VUF10166, a novel compound with differing activities at 5-HT₃A and 5-HT₃AB receptors.
The actions of a novel, potent 5-HT₃ receptor ligand, [2-chloro-(4-methylpiperazine-1-yl)quinoxaline (VUF10166)], were examined at heterologously expressed human 5-HT₃A and 5-HT₃AB receptors. VUF10166 displaced [³H]granisetron binding to 5-HT₃A receptors expressed in human embryonic kidney cells with high affinity (K(i) = 0.04 nM) but was less potent at 5-HT₃AB receptors (K(i) = 22 nM). Dissociation of [³H]granisetron in the presence of VUF10166 was best fit with a single time constant (t(1/2) = 53 min) at 5-HT₃A receptors, but with two time constants (t(1/2) = 55 and 2.4 min) at 5-HT₃AB receptors. Electrophysiological studies in oocytes revealed that VUF10166 inhibited 5-HT-induced responses at 5-HT₃A receptors at nanomolar concentrations, but inhibition and recovery were too slow to determine an IC₅₀. At 5-HT₃AB receptors, inhibition and recovery were faster, yielding an IC₅₀ of 40 nM. Cysteine substitutions in the complementary (-), but not the principal (+), face of the 5-HT₃B subunit produced heteromeric receptors in which the actions of VUF10166 resembled those at homomeric receptors. At 5-HT₃A receptors, VUF10166 at higher concentrations also behaved as a partial agonist (EC₅₀ = 5.2 μM; R(max) = 0.24) but did not elicit significant responses at 5-HT₃AB receptors at ≤100 μM. Thus, we propose that VUF10166 binds to the common A+A- site of both receptor types and to a second A+B- modulatory site in the heteromeric receptor. The ability of VUF10166 to distinguish between 5-HT₃A and 5-HT₃AB receptors could help evaluate differences between these receptor types and has potential therapeutic value.
Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom.
A J
AJ
Thompson
M H P
MH
Verheij
I J P
IJ
de Esch
S C R
SC
Lummis
D000818:Animals; D002478:Cells, Cultured; D005260:Female; D017829:Granisetron / Q000494:pharmacology; D057809:HEK293 Cells; D006801:Humans; D007553:Isotope Labeling / Q000379:methods; D008024:Ligands; D009154:Mutation / Q000187:drug effects / Q000235:genetics; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism; D010880:Piperidines / Q000494:pharmacology*; D011485:Protein Binding / Q000187:drug effects; D011810:Quinoxalines / Q000494:pharmacology*; D044406:Receptors, Serotonin, 5-HT3 / Q000235:genetics* / Q000378:metabolism*; D058827:Serotonin 5-HT3 Receptor Agonists / Q000494:pharmacology; D058831:Serotonin 5-HT3 Receptor Antagonists / Q000494:pharmacology; D014982:Xenopus laevis / Q000378:metabolism
D017829:Granisetron; D008024:Ligands; D010880:Piperidines; D011810:Quinoxalines; D044406:Receptors, Serotonin, 5-HT3; D058827:Serotonin 5-HT3 Receptor Agonists; D058831:Serotonin 5-HT3 Receptor Antagonists; C574388:2-chloro-(4-methylpiperazine-1-yl)quinoxaline