PLD2 Enhances EGF Response in EL4 Lymphoma Cells

Abstract

Phospholipase D2 (PLD2) catalyzes the hydrolysis of phosphatidylcholine to yield phosphatidic acid (PA), a putative lipid second messenger. PLD2 is postulated to play a role in enhancing tumorigenesis. The epidermal growth factor receptor (EGFR) has been shown to interact with and activate PLD2. EL4 cells, derived from a murine lymphoma, present a unique model in which to elucidate the role of PLD2 in signal transduction, since they lack endogenous PLD2 mRNA and protein. In order to further elucidate PLD2-mediated signal transduction, HA-tagged PLD2 constructs were stably transfected into EL4-V7 cells. In the current study, we asked whether the EGFR might play a role in PLD2-mediated effects. Western blotting and RT-PCR were used to establish that both parental cells and PLD2 transfectants express endogenous EGFR. Levels of EGFR protein are increased in cells expressing active PLD2, as compared to parental cells or cells expressing inactive PLD2. EGF stimulates proliferation of EL4 cells transfected with active PLD2, but not in parental cells or cells transfected with inactive PLD2. EGF-mediated proliferation in cells expressing active PLD2 is modulated by the PI3K/Akt pathway, and not by the Erk MAPK pathway. PLD2 enhances EGF-induced invasion through Matrigel of cells expressing active PLD2, as compared to parental cells or cells expressing inactive PLD2. Taken together, the data suggest that PLD2 may act in concert with EGFR to enhance mitogenesis and invasion in lymphoma cells. (Supported by NIH CA094144-01)