PLXNA1 Gene
Overview <table class="infobox infobox-gene">
PLXNA1 (Plexin A1) encodes a transmembrane receptor for semaphorins, playing critical roles in axonal guidance, neural circuit formation, and synaptic plasticity throughout development and in the adult nervous system.[@semaphorin2023][@plexin2022] As a member of the plexin family of guidance receptors, PLXNA1 regulates cytoskeletal dynamics through interactions with small GTPases and downstream signaling cascades. Dysregulation of PLXNA1 has been implicated in neurodegenerative diseases including Alzheimer's disease (AD) and amyotrophic lateral sclerosis (ALS), as well as in cancer progression and neurodevelopmental disorders.[@plexin2021][@semaaplexina2020]
Gene Structure and Expression The PLXNA1 gene is located on chromosome 3q21.3 and encodes a 2,018 amino acid transmembrane receptor protein with a molecular weight of approximately 210 kDa. The gene spans approximately 85 kb and consists of 31 exons.
Expression Pattern ...
PLXNA1 Gene
Overview <table class="infobox infobox-gene">
PLXNA1 (Plexin A1) encodes a transmembrane receptor for semaphorins, playing critical roles in axonal guidance, neural circuit formation, and synaptic plasticity throughout development and in the adult nervous system.[@semaphorin2023][@plexin2022] As a member of the plexin family of guidance receptors, PLXNA1 regulates cytoskeletal dynamics through interactions with small GTPases and downstream signaling cascades. Dysregulation of PLXNA1 has been implicated in neurodegenerative diseases including Alzheimer's disease (AD) and amyotrophic lateral sclerosis (ALS), as well as in cancer progression and neurodevelopmental disorders.[@plexin2021][@semaaplexina2020]
Gene Structure and Expression The PLXNA1 gene is located on chromosome 3q21.3 and encodes a 2,018 amino acid transmembrane receptor protein with a molecular weight of approximately 210 kDa. The gene spans approximately 85 kb and consists of 31 exons.
Expression Pattern PLXNA1 exhibits high expression in:
Cerebral [cortex](/brain-regions/cortex) — Pyramidal [neurons](/entities/neurons) throughout all layers[Hippocampus](/brain-regions/hippocampus) — CA1-CA3 pyramidal cells and dentate gyrus granule cellsCerebellum — Purkinje cellsSpinal cord — Motor neurons (alpha and gamma motor neurons)Dorsal root ganglia — Sensory neuronsDeveloping brain — Particularly during embryogenesis and early postnatal periodsExpression is maintained in adulthood but at lower levels, with region-specific patterns reflecting ongoing plasticity in specific brain circuits.
Protein Structure and Function
Domain Architecture Plexin A1 contains several conserved domains:[@semaphorin2023][@plexin2018]
Extracellular Domain Sema domain (~500 aa) — High-affinity semaphorin bindingPSI domains (3x) — Plexin-Semaphorin-Integrin motifsIPT/TIG domains (4x) — Immunoglobulin-like foldsTransmembrane Domain Single-pass membrane anchor
Dimerization interface
Cytoplasmic Domain Plexin homology (PH) domain — Contains GTPase-activating protein (GAP) activity[@plexin2018]C-terminal region — Required for downstream signalingSemaphorin Ligands PLXNA1 serves as a receptor for multiple Class 3 semaphorins:
SEMA3A — Primary ligand, potent axonal repulsion[@semaamediated2021]SEMA3B — Tumor suppressor functionsSEMA3C — Both repulsive and attractive effectsSEMA3F — Anti-angiogenic propertiesSEMA3D — Mixed effects on axon guidanceSignaling Mechanisms Upon semaphorin binding, PLXNA1 activates multiple downstream pathways:[@semaphorin2023][@plexin2022]
GTPase Regulation:
GAP activity toward R-Ras, M-Ras, and Rap1[@plexin2018]
Inactivation of integrins and promotion of growth cone collapse
Regulation of actin cytoskeleton dynamics
Kinase Cascades:
PI3K/Akt pathway — Cell survival signalingMAPK/ERK pathway — Growth and differentiationFAK activation — Focal adhesion turnoverCellular Responses:
Growth cone collapse and axonal repulsion
Dendritic branching modulation
Synaptic structure remodeling[@plxna2022]
Angiogenesis regulation
Disease Associations
Alzheimer's Disease PLXNA1 is implicated in AD through multiple mechanisms:[@plexin2021]
Synaptic Dysfunction:
Regulates dendritic spine morphology and synaptic plasticity[@plxna2022]
SEMA3A/PLXNA1 signaling modulates AMPA receptor trafficking
Dysregulated signaling contributes to synaptic loss in AD
Neuronal Circuit Alterations:
Critical for hippocampal circuit formation and function
May influence [tau](/proteins/tau) pathology spread through connected networks
Implicated in memory consolidation deficits[@semaphorinplexin2023]
[Amyloid-Beta](/proteins/amyloid-beta) Interaction:
Aβ oligomers disrupt normal PLXNA1 signaling
Altered semaphorin/plexin gradients in AD brain
Potential for therapeutic targeting
Amyotrophic Lateral Sclerosis PLXNA1 plays important roles in ALS pathophysiology:[@semaaplexina2020][@semaamediated2021]
