FIGURE 4.
BTT-3033 and BTT-3034 recognize different α2β1 integrin conformations. A, integrin α2 expression levels on the CHO cell surface were determined by flow cytometry using anti-human CD49b and FITC-labeled secondary antibodies. B, the inhibitors (at EC50 concentrations) were tested by assaying CHO-α2E336A and CHO-α2E318W cell adhesion to collagen I in the presence of 100 nm TPA under static conditions. Adherent cells were detected using the WST-1 reagent. The data expressed are the mean ± S.E. of three to four independent experiments. BTT-3034 was a potent inhibitor of TPA-activated CHO-α2E318W cells, whereas BTT-3033 was not. Significant inhibition by BTT-3034 is indicated by an asterisk (Wilcoxon Rank-Sum test, one-tailed, *, p = 0.034; paired t test, p = 0.002).