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Hafko R, Villapol S, Nostramo R, Symes A, Sabban EL, Inagami T, Saavedra JM. Commercially available angiotensin II At₂ receptor antibodies are nonspecific. PLoS One 2013; 8:e69234. [PMID: 23840911 PMCID: PMC3698141 DOI: 10.1371/journal.pone.0069234] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Accepted: 06/06/2013] [Indexed: 12/31/2022] Open
Abstract
Commercially available angiotensin II At₂ receptor antibodies are widely employed for receptor localization and quantification, but they have not been adequately validated. In this study, we characterized three commercially available At₂ receptor antibodies: 2818-1 from Epitomics, sc-9040 from Santa Cruz Biotechnology, Inc., and AAR-012 from Alomone Labs. Using western blot analysis the immunostaining patterns observed were different for every antibody tested, and in most cases consisted of multiple immunoreactive bands. Identical immunoreactive patterns were present in wild-type and At₂ receptor knockout mice not expressing the target protein. In the mouse brain, immunocytochemical studies revealed very different cellular immunoreactivity for each antibody tested. While the 2818-1 antibody reacted only with endothelial cells in small parenchymal arteries, the sc-9040 antibody reacted only with ependymal cells lining the cerebral ventricles, and the AAR-012 antibody reacted only with multiple neuronal cell bodies in the cerebral cortex. Moreover, the immunoreactivities were identical in brain tissue from wild-type or At₂ receptor knockout mice. Furthermore, in both mice and rat tissue extracts, there was no correlation between the observed immunoreactivity and the presence or absence of At₂ receptor binding or gene expression. We conclude that none of these commercially available At₂ receptor antibodies tested met the criteria for specificity. In the absence of full antibody characterization, competitive radioligand binding and determination of mRNA expression remain the only reliable approaches to study At₂ receptor expression.
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Affiliation(s)
- Roman Hafko
- Section on Pharmacology, Division of Intramural Research Programs, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Sonia Villapol
- Centre for Neuroscience and Regenerative Medicine, Bethesda, Maryland, United States of America
- Department of Pharmacology, Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States of America
| | - Regina Nostramo
- Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, New York, United States of America
| | - Aviva Symes
- Centre for Neuroscience and Regenerative Medicine, Bethesda, Maryland, United States of America
- Department of Pharmacology, Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States of America
| | - Esther L. Sabban
- Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, New York, United States of America
| | - Tadashi Inagami
- Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Juan M. Saavedra
- Section on Pharmacology, Division of Intramural Research Programs, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
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Shelat SG, Reagan LP, King JL, Fluharty SJ, Flanagan-Cato LM. Analysis of angiotensin type 2 receptors in vasopressinergic neurons and pituitary in the rat. REGULATORY PEPTIDES 1998; 73:103-12. [PMID: 9533814 DOI: 10.1016/s0167-0115(97)01066-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Previous functional studies indicated that an angiotensin type 2 (AT2) receptor subtype may participate in the regulation of vasopressin release by angiotensin II (AngII). In the present study, AT2 receptor-directed antiserum immunohistochemically detected AT2 receptors within the hypothalamic paraventricular (PVN) and the supraoptic nuclei (SON) of the rat brain, more specifically, in identified vasopressinergic neurons. Considering the lack of AT2 binding in the PVN and the SON using receptor autoradiography, we tested the hypothesis that these AT2 receptors are transported to the posterior pituitary. Western blot analysis detected AT2 immunoreactivity in the posterior pituitary. However, no AT2 binding was detected in posterior pituitary membranes, and no AT2 binding was detected with quantitative receptor autoradiography in the neurohypophysis. Thus, if AT2 receptors are transported from the magnocellular vasopressin neurons to the posterior pituitary, their role in AngII regulation of vasopressin release at the neurohypophyseal terminals remains to be clarified.
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Affiliation(s)
- S G Shelat
- Institute of Neurological Sciences, Department of Animal Biology, University of Pennsylvania, Philadelphia 19104, USA
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Fluharty SJ, Reagan LP, Yee DK. The angiotensin type 1 and type 2 receptor families. Siblings or cousins? ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1995; 377:193-215. [PMID: 7484423 DOI: 10.1007/978-1-4899-0952-7_11] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The diverse actions of angiotensin II (AngII) are mediated by cell surface receptors. Molecular cloning techniques have identified two distinct subtypes of AngII receptors referred to as AT1 and AT2. It is now well accepted that multiple forms of the AT1 receptor exist, but similar diversity of the AT2 subtype has not been conclusively demonstrated. Nonetheless, several converging lines of evidence do suggest that multiple AT2 receptors may be present in brain and cultured neuron-like cells lines. For instance, some AT2 receptors are regulated by guanine nucleotides and sulfhydryl-reducing agents, whereas others are insensitive. AT2 receptor populations also exhibit differing pharmacological profiles particularly with respect to their affinity for peptidic and non-peptidic ligands. Moreover, a recently developed anti-AT2 polyclonal antisera reveals a unique pattern of immunohistochemical staining in brain and it does not immunoreact with the recently cloned AT2 receptor. Collectively, these results support the hypothesis of multiple AT2 receptors at least within the CNS. Future studies should reveal whether these putative AT2 receptor subtypes result from unique genes or cell-specific post-translational modifications of a single gene product.
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Affiliation(s)
- S J Fluharty
- Department of Animal Biology, University of Pennsylvania, Philadelphia, USA
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