Figure 7. Myc-tag accessibility increases after intracellular cleavage of syntaxin.
(a) Cells expressing syntaxin-myc or syx-ΔS-myc were co-transfected (BoNT/C1) or not (control) with the light chain of botulinum neurotoxin C1 (BoNT/C1) fused to GFP. One day after transfection cells were fixed, stained for myc and imaged for quantification of the myc- (a) and GFP-intensity (not shown). Images are shown at the same scalings. (b) Staining quantified from outlined cells. While BoNT/C1 did not change the size of syx-ΔS cells, it produced ≈ 30% smaller syntaxin-myc cells, indicating that syntaxin-myc cells may concentrate their fluorescence on smaller areas. This may lead to an overestimation of the BoNT/C1 induced increase in brightness. Therefore the mean intensities were related to the average size of the cells. Values are given as means ± S.E.M. (n = 5). t-test on syntaxin-myc/syntaxin-myc + BoNT/C1, p=0.034 (*p<0.05); t-test on syx-ΔS-myc/syx-ΔS-myc + BoNT/C1, p=0.998 (ns, not significant p>0.05).