KCNMB4

KCNMB4

Gene Overview

<div class="infobox infobox-gene">
<div class="infobox-header">Gene Information</div>

<table>
<tr><th>Symbol</th><td>KCNMB4</td></tr>
<tr><th>Full Name</th><td>Potassium Calcium-Activated Channel Subunit Beta 4</td></tr>
<tr><th>Chromosome</th><td>12q14.1</td></tr>
<tr><th>NCBI Gene ID</th><td>[27344](https://www.ncbi.nlm.nih.gov/gene/27344)</td></tr>
<tr><th>UniProt ID</th><td>[Q9UNX9](https://www.uniprot.org/uniprot/Q9UNX9)</td></tr>
<tr><th>Ensembl ID</th><td>[ENSG00000135677](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000135677)</td></tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>
</div>

Overview

KCNMB4 (Potassium Calcium-Activated Channel Subunit Beta 4) encodes the beta4 auxiliary subunit of large-conductance calcium-activated potassium (BK) channels. BK channels are voltage-gated potassium channels with extraordinary conductance (~300 pS) that play crucial roles in regulating neuronal excitability, neurotransmitter release, and smooth muscle tone [@knaus1994][@orio2002]. The beta4 subunit modifies the biophysical properties of BK channels and targets them to specific cellular compartments, with particular importance in [neurons](/entities/neurons) of the central and peripheral nervous systems [@latorre2006].

Function

KCNMB4 encodes a 210-amino acid auxiliary subunit that modulates BK channel (encoded by KCNMA1) function:

Beta Subunit Structure

KCNMB4

Gene Overview

<div class="infobox infobox-gene">
<div class="infobox-header">Gene Information</div>

<table>
<tr><th>Symbol</th><td>KCNMB4</td></tr>
<tr><th>Full Name</th><td>Potassium Calcium-Activated Channel Subunit Beta 4</td></tr>
<tr><th>Chromosome</th><td>12q14.1</td></tr>
<tr><th>NCBI Gene ID</th><td>[27344](https://www.ncbi.nlm.nih.gov/gene/27344)</td></tr>
<tr><th>UniProt ID</th><td>[Q9UNX9](https://www.uniprot.org/uniprot/Q9UNX9)</td></tr>
<tr><th>Ensembl ID</th><td>[ENSG00000135677](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000135677)</td></tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>
</div>

Overview

KCNMB4 (Potassium Calcium-Activated Channel Subunit Beta 4) encodes the beta4 auxiliary subunit of large-conductance calcium-activated potassium (BK) channels. BK channels are voltage-gated potassium channels with extraordinary conductance (~300 pS) that play crucial roles in regulating neuronal excitability, neurotransmitter release, and smooth muscle tone [@knaus1994][@orio2002]. The beta4 subunit modifies the biophysical properties of BK channels and targets them to specific cellular compartments, with particular importance in [neurons](/entities/neurons) of the central and peripheral nervous systems [@latorre2006].

Function

KCNMB4 encodes a 210-amino acid auxiliary subunit that modulates BK channel (encoded by KCNMA1) function:

Beta Subunit Structure

• N-terminal Extracellular Domain: Mediates interactions with the extracellular matrix and other proteins [@jaffe2011].
• Transmembrane Segment: Single transmembrane helix anchoring the subunit to the membrane.
• C-terminal Intracellular Domain: Interacts with the cytoplasmic domain of the BK alpha-subunit to modulate gating [@jaffe2011].

Modulation of BK Channel Properties

• Gating Kinetics: beta4 subunits accelerate activation and slow deactivation of BK channels [@wang2019].
• Calcium Sensitivity: Modifies the calcium sensitivity of the channel, shifting the activation curve [@wang2019].
• Voltage Dependence: Alters voltage dependence of activation [@latorre2006].
• Pharmacology: Changes sensitivity to BK channel modulators including paxilline and iberiotoxin [@latorre2006].

