G Protein-Activated Inward Rectifier Potassium Channel 1 (GIRK1/KCNJ3)
<table class="infobox infobox-protein">
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<th class="infobox-header" colspan="2">G Protein-Activated Inward Rectifier Potassium Channel 1 (GIRK1/KCNJ3)</th>
</tr>
<tr>
<td class="label">Interactor</td>
<td>Function</td>
</tr>
<tr>
<td class="label">GIRK2/KCNJ6</td>
<td>Heterotetramer formation</td>
</tr>
<tr>
<td class="label">GIRK3/KCNJ9</td>
<td>Heterotetramer formation</td>
</tr>
<tr>
<td class="label">GIRK4/KCNJ5</td>
<td>Heterotetramer formation</td>
</tr>
<tr>
<td class="label">Gβγ subunits</td>
<td>Direct activation</td>
</tr>
<tr>
<td class="label">PIP2</td>
<td>Channel gating</td>
</tr>
<tr>
<td class="label">GABA-B R2</td>
<td>Receptor coupling</td>
</tr>
<tr>
<td class="label">μ-opioid receptor</td>
<td>Receptor coupling</td>
</tr>
<tr>
<td class="label">M2 receptor</td>
<td>Receptor coupling</td>
</tr>
<tr>
<td class="label">PDZ proteins</td>
<td>Scaffolding</td>
</tr>
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<td class="label">Associated Diseases</td>
<td><a href="/wiki/aging" style="color:#ef9a9a">Aging</a>, <a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/autism" style="color:#ef9a9a">Autism</a>, <a href="/wiki/cancer" style="color:#ef9a9a">Cancer</a>, <a href="/wiki/ms" style="color:#ef9a9a">Ms</a></td>
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<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">13 edges</a></td>
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<h3 style="margin-top: 0; border-bottom: 1px solid #ccc;">KCNJ3/GIRK1 Protein</h3>
<table style="width: 100%; border-collapse: collapse;">
<tr><td style="padding: 4px 8px;"><strong>Gene</strong></td><td>[KCNJ3](/genes/kcnj3)</td></tr>
<tr><td style="padding: 4px 8px;"><strong>UniProt ID</strong></td><td>[P48051](https://www.uniprot.org/uniprot/P48051)</td></tr>
<tr><td style="padding: 4px 8px;"><strong>PDB Structures</strong></td><td>[6VKG](https://www.rcsb.org/structure/6VKG), [6VIC](https://www.rcsb.org/structure/6VIC)</td></tr>
<tr><td style="padding: 4px 8px;"><strong>Molecular Weight</strong></td><td>56.7 kDa</td></tr>
<tr><td style="padding: 4px 8px;"><strong>Amino Acids</strong></td><td>501</td></tr>
<tr><td style="padding: 4px 8px;"><strong>Subcellular Location</strong></td><td>Plasma membrane</td></tr>
<tr><td style="padding: 4px 8px;"><strong>Protein Family</strong></td><td>Inward rectifier potassium channel (Kir) family</td></tr>
</table>
</div>
Overview
G protein-activated inward rectifier potassium channel 1 (GIRK1), also known as Kir3.1 or KCNJ3, is a 56 kDa inward-rectifying potassium channel subunit that forms ligand-gated potassium channels activated by G protein-coupled receptors (GPCRs)[@kubo1993]. Encoded by the [KCNJ3](/genes/kcnj3) gene on chromosome 2q24.1, GIRK1 assembles with other GIRK subunits (GIRK2/KCNJ6, GIRK3/KCNJ9, GIRK4/KCNJ5) to form heterotetrameric channels that mediate slow inhibitory postsynaptic potentials in [neurons](/entities/neurons)[@kofuji1995].
GIRK channels are critical regulators of neuronal excitability, coupling inhibitory neurotransmitter receptors (GABA-B, M2 muscarinic, μ-opioid) to membrane hyperpolarization through direct Gβγ subunit binding[@wickman1994]. In the nervous system, GIRK1-containing channels regulate action potential firing, neurotransmitter release, and synaptic plasticity, making them important players in neurological disorders including epilepsy, addiction, and neurodegenerative diseases[@lscher2010].
