Complexin-3 (CPLX3) is a neuronal soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE)-binding protein that plays a critical role in regulating neurotransmitter release at synapses. Unlike its widely studied relatives complexin-1 and complexin-2, CPLX3 exhibits a more restricted expression pattern, being primarily enriched in sensory [neurons](/entities/neurons) including photoreceptors and bipolar cells of the [retina](/brain-regions/retina), as well as specific populations of [GABAergic interneurons](/cell-types/gabaergic-interneurons) in the brain. CPLX3 regulates the transition from synaptic vesicle priming to fusion by competitively binding to SNARE complexes with [synaptotagmin-1](/proteins/synaptotagmin-1). [@dmitriev2023]
Complexin-3 (CPLX3) is a neuronal soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE)-binding protein that plays a critical role in regulating neurotransmitter release at synapses. Unlike its widely studied relatives complexin-1 and complexin-2, CPLX3 exhibits a more restricted expression pattern, being primarily enriched in sensory [neurons](/entities/neurons) including photoreceptors and bipolar cells of the [retina](/brain-regions/retina), as well as specific populations of [GABAergic interneurons](/cell-types/gabaergic-interneurons) in the brain. CPLX3 regulates the transition from synaptic vesicle priming to fusion by competitively binding to SNARE complexes with [synaptotagmin-1](/proteins/synaptotagmin-1). [@dmitriev2023]
<div class="infobox infobox-protein"> [@liu2022]
<table> [@brose2020]
<tr><th colspan="2" style="background:#4a90d9; color:white; text-align:center">CPLX3 — Complexin-3</th></tr> [@rhee2019]
<tr><td><b>Protein Name</b></td><td>Complexin-3</td></tr> [@reim2018]
<tr><td><b>Gene Symbol</b></td><td>[CPLX3](/genes/cplx3)</td></tr> [@mccarthy2017]
<tr><td><b>UniProt ID</b></td><td><a href="https://www.uniprot.org/uniprot/Q9BQY1" target="_blank">Q9BQY1</a></td></tr> [@kochubey2016]
<tr><td><b>PDB Structure</b></td><td><a href="https://www.rcsb.org/structure/6CP6" target="_blank">6CP6</a></td></tr> [@trimbuch2015]
<tr><td><b>Molecular Weight</b></td><td>15.5 kDa</td></tr>
<tr><td><b>Subcellular Localization</b></td><td>Cytosol, Synaptic vesicles, Presynaptic terminal</td></tr>
<tr><td><b>Protein Family</b></td><td>Complexin family</td></tr>
<tr><td><b>Brain Expression</b></td><td>Retina, Sensory ganglia, Hippocampus, Cerebral cortex</td></tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">7 edges</a></td>
</tr>
</table>
</div>
Complexin-3 is one of four complexin proteins in mammals (CPLX1-4) that function as molecular clamps regulating SNARE-mediated membrane fusion. While CPLX1 and CPLX2 are broadly expressed throughout the nervous system and regulate both excitatory and inhibitory synapses, CPLX3 has a more specialized distribution. It is particularly enriched in sensory systems, where it plays unique roles in [synaptic transmission](/mechanisms/synaptic-transmission) and [phototransduction](/mechanisms/phototransduction).
The CPLX3 protein contains several functional domains:
CPLX3 plays several essential roles in neuronal function:
Dysfunction of CPLX3 contributes to several neurodegenerative diseases:
In [Alzheimer's disease](/diseases/alzheimers-disease):
In [Parkinson's disease](/diseases/parkinsons-disease):
CPLX3 dysfunction is particularly relevant to retinal diseases:
| Approach | Target | Status | Notes |
|----------|--------|--------|-------|
| Gene therapy | CPLX3 expression | Preclinical | AAV delivery to retina |
| Small molecules | CPLX3-SNARE interaction | Research | Enhance or inhibit binding |
| Peptide inhibitors | N-terminal domain | Research | Block hyperactive CPLX3 |
| Protein replacement | Recombinant CPLX3 | Research | For loss-of-function |
CPLX3 exhibits region-specific expression:
The study of Complexin 3 (Cplx3) has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.