GIRK2/Kir2.2 — G Protein-Activated Inward Rectifier Potassium Channel 2
<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">GIRK2/Kir2.2 — G Protein-Activated Inward Rectifier Potassium Channel 2</th>
</tr>
<tr>
<td class="label">
Protein Name</td>
<td>GIRK2 (G Protein-Activated Inward Rectifier Potassium Channel 2)</td>
</tr>
<tr>
<td class="label">
Gene</td>
<td>KCNJ6</td>
</tr>
<tr>
<td class="label">
UniProt ID</td>
<td>P48051</td>
</tr>
<tr>
<td class="label">
PDB Structure</td>
<td>7R0F, 7V6S</td>
</tr>
<tr>
<td class="label">
Molecular Weight</td>
<td>~50 kDa</td>
</tr>
<tr>
<td class="label">
Subcellular Localization</td>
<td>Plasma membrane, [dendritic spines](/cell-types/dendritic-spines), axon terminals</td>
</tr>
<tr>
<td class="label">
Protein Family</td>
<td>Inward rectifier potassium channel (Kir2.x)</td>
</tr>
<tr>
<td class="label">Strategy</td>
<td>Compound</td>
</tr>
<tr>
<td class="label">Blocker</td>
<td>Tertiapin-Q</td>
</tr>
<tr>
<td class="label">Allosteric modulator</td>
<td>GIRK activator</td>
</tr>
<tr>
<td class="label">Gene therapy</td>
<td>AAV-GIRK2</td>
</tr>
<tr>
<td class="label">Neuroprotection</td>
<td>Small molecules</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>
Introduction
...GIRK2/Kir2.2 — G Protein-Activated Inward Rectifier Potassium Channel 2
<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">GIRK2/Kir2.2 — G Protein-Activated Inward Rectifier Potassium Channel 2</th>
</tr>
<tr>
<td class="label">
Protein Name</td>
<td>GIRK2 (G Protein-Activated Inward Rectifier Potassium Channel 2)</td>
</tr>
<tr>
<td class="label">
Gene</td>
<td>KCNJ6</td>
</tr>
<tr>
<td class="label">
UniProt ID</td>
<td>P48051</td>
</tr>
<tr>
<td class="label">
PDB Structure</td>
<td>7R0F, 7V6S</td>
</tr>
<tr>
<td class="label">
Molecular Weight</td>
<td>~50 kDa</td>
</tr>
<tr>
<td class="label">
Subcellular Localization</td>
<td>Plasma membrane, [dendritic spines](/cell-types/dendritic-spines), axon terminals</td>
</tr>
<tr>
<td class="label">
Protein Family</td>
<td>Inward rectifier potassium channel (Kir2.x)</td>
</tr>
<tr>
<td class="label">Strategy</td>
<td>Compound</td>
</tr>
<tr>
<td class="label">Blocker</td>
<td>Tertiapin-Q</td>
</tr>
<tr>
<td class="label">Allosteric modulator</td>
<td>GIRK activator</td>
</tr>
<tr>
<td class="label">Gene therapy</td>
<td>AAV-GIRK2</td>
</tr>
<tr>
<td class="label">Neuroprotection</td>
<td>Small molecules</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>
Introduction
Girk2 Kir2.2 — G Protein Activated Inward Rectifier Potassium Channel 2 is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
Overview
GIRK2 (Kir2.2, encoded by KCNJ6) is a G protein-activated inward rectifier potassium channel highly expressed in dopaminergic [neurons](/entities/neurons) of the substantia nigra pars compacta (SNpc). This channel is critical for regulating neuronal excitability and has been strongly implicated in Parkinson's disease pathogenesis. GIRK2 forms the canonical inward rectifier channel that mediates dopamine D2 receptor-induced hyperpolarization, making it essential for dopaminergic signaling and neuron survival.
Structure
GIRK2 forms homotetramers or heterotetramers with other Kir2.x subunits:
- Four transmembrane domains: M1 and M2 helices form the channel pore
- Selectivity filter: GYG motif confers K+ selective permeation
- Cytoplasmic domains: N-terminus and C-terminus interact with G-protein beta-gamma subunits
- Phosphorylation sites: Multiple serine/threonine residues regulated by kinases
- PIP2 binding site: Required for channel activation and trafficking
- Gβγ binding domain: Cytoplasmic loop mediates G-protein activation
Expression Pattern
GIRK2 exhibits highly specific expression patterns:
- Brain: Highest expression in substantia nigra pars compacta, ventral tegmental area, [hippocampus](/brain-regions/hippocampus), and cerebral [cortex](/brain-regions/cortex)
- Dopaminergic neurons: Very high expression in SNpc and VTA dopaminergic neurons
- Other neurons: Medium spiny neurons in striatum, cerebellar Purkinje cells
- Peripheral tissues: Heart, endocrine glands, pancreas
- Subcellular: Primarily plasma membrane, with enrichment in [dendritic spines](/mechanisms/dendritic-spines) and axon terminals
Normal Function
GIRK2 channels serve critical physiological roles:
Dopaminergic neuron regulation: Maintains resting membrane potential in SNpc neurons
GPCR signaling: Activated by Gi/o-coupled receptors (dopamine D2, adenosine A1, GABA-B, opioid)
Synaptic inhibition: Mediates inhibitory postsynaptic responses through G-protein signaling
Neuroprotection: Controls Ca2+ influx via membrane potential regulation
