Tered or damaged neurotoxins. In the specificity studies, differentiated SiMa cells were treated with recombinant LHN/A,Sensitive Cell-Based Potency Assay for BoNT/AFigure 2. SiMa cells were selected from forty-two cell lines screened for BoNT/A complex uptake. A. Example of cell line screening. Differentiated cells were treated with 1 nM BoNT/A for 6 h followed by 16 h incubation to allow for the cleavage of SNAP25. Western blots were performed with an antibody to SNAP25 and the percent SNAP25 cleavage was calculated. Sensitive cell lines Neuro-2a, N18, and LA1-55n produced ,20 cleavage while SH-SY5Y produced only 7 cleavage. Same cell lines were treated with 0.25, 0.5, and 1 nM BoNT/A. Western blots were performed with anti-buy PD1-PDL1 inhibitor 1 SNAP25197 polyclonal antibody confirming that SH-SY5Y cells were less sensitive. Cleavage of 11967625 SNAP25 could be detected with 0.25 nM BoNT/A. B. Undifferentiated Neuro-2a and SiMa cells were treated with 0.1 and 0.3 nM BoNT/A complex for 16 h. Western blots were performed with antibody S9684 (Sigma) that recognizes intact and cleaved SNAP25. Under these conditions, SiMa cells produced cleaved SNAP25197 at both concentrations while no cleavage was detected in undifferentiated Neuro-2a cells. doi:10.1371/journal.pone.0049516.glacking the binding domain but containing the Light Chain and Translocation domains, and a recombinant iBoNT/A containing an inactivating mutation in the LC [49] (Figure 4B). SNAP25197 was only detected at the higher doses of LHN/A tested, suggesting a non-specific internalization of LHN/A (signals at 100 nM LHN/ A were 3PO similar to BoNT/A at 0.31 pM) and there was no SNAP25197 detected after iBoNT/A treatments. LHN/A uptake was at least 60,000 fold lower than 150 kDa BoNT/A (EC50 = 1.6 pM). To determine the effects of higher concentrations of LHN/A in the SiMa CBA, differentiated SiMa cells were treated with BoNT/A complex (at pM concentrations) or LHN/A with a highest dose of 50 mM. The data in figure 4C confirms specificity of the CBPA to fully active toxin and defines the effects of LHN/A in the assay at concentrations ,106 higher than those of active BoNT/A. The EC50 for the LHN/A molecule was 2.1 mM versus 0.85 pM for the fully active BoNT/A. Moreover, the assay can measure the potency of pure neurotoxin (150 kDa) as well as BoNT/A complex. These results demonstrate that the CBPA mirrors BoNT/A mechanism of action in vivo: binding, internalization-translocation, and catalytic activity [14].Optimization of the CBPA for BoNT/AThree major experimental steps require optimization in a CBPA: cell growth and differentiation conditions, drug treatment, and read-out parameters. Factors influencing performance at each step were evaluated individually with BoNT/A uptake as the endpoint, measured as the presence of SNAP25197, and are summarized in Table 1. The final conditions chosen for the optimized assay were plating 50,000 cells/well in EMEM serumfree medium supplemented with N2 and B27 (Figure 5A) in polyD-lysine plates for 48 h (Figure 5B) followed by 0.004?5 pM BoNT/A treatment for 24 h and two-day incubation in toxin free medium to allow for SNAP25197 accumulation (Figure 5C). For the ECL-ELISA, High Bind ELISA plates were spotted with 5 mL of 2E2A6 at 20 mg/mL (Figure 5D), dried and then blocked with2 ECL (Enhanced Chemiluminescence) with 10 goat serum for 1 h followed by lysate incubation overnight at 4uC (Figure 5E). Sulfo-tag labeled detection antibody was incubated at room temperature for.Tered or damaged neurotoxins. In the specificity studies, differentiated SiMa cells were treated with recombinant LHN/A,Sensitive Cell-Based Potency Assay for BoNT/AFigure 2. SiMa cells were selected from forty-two cell lines screened for BoNT/A complex uptake. A. Example of cell line screening. Differentiated cells were treated with 1 nM BoNT/A for 6 h followed by 16 h incubation to allow for the cleavage of SNAP25. Western blots were performed with an antibody to SNAP25 and the percent SNAP25 cleavage was calculated. Sensitive cell lines Neuro-2a, N18, and LA1-55n produced ,20 cleavage while SH-SY5Y produced only 7 cleavage. Same cell lines were treated with 0.25, 0.5, and 1 nM BoNT/A. Western blots were performed with anti-SNAP25197 polyclonal antibody confirming that SH-SY5Y cells were less sensitive. Cleavage of 11967625 SNAP25 could be detected with 0.25 nM BoNT/A. B. Undifferentiated Neuro-2a and SiMa cells were treated with 0.1 and 0.3 nM BoNT/A complex for 16 h. Western blots were performed with antibody S9684 (Sigma) that recognizes intact and cleaved SNAP25. Under these conditions, SiMa cells produced cleaved SNAP25197 at both concentrations while no cleavage was detected in undifferentiated Neuro-2a cells. doi:10.1371/journal.pone.0049516.glacking the binding domain but containing the Light Chain and Translocation domains, and a recombinant iBoNT/A containing an inactivating mutation in the LC [49] (Figure 4B). SNAP25197 was only detected at the higher doses of LHN/A tested, suggesting a non-specific internalization of LHN/A (signals at 100 nM LHN/ A were similar to BoNT/A at 0.31 pM) and there was no SNAP25197 detected after iBoNT/A treatments. LHN/A uptake was at least 60,000 fold lower than 150 kDa BoNT/A (EC50 = 1.6 pM). To determine the effects of higher concentrations of LHN/A in the SiMa CBA, differentiated SiMa cells were treated with BoNT/A complex (at pM concentrations) or LHN/A with a highest dose of 50 mM. The data in figure 4C confirms specificity of the CBPA to fully active toxin and defines the effects of LHN/A in the assay at concentrations ,106 higher than those of active BoNT/A. The EC50 for the LHN/A molecule was 2.1 mM versus 0.85 pM for the fully active BoNT/A. Moreover, the assay can measure the potency of pure neurotoxin (150 kDa) as well as BoNT/A complex. These results demonstrate that the CBPA mirrors BoNT/A mechanism of action in vivo: binding, internalization-translocation, and catalytic activity [14].Optimization of the CBPA for BoNT/AThree major experimental steps require optimization in a CBPA: cell growth and differentiation conditions, drug treatment, and read-out parameters. Factors influencing performance at each step were evaluated individually with BoNT/A uptake as the endpoint, measured as the presence of SNAP25197, and are summarized in Table 1. The final conditions chosen for the optimized assay were plating 50,000 cells/well in EMEM serumfree medium supplemented with N2 and B27 (Figure 5A) in polyD-lysine plates for 48 h (Figure 5B) followed by 0.004?5 pM BoNT/A treatment for 24 h and two-day incubation in toxin free medium to allow for SNAP25197 accumulation (Figure 5C). For the ECL-ELISA, High Bind ELISA plates were spotted with 5 mL of 2E2A6 at 20 mg/mL (Figure 5D), dried and then blocked with2 ECL (Enhanced Chemiluminescence) with 10 goat serum for 1 h followed by lysate incubation overnight at 4uC (Figure 5E). Sulfo-tag labeled detection antibody was incubated at room temperature for.
