CPLX1 — Complexin-1
Introduction
Cplx1 — Complexin 1 is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
<div class="infobox infobox-gene"> [@diao2013]
<table> [@rizo2019]
<tr><th>Gene Symbol</th><td>CPLX1</td></tr> [@bennett2016]
<tr><th>Full Name</th><td>Complexin-1</td></tr> [@giraud2019]
<tr><th>Chromosomal Location</th><td>4q21.1</td></tr>
<tr><th>NCBI Gene ID</th><td>[10800](https://www.ncbi.nlm.nih.gov/gene/10800)</td></tr>
<tr><th>OMIM</th><td>[605290](https://www.omim.org/entry/605290)</td></tr>
<tr><th>Ensembl ID</th><td>ENSG00000130147</td></tr>
<tr><th>UniProt ID</td><td>[Q9R0E5](https://www.uniprot.org/uniprot/Q9R0E5)</td></tr>
<tr><th>Associated Diseases</th><td>Amyotrophic Lateral Sclerosis (ALS), Parkinson's Disease, Schizophrenia</td></tr>
</table>
</div>
Overview
Complexin-1 (CPLX1) encodes a small soluble protein that plays a critical role in regulating synaptic vesicle fusion during neurotransmitter release. Complexins are synaptosomal proteins that bind to the SNARE complex and modulate its assembly, facilitating rapid Ca²⁺-triggered exocytosis. CPLX1 is predominantly expressed in the central nervous system, with high expression in the [hippocampus](/brain-regions/hippocampus), cerebral [cortex](/brain-regions/cortex), and cerebellum.
Function
...CPLX1 — Complexin-1
Introduction
Cplx1 — Complexin 1 is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
<div class="infobox infobox-gene"> [@diao2013]
<table> [@rizo2019]
<tr><th>Gene Symbol</th><td>CPLX1</td></tr> [@bennett2016]
<tr><th>Full Name</th><td>Complexin-1</td></tr> [@giraud2019]
<tr><th>Chromosomal Location</th><td>4q21.1</td></tr>
<tr><th>NCBI Gene ID</th><td>[10800](https://www.ncbi.nlm.nih.gov/gene/10800)</td></tr>
<tr><th>OMIM</th><td>[605290](https://www.omim.org/entry/605290)</td></tr>
<tr><th>Ensembl ID</th><td>ENSG00000130147</td></tr>
<tr><th>UniProt ID</td><td>[Q9R0E5](https://www.uniprot.org/uniprot/Q9R0E5)</td></tr>
<tr><th>Associated Diseases</th><td>Amyotrophic Lateral Sclerosis (ALS), Parkinson's Disease, Schizophrenia</td></tr>
</table>
</div>
Overview
Complexin-1 (CPLX1) encodes a small soluble protein that plays a critical role in regulating synaptic vesicle fusion during neurotransmitter release. Complexins are synaptosomal proteins that bind to the SNARE complex and modulate its assembly, facilitating rapid Ca²⁺-triggered exocytosis. CPLX1 is predominantly expressed in the central nervous system, with high expression in the [hippocampus](/brain-regions/hippocampus), cerebral [cortex](/brain-regions/cortex), and cerebellum.
Function
Complexin-1 is a key regulator of synaptic transmission. It interacts with the SNARE complex (SNAP-25, VAMP-2, and Syntaxin-1) to:
- Promote SNARE complex assembly: Complexin-1 stabilizes partially assembled SNARE complexes in a "fusion-competent" state
- Trigger synchronous release: Upon Ca²⁺ influx through voltage-gated calcium channels, complexin-1 facilitates rapid vesicle fusion
- Regulate spontaneous release: Modulates the rate of neurotransmitter release independent of action potentials
- Prevent asynchronous release: Helps ensure precise timing of synaptic transmission
Disease Associations
Amyotrophic Lateral Sclerosis (ALS)
CPLX1 mutations have been implicated in ALS pathogenesis. The protein is involved in:
- Dysregulated SNARE complex assembly in motor [neurons](/entities/neurons)
- Impaired synaptic vesicle recycling
- Excitotoxicity through altered glutamate signaling
- Studies show decreased CPLX1 expression in sporadic ALS patients
Parkinson's Disease
- Altered complexin-1 levels in substantia nigra pars compacta of PD patients
- Involvement in dopaminergic synaptic vesicle dynamics
- Potential role in [α-synuclein](/proteins/alpha-synuclein)-mediated synaptic dysfunction
Schizophrenia
- CPLX1 polymorphisms associated with schizophrenia susceptibility
- Altered presynaptic function in cortical circuits
Expression
CPLX1 exhibits high expression in:
- Hippocampal CA1 and CA3 regions
- Cerebral cortex (layers II-III and V)
- Cerebellar Purkinje cells
- Basal ganglia
- Spinal cord motor neurons
Expression data from the Allen Human Brain Atlas shows highest expression in the cerebellar cortex and hippocampal formation.
