title: 125I-Antisauvagine-30: a novel and specific high-affinity radioligand for the characterization of corticotropin-releasing factor type 2 receptors.
abstract: Corticotropin-releasing factor (CRF) receptors type 1 (CRF(1)) and type 2 (CRF(2)) differ from each other in their pharmacological properties. The human and ovine CRF versions bind to CRF(1) receptors with significantly higher affinity than to CRF(2) receptors. Recently antisauvagine-30, an N-terminally truncated version of the CRF analog sauvagine, was characterized as a specific antagonist to mouse CRF(2B). We have synthesized the radiolabeled version (125)I-antisauvagine-30 and tested it for its affinity at human CRF(1) (hCRF(1)), hCRF(2A), Xenopus CRF(1) (xCRF(1)) and xCRF(2) receptors. In control binding studies (125)I-labeled hCRF, sauvagine and astressin were also bound to these receptors. (125)I-antisauvagine-30 exclusively bound to hCRF(2A) and xCRF(2) but not to hCRF(1) and xCRF(1) receptors. (125)I-antisauvagine-30 binding to hCRF(2A) and xCRF(2) receptors was saturable and of high affinity (hCRF(2A): K(d)=125 pM; xCRF(2): K(d)=1.1 nM). In displacement binding experiments using (125)I-antisauvagine-30 as radioligand several CRF analogs bound to hCRF(2A) and xCRF(2) receptors with similar rank orders as reported with other CRF radioligands. Finally, preliminary studies using (125)I-antisauvagine-30 binding to membrane homogenates prepared from different rat brain structures showed that the peptide bound specifically to brain areas expressing CRF(2) receptors. These data demonstrate that (125)I-antisauvagine-30 is the first high-affinity ligand to specifically label CRF(2) receptors.
authors.affiliation: F. Hoffmann-La Roche Ltd, Pharma Division, Preclinical Research, Building 70, Room 307, Grenzacher Strasse 124, 4070, Basel, Switzerland.
authors.forename: J
authors.initials: J
authors.lastname: Higelin
authors.forename: G
authors.initials: G
authors.lastname: Py-Lang
authors.forename: C
authors.initials: C
authors.lastname: Paternoster
authors.forename: G J
authors.initials: GJ
authors.lastname: Ellis
authors.forename: A
authors.initials: A
authors.lastname: Patel
authors.forename: F M
authors.initials: FM
authors.lastname: Dautzenberg
mesh_terms: D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D001923:Brain Chemistry / Q000187:drug effects; D002478:Cells, Cultured; D003346:Corticotropin-Releasing Hormone / Q000378:metabolism; D006150:Guanine Nucleotides / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D007202:Indicators and Reagents; D007700:Kinetics; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D010446:Peptide Fragments; D010455:Peptides / Q000494:pharmacology; D011869:Radioligand Assay; D019275:Radiopharmaceuticals; D051381:Rats; D018019:Receptors, Corticotropin-Releasing Hormone / Q000187:drug effects*; D014981:Xenopus
chemical_list: C101531:CRF receptor type 2; D006150:Guanine Nucleotides; D007202:Indicators and Reagents; D010446:Peptide Fragments; D010455:Peptides; D019275:Radiopharmaceuticals; D018019:Receptors, Corticotropin-Releasing Hormone; C116607:antisauvagine 30; D003346:Corticotropin-Releasing Hormone