Tyrosine phosphorylation-dependent and -independent associations of protein kinase C-Δ with Src family kinases in the RBL-2H3 mast cell line: regulation of Src family kinase activity by protein kinase C-δ

Abstract

Src kinases and protein kinase C (PKC) have been well studied for their role in oncogenic and normal cellular processes. Herein we report on a novel regulatory pathway mediated by the interaction of PKC-δ with p53/56^Lyn (Lyn) and with p60^Src (Src) that results in the phosphorylation and increased activity of Lyn and Src. In the RBL-2H3 mast cell line, the interaction of PKC-δ with Lyn required the activation of the high affinity receptor for IgE (FcεRI) while the interaction with Src was constitutive. Increased complex formation of PKC-δ with Lyn or Src led to increased serine phosphorylation and activity of the Src family kinases. Conversely, Lyn was found to phosphorylate Lyn-associated and recombinant PKC-δ in vitro and the tyrosine 52 phosphorylated PKC-δ was recruited to associate with the Lyn SH2 domain. The constitutive association of PKC-δ with Src did not result in the tyrosine phosphorylation of PKC-δ prior to or after FcεRI engagement. However in cells over-expressing PKC-δ, FcεRI engagement resulted in the dramatic inhibition of Src activity and some inhibition of Lyn activity. Thus, the interaction and cross-talk of PKC-δ with Src family kinases suggests a novel and inter-dependent mechanism for regulation of enzymatic activity that may serve an important role in cellular responses.