Atomic force microscopy reveals the stoichiometry and subunit arrangement of 5-HT3 receptors

The 5-HT 3 receptor is a cation-selective ligand-gated ion channel of the Cys-loop superfamily. The receptor is an important therapeutic target, with receptor antagonists being widely used as antiemetics in cancer therapy. The two known receptor subunits, A and B, form homomeric 5-HT 3A receptors an...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2005-08, Vol.102 (35), p.12595-12600
Main Authors: Barrera, Nelson P, Herbert, Paul, Henderson, Robert M, Martin, Ian L, Edwardson, J Michael
Format: Article
Language:English
Subjects:
Animals
Antibodies, Monoclonal
Antigen-Antibody Complex - chemistry
Biological Sciences
Cancer
Cell Line
Humans
Immunoglobulins
In Vitro Techniques
Mice
Microscopy
Microscopy, Atomic Force
Multiprotein Complexes
Protein Engineering
Protein Subunits
Receptors, Serotonin, 5-HT3 - chemistry
Receptors, Serotonin, 5-HT3 - genetics
Receptors, Serotonin, 5-HT3 - immunology
Recombinant Proteins - chemistry
Recombinant Proteins - genetics
Recombinant Proteins - immunology
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Summary:The 5-HT 3 receptor is a cation-selective ligand-gated ion channel of the Cys-loop superfamily. The receptor is an important therapeutic target, with receptor antagonists being widely used as antiemetics in cancer therapy. The two known receptor subunits, A and B, form homomeric 5-HT 3A receptors and heteromeric 5-HT 3A/B receptors. The heteromeric receptor has the higher single-channel conductance and more closely mimics the properties of the native receptor. We have used atomic force microscopy to study the architecture of 5-HT 3A and 5-HT 3A/B receptors. We engineered different epitope tags onto the A- and B-subunits and imaged receptors that were doubly liganded by anti-epitope antibodies. We found that, for the 5-HT 3A/B receptor, the distribution of angles between antibodies against the A-subunit had a single peak at ≈144°, whereas the distribution for antibodies against the B-subunit had two peaks at ≈72° and 144°. Our results indicate that the subunit stoichiometry is 2A:3B and that the subunit arrangement around the receptor rosette is B-B-A-B-A. This arrangement may account for the difference between the agonist Hill coefficients and the single-channel conductances for the two types of receptor. ligand-gated ion channel receptor structure
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.0503253102