Hypertension is a major risk factor for myocardial infarction, heart failure, and stroke. The renin-angiotensin system (RAS), an important modulator of blood pressure and cardiovascular physiology, plays a critical role in the etiology of hypertension and the pathophysiology of cardiac, renal and vascular diseases. The octapeptide angiotensin II is the principal terminal component of the RAS and its pressor/vasoactive effects are mediated through activation of the angiotensin type 1 cellular receptor (AT1R). Multiple components of the RAS are targets of current anti-hypertensive drugs. Understanding the mechanisms, physiological significance, and complex interplays of the circulating, tissue, and intracellular RAS components is vital to further, effective drug development. Initial studies were designed to identify proteins which bind to the cytoplasmic carboxy-terminus of AT1R. Such proteins are expected to be involved in intracellular trafficking of AT1R, as well as in ligand-mediated internalization, recycling and signal transduction. Using a yeast-two hybrid approach, we identified several proteins which bind to the AT1R, the most prevalent of which are GABARAP and the related protein, GABARAPL1. GABARAP, originally identified through its binding to the GABAA receptor, is involved in trafficking of the GABAA receptor to the plasma membrane. Because of the importance of trafficking proteins for determining steady-state plasma membrane levels of receptors, we have investigated and confirmed the presumptive interaction between AT1R and GABARAP. In addition, we have obtained initial evidence indicating that this interaction is instrumental in regulating the plasma membrane level, and subsequent ligand-mediated activities, of AT1R. Our broad, working hypothesis is that GABARAP directly interacts with AT1R to promote cellular trafficking of the receptor to the plasma membrane. Trafficking is an area of AT1R biology that is poorly understood but one that appears to be a logical candidate for therapeutic manipulation, especially given our additional preliminary findings that gabarap-/- mice exhibit reduced blood pressure compared to wild-type mice. The objectives of the proposed research program is to characterize the interaction between AT1R and GABARAP, determine the mechanism by which GABARAP regulates trafficking of AT1R to the plasma membrane, and explore the importance of this interaction in blood pressure modulation.
|Effective start/end date||07/01/2010 → 06/30/2012|