CACNG4
<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">CACNG4 - TARP Gamma-4 Calcium Channel Subunit</th>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>CACNG4</td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Calcium Voltage-Gated Channel Auxiliary Subunit Gamma 4</td>
</tr>
<tr>
<td class="label">Chromosome</td>
<td>17q24.2</td>
</tr>
<tr>
<td class="label">HGNC ID</td>
<td>HGNC:1404</td>
</tr>
<tr>
<td class="label">Ensembl ID</td>
<td>ENSG00000154042</td>
</tr>
<tr>
<td class="label">RefSeq</td>
<td>NM_020321</td>
</tr>
<tr>
<td class="label">UniProt</td>
<td>Q9Y6A2</td>
</tr>
<tr>
<td class="label">Aliases</td>
<td>TARP γ4</td>
</tr>
<tr>
<td class="label">Approach</td>
<td>Status</td>
</tr>
<tr>
<td class="label">TARP γ4-Selective Modulators</td>
<td>Research</td>
</tr>
<tr>
<td class="label">AMPA Receptor Potentiators</td>
<td>Phase 2/3</td>
</tr>
<tr>
<td class="label">Calcium Channel Blockers</td>
<td>Approved</td>
</tr>
<tr>
<td class="label">Gene Therapy</td>
<td>Experimental</td>
</tr>
<tr>
<td class="label">Variant</td>
<td>Type</td>
</tr>
<tr>
<td class="label">rs124</td>
<td>SNP</td>
</tr>
<tr>
<td class="label">rs3818622</td>
<td>SNP</td>
</tr>
<tr>
<td class="label">rs2078267</td>
<td>SNP</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>
Overview
CACNG4 (Calcium Voltage-Gated Channel Auxiliary Subunit Gamma 4), also known as TARP γ4 (Transmembrane AMPA Receptor Regulatory Protein gamma-4), is a human gene whose product encodes the TARP γ4 protein, a member of the transmembrane AMPA receptor regulatory proteins (TARPs) family[@tarp2012]. TARP γ4 is primarily expressed in the brain and functions as an auxiliary subunit of both voltage-gated calcium channels and AMPA receptors[@tarps2010].
TARP γ4 plays important roles in synaptic transmission, neuronal excitability, and has been implicated in epilepsy, autism spectrum disorder (ASD), and Alzheimer's disease (AD)[@cacng2012][@tarp2014a][@calcium2014]. Unlike other TARP isoforms, TARP γ4 shows distinct expression patterns and pharmacological properties that make it a unique therapeutic target[@milstein2015].
Molecular Function
CACNG4 encodes the TARP γ4 protein, which serves multiple critical functions in the nervous system:
Voltage-Gated Calcium Channel Modulation
TARP γ4 modulates the kinetic properties of P/Q-type (Cav2.1) and L-type (Cav1.2) voltage-gated calcium channels. It increases channel open probability and alters voltage-dependent activation/inactivation kinetics[@heck2014]. This modulation affects:
- Calcium influx during action potentials
- Neurotransmitter release at presynaptic terminals
- Gene expression through calcium-dependent signaling pathways
AMPA Receptor Trafficking and Gating
As with other TARPs, TARP γ4 regulates AMPA receptor trafficking and gating at synaptic membranes. It binds to AMPA receptor subunits (GluA1-4) through its C-terminal PDZ-binding domain and facilitates:
- Proper receptor localization to synaptic sites
- Stabilization of receptors at the postsynaptic density
- Modulation of channel gating properties[@tarps2010]
Neuronal Excitability and Synaptic Plasticity
TARP γ4 plays a crucial role in controlling neuronal excitability and synaptic plasticity. It contributes to both LTP and LTD through its regulation of AMPA receptor trafficking[@kim2007]. The protein is involved in:
- Learning and memory processes
- Activity-dependent synaptic modifications
- Homeostatic plasticity responses
Structure
TARP γ4 is a 329-amino acid protein with a characteristic topology similar to other TARP family members:
- N-terminal extracellular domain: Contains glycosylation sites important for protein folding
- Four transmembrane domains: Form the channel-like structure
- C-terminal cytoplasmic tail: Contains the PDZ-binding domain (X-S/T-X-Φ motif) for interaction with PSD-95 and other PDZ proteins
The C-terminal PDZ-binding motif is critical for anchoring the protein at synapses and coupling to AMPA receptor subunits.
Expression Pattern
TARP γ4 shows distinct expression patterns compared to other TARP isoforms, with highest expression in cortical and hippocampal neurons[@expression2005]:
- Cerebral cortex (layer 2-6 pyramidal neurons)
- Hippocampus (CA1-CA3 pyramidal cells, dentate gyrus granule cells)
- Basal ganglia (striatal medium spiny neurons)
- Cerebellum (Purkinje cells)
- Thalamus (relay neurons)
This distribution suggests a role in cortical processing and hippocampal-dependent learning and memory.
Disease Associations
Epilepsy
CACNG4 mutations have been associated with idiopathic generalized epilepsy. The protein's role in regulating neuronal excitability through calcium channel modulation makes it a candidate for seizure susceptibility[@cacng2012]. Studies have identified:
- CACNG4 variants in families with epilepsy
- Altered TARP γ4 function in seizure models
- Interactions with other epilepsy-associated proteins
Autism Spectrum Disorder
Altered CACNG4 expression has been reported in ASD brains. TARP γ4 modulates glutamatergic signaling, which is dysregulated in autism. Genetic studies have identified CACNG4 variants in autism susceptibility screens[@tarp2014a][@zuber2005].
Alzheimer's Disease
TARP γ4 may modulate amyloid-β effects on synaptic function. The protein's role in calcium homeostasis and synaptic plasticity is relevant to AD pathogenesis[@calcium2014]. Changes in TARP γ4 expression have been observed in:
- AD brain tissue
- Amyloid transgenic mouse models
- In vitro Aβ toxicity studies
Other Neurological Conditions
- Migraine: CACNG4 variants may influence cortical excitability
- Bipolar disorder: Some studies suggest altered TARP function
- Schizophrenia: Genetic association studies have identified links
Therapeutic Implications
TARP γ4-selective modulators may have therapeutic potential for neurological disorders[@tarptargeted2015][@catterall2013]:
Common Variants
See Also
- [Calcium Channels](/therapeutics/calcium-channel-blockers)
- [AMPA Receptors](/entities/ampa-receptors)
- [Synaptic Transmission](/mechanisms/synaptic-transmission)
- [Synaptic Plasticity](/mechanisms/synaptic-plasticity)
- [Epilepsy](/diseases/epilepsy)
- [Alzheimer's Disease](/diseases/alzheimers-disease)
- [Autism Spectrum Disorder](/diseases/autism-spectrum-disorder)
External Links
- [NCBI Gene: CACNG4](https://www.ncbi.nlm.nih.gov/gene/27069)
- [UniProt: Q9Y6A2](https://www.uniprot.org/uniprot/Q9Y6A2)
- [GeneCards: CACNG4](https://www.genecards.org/cgi-bin/carddisp.pl?gene=CACNG4)
- [OMIM: 605207](https://www.omim.org/entry/605207)