The FYN gene (FYN Proto-Oncogene, Src Family Tyrosine Kinase) encodes a member of the Src family of non-receptor tyrosine kinases (SFKs). FYN is a critical signaling molecule in the nervous system, playing essential roles in synaptic plasticity, learning and memory, NMDA receptor function, and myelin formation. Dysregulation of FYN signaling is implicated in Alzheimer's disease, Parkinson's disease, schizophrenia, and multiple sclerosis.
| Attribute |
Value |
| Symbol |
FYN |
| Full Name |
FYN Proto-Oncogene, Src Family Tyrosine Kinase |
| Chromosomal Location |
6q21 |
| NCBI Gene ID |
2534 |
| OMIM ID |
137025 |
| Ensembl ID |
ENSG00000110881 |
| UniProt ID |
P39687 |
| Protein Size |
537 amino acids |
| Molecular Weight |
~60 kDa |
FYN, like all Src family kinases, contains several conserved domains:
- N-terminal myristoylation site: Targets FYN to the plasma membrane
- Unique domain: Confers specificity to each SFK member
- SH3 domain: Proline-rich region binding
- SH2 domain: Phosphotyrosine-containing motif binding
- Kinase domain: Catalytic tyrosine kinase activity
FYN exists in two isoforms:
- FYN-B: Full-length isoform, predominant in brain
- FYN-A: Alternatively spliced variant with different tissue distribution
FYN plays multiple critical roles in the nervous system:
¶ Synaptic Plasticity and Learning
- NMDA Receptor Phosphorylation: FYN phosphorylates NR2A and NR2B subunits, modulating receptor function
- PSD-95 Interaction: Forms signaling complexes at postsynaptic densities
- Long-term Potentiation (LTP): Essential for LTP induction in hippocampal neurons
- Learning and Memory: FYN knockout mice show deficits in spatial memory
- Oligodendrocyte Development: Critical for proper myelination
- Node of Ranvier Organization: Regulates sodium channel clustering
- Receptor Tyrosine Kinase Signaling: Mediates responses to growth factors
- Integrin Signaling: Controls neuronal adhesion and migration
- Immune Receptor Signaling: T-cell receptor signaling in microglia
FYN is expressed throughout the brain with highest levels in:
- Cerebral cortex (layers II-IV pyramidal neurons)
- Hippocampus (CA1-CA3 pyramidal cells, dentate gyrus granule cells)
- Cerebellum (Purkinje cells)
- Basal ganglia (striatum, substantia nigra)
- Thalamus and hypothalamus
Outside the brain, FYN is expressed in T-cells, NK cells, and other immune cells.
FYN is centrally involved in AD pathogenesis:
- Tau Phosphorylation: FYN can phosphorylate tau at tyrosine residues, promoting pathology
- NMDA Receptor Dysfunction: FYN-mediated phosphorylation contributes to excitotoxicity
- Amyloid-beta Signaling: Aβ activates FYN, linking amyloid to downstream toxic signaling
- Synaptic Loss: FYN-dependent pathways contribute to synaptic impairment
- Therapeutic Target: FYN inhibitors are being investigated for AD treatment
- Dopaminergic Signaling: FYN regulates dopamine receptor signaling
- Alpha-synuclein Phosphorylation: FYN can phosphorylate α-synuclein at Tyr125
- Neuroprotection: FYN activity is required for neuroprotective responses
- NMDA Receptor Hypofunction: FYN deficiency may contribute to NMDA receptor dysfunction
- Cognitive Deficits: Linked to working memory impairments
- Immune Cell Activation: FYN in T-cells contributes to autoimmune responses
- Demyelination: Altered signaling in oligodendrocytes
| Drug/Compound |
Mechanism |
Status |
| Dasatinib |
Broad SFK inhibitor |
FDA-approved for CML |
| Bosutinib |
SFK inhibitor |
FDA-approved for CML |
| Saracatinib (AZD0530) |
FYN-selective inhibitor |
Phase II for AD |
| FYN-specific compounds |
Selective targeting |
Preclinical |
FYN interacts with multiple signaling cascades:
- PI3K/Akt Pathway: Downstream survival signaling
- MAPK/ERK Pathway: Growth and differentiation
- PLCγ Pathway: Calcium signaling
- STAT Pathway: Transcriptional regulation
- FYN knockout mice display enhanced sensitivity to Aβ toxicity
- Saracatinib (AZD0530) showed promise in AD clinical trials for cognitive symptoms
- FYN gene variants are associated with schizophrenia risk