1310139

pubmed:Citation

1

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.

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MEDLINE

0026-895X

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154-62

pubmed-meshheading:1310139-Adenylate Cyclase, pubmed-meshheading:1310139-Adenylate Cyclase Toxin, pubmed-meshheading:1310139-Angiotensin II, pubmed-meshheading:1310139-Animals, pubmed-meshheading:1310139-Biphenyl Compounds, pubmed-meshheading:1310139-Cell Membrane, pubmed-meshheading:1310139-GTP-Binding Proteins, pubmed-meshheading:1310139-Guanosine Triphosphate, pubmed-meshheading:1310139-Imidazoles, pubmed-meshheading:1310139-Losartan, pubmed-meshheading:1310139-Pertussis Toxin, pubmed-meshheading:1310139-Phosphatidylinositols, pubmed-meshheading:1310139-Pituitary Gland, Anterior, pubmed-meshheading:1310139-Pituitary Neoplasms, pubmed-meshheading:1310139-Rats, pubmed-meshheading:1310139-Rats, Inbred BUF, pubmed-meshheading:1310139-Receptors, Angiotensin, pubmed-meshheading:1310139-Signal Transduction, pubmed-meshheading:1310139-Sulfhydryl Reagents, pubmed-meshheading:1310139-Tetrazoles, pubmed-meshheading:1310139-Tritium, pubmed-meshheading:1310139-Tumor Cells, Cultured, pubmed-meshheading:1310139-Type C Phospholipases, pubmed-meshheading:1310139-Virulence Factors, Bordetella

Angiotensin II receptor recognized by DuP753 regulates two distinct guanine nucleotide-binding protein signaling pathways.

Journal Article, Research Support, U.S. Gov't, P.H.S.