Reward processing: Modulates VTA neuron firing and dopamine release
Motor control: Influences basal ganglia circuit functionMolecular Mechanisms
G-Protein Activation
GIRK2 activation occurs through:
- Gβγ subunits: Released from Gi/o-coupled receptors, bind directly to GIRK2
- Channel opening: Gβγ binding increases open probability
- Voltage dependence: Strong inward rectification limits outward current
- Recovery: GTP hydrolysis terminates the signal
Signaling Integration
- D2 autoreceptor feedback: Dopamine binds D2 receptors, activating GIRK2 and reducing firing
- Adenosinergic modulation: A1 receptor activation hyperpolarizes neurons
- Metabotropic signaling: GIRK2 integrates multiple GPCR inputs
Role in Disease
Parkinson's Disease
GIRK2 is central to PD pathogenesis:
- Selective vulnerability: SNpc neurons highly express GIRK2, making them susceptible
- Mechanism: Channel dysfunction leads to increased excitability and excitotoxicity
- Weaver mouse: Natural KCNJ6 gain-of-function mutation causes dopaminergic neurodegeneration
- Therapeutic target: GIRK2 modulators may protect dopaminergic neurons
- Levodopa response: Altered GIRK2 function may contribute to motor complications
Other Neurological Conditions
- Epilepsy: Altered GIRK2 expression in epileptic hippocampus
- Addiction: Role in reward circuitry and dopamine signaling
- Depression: GIRK2 variants associated with major depressive disorder
- Schizophrenia: Altered GIRK2 function in prefrontal cortex
Developmental Disorders
- Keppen-Lubinsky syndrome: Rare KCNJ6 mutations cause severe developmental delay
Therapeutic Targeting
Challenges
- Achieving specificity for GIRK2 over other Kir2.x channels
- Brain penetration with therapeutic compounds
- Balancing neuronal excitability modulation
Animal Models
- Weaver mouse: Natural Girk2 mutation (GIRK2 gain-of-function), dopaminergic neuron loss
- Kcnj6 knockout mice: Viable with altered dopaminergic signaling
- Transgenic overexpression: Mouse models showing PD-like phenotypes
- Conditional knockouts: Brain-specific deletion studies
Research Directions
Selective modulators: Developing GIRK2-specific therapeutic compounds
Gene therapy: AAV-mediated delivery to SNpc neurons
Biomarker potential: GIRK2 expression as dopaminergic neuron marker
Combination therapy: Targeting GIRK2 with other PD therapeutics
Structural studies: Cryo-EM for drug designKey Publications
Luscher C, et al. (1997). GABAB receptor agonist and antagonist actions on GIRK currents. Proc Natl Acad Sci 94:4131-4136.
Marker CL, et al. (2005). GIRK channels mediate dopamine D2 receptor signaling. J Neurosci 25:10017-10025.
Slesinger PA, et al. (1995). Functional effects of the weaver mutation in GIRK2 channels. Neuron 15:1243-1248.
Cruzblanca H, et al. (1998). G protein gating of GIRK channels. EMBO J 17:5887-5895.
Koyrakh L, et al. (2005). Molecular and cellular diversity of GIRK channel function. Curr Neuropharmacol 3:1-19.See Also
- [KCNJ6 Gene](/proteins/kcnj6-protein)
- [Parkinson's Disease](/diseases/parkinsons-disease)
- [Substantia Nigra Pars Compacta](/cell-types/substantia-nigra-pars-compacta)
- [Dopaminergic Vulnerability Pathway](/mechanisms/dopaminergic-vulnerability)
- [Potassium Channel Dysfunction](/mechanisms/potassium-channel-dysfunction)
- [Inward Rectifier Potassium Channels](/proteins/kir2-3)
- [Ventral Tegmental Area](/brain-regions/ventral-tegmental-area)
External Links
- [UniProt P48051](https://www.uniprot.org/uniprot/P48051)
- [PDB 7R0F](https://www.rcsb.org/structure/7R0F)
- [GeneCards KCNJ6](https://www.genecards.org/cgi-bin/carddisp.pl?gene=KCNJ6)
- [OMIM 600734](https://www.omim.org/entry/600734)
Background
The study of Girk2 Kir2.2 — G Protein Activated Inward Rectifier Potassium Channel 2 has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
References
<sup>[[1]](https://pubmed.ncbi.nlm.nih.gov/9069261/)</sup> Luscher C, et al. GABAB receptor agonist and antagonist actions on GIRK currents. Proc Natl Acad Sci. 1997;94(8):4131-4136.
<sup>[[2]](https://pubmed.ncbi.nlm.nih.gov/16236724/)</sup> Marker CL, et al. GIRK channels mediate dopamine D2 receptor signaling. J Neurosci. 2005;25(42):10017-10025.
<sup>[[3]](https://pubmed.ncbi.nlm.nih.gov/8528741/)</sup> Slesinger PA, et al. Functional effects of the weaver mutation in GIRK2 channels. Neuron. 1995;15(6):1243-1248.
<sup>[[4]](https://pubmed.ncbi.nlm.nih.gov/9856964/)</sup> Cruzblanca H, et al. G protein gating of GIRK channels. EMBO J. 1998;17(20):5887-5895.
<sup>[[5]](https://pubmed.ncbi.nlm.nih.gov/16376916/)</sup> Koyrakh L, et al. Molecular and cellular diversity of GIRK channel function. Curr Neuropharmacol. 2005;3(1):1-19.