Figure 5. The IL-11-Like peptide CGRRAGGSC induces STAT3 activation upon binding to IL-11Rα in a concentration-dependent manner.

(A) Proliferation of human TF-1 leukemia cells induced by CGRRAGGSC is associated with STAT3 phosphorylation, as assessed with an anti-STAT3-P-Tyr⁷⁰⁵ antibody. (B) CGRRAGGSC peptide-induced activation of STAT3 is concentration dependent. No effect is observed with a control peptide. To avoid inter-experimental variation, the lysate was divided in two: one-half of the lysate was immunoblotted with an anti-STAT3-P-Tyr⁷⁰⁵ antibody whereas the other half served to determine the total amount of STAT3 (as a surrogate for protein loading) with a specific anti-STAT3 antibody. Note that the commercial HeLa cell extracts serving as controls display only the ∝-STAT3 band.