Phospholipase C-γ1 (PLC-γ1), which generates two second messengers, namely, inositol-1, 4, 5-trisphosphate and diacylglycerol, is implicated in growth factor-mediated chemotaxis. However, the exact role of PLC-γ1 in integrin-mediated cell adhesion and migration remains poorly understood. In this study, we demonstrate that PLC-γ1 is required for actin cytoskeletal organization and cell motility through the regulation of Pyk2 and paxillin activation. After fibronectin stimulation, PLC-γ1 directly interacted with the cytoplasmic tail of integrin β1. In PLC-γ1-silenced cells, integrin-induced Pyk2 and paxillin phosphorylation were significantly reduced and PLC-γ1 potentiated the integrin-induced Pyk2/paxillin activation in its enzymatic activity-dependent manner. In addition, specific knock-down of PLC-γ1 resulted in a failure to form focal adhesions dependent on fibronectin stimulation, which appeared to be caused by the suppression of Pyk2 and paxillin phosphorylation. Interestingly, PLC-γ1 potentiated the activations of Rac, thus integrin-induced lamellipodia formation was up-regulated. Consequently, the strength of cell-substratum interaction and cell motility were profoundly up-regulated by PLC-γ1. Taken together, these results suggest that PLC-γ1 is a key player in integrin-mediated cell spreading and motility achieved by the activation of Pyk2/paxillin/Rac signaling. © 2007 Elsevier Inc. All rights reserved.
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