title: Involvement of Ral GTPase in v-Src-induced phospholipase D activation.
abstract: An early response to the tyrosine kinase activity of v-Src is an increase in phospholipase D (PLD) activity, which leads to the generation of biologically active lipid second messengers, including phosphatidic acid, lysophosphatidic acid and diacylglycerol. We have recently demonstrated that v-Src-induced PLD activity is mediated by Ras, although Ras involvement was indirect, requiring a cytosolic factor for PLD activation. Ras interacts with and activates Ral-GDS, the exchange factor responsible for the activation of Ral GTPases. Here we report that this newly identified Ras/Ral signalling pathway mediates PLD activation by v-Src. PLD activity could be precipitated from v-Src-transformed cell lysates with immobilized RalA protein and with an anti-Ral antibody. A mutation to the region of RalA analogous to the 'effector domain' of Ras did not reduce the ability of RalA to complex with PLD, although deletion of a Ral-specific amino-terminal region did. Overexpression of RalA potentiated PLD activation by v-Src, and expression of dominant negative RalA mutants inhibited both v-Src- and v-Ras-induced PLD activity. Thus RalA is involved in the tyrosine kinase activation of PLD through its unique N terminus, and that PLD is a downstream target of a Ras/Ral GTPase cascade.
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002461:Cell Line, Transformed; D004789:Enzyme Activation; D004800:Enzymes, Immobilized; D020558:GTP Phosphohydrolases / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D009154:Mutation; D015688:Oncogene Protein pp60(v-src) / Q000378:metabolism*; D010739:Phospholipase D / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D020725:ral GTP-Binding Proteins; D018631:ras Proteins / Q000378:metabolism
chemical_list: D004800:Enzymes, Immobilized; D011993:Recombinant Fusion Proteins; D015688:Oncogene Protein pp60(v-src); D010739:Phospholipase D; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D020725:ral GTP-Binding Proteins; D018631:ras Proteins