title: FRET Studies of Quinolone-Based Bitopic Ligands and Their Structural Analogues at the Muscarinic M1Receptor.
abstract: Aiming to design partial agonists as well as allosteric modulators for the M1muscarinic acetylcholine (M1AChR) receptor, two different series of bipharmacophoric ligands and their structural analogues were designed and synthesized. The hybrids were composed of the benzyl quinolone carboxylic acid (BQCA)-derived subtype selective allosteric modulator 3 and the orthosteric building block 4-((4,5-dihydroisoxazol-3-yl)oxy)-N,N-dimethylbut-2-yn-1-amine (base of iperoxo) 1 or the endogenous ligand 2-(dimethylamino)ethyl acetate (base of acetylcholine) 2, respectively. The two pharmacophores were linked via alkylene chains of different lengths (C4, C6, C8, and C10). Furthermore, the corresponding structural analogues of 1 and 2 and of modified BQCA 3 with varying alkyl chain length between C2 and C10 were investigated. Fluorescence resonance energy transfer (FRET) measurements in a living single cell system were investigated in order to understand how these compounds interact with a G protein-coupled receptor (GPCR) on a molecular level and how the single moieties contribute to ligand receptor interaction. The characterization of the modified orthosteric ligands indicated that a linker attached to an orthoster rapidly attenuates the receptor response. Linker length elongation increases the receptor response of bitopic ligands, until reaching a maximum, followed by a gradual decrease. The optimal linker length was found to be six methylene groups at the M1AChR. A new conformational change is described that is not of inverse agonistic origin for long linker bitopic ligands and was further investigated by exceptional fragment-based screening approaches.
authors.affiliation: Department of Pharmaceutical and Medical Chemistry, Institute of Pharmacy, University of Würzburg , Am Hubland, 97074 Würzburg, Germany.
authors.forename: Regina
authors.initials: R
authors.lastname: Messerer
authors.affiliation: Department of Pharmacology and Toxicology, University of Würzburg , Versbacher Str. 9, 97078 Würzburg, Germany.|Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg , Josef Schneider Straße 2, 97080 Würzburg, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Kauk
authors.affiliation: Department of Pharmaceutical and Medical Chemistry, Institute of Pharmacy, University of Würzburg , Am Hubland, 97074 Würzburg, Germany.
authors.forename: Daniela
authors.initials: D
authors.lastname: Volpato
authors.affiliation: Department of Pharmacology and Toxicology, University of Würzburg , Versbacher Str. 9, 97078 Würzburg, Germany.|Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg , Josef Schneider Straße 2, 97080 Würzburg, Germany.
authors.forename: Maria Consuelo
authors.initials: MC
authors.lastname: Alonso Canizal
authors.affiliation: Department of Pharmaceutical and Medical Chemistry, Institute of Pharmacy, University of Würzburg , Am Hubland, 97074 Würzburg, Germany.
authors.forename: Jessika
authors.initials: J
authors.lastname: Klöckner
authors.affiliation: Department of Pharmacology and Toxicology, University of Würzburg , Versbacher Str. 9, 97078 Würzburg, Germany.|Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg , Josef Schneider Straße 2, 97080 Würzburg, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Zabel
authors.affiliation: Department of Pharmacology and Toxicology, University of Würzburg , Versbacher Str. 9, 97078 Würzburg, Germany.|Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg , Josef Schneider Straße 2, 97080 Würzburg, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Nuber
authors.affiliation: Department of Pharmacology and Toxicology, University of Würzburg , Versbacher Str. 9, 97078 Würzburg, Germany.|Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg , Josef Schneider Straße 2, 97080 Würzburg, Germany.
authors.forename: Carsten
authors.identifier: 0000-0003-0884-9300
authors.initials: C
authors.lastname: Hoffmann
authors.affiliation: Department of Pharmaceutical and Medical Chemistry, Institute of Pharmacy, University of Würzburg , Am Hubland, 97074 Würzburg, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Holzgrabe
mesh_terms: D031541:Fluorescence Resonance Energy Transfer; D008024:Ligands; D015363:Quinolones / Q000737:chemistry*; D043643:Receptor, Muscarinic M1 / Q000737:chemistry*
chemical_list: D008024:Ligands; D015363:Quinolones; D043643:Receptor, Muscarinic M1