Visualising functional 5-HT3 receptors containing A and C subunits at or near the cell surface

Isaiah P.L. Abad, Ray L. Fam, Dan Thanh Nguyen, Cameron J. Nowell, Phuc N.H. Trinh, David T. Manallack, Lubna A. Freihat, Jay Chakrabarti, Aamani Jamil, Betty Exintaris, Nor S. Yaakob, Helen R. Irving

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Abstract

Five different subunits of the human serotonin 3 (5-hydroxytrptamine 3; 5-HT3) receptor exist and these are present in both central and peripheral systems. Different subunits alter the efficacy of 5-HT3 receptor antagonists used to treat diarrhoea predominant-irritable bowel syndrome, chemotherapy induced nausea and vomiting and depression. Cell surface arrangement of 5-HT3 receptor complexes and the contribution of C, D and E subunits to receptor function is poorly understood. Here, we examine interactions of A and C subunits using 5-HT3 receptor subunits containing fluorescent protein inserts between the 3rd and 4th transmembrane spanning region. HEK293T cells that do not normally express 5-HT3 receptor subunits, were transiently transfected with A or C or both subunits. Patch clamp experiments show that cells transfected with either fluorescent protein tagged A or A and C subunits generate whole cell currents in response to 5-HT. These findings correlate with the apparent distribution of fluorescent protein tagged A and C subunits at or near cell surfaces detected using TIRF microscopy. In co-transfected cells, the A and C subunits are associated forming AC heteromer complexes at or near the cell surface and a proportion can also form A or C homomers. In conclusion, it is likely that both A homomers and AC heteromers contribute to whole cell currents in response to 5-HT with minimal contribution from C homomers.

Original languageEnglish
Article number110860
Number of pages10
JournalBiomedicine & Pharmacotherapy
Volume132
DOIs
Publication statusPublished - Dec 2020

Keywords

  • 5-HT3 receptor C subunit
  • 5-Hydroxytryptamine receptors
  • HTR3C
  • Ligand-gated ion channels
  • Serotonin receptors

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