Interferon-gamma induces AT(2) receptor expression in fibroblasts by Jak/STAT pathway and interferon regulatory factor-1

Tumor cell-intrinsic Piezo2 drives radioresistance by impairing CD8+ T cell stemness maintenance

Changes in mechanosensitive ion channels following radiation have seldom been linked to therapeutic sensitivity or specific factors involved in antitumor immunity. Here, in this study, we found that the mechanical force sensor, Piezo2, was significantly upregulated in tumor cells after radiation, and Piezo2 knockout in tumor cells enhanced tumor growth suppression by radiotherapy. Specifically, loss of Piezo2 in tumor cells induced their IL-15 expression via unleashing JAK2/STAT1/IRF-1 axis after radiation. This increase in IL-15 activates IL-15Rα on tumor-infiltrating CD8+ T cells, thereby leading to their augmented effector and stem cell-like properties, along with reduced terminal exhausted feature. Importantly, Piezo2 expression was negatively correlated with CD8 infiltration, as well as with radiosensitivity of patients with rectum adenocarcinoma receiving radiotherapy treatment. Together, our findings reveal that tumor cell-intrinsic Piezo2 induces radioresistance by dampening the IRF-1/IL-15 axis, thus leading to impaired CD8+ T cell-dependent antitumor responses, providing insights into the further development of combination strategies to treat radioresistant cancers.

GETV nsP2 plays a critical role in the interferon antagonism and viral pathogenesis

Getah virus (GETV) was becoming more serious and posing a potential threat to animal safety and public health. Currently, there is limited comprehension regarding the pathogenesis and immune evasion mechanisms employed by GETV. Our study reveals that GETV infection exhibits the capacity for interferon antagonism. Specifically, the nonstructural protein nsP2 of GETV plays a crucial role in evading the host immune response. GETV nsP2 effectively inhibits the induction of IFN-β by blocking the phosphorylation and nuclear translocation of IRF3. Additionally, GETV nsP2 hinders the phosphorylation of STAT1 and its nuclear accumulation, leading to significantly impaired JAK-STAT signaling. Furthermore, the amino acids K648 and R649, situated in the C-terminal region of GETV nsP2, play a crucial role in facilitating nuclear localization. Not only do they affect the interference of nsP2 with the innate immune response, but they also exert an influence on the pathogenicity of GETV in mice. In summary, our study reveals novel mechanisms by which GETV evades the immune system, thereby offering a foundation for comprehending the pathogenic nature of GETV. Video Abstract.

ARIH1 signaling promotes anti-tumor immunity by targeting PD-L1 for proteasomal degradation

Cancer expression of PD-L1 suppresses anti-tumor immunity. PD-L1 has emerged as a remarkable therapeutic target. However, the regulation of PD-L1 degradation is not understood. Here, we identify several compounds as inducers of PD-L1 degradation using a high-throughput drug screen. We find EGFR inhibitors promote PD-L1 ubiquitination and proteasomal degradation following GSK3α-mediated phosphorylation of Ser279/Ser283. We identify ARIH1 as the E3 ubiquitin ligase responsible for targeting PD-L1 to degradation. Overexpression of ARIH1 suppresses tumor growth and promotes cytotoxic T cell activation in wild-type, but not in immunocompromised mice, highlighting the role of ARIH1 in anti-tumor immunity. Moreover, combining EGFR inhibitor ES-072 with anti-CTLA4 immunotherapy results in an additive effect on both tumor growth and cytotoxic T cell activation. Our results delineate a mechanism of PD-L1 degradation and cancer escape from immunity via EGFR-GSK3α-ARIH1 signaling and suggest GSK3α and ARIH1 might be potential drug targets to boost anti-tumor immunity and enhance immunotherapies.

