KCNN4 — Potassium Calcium-Activated Channel Subfamily N Member 4

KCNN4 — Potassium Calcium-Activated Channel Subfamily N Member 4

Overview

KCNN4 — Potassium Calcium-Activated Channel Subfamily N Member 4

Overview

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">KCNN4 — Potassium Calcium-Activated Channel Subfamily N Member 4</th>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>KCNN4</td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Potassium Calcium-Activated Channel Subfamily N Member 4</td>
</tr>
<tr>
<td class="label">Aliases</td>
<td>SK4, IK1, KCa3.1</td>
</tr>
<tr>
<td class="label">Chromosome</td>
<td>19q13.2</td>
</tr>
<tr>
<td class="label">NCBI Gene ID</td>
<td>[3782](https://www.ncbi.nlm.nih.gov/gene/3782)</td>
</tr>
<tr>
<td class="label">Ensembl ID</td>
<td>[ENSG00000104970](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000104970)</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>[Q9UQM4](https://www.uniprot.org/uniprot/Q9UQM4)</td>
</tr>
<tr>
<td class="label">OMIM</td>
<td>604270</td>
</tr>
<tr>
<td class="label">Protein Type</td>
<td>Ion channel (intermediate-conductance Ca2+-activated K+)</td>
</tr>
<tr>
<td class="label">Expression</td>
<td>Erythrocytes, immune cells, brain (glia), salivary glands</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td>Multiple sclerosis, neuroinflammation, immune disorders</td>
</tr>
<tr>
<td class="label">Pathway</td>
<td>Interaction</td>
</tr>
<tr>
<td class="label">T cell receptor</td>
<td>Essential for activation</td>
</tr>
<tr>
<td class="label">Calcium signaling</td>
<td>Modulates Ca2+ influx</td>
</tr>
<tr>
<td class="label">Cytokine production</td>
<td>Regulates release</td>
</tr>
<tr>
<td class="label">Cell volume</td>
<td>Controls flux</td>
</tr>
<tr>
<td class="label">Approach</td>
<td>Development Stage</td>
</tr>
<tr>
<td class="label">TRAM-34</td>
<td>Preclinical</td>
</tr>
<tr>
<td class="label">Senicapoc</td>
<td>Clinical (sickle cell)</td>
</tr>
<tr>
<td class="label">KCNN4 activators</td>
<td>Research</td>
</tr>
<tr>
<td class="label">Gene therapy</td>
<td>Early research</td>
</tr>
<tr>
<td class="label">Component</td>
<td>Interaction</td>
</tr>
<tr>
<td class="label">Calmodulin</td>
<td>Direct binding</td>
</tr>
<tr>
<td class="label">T cell receptor</td>
<td>Essential</td>
</tr>
<tr>
<td class="label">Cytokine pathways</td>
<td>Modulates</td>
</tr>
<tr>
<td class="label">Calcium channels</td>
<td>Electrical coupling</td>
</tr>
</table>

KCNN4 (Potassium Calcium-Activated Channel Subfamily N Member 4), also known as SK4 or IK1 (Intermediate-Conductance Calcium-Activated Potassium Channel 4), is an intermediate-conductance calcium-activated potassium channel that plays critical roles in immune cell activation, erythrocyte volume regulation, epithelial secretion, and neuroinflammation. Originally identified in erythrocytes and immune cells, KCNN4 has emerged as an important player in neurodegenerative diseases through its functions in microglia, astrocytes, and peripheral immune cells that communicate with the central nervous system["@stocker2004"].

KCNN4 belongs to the KCNN family (also known as SK/IK family) of calcium-activated potassium channels. Unlike the small-conductance KCNN1-3 channels, KCNN4 exhibits intermediate conductance (~20-80 pS), placing it between the small and large conductance channels. This unique property, along with its expression pattern in non-neuronal cells, makes KCNN4 a distinct therapeutic target for modulating immune function and neuroinflammation in neurodegenerative diseases["@shah2018"].

Gene Structure and Protein Architecture

Channel Topology

KCNN4 shares the typical six-transmembrane domain structure:

• S1-S4: Voltage sensor-like domain (non-voltage sensing)
• S5-S6: Pore-forming region with K⁺ selectivity filter
• N-terminus: Cytoplasmic, contains regulatory sequences
• C-terminus: Cytoplasmic, contains calmodulin binding domain

Calmodulin Binding

Like other KCNN channels, KCNN4 is regulated by calmodulin[@ishii2018]:

• Calmodulin binding domain: Located in C-terminal region
• Calcium sensitivity: Lower Ca²⁺ sensitivity than SK1-3 channels
• Activation kinetics: Faster activation and deactivation

Assembly

KCNN4 forms functional tetramers:

• Homotetrameric assembly: Four subunits form functional channel
• No known heteromers: Does not form mixed tetramers with other KCNN isoforms
• Tissue-specific regulation: Different regulatory mechanisms in different cell types

Normal Function

Immune Cell Function

KCNN4 is critical for immune cell activation[@mori2021]:

T lymphocytes:

• Required for T cell receptor signaling
• Supports calcium influx during activation
• Necessary for proliferation and cytokine production

• Modulates B cell receptor signaling
• Affects antibody production

• Regulates cytotoxic granule release
• Important for killing target cells

• Controls antigen presentation
• Modulates migration

Erythrocyte Function

KCNN4 regulates erythrocyte volume and hydration[@huang2020]:

