Inhibition of the EGF-induced activation of phospholipase C-γ1 by a single chain antibody fragment.

Abstract

Phospholipase C-γ1(PLC-γ1) is known to play an essential role in various cellular responses, such as proliferation and tumorigenesis, and PLC-γ1-specific inhibitors are commonly employed to investigate the mechanism of the PLC-γ1-mediated signaling pathway. In this study, we developed a single chain antibody fragment (scFv) as a blocker for PLC-γ1 mediated signaling. scFv, designated F7-scFv, specifically bound to PLC-γ1 with high affinity (Kd=1.9×10-8 M) in vitro. F7-scFv also bound to PLC-γ1 in vivo and altered the distribution pattern of PLC-γ1 from the cytoplasm to the intracellular aggregates, where F7-scFv was localized. Moreover, F7-scFv interrupted the EGF-induced translocation of PLC-γ1 from the cytosol to the membrane ruffle and attenuated EGF-induced inositol phosphates generation and intracellular calcium mobilization. These results indicate that F7-scFv blocks EGF-induced PLC-γ1 activation by causing sequestering of PLC-γ1 into intracellular aggregates, and may therefore be useful in studies of the PLC-γ1-mediated signaling pathway.