FGF22 is a paracrine fibroblast growth factor member of the FGF7 subfamily that functions as a presynaptic organizer with broad roles in neuronal development and neuroprotection 1. Primary Function: FGF22 acts as a postsynaptic-cell-derived presynaptic organizer essential for excitatory synapse formation, requiring selective intracellular transport via KIF3A/KIF17 motor proteins and SAP102 adaptor protein to localize at excitatory synaptic sites 2. Mechanism: FGF22 signals through FGFR1/FGFR2 receptors, activating multiple pathways including Wnt/β-Catenin, Sonic Hedgehog, and Notch signaling to promote neuronal proliferation and differentiation 3. The protein also engages the FGFR2/YAP axis to suppress ferroptosis-mediated neurodegeneration 4. Disease Relevance: FGF22 shows therapeutic potential in spinal cord injury through enhanced circuit rewiring and functional recovery when applied within 24 hours of lesion 5. In Alzheimer's disease, FGF22 reduces ferroptosis and neuronal apoptosis, ameliorating cognitive deficits 4. FGF22 exhibits neuroprotective effects in depression via IL-1β downregulation 6. However, elevated FGF22/FGFR2 signaling in pancreatic cancer promotes fibroblast-cancer cell crosstalk, facilitating invasion and metastasis 7. Clinical Significance: FGF22 represents a promising synaptogenic therapeutic target for neurological disorders, though cancer contexts require pathway inhibition rather than activation.