[6] Fyn is a 59-kDa member of the Src family of kinases typically associated with T-cell and neuronal signaling in development and normal cell physiology.

Fyn is functionally distinct from its family members in that it interacts with FAK and paxillin (PXN) in the regulation of cell morphology and motility.

[9] Fyn is primarily localized to the cytoplasmic leaflet of the plasma membrane, where it phosphorylates tyrosine residues on key targets involved in a variety of different signaling pathways.

[7] Fyn also appears to play an important role in fertilization including in the rapid Inositol trisphosphate-mediated calcium signaling which occurs when oocyte and sperm interact.

Knowing which pathways involve Fyn will provide key insight for the development of potential pharmacologic agents to attenuate this uncontrolled signaling.

[7] Additionally, in glioblastoma multiform, Src and Fyn have been found to be “effectors of oncogenic EGFR signaling” which has led to tumor invasion and cancer cell survival.

Normal FAK is a tyrosine kinase that gets recruited to focal adhesion sites and plays a key role in directed cell movement.

Additional pathways under investigation regarding Fyn’s role in cancer progression include: the Rac and Rho family of GTPases, Ras, Erk, and MAPK.

Furthermore, “expression of kinase-dead-Fyn (KD-Fyn), a specific competitor of endogenous Fyn,” was found to reduce the size of primary tumors in mice.