posted on 2022-02-23, 16:36authored byAnat Levit Kaplan, Ryan T. Strachan, Joao M. Braz, Veronica Craik, Samuel Slocum, Thomas Mangano, Vanessa Amabo, Henry O’Donnell, Parnian Lak, Allan I. Basbaum, Bryan L. Roth, Brian K. Shoichet
The
5-HT5A receptor (5-HT5AR), for which
no selective agonists and a few antagonists exist, remains the least
understood serotonin receptor. A single commercial antagonist, SB-699551,
has been widely used to investigate the 5-HT5AR function
in neurological disorders, including pain, but this molecule has substantial
liabilities as a chemical probe. Accordingly, we sought to develop
an internally controlled probe set. Docking over 6 million molecules
against a 5-HT5AR homology model identified 5 mid-μM
ligands, one of which was optimized to UCSF678, a 42
nM arrestin-biased partial agonist at the 5-HT5AR with
a more restricted off-target profile and decreased assay liabilities
versus SB-699551. Site-directed mutagenesis supported the docked pose
of UCSF678. Surprisingly, analogs of UCSF678 that lost the 5-HT5AR activity revealed that 5-HT5AR engagement is nonessential for alleviating pain, contrary
to studies with less-selective ligands. UCSF678 and analogs
constitute a selective probe set with which to study the function
of the 5-HT5AR.