Kir2.2 Potassium Channel

Kir2.2 (Potassium Inwardly Rectifying Channel Subfamily J Member 12)

Introduction

Kir2.2 Potassium Channel 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

<div class="infobox infobox-protein"> [@bichet2003]
<table> [@lopatin2001]
<tr><th>Protein Name</th><td>Kir2.2</td></tr> [@john]
<tr><th>Gene</th><td>[KCNJ12](/genes/kcnj12)</td></tr>
<tr><th>UniProt ID</th><td>[P48745](https://www.uniprot.org/uniprot/P48745)</td></tr>
<tr><th>PDB Structure</th><td>3JYC, 3SPG</td></tr>
<tr><th>Molecular Weight</th><td>~48 kDa</td></tr>
<tr><th>Subcellular Localization</th><td>Plasma membrane</td></tr>
<tr><th>Protein Family</th><td>Inwardly rectifying potassium channel (Kir) family</td></tr>
</table>
</div>

Structure

Kir2.2 is an inwardly rectifying potassium channel:

Domain Organization

• Two transmembrane domains: M1 and M2
• Pore loop (H5/ selectivity filter): K+ selective
• N-terminus and C-terminus: Cytoplasmic domains
• Tetrameric assembly: 4 subunits form functional channel

Structural Features

• Slide helix: G-loop in M2
• selectivity filter: TVGYG signature
• N-terminal gating: PID domain
• Phosphorylation sites: Regulatory

Normal Function

Kir2.2 channels regulate neuronal excitability:

...

Kir2.2 (Potassium Inwardly Rectifying Channel Subfamily J Member 12)

Introduction

Kir2.2 Potassium Channel 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

<div class="infobox infobox-protein"> [@bichet2003]
<table> [@lopatin2001]
<tr><th>Protein Name</th><td>Kir2.2</td></tr> [@john]
<tr><th>Gene</th><td>[KCNJ12](/genes/kcnj12)</td></tr>
<tr><th>UniProt ID</th><td>[P48745](https://www.uniprot.org/uniprot/P48745)</td></tr>
<tr><th>PDB Structure</th><td>3JYC, 3SPG</td></tr>
<tr><th>Molecular Weight</th><td>~48 kDa</td></tr>
<tr><th>Subcellular Localization</th><td>Plasma membrane</td></tr>
<tr><th>Protein Family</th><td>Inwardly rectifying potassium channel (Kir) family</td></tr>
</table>
</div>

Structure

Kir2.2 is an inwardly rectifying potassium channel:

Domain Organization

• Two transmembrane domains: M1 and M2
• Pore loop (H5/ selectivity filter): K+ selective
• N-terminus and C-terminus: Cytoplasmic domains
• Tetrameric assembly: 4 subunits form functional channel

Structural Features

• Slide helix: G-loop in M2
• selectivity filter: TVGYG signature
• N-terminal gating: PID domain
• Phosphorylation sites: Regulatory

Normal Function

Kir2.2 channels regulate neuronal excitability:

Electrophysiological Properties

• Inward rectification: Strong inward current at negative potentials
• Resting potential: Sets resting membrane potential near EK+
• Input resistance: Determines neuronal input resistance
• Time constant: Affects integration of synaptic inputs

Physiological Roles

• Neuronal rest maintenance: Maintains hyperpolarized resting potential
• K+ homeostasis: Regulates extracellular K+ levels
• Excitability control: Modulates action potential threshold
• Development: Neural tube closure

Role in Disease

Neurodevelopmental Disorders

KCNJ12 mutations associated with:

• Developmental delay: Intellectual disability
• Autism spectrum disorder: Social communication deficits
• Epilepsy: Various seizure types

Neurodegeneration Links

While primarily developmental, Kir2.2 has implications in:

• Parkinson's disease: Altered Kir function in models
• ALS: Dysregulated K+ handling
• Peripheral neuropathy: Channelopathies

Therapeutic Targeting

Channel Modulators

• Kir channel blockers: Verapamil, chloroquine
• Kir channel activators: ML133, PAM-2
• Racemic bupivacaine: Enantiomer-selective block

Gene Therapy

• AAV-delivered wild-type KCNJ12
• CRISPR-based gene correction
• siRNA for dominant mutations

Key Publications

Bortolotto ZA et al. (2016). "Kir2.2 channels in [neurons](/entities/neurons)." J Neurosci. PMID: 26843638(https://pubmed.ncbi.nlm.nih.gov/26843638/)

Hibino H et al. (2010). "Inwardly rectifying potassium channels." Physiol Rev. PMID: 20923739(https://pubmed.ncbi.nlm.nih.gov/20923739/)

Kelley M et al. (2020). "KCNJ12 in neurodevelopment." Brain. PMID: 32588854(https://pubmed.ncbi.nlm.nih.gov/32588854/)

Therapeutic Targeting

Kir2.2 channels can be modulated:

Pharmacological Modulators

| Drug/Compound | Effect | Status |
|---------------|--------|--------|
| ML133 | Blocker | Research |
| Papaverine | Opener | Research |
| Zuclopenthixol | Blocker | Research |
| VU590 | Blocker | Research |

Clinical Relevance

• No direct Kir2.2-targeted drugs approved
• General anesthetics affect Kir channels
• Antiarrhythmic potential

Research Directions

Current Studies

• Understanding Kir channel trafficking
• Structure-function studies
• Role in neurodevelopment
• Therapeutic modulation strategies

Model Systems

• Knockout mice
• Zebrafish models
• Xenopus oocytes for electrophysiology
• iPSC-derived neurons

Protein Interactions

Kir2.2 interacts with regulatory proteins:

| Partner | Interaction | Function |
|---------|-------------|----------|
| Kir2.1 (KCNJ2) | Heterotetramer | Channel assembly |
| Kir2.3 (KCNJ4) | Heterotetramer | Tissue-specific function |
| PIP2 | Lipid binding | Channel activation |
| G-proteins | Modulation | Signal transduction |
| PDZ domain proteins | Scaffolding | Localization |

Background

The study of Kir2.2 Potassium Channel 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

[@john]: John SA, et

See Also

• KCNJ12 Gene - Gene Page
• Potassium Channels - Protein Family
• Ion Channels - Related
• Epilepsy - Related Disease

External L

• [UniProt: P48745](https://www.uniprot.org/uniprot/P48745)
• [RCSB PDB: 3JYC](https://www.rcsb.org/structure/3JYC)
• [IUPHAR: Kir2.x](https://www.guidetopharmacology.org/GRAC/FamilyDisplayForward?familyId=82)

NeuroWiki - Protein Page | Last Updated: 2026-03-04