[PP.35.01] ATRAP, A NOVEL INTERACTING MOLECULE WITH AT1 RECEPTOR, INHIBITS ANG II INDUCED PROLIFERATIVE ACTIVITY AND OXIDATIVE STRESS IN RAT SMOOTH MUSCLE CELLS

Objective: Ang II influenses the structure and function of vascular smooth muscle cells, and plays an important role in reactive oxygen species production. Superoxide anions are recognized as mediators of intracellular signaling cascades and are known to participate in cardiovascular diseases such as arteriosclerosis and hypertension. Previous studies reported that the production of superoxide is modulated by many factors including Ang II - AT1 receptor signaling. One of the major sources of superoxide in the aorta is NADPH oxidase located in the smooth muscle cells. The NADPH oxidase complex consists of p22phox, Rac1, and Nox1 etc. With respect to AT1 receptor signaling, the carboxy-terminal cytoplasmic domain of AT1 receptor is involved in the control of receptor internalization and in linking receptor-mediated signal transduction to the specific biological response. We cloned a novel molecule interacting with carboxy-terminal domain of AT1 receptor, which we named ATRAP (for AT1 receptor-associated protein), using the yeast two-hybrid strategy. In this study, we tested the hypothesis that vascular smooth muscle cells express ATRAP and that ATRAP attenuates Ang II-induced proliferative activity and oxidative stress in vascular smooth muscle cells. Design and method: We used rat smooth muscle cells and used adenoviral gene transfer for ATRAP overexpression. We used real time PCR,ELISA of TGF-ß,p22phox,Rac1,Nox1 and BrdU incorporation assay for cell proliferation. Results: We identified that the ATRAP mRNA and protein were endogeneously expressed in VSMC, and found a colocalization of ATRAP and AT1 receptor in Ang II-stimulated VSMC. The results of gain-of-function studies by adenoviral gene transfer demonstrated that overexpression of ATRAP significantly inhibited Ang II-mediated increases in c-fos gene transcription, BrdU incorpoaration, and mRNAs expression of NADPH oxidase complex (p < 0.05, n = 6). Conclusions: These results indicate that ATRAP significantly attenuates Ang II-mediated proliferative activity and oxidative stress in vascular smooth muscle cells, and suggests a novel strategy to inhibit cardiovascular disease such as arteriosclerosis and hypertension.