Fig. 2: Indications of VLZ as an allosteric inhibitor of SERT WT.

a Saturation uptake experiments for [³H]5-HT transport as a function of increasing VLZ concentrations (0–15 nM) are compatible with a non-competitive inhibition for VLZ. Colors of lines and symbols represent various concentrations of VLZ defined in legend. The V_MAX for [³H]5-HT decreases with increasing VLZ concentration. Data are shown in percent of 5-HT V_MAX in the absence of VLZ (V_MAX in the absence of VLZ is 4899 ± 312 cpm/min/10⁵ cells). The K_M-value for 5-HT is largely unaffected by increasing VLZ concentrations (Supplementary Table 2). Non-specific [³H]5-HT binding was assessed in the presence of 1 µM paroxetine. Experiments are performed in triplicates on intact COS-7 cells transiently expressing SERT, n = 3–8. b Representative experiment for the assessment of VLZ allosteric potency determined by its influence on [³H]IMI dissociation. The slope for [³H]IMI dissociation ranges from 0.528 ± 0.012 min⁻¹ in the absence of VLZ (ctrl, black line) to 0.045 ± 0.019 min⁻¹ in the presence of 1120 nM VLZ (blue line). Data are converted to the dose-response curve in (b) to determine the allosteric potency (see Methods). c Allosteric potency of VLZ determined as concentration-dependent inhibition of [³H]IMI and [³H]S-CIT dissociation. The radioligands were prebound to SERT WT prior to the addition of VLZ in the indicated concentrations. Data are plotted as the effect of VLZ on the [³H]IMI and [³H]S-CIT dissociation rate (k_[VLZ]) relative to the rate in the absence of VLZ (k_[ctrl]). The allosteric potency of VLZ is ~17-fold higher in the presence of prebound [³H]IMI (circles, tan) relative to [³H]S-CIT (triangles, brown), with IC₅₀ = 14.1 [11.8; 16.8] and 250 [203; 307] nM, respectively (mean [S.E. interval]), n = 10 ([³H]IMI) and 7 ([³H]S-CIT). Data are shown as means ± S.E. (error bars). [³H]cmpd: [³H]compound (being either [³H]IMI or [³H]S-CIT). Source data are provided as a Source Data file.