GIRK2/Kir2.2 — G Protein-Activated Inward Rectifier Potassium Channel 2

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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

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.

Protein Information

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 function

Molecular 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 design

Key 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.

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

[[1]](https://pubmed.ncbi.nlm.nih.gov/9069261/) Luscher C, et al. GABAB receptor agonist and antagonist actions on GIRK currents. Proc Natl Acad Sci. 1997;94(8):4131-4136.

[[2]](https://pubmed.ncbi.nlm.nih.gov/16236724/) Marker CL, et al. GIRK channels mediate dopamine D2 receptor signaling. J Neurosci. 2005;25(42):10017-10025.

[[3]](https://pubmed.ncbi.nlm.nih.gov/8528741/) Slesinger PA, et al. Functional effects of the weaver mutation in GIRK2 channels. Neuron. 1995;15(6):1243-1248.

[[4]](https://pubmed.ncbi.nlm.nih.gov/9856964/) Cruzblanca H, et al. G protein gating of GIRK channels. EMBO J. 1998;17(20):5887-5895.

[[5]](https://pubmed.ncbi.nlm.nih.gov/16376916/) Koyrakh L, et al. Molecular and cellular diversity of GIRK channel function. Curr Neuropharmacol. 2005;3(1):1-19.

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GIRK2/Kir2.2 — G Protein-Activated Inward Rectifier Potassium Channel 2

GIRK2/Kir2.2 — G Protein-Activated Inward Rectifier Potassium Channel 2

Introduction

GIRK2/Kir2.2 — G Protein-Activated Inward Rectifier Potassium Channel 2

Introduction

Overview

Protein Information

Structure

Expression Pattern

Normal Function

Molecular Mechanisms

G-Protein Activation

Signaling Integration

Role in Disease

Parkinson's Disease

Other Neurological Conditions

Developmental Disorders

Therapeutic Targeting

Challenges

Animal Models

Research Directions

Key Publications

See Also

External Links

Background

References