title: Association of the novel non-AT1, non-AT2 angiotensin binding site with neuronal cell death.
abstract: We have discovered a non-AT(1), non-AT(2) angiotensin binding site in rodent and human brain membranes, which, based on its pharmacological/biochemical properties and tissue distribution, is different from angiotensin receptors and key proteases processing angiotensins. In this study, the novel angiotensin binding site was localized to a specific brain cell type by using radioligand receptor binding assays. Our results indicate that the novel binding site is expressed in mouse primary cortical neuronal membranes but not in primary cortical astroglial and bEnd.3 brain capillary endothelial cell membranes. Whole-cell binding assays in neurons showed that the binding site faces the outer side of the plasma membrane. Consistent with our previous observations, the novel binding site was unmasked by the sulfhydryl reagent p-chloromercuribenzoate. This effect had a bell-shaped curve and was reversed by reduced glutathione, indicating that the function of the binding site might be regulated by the redox state of the environment. Density of the novel binding site measured by saturation binding assays was significantly increased in neuronal membranes of cells challenged in four in vitro models of cell death (oxygen-glucose deprivation, sodium azide-induced hypoxia, N-methyl-D-aspartate neurotoxicity, and hydrogen peroxide neurotoxicity). In addition, our in vivo data from developing mouse brains showed that the density of the novel angiotensin binding site changes similarly to the pattern of neuronal death in maturating brain. This is the first time that evidence is provided on the association of the novel angiotensin binding site with neuronal death, and future studies directed toward understanding of the functions of this protein are warranted.
authors.affiliation: Department of Pharmaceutical Sciences and Vascular Drug Research Center, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, Texas 79106, USA.
authors.forename: Mamoon
authors.initials: M
authors.lastname: Rashid
authors.forename: Thiruma V
authors.initials: TV
authors.lastname: Arumugam
authors.forename: Vardan T
authors.initials: VT
authors.lastname: Karamyan
mesh_terms: D015059:1-Sarcosine-8-Isoleucine Angiotensin II / Q000378:metabolism; D002731:4-Chloromercuribenzenesulfonate / Q000494:pharmacology; D000804:Angiotensin II / Q000378:metabolism; D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology; D057912:Angiotensin II Type 2 Receptor Blockers / Q000494:pharmacology; D000818:Animals; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000378:metabolism; D005260:Female; D005978:Glutathione / Q000494:pharmacology; D019803:Glutathione Disulfide / Q000494:pharmacology; D007700:Kinetics; D051379:Mice; D008815:Mice, Inbred Strains; D009474:Neurons / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D016548:Prosencephalon / Q000166:cytology / Q000196:embryology / Q000254:growth & development / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects / Q000502:physiology; D011945:Receptors, Angiotensin / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors / Q000378:metabolism; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism; D013696:Temperature; D020245:p-Chloromercuribenzoic Acid / Q000494:pharmacology
chemical_list: D047228:Angiotensin II Type 1 Receptor Blockers; D057912:Angiotensin II Type 2 Receptor Blockers; D011945:Receptors, Angiotensin; D011956:Receptors, Cell Surface; D000804:Angiotensin II; D020245:p-Chloromercuribenzoic Acid; D002731:4-Chloromercuribenzenesulfonate; D015059:1-Sarcosine-8-Isoleucine Angiotensin II; D005978:Glutathione; D019803:Glutathione Disulfide