title: Antagonists of GPR35 display high species ortholog selectivity and varying modes of action.
abstract: Variation in pharmacology and function of ligands at species orthologs can be a confounding feature in understanding the biology and role of poorly characterized receptors. Substantial selectivity in potency of a number of GPR35 agonists has previously been demonstrated between human and rat orthologs of this G protein-coupled receptor. Via a bioluminescence resonance energy transfer-based assay of induced interactions between GPR35 and β-arrestin-2, addition of the mouse ortholog to such studies indicated that, as for the rat ortholog, murine GPR35 displayed very low potency for pamoate, whereas potency for the reference GPR35 agonist zaprinast was intermediate between the rat and human orthologs. This pattern was replicated in receptor internalization and G protein activation assays. The effectiveness and mode of action of two recently reported GPR35 antagonists, methyl-5-[(tert-butylcarbamothioylhydrazinylidene)methyl]-1-(2,4-difluorophenyl)pyrazole-4-carboxylate (CID-2745687) and 2-hydroxy-4-[4-(5Z)-5-[(E)-2-methyl-3-phenylprop-2-enylidene]-4-oxo-2-sulfanylidene-1,3-thiazolidin-3-yl]butanoylamino)benzoic acid (ML-145), were investigated. Both CID-2745687 and ML-145 competitively inhibited the effects at human GPR35 of cromolyn disodium and zaprinast, two agonists that share an overlapping binding site. By contrast, although ML-145 also competitively antagonized the effects of pamoate, CID-2745687 acted in a noncompetitive fashion. Neither ML-145 nor CID-2745687 was able to effectively antagonize the agonist effects of either zaprinast or cromolyn disodium at either rodent ortholog of GPR35. These studies demonstrate that marked species selectivity of ligands at GPR35 is not restricted to agonists and considerable care is required to select appropriate ligands to explore the function of GPR35 in nonhuman cells and tissues.
authors.affiliation: Molecular Pharmacology Group, Institute of Molecular, Cell, and Systems Biology, College of Medical, Veterinary, and Life Sciences, University of Glasgow, Glasgow, United Kingdom.
authors.forename: Laura
authors.initials: L
authors.lastname: Jenkins
authors.forename: Nicholas
authors.initials: N
authors.lastname: Harries
authors.forename: Jennifer E
authors.initials: JE
authors.lastname: Lappin
authors.forename: Amanda E
authors.initials: AE
authors.lastname: MacKenzie
authors.forename: Zaynab
authors.initials: Z
authors.lastname: Neetoo-Isseljee
authors.forename: Craig
authors.initials: C
authors.lastname: Southern
authors.forename: Edward G
authors.initials: EG
authors.lastname: McIver
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Nicklin
authors.forename: Debra L
authors.initials: DL
authors.lastname: Taylor
authors.forename: Graeme
authors.initials: G
authors.lastname: Milligan
mesh_terms: D000636:Aminosalicylic Acids / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D019390:Arrestins / Q000378:metabolism; D060807:Bioluminescence Resonance Energy Transfer Techniques; D018929:Cell Culture Techniques; D004305:Dose-Response Relationship, Drug; D054333:Drug Partial Agonism; D057809:HEK293 Cells; D006801:Humans; D006835:Hydrazones / Q000737:chemistry / Q000494:pharmacology*; D008024:Ligands; D051379:Mice; D008856:Microscopy, Fluorescence; D015394:Molecular Structure; D011485:Protein Binding; D051381:Rats; D043562:Receptors, G-Protein-Coupled / Q000819:agonists / Q000037:antagonists & inhibitors* / Q000235:genetics; D013045:Species Specificity; D053778:Thiazolidines / Q000737:chemistry / Q000494:pharmacology*; D013890:Thiourea / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D014162:Transfection; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins
chemical_list: C577640:2-hydroxy-4-(4-(5-(2-methyl-3-phenylprop-2-enylidene)-4-oxo-2-sulfanylidene-1,3-thiazolidin-3-yl)butanoylamino)benzoic acid; C000605254:ARRB2 protein, human; D000636:Aminosalicylic Acids; C000605258:Arrb2 protein, mouse; C000605257:Arrb2 protein, rat; D019390:Arrestins; C111379:GPR35 protein, human; C513986:GPR35 protein, mouse; C513985:GPR35 protein, rat; D006835:Hydrazones; D008024:Ligands; D043562:Receptors, G-Protein-Coupled; D053778:Thiazolidines; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins; C577639:methyl 5-((tert-butylcarbamothioylhydrazinylidene)methyl)-1-(2,4-difluorophenyl)pyrazole-4-carboxylate; D013890:Thiourea