Increased AT2R expression is induced by AT1R autoantibody via two axes, Klf-5/IRF-1 and circErbB4/miR-29a-5p, to promote VSMC migration

Vascular remodeling can be caused by angiotensin II type 1 receptor (AT₁R) autoantibody (AT1-AA), although the related mechanism remains unknown. Angiotensin II type 2 receptor (AT₂R) plays multiple roles in vascular remodeling through cross-talk with AT₁R in the cytoplasm. Here, we aimed to explore the role and mechanism of AT₂R in AT1-AA-induced vascular smooth muscle cell (VSMC) migration, which is a key event in vascular remodeling. In vitro and in vivo, we found that AT₂R can promote VSMC migration in AT1-AA-induced vascular remodeling. Moreover, AT₂R expression was upregulated via Klf-5/IRF-1-mediated transcriptional and circErbB4/miR-29a-5p-mediated posttranscriptional mechanisms in response to AT1-AA. Our data provide a molecular basis for AT1-AA-induced AT₂R expression by transcription factors, namely, a circular RNA and a microRNA, and showed that AT₂R participated in AT1-AA-induced VSMC migration during the development of vascular remodeling. AT₂R may be a potential target for the treatment of AT1-AA-induced vascular diseases.

Deletion of interferon-regulatory factor-1 results in cognitive impairment

Interferon-regulatory factor (IRF)-1-dependent genes in neurons play a role in ischemic neuronal death; however, the roles of IRF-1 in dementia are not well investigated. Therefore, we assessed the effect of IRF-1 on cognitive function using a vascular cognitive impairment mouse model created by chronic cerebral hypoperfusion. Male 10-week-old C57BL/6 (wild-type; WT) and IRF-1-knockout (IRF-1KO) mice were used in this study. A chronic cerebral hypoperfusion mouse model was generated by bilateral common carotid artery stenosis (BCAS) treatment. After 6 weeks of BCAS, the mice were subjected to the Morris water maze test five times a day for 5 days. In the Morris water maze task, escape latency was significantly prolonged in sham-operated IRF-1KO mice compared with sham-operated WT mice. However, BCAS treatment cancelled such difference in spatial learning between WT and IRF-1KO mice. BCAS treatment decreased CBF, but no significant difference was observed between the two strains after BCAS. Sham-operated IRF-1KO mice showed a decrease in mRNA expression of caspase-1 and an increase in IRF-2 expression in the hippocampus. Expression of angiotensin II type 2 (AT₂) receptor, which induces better cognitive function, is regulated by IRF-1; however, no obvious difference in AT₂ receptor expression was observed between the two strains even after BCAS. These results suggest that IRF-1 has a protective effect on cognitive decline in a normal condition; however, there was no obvious effect on cognition after chronic cerebral hypoperfusion treatment.

Reprogramming Interferon Regulatory Factor Signaling in Cardiometabolic Diseases

Interferon regulatory factors (IRFs) are evolutionarily conserved proteins expressed not only in immune cells but also in other tissues and organs outside the immune system. In this review, we discuss mechanisms responsible for IRF-mediated innate immune responses and the function and mechanism of IRFs in cardiometabolic diseases. We focus on the role of IRFs in innate immunity and cardiometabolic homeostasis, and highlight reprogrammed IRF signaling.

Experimental Study of Antiatherosclerosis Effects with Hederagenin in Rats

The research tries to establish Wistar rat's model of atherosclerosis for evaluating the antiatherosclerotic effect of hederagenin and exploring its antiatherosclerosis-related mechanisms. The statistical data have shown that hederagenin exhibits multiple pharmacological activities in the treatment of hyperlipidemia, antiplatelet aggregation, liver protection, and anti-inflammation, indicating that hederagenin may exert a protective effect on vascular walls by improving lipid metabolism disorders and lipid deposition. The results show that hederagenin can correct the imbalance of endothelial function by inhibiting the release of large amounts of iNOS and increasing eNOS contents and inhibits the IKKβ/NF-κB signaling pathway to reduce the release of IL-6, IFN-γ, TNF-α, and other inflammatory factors. The experimental results indicated that hederagenin can inhibit or ameliorate the pathological changes associated with AS, displaying an excellent preventive function against AS.

