempt to put them in context with recently available structural data.
Collapse
Affiliation(s)
- Rona Sadja
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, Israel
| | | | | |
Collapse
|
15
|
Riven I, Kalmanzon E, Segev L, Reuveny E. Conformational Rearrangements Associated with the Gating of the G Protein-Coupled Potassium Channel Revealed by FRET Microscopy. Neuron 2003; 38:225-35. [PMID: 12718857 DOI: 10.1016/s0896-6273(03)00193-4] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
G protein-coupled potassium channels (GIRK/Kir3.x) are key determinants that translate inhibitory chemical neurotransmission into changes in cellular excitability. To understand the mechanism of channel activation by G proteins, it is necessary to define the structural rearrangements in the channel that result from interaction with Gbetagamma subunits. In this study we used a combination of fluorescence spectroscopy and through-the-objective total internal reflection microscopy to monitor the conformational rearrangements associated with the activation of GIRK channels in single intact cells. We detect activation-induced changes in FRET consistent with a rotation and expansion of the termini along the central axis of the channel. We propose that this rotation and expansion of the termini drives the channel to open by bending and possibly rotating the second transmembrane segment.
Collapse
Affiliation(s)
- Inbal Riven
- Department of Biological Chemistry, Weizmann Institute of Science, 76100, Rehovot, Israel
| | | | | | | |
Collapse
|