PLXNA2 (Plexin A2) encodes a member of the plexin family of transmembrane receptors for semaphorins, playing critical roles in neural development, circuit formation, and synaptic plasticity. Plexin A2 is essential for axonal guidance during development and continues to regulate synaptic structure and function in the adult brain.[@plexin2021] Dysregulation of PLXNA2 has been implicated in neurodegenerative diseases, particularly Alzheimer's disease, as well as neurodevelopmental disorders including autism spectrum disorder (ASD) and schizophrenia.[@semaaplexina2020][@plxna2019]
Gene Structure and Expression
The PLXNA2 gene spans approximately 127 kb on chromosome 1q23.3 and consists of 33 exons encoding a 2,034 amino acid transmembrane receptor protein with a molecular weight of approximately 220 kDa.
PLXNA2 (Plexin A2) encodes a member of the plexin family of transmembrane receptors for semaphorins, playing critical roles in neural development, circuit formation, and synaptic plasticity. Plexin A2 is essential for axonal guidance during development and continues to regulate synaptic structure and function in the adult brain.[@plexin2021] Dysregulation of PLXNA2 has been implicated in neurodegenerative diseases, particularly Alzheimer's disease, as well as neurodevelopmental disorders including autism spectrum disorder (ASD) and schizophrenia.[@semaaplexina2020][@plxna2019]
Gene Structure and Expression
The PLXNA2 gene spans approximately 127 kb on chromosome 1q23.3 and consists of 33 exons encoding a 2,034 amino acid transmembrane receptor protein with a molecular weight of approximately 220 kDa.
[Hippocampus](/brain-regions/hippocampus) — CA1-CA3 regions and dentate gyrus granule cells
Cerebellum — Purkinje cells and granule cells
Olfactory bulb — mitral and tufted cells
Thalamus — relay neurons
Substantia nigra — dopaminergic neurons
Expression peaks during embryonic development and early postnatal periods, with sustained expression in adulthood particularly in regions undergoing continuous plasticity.[@plexin2021]
Cytoplasmic domain — Plexin homology (PH) domain with GTPase-activating protein (GAP) activity for R-Ras and Rap GTPases[@plexin2018]
Semaphorin Signaling
Plexin A2 functions as the primary receptor for Class 3 semaphorins (SEMA3A, SEMA3B, SEMA3C, SEMA3F). Binding induces receptor dimerization and activation of downstream signaling cascades:
Axonal repulsion — SEMA3A binding to PLXNA2 triggers growth cone collapse through RhoA/ROCK-dependent cytoskeletal remodeling[@plexin2021]
Synaptic scaling — PLXNA2 modulates AMPA receptor trafficking via Rap GAP activity[@plexin2022]
Dendritic arborization — Regulates dendritic branching complexity through R-Ras inactivation
Plexin Co-receptors
PLXNA2 forms complexes with:
NRP1 (Neuropilin 1) — Primary co-receptor for SEMA3A/F
NRP2 (Neuropilin 2) — Co-receptor for SEMA3C/F
Plexin A1 — Heterodimeric receptor complexes
Plexin A4 — Coordination in sensory neuron guidance
Disease Associations
Alzheimer's Disease
PLXNA2 is implicated in Alzheimer's disease through multiple mechanisms:[@semaaplexina2020][@amyloidbeta2022]
Synaptic Dysfunction:
PLXNA2-mediated signaling regulates dendritic spine morphology and synaptic plasticity
[Amyloid-beta](/proteins/amyloid-beta) oligomers disrupt SEMA3A/PLXNA2 signaling, leading to synaptic loss
Altered PLXNA2 expression correlates with cognitive decline in AD patients
Neuronal Circuit Alterations:
SEMA3A/PLXNA2 dysregulation contributes to hippocampal circuit dysfunction
Implicated in [entorhinal cortex](/brain-regions/entorhinal-cortex)-to-hippocampal connectivity deficits
May influence [tau](/proteins/tau) pathology propagation along neuronal circuits
Genetic Evidence:
GWAS studies have identified PLXNA2 variants associated with late-onset AD risk[@gwas2019]
Expression quantitative trait loci (eQTLs) in PLXNA2 correlate with AD severity
Autism Spectrum Disorder (ASD)
PLXNA2 is one of the most consistently implicated genes in ASD:[@plxna2019][@semaphorinplexin2021]
Synaptogenesis Defects:
Critical for excitatory synapse formation and function