PLD1b in IIC9 fibroblasts is selectively activated in the nucleus and not in the Golgi apparatus

Mitogen-induced activation of a nuclear-acting PC-phospholipase D (PLD) is mediated, at least in part, by the translocation of RhoA to the nucleus. A remaining question is whether PLD in all subcellular compartments is regulated in the same manner. To address this question, we identified PLD in another subcellular compartment and determined whether its activity was influenced by α-thrombin in a RhoA-dependent manner. The data in this manuscript show that nuclear PLD is selectively regulated. α-Thrombin stimulates an increase in PLD activity in IIC9 fibroblast nuclei while Golgi PLD activity is unaffected. We cloned PLD1 from IIC9s (hamPLD1b) to show that it is present in both nuclei and Golgi. Interestingly, only nuclear PLD1 is modulated by α-thrombin, demonstrating that this activity is selectively regulated. These data provide support for the physiological importance of agonist-induced nuclear signalling enzymes.