Protein kinase C θ is expressed in mast cells and is functionally involved in Fcɛ receptor I signaling

We investigated possible expression and function in mast cells ofprotein kinase C (PKC) θ, a member of the PKC family withdemonstrated function in a limited range of cell types. We found thatPKC θ is expressed in bone marrow-derived mast cells and in the RBL-2H3 mast cell line. PKC θ underwent translocation to the membranein response to Fcɛ receptor I (FcɛR I) activation. Receptoractivation induced phosphorylation of PKC θ. The tyrosinephosphorylation of PKC θ is delayed relative to PKC δ and coincidestemporally with PKC θ association with c-src family members Lyn andSrc. Studies of RBL-2H3 cells transduced with PKC θ constructsindicated a role for PKC θ in receptor-induced activation ofextracellular regulated kinases, interleukin-3 gene transcription, anddegranulation in response to antigen stimulation. These studies extendthe known functions of PKCθ to another important immune cell type andindicate the concurrent participation of multiple PKCs in the FcɛRI-mediated response of mast cells.