RT Journal Article
SR Electronic
T1 Identification of Overlapping, but Differential Binding Sites for the High-affinity CXCR3 Antagonists NBI-74330 and VUF11211
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP mol.113.088633
DO 10.1124/mol.113.088633
A1 Danny J Scholten
A1 Luc Roumen
A1 Maikel Wijtmans
A1 Marlies CA Verkade-Vreeker
A1 Hans Custers
A1 Michael Lai
A1 Daniela de Hooge
A1 Meritxell Canals
A1 Iwan JP de Esch
A1 Martine J Smit
A1 Chris de Graaf
A1 Rob Leurs
YR 2013
UL http://molpharm.aspetjournals.org/content/early/2013/10/30/mol.113.088633.abstract
AB Chemokine receptor CXCR3 and/or its main three ligands CXCL9, CXCL10, and CXCL11 are highly upregulated in a variety of diseases. As such, considerable efforts have been made to develop small-molecule receptor CXCR3 antagonists, yielding distinct chemical classes of antagonists blocking binding and/or function of CXCR3 chemokines. Although it is suggested that these compounds bind in an allosteric fashion, so far no evidence has been provided regarding the molecular details of their interaction with CXCR3. Using site-directed mutagenesis complemented with in silico homology modeling, we report the binding modes of two high-affinity CXCR3 antagonists of distinct chemotypes: VUF11211 (piperazinyl-piperidine) with a rigid elongated structure containing two basic groups, and NBI-74330 (8-azaquinazolinone) without any basic group. Here we show that NBI-74330 is anchored in the transmembrane minor pocket lined by helices 2 (W2.60, D2.63), 3 (F3.32), and 7 (S7.39, Y7.43), whereas VUF11211 extends from the minor pocket into the major pocket of the transmembrane domains, located between residues in helices 1 (Y1.39), 2 (W2.60), 3 (F3.32), 4 (D4.60), 6 (Y6.51), and 7 (S7.39, Y7.43). Mutation of these residues did not affect CXCL11 binding significantly, confirming the allosteric nature of the interaction of these small molecules with CXCR3. Moreover, the model derived from our in silico-guided studies fits well with the already published structure-activity relationship data on these ligands. Altogether, in this study we show overlapping, yet different binding sites for two high-affinity CXCR3 antagonists, which offer new opportunities for the structure-based design of allosteric modulators for CXCR3.