Cellular and Physiological Functions

• Neuronal Excitability: Regulates neuronal firing patterns, particularly in hippocampal and cortical neurons [@brenner2000].
• Neurotransmitter Release: Controls calcium entry through voltage-gated calcium channels at presynaptic terminals, affecting neurotransmitter release [@shao2007].
• Smooth Muscle Function: Modulates BK channels in vascular smooth muscle, affecting blood flow to the brain [@raffaelli2004].
• Hair Cell Function: Essential for normal hearing in the inner ear through effects on auditory hair cells [@brenner2005].

Disease Associations

Alzheimer's Disease

KCNMB4 and BK channels have several connections to Alzheimer's disease:

• Neuronal Hyperexcitability: AD is associated with network hyperexcitability. BK channel function, modulated by beta4, regulates neuronal excitability, and alterations may contribute to seizure activity observed in some AD patients [@riazanski2011].
• Calcium Dysregulation: BK channels are calcium-activated, and the calcium dysregulation characteristic of AD may affect their function. beta4 subunit alterations could exacerbate this [@palop2010].
• Synaptic Dysfunction: BK channels at synapses regulate neurotransmitter release. Altered BK channel function may contribute to synaptic deficits in AD [@shao2007].
• Vascular Function: beta4-containing BK channels in cerebral vasculature may affect cerebral blood flow in AD [@raffaelli2004].

Parkinson's Disease

• Dopaminergic Neuron Function: BK channels regulate the firing patterns of dopaminergic neurons in the substantia nigra. The beta4 subunit influences these properties [@berridge2010].
• Mitochondrial Function: BK channels can localize to mitochondria (mitoBK channels) and affect neuronal survival. beta4 subunit composition may influence this protective function [@watson2012].
• Oxidative Stress: BK channel modulators have shown protective effects in PD models, though beta4-specific roles are not well characterized [@orourke2010].

Epilepsy

• Seizure Susceptibility: Given its role in neuronal excitability, KCNMB4 variations have been investigated in epilepsy. The beta4 subunit's effects on neuronal firing could influence seizure thresholds [@zhang2012].

Stroke and Cerebrovascular Disease

• Cerebral Blood Flow: BK channels in cerebral arterioles regulate vascular tone. The beta4 subunit modulates these responses to affect cerebral blood flow [@raffaelli2004].
• Ischemic Protection: BK channel activation can be protective in ischemic conditions, with beta4 subunit composition influencing these effects [@ngouemo2014].

Hearing Loss

• Auditory Function: KCNMB4 is highly expressed in inner ear hair cells. Mutations or variations can cause hearing loss, making it a gene of interest for auditory neuropathy [@brenner2005].

Expression

Brain Expression

• Regional Distribution: Expressed throughout the brain with high levels in the [hippocampus](/brain-regions/hippocampus) (CA1-CA3, dentate gyrus), cerebral [cortex](/brain-regions/cortex), cerebellum (particularly Purkinje cells), and brainstem nuclei [@kaur2011].
• Cellular Localization: Neuronal expression, with both somatic and dendritic localization. Also detected in some glial cells [@kaur2011].
• Synaptic Localization: Presynaptic terminals where it regulates neurotransmitter release [@shao2007].

Peripheral Expression

• Inner Ear: High expression in hair cells of the cochlea and vestibular system [@brenner2005].
• Cardiovascular System: Expressed in vascular smooth muscle cells, particularly in cerebral arteries [@raffaelli2004].
• Other Tissues: Lower expression in testis, pancreas, and skeletal muscle.

Key Publications

See Also

• BK Potassium Channels
• Ion Channel Dysfunction in Neurodegeneration
• [Neuronal Excitability](/mechanisms/neuronal-hyperexcitability)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)
• [Epilepsy](/diseases/epilepsy)
• Stroke and Cerebrovascular Disease

External Links

• [NCBI Gene: KCNMB4](https://www.ncbi.nlm.nih.gov/gene/27344)
• [UniProt: Q9UNX9](https://www.uniprot.org/uniprot/Q9UNX9)
• [Ensembl: ENSG00000135677](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000135677)
• [PubMed: KCNMB4](https://pubmed.ncbi.nlm.nih.gov/?term=KCNMB4)
• [IUPHAR/BPS Guide to Pharmacology: BK channel beta4](https://www.guidetopharmacology.org/)

References