The interferon regulatory factors as novel potential targets in the treatment of cardiovascular diseases

The family of interferon regulatory factors (IRFs) consists of nine members (IRF1-IRF9) in mammals. They act as transcription factors for the interferons and thus exert essential regulatory functions in the immune system and in oncogenesis. Recent clinical and experimental studies have identified critically important roles of the IRFs in cardiovascular diseases, arising from their participation in divergent and overlapping molecular programmes beyond the immune response. Here we review the current knowledge of the regulatory effects and mechanisms of IRFs on the immune system. The role of IRFs and their potential molecular mechanisms as novel stress sensors and mediators of cardiovascular diseases are highlighted.

JAK-STAT and the renin-angiotensin system: The role of the JAK-STAT pathway in blood pressure and intrarenal renin-angiotensin system regulation

The renin-angiotensin system (RAS) plays important roles in blood pressure control and tissue disease. An inappropriate local angiotensin II elevation in the kidneys leads to the development of hypertension, tissue damage and chronic injury. Studies have demonstrated that the JAK-STAT pathway mediates angiotensin II-triggered gene transcription. The JAK-STAT pathway in turn, acting as an amplifying system, contributes to further intrarenal RAS activation. These observations prompt the suggestion that the JAK-STAT pathway may be of importance in elucidating the mechanisms RAS-associated tissue injury. Accordingly, this review provides a brief overview of the interactions between the JAK-STAT pathway and the RAS, specifically the RAS expressed in the kidneys.

Interferon regulatory factor-1 exerts inhibitory effect on neointimal formation after vascular injury

OBJECTIVE

To investigate the effect of interferon regulatory factors (IRFs) on neointimal formation after vascular injury in the mouse, and its possible mechanism.

METHODS

Vascular injury was induced by polyethylene cuff placement around the left femoral artery of IRF-1-deficient mice and C57BL/6J mice. The mRNA expressions of IRF-1, IRF-2, angiotensin II type 2 (AT2) receptor, interleukin-1 beta converting enzyme (ICE), inducible nitric oxide synthase (iNOS) were detected by RT-PCR and immunohistochemical staining.

RESULTS

Neointimal formation after vascular injury was significantly greater in IRF-1-deficient mice than that in C57BL/6J mice (P<0.05). In contrast, TUNEL-positive nuclei to total nuclei in the neointima and media in vascular smooth muscle cell (VSMC) in the injured artery significantly attenuated in IRF-1-deficient mice compared to C57BL/6J mice (P<0.05). The expressions of AT2 receptor as well as pro-apoptotic genes such as ICE and iNOS in C57BL/6J mice were up-regulated in response to vascular injury, but this upregulation was attenuated in IRF-1-deficient mice.

CONCLUSIONS

Our results suggest that IRF-1 induces VSMC apoptosis and inhibits neointimal formation after vascular injury at least partly due to the upregulation of AT2 receptor, ICE and iNOS expressions. These results indicate that IRF-1 exerts an inhibitory effect on neointimal formation through the induction of apoptosis in VSMCs.

Pravastatin attenuates interferon-gamma action via modulation of STAT1 to prevent aortic atherosclerosis in apolipoprotein E-knockout mice

