The α1 and α6 Subunits Can Coexist in the Same Cerebellar GABAA Receptor Maintaining Their Individual Benzodiazepine‐Binding Specificities

ZU Khan, A Gutiérrez, AL De Blas - Journal of neurochemistry, 1996 - Wiley Online Library
ZU Khan, A Gutiérrez, AL De Blas
Journal of neurochemistry, 1996Wiley Online Library
Two GABAA receptor subunit‐specific antibodies anti‐α6 and anti‐α1 have been used for
elucidating the relationship between the presence of α1 and/or α6 subunits in the cerebellar
GABAA receptors and the benzodiazepine‐binding specificity. Receptor
immunoprecipitation with the subunit‐specific antibodies shows that 39% of the cerebellar
GABAA receptors have α6, whereas 76% of the receptors have α1 as determined by [3H]
muscimol binding. Results show that 42–45% of the receptors having α6 also have α1 …
Abstract
Two GABAA receptor subunit‐specific antibodies anti‐α6 and anti‐α1 have been used for elucidating the relationship between the presence of α1 and/or α6 subunits in the cerebellar GABAA receptors and the benzodiazepine‐binding specificity. Receptor immunoprecipitation with the subunit‐specific antibodies shows that 39% of the cerebellar GABAA receptors have α6, whereas 76% of the receptors have α1 as determined by [3H]muscimol binding. Results show that 42–45% of the receptors having α6 also have α1, whereas 13–15% of the receptors that contain α1 also have α6. The immunoprecipitation results as well as immunopurification and immunoblotting experiments reveal the existence of three types of cerebellar GABAA receptors; i.e., one has both α1 and α6 subunits, a second type has α1 but not α6, and a third type has α6 but not α1 subunits. The results also show that receptors where α1 and α6 subunits coexist have two pharmacologically different benzodiazepine‐binding properties, each associated with a different α subunit. The α1 subunit contributes the high‐affinity binding of [3H]Ro 15‐1788 (flumazenil) and the diazepam‐sensitive binding of [3H]Ro 15‐4513. The α6 subunit contributes the diazepam‐insensitive binding of [3H]Ro 15‐4513, but it does not bind [3H]Ro 15‐1788 with high affinity. Thus, in the cerebellar α1–α6 GABAA receptors, there is no dominance of the pharmacology of one α subunit over the other.
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