Figure 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 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.