Figure 1. Drugs that inhibit NAADP-evoked Ca²⁺ release block MERS translocation.

A, Ca²⁺ release in sea urchin egg homogenate as resolved by fluo-3 fluorescence measurements. Ca²⁺ liberation was measured in the absence (solid circles, top trace) or presence of fangchinoline (open circles, 10μM) in response to NAADP (blue, 70nM), IP₃ (red, 200nM) or cADPR (green, 100nM). Data represent values from a minimum of three independent experiments and are expressed as mean ± SEM. B, correlation plot comparing the extent of inhibition of NAADP- (blue) IP₃- (red) or cADPR-evoked Ca²⁺ release (green) observed with individual ligands (10μM) correlated with the extent of inhibition of MERS-pseudovirus translocation evoked by the same ligands (at the same concentration, 10μM). None of these tested ligands evoked Ca²⁺ release by themselves. Solid (NAADP) and dotted lines (IP₃, cADPR) represent linear regression of datapoints. Ligand key: 1=DMSO, 2=Cycleanine, 3=Tubocurarine, 4=Nimodipine, 5=Procaine, 6=Chondocurine, 7=Benzocaine, 8=Hernandezine, 9=Berbamine, 10=Nicardipine, 11=Verapamil, 12=Tetrandrine, 13=Fangchinoline, 14=Amitriptyline, 15=Loperamide, 16=Ned-19, 17=Bafilomycin, 18=U18666A, 19=YM201636, 20=Fluoxetine, 21=Citalopram, 22=Desipramine, 23=Siramesine. MERS-pseudovirus infectivity was measured using a luciferase-based cell entry assay, assay methodology and inhibition of NAADP-evoked Ca²⁺ shown in this figure are described in detail in the companion paper [25].