Agonist and antagonist modulation of [35S]-GTP gamma S binding in transfected CHO cells expressing the neurotensin receptor.
1. The functional interaction of the cloned rat neurotensin receptor with intracellular G-proteins was investigated by studying the binding of the radiolabelled guanylyl nucleotide analogue [35S]-GTP gamma S induced by neurotensin to membranes prepared from transfected Chinese hamster ovary (CHO) cells. 2. The agonist-induced binding of [35S]-GTP gamma S was only detected in the presence of NaCl in the incubation buffer. However, it was also demonstrated that the binding of [3H]-neurotensin to its receptor was inhibited by NaCl. In the presence of 50 mM NaCl, the binding of the labelled nucleotide was about 2 fold increased by stimulation with saturating concentrations of neurotensin (EC50 value of 2.3 +/- 0.9 nM). 3. The stimulation of [35S]-GTP gamma S binding by neurotensin was mimicked by the stable analogue of neurotensin, JMV-449 (EC50 value of 1.7 +/- 0.4 nM) and the neurotensin related peptide neuromedin N (EC50 value of 21 +/- 6 nM). 4. The NT-induced [35S]-GTP gamma S binding was competitively inhibited by SR48692 (pA2 value of 9.55 +/- 0.28), a non-peptide neurotensin receptor antagonist. SR48692 alone had no effect on the specific binding of [35S]-GTP gamma S. 5. The response to neurotensin was found to be inhibited by the aminosteroid U-73122, a putative inhibitor of phospholipase C-dependent processes, indicating that this drug may act at the G-protein level. 6. Taken together, these results constitute the first characterization of the exchange of guanylyl nucleotides at the G-protein level that is induced by the neuropeptide neurotensin after binding to its receptor.
Hermans
E
E
Laboratory of Pharmacology, Université Catholique de Louvain, Brussels, Belgium.
Geurts
M
M
Maloteaux
J M
JM
D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D004963:Estrenes / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000502:physiology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000378:metabolism; D009496:Neurotensin / Q000378:metabolism; D011760:Pyrrolidinones / Q000494:pharmacology; D051381:Rats; D018028:Receptors, Neurotensin / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012965:Sodium Chloride / Q000494:pharmacology; D014162:Transfection
D004963:Estrenes; D011760:Pyrrolidinones; D018028:Receptors, Neurotensin; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D006153:Guanosine Diphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D009496:Neurotensin; D012965:Sodium Chloride; D019204:GTP-Binding Proteins