The renin-angiotensin system in the kidney plays a critical role in the regulation of renal hemodynamics and sodium handling through the activation of vascular, glomerular and tubular angiotensin II type 1 (AT1) receptor-mediated signaling. We previously cloned a molecule that specifically bound to the AT1 receptor and modulated AT1 receptor signaling in vitro, which we named ATRAP (for AT1 receptor-associated protein). The purpose of this study is to analyze the renal distribution of ATRAP and to examine whether ATRAP is co-expressed with the AT1 receptor in the mouse kidney. We performed in situ hybridization, Western blot analysis, and immunohistochemistry to investigate the expression of ATRAP mRNA and protein in the mouse kidney. The results of Western blot analysis revealed the ATRAP protein to be abundantly expressed in the kidney. Employing in situ hybridization and immunohistochemistry, we found that both ATRAP mRNA and the protein were widely distributed along the renal tubules from Bowman's capsules to the inner medullary collecting ducts. ATRAP mRNA was also detected in the glomeruli, vasculature, and interstitial cells. In all tubular cells, the ATRAP protein colocalized with the AT1 receptor. Finally, we found that the dietary salt depletion significantly decreased the renal expression of ATRAP as well as AT1 receptor. These findings show ATRAP to be abundantly and broadly distributed in nephron segments where the AT1 receptor is expressed. Furthermore, this is the first report demonstrating a substantial colocalization of ATRAP and AT1 receptor in vivo.

A close relationship between obesity and hypertension has been recognized, and plasma angiotensinogen concentrations (p-AGT) have been reported to correlate with blood pressure (BP). However, little is known about AGT in obese patients with hypertension. To define the role of AGT in obese hypertension, we measured p-AGT in obese patients. The subjects were 42 obese patients diagnosed on the basis of a body mass index (BMI) of more than 25 kg/m2, and 21 sex- and age-matched nonobese patients, whose BMI was less than 25 kg/m2. The hypertensive patients had not previously received antihypertensive drugs. P-AGT (P < .05) and mean BP (P < .0001) was increased in the obese patients as compared with the nonobese patients. Positive correlations were observed between BMI and p-AGT, mean BP and p-AGT, and BMI and mean BP (all P < .05). However, after adjustment for blood pressure, p-AGT was not different between groups, and after adjustment a positive correlation remained only between BMI and mean BP. These results suggested the possible involvement of increased p-AGT in hypertension in obese patients, although this may be a secondary change to hypertension or obesity.

Abstract-We cloned a novel molecule interacting with angiotensin II type 1 receptor, which we named ATRAP (for angiotensin II type 1 receptor-associated protein). Previous in vitro studies showed that ATRAP significantly promotes constitutive internalization of the angiotensin II type 1 receptor and further attenuates angiotensin II-mediated hypertrophic responses in cardiomyocytes. The present study was designed to investigate the putative functional role of ATRAP in cardiac hypertrophy by angiotensin II infusion in vivo. We first examined the effect of angiotensin II infusion on endogenous ATRAP expression in the heart of C57BL/6J wild-type mice. The angiotensin II treatment promoted cardiac hypertrophy, concomitant with a significant decrease in cardiac ATRAP expression, but without significant change in cardiac angiotensin II type 1 receptor expression. We hypothesized that a downregulation of the cardiac ATRAP to angiotensin II type 1 receptor ratio is involved in the pathogenesis of cardiac hypertrophy. To examine this hypothesis, we next generated transgenic mice expressing ATRAP specifically in cardiomyocytes under control of the ␣-myosin heavy chain promoter. In cardiac-specific ATRAP transgenic mice, the development of cardiac hypertrophy, activation of p38 mitogen-activated protein kinase, and expression of hypertrophy-related genes in the context of angiotensin II treatment were completely suppressed, in spite of there being no significant difference in blood pressure on radiotelemetry between the transgenic mice and littermate control mice. These results demonstrate that cardiomyocyte-specific overexpression of ATRAP in vivo abolishes the cardiac hypertrophy provoked by chronic angiotensin II infusion, thereby suggesting ATRAP to be a novel therapeutic target in cardiac hypertrophy. (Hypertension. 2010;55:1157-1164.)Key Words: basic science Ⅲ receptors Ⅲ gene expression/regulation Ⅲ hypertrophy/remodeling Ⅲ angiotensin receptors E vidence suggests that the activation of angiotensin II (Ang II) type 1 receptor (AT 1 R) through the tissue renin-angiotensin system may play an important role in the development of cardiac hypertrophy. The carboxyl-terminal portion of AT 1 R is involved in the control of AT 1 R internalization independent of G protein coupling, and it plays an important role in linking receptor-mediated signal transduction to the specific biological response to Ang II. 1,2 We previously cloned a novel AT 1 R-associated protein (ATRAP) that specifically interacts with the carboxylterminal domain of AT 1 R. [3][4][5][6] We showed that ATRAP is broadly expressed in many tissues, as is AT 1 R, and suppresses Ang II-mediated pathological responses in cardiomyocytes and vascular smooth muscle cells by promoting the constitutive internalization of AT 1 R. 7-9 However, the function of ATRAP in cardiac hypertrophy in vivo still remains to be demonstrated. Thus, the present study was carried out to investigate whether there is a role for ATRAP in the cardiac hypertrophy induced by chronic Ang II ...

