Abstract |
Binding sites for 2 beta-carbomethoxy-3 beta-(4-fluorophenyl)[3H]tropane ([3H] WIN 35,428) on the human dopamine transporter expressed in C6 glioma cells were alkylated with N-ethylmaleimide (NEM), and the protective potency of the blockers cocaine, N[1-(2-benzo[b]thiophenyl) cyclohexyl] piperidine (BTCP), and benztropine, and of the substrates dopamine, d-amphetamine, and norepinephrine was measured. In general, the protective potency was lower (at least 4-5 times) than the potency in inhibiting [3H] WIN 35,428 binding with the compounds present under the same experimental conditions used for the NEM alkylation. However, the disparity was substantially greater for all substrates tested (23- to 44-fold) than for the blockers (4- to 11-fold), especially cocaine (5-fold) and BTCP (4-fold). Benztropine took an intermediate place (11-fold) between cocaine (5-fold) and BTCP (4-fold), on the one hand, and dopamine (23-fold), on the other hand. [3H] WIN 35,428 binding was best described by a one-site model under the present conditions. The results are discussed in terms of models involving blocker-induced conformational changes and overlapping nonidentical binding domains for blockers and substrates.
|
Authors | M E Reith, C Xu, L L Coffey |
Journal | Biochemical pharmacology
(Biochem Pharmacol)
Vol. 52
Issue 9
Pg. 1435-46
(Nov 08 1996)
ISSN: 0006-2952 [Print] England |
PMID | 8937455
(Publication Type: Comparative Study, Journal Article, Research Support, U.S. Gov't, P.H.S.)
|
Chemical References |
- Carrier Proteins
- Dopamine Plasma Membrane Transport Proteins
- Dopamine Uptake Inhibitors
- Membrane Glycoproteins
- Membrane Transport Proteins
- Nerve Tissue Proteins
- (1R-(exo,exo))-3-(4-fluorophenyl)-8-methyl-8- azabicyclo(3.2.1)octane-2-carboxylic acid, methyl ester
- Cocaine
- Ethylmaleimide
- Dopamine
|
Topics |
- Animals
- Binding Sites
- Carrier Proteins
(antagonists & inhibitors, genetics, metabolism)
- Cell Membrane
(metabolism)
- Cloning, Molecular
- Cocaine
(analogs & derivatives, metabolism)
- Dopamine
(metabolism)
- Dopamine Plasma Membrane Transport Proteins
- Dopamine Uptake Inhibitors
(metabolism)
- Ethylmaleimide
(pharmacology)
- Humans
- Kinetics
- Membrane Glycoproteins
- Membrane Transport Proteins
- Nerve Tissue Proteins
- Rats
- Transfection
- Tumor Cells, Cultured
|