Protein kinase C theta is expressed in mast cells and is functionally involved in Fc epsilon receptor I signaling

We investigated possible expression and function in mast cells of protein k inase C (PKC) theta, a member of the PKC family with demonstrated function in a limited range of cell types. We found that PKC theta is expressed in b one marrow-derived mast cells and in the RBL-2H3 mast cell line. PKC theta underwent translocation to the membrane in response to Fc epsilon receptor I(Fc epsilonR I) activation. Receptor activation induced phosphorylation of PKC theta, The tyrosine phosphorylation of PKC theta is delayed relative t o PKC delta and coincides temporally with PKC theta association with c-src family members Lyn and Src, Studies of RBL-2H3 cells transduced with PKC th eta constructs indicated a role for PKC theta in receptor-induced activatio n of extracellular regulated kinases, interleukin-3 gene transcription, and degranulation in response to antigen stimulation. These studies extend the known functions of PKC theta to another important immune cell type and ind icate the concurrent participation of multiple PKCs in the Fc epsilonR I-me diated response of mast cells.