Two mechanisms of action of the adamantane derivative IEM-1460 at human AMPA-type glutamate receptors.
1. Antagonizing glutamatergic neurotransmission by blockade of AMPA-type glutamate receptors (GluR) is a promising pharmacological strategy for neuroprotection in neurodegenerative diseases and acute treatment of stroke. 2. We investigated the interaction of the adamantane derivative IEM-1460 with human wild-type and mutant AMPA-type GluR channels. Different recombinant homooligomeric human AMPA-type GluR channels and a rat nondesensitizing mutant GluR (GluR2 L504Y) channel were expressed in HEK293 cells and investigated using the patch-clamp technique in combination with ultrafast agonist application. 3. When IEM-1460 was coapplied with glutamate, an open channel block mechanism was observed at slow desensitizing GluR2 flip (>/=0.1 mM IEM-1460) and nondesensitizing GluR2 L504Y channels (>/=1 microM IEM-1460). 4. A competitive block of AMPA-type channels was observed with IC(50) values for the dose block curves of 0.1 mM IEM-1460 at human unmutated and 10 microM IEM-1460 at mutant GluR channels. 5. Nondesensitizing GluR2 L504Y channels were used to further characterize the block mechanism. After equilibration with the agonist, a current decay upon coapplication of glutamate and IEM-1460 was observed. The recovery from block was independent of the glutamate and IEM-1460 concentration. The extent of current inhibition as well as the time constant of current decay upon addition of the blocker to the test solution were dependent on agonist concentration; this strongly points to an additional competitive-like block mechanism of IEM-1460 at human AMPA-type GluR channels. 6. The data were interpreted in the frame of a molecular scheme with two binding sites of IEM-1460 at the receptor, one at the unliganded resting and the other at the fully liganded open state of the channels.
Schlesinger
Friedrich
F
Neurological Department of the Medical School of Hannover, Karl-Neuberg Str. 1, 30623 Hannover, Germany. Schlesinger.Friedrich@mh-hannover.de
Tammena
Derk
D
Krampfl
Klaus
K
Bufler
Johannes
J
D000218:Adamantane / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000494:pharmacology*; D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D018691:Excitatory Amino Acid Antagonists / Q000138:chemical synthesis / Q000494:pharmacology*; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D018408:Patch-Clamp Techniques; D051381:Rats; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors* / Q000235:genetics
D018691:Excitatory Amino Acid Antagonists; C110702:IEM 1460; D018091:Receptors, AMPA; D000218:Adamantane