FIGURE 10.

rBASIC activity is dependent on the cholesterol content of the plasma membrane. A, representative current traces showing the activation of WT rBASIC (upper panel, blue traces) and rBASIC ΔN30 (lower panel, red traces) expressed in HEK293 cells by the removal of extracellular divalent cations (−Ca²⁺) and the application of increasing concentrations UDCA. Before current recordings, HEK293 cells were either incubated for 1 h in 10 mm MβCD to remove cholesterol from the plasma membrane (−Chol.) or incubated for 1 h in 10 mm water-soluble cholesterol to increase the cholesterol content of the plasma membrane (+Chol.). Untreated HEK293 cells served as control (norm.). B, concentration-response curves for UDCA for WT rBASIC and rBASIC ΔN30 recorded from cells treated with 10 mm MβCD or 10 mm water-soluble cholesterol or untreated as shown in A. Color coding matches traces shown in A. Error bars, S.E., curves were fitted to the Hill equation (n = 8).