Studies of the biogenic amine transporters. XI. Identification of a 1-[2-[bis(4-fluorophenyl)methoxy]ethyl]-4-(3-phenylpropyl)piperazine (GBR12909) analog that allosterically modulates the serotonin transporter.
Previous studies identified partial inhibitors of serotonin (5-HT) transporter and dopamine transporter binding. We report here on a partial inhibitor of 5-HT transporter (SERT) binding identified among a group of 1-[2-[bis(4-fluorophenyl)methoxy]ethyl]-4-(3-phenylpropyl)piperazine analogs (4-[2-[bis(4-fluorophenyl)-methoxy]ethyl]-1-(2-trifluoromethyl-benzyl)-piperidine; TB-1-099). Membranes were prepared from rat brains or human embryonic kidney cells expressing the cloned human dopamine (hDAT), serotonin (hSERT), and norepinephrine (hNET) transporters. beta-(4'-(125)Iodophenyl)tropan-2beta-carboxylic acid methyl ester ([(125)I]RTI-55) binding and other assays followed published procedures. Using rat brain membranes, TB-1-099 weakly inhibited DAT binding (K(i) = 439 nM), was inactive at NET binding ([(3)H]nisoxetine), and partially inhibited SERT binding with an extrapolated plateau ("A" value) of 20%. Similarly, TB-1-099 partially inhibited [(125)I]RTI-55 binding to hSERT with an extrapolated plateau (A value) of 14%. Upon examining the effect of increasing concentrations of TB-1-099 on the apparent K(d) and B(max) of [(125)I]RTI-55 binding to hSERT, we found that TB-1-099 decreased the B(max) in a dose-dependent manner and affected the apparent K(d) in a manner well described by a sigmoid dose-response curve. TB-1-099 increased the K(d) but not to the magnitude expected for a competitive inhibitor. In rat brain synaptosomes, TB-1-099 noncompetitively inhibited [(3)H]5-HT, but not [(3)H]dopamine, uptake. Dissociation experiments indicated that TB-1-099 promoted the rapid dissociation of a small component of [(125)I]RTI-55 binding to hSERT. Association experiments demonstrated that TB-1-099 slowed [(125)I]RTI-55 binding to hSERT in a manner unlike that of the competitive inhibitor indatraline. Viewed collectively, these results support the hypothesis that TB-1-099 allosterically modulates hSERT binding and function.
Nightingale
Barbara
B
Clinical Psychopharmacology Section, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, 5500 Nathan Shock Drive, Baltimore, MD 21224, USA.
Dersch
Christina M
CM
Boos
Terrence L
TL
Greiner
Elisabeth
E
Calhoun
William J
WJ
Jacobson
Arthur E
AE
Rice
Kenner C
KC
Rothman
Richard B
RB
D000818:Animals; D001559:Benzhydryl Compounds / Q000494:pharmacology*; D001667:Binding, Competitive / Q000187:drug effects; D001921:Brain / Q000378:metabolism; D002460:Cell Line; D003042:Cocaine / Q000031:analogs & derivatives / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008562:Membrane Glycoproteins / Q000187:drug effects*; D026901:Membrane Transport Proteins / Q000187:drug effects*; D009419:Nerve Tissue Proteins / Q000187:drug effects*; D018377:Neurotransmitter Agents / Q000378:metabolism; D010879:Piperazines / Q000494:pharmacology*; D010880:Piperidines / Q000494:pharmacology*; D011485:Protein Binding; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000378:metabolism; D050486:Serotonin Plasma Membrane Transport Proteins; D017367:Selective Serotonin Reuptake Inhibitors / Q000494:pharmacology
D001559:Benzhydryl Compounds; D003042:Cocaine; D004298:Dopamine; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D018377:Neurotransmitter Agents; D010879:Piperazines; D010880:Piperidines; D012701:Serotonin; D050486:Serotonin Plasma Membrane Transport Proteins; D017367:Selective Serotonin Reuptake Inhibitors; C504158:4-(2-(bis(4-fluorophenyl)methoxy)ethyl)-1-(2-trifluoromethylbenzyl)piperidine; C493230:SLC6A4 protein, human; C493232:Slc6a4 protein, rat; C069723:2beta-carbomethoxy-3beta-(4-iodophenyl)tropane; C043425:vanoxerine