Identification and Characterization of the Interaction between Heat-Shock Protein 90 and Phospholipase C-γ1

Phosphoinositide-specific phospholipase C-γ1 (PLC-γ1) is a pivotal mediator in the signal transduction cascades induced by many growth factors. Using a yeast two-hybrid system, heat-shock protein 90 (Hsp90) was identified as a PLC-γ1-binding protein. A co-immunoprecipitation experiment, using anti-PLC-γ1 antibody, demonstrated an in vivo interaction between Hsp90 and PLC-γ1 in the NIH-3T3 cells. The interaction in NIH-3T3 was unaffected by the PDGF treatment, inducing phosphorylation and activation of PLC- γ1. Direct interaction between Hsp90 and PLC-γ1 was confirmed by in vitro binding experiments using purified Hsp90 and PLC-γ1. Furthermore, Hsp90 increased the PIP₂-hydrolyzing activity of PLC-γ1 up to 2-fold at 0.1μM in vitro. Taken together, we show for the first time, the interaction of PLC-γ1 with Hsp90, both in vivo and in vitro. We suggest that Hsp90 may play a role in PLC-γ1-mediated signal transduction.