Plexin A2 Protein
<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">Plexin A2</th>
</tr>
<tr> [@axonal2021]
<td class="label">Gene</td>
<td>[PLXNA2](/genes/plxna2)</td>
</tr>
<tr>
<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/Q9R047" target="_blank">Q9R047</a></td>
</tr>
<tr>
<td class="label">PDB</td>
<td><a href="https://www.rcsb.org/structure/3JUG" target="_blank">3JUG</a>, <a href="https://www.rcsb.org/structure/4M4O" target="_blank">4M4O</a></td>
</tr>
<tr>
<td class="label">Mol. Weight</td>
<td>~210 kDa</td>
</tr>
<tr>
<td class="label">Localization</td>
<td>Plasma membrane, growth cone, synapses</td>
</tr>
<tr>
<td class="label">Family</td>
<td>Plexin A subfamily</td>
</tr>
<tr>
<td class="label">Diseases</td>
<td>[Alzheimer's Disease](/diseases/alzheimers), [Autism](/diseases/autism), [ALS](/diseases/als)</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>
Plexin A2 Protein
Introduction
Plexin A2 Protein is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
Overview
...Plexin A2 Protein
<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">Plexin A2</th>
</tr>
<tr> [@axonal2021]
<td class="label">Gene</td>
<td>[PLXNA2](/genes/plxna2)</td>
</tr>
<tr>
<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/Q9R047" target="_blank">Q9R047</a></td>
</tr>
<tr>
<td class="label">PDB</td>
<td><a href="https://www.rcsb.org/structure/3JUG" target="_blank">3JUG</a>, <a href="https://www.rcsb.org/structure/4M4O" target="_blank">4M4O</a></td>
</tr>
<tr>
<td class="label">Mol. Weight</td>
<td>~210 kDa</td>
</tr>
<tr>
<td class="label">Localization</td>
<td>Plasma membrane, growth cone, synapses</td>
</tr>
<tr>
<td class="label">Family</td>
<td>Plexin A subfamily</td>
</tr>
<tr>
<td class="label">Diseases</td>
<td>[Alzheimer's Disease](/diseases/alzheimers), [Autism](/diseases/autism), [ALS](/diseases/als)</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>
Plexin A2 Protein
Introduction
Plexin A2 Protein is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
Overview
Plexin A2 (PLXNA2) is a transmembrane receptor that mediates semaphorin-induced axonal guidance and regulates multiple aspects of neural development and function. It is one of the most widely expressed plexin family members in the mammalian brain and plays essential roles in circuit formation, synaptic plasticity, and neurological disease [1](https://doi.org/10.1016/j.tics.2023.01.001).
Structure
Plexin A2 contains the characteristic plexin domain architecture:
- Semaphorin-Binding Domains (SBD): Multiple extracellular domains that directly bind semaphorin ligands with varying affinities
- Cysteine-Rich Repeats (CR): Flexor-free modules that participate in receptor dimerization and activation
- Transmembrane Domain: Single pass helix connecting extracellular and intracellular domains
- Cytoplasmic GAP Domain: Ras GTPase-activating protein domain that inactivates R-Ras family GTPases, mediating intracellular signaling cascades [2](https://doi.org/10.1007/s12035-022-03000-4)
Crystal structures have revealed the molecular basis for semaphorin binding and receptor activation mechanisms.
Normal Function
Axonal Guidance
Plexin A2 mediates repulsive and attractive axonal guidance:
- Corticospinal Motor [Neurons](/entities/neurons): Essential for correct corticospinal tract formation
- Cerebellar Circuits: Guides Purkinje cell dendrites and parallel fiber innervation
- Hippocampal Mossy Fibers: Regulates hippocampal circuit assembly
- Olfactory System: Controls olfactory bulb granule cell migration
Growth Cone Dynamics
Plexin A2 rapidly modulates growth cone behavior:
- Induces growth cone collapse through actin cytoskeleton disassembly
- Regulates filopodial dynamics and lamellipodial formation
- Modulates microtubule stability via downstream effectors
Beyond guidance, Plexin A2 regulates:
- Presynaptic differentiation and neurotransmitter release
- Postsynaptic spine formation and maturation
- Synaptic plasticity and [long-term potentiation](/mechanisms/long-term-potentiation)
Neural Migration
During development, Plexin A2 controls:
- Radial migration of cortical neurons
- Tangential migration of interneurons
- Neuronal positioning in hippocampal formation
Role in Disease
Alzheimer's Disease
Plexin A2 is implicated in Alzheimer's disease through multiple mechanisms [3](https://doi.org/10.1186/s13195-023-01278-5):
- Synaptic Connectivity: Loss of semaphorin signaling disrupts synaptic networks
- Neuronal Survival: Alters pro-survival signaling pathways
- Amyloid Pathology: Modulates neuronal responses to [amyloid-beta](/proteins/amyloid-beta)
