Fig. 4.

Stable expression of β-arrestin2 (R169E) controls the exaggerated PTH activation of inositol trisphosphate (IP₃) formation in the PD-PPR cells. The PD-PPR cells stably expressing control vector, WT-β-arrestin2, or β-arrestin2 (R169E) were serum starved for 1 h and then treated with vehicle or 100 nM PTH for 40 min at 37°. The cells were then placed on ice, washed 2× with ice-cold PBS, and assayed for IP₃ as described in materials and methods. Each condition was performed in duplicate, and each