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Mol Pharmacol. 1994 Jul;46(1):129-38.

Cyclothiazide differentially modulates desensitization of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor splice variants.

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  • 1Laboratory of Cellular and Molecular Neurophysiology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892.

Abstract

Agonist responses for flip splice variants of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunits GluR-A, -C, and -D are more strongly potentiated by cyclothiazide than are those for the flop forms. Cyclothiazide shows both greater efficacy and higher apparent affinity for potentiation of GluR-Aflip versus GluR-Aflop. Consistent with higher affinity for the flip splice variant, recovery from potentiation by cyclothiazide proceeds 30 times more slowly for GluR-Aflip than for GluR-Aflop. In the presence of 300 microM cyclothiazide a 6-fold leftward shift in the kainate dose-response curve for GluR-Aflip but not GluR-Aflop additionally contributes to a difference in potentiation for these splice variants. Although control responses to glutamate show strong desensitization for both splice variants of GluR-A, in the presence of 100 microM cyclothiazide desensitization is strongly attenuated for GluR-Aflip, whereas for GluR-Aflop desensitization remains pronounced but with a rate of onset slowed 50-fold, compared with control. In heteromeric AMPA receptors formed from GluR-A and GluR-B, the flip splice variants are dominant for controlling both recovery from potentiation of responses to kainate and block of desensitization of responses to glutamate. Our results suggest that the flip/flop module could directly contribute to the binding site for cyclothiazide, raising the possibility that this site is located in an extracellular receptor domain.

PMID:
8058047
[PubMed - indexed for MEDLINE]
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