Angiotensin II receptor recognized by DuP753 regulates two distinct guanine nucleotide-binding protein signaling pathways.
The 7315c cell, derived from a rat anterior pituitary tumor, expresses an angiotensin II (AII) receptor. [3H]AII binds to 7315c membranes specifically and saturably (Kd = 2.1 +/- 0.6 x 10(-6) M, Bmax = 282 +/- 33 fmol/mg of protein). GTP diminished the affinity of the membranes for [3H]AII (Kd = 4.1 +/- 0.4 x 10(-9) M, Bmax = 210 +/- 26 fmol/mg of protein). [3H]AII binding was displaced by AII (Ki = 1.3 +/- 0.6 x 10(-9) M), angiotensin III (AIII) (Ki = 0.9 +/- 0.4 x 10(-9) M), and the nonpeptide AII antagonist DuP753 (Ki = 1.4 +/- 0.6 x 10(-8) M). In contrast, a second nonpeptide AII ligand, PD123177, did not compete for [3H]AII binding sites. In intact cells, AII and AIII stimulated inositol trisphosphate (IP3) production (EC50 = 1.1 +/- 0.6 x 10(-8) M and 1.1 +/- 0.5 x 10(-8) M, respectively); this response to AII was antagonized by DuP753 (Ki = 1.7 +/- 0.3 x 10(-7) M). Pertussis toxin treatment failed to affect the ability of AII to stimulate IP3 production. In a crude membrane preparation, GTP was required for maximal AII-induced IP3 stimulation; guanosine thio-diphosphate abolished the agonist-GTP stimulation of IP3 production, in a concentration-dependent fashion. AII and AIII also inhibited adenylyl cyclase (EC50 = 2.9 +/- 1.1 x 10(-8) M and 6.0 +/- 1.0 x 10(-8) M, respectively). DuP753 antagonized the inhibition by AII of adenylyl cyclase (Ki = 2.8 +/- 0.4 x 10(-8) M). PD123177 failed to antagonize AII-induced cyclase inhibition. Pertussis toxin treatment abolished the AII and AIII inhibition of adenylyl cyclase. GTP was required for AII-induced inhibition of adenylyl cyclase. These data suggest that, in 7315c cells, a single subtype of AII receptor, identified by DuP753, is capable of regulating two different guanine nucleotide-binding protein (G protein) signalling pathways; one G protein, which is insensitive to pertussis toxin, stimulates IP3 production and the other G protein, which is sensitive to pertussis toxin, inhibits adenylyl cyclase.
Crawford
K W
KW
Uniformed Services University of the Health Sciences, Department of Pharmacology, Bethesda, Maryland 20889-4799.
Frey
E A
EA
Cote
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D037361:Adenylate Cyclase Toxin; D000067956:Adenylyl Cyclase Inhibitors; D000804:Angiotensin II / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000494:pharmacology; D057911:Angiotensin Receptor Antagonists; D000818:Animals; D001713:Biphenyl Compounds / Q000494:pharmacology*; D002462:Cell Membrane / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000502:physiology*; D006160:Guanosine Triphosphate / Q000502:physiology; D007093:Imidazoles / Q000494:pharmacology*; D019808:Losartan; D037342:Pertussis Toxin; D010716:Phosphatidylinositols / Q000378:metabolism; D010903:Pituitary Gland, Anterior / Q000473:pathology; D010911:Pituitary Neoplasms / Q000201:enzymology / Q000473:pathology; D051381:Rats; D011915:Rats, Inbred BUF; D011945:Receptors, Angiotensin / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D013777:Tetrazoles / Q000494:pharmacology*; D014316:Tritium; D014407:Tumor Cells, Cultured / Q000187:drug effects; D010738:Type C Phospholipases / Q000187:drug effects / Q000378:metabolism; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D037361:Adenylate Cyclase Toxin; D000067956:Adenylyl Cyclase Inhibitors; D057911:Angiotensin Receptor Antagonists; D001713:Biphenyl Compounds; D007093:Imidazoles; D010716:Phosphatidylinositols; D011945:Receptors, Angiotensin; D013439:Sulfhydryl Reagents; D013777:Tetrazoles; D010566:Virulence Factors, Bordetella; D014316:Tritium; D000804:Angiotensin II; D006160:Guanosine Triphosphate; D037342:Pertussis Toxin; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D019808:Losartan