کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5548827 | 1556592 | 2017 | 10 صفحه PDF | دانلود رایگان |
- A chimeric GLIC/GABAÏ pentameric ligand gated ion channel was made and studied.
- Like GABAÏ, chimeric channels were Clâ conducting and inhibited by anesthetics.
- Anesthetic modulation of current is mediated locally in domain where it binds.
- Neurosteroid modulation of chimeric channels was swapped compare to GABAÏ.
- Interactions between extracellular and channel domains shape neurosteroid actions.
Pentameric ligand-gated ion channels (pLGICs) are the targets of several clinical and endogenous allosteric modulators including anesthetics and neurosteroids. Molecular mechanisms underlying allosteric drug modulation are poorly understood. Here, we constructed a chimeric pLGIC by fusing the extracellular domain (ECD) of the proton-activated, cation-selective bacterial channel GLIC to the transmembrane domain (TMD) of the human Ï1 chloride-selective GABAAR, and tested the hypothesis that drug actions are regulated locally in the domain that houses its binding site. The chimeric channels were proton-gated and chloride-selective demonstrating the GLIC ECD was functionally coupled to the GABAÏ TMD. Channels were blocked by picrotoxin and inhibited by pentobarbital, etomidate and propofol. The point mutation, Ï TMD W328M, conferred positive modulation and direct gating by pentobarbital. The data suggest that the structural machinery mediating general anesthetic modulation resides in the TMD. Proton-activation and neurosteroid modulation of the GLIC-Ï chimeric channels, however, did not simply mimic their respective actions on GLIC and GABAÏ revealing that across domain interactions between the ECD and TMD play important roles in determining their actions. Proton-induced current responses were biphasic suggesting that the chimeric channels contain an additional proton sensor. Neurosteroid modulation of the GLIC-Ï chimeric channels by the stereoisomers, 5α-THDOC and 5β-THDOC, were swapped compared to their actions on GABAÏ indicating that positive versus negative neurosteroid modulation is not encoded solely in the TMD nor by neurosteroid isomer structure but is dependent on specific interdomain connections between the ECD and TMD. Our data reveal a new mechanism for shaping neurosteroid modulation.
Journal: Neuropharmacology - Volume 125, October 2017, Pages 343-352