Kinetic mechanism of dopamine transporter interaction with 1-(2-(bis-(4-fluorophenyl)methoxy)ethyl)-4-(3-phenylpropyl)piperazine (GBR 12909).
Interaction of piperazine-based dopamine transporter inhibitor GBR12909 with rat dopamine transporters has been studied by means of competition kinetics analysis, employing [(3)H]PE2I as the reporter ligand. It has been found that GBR12909 is capable of inducing so-called "slow isomerization step" upon binding to DAT, probably consisting of a conformational change in the transporter protein. The mechanism exhibited by GBR12909 appears to be similar to the mechanism of PE2I that has been reported earlier and also confirms previous observations for GBR12783 made by Do-Rego and co-workers using dopamine uptake data. It appears that the isomerization phenomenon previously described for PE2I is not limited to tropane-based DAT inhibitors, but is, in fact, a general property of dopamine transporter protein, similar to "isomerization" process reported previously for G-protein coupled receptors. The rapid first step of association of the GBR 12909 is characterized by the equilibrium constant K(L)=34+/-11nM and the second slow step by k(i)=0.033+/-0.005s(-1).
Stepanov
Vladimir
V
Institute of Chemistry, University of Tartu, Jakobi 2, Tartu 51014, Estonia. vladimir.stepanov@ut.ee
Järv
Jaak
J
D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects / Q000502:physiology; D001921:Brain / Q000187:drug effects* / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism; D050483:Dopamine Plasma Membrane Transport Proteins / Q000187:drug effects* / Q000378:metabolism*; D018765:Dopamine Uptake Inhibitors / Q000494:pharmacology*; D005260:Female; D007536:Isomerism; D007700:Kinetics; D015394:Molecular Structure; D010879:Piperazines / Q000494:pharmacology*; D011487:Protein Conformation / Q000187:drug effects; D011869:Radioligand Assay; D051381:Rats; D017208:Rats, Wistar; D013347:Subcellular Fractions; D013997:Time Factors
D050483:Dopamine Plasma Membrane Transport Proteins; D018765:Dopamine Uptake Inhibitors; D010879:Piperazines; C043425:vanoxerine; D004298:Dopamine