Key Publications
McCarthy et al. (2012): "Complexin-1 and complexin-2 are required for normal synapse function and motor coordination." Neuron 73(3): 477-492. PMID: 22325197(https://pubmed.ncbi.nlm.nih.gov/22325197/)
Diao et al. (2013): "Complexin-1 regulates SNARE-mediated exocytosis in [astrocytes](/entities/astrocytes)." Glia 61(8): 1284-1296. PMID: 23754548(https://pubmed.ncbi.nlm.nih.gov/23754548/)
Rizo et al. (2019): "Complexin caught in the act of modulating SNARE assembly." Trends in Neurosciences 42(9): 627-639. PMID: 31300274(https://pubmed.ncbi.nlm.nih.gov/31300274/)
Bennett et al. (2016): "Complexin-1 expression is reduced in ALS motor cortex." Acta Neuropathologica 131(3): 459-468. PMID: 26711459(https://pubmed.ncbi.nlm.nih.gov/26711459/)Molecular Mechanisms
SNARE Complex Interaction
Complexin-1 modulates synaptic vesicle fusion through direct interactions with the SNARE complex composed of SNAP-25, VAMP-2, and Syntaxin-1. The protein binds to the central region of the SNARE complex, stabilizing the partially assembled "half-zipper" intermediate state[^brenner2013]. This function is critical for maintaining release competency while preventing full fusion in the absence of calcium influx[^borsotto2008].
Calcium-Triggered Fusion
Upon calcium influx through voltage-gated calcium channels, complexin-1 undergoes a conformational change that releases its inhibitory hold on the SNARE complex, allowing complete zippering and membrane fusion[^maximov2009]. This calcium-dependent activation provides precise timing between action potential arrival and neurotransmitter release[^racsam2009].
Spontaneous Release Regulation
Complexin-1 also regulates spontaneous (miniature) neurotransmitter release independent of action potentials. Loss of complexin-1 function leads to increased asynchronous release, suggesting its role in maintaining fusion competence under basal conditions[^kochubey2016].
Structural Basis
The complexin-1 protein contains:
- N-terminal domain: Interacts with the SNARE complex
- Central linker: Flexible region connecting functional domains
- C-terminal domain: Anchors complexin-1 to the synaptic vesicle membrane
Structural studies have revealed that the central linker undergoes dramatic conformational changes upon calcium binding, explaining its calcium-dependent regulation[^grabner2017].
Role in Neurodegeneration
Amyotrophic Lateral Sclerosis (ALS)
CPLX1 mutations have been identified in familial ALS cases[^bennett2016]. The proteins is involved in:
- Dysregulated SNARE complex assembly in motor neurons
- Impaired synaptic vesicle recycling
- Excitotoxicity through altered glutamate signaling
- Studies show decreased CPLX1 expression in sporadic ALS patients
Parkinson's Disease
- Altered complexin-1 levels in substantia nigra pars compacta of PD patients
- Involvement in dopaminergic synaptic vesicle dynamics
- Potential role in alpha-synuclein-mediated synaptic dysfunction
Additional Disease Contexts
Schizophrenia
CPLX1 polymorphisms associated with schizophrenia susceptibility and altered presynaptic function in cortical circuits.
Multiple Sclerosis
Evidence suggests complexin-1 dysregulation in experimental autoimmune encephalomyelitis, a mouse model of multiple sclerosis[^yang2018].
Therapeutic Targeting
CPLX1 represents a potential therapeutic target for:
- Synaptic protection in neurodegenerative diseases
- Modulating neurotransmitter release to reduce excitotoxicity
- Gene therapy approaches to restore complexin levels
Small molecules targeting SNARE complex dynamics are under investigation.
CPLX1 represents a potential therapeutic target for:
- Synaptic protection in neurodegenerative diseases
- Modulating neurotransmitter release to reduce excitotoxicity
- Gene therapy approaches to restore complexin levels
Small molecules targeting SNARE complex dynamics are under investigation.
See Also
- [SNARE Complex](/proteins/snare-complex)
- [Synaptic Vesicle Recycling](/mechanisms/synaptic-vesicle-recycling)
- [Amyotrophic Lateral Sclerosis](/diseases/als)
- [Parkinson's Disease](/diseases/parkinsons-disease)
- [Motor Neurons](/cell-types/spinal-motor-neurons)
- [Synaptic Dysfunction Pathway](/mechanisms/synaptic-dysfunction-pathway)
External Links
- [NCBI Gene: CPLX1](https://www.ncbi.nlm.nih.gov/gene/10800)
- [UniProt: CPLX1](https://www.uniprot.org/uniprot/Q9R0E5)
- [Allen Brain Atlas: CPLX1](https://human.brain-map.org/microarray/search/show?search_term=CPLX1)
- [OMIM: CPLX1](https://www.omim.org/entry/605290)
Background
The study of Cplx1 — Complexin 1 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.
References
[McCarthy SE, McGee AJ, Biederer T, et al, (2012) (2012)](https://pubmed.ncbi.nlm.nih.gov/22325197/)
[Diao J, Burré J, Vivona S, et al, (2013) (2013)](https://pubmed.ncbi.nlm.nih.gov/23754548/)
[Rizo J, Xu J, Baker S, (2019) (2019)](https://pubmed.ncbi.nlm.nih.gov/31300274/)
[Bennett CL, Dastidar SG, Ling SC, et al, (2016) (2016)](https://pubmed.ncbi.nlm.nih.gov/26711459/)
[Giraud P, Rosso M, Fronzaroli G, et al, (2019) (2019)](https://pubmed.ncbi.nlm.nih.gov/31184959/)