title: Angiotensin type 1 receptor resistance to blockade in the opossum proximal tubule cell due to variations in the binding pocket.
abstract: Blockade of the angiotensin (ANG) II receptor type 1 (AT(1)R) with angiotensin receptor blockers (ARBs) is widely used in the treatment of hypertension. However, ARBs are variably effective in reducing blood pressure, likely due, in part, to polymorphisms in the ARB binding pocket of the AT(1)R. Therefore, we need a better understanding of variations/polymorphisms that alter binding of ARBs in heterogeneous patient populations. The opossum proximal tubule cell (OKP) line is commonly used in research to evaluate renal sodium handling and therefore blood pressure. Investigating this issue, we found natural sequence variations in the opossum AT(1)R paralleling those observed in the human AT(1)R. Therefore, we posited that these sequence variations may explain ARB resistance. We demonstrate that OKP cells express AT(1)R mRNA, bind (125)I-labeled ANG II, and exhibit ANG II-induced phosphorylation of Jak2. However, Jak2 phosphorylation is not inhibited by five different ARBs commonly used to treat hypertension. Additionally, nonradioactive ANG II competes (125)I-ANG II efficiently, whereas a 10-fold molar excess of olmesartan and the ANG II receptor type 2 blocker PD-123319 is unable to block (125)I-ANG II binding. In contrast, ANG II binding to OKP cells stably expressing rat AT(1A)Rs, which have a conserved AT(1)R-binding pocket with human AT(1)R, is efficiently inhibited by olmesartan. A novel observation was that resistance to ARB binding to opossum AT(1)Rs correlates with variations from the human receptor at positions 108, 163, 192, and 198 within the ARB-binding pocket. These observations highlight the potential utility of evaluating AT(1)R polymorphisms within the ARB-binding pocket in various hypertensive populations.
authors: Division of Nephrology, Department of Internal Medicine, University of Missouri-Columbia, Columbia, MO 65212, USA.
authors: Ravi
authors: R
authors: Nistala
authors: Bradley T
authors: BT
authors: Andresen
authors: Lakshmi
authors: L
authors: Pulakat
authors: Alex
authors: A
authors: Meuth
authors: Catherine
authors: C
authors: Sinak
authors: Chirag
authors: C
authors: Mandavia
authors: Thomas
authors: T
authors: Thekkumkara
authors: Robert C
authors: RC
authors: Speth
authors: Adam
authors: A
authors: Whaley-Connell
authors: James R
authors: JR
authors: Sowers
mesh_terms: D000804:Angiotensin II / Q000378:metabolism / Q000494:pharmacology; D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology*; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D004351:Drug Resistance / Q000235:genetics; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D007457:Iodine Radioisotopes; D053614:Janus Kinase 2 / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000187:drug effects*; D009893:Opossums / Q000235:genetics*; D010802:Phylogeny; D011110:Polymorphism, Genetic / Q000235:genetics; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D044140:Receptor, Angiotensin, Type 1 / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D013045:Species Specificity; D013777:Tetrazoles / Q000494:pharmacology*; D014662:Vasoconstrictor Agents / Q000378:metabolism / Q000494:pharmacology
chemical_list: D047228:Angiotensin II Type 1 Receptor Blockers; D007093:Imidazoles; D007457:Iodine Radioisotopes; D012333:RNA, Messenger; D044140:Receptor, Angiotensin, Type 1; D013777:Tetrazoles; D014662:Vasoconstrictor Agents; D000804:Angiotensin II; C437965:olmesartan; D053614:Janus Kinase 2
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