• Gardos channel: KCNN4 is also known as the Gardos channel
• Volume regulation: Activates during cell swelling to drive K⁺ and water loss
• Sickle cell disease: Involved in sickling of red blood cells

Epithelial Secretion

In salivary glands and other epithelia:

• Salivary secretion: Controls Cl⁻ secretion through basolateral K⁺ recycling
• Lung epithelial function: Modulates airway surface liquid
• Intestinal secretion: Affects intestinal fluid balance

Glial Function

In the central nervous system[@kaushal2019]:

Microglia:

• KCNN4 expressed in activated microglia
• Regulates microglial activation state
• Modulates cytokine release

• KCNN4 in astrocyte processes
• May affect potassium buffering
• Could modulate astrocyte responses to injury

Role in Neurodegeneration

Neuroinflammation

KCNN4 contributes to neuroinflammatory processes[@weng2017]:

Microglial activation:

• KCNN4 upregulation in activated microglia
• Regulates release of pro-inflammatory cytokines
• Modulates phagocytic activity

• Contributes to chronic neuroinflammation
• May affect disease progression
• Target for anti-inflammatory therapy

• Microglial KCNN4 in dopaminergic neuron loss
• Potential therapeutic target

Multiple Sclerosis and Demyelination

KCNN4 plays a role in demyelinating diseases[@zhang2020]:

T cell involvement:

• KCNN4 in autoreactive T cells
• Contributes to myelin-targeted immune attack
• Blocking reduces disease severity in models

• Affects oligodendrocyte function
• Modulates immune-mediated damage

Neuropathic Pain

KCNN4 contributes to chronic pain states[@yang2019]:

Sensory neurons:

• Upregulated in dorsal root ganglion neurons
• Contributes to hyperexcitability
• Blocking reduces pain behaviors

• KCNN4 in immune cells affects pain pathways
• Cross-talk between immune and nervous system

Stroke and Brain Injury

KCNN4 in post-injury responses:

• Inflammatory response: Modulates post-stroke inflammation
• Microglial activation: Affects recovery
• Therapeutic potential: Blocking may improve outcomes

Molecular Mechanisms

Calcium Gating

KCNN4 is activated by intracellular Ca²⁺:

Signaling Interactions

KCNN4 interacts with multiple pathways:

Electrophysiological Properties

• Conductance: Intermediate (~20-80 pS)
• Voltage dependence: Weakly voltage-dependent
• Calcium sensitivity: Lower than SK1-3
• Pharmacology: Blocked by clotrimazole, TRAM-34

Therapeutic Implications

Targeting Strategies

KCNN4 can be pharmacologically modulated[@chen2022]:

Blockers:

• TRAM-34: Specific KCNN4 blocker
• Clotrimazole: Less specific but effective
• Senicapoc: Clinical trials for sickle cell disease

• Reduce neuroinflammation
• Treat demyelinating diseases
• Manage chronic pain

Drug Development Status

Clinical Considerations

Challenges:

• Peripheral vs central: Targeting CNS vs peripheral immune cells
• Isoform specificity: Similarities with other KCNNs
• Off-target effects: Immune suppression risk
• BBB penetration: For CNS targeting

Research Directions

Current Questions

Emerging Areas

• Brain-penetrant blockers: New compounds for CNS diseases
• Cell-specific targeting: Delivery to specific immune populations
• Repurposing: Existing KCNN4 blockers for neurodegeneration
• Biomarkers: Pathway activity indicators

Animal Models and Research Findings

Knockout Mouse Studies

• Kcnn4 knockout: Viable with immune and erythrocyte phenotypes
• Immune deficits: Impaired T cell activation
• Erythrocyte abnormalities: Altered volume regulation

Disease Model Findings

• MS models: KCNN4 blockers reduce disease severity
• Pain models: Reduces neuropathic pain
• Stroke models: Improves outcomes

Human Studies

• Expression studies: KCNN4 in immune cells from patients
• Genetic studies: Variants in disease risk
• Clinical trials: Senicapoc in various conditions

Interactions and Signaling Network

KCNN4 interacts with multiple components:

See Also

• [KCNN1](/genes/kcnn1) — SK1 channel
• [KCNN2](/genes/kcnn2) — SK2 channel
• [KCNN3](/genes/kcnn3) — SK3 channel
• [Ion Channels in Neurodegeneration](/mechanisms/ion-channels-neurodegeneration)
• [Neuroinflammation](/mechanisms/neuroinflammation)
• [Microglia](/cell-types/microglia)
• [Multiple Sclerosis](/diseases/multiple-sclerosis)
• [Neuropathic Pain](/mechanisms/neuropathic-pain)

External Links

• [NCBI Gene - KCNN4](https://www.ncbi.nlm.nih.gov/gene/3782)
• [UniProt - KCNN4](https://www.uniprot.org/uniprot/Q9UQM4)
• [Ensembl - KCNN4](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000104970)
• [OMIM - KCNN4](https://omim.org/entry/604270)
• [GeneCards - KCNN4](https://www.genecards.org/cgi-bin/carddisp.pl?gene=KCNN4)

References

Pathway Diagram

The following diagram shows the key molecular relationships involving KCNN4 — Potassium Calcium-Activated Channel Subfamily N Member 4 discovered through SciDEX knowledge graph analysis: