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Identification of membrane-bound variant of metalloendopeptidase neurolysin (EC 3.4.24.16) as the non-angiotensin type 1 (non-AT1), non-AT2 angiotensin binding site.

ABSTRACT: Recently, we discovered a novel non-angiotensin type 1 (non-AT1), non-AT2 angiotensin binding site in rodent and human brain membranes, which is distinctly different from angiotensin receptors and key proteases processing angiotensins. It is hypothesized to be a new member of the renin-angiotensin system. This study was designed to isolate and identify this novel angiotensin binding site. An angiotensin analog, photoaffinity probe 125I-SBpa-Ang II, was used to specifically label the non-AT1, non-AT2 angiotensin binding site in mouse forebrain membranes, followed by a two-step purification procedure based on the molecular size and isoelectric point of the photoradiolabeled binding protein. Purified samples were subjected to two-dimensional gel electrophoresis followed by mass spectrometry identification of proteins in the two-dimensional gel sections containing radioactivity. LC-MS/MS analysis revealed eight protein candidates, of which the four most abundant were immunoprecipitated after photoradiolabeling. Immunoprecipitation studies indicated that the angiotensin binding site might be the membrane-bound variant of metalloendopeptidase neurolysin (EC 3.4.24.16). To verify these observations, radioligand binding and photoradiolabeling experiments were conducted in membrane preparations of HEK293 cells overexpressing mouse neurolysin or thimet oligopeptidase (EC 3.4.24.15), a closely related metalloendopeptidase of the same family. These experiments also identified neurolysin as the non-AT1, non-AT2 angiotensin binding site. Finally, brain membranes of mice lacking neurolysin were nearly devoid of the non-AT1, non-AT2 angiotensin binding site, further establishing membrane-bound neurolysin as the binding site. Future studies will focus on the functional significance of this highly specific, high affinity interaction between neurolysin and angiotensins.

SUBMITTER: Wangler NJ

PROVIDER: S-EPMC3249063 | biostudies-literature | 2012 Jan

REPOSITORIES: biostudies-literature

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Identification of membrane-bound variant of metalloendopeptidase neurolysin (EC 3.4.24.16) as the non-angiotensin type 1 (non-AT1), non-AT2 angiotensin binding site.

Wangler Naomi J NJ Santos Kira L KL Schadock Ines I Hagen Fred K FK Escher Emanuel E Bader Michael M Speth Robert C RC Karamyan Vardan T VT

The Journal of biological chemistry 20111028 1

Recently, we discovered a novel non-angiotensin type 1 (non-AT1), non-AT2 angiotensin binding site in rodent and human brain membranes, which is distinctly different from angiotensin receptors and key proteases processing angiotensins. It is hypothesized to be a new member of the renin-angiotensin system. This study was designed to isolate and identify this novel angiotensin binding site. An angiotensin analog, photoaffinity probe 125I-SBpa-Ang II, was used to specifically label the non-AT1, non ...[more]

PMID: 22039052

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Project description:It has long been known that angiotensin type-1 receptors (AT1R) play a critical role in sympathetic regulation, cardiovascular activity, and hormone secretion under physiological and pathological states. On the other hand, the functional significance of angiotensin type-2 receptors (AT2R) is poorly understood. In a recent study we demonstrated that, in rats with chronic heart failure, AT1R protein expression was increased but AT2R expression was decreased in the rostral ventrolateral medulla (RVLM). This imbalance of angiotensin receptors contributed to sympatho-excitation in the heart failure state. In the current experiment, we measured AT1R and AT2R protein expressions in the brainstem, kidney and liver from male foetuses (3 days before birth), male neonates (3 days after birth), male and female adults (8 weeks) and male aged (28 months) rats by Western blot analysis. In the brainstem, we found that the foetuses and neonates exhibited a significantly lower AT2R protein expression compared with adult rats (foetus 0.08 ± 0.01, neonate 0.12 ± 0.01, male adult 0.25 ± 0.01, female adult 0.22 ± 0.02; n = 4 per group, p < 0.001 foetus and neonate compared with male or female adults). In contrast, the foetuses and neonates expressed significantly higher AT1R protein than that of the adults (foetus 0.64 ± 0.09, neonate 0.56 ± 0.01, male adult 0.13 ± 0.02, female adult 0.08 ± 0.02; n = 4 each group, p < 0.001 foetus and neonate compared with male and female adults). In the liver, the AT2R protein was also higher in foetus and neonate, than in adult rats. Interestingly, the foetal liver expressed higher AT1R protein compared with that of the neonate. In the kidney, AT2R expression was significantly increased with age (foetus 0.08 ± 0.01, neonate 0.19 ± 0.02, male adult 0.49 ± 0.04, female adult 0.90 ± 0.10; n = 4 per group, p < 0.01-0.001). AT1R expression, on the other hand, was higher in the foetuses than that in both neonate and male adults. This study provides data contrary to existing dogma that AT2R expression is higher in foetal life and low in adults, suggesting an involvement of a potentially important functional role for AT2R in adult animals and AT1R in foetal development and/or physiology.

