title: Design, synthesis and biological evaluation of bivalent ligands against A(1)-D(1) receptor heteromers.
abstract: OBJECTIVE
  To design and synthesize bivalent ligands for adenosine A1-dopamine D1 receptor heteromers (A1-D1R), and evaluate their pharmacological activities.
  
  
  METHODS
  Bivalent ligands and their corresponding A1R monovalent ligands were designed and synthesized. The affinities of the bivalent ligands for A1R and D1R in rat brain membrane preparation were examined using radiolabeled binding assays. To demonstrate the formation of A1-D1R, fluorescence resonance energy transfer (FRET) was conducted in HEK293 cells transfected with D1-CFP and A1-YFP. Molecular modeling was used to analyze the possible mode of protein-protein and protein-ligand interactions.
  
  
  RESULTS
  Two bivalent ligands for A1R and D1R (20a, 20b), as well as the corresponding A1R monovalent ligands (21a, 21b) were synthesized. In radiolabeled binding assays, the bivalent ligands showed affinities for A1R 10-100 times higher than those of the corresponding monovalent ligands. In FRET experiments, the bivalent ligands significantly increased the heterodimerization of A1R and D1R compared with the corresponding monovalent ligands. A heterodimer model with the interface of helixes 3, 4, 5 of A1R and helixes 1, 6, 7 from D1R was established with molecular modeling. The distance between the two ligand binding sites in the heterodimer model was approximately 48.4 Å, which was shorter than the length of the bivalent ligands.
  
  
  CONCLUSIONS
  This study demonstrates the existence of A1-D1R in situ and a simultaneous interaction of bivalent ligands with both the receptors.
authors: The State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.
authors: Jian
authors: J
authors: Shen
authors: Lei
authors: L
authors: Zhang
authors: Wan-ling
authors: WL
authors: Song
authors: Tao
authors: T
authors: Meng
authors: Xin
authors: X
authors: Wang
authors: Lin
authors: L
authors: Chen
authors: Lin-yin
authors: LY
authors: Feng
authors: Ye-chun
authors: YC
authors: Xu
authors: Jing-kang
authors: JK
authors: Shen
mesh_terms: D058917:Adenosine A2 Receptor Antagonists / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism; D018491:Dopamine Agonists / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D015195:Drug Design; D031541:Fluorescence Resonance Energy Transfer; D057809:HEK293 Cells; D006801:Humans; D008024:Ligands; D062105:Molecular Docking Simulation; D015394:Molecular Structure; D011485:Protein Binding; D055503:Protein Multimerization; D051381:Rats; D017208:Rats, Wistar; D043682:Receptor, Adenosine A1 / Q000737:chemistry / Q000378:metabolism*; D017447:Receptors, Dopamine D1 / Q000819:agonists / Q000737:chemistry / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D058917:Adenosine A2 Receptor Antagonists; D018491:Dopamine Agonists; D008024:Ligands; D043682:Receptor, Adenosine A1; D017447:Receptors, Dopamine D1