title: Design, synthesis and pharmacological evaluation of 5-hydroxytryptamine(1a) receptor ligands to explore the three-dimensional structure of the receptor.
abstract: In this work, we evaluate the structural differences of transmembrane helix 3 in rhodopsin and the 5-hydroxytryptamine 1A (5-HT1A) receptor caused by their different amino acid sequence. Molecular dynamics simulations of helix 3 in the 5-HT1A receptor tends to bend toward helix 5, in sharp contrast to helix 3 in rhodopsin, which is properly located within the position observed in the crystal structure. The relocation of the central helix 3 in the helical bundle facilitates the experimentally derived interactions between the neurotransmitters and the Asp residue in helix 3 and the Ser/Thr residues in helix 5. The different amino acid sequence that forms helix 3 in rhodopsin (basically the conserved Gly(3.36)Glu(3.37) motif in the opsin family) and the 5-HT1A receptor (the conserved Cys(3.36)Thr(3.37) motif in the neurotransmitter family) produces these structural divergences. These structural differences were experimentally checked by designing and testing ligands that contain comparable functional groups but at different interatomic distance. We have estimated the position of helix 3 relative to the other helices by systematically changing the distance between the functional groups of the ligands (1 and 2) that interact with the residues in the receptor. Thus, ligand 1 optimally interacts with a model of the 5-HT1A receptor that matches rhodopsin template, whereas ligand 2 optimally interacts with a model that possesses the proposed conformation of helix 3. The lack of affinity of 1 (K(i) > 10,000 nM) and the high affinity of 2 (K(i) = 24 nM) for the 5-HT1A receptor binding sites, provide experimental support to the proposed structural divergences of helix 3 between the 5-HT1A receptor and rhodopsin.
authors.affiliation: Departamento de Química Orgánica I, Facultad de Ciencias Químicas, Universidad Complutense, Madrid, Spain.
authors.forename: María L
authors.initials: ML
authors.lastname: López-Rodríguez
authors.forename: Bruno
authors.initials: B
authors.lastname: Vicente
authors.forename: Xavier
authors.initials: X
authors.lastname: Deupi
authors.forename: Sergio
authors.initials: S
authors.lastname: Barrondo
authors.forename: Mireia
authors.initials: M
authors.lastname: Olivella
authors.forename: M José
authors.initials: MJ
authors.lastname: Morcillo
authors.forename: Bellinda
authors.initials: B
authors.lastname: Behamú
authors.forename: Juan A
authors.initials: JA
authors.lastname: Ballesteros
authors.forename: Joan
authors.initials: J
authors.lastname: Sallés
authors.forename: Leonardo
authors.initials: L
authors.lastname: Pardo
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D001216:Asparagine / Q000378:metabolism; D001224:Aspartic Acid / Q000378:metabolism; D003198:Computer Simulation; D015195:Drug Design; D066298:In Vitro Techniques; D008297:Male; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D017433:Protein Structure, Secondary; D051381:Rats; D017207:Rats, Sprague-Dawley; D011985:Receptors, Serotonin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D044263:Receptors, Serotonin, 5-HT1; D012243:Rhodopsin / Q000737:chemistry; D017299:Rod Opsins / Q000737:chemistry; D018490:Serotonin Agents / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology
chemical_list: D000596:Amino Acids; D008565:Membrane Proteins; D011985:Receptors, Serotonin; D044263:Receptors, Serotonin, 5-HT1; D017299:Rod Opsins; D018490:Serotonin Agents; D001224:Aspartic Acid; D001216:Asparagine; D012243:Rhodopsin