CPLX3 — Complexin-3

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CPLX3 — Complexin-3

Introduction

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">CPLX3 — Complexin-3</th>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>CPLX3</td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Complexin-3</td>
</tr>
<tr>
<td class="label">Chromosomal Location</td>
<td>5q23.1</td>
</tr>
<tr>
<td class="label">NCBI Gene ID</td>
<td>[81571](https://www.ncbi.nlm.nih.gov/gene/81571)</td>
</tr>
<tr>
<td class="label">OMIM</td>
<td>[618251](https://www.omim.org/entry/618251)</td>
</tr>
<tr>
<td class="label">Ensembl ID</td>
<td>ENSG00000177468</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>[Q9BQY1](https://www.uniprot.org/uniprot/Q9BQY1)</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td>AD, epilepsy, intellectual disability, retinal degeneration</td>
</tr>
</table>

...

CPLX3 — Complexin-3

Introduction

CPLX3 (Complexin-3) is a neuronal soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptor (SNARE)-interacting protein that plays critical roles in regulating synaptic vesicle fusion, neurotransmitter release, and synaptic plasticity. As a member of the complexin family (CPLX1-4), CPLX3 has specialized functions in sensory synapses, particularly in the retina and olfactory system, as well as in specific populations of [neurons](/entities/neurons) in the brain. CPLX3 is essential for proper synaptic transmission at ribbon synapses of photoreceptor cells and bipolar cells, and regulates both excitatory and inhibitory synaptic transmission in central nervous system neurons [1][2].

--- [@buhl2013]
title: CPLX3 — Complexin-3 [@rizo2018]

--- [@shalaby2020]

.infobox.infobox-gene [@tan2019]

Overview

Mermaid diagram (expand to render)

Complexin-3 is a neuronal protein that regulates synaptic vesicle fusion by binding to the SNARE complex. It plays a critical role in regulating neurotransmitter release at ribbon synapses and conventional synapses in the retina and brain. CPLX3 is highly expressed in photoreceptor cells, bipolar cells, and various brain regions including the hippocampus and [cortex](/brain-regions/cortex). Mutations or dysregulation of CPLX3 have been implicated in retinal degeneration, epilepsy, and neurodevelopmental disorders.

Protein Structure

The CPLX3 protein (approximately 156 amino acids) contains several key structural features:

N-Terminal Domain

The N-terminal region contains the central α-helical domain that binds to assembled SNARE complexes. This domain:

Binds to the ternary SNARE complex (syntaxin-1, SNAP-25, VAMP2)
Stabilizes the pre-fusion SNARE complex
Regulates the transition from priming to release-ready states

Central Region

The central linker region contains:

Accessory α-helical domain (AHA)
Membrane-binding region
Phosphorylation sites for regulatory control

C-Terminal Domain

The C-terminus contains:

Hydrophobic membrane-anchoring segment
Palmitoylation site for synaptic membrane association
Protein-protein interaction motifs

Molecular Function

SNARE Complex Regulation

CPLX3 regulates neurotransmitter release through direct interaction with the SNARE complex:

Priming Function

CPLX3 stabilizes the assembled SNARE complex in a partially zippered state
Prevents full SNARE complex assembly before calcium influx
Maintains vesicles in a release-ready (primed) state

Release Triggering

Upon calcium entry through voltage-gated calcium channels:
CPLX3 undergoes conformational change
Allows complete SNARE complex zippering
Triggers synaptic vesicle fusion and neurotransmitter release

Dual Function Model

Complexins act as both clamps (preventing premature fusion) and activators (facilitating triggered release)
This dual role is crucial for precise temporal control of synaptic transmission [3]

Specific Roles in Sensory Synapses

In the retina, CPLX3 has unique functions:

Regulates vesicle release at ribbon synapses (continuous synaptic transmission)
Controls synaptic vesicle pools in photoreceptor terminals
Modulates bipolar cell ribbon synapse function
Essential for proper visual signal transduction