Structure and Domain Architecture
GIRK1 forms homotetrameric or heterotetrameric channels with characteristic inward rectifier architecture[@whorton2013]:
Transmembrane Domains
- TM1 (residues ~87-107): First transmembrane helix
- TM2 (residues ~145-165): Second transmembrane helix containing the pore
Pore Region (residues ~115-145)
- Selectivity filter: GYG (Gly-Tyr-Gly) motif at positions 142-144
- P-loop: Forms the K+ conduction pathway
- Signature sequence: T-X-G-Y/F-G motif characteristic of K+ channels
Cytoplasmic Domains
N-Terminal Domain (residues 1-86)
- N-terminal helix: Contributes to Gβγ binding
- Tetra-Golgi trafficking signals: Influences channel localization
C-Terminal Domain (residues 166-501)
- Gβγ binding site: Critical for channel activation
- PIP2 binding site: Required for channel opening
- Phosphorylation sites: PKA and PKC regulatory sites
- PDZ-binding motif: C-terminal E-S/K-V sequence for protein interactions
Tetrameric Assembly
- Forms heterotetramers primarily with GIRK2 (Kir3.1/Kir3.2)
- GIRK1/GIRK2 channels are the predominant neuronal isoform
- Each subunit contributes to central pore formation
Normal Function in the Nervous System
Inhibitory Neurotransmission
GIRK1-containing channels mediate slow inhibitory postsynaptic potentials[@lscher1997]:
GABA-B receptor coupling: GABA release → GABA-B activation → Gi/o protein → Gβγ → GIRK opening
Membrane hyperpolarization: K+ efflux hyperpolarizes neurons below threshold
Reduced excitability: Decreased action potential firing rateNeuronal Excitability Regulation
GIRK channels provide tonic inhibitory tone via[@chen2018]:
- Basal activity: Constitutive PIP2-dependent activity
- Leak conductance: Maintains resting membrane potential
- Input resistance modulation: Shapes synaptic integration
Synaptic Plasticity
GIRK1 channels influence synaptic function through[@chung2006]:
- Spike frequency adaptation: Limits sustained firing
- Dendritic integration: Shapes EPSP propagation
- Paired-pulse modulation: Affects short-term plasticity
Neurotransmitter Systems
GIRK1 is coupled to multiple inhibitory receptor systems[@marker1996]:
- GABA-B receptors: Primary inhibitory neurotransmitter
- M2/M4 muscarinic receptors: Cholinergic modulation
- μ-opioid receptors: Analgesic signaling
- D2/D4 dopamine receptors: Dopaminergic inhibition
- A1 adenosine receptors: Adenosine-mediated suppression
Role in Neurodegeneration
Alzheimer's Disease
GIRK1 function is altered in AD[@ohno2006]:
Expression Changes
- Reduced expression: Decreased KCNJ3 mRNA in AD [hippocampus](/brain-regions/hippocampus)
- Membrane localization: Impaired trafficking to synapses
- Post-translational modifications: Altered phosphorylation status
Pathophysiological Effects
- Excitatory/inhibitory imbalance: Loss of inhibitory tone
- Seizure susceptibility: Increased hyperexcitability in AD models
- Synaptic dysfunction: Impaired GABA-B signaling
Aβ Effects on GIRK
- [Aβ](/proteins/amyloid-beta) oligomers: Reduce GIRK current amplitude
- Receptor uncoupling: Impaired GPCR-GIRK signaling
- Oxidative damage: Channel cysteine modification
Parkinson's Disease
GIRK1 roles in basal ganglia circuitry[@kuzhikandathil2002]:
Dopamine-GIRK Interaction
- D2 receptor coupling: Dopamine inhibits striatal neurons via GIRK
- Reward circuitry: GIRK in ventral tegmental area
- Motor control: Basal ganglia output regulation
Neuroprotective Potential
- Excitotoxicity protection: Limits glutamate-mediated damage
- Inflammation modulation: GABA-B-GIRK anti-inflammatory effects
Epilepsy
GIRK1 dysfunction in seizure disorders[@millichap2016]:
- KCNJ3 mutations: Associated with idiopathic generalized epilepsy
- GABA-B-GIRK pathway: Impaired in temporal lobe epilepsy
- Antiepileptic mechanisms: Enhanced GIRK activity reduces seizures
Addiction and Reward
GIRK1 in substance use disorders[@laboube2007]:
- Opioid-GIRK coupling: Mediates analgesia and tolerance
- Alcohol effects: GIRK modulation by ethanol
- Drug reward pathway: VTA GIRK in addiction circuitry
Therapeutic Targeting
GIRK Modulators
Positive modulators (GIRK activators)[@kaufmann2013]:
- ML297: Selective GIRK1/2 activator, anxiolytic effects
- Naringenin: Natural flavonoid with GIRK activity
- Ethanol: Potentiates GIRK at intoxicating concentrations
Negative modulators (GIRK inhibitors)[@jin1998]:
- SCH-23390: D1 antagonist that blocks GIRK
- Tertiapin: Peptide toxin GIRK blocker
- Ba²⁺ ions: Classical inward rectifier blocker
Disease-Targeted Approaches
Epilepsy treatment[@signorini1997]:
- GIRK enhancers as anticonvulsants
- GABA-B agonists + GIRK potentiation
Addiction therapy[@torrecilla2008]:
- GIRK modulators for opioid use disorder
- Alcohol use disorder treatment
Pain management[@marker2010]:
- Opioid-sparing GIRK activation
- Chronic pain modulation
Drug Development Challenges
- Subtype selectivity: Need for GIRK1-specific compounds
- [Blood-brain barrier](/entities/blood-brain-barrier): CNS penetration requirements
- Cardiac effects: Avoid GIRK4 (cardiac) cross-reactivity
Protein-Protein Interactions
Summary
GIRK1 is a critical component of neuronal inhibitory signaling, coupling G protein-coupled receptors to membrane hyperpolarization through potassium efflux. As a primary mediator of slow inhibitory postsynaptic potentials, GIRK1-containing channels regulate neuronal excitability, synaptic plasticity, and network synchronization. Dysregulation of GIRK1 function contributes to epilepsy, addiction, and neurodegenerative diseases, making GIRK modulation an attractive therapeutic target.
