G Protein-Activated Inward Rectifier Potassium Channel 1 (GIRK1/KCNJ3)

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G Protein-Activated Inward Rectifier Potassium Channel 1 (GIRK1/KCNJ3)

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G Protein-Activated Inward Rectifier Potassium Channel 1 (GIRK1/KCNJ3)

<table class="infobox infobox-protein">
<tr>
<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>
<tr>
<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>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">13 edges</a></td>
</tr>
</table>

...

G Protein-Activated Inward Rectifier Potassium Channel 1 (GIRK1/KCNJ3)

<table class="infobox infobox-protein">
<tr>
<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>
<tr>
<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>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">13 edges</a></td>
</tr>
</table>

<div style="float: right; margin: 0 0 1em 1em; padding: 1em; background: #f8f9fa; border: 1px solid #ddd; border-radius: 8px; font-size: 0.9em; max-width: 300px;">
<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 rate

Neuronal 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.

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)

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Related Entities

KCNJ3PROTEIN

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slug	proteins-kcnj3-protein
kg_node_id	KCNJ3PROTEIN
entity_type	protein
origin_type	v1_polymorphic_backfill
source_table	wiki_pages
wiki_page_id	wp-c9fa98ded656
__merged_from	{'merged_at': '2026-05-13', 'unprefixed_id': 'proteins-kcnj3-protein'}
_schema_version	1

📊 Evidence Profile Foundational

Evidence Balance

+0%

Certainty

95%

Debates

0

Incoming

19

Outgoing

20

0 supporting 0 contradicting 0 neutral

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📗 Cite This Artifact

G Protein-Activated Inward Rectifier Potassium Channel 1 (GIRK1/KCNJ3)

G Protein-Activated Inward Rectifier Potassium Channel 1 (GIRK1/KCNJ3)

G Protein-Activated Inward Rectifier Potassium Channel 1 (GIRK1/KCNJ3)

Overview

Structure and Domain Architecture

Transmembrane Domains

Pore Region (residues ~115-145)

Cytoplasmic Domains

N-Terminal Domain (residues 1-86)

C-Terminal Domain (residues 166-501)

Tetrameric Assembly

Normal Function in the Nervous System

Inhibitory Neurotransmission

Neuronal Excitability Regulation

Synaptic Plasticity

Neurotransmitter Systems

Role in Neurodegeneration

Alzheimer's Disease

Expression Changes

Pathophysiological Effects

Aβ Effects on GIRK

Parkinson's Disease

Dopamine-GIRK Interaction

Neuroprotective Potential

Epilepsy

Addiction and Reward

Therapeutic Targeting

GIRK Modulators

Disease-Targeted Approaches

Drug Development Challenges

Protein-Protein Interactions

Summary

See Also

External Links

References

💬 Discussion