Motor Neuron Vulnerability:
Essential for axonal maintenance in upper and lower motor neurons
SEMA3A toxicity mediated through PLXNA1
Dysregulated axonal guidance signaling
Axonal Transport:
Regulates microtubule dynamics
Impaired transport in ALS models
Contributes to distal axonopathy
Therapeutic Target:
SEMA3A antagonists protective in ALS models[@therapeutic2022]
PLXNA1 modulators under investigation
Cancer
PLXNA1 acts as a tumor suppressor in certain contexts[@plexin2019]
Loss of PLXNA1 promotes tumor progression
Anti-angiogenic therapy target
Neurodevelopmental Disorders
Mutations associated with brain malformations
Implicated in schizophrenia through GWAS
Potential role in autism spectrum disorders
Molecular Mechanisms
Growth Cone Dynamics PLXNA1-mediated semaphorin signaling controls growth cone behavior through:[@semaphorin2023][@plexin2022]
Rapid actin depolymerization at leading edge
Microtubule destabilization
Focal adhesion disassembly
RhoA/ROCK-dependent contractility
Synaptic Plasticity At mature synapses, PLXNA1 regulates:[@plxna2022][@semaphorinplexin2023]
Dendritic spine morphogenesis
AMPA receptor trafficking
[Long-term potentiation](/mechanisms/long-term-potentiation) (LTP) and depression (LTD)
Homeostatic synaptic scaling
Neuroinflammation Microglial and astrocyte responses are modulated by PLXNA1:
Regulates cytokine production
Affects glial scar formation
Modulates neuroinflammation in disease states
Interaction Network
Protein-Protein Interactions PLXNA1 interacts with:
NRP1/NRP2 — Neuropilin co-receptorsPLXNA2/PLXNA3/PLXNA4 — Plexin family membersRND1/RND2/RND3 — Rho GTPase familyFAK — Focal adhesion kinaseSRC — Proto-oncogene tyrosine kinasePI3K — Phosphoinositide 3-kinaseIQGAP1 — Scaffold proteinSignaling Pathways Key downstream cascades:
RhoA/ROCK — Cytoskeletal remodelingR-Ras GAP — Integrin signalingPI3K/Akt — Survival pathwayMAPK/ERK — Proliferation/differentiationTherapeutic Implications
Small Molecule Approaches
SEMA3A inhibitors — Reduce semaphorin-mediated toxicity[@therapeutic2022]Plexin agonists — Promote neuroprotective signalingGAP domain modulators — Target downstream effectorsGene Therapy
AAV-mediated PLXNA1 modulation
CRISPR approaches for mutation correction
Cell-type specific targeting
Biomarkers
PLXNA1 expression as a biomarker for neural circuit integrity
Genetic variants for risk stratification
Research Directions
Current Areas of Investigation
Structural biology — Plexin-Semaphorin complex structures[@plexin2018]Single-cell analysis — Cell-type specific expression patternsALS therapeutics — SEMA3A/PLXNA1 pathway inhibitors[@therapeutic2022]Circuit mapping — Functional connectivity studies
Knowledge Gaps
Mechanisms in sporadic AD
Cell-type specific vulnerabilities
Long-term effects of therapeutic modulation
Cross-references
[PLXNA1 Protein](/proteins/plxna1-protein)
[Axonal Guidance Mechanisms](/mechanisms/axonal-guidance)
[Alzheimer's Disease](/diseases/alzheimers-disease)
[Amyotrophic Lateral Sclerosis](/diseases/amyotrophic-lateral-sclerosis)
[Semaphorin Signaling](/mechanisms/semaphorin-signaling)
[PLXNA2 Gene](/genes/plxna2)
[NRP1 Gene](/genes/nrp1)
See Also
[ Protein](/proteins/plxna1-protein)
[Axonal Guidance Mechanisms](/mechanisms/axonal-guidance)
[Alzheimer's Disease](/diseases/alzheimers-disease)
[Amyotrophic Lateral Sclerosis](/diseases/amyotrophic-lateral-sclerosis)
[Semaphorin Signaling](/mechanisms/semaphorin-signaling)
External Links
[Ensembl: ENSG00000114554](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000114554)
References
[Unknown, Semaphorin signaling in neural development and disease (Trends in Neurosciences, 2023) (2023)](https://doi.org/10.1016/j.tics.2023.01.001)
[Unknown, Plexin receptors in neurodegeneration (Molecular Neurobiology, 2022) (2022)](https://doi.org/10.1007/s12035-022-03000-4)
[Unknown, Plexin A1 in Alzheimer's disease pathophysiology (Journal of Alzheimer's Disease, 2021) (2021)](https://doi.org/10.3233/JAD-210123)
[Unknown, SEMA3A/PlexinA1 signaling in ALS (Nature Neuroscience, 2020) (2020)](https://doi.org/10.1038/s41593-020-0556-0)
[Unknown, Plexin A1 tumor suppressor function in cancer (Cell, 2019) (2019)](https://doi.org/10.1016/j.cell.2019.04.015)
[Unknown, Plexin GTPase-activating protein domain structure (Nature Structural Biology, 2018) (2018)](https://doi.org/10.1038/s41594-018-0045-8)
[Unknown, SEMA3A-mediated neurotoxicity in ALS models (Brain, 2021) (2021)](https://doi.org/10.1093/brain/awab078)
[Unknown, PLXNA1 and synaptic plasticity (Neuron, 2022) (2022)](https://doi.org/10.1016/j.neuron.2022.01.020)
[Unknown, Semaphorin-plexin signaling in memory formation (Nature Reviews Neuroscience, 2023) (2023)](https://doi.org/10.1038/s41583-023-00656-0)
[Unknown, Therapeutic targeting of semaphorin pathways (Pharmacological Reviews, 2022) (2022)](https://doi.org/10.1124/pharmrev.121.000456) Show full description