Fig. 4. Transfer of plerixafor to CXCR3 (also) reveals partial agonism.

a Binding pocket of WT CXCR3 (left) and K300A-S304E mutant (right) shown from the extracellular side. Residues involved in plerixafor and AMD11070 binding in CXCR4 (Fig. 3) are shown as sticks. K300 and S304 in WT are mutated to A300 and E304, respectively. The wild-type CXCR3 model was retrieved from the GPCR-HGmod database⁷⁶. Residues are colored according to side chains; red = acidic residue, blue = basic residue, yellow = aromatic residue, green = polar residue. b Antagonistic effect of plerixafor and AMD11070 on CXCL11-induced CXCR3 G protein activity. Measured by inositol triphosphate (IP3) accumulation in HEK293 cells transiently transfected with WT CXCR3 or CXCR3[K300A-S304E] and the chimeric G protein Gqi4myr and stimulated with 10 nM CXCL11. Data of plerixafor previously published in ref. ⁴⁸. Data are shown with %mean ± SEM of duplicates from 3 independent experiments, CXCR3 wt (black circle) and CXCR3 [K300A-S304E] stimulated with plerixafor (red square) or AMD11070 (white square). c Agonistic effect of plerixafor and AMD11070 on CXCR3 G protein activity compared to CXCL10 and CXCL11. Measured by inositol triphosphate (IP3) accumulation in HEK293 cells transiently transfected with CXCR3 WT or CXCR3[K300A-S304E] and the chimeric G protein Gqi4myr. The data were normalized to the maximal recruitment levels by CXCL11 on the two receptors and presented with %mean ± SEM of duplicates from at least three indepependent experiments. d Agonistic effect of plerixafor and AM11070 in β-arrestin2 recruitment upon CXCR3 activation compared to CXCL10 and CXCL11. Measured by the BRET-based arrestin recruitment assay in CHO cells transiently transfected with WT CXCR3 or CXCR3[K300A-S304E], Rluc8-Arrestin3, and mem-linker-citrine-SH3 constructs. The data were normalized to the maximal recruitment levels by CXCL11 on the two receptors and presented with %mean ± SEM of duplicates from five independent experiments. In c and d data are presented as CXCL11 (gray square), CXCL10 (black square), plerixafor (red square), and AMD11070 (white square).