1. The beneficial effects of pravastatin, beyond that of lowering cholesterol in atherosclerosis, include reducing the action of interferon (IFN)-gamma. Interferon-gamma activates the signal transducer and activator of transcription 1 (STAT1), but it is unclear whether the inhibitory effect of pravastatin in atherosclerosis is via modulation of the IFN-gamma/STAT1 pathway. Thus, the aim of the present study was to determine whether the action of pravastatin in preventing aortic atherosclerosis by attenuation of IFN-gamma action is dependent on STAT1. 2. Male apolipoprotein E-knockout (apoE(-/-)) mice were fed a diet containing 1.25% cholesterol (w/w). Mice were divided into two groups, one of which was supplemented with pravastatin (80 mg/kg per day). Male C57BL/6J mice were fed a normal diet and served as the control group (n = 12 per group). 3. Atherosclerotic lesions in the aortic root were assessed by staining sections haematoxylin and eosin. Serum concentrations of IFN-gamma and IFN-gamma mRNA expression in the thoracoabdominal aorta were determined by ELISA and real-time quantitative polymerase chain reaction methods, respectively. Expression of phosphorylated STAT1 (pSTAT1), interferon regulating factor (IRF)-1 and suppressors of cytokine signalling 1 (SOCS1) was determined in the thoracoabdominal aorta using Western blot analysis. 4. After 8 weeks, pravastatin treatment significantly prevented the formation of atherosclerotic lesions (P < 0.05) and reduced serum IFN-gamma concentrations (P < 0.05) and levels of IFN-gamma mRNA within the aorta (P < 0.01). Pravastatin significantly decreased the expressions of pSTAT1 and IRF-1 within the aorta and significantly increased expression of SOCS1. 5. These results suggest that the actions of pravastatin in attenuating the action of IFN-gamma and subsequently preventing aortic atherosclerosis may depend, at least in part, on modulation of STAT1 activity. This providing us with a new therapeutic approach and a clearer insight into the clinical benefits of pravastatin.

Angiotensin type 2 receptor is expressed in human atherosclerotic lesions

Objective. Expression of the angiotensin type 2 receptor (AT2-receptor) occurs in many animal models of atherosclerosis. However, its expression in human plaques and its functional role remains undetermined.This study examined AT2-receptor expression in human atherosclerotic plaque and also explored its potentially important functional role in atherosclerosis.

Material and methods. We analysed carotid atherosclerotic plaques obtained from 14 Caucasian patients who had previously carotid artery stenosis. Half of all subjects undergone endarterectomy for symptomatic carotid artery stenosis. Half of all subjects received treatment with an angiotensin receptor blocker (ARB) (n=7); the remaining subjects received no intervention in the renin-angiotensin system (n=7). Immunohistochemistry measured tissue expression of smooth muscle cells (α-actin), macrophages (CD68 antibody), collagen (picro-sirius), and AT2-receptor (AT2-receptor antibody).

Results. AT2-receptor expression occurred consistently in all specimens. Although cellular localisation varied, AT2-receptor expression levels correlated with macrophage levels (p<0.01). Compared to conventional treatment, ongoing ARB treatment affected neither AT2-receptor levels nor plaque composition.

Conclusions. AT2-receptor is expressed in human atherosclerotic plaque. Furthermore, we detected no functionally important role of AT2-receptor expression and found no evidence that ARB treatment regulates AT2-receptor expression.

Regulation of Inhibitory Protein-κB and Monocyte Chemoattractant Protein-1 by Angiotensin II Type 2 Receptor-Activated Src Homology Protein Tyrosine Phosphatase-1 in Fetal Vascular Smooth Muscle Cells

