title: Fluorescence correlation spectroscopy in drug discovery: study of Alexa532-endothelin 1 binding to the endothelin ETA receptor to describe the pharmacological profile of natural products.
abstract: Fluorescence correlation spectroscopy and the newly synthesized Alexa532-ET1 were used to study the dynamics of the endothelin ET(A) receptor-ligand complex alone and under the influence of a semisynthetic selective antagonist and a fungal extract on living A10 cells. Dose-dependent increase of inositol phosphate production was seen for Alexa532-ET1, and its binding was reduced to 8% by the selective endothelin ET(A) antagonist BQ-123, confirming the specific binding of Alexa532-ET1 to the endothelin ET(A) receptor. Two different lateral mobilities of the receptor-ligand complexes within the cell membrane were found allowing the discrimination of different states for this complex. BQ-123 showed a strong binding affinity to the "inactive" receptor state characterized by the slow diffusion time constant. A similar effect was observed for the fungal extract, which completely displaced Alexa532-ET1 from its binding to the "inactive" receptor state. These findings suggest that both BQ-123 and the fungal extract act as inverse agonists.
authors.affiliation: Department of Molecular Pharmacology and Pharmacognosy, Drug Discovery Center, Institute for Scientific Research and High Technology Services, Panama City, Panama. ccaballero@indicasat.org.pa
authors.forename: Catherina
authors.initials: C
authors.lastname: Caballero-George
authors.forename: Thomas
authors.initials: T
authors.lastname: Sorkalla
authors.forename: Daniel
authors.initials: D
authors.lastname: Jakobs
authors.forename: Jessica
authors.initials: J
authors.lastname: Bolaños
authors.forename: Huzefa
authors.initials: H
authors.lastname: Raja
authors.forename: Carol
authors.initials: C
authors.lastname: Shearer
authors.forename: Eldredge
authors.initials: E
authors.lastname: Bermingham
authors.forename: Hanns
authors.initials: H
authors.lastname: Häberlein
mesh_terms: D000818:Animals; D001203:Ascomycota / Q000737:chemistry; D002460:Cell Line; D055808:Drug Discovery; D019332:Endothelin-1 / Q000031:analogs & derivatives* / Q000378:metabolism; D005452:Fluoresceins / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000166:cytology; D010456:Peptides, Cyclic / Q000494:pharmacology; D051381:Rats; D044022:Receptor, Endothelin A / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
chemical_list: C575335:Alexa532-endothelin 1; D019332:Endothelin-1; D005452:Fluoresceins; D010456:Peptides, Cyclic; D044022:Receptor, Endothelin A; C072247:cyclo(Trp-Asp-Pro-Val-Leu)