The angiotensinogen (AGT) gene M235T variant is associated with essential hypertension and elevated plasma AGT concentrations, although the underlying mechanisms are unknown. Recent studies have suggested that AGCE 1 (human AGT gene core promoter element 1) located in the 5' upstream core promoter region (position -25 to -1) of the human AGT gene has an important part in the expression of AGT mRNA by binding with transcription factor AGCF 1 (human AGT gene core promoter element binding factor 1), and a mutation at -20 from adenine to cytosine (A-20C) increases the level of expression of this transcript. We therefore examined subjects with this mutation to study the association with increased plasma AGT concentrations and with essential hypertension. One hundred eighty-eight subjects receiving no antihypertensive medication were examined with regard to the correlation between A-20C and plasma AGT concentrations, and 234 subjects were studied with respect to the association between A-20C and essential hypertension. A-20C was determined by polymerase chain reaction-restriction fragment length polymorphism analysis with EcoOR 109I. Multiple regression analysis showed a weak but significant correlation between A-20C and plasma AGT concentrations (P=.047) and essential hypertension (P=.049). The results suggest that A-20C may underlie the increase in plasma AGT concentrations and be involved in the development of essential hypertension.

Angiotensinogen gene-knockout (Atg-/-) mice lacking angiotensin II exhibit chronic hypotension. The present study was designed to investigate pathophysiology of Atg-/- mice from the renal functional view. Wild-type (Atg+/+) and Atg-/- mice at 10 weeks of age were housed in metabolic cages for 24-hour urine collection. When provided free access to water, Atg-/- mice showed an increased urine output and a decreased urine osmolality compared with Atg+/+ mice. Urinary excretion and plasma levels of vasopressin were significantly higher in mutant mice than in wild-type mice. On the other hand, urinary excretion of aldosterone in mutant mice was suppressed to the levels under the detection limit of the assay system. The mean plasma aldosterone level of Atg-/- mice was suppressed to 30% of that of Atg+/+ mice. Plasma levels of creatinine, endogenous creatinine clearance, and urinary electrolyte excretion were not different between these mice. In Atg+/+ mice, urine osmolality was markedly increased from 1929 +/- 21 to 3314 +/- 402 mOsm/kg during water deprivation, whereas this parameter in Atg-/- mice did not change significantly (from 1413 +/- 121 to 1590 +/- 92 mOsm/kg). Urinary vasopressin excretion increased during water deprivation from 0.24 +/- 0.04 and 0.70 +/- 0.08 to 0.42 +/- 0.06 and 2.31 +/- 0.35 ng/mg creatinine in wild-type and mutant mice, respectively. Histologic study revealed interstitial inflammation, and atrophic changes in the tubules and papilla in Atg-/- mice. In conclusion, a genetic deficiency of angiotensinogen produced an impaired urine concentrating ability and tubulointerstitial lesions, indicating the critical role of angiotensinogen in developing normal tubular function and construction.