In the present study we examined the effects of angiotensin II (Ang II) type 2 (AT(2)) receptor stimulation on AT(1) receptor-mediated monocyte chemoattractant protein-1 (MCP-1) expression and the possible mechanisms of AT(2) receptor-mediated signaling in cultured rat fetal vascular smooth muscle cells, which express both AT(1) and AT(2) receptors. Ang II stimulation induced MCP-1 mRNA expression as well as an increase in nuclear factor-kappaB (NF-kappaB) binding to the corresponding cis DNA element of the MCP-1 promoter region and a decrease in the cytosolic inhibitory protein-kappaB (IkappaB) protein level via AT(1) receptor stimulation, whereas stimulation of the AT(2) receptor decreased Ang II-induced MCP-1 expression, NF-kappaB DNA binding, and IkappaB degradation, suggesting that activation of the AT(2) receptor attenuated AT(1) receptor-mediated MCP-1 expression via a decrease in NF-kappaB DNA binding and an increase in IkappaB stability. Moreover, we demonstrated that AT(2) receptor stimulation attenuated TNFalpha-mediated NF-kappaB activation and MCP-1 expression. A tyrosine phosphatase inhibitor, orthovanadate, attenuated the AT(2) receptor-mediated increase in IkappaB protein. Moreover, we observed that two IkappaB subunits (IkappaBalpha and IkappaBbeta) were tyrosine-phosphorylated after Ang II stimulation. Transfection of a dominant-negative Src homology protein tyrosine phosphatase-1 mutant into vascular smooth muscle cells inhibited the AT(2) receptor-mediated increase in IkappaB, leading to a significant increase in AT(1) receptor-induced NF-kappaB activation and MCP-1 expression. Taken together, our results demonstrated that AT(2) receptor stimulation attenuated MCP-1 expression via IkappaB stabilization, and Src homology protein tyrosine phosphatase-1 might play a critical role in the transcriptional regulation of MCP-1 expression through the control of IkappaB protein stability.

Interferons in enteroviral heart disease: modulation of cytokine expression and antiviral activity

Interferon (IFN)-beta has a more than 120-fold higher antiviral activity than the closely related IFN-alpha in human myocardial fibroblasts infected with the cardiotropic enterovirus coxsackievirus B3 (CVB3). CVB3 replication induces interleukin (IL)-6 and IL-8 expression in myocardial fibroblasts, and suppresses the expression of monocyte chemoattractant protein-1 (MCP-1). We investigated whether the higher antiviral activity of IFN-beta compared to IFN-alpha was a result of a suppression of IL-8 expression by IFN-beta since previous studies had indicated that IL-8 stimulates enterovirus replication. Human myocardial fibroblasts were treated with either IFN-alpha, IFN-beta or IFN-gamma (0, 10, 100, or 1,000 IU/ml) and the concentrations of IL-6, IL-8 and MCP-1 were measured in culture supernatants by immunoassays. Both IFN-beta and IFN-gamma reduced IL-6 and IL-8 expression significantly. In addition, neutralization of IL-8 in culture supernatants of myocardial fibroblasts using a monoclonal antibody demonstrated a significant reduction of CVB3 titers. Antiproliferative effects of all three IFNs were very low (<30% with 1,000 IU/ml), indicating that the suppression IL-6 and IL-8 was not related to cytotoxicity. MCP-1 expression was increased only by high concentrations of IFN-gamma (1,000 IU/ml). By contrast, IFN-alpha had no significant effect on IL-6, IL-8 and MCP-1 expression. In conclusion, suppression of IL-8 expression is an "immuno-modulating" feature of IFN-beta in human myocardial fibroblasts, which is similar to the activity of IFN-gamma. This feature of IFN-beta contributes to its high antiviral activity against CVB3 and may be useful in the treatment of enteroviral heart disease.

Cytokine-mediated downregulation of vasopressin V(1A) receptors during acute endotoxemia in rats

The reduced pressure response to vasopressin during acute sepsis has directed our interest to the regulation of vasopressin V(1A) receptors. Rats were injected with lipopolysaccharide for induction of experimental gram-negative sepsis. V(1A) receptor gene expression was downregulated in the liver, lung, kidney, and heart during endotoxemia. Inasmuch as the concentrations of proinflammatory cytokines such as interleukin-1beta, tumor necrosis factor-alpha, and interferon-gamma were highly increased during sepsis, the influence of these cytokines on V(1A) receptor expression was investigated in primary cultures of hepatocytes and in the aortic vascular smooth muscle cell line A7r5. V(1A) receptor expression was downregulated by the cytokines in a nitric oxide-independent manner. Blood pressure dose-response studies after injection of endotoxin showed a diminished responsiveness to the selective V(1) receptor agonist Phe(2),Ile(3),Orn(8)-vasopressin. Our data show that sepsis causes a downregulation of V(1A) receptors and suggest that this effect is likely mediated by proinflammatory cytokines. We propose that this downregulation of V(1A) receptors contributes to the attenuated responsiveness of blood pressure in response to vasopressin and, therefore, contributes to the circulatory failure in septic shock.