See Also
- KCNJ3 Gene
- GIRK2/KCNJ6 Protein
- [Ion Channels in Neurodegeneration](/mechanisms/ion-channel-dysfunction)
- [GABAergic Signaling](/mechanisms/gabaergic-signaling)
- [Epilepsy](/diseases/epilepsy)
- [Alzheimer's Disease](/diseases/alzheimers-disease)
External Links
- [UniProt: P48051](https://www.uniprot.org/uniprot/P48051)
- [NCBI Gene: 3760](https://www.ncbi.nlm.nih.gov/gene/3760)
- [IUPHAR: Kir3.1](https://www.guidetopharmacology.org/GRAC/ObjectDisplayForward?objectId=507)
References
[Kubo Y, Reuveny E, Slesinger PA, et al, Primary structure and functional expression of a rat G-protein-coupled muscarinic potassium channel (1993)](https://doi.org/10.1038/364802a0)
[Kofuji P, Davidson N, Lester HA, Evidence that neuronal G-protein-gated inwardly rectifying K+ channels are activated by Gβγ subunits and function as heteromultimers (1995)](https://doi.org/10.1073/pnas.92.14.6542)
[Wickman KD, Iñiguez-Lluhl JA, Davenport PA, et al, Recombinant G-protein βγ-subunits activate the muscarinic-gated atrial potassium channel (1994)](https://doi.org/10.1038/368255a0)
[Lüscher C, Slesinger PA, Emerging roles for G protein-gated inwardly rectifying potassium (GIRK) channels in health and disease (2010)](https://doi.org/10.1038/nrn2816)
[Whorton MR, MacKinnon R, Crystal structure of the mammalian GIRK2-βγ G-protein complex (2013)](https://doi.org/10.1038/nature12241)
[Lüscher C, Jan LY, Stoffel M, et al, G protein-coupled inwardly rectifying K+ channels (GIRKs) mediate postsynaptic but not presynaptic transmitter actions in hippocampal neurons (1997)](https://doi.org/10.1016/S0896-6273(00)
[Chen SC, Ehrlich BE, G protein-gated inwardly rectifying K+ channels and neuronal excitability (2018)](https://doi.org/10.1152/physiol.00003.2018)
[Chung HJ, Jan YN, Jan LY, Polarized axonal surface expression of neuronal KCNQ channels is mediated by multiple signals in the KCNQ2 and KCNQ3 C-terminal domains (2006)](https://doi.org/10.1073/pnas.0603376103)
[marker Y, Karschin C, Ross EM, et al, G protein-gated K+ channels: conserved subunit composition (1996)](https://doi.org/10.1074/jbc.271.50.32317)
[Ohno M, Sametsky EA, Silva AJ, Disterhoft JF, Differential effects of α-CaMKII mutation on hippocampal-dependent learning and memory in young and aged mice (2006)](https://doi.org/10.1523/JNEUROSCI.3244-05.2006)
[Kuzhikandathil EV, Oxford GS, Classic D1 dopamine receptor antagonist R-(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine (SCH-23390) directly inhibits G protein-coupled inwardly rectifying potassium channels (2002)](https://doi.org/10.1124/mol.62.1.119)
[Millichap JJ, Liu HL, Puri R, et al, KCNJ3 mutations in epilepsy (2016)](https://doi.org/10.1002/ana.24647)
[Labouèbe G, Lomazzi M, Cruz HG, et al, RGS2 modulates coupling between GABA-B receptors and GIRK channels in dopamine neurons of the ventral tegmental area (2007)](https://doi.org/10.1038/nn2006)
[Kaufmann K, Romaine I, Days E, et al, ML297 (VU0456810), the first potent and selective activator of the GIRK potassium channel, displays antiepileptic properties in rodents (2013)](https://doi.org/10.1021/cn400062a)
[Jin W, Lu Z, A novel high-affinity inhibitor for inward-rectifier K+ channels (1998)](https://doi.org/10.1021/bi981178p)
[Signorini S, Liao YJ, Duncan SA, et al, Normal cerebellar development but susceptibility to seizures in mice lacking G protein-coupled, inwardly rectifying K+ channel GIRK2 (1997)](https://doi.org/10.1073/pnas.94.3.923)
[Torrecilla M, Marker CL, Cintora SC, et al, G-protein-gated inwardly rectifying potassium channels contain DLP4 motif required for behavioral effects of ethanol (2008)](https://doi.org/10.1038/nn2105)
[Marker CL, Laitinen K, Arar M, Wickman K, GIRK1 and GIRK2 in the brain: implications for analgesia (2010)](https://doi.org/10.1016/j.pain.2010.08.044)