Atherosclerosis remains a leading cause of death in the United States. Accumulating evidence suggests that aortic wall smooth muscle cell gene expression contributes substantially to atherogenesis. -arrestin2 (arr2) an endocytic and signaling adaptor for G protein-coupled receptors (GPCRs), growth factor receptors and ion- channels is also known to promote neointimal hyperplasia and atherosclerosis in mice. Reversible arr2 ubiquitination, as regulated by deubiquitinases (DUBs) is a critical post-translational modification that is required for arr2's adaptor functions in mediating cell-signaling. Our Preliminary Studies suggests that the DUB USP20 might affect arr2 ubiquitination as well as NF?B signaling induced by the atherogenic Toll-like receptor 4 (TLR4). To delineate the role(s) of arr2 ubiquitination/deubiquitination dynamics in vivo and to evaluate whether the ubiquitination status of arr2 could engender pro-inflammatory signaling in SMCs, we have generated transgenic mice expressing USP20 or its catalytically inactive isoform (DN-USP20) under control of the SMC-specific SM22? promoter. In this model, we expect that by de-ubiquitinating arr2, USP20 would reduce arr2 activity and thereby reduce the SMC pro-atherogenic proliferation and migration that engenders neointimal hyperplasia, whereas the DN-USP20 would have reciprocal effects. By utilizing these and additional novel reagents and in vivo methods involving diet and gene-dependent atherosclerosis and in vitro techniques employing primary vascular smooth muscle cells we will test the hypotheses that USP20 in SMCs mitigates atherosclerosis through mechanisms involving deubiquitination of arr2, and/or deubiquitination of TRAF6 or TRAF2 in a manner dependent upon arr2 scaffolding by accomplishing following specific aims: (1) To determine the atheroprotective role of SMC USP20, and whether USP20's mechanism of action requires de-ubiquitination of arr2 (2) To determine whether USP20 activity regulates arr2-dependent SMC proliferation, migration and signaling triggered by inflammatory stimuli and (3) To elucidate the mechanistic basis of USP20's effects on arr2-dependent signaling.
Atherosclerosis remains a leading cause of death in the United States. In determining cellular and molecular mechanisms by which the protein USP20 protects against atherosclerosis, this project should identify gene products and molecular mechanisms that may serve as novel therapeutic targets for treating humans with atherosclerosis.