Expression and role of angiotensin II type 2 receptor in the kidney and mesangial cells of spontaneously hypertensive rats

Angiotensin II type 2 (AT2) receptor is developmentally regulated and exerts antiproliferative and proapoptotic actions. Genetic ablation of this receptor in mice affects regulation of blood pressure, but the involvement of the AT2 receptor in the pathogenesis of hypertension remains unknown. In the present study, we examined developmental changes of angiotensin receptor subtypes in the kidney of stroke-prone spontaneously hypertensive rats (SHRSP), and compared them with those in normotensive Wistar-Kyoto rats (WKY). We also investigated the regulation and functional role of the AT2 receptor in cultured mesangial cells. Receptor binding and Northern blot analyses revealed that AT2 receptor expression is significantly lower in the SHRSP kidney than in the WKY kidney during the perinatal period, while AT1 receptor expression is not different between them. In WKY mesangial cells, AT2 receptor stimulation exerted a potent antiproliferative effect; this effect was not observed in SHRSP cells lacking the AT2 receptor expression. The expression of interferon regulatory factor (IRF)-1 paralleled the growth-dependent induction of AT2 receptor in WKY mesangial cells, and transfection of IRF-1 antisense oligonucleotide significantly suppressed AT2 receptor expression, indicating IRF-1-dependent regulation of AT2 receptor expression in mesangial cells. However, this induction was inefficient in SHRSP cells. Thus, we found impaired AT2 receptor expression in the SHRSP kidney in vivo and in mesangial cells in vitro. The unbalanced expression of renal angiotensin receptor subtypes with exaggerated AT1 receptor signaling during early life in SHRSP may play a role in the programming for hypertension and related renal injury.

Nitric oxide-dependent down-regulation of angiotensin II type 2 receptors during experimental sepsis

OBJECTIVE

The systemic renin-angiotensin system is highly activated during septic shock. This has focused interest in regulation of the adrenal angiotensin II type 2 receptor (AT2) as the target thought to mediate angiotensin II-induced adrenal catecholamine release during experimental sepsis in vivo. In addition, the influence of typical endogenous mediators of sepsis, such as proinflammatory cytokines and nitric oxide, on AT2 receptor expression should be investigated in vitro.

DESIGN

Prospective animal trial followed by a controlled cell culture study.

SETTING

Laboratory of the Department of Anesthesiology.

SUBJECTS

Male Sprague-Dawley rats weighing 200-250 g, PC12 cell line.

INTERVENTIONS

Rats were injected with lipopolysaccharide to stimulate Gram-negative sepsis or lipoteichoic acid to stimulate Gram-positive sepsis. AT2 receptor expression, abundance of the proinflammatory cytokines (interleukin-1beta, tumor necrosis factor-alpha, and interferon-gamma), and nitric oxide synthase II expression have been determined in the adrenal gland. Rat adrenal pheochromocytoma cells were incubated with these cytokines or with the nitric oxide donors sodium nitroprusside or S-nitroso-N-acetylpenicillamine to investigate the regulation of AT2 receptors during severe inflammation on a cellular level.

MEASUREMENTS AND MAIN RESULTS

In the adrenal gland, AT2 receptor expression was down-regulated in both models of sepsis, whereas tissue cytokine concentrations were elevated and nitric oxide synthase II expression was induced. Incubation of PC12 cells with proinflammatory cytokines resulted in a dose-dependent diminished expression of AT2 receptors, which was mimicked by incubation with nitric oxide donors. Blocking of cytokine-induced nitric oxide synthesis by co-incubation of PC12 cells with NG-nitro-l-arginine methyl ester prevented down-regulation of AT2 receptors.