Project description:Gliomas are aggressive primary brain tumors with high infiltrative potential. The expression of Angiotensin II (Ang II) receptors has been associated with poor prognosis in human astrocytomas, the most common type of glioma. In this study, we investigated the role of Angiotensin II in glioma malignancy through transcriptional profiling and network analysis of cultured C6 rat glioma cells exposed to Ang II and to inhibitors of its membrane receptor subtypes. C6 cells were treated with Ang II and specific antagonists of AT1 and AT2 receptors. Total RNA was isolated after three and six hours of Ang II treatment and analyzed by oligonucleotide microarray technology. Gene expression data was evaluated through transcriptional network modeling to identify how differentially expressed (DE) genes are connected to each other. Moreover, other genes co-expressing with the DE genes were considered in these analyses in order to support the identification of enriched functions and pathways. A hub-based network analysis showed that the most connected nodes in Ang II-related networks exert functions associated with cell proliferation, migration and invasion, key aspects for glioma progression. The subsequent functional enrichment analysis of these central genes highlighted their participation in signaling pathways that are frequently deregulated in gliomas such as ErbB, MAPK and p53. Noteworthy, either AT1 or AT2 inhibitions were able to down-regulate different sets of hub genes involved in protumoral functions, suggesting that both Ang II receptors could be therapeutic targets for intervention in glioma. Taken together, our results point out multiple actions of Ang II in glioma pathogenesis and reveal the participation of both Ang II receptors in the regulation of genes relevant for glioma progression. This study is the first one to provide systems-level molecular data for better understanding the protumoral effects of Ang II in the proliferative and infiltrative behavior of gliomas.

Project description:Gliomas are aggressive primary brain tumors, presenting surgery limitations due to their highly infiltrative potential. The expression of Angiotensin II (Ang II) receptors in human astrocytomas was previously associated with a poor prognosis. Accordingly, this study was undertaken to reveal the molecular mechanisms underlying Ang II actions in gliomas through the transcriptomic analysis of glioma cells exposed to Ang II. C6 glioma cells were treated with Ang II and specific antagonists of AT1 and AT2. Total RNA was isolated at three and six hours intervals and submitted to oligonucleotide microarray protocol. The differentially expressed genes were obtained by paired t-tests with p<0.05 and interpreted using Venn diagrams, functional enrichment and protein interaction network analyses. Validation of microarray results was carried out through qPCR experiments of selected genes. We found a high number of significant genes with low fold changes in gene expression at the time intervals studied. These genes were regulated in a time dependent-manner, with most gene expression changes being exclusive to one of the time intervals evaluated. Our results indicated that blocking AT1 or AT2 changed the expression of genes involved in regulation of transcription, cell cycle, cell proliferation, differentiation, apoptosis, cell adhesion, cell migration, regulation of actin cytoskeleton, protein transport and protein ubiquitination. Additionally, the signaling pathways over-represented by the significant genes were ErbB, mTOR, MAPK, neurotrophin, insulin and Wnt. Finally, interactome analyses revealed hub genes associated with cell proliferation, survival, migration, transport, structural support, neurotrophin pathway, MAPK signaling and Wnt signaling. Taken together, our findings implicate Ang II-transcriptional regulation in glioma progression by means of the modulation of genes participating in protumoral functions. This transcriptome pattern is observed upon Ang II activation of either AT1 or AT2 receptors, thereby highlighting the relevance of both receptor subtypes in glioma progression. Interactome analyses disclosed hub genes regulated by Ang II which may present higher control over their networks. These genes participate in biological functions that could enhance the degree of malignancy in gliomas and thus should be further explored. C6 cells were cultured in Dulbecco's modified Eagle's medium (DMEM) supplemented with 10% fetal bovine serum, 100 Units/ml penicillin and 100 M-BM-5g/ml streptomycin. Cells were seeded in cell culture dishes and incubated at 37M-BM-0C/ 5% CO2 until becoming confluent. Then, these cells were pre-treated (30 minutes) with either AT1 receptor antagonist (Losartan: 10-5M) or AT2 receptor antagonist (PD123319: 10-5M) followed by Ang II treatment (10-7 M) according to the treatment scheme: Group 1 M-bM-^@M-^S control; Group 2 M-bM-^@M-^S cells only treated with Ang II; Group 3 M-bM-^@M-^S cells pre-treated (30 minutes) with Losartan and then treated with Ang II; Group 4 M-bM-^@M-^S cells pre-treated (30 minutes) with PD123319 and then treated with Ang II. To identify which genes were significantly differentially expressed, paired t-tests (p<0.05) were performed in the following comparisons: Ang II x Control (3h); Ang II x Control (6h); Ang II +Los x Ang II (3h); Ang II +Los x Ang II (6h); Ang II +PD123319 x Ang II (3h); Ang II +PD123319 x Ang II (6h).

Dataset Information

Identification of membrane-bound variant of metalloendopeptidase neurolysin (EC 3.4.24.16) as the non-angiotensin type 1 (non-AT1), non-AT2 angiotensin binding site.

Publications

Identification of membrane-bound variant of metalloendopeptidase neurolysin (EC 3.4.24.16) as the non-angiotensin type 1 (non-AT1), non-AT2 angiotensin binding site.

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