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Nat Commun. 2019 Jul 19;10(1):3225. doi: 10.1038/s41467-019-11142-8.

Molecular mechanism of setron-mediated inhibition of full-length 5-HT3A receptor.

Author information

1
Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, 44106-4970, USA.
2
Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
3
Division of CryoEM and Bioimaging, SSRL, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA, 94025, USA.
4
Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, 44106-4970, USA. Sudha.chakrapani@case.edu.
5
Department of Neuroscience, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106-4970, USA. Sudha.chakrapani@case.edu.

Abstract

Serotonin receptor (5-HT3AR) is the most common therapeutic target to manage the nausea and vomiting during cancer therapies and in the treatment of irritable bowel syndrome. Setrons, a class of competitive antagonists, cause functional inhibition of 5-HT3AR in the gastrointestinal tract and brainstem, acting as effective anti-emetic agents. Despite their prevalent use, the molecular mechanisms underlying setron binding and inhibition of 5-HT3AR are not fully understood. Here, we present the structure of granisetron-bound full-length 5-HT3AR solved by single-particle cryo-electron microscopy to 2.92 Å resolution. The reconstruction reveals the orientation of granisetron in the orthosteric site with unambiguous density for interacting sidechains. Molecular dynamics simulations and electrophysiology confirm the granisetron binding orientation and the residues central for ligand recognition. Comparison of granisetron-bound 5-HT3AR with the apo and serotonin-bound structures, reveals key insights into the mechanism underlying 5-HT3AR inhibition.

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