Fyn, active

Fyn is a member of the src-related gene family of non-receptor tyrosine kinases. Recent studies indicate that fyn kinase plays a critical role in mediating signal transduction through the T-cell receptor thereby initiating a signal transduction cascade leading to lymphokine secretion and cell proliferation. One of the earliest biochemical responses following T-cell receptor activation is an increase in tyrosine kinase activity and concomitant phosphorylation of several intracellular substrates. Fyn kinase is an important mediator of this phosphorylation since it is physically associated with the T-cell receptor. Additional evidence supports the view that fyn participates in signal transduction pathways leading from multiple T-cell membrane proteins and hence may serve to integrate stimuli received from several independent receptor structures. In the case of the B-cell receptor, fyn is one of several kinases associated with the receptor and is activated following receptor cross-linking.