title: Neoceptor concept based on molecular complementarity in GPCRs: a mutant adenosine A(3) receptor with selectively enhanced affinity for amine-modified nucleosides.
abstract: Adenosine A(3) receptors are of interest in the treatment of cardiac ischemia, inflammation, and neurodegenerative diseases. In an effort to create a unique receptor mutant that would be activated by tailor-made synthetic ligands, we mutated the human A(3) receptor at the site of a critical His residue in TM7, previously proposed to be involved in ligand recognition through interaction with the ribose moiety. The H272E mutant receptor displayed reduced affinity for most of the uncharged A(3) receptor agonists and antagonists examined. For example, the nonselective agonist 1a was 19-fold less potent at the mutant receptor than at the wild-type receptor. The introduction of an amino group on the ribose moiety of adenosine resulted in either equipotency or enhanced binding affinity at the H272E mutant relative to wild-type A(3) receptors, depending on the position of the amino group. 3'-Amino-3'-deoxyadenosine proved to be 7-fold more potent at the H272E mutant receptor than at the wild-type receptor, while the corresponding 2'- and 5'-amino analogues did not display significantly enhanced affinities. An 3'-amino-N(6)-iodobenzyl analogue showed only a small enhancement at the mutant (K(i) = 320 nM) vs wild-type receptors. The 3'-amino group was intended for a direct electrostatic interaction with the negatively charged ribose-binding region of the mutant receptor, yet molecular modeling did not support this notion. This design approach is an example of engineering the structure of mutant receptors to recognize synthetic ligands for which they are selectively matched on the basis of molecular complementarity between the mutant receptor and the ligand. We have termed such engineered receptors "neoceptors", since the ligand recognition profile of such mutant receptors need not correspond to the profile of the parent, native receptor.
authors.affiliation: Molecular Recognition Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA. kajacobs@helix.nih.gov
authors.forename: K A
authors.initials: KA
authors.lastname: Jacobson
authors.forename: Z G
authors.initials: ZG
authors.lastname: Gao
authors.forename: A
authors.initials: A
authors.lastname: Chen
authors.forename: D
authors.initials: D
authors.lastname: Barak
authors.forename: S A
authors.initials: SA
authors.lastname: Kim
authors.forename: K
authors.initials: K
authors.lastname: Lee
authors.forename: A
authors.initials: A
authors.lastname: Link
authors.forename: P V
authors.initials: PV
authors.lastname: Rompaey
authors.forename: S
authors.initials: S
authors.lastname: van Calenbergh
authors.forename: B T
authors.initials: BT
authors.lastname: Liang
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D000588:Amines / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D002540:Cerebral Cortex / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D008024:Ligands; D008958:Models, Molecular; D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D011869:Radioligand Assay; D051381:Rats; D043684:Receptor, Adenosine A3; D018047:Receptors, Purinergic P1 / Q000235:genetics* / Q000378:metabolism
chemical_list: D000588:Amines; D008024:Ligands; D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D043684:Receptor, Adenosine A3; D018047:Receptors, Purinergic P1; D000242:Cyclic AMP; D019204:GTP-Binding Proteins; D000241:Adenosine