The Eph family of receptor tyrosine kinases and their ephrin ligands are key regulators of cell positioning, synaptic plasticity, and developmental patterning. The Eph/ephrin system mediates bidirectional signaling that controls axonal guidance, synapse formation, and neural circuit assembly. In neurodegenerative diseases, Eph/ephrin signaling is dysregulated and contributes to synaptic dysfunction, impaired regeneration, and neuroinflammation. Understanding this pathway offers therapeutic opportunities for conditions like Alzheimer's disease, Parkinson's disease, and stroke. [@klein2012]
The Eph family of receptor tyrosine kinases and their ephrin ligands are key regulators of cell positioning, synaptic plasticity, and developmental patterning. The Eph/ephrin system mediates bidirectional signaling that controls axonal guidance, synapse formation, and neural circuit assembly. In neurodegenerative diseases, Eph/ephrin signaling is dysregulated and contributes to synaptic dysfunction, impaired regeneration, and neuroinflammation. Understanding this pathway offers therapeutic opportunities for conditions like Alzheimer's disease, Parkinson's disease, and stroke. [@klein2012]
EphB2 is critically involved in synaptic function: [@murai2003] [@coon2019]
Synaptic localization: EphB2 is enriched at excitatory synapses
NMDA receptor interaction: EphB2 regulates NMDA receptor function and trafficking
A beta-induced dysfunction: A beta reduces EphB2 expression and disrupts signaling [@fu2018]
Memory impairment: Restoring EphB2 reverses memory deficits in AD mouse models
The downregulation of EphB2 by amyloid-beta oligomers contributes to synaptic failure and cognitive decline in AD. Therapeutic approaches aimed at enhancing EphB2 signaling are being explored as potential treatments for synaptic dysfunction in AD.
Ephrin-A Signaling
Ephrin-A5 modulates amyloid precursor protein (APP) processing
EphA4 activation contributes to synaptic loss and dendritic spine simplification
EphA4 antagonists promote synaptic repair and functional recovery
Therapeutic targeting of EphA4 being explored in preclinical models
Regeneration and Plasticity
Impaired Eph/ephrin signaling contributes to regenerative failure after injury
Blocking EphA4 promotes axon regeneration after CNS injury
Bidirectional signaling regulates neural circuit assembly during development and adulthood
Role in Parkinson's Disease
Dopaminergic System Development
EphB receptors regulate development of dopaminergic neurons in the substantia nigra
Axonal guidance molecules influence substantia nigra connectivity and circuit formation
Eph/ephrin signaling during development may determine vulnerability of dopaminergic neurons
Synaptic Function
Dysregulated EphB signaling affects striatal synapse function and plasticity
Contributes to basal ganglia circuit dysfunction in PD
Alpha-synuclein pathology may disrupt Eph/ephrin signaling pathways
Role in Stroke and Brain Injury
Ischemic Damage
EphA/ephrin-A signaling is upregulated after stroke and brain injury
Mediates post-ischemic inflammation and angiogenesis
Bidirectional signaling affects both neurons and vasculature
EphA4 and ephrin-A5 are particularly implicated in post-injury responses
Regeneration
Manipulating Eph/ephrin signaling can promote or inhibit regeneration
EphA4 antagonists improve functional recovery after stroke [@chen2019]
[H et al. 2025: Idebenone Mitigates Traumatic-Brain-Injury-Triggered Gene Expression Changes in the Prefrontal Cortex](https://pubmed.ncbi.nlm.nih.gov/40498000/)
[H et al. 2025: Idebenone Enhances the Early Microglial Response to Traumatic Brain Injury](https://pubmed.ncbi.nlm.nih.gov/40654680/)
[Murai KK, Pasquale EB. Eph/ephrin signaling in the formation of the central nervous system. Neuroscientist. 2004](https://pubmed.ncbi.nlm.nih.gov/15587550/)
[Klein R. Eph/ephrin signaling in brain development and disease. Neuron. 2012](https://pubmed.ncbi.nlm.nih.gov/22920252/)
[Xu NJ, Henkemeyer M. Ephrin-B3 binding and cognitive function. Nat Rev Neurosci. 2012](https://pubmed.ncbi.nlm.nih.gov/23047776/)
[Coon AL, et al., EphB2 in hippocampal synaptic plasticity and memory. J Neurosci. 2019](https://pubmed.ncbi.nlm.nih.gov/31053618/)