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[1]. TARP γ4 is primarily expressed in the brain and functions as an auxiliary subunit of both voltage-gated calcium channels and AMPA receptors[2].
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)[3][4][5]. Unlike other TARP isoforms, TARP γ4 shows distinct expression patterns and pharmacological properties that make it a unique therapeutic target[6].
| Property | Value |
|---|---|
| Gene Symbol | CACNG4 |
| Full Name | Calcium Voltage-Gated Channel Auxiliary Subunit Gamma 4 |
| Chromosome | 17q24.2 |
| HGNC ID | HGNC:1404 |
| Ensembl ID | ENSG00000154042 |
| RefSeq | NM_020321 |
| UniProt | Q9Y6A2 |
| Aliases | TARP γ4 |
CACNG4 encodes the TARP γ4 protein, which serves multiple critical functions in the nervous system:
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[7]. This modulation affects:
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:
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[8]. The protein is involved in:
TARP γ4 is a 329-amino acid protein with a characteristic topology similar to other TARP family members:
The C-terminal PDZ-binding motif is critical for anchoring the protein at synapses and coupling to AMPA receptor subunits.
TARP γ4 shows distinct expression patterns compared to other TARP isoforms, with highest expression in cortical and hippocampal neurons[9]:
This distribution suggests a role in cortical processing and hippocampal-dependent learning and memory.
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[3:1]. Studies have identified:
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[4:1][10].
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[5:1]. Changes in TARP γ4 expression have been observed in:
TARP γ4-selective modulators may have therapeutic potential for neurological disorders[11][12]:
| Approach | Status | Description |
|---|---|---|
| TARP γ4-Selective Modulators | Research | Isoform-specific calcium channel drugs |
| AMPA Receptor Potentiators | Phase 2/3 | Ampakines for cognitive enhancement |
| Calcium Channel Blockers | Approved | L-type blockers for various indications |
| Gene Therapy | Experimental | Restoring normal TARP γ4 function |
| Variant | Type | Association | Notes |
|---|---|---|---|
| rs124 | SNP | Epilepsy risk | Regulatory variant |
| rs3818622 | SNP | ASD susceptibility | In promoter region |
| rs2078267 | SNP | AD risk | Alters expression |
Kim K, et al. TARP function and pharmacology. Molecular Pharmacology. 2012. ↩︎
Nicoll RA, et al. TARPs in synaptic transmission. Journal of Physiology. 2010. ↩︎ ↩︎
Everett J, et al. CACNG4 and epilepsy genetics. Epilepsia. 2012. ↩︎ ↩︎
Liu L, et al. TARP expression in autism brain. Molecular Autism. 2014. ↩︎ ↩︎
Yang J, et al. Calcium channels in Alzheimer's disease. Cell Calcium. 2014. ↩︎ ↩︎
Milstein AD, et al. TARP subtypes and their pharmacological properties. Journal of Molecular Neuroscience. 2015. ↩︎
Heck TD, et al. TARP modulation of calcium channel gating. Journal of General Physiology. 2014. ↩︎
Kim J, et al. TARP γ8 and synaptic plasticity in hippocampus. Nature Neuroscience. 2007. ↩︎
Lee SH, et al. Expression of TARP isoforms in brain. Journal of Comparative Neurology. 2005. ↩︎
Zuber G, et al. TARP association with neurological disease. Brain Research Reviews. 2005. ↩︎
Sharp AH, et al. TARP-targeted drug development. Nature Reviews Drug Discovery. 2015. ↩︎
Catterall WA, et al. Calcium channelopathies of voltage-gated channels. Cold Spring Harbor Perspectives in Biology. 2013. ↩︎