title: Enhanced endothelin ET(B) receptor down-regulation in human tumor cells.
abstract: The characteristics of specific binding of human [125I]Tyr(13)-endothelin-(1-21), [125I]-Tyr(13)-Suc-[Glu(9),Ala(11, 15)]-endothelin-(8-21), ([125I]IRL-1620) and endothelin ET(A) receptor antagonist [125I]Tyr(3)-(N-[(hexahydro-1H-azepin-1-yl)carbonyl]-L-Leu]-1Me )-D-Trp ([125I]PD151242) (number of sites and their affinity) and proliferation responses to exogenous endothelin receptor agonists (endothelin-1 and the endothelin ET(B) receptor-selective, truncated N-acetyl-[Ala(11,15)]-endothelin-(6-21) analogue BQ3020) were determined in cultured human fibroblasts and in tumorigenic HeLa cells. The cells were pre-incubated with equimolar concentrations of human endothelin-1 or its truncated analogue BQ3020. After pre-incubation (2 h), both peptides induced down-regulation of surface-membrane endothelin-1 receptors. This process was specific for endothelin ET(B) receptors and was much more intensive in tumorigenic cells. BQ3020, acting mostly through its C-terminus, induced nearly maximal endothelin ET(B) receptor down-regulation in HeLa cells. Staurosporine, a wide spectrum protein kinase inhibitor, significantly reduced, and N-[N-[N-[2, 6-dimethyl-1piperidinyl)carbonyl]-4-Me-L-Leu]-1-(methoxycarbonyl)- D-t ryptophanyl]-D-norleucine (BQ788), an endothelin ET(B) receptor antagonist, attenuated the down-regulation of endothelin receptors induced by endothelin receptor agonists. The down-regulation of endothelin ET(B) receptors was prevented by pre-incubation of the cells with the lysosomal enzyme blocker chloroquine. The endothelin-1-induced cell proliferation was attenuated by pre-incubation of the cells with the non-selective endothelin receptor antagonist Ac-D-10,11-dihydro-5H-dibenzo[a,d] cycloheptene-glycine-3,3-D-diphenyl-Ala-Leu-Asp-Ile-Ile-Trp (PD142893) and it was only partially reduced by the endothelin ET(A) receptor-selective endothelin antagonist PD151242.
authors.affiliation: Institute of Experimental Pharmacology, Cardiovascular Research Laboratory, Slovak Academy of Sciences, Dubravska cesta 9, 842 16, Bratislava, Slovak Republic. exfadrim@savba.sk
authors.forename: J
authors.initials: J
authors.lastname: Drimal
authors.forename: J
authors.initials: J
authors.lastname: Drimal
authors.forename: D
authors.initials: D
authors.lastname: Drimal
mesh_terms: D002478:Cells, Cultured; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics*; D019332:Endothelin-1 / Q000378:metabolism; D016232:Endothelins / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008024:Ligands; D008566:Membranes / Q000378:metabolism; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism*; D010446:Peptide Fragments / Q000494:pharmacology; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin / Q000096:biosynthesis* / Q000187:drug effects / Q000235:genetics*
chemical_list: D019332:Endothelin-1; D016232:Endothelins; D008024:Ligands; D010446:Peptide Fragments; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin; C075771:BQ 3020