Back to Search
Start Over
Modular Design of Cys-loop Ligand-gated Ion Channels: Functional 5-HT3 and GABA ρ1 Receptors Lacking the Large Cytoplasmic M3M4 Loop
- Source :
- The Journal of General Physiology
- Publication Year :
- 2008
- Publisher :
- Rockefeller University Press, 2008.
-
Abstract
- Cys-loop receptor neurotransmitter-gated ion channels are pentameric assemblies of subunits that contain three domains: extracellular, transmembrane, and intracellular. The extracellular domain forms the agonist binding site. The transmembrane domain forms the ion channel. The cytoplasmic domain is involved in trafficking, localization, and modulation by cytoplasmic second messenger systems but its role in channel assembly and function is poorly understood and little is known about its structure. The intracellular domain is formed by the large (>100 residues) loop between the α-helical M3 and M4 transmembrane segments. Putative prokaryotic Cys-loop homologues lack a large M3M4 loop. We replaced the complete M3M4 loop (115 amino acids) in the 5-hydroxytryptamine type 3A (5-HT3A) subunit with a heptapeptide from the prokaryotic homologue from Gloeobacter violaceus. The macroscopic electrophysiological and pharmacological characteristics of the homomeric 5-HT3A-glvM3M4 receptors were comparable to 5-HT3A wild type. The channels remained cation-selective but the 5-HT3A-glvM3M4 single channel conductance was 43.5 pS as compared with the subpicosiemens wild-type conductance. Coexpression of hRIC-3, a protein that modulates expression of 5-HT3 and acetylcholine receptors, significantly attenuated 5-HT–induced currents with wild-type 5-HT3A but not 5-HT3A-glvM3M4 receptors. A similar deletion of the M3M4 loop in the anion-selective GABA-ρ1 receptor yielded functional, GABA-activated, anion-selective channels. These results imply that the M3M4 loop is not essential for receptor assembly and function and suggest that the cytoplasmic domain may fold as an independent module from the transmembrane and extracellular domains.
- Subjects :
- Serotonin
Patch-Clamp Techniques
Physiology
Molecular Sequence Data
Sodium Chloride
Biology
Cyanobacteria
Article
Cell Line
Membrane Potentials
Diltiazem
Mice
Xenopus laevis
03 medical and health sciences
0302 clinical medicine
Animals
Humans
Picrotoxin
Serotonin 5-HT3 Receptor Antagonists
Amino Acid Sequence
gamma-Aminobutyric Acid
Ion channel
030304 developmental biology
Acetylcholine receptor
0303 health sciences
Transmembrane channels
Binding Sites
Sequence Homology, Amino Acid
Intracellular Signaling Peptides and Proteins
Lidocaine
Articles
Light-gated ion channel
Ondansetron
6. Clean water
Transmembrane protein
Transmembrane domain
Receptors, GABA-B
Biochemistry
Mutation
Oocytes
Biophysics
Ligand-gated ion channel
Female
Receptors, Serotonin, 5-HT3
GABA-B Receptor Antagonists
030217 neurology & neurosurgery
Cys-loop receptors
Subjects
Details
- ISSN :
- 15407748 and 00221295
- Volume :
- 131
- Database :
- OpenAIRE
- Journal :
- Journal of General Physiology
- Accession number :
- edsair.doi.dedup.....41846b8ef8677685aa0a63542455b01c