CACNG2 Gene
<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">CACNG2 - Stargazin Calcium Channel Gamma-2</th>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>CACNG2</td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Calcium Voltage-Gated Channel Gamma Subunit 2 (Stargazin)</td>
</tr>
<tr>
<td class="label">Chromosome</td>
<td>22q12.1</td>
</tr>
<tr>
<td class="label">HGNC ID</td>
<td>HGNC:15868</td>
</tr>
<tr>
<td class="label">Ensembl ID</td>
<td>ENSG00000166862</td>
</tr>
<tr>
<td class="label">RefSeq</td>
<td>NM_006031</td>
</tr>
<tr>
<td class="label">UniProt</td>
<td>Q9Y698</td>
</tr>
<tr>
<td class="label">Aliases</td>
<td>STARG2, TARP γ2</td>
</tr>
<tr>
<td class="label">Approach</td>
<td>Status</td>
</tr>
<tr>
<td class="label">AMPA Receptor Modulators</td>
<td>Approved</td>
</tr>
<tr>
<td class="label">PKC Inhibitors</td>
<td>Experimental</td>
</tr>
<tr>
<td class="label">Gene Therapy</td>
<td>Experimental</td>
</tr>
<tr>
<td class="label">TARP-Selective Modulators</td>
<td>Research</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>
Overview
CACNG2 (Calcium Voltage-Gated Channel Gamma Subunit 2), also known as stargazin, encodes the gamma-2 subunit of voltage-gated calcium channels. This subunit is a member of the transmembrane AMPA receptor regulatory proteins (TARPs) family and is critical for AMPA receptor trafficking and synaptic plasticity in addition to its role in calcium channels[@tomita2003][@chen2000].
Stargazin was originally identified as a component of voltage-gated calcium channels, but subsequent research revealed its crucial role as an auxiliary subunit of AMPA receptors. The discovery of the stargazer mouse, which carries a spontaneous mutation in CACNG2 and exhibits ataxia and seizures, highlighted the importance of this gene in neurological disease[@letts1998][@payne2008].
Molecular Function
The CACNG2/stargazin protein serves multiple critical functions in the nervous system:
AMPA Receptor Trafficking and Regulation
Stargazin is essential for the proper trafficking and anchoring of AMPA receptors at synapses. It binds to the cytoplasmic tails of AMPA receptor subunits (GluA1-4) and facilitates their transport to the synaptic membrane. Without stargazin, AMPA receptors fail to cluster properly at postsynaptic densities, leading to impaired synaptic transmission[@menzel2005][@kato2008].
Calcium Channel Modulation
As a member of the voltage-gated calcium channel gamma subunit family, stargazin modulates high-voltage-activated calcium channel function. This modulation affects calcium influx during action potentials and regulates neurotransmitter release at presynaptic terminals[@milstein2007].
Synaptic Plasticity
Stargazin is essential for both long-term potentiation (LTP) and long-term depression (LTD), forms of synaptic plasticity underlying learning and memory. The regulation of AMPA receptor trafficking by stargazin allows for dynamic modulation of synaptic strength in response to activity patterns[@roopra2007][@kim2008].
Phosphorylation Regulation
Stargazin function is regulated by phosphorylation. Phosphorylation at serine residues modulates its interaction with AMPA receptors and its trafficking dynamics. PKC-mediated phosphorylation affects synaptic plasticity and learning[@huang2018].
Structure
Stargazin is a 323-amino acid protein with a characteristic topology:
- N-terminal extracellular domain: Contains glycosylation sites
- Four transmembrane domains: Form the channel-like structure
- C-terminal cytoplasmic tail: Contains the PDZ-binding domain that interacts with AMPA receptor subunits
The C-terminal PDZ-binding motif (X-S/T-X-Φ) is critical for binding to PSD-95 and other PDZ proteins that anchor the complex at synapses.
Disease Associations
Alzheimer's Disease
Stargazin dysfunction affects glutamatergic signaling in AD models. Amyloid-β oligomers can interfere with stargazin-mediated AMPA receptor trafficking, contributing to synaptic plasticity deficits observed in AD. The loss of synaptic AMPA receptors in AD may involve stargazin-related mechanisms[@luthi2011][@nathan2010].
Key connections include:
- Aβ-induced disruption of AMPA receptor trafficking
- Impaired LTP in hippocampal circuits
- Synaptic plasticity deficits involving stargazin phosphorylation
Parkinson's Disease
Altered glutamatergic signaling in basal ganglia circuits is a hallmark of PD. Stargazin contributes to the regulation of AMPA receptors in the striatum and motor [cortex](/brain-regions/cortex), where changes may contribute to motor cortex hyperexcitability and dyskinesias associated with dopaminergic dysfunction.
Epilepsy
CACNG2 mutations cause multiple forms of epileptic encephalopathy. The stargazer mouse (Cacng2stg/stg) carries a nonsense mutation that causes spontaneous seizures, ataxia, and cerebellar dysfunction. These mice exhibit:
- Impaired AMPA receptor trafficking
- Reduced synaptic AMPA receptor density
- Abnormal cerebellar GABAergic signaling[@cho2007]
Human CACNG2 mutations have been linked to:
- Early infantile epileptic encephalopathy (EIEE)
- Generalized epilepsy with absence seizures
- Intractable childhood epilepsy
Autism Spectrum Disorders
Strong genetic associations between CACNG2 variants and ASD have been identified. Studies have found CACNG2 mutations in autism susceptibility gene screens. The mechanism involves synaptic dysfunction due to impaired AMPA receptor trafficking and altered glutamatergic signaling[@swift2006].
Schizophrenia
Genetic variants in CACNG2 have been associated with schizophrenia risk. Altered glutamatergic neurotransmission due to stargazin dysfunction may contribute to the hypoglutamatergic state observed in schizophrenia patients.
Therapeutic Targeting
Animal Models
- Stargazer Mice (Cacng2stg/stg): Spontaneous mutation causing ataxia and seizures
- CACNG2 Knockout Mice: Impaired AMPA receptor trafficking, reduced synaptic responses
- Transgenic Overexpression: Enhanced synaptic plasticity, improved learning
- Conditional Knockouts: Region-specific deletion to study specific circuits
See Also
- [AMPA Receptors](/proteins/ampa-receptors)
- [Synaptic Plasticity](/mechanisms/synaptic-plasticity)
- [Long-Term Potentiation](/mechanisms/long-term-potentiation)
- [Alzheimer's Disease](/diseases/alzheimers-disease)
- [Epilepsy](/diseases/epilepsy)
- [Autism Spectrum Disorder](/diseases/autism-spectrum-disorder)
External Links
- [NCBI Gene: CACNG2](https://www.ncbi.nlm.nih.gov/gene/10368)
- [UniProt: Q9Y698](https://www.uniprot.org/uniprot/Q9Y698)
- [GeneCards: CACNG2](https://www.genecards.org/cgi-bin/carddisp.pl?gene=CACNG2)
- [OMIM: 300491](https://www.omim.org/entry/300491)