The intracellular signal transduction of AngII (angiotensin II) has been implicated in cardiovascular diseases, such as hypertension, atherosclerosis and restenosis after injury. AT(1) receptor (AngII type-1 receptor), a G-protein-coupled receptor, mediates most of the physiological and pathophysiological actions of AngII, and this receptor is predominantly expressed in cardiovascular cells, such as VSMCs (vascular smooth muscle cells). AngII activates various signalling molecules, including G-protein-derived second messengers, protein kinases and small G-proteins (Ras, Rho, Rac etc), through the AT(1) receptor leading to vascular remodelling. Growth factor receptors, such as EGFR (epidermal growth factor receptor), have been demonstrated to be 'trans'-activated by the AT(1) receptor in VSMCs to mediate growth and migration. Rho and its effector Rho-kinase/ROCK are also implicated in the pathological cellular actions of AngII in VSMCs. Less is known about the endothelial AngII signalling; however, recent studies suggest the endothelial AngII signalling positively, as well as negatively, regulates the NO (nitric oxide) signalling pathway and, thereby, modulates endothelial dysfunction. Moreover, selective AT(1)-receptor-interacting proteins have recently been identified that potentially regulate AngII signal transduction and their pathogenic functions in the target organs. In this review, we focus our discussion on the recent findings and concepts that suggest the existence of the above-mentioned novel signalling mechanisms whereby AngII mediates the formation of cardiovascular diseases.

Ang II requires EGFR to mediate ERK activation in VSMCs and the heart. EGFR plays a critical role in the LVH induced by Ang II.

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Background-Rho and its effector Rho-kinase/ROCK mediate cytoskeletal reorganization as well as smooth muscle contraction. Recent studies indicate that Rho and ROCK are critically involved in vascular remodeling. Here, we tested the hypothesis that Rho/ROCK are critically involved in angiotensin II (Ang II)-induced migration of vascular smooth muscle cells (VSMCs) by mediating a specific signal cross-talk. Methods and Results-Immunoblotting demonstrated that Ang II stimulated phosphorylation of a ROCK substrate, regulatory myosin phosphatase targeting subunit (MYPT)-1. Phosphorylation of MYPT-1 as well as migration of VSMCs induced by Ang II was inhibited by dominant-negative Rho (dnRho) or ROCK inhibitor, Y27632. Ang II-induced c-Jun NH 2 -terminal kinase (JNK) activation, but extracellular signal-regulated kinase (ERK) activation was not mediated through Rho/ROCK. Thus, infection of adenovirus encoding dnJNK inhibited VSMC migration by Ang II. We have further demonstrated that the Rho/ROCK activation by Ang II requires protein kinase C-␦ (PKC␦) and proline-rich tyrosine kinase 2 (PYK2) activation, but not epidermal growth factor receptor transactivation. Also, VSMCs express PDZ-Rho guanine nucleotide exchange factor (GEF) and Ang II stimulated PYK2 association with tyrosine phosphorylated PDZ-RhoGEF. A ngiotensin II (Ang II) has been implicated in various cardiovascular diseases such as hypertension, atherosclerosis, and restenosis after angioplasty. 1 Therefore, there has been considerable interest in defining the functional significance of signaling pathways of the Ang II type 1 receptor (AT 1 ), which is dominantly expressed in vascular smooth muscle cells (VSMCs). 1-3 Through this receptor, Ang II stimulates hypertrophy and hyperplasia of VSMCs. 2 The AT 1 receptor primarily couples to G q leading to elevation of intracellular Ca 2ϩ and activation of protein kinase C (PKC). 2 In addition, tyrosine kinase activation by Ang II is linked to downstream mitogenactivated protein kinase (MAPK) activation, thereby mediating the growth promoting response in VSMCs. 2,4,5 In this regard, several key tyrosine kinases have been identified that may contribute to the growth-promoting effects of the AT 1 receptor. These kinases include epidermal growth factor receptor (EGFR) and proline-rich tyrosine kinse 2 (PYK2). 4,5 In addition to its growth responses, VSMC migration by Ang II is strongly implicated in various cardiovascular diseases, 6 whereas the detailed signaling mechanisms by which the AT 1 receptor mediates migration are insufficiently characterized. At least, a MAPK, ERK appears to be required for Ang II-induced migration of VSMCs. 7 Recently, Zahn et al showed that 3 major MAPKs, ERK, p38MAPK, and c-Jun NH 2 -terminal kinase (JNK), are all required for VSMC migration induced by platelet-derived growth factor (PDGF), 8 suggesting that these MAPKs coordinately mediate VSMC migration. A small G protein, Rho, and its effector Rho-kinase/ ROCK, are involved in many aspects of cell motility, from smooth muscle...