CONCLUSIONS

These findings show that in our model of sepsis, the expression of AT2 receptors in the adrenal gland is down-regulated in a nitric oxide-dependent manner. Because AT2 receptors are thought to be involved in adrenal catecholamine secretion in a stimulatory fashion, the diminished expression of AT2 receptors could play an important role in the pathogenesis of septic shock via impaired angiotensin II-induced adrenal catecholamine release, despite a strong activation of the systemic renin-angiotensin system.

Characterization of human myocardial fibroblasts immortalized by HPV16 E6--E7 genes

Human myocardial fibroblasts (HMF) have proved to be useful as a species specific cell culture system in various studies on myocarditis and cardiac remodelling. However, their use is limited, since they are hard to obtain and lifespan is short due to replicative senescence. To overcome these disadvantages, we transfected primary HMF with the E6 and E7 genes of the oncogenic human papillomavirus (HPV) 16. Successful transfection was demonstrated in 3 of 12 experiments by detection of E6-E7 gene transcription with nucleic acid sequence based amplification (NASBA). No significant change of phenotype was noted in the emerging cell lines (HMF(1226D), HMF(1321D), HMF(1226K)), but their in vitro lifespan was increased by 20 to 30 population doublings until cells entered crisis. A single subclone of HMF(1226K) had a transformed phenotype and continued to proliferate indefinitely. This subclone (HMF(1226K/I)) was considered to be immortalized and telomerase activity was detected. Despite the increased risk of mutations due to abrogation of p53 function, HMF(1226K/I) and the HMF lines with an increased lifespan retained the properties of primary HMF cells, as they expressed fibroblast markers (prolyl-4-hydroxylase, vimentin), cytokines (interleukin 1 alpha, 6, 8), and angiotensin II receptors and still were permissive for coxsackievirus B3 infection.

Examination of angiotensin II type 1 and type 2 receptor expression in human kidneys by immunohistochemistry

Recent studies have suggested that both the angiotensin II type 1 (AT1) and type 2 (AT2) receptors may be involved in the control of renal function in rodents. The aim of this study was to examine the distribution of these receptors in normal and diseased human kidneys. Kidney samples were obtained from 21 patients with and without glomerular lesions (3 control kidney samples from patients undergoing nephrectomy, 4 patients with minimal change disease, 6 patients with IgA nephropathy, and 8 patients with membranous glomerulonephritis). AT1 receptor immunohistochemical staining was examined and found to be most prominent in blood vessels, but staining of the tubules and glomeruli was also seen. In the case of the AT2 receptor, mild-moderate immunohistochemical staining was seen in the blood vessels, with weaker staining in the glomeruli. A similar distribution was seen in the patients with glomerulopathy. These results suggest that both AT1 and AT2 receptors are expressed in the normal human kidney, as well as in patients with glomerular disease. The histological distribution of these receptors supports the notion that both receptors may have a physiological role in normal and diseased kidneys in humans.

ATRAP, novel AT1 receptor associated protein, enhances internalization of AT1 receptor and inhibits vascular smooth muscle cell growth

We have identified a novel, membrane-located protein that interacts specifically with the carboxyl-terminal cytoplasmic domain of the AT1a receptor, which we named ATRAP (for AT1 receptor-associated protein). To further investigate the role of ATRAP in AT1 receptor function, we examined the effect of overexpression of ATRAP on angiotensin II (Ang II)-induced AT1 receptor desensitization and/or internalization, and cell proliferation in adult vascular smooth muscle cells (VSMCs). Transfection of ATRAP potentiated AT1 receptor internalization upon Ang II stimulation in these VSMCs. Moreover, we observed that AT1 receptor-induced DNA synthesis was markedly inhibited in ATRAP transfected VSMCs associated with the inhibition of the phosphorylation of signal transducers and activators of transcription (STAT) 3 and Akt. Our results suggest that ATRAP functions as a negative regulator in AT1 receptor-mediated cell proliferation in VSMCs.