Angiotensin AT1 Receptor-associated protein Arap1 in the Kidney Vasculature is Suppressed by Angiotensin II

Arap1 is a protein that interacts with angiotensin II type 1 (AT1) receptors and facilitates increased AT1 receptor surface expression in vitro. In the present study we assessed the tissue localization and regulation of Arap1 in vivo. Arap1 was found in various mouse organs with highest expression in the heart, kidney, aorta, and adrenal gland. Renal Arap1 protein was restricted to the vasculature and to glomerular mesangial cells and was absent from tubular epithelia. A similar localization was found in human kidneys. To test the hypothesis that angiotensin II may control renal Arap1 expression, mice were subjected to various conditions to alter the activity of the RAS. A high salt diet (4% NaCl, 7d) upregulated Arap1 expression in mice by 47% compared to controls (0.6% NaCl, p=.03). Renal artery stenosis (7 d) or water restriction (48 hrs), suppressed Arap1 levels compared to controls (-64% and -62% in the clipped and contralateral kidney, respectively; and - 50% after water restriction; p