Activation of protein-tyrosine kinase Pyk2 is downstream of Syk in FcepsilonRI signaling.
Aggregation of the FcepsilonRI, a member of the immune receptor family, induces the activation of proteintyrosine kinases and results in tyrosine phosphorylation of proteins that are involved in downstream signaling pathways. Here we report that Pyk2, another member of the focal adhesion kinase family, was present in the RBL-2H3 mast cell line and was rapidly tyrosine-phosphorylated and activated after FcepsilonRI aggregation. Tyrosine phosphorylation of Pyk2 was also induced by the calcium ionophore A23187, by phorbol myristate acetate, or by stimulation of G-protein-coupled receptors. Adherence of cells to fibronectin dramatically enhanced the induced tyrosine phosphorylation of Pyk2. Although Src family kinases are activated by FcepsilonRI stimulation and tyrosine-phosphorylate the receptor subunits, the activation and tyrosine phosphorylation of Pyk2 were downstream of Syk. In contrast, tyrosine phosphorylation of Pyk2 by stimulation of G-protein-coupled receptors was independent of Syk. Therefore, the FcepsilonRI-induced tyrosine phosphorylation of Pyk2 is downstream of Syk and may play a role in cell secretion.
Okazaki
H
H
Receptors and Signal Transduction Section, Oral Infection and Immunity Branch, NIDR, National Institutes of Health, Bethesda, Maryland 20892-1188, USA. ho11o@nih.gov
Zhang
J
J
Hamawy
M M
MM
Siraganian
R P
RP
D002448:Cell Adhesion; D002460:Cell Line; D004789:Enzyme Activation; D004792:Enzyme Precursors / Q000378:metabolism; D051418:Focal Adhesion Kinase 2; D019204:GTP-Binding Proteins / Q000378:metabolism; D007139:Immunoglobulin epsilon-Chains / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D015398:Signal Transduction; D000072377:Syk Kinase; D014443:Tyrosine / Q000378:metabolism
D004792:Enzyme Precursors; D007139:Immunoglobulin epsilon-Chains; D047908:Intracellular Signaling Peptides and Proteins; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D051418:Focal Adhesion Kinase 2; D000072377:Syk Kinase; D019204:GTP-Binding Proteins