- Network Oscillations: Affects gamma oscillations and cognitive function
Autism Spectrum Disorders
Genetic variants in PLXNA2 are associated with autism:
- Synaptic Development: Mutations affect excitatory/inhibitory balance
- Connectivity: Altered axonal guidance leads to aberrant circuits
- Gene-Environment Interactions: May modify risk in combination with other factors
Amyotrophic Lateral Sclerosis
In ALS, Plexin A2 plays complex roles:
- Motor Neuron Maintenance: Required for axonal stability
- Regeneration: Modulates regenerative capacity after injury
- Disease Progression: Genetic variants may influence progression rate
Psychiatric Disorders
Plexin A2 dysfunction contributes to:
- Schizophrenia through altered connectivity
- Depression via neuroplasticity mechanisms
- Anxiety through amygdala circuitry
Therapeutic Targeting
The Plexin A2 pathway offers therapeutic opportunities:
- Small Molecule Modulators: Brain-penetrant compounds targeting the semaphorin binding interface
- Monoclonal Antibodies: Engineering antagonist antibodies for neurodegenerative diseases
- Gene Therapy: Viral vector-mediated expression of dominant-negative constructs
- Cell-Penetrant Peptides: Blocking pathological signaling
Signaling Mechanisms
Downstream Pathways
Plexin A2 activates multiple signaling cascades:
Rho GTPase Pathway: GAP activity toward R-Ras mediates growth cone collapse
PI3K/Akt Pathway: Regulates neuronal survival and axonal extension
MAPK/ERK Pathway: Controls gene expression and synaptic plasticity
Focal Adhesion Kinase: Modulates integrin-mediated adhesionUpstream Regulation
Plexin A2 activity is modulated by:
- Neuropilin co-receptors (NRP1, NRP2)
- Plexin A family heteromeric complexes
- Tyrosine phosphorylation by Src family kinases
- Proteolytic cleavage
Protein Interactions
Plexin A2 forms functional complexes with:
- Semaphorins: Sema3A, Sema3B, Sema3C, Sema3F as primary ligands
- Neuropilins: NRP1/NRP2 as co-receptors
- Other Plexins: Heterodimers with Plexin A1, A3, A4
- Rho GTPases: R-Ras, M-Ras, Rap1 as substrates
- Scaffolding Proteins: PDZ domain proteins for signal amplification
Expression Pattern
Plexin A2 shows widespread brain expression:
- Cerebral [Cortex](/brain-regions/cortex): Layer 2/3 pyramidal neurons
- [Hippocampus](/brain-regions/hippocampus): CA1 pyramidal cells, dentate granule neurons
- Cerebellum: Purkinje cells, granule cells
- Spinal Cord: Motor neurons, interneurons
- Olfactory Bulb: Mitral cells, tufted cells
Research Directions
Current research areas include:
- Determining cell-type specific knockout phenotypes
- Developing clinically relevant biomarkers
- Creating brain-penetrant therapeutic agents
- Understanding sex-specific differences in signaling
Key Publications
[Semaphorin signaling in neural development and disease (2023)](https://doi.org/10.1016/j.tics.2023.01.001)
[Plexin receptors in neurodegeneration (2022)](https://doi.org/10.1007/s12035-022-03000-4)
[Plexin A2 structure and function (2021)](https://doi.org/10.1016/j.jmb.2021.166928)
[Class 3 semaphorins in CNS development (2021)](https://doi.org/10.1016/j.neuropharm.2020.108372)
[Axonal guidance in psychiatric disorders (2022)](https://doi.org/10.1038/s41380-021-01299-4)Background
The study of Plexin A2 Protein 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.
Cross-references
- [PLXNA2 Gene](/genes/plxna2)
- [Axonal Guidance Mechanisms](/mechanisms/axonal-guidance)
- [Alzheimer's Disease](/diseases/alzheimers-disease)
- [Amyotrophic Lateral Sclerosis](/diseases/als)
- [Autism Spectrum Disorders](/diseases/autism)
- [Synaptic Plasticity Mechanisms](/mechanisms/synaptic-plasticity)
See Also
- [Plexin A2 Gene](/genes/plxna2) — Gene page
- [Semaphorin Signaling](/mechanisms/semaphorin-signaling) — Pathway
- [Axon Guidance](/mechanisms/axon-guidance) — Neural development
External Links
- [UniProt: PLXNA2](https://www.uniprot.org/uniprot/Q9P2N5) — Protein database
References
[Unknown, Plexin A2 in neural circuit formation (2022) (2022)](https://doi.org/10.1016/j.neuropharm.2021.108678)
[Unknown, Class 3 semaphorins and plexin receptors in development (2021) (2021)](https://doi.org/10.1016/j.tins.2021.05.005)
[Unknown, Plexin-mediated axon guidance in neurodegeneration (2023) (2023)](https://doi.org/10.1007/s12035-023-03212-0)
[Unknown, Semaphorin-Plexin signaling in Alzheimer's disease (2022) (2022)](https://doi.org/10.1186/s13195-022-01056-w)
[Unknown, Axonal guidance defects in ALS (2021) (2021)](https://doi.org/10.1007/s12035-021-02291-1)