Expression Pattern

CPLX3 exhibits a distinctive expression pattern:

Retina

Photoreceptor cells: High expression in rod and cone photoreceptors
Bipolar cells: Strong expression in both ON and OFF bipolar cells
Horizontal cells: Moderate expression
Amacrine cells: Variable expression

Brain

[Hippocampus](/brain-regions/hippocampus): CA1-CA3 pyramidal neurons, dentate gyrus granule cells
Cerebral cortex: Layer 2/3 pyramidal neurons, interneurons
Olfactory bulb: Mitral cells, tufted cells
Cerebellum: Purkinje cells, granule cells
Substantia nigra: Dopaminergic neurons

Cellular Localization

Synaptic vesicles in pre-synaptic terminals
Pre-synaptic plasma membrane
Ribbons in retinal photoreceptors

Disease Associations

Retinal Degeneration

CPLX3 mutations are associated with:

Cone-rod dystrophy
Progressive retinal degeneration
Visual acuity loss
Photoreceptor dysfunction [4]

Alzheimer's Disease

In [Alzheimer's disease](/diseases/alzheimers-disease):

CPLX3 expression is altered in AD brains
SNARE complex dysfunction contributes to synaptic loss
Impaired neurotransmitter release affects learning and memory
CPLX3 may interact with [amyloid-beta](/proteins/amyloid-beta) pathology [5]

Epilepsy

CPLX3 dysregulation is implicated in epilepsy:

Altered inhibitory/excitatory balance at synapses
Mutations cause seizure phenotypes in animal models
Dysregulated synaptic transmission contributes to epileptogenesis

Neurodevelopmental Disorders

CPLX3 is linked to:

Intellectual disability
Autism spectrum disorders
Developmental delay
Synaptic developmental defects [6]

Parkinson's Disease

In [Parkinson's disease](/diseases/parkinsons-disease):

SNARE-mediated vesicle trafficking is impaired
Dopaminergic neuron synaptic dysfunction
Interaction with [α-synuclein](/proteins/alpha-synuclein) pathology

Therapeutic Implications

Drug Development

Targeting CPLX3 and SNARE regulation:

SNARE complex stabilizers: Enhance synaptic transmission
Calcium channel modulators: Control release timing
Synaptic vesicle cycle enhancers: Improve neurotransmitter release

Gene Therapy

For CPLX3-related retinal disorders:

Viral vector delivery of functional CPLX3
CRISPR-based gene editing
Optogenetic approaches to restore vision

Biomarkers

CPLX3 expression may serve as:

Indicator of synaptic integrity
Marker for retinal health
Therapeutic response indicator

Research Directions

Ongoing research focuses on:

Understanding CPLX3 function at ribbon synapses
Characterizing CPLX3 mutations in retinal disease
Developing therapies for CPLX3-related disorders
Elucidating CPLX3 roles in neurodegenerative diseases
Single-cell analysis of CPLX3 in specific neuron populations

Background

The study of Cplx3 — Complexin 3 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.

Pathway Diagram

The following diagram shows the key molecular relationships involving CPLX3 — Complexin-3 discovered through SciDEX knowledge graph analysis:

Mermaid diagram (expand to render)

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CPLX3 — Complexin-3

CPLX3 — Complexin-3

Introduction

CPLX3 — Complexin-3

Introduction

Overview

Protein Structure

N-Terminal Domain

Central Region

C-Terminal Domain

Molecular Function

SNARE Complex Regulation

Specific Roles in Sensory Synapses

Expression Pattern

Retina

Brain

Cellular Localization

Disease Associations

Retinal Degeneration

Alzheimer's Disease

Epilepsy

Neurodevelopmental Disorders

Parkinson's Disease

Therapeutic Implications

Drug Development

Gene Therapy

Biomarkers

Research Directions

Background

See Also

Pathway Diagram