The migration of vascular smooth muscle cells (VSMCs) is an essential event during atherosclerosis and restenosis after angioplasty. Cellular migration is achieved through coordinated regulation of membrane trafficking and cytoskeletal reorganization. While many studies have focused on the regulation of cytoskeletal reorganization in VSMCs, little is known about the involvement of membrane trafficking and the coordinated regulation of cytoskeletal reorganization and membrane trafficking in the migration of these cells. Our preliminary data have suggested that Phospholipase D2 (PLD2), a member of the phospholipase D family that generates the signaling lipid phosphatidic acid (PA), plays important roles in the migration, cytoskeletal reorganization, and membrane trafficking in VSMCs. Using a combination of liposome pull-down and mass spectrometry, we also identified some new PA-binding proteins, which have revealed the novel mechanistic insights into the cellular functions of PA. Based on our findings, we propose that PLD2-generated PA coordinately regulate cytoskeletal reorganization and membrane trafficking during VSMC migration. By using some newly available reagents and a unique interdisciplinary approach including molecular and cell biology, lipid biology, and animal models, we will investigate the mechanisms by which PLD2 regulates VSMC migration in vitro, and then examine how PLD2-regulated cell migration contributes to injury-induced vascular remodeling using mouse models. Three aims are proposed. In Aim 1, we will examine the roles of PLD2 in the polarization and migration of VSMCs. In Aim 2, we will elucidate the mechanisms by which PLD2-controlled membrane trafficking regulates VSMC migration. In Aim 3, we will investigate if PLD2 regulates vascular remodeling in vivo.