FIGURE 2.

CCK binding and signaling responses at wild type and mutant CCK receptors in the absence or presence of elevated membrane cholesterol. Shown are CCK competition-binding (top panels, A and B) and dose-dependent calcium-response curves (bottom panels, C and D) for receptor-bearing CHO cell lines for CCK1R WT and CCK1R Y140A in the presence of excess membrane cholesterol (A and C), as well as for the corresponding mutant CCK2R Y153A (B and D). Inset shows representative images of filipin staining of cholesterol in control and cholesterol-modulated CHO-CCK1R cells, where an increase in staining is observed on cells with augmented membrane cholesterol. Radioligand binding values reflect percentages of maximum saturable CCK radioligand binding in the absence of competing CCK. Intracellular calcium responses are expressed as percentages of the maximal responses measured for each condition. The curves represent mean ± S.E. from four to nine independent experiments performed in duplicate.