PROJECT SUMMARY Aortic aneurysm is a prevalent condition defined by excessive aortic growth and medial wall remodeling that can result in lethal dissection and rupture. Few effective pharmacological treatments exist for aneurysm, due in large part to an incomplete understanding of the mechanisms that underlie the disease. The goal of this proposal is to derive a more comprehensive understanding of the molecular events that belie thoracic aortic aneurysm progression, and in so doing identify and validate potential targets for novel pharmacological therapy. Preliminary in vitro and in vivo data indicate that interactions between angiotensin II, integrin, and transforming growth factor ? (TGF?) signaling are key molecular elements of aneurysm pathogenesis. The principal investigator, Dr. Sarah Parker, uses a genetic knock-in mouse model of Marfan syndrome (MFS) to study the context-dependent molecular mechanisms leading to dysregulated TGF? signaling in thoracic aortic aneurysm. In the mentored phase of this proposal, Dr. Parker will use in vitro techniques to assess how of Integrin ?3 (ITG?3) overexpression, as occurs in MFS, impacts aspects of vascular smooth muscle cell physiology known to be altered in aortic aneurysm, and use novel mass spectrometry technologies (data independent acquisition MS) to identify pathogenic signaling components downstream of ITG?3 that drive altered VSMC physiology (Aim 1). In the transition to the independent phase, Dr. Parker will identify how another signaling network, ?-Arrestin 2 (?ARR2) biased signaling by the Angiotensin II Type 1 Receptor (AT1R), contributes to dysregulated TGF? signaling and altered mechanical properties of VSMCs that occur during aneurysm in MFS (Aim 2). Finally, Dr. Parker will integrate the findings in Aims 1 and 2 to test a unifying hypothesis that altered matrix sensing by ITG?3 contributes to ?ARR2 biased signaling by AT1R both in vitro as well as in vivo in MFS mice, and further determine whether pharmacological manipulation of ITG?3 and/or ?ARR2-biased signaling can attenuate aneurysm progression in MFS (Aim 3). Dr. Parker received her Ph.D. in Physiology from the Medical College of Wisconsin (MCW). She has subsequently completed the first three and a half years of her Post Doctoral fellowship at Johns Hopkins University under the collaborative mentorship of Dr. Harry (Hal) Dietz, a renowned clinician and expert in the medical genetics of connective tissue disorders and aortic aneurysm, and Dr. Jennifer Van Eyk, a premier expert in clinical cardiovascular proteomics. Building upon her established expertise in cardiovascular physiology and mass spectrometry-based proteomic techniques, this K99/R00 award will allow Dr. Parker to (1) develop informatics and computational skills for the analysis and interpretation of complex molecular data sets, (2) in collaboration with Dr. Megan McCain at the University of Southern California, develop an in vitro model to independently modify matrix components, smooth muscle cell types, and soluble extracellular factors in order to study contractile physiology in smooth muscle cells, (3) continue to build expertise in the vascular biology of the aorta and (4) strengthen her communication, mentoring, management, and leadership skills to prepare for success as an independent biomedical researcher. Dr. Parker will complete the mentored phase of this award at Cedars-Sinai Medical Center (CSMC), where her primary mentor, Dr. Van Eyk, has recently moved her laboratory to become the director of the Advanced Clinical Biosystems Research Institute. Dr. Parker has enlisted an impressive team of mentors and advisors both local to Cedars Sinai (Dr. Jennifer Van Eyk, Dr. Moshe Arditi, Dr. Ben Berman, Dr. Ken Bernstein) and at external institutions (Dr. Hal Dietz, Dr. John Yates, and Dr. Megan McCain) to facilitate her scientific and personal development. The clinical research environments fostered by the institutions where Dr. Parker has been trained (Johns Hopkins, MCW) and will continue her training (CSMC) provide ideal settings to facilitate her long-term career goal to elucidate context-dependent, pathological signaling events in situ and connect them with the altered cellular, tissue, and organ physiology characteristic of disease pathogenesis. Dr. Parker will first focus her approach on the specific etiological mechanisms that drive ascending aortic aneurysm, and intends to eventually expand her research into other areas of cardiovascular biology where the full complexity of external and internal molecular context must be understood in order to best predict the cause-and-effect relationships between cell signaling and pathophysiology. To achieve this goal, Dr. Parker intends to bridge focused mass spectrometry-based discovery workflows with careful biological validation and the pre-clinical testing of novel therapeutic candidates that will be used to treat specific pathologies. This award will be fundamental in supporting Dr. Parker to build the framework for a research program that will achieve her career goals. Furthermore, by completing the aims of this proposal Dr. Parker will make a significant contribution toward the development of new treatments that will prevent the debilitating consequences of aortic aneurysm.