PUBLICATION
The intracellular domain of homomeric glycine receptors modulates agonist efficacy
- Authors
- Ivica, J., Lape, R., Jazbec, V., Yu, J., Zhu, H., Gouaux, E., Gold, M.G., Sivilotti, L.G.
- ID
- ZDB-PUB-210223-13
- Date
- 2021
- Source
- The Journal of biological chemistry 296: 100387 (Journal)
- Registered Authors
- Keywords
- Ion channel, agonist efficacy, channel activation, glycine receptor, intracellular domain, open probability, patch clamp, pharmacology, single-molecule biophysics, whole-cell current
- MeSH Terms
-
- Amino Acid Sequence
- Animals
- Cells, Cultured
- GABA Agents/pharmacology
- Glycine/pharmacology*
- Glycine Agents/pharmacology
- Humans
- Patch-Clamp Techniques/methods
- Protein Domains
- Receptors, Glycine/agonists*
- Receptors, Glycine/metabolism
- Structure-Activity Relationship
- Taurine/pharmacology*
- Zebrafish
- beta-Alanine/pharmacology*
- gamma-Aminobutyric Acid/pharmacology*
- PubMed
- 33617876 Full text @ J. Biol. Chem.
Citation
Ivica, J., Lape, R., Jazbec, V., Yu, J., Zhu, H., Gouaux, E., Gold, M.G., Sivilotti, L.G. (2021) The intracellular domain of homomeric glycine receptors modulates agonist efficacy. The Journal of biological chemistry. 296:100387.
Abstract
Like other pentameric ligand-gated channels, glycine receptors (GlyRs) contain long intracellular domains (ICDs) between transmembrane helices 3 and 4. Structurally characterized GlyRs are generally engineered to have a very short ICD. We show here that for one such construct, zebrafish GlyREM, the agonists glycine, β-alanine, taurine, and GABA have high efficacy and produce maximum single-channel open probabilities greater than 0.9. In contrast, for full-length human α1 GlyR, taurine and GABA were clearly partial agonists, with maximum open probabilities of 0.46 and 0.09, respectively. We found that the elevated open probabilities in GlyREM are not due to the limited sequence differences between the human and zebrafish orthologs, but rather to replacement of the native ICD with a short tripeptide ICD. Consistent with this interpretation, shortening the ICD in the human GlyR increased the maximum open probability produced by taurine and GABA to 0.90 and 0.70, respectively, but further engineering it to resemble GlyREM (by introducing the zebrafish transmembrane helix 4 and C terminus) had no effect. Furthermore, reinstating the native ICD to GlyREM converted taurine and GABA to partial agonists, with maximum open probabilities of 0.66 and 0.40, respectively. Structural comparison of transmembrane helices 3 and 4 in short- and long-ICD GlyR subunits revealed that ICD shortening does not distort the orientation of these helices within each subunit. This suggests that the effects of shortening the ICD stem from removing a modulatory effect of the native ICD on GlyR gating, revealing a new role for ICD in pentameric ligand-gated channels.
Genes / Markers
Expression
Phenotype
Mutations / Transgenics
Human Disease / Model
Sequence Targeting Reagents
Fish
Orthology
Engineered Foreign Genes
Mapping