Activation and modulation of concatemeric GABA-A receptors expressed in human embryonic kidney cells

Gustav Akk, Ping Li, John Bracamontes, Joe Henry Steinbach

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


We have employed whole-cell and single-channel electrophysiology to examine the kinetic and pharmacological properties of GABA-A receptors consisting of γ2L-β2-α1 and β2-α1 subunit concatemeric constructs expressed in human embryonic kidney cells. Concatemeric receptors activated by GABA exhibited the same single-channel conductance, channel opening rate constant, and basic open- and closed-time properties as receptors containing free subunits. However, the whole-cell GABA dose-response and the single-channel effective opening rate curves were shifted to higher GABA concentrations, suggesting that the concatemeric receptors have a lower affinity to GABA. Pharmacological tests demonstrated that the concatemeric receptors were potentiated by pentobarbital, diazepam, and the neurosteroid (3α,5α)-3-hydroxypregnan-20-one (3α5αP), and were insensitive to Zn2+. Selective introduction of the α1Q241L mutation, previously shown to abolish α1β2γ2L channel potentiation by neurosteroids, into one of the two concatemeric constructs had a relatively small effect on receptor activation by GABA or macroscopic potentiation by the neurosteroid 3α5αP. Single-channel measurements showed that the kinetic mechanism of action of the steroid is unchanged when the mutation is introduced to the γ2L-β2-α1 concatemer. We infer that a single wild-type α subunit is capable of mediating the full set of kinetic effects in the presence of steroids. Introduction of the α1Q241W mutation, previously shown to mimic the effect of the steroid on α1β2γ2L channels, selectively into either concatemeric construct altered the mode of activity elicited by P4S, but the presence of mutations in both α subunits was required to affect open-time distributions. The data indicate that the α1Q241W mutation acts as a partial steroid modulator.

Original languageEnglish
Pages (from-to)1400-1411
Number of pages12
JournalMolecular pharmacology
Issue number6
StatePublished - Jun 2009


Dive into the research topics of 'Activation and modulation of concatemeric GABA-A receptors expressed in human embryonic kidney cells'. Together they form a unique fingerprint.

Cite this