Figure 3.

Effect of ER-27319 on the phosphorylation of Syk induced by phosphorylated ITAMs or in anti-IgM stimulated human peripheral B cells. Cytosolic fractions of RBL-2H3 cell homogenates were incubated with the indicated concentration of ER-27319 (ER), 10 μM phosphorylated FcɛRI γ subunit ITAM (Pep1) (A) or Igβ ITAM (Pep2) (B) and 50 μM ATP (ATP) in kinase buffer as described in the text. (C) Human peripheral B cells were incubated in the presence (30 μM) or absence of ER-27319 before stimulation by anti-IgM. Syk was subsequently isolated with an antibody to Syk, resolved, and transferred to nitrocellulose membranes. Membranes were probed with anti-phosphotyrosine (Anti-PY) and subsequently reprobed with anti-Syk.