Mechanism-Based Approach to the Successful Prevention of Cocaine Inhibition of the Neuronal (3
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- 作者：Arcadius V. Krivoshein and George P. Hess
- 刊名：Biochemistry
- 出版年：2004
- 出版时间：January 20, 2004
- 年：2004
- 卷：43
- 期：2
- 页码：481 - 489
- 全文大小：118K
- 年卷期：v.43,no.2(January 20, 2004)
- ISSN：1520-4995
文摘
The nicotinic acetylcholine receptor (nAChR) belongs to a family of five channel-formingproteins that regulate communication between the approximately 1012 cells of the nervous system. Aminimum mechanism of inhibition of the muscle-type nAChR (1) by the noncompetitive inhibitors cocaineand MK-801 [(+)-dizocilpine, an anticonvulsant] indicated they bind to a regulatory site, with higheraffinity for the closed-channel form than for the open-channel form, thus shifting the equilibrium towardthe closed-channel form and inhibiting receptor function. The mechanism predicts that compounds thatbind to this regulatory site with equal or higher affinity for the open-channel conformation than for theclosed-channel conformation will prevent receptor inhibition (1). Does a neuronal form of the receptorbehave similarly? The mechanism of inhibition of the neuronal nAChR by cocaine and MK-801 usingrapid chemical kinetic techniques was investigated. The 
3
4 nAChR stably expressed in HEK 293 cellswas used in these investigations. Whole-cell currents originated from a major and minor nAChR isoform.Only the major isoform has been characterized. For the dominant, rapidly desensitizing isoform, thecarbamoylcholine dissociation constant for the site controlling receptor activation, Kd, is 2 mM; the channel-opening equilibrium constant, 
-1, is 4; and the dominant desensitization rate constant, k34, is 20 s-1.Cocaine inhibits the receptor noncompetitively, with an apparent KI of 84 and 26 
M at high and lowcarbamoylcholine concentrations, at which concentrations the receptor is mainly in the open- or closed-channel form, respectively. Similar results were obtained with MK-801. A combinatorially synthesizedRNA ligand and a cocaine analogue alleviated cocaine inhibition of this neuronal receptor.
34 nAChR stably expressed in HEK 293 cellswas used in these investigations. Whole-cell currents originated from a major and minor nAChR isoform.Only the major isoform has been characterized. For the dominant, rapidly desensitizing isoform, thecarbamoylcholine dissociation constant for the site controlling receptor activation, Kd, is 2 mM; the channel-opening equilibrium constant, -1, is 4; and the dominant desensitization rate constant, k34, is 20 s-1.Cocaine inhibits the receptor noncompetitively, with an apparent KI of 84 and 26 M at high and lowcarbamoylcholine concentrations, at which concentrations the receptor is mainly in the open- or closed-channel form, respectively. Similar results were obtained with MK-801. A combinatorially synthesizedRNA ligand and a cocaine analogue alleviated cocaine inhibition of this neuronal receptor.