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Effects of the N343A mutation in TM6 of the human serotonin 5‐HT2A Receptor
Author(s) -
Braden Michael R.,
Chambers James J.,
Nichols David E.
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a247-c
Subject(s) - chemistry , docking (animal) , serotonergic , stereochemistry , tryptamines , serotonin , hallucinogen , receptor , mutant , ligand (biochemistry) , pharmacology , biochemistry , tryptamine , biology , medicine , gene , nursing
The human serotonin 2A receptor (h5‐HT 2A R) plays an essential role in cognition, and is the principal target for serotonergic hallucinogens as well as atypical antipsychotics. Utilizing our in silico ‐activated h5‐HT 2A R homology model, an interaction was predicted between Asn343(6.55) in TM6 and the carbonyl of LSD. Virtual docking simulations of a new class of 5‐HT2 agonists, substituted N ‐benzyl phenethylamines (“ N ‐Benzyls”), indicated that interaction with N343 also might contribute to the high binding affinities of those compounds. It was hypothesized that an N343A mutation would have a detrimental effect on binding and activity of ergolines and N ‐Benzyl compounds with polar ortho‐substituents. Surprisingly, affinity was relatively unaffected for most ergolines and N ‐Benzyls. LSD actually had 2‐fold increased affinity for the N343A mutant, and other tryptamines had mixed effects. Dramatic decreases in binding affinity were observed with an N ‐Benzyl analogue that lacked a polar ortho‐substituent ( N ‐naphthyl; >10‐fold loss) and serotonin (>10‐fold loss). Using phosphoinositide accumulation to assess function, LSD, DET, and DMT showed 3‐ to 4‐fold increased potency, psilocin and 5‐MeO‐DMT were 2‐ and 5‐fold less potent, respectively, and serotonin was 60‐fold less potent. The N343A mutation also decreased the intrinsic activity of all drugs tested. Thus, our original hypothesis appears incorrect. We now hypothesize that N343 either stabilizes a high‐energy ground state of the helical bundle, or else may stabilize an activated receptor conformation once the ligand has bound. Supported by NIDA grant DA02189.