Figure 7

LPI releases prebound Stx; the inhibitory effect of LPI on Stx binding is reversed by mβCD; LPI has almost no inhibitory effect on binding of ricin.

(a) HEp-2 cells were incubated with ¹²⁵I-Stx1m on ice for 30 min, washed and treated with 10 μM LPI for 20 min at 37 °C. Cell medium was collected, cells were lysed and the radioactivity signal was counted. The quantification of ¹²⁵I-Stx1m counts is expressed as % of total counts (mean ± SEM; n = 3). (b) Cells were pretreated with 10 μM LPI for 30 min and then increasing concentrations of mβCD were added and treatment continued for 15 min. Cells were then incubated with ¹²⁵I-Stx1m for 20 min at 37 °C and cell-associated ¹²⁵I-Stx1m was counted, quantification results presented as % of control (mean ± SEM; n = 3). (c) Cells were pretreated with 10 μM LPI for 30 min and then 10 mM mβCD was added and treatment continued for 15 min. Cells were then incubated with ¹²⁵I-Stx1m for 20 min on ice and cell bound ¹²⁵I-Stx1m was counted, quantification results presented as % of control (mean ± SEM; n = 3). (d) Cells were pretreated with 10 μM LPI for 30 min at 37 °C, prior to incubation with ¹²⁵I-ricin (20 min 37 °C). After the treatment, cells were washed, lysed and the radioactive signal was measured. Quantification data are presented as % of control (mean ± SEM; n = 6).