Figure 1.

FcεRI activation. Upon FcεRI aggregation, Lyn initiates downstream signaling events through phosphorylation of ITAMs on FcεRI β and γ. Syk binds phosphorylated γ ITAM, and Lyn phosphorylates tyrosine residue of FcεRIγ-bound Syk. Activated Lyn and Syk further phosphorylate many downstream signaling molecules, leading to degranulation and de-novo synthesis of chemokines, cytokines, and lipid mediators. Under strong stimuli, Lyn recruits SHIP1 and SHP-1 via the phosphorylated FcεRI β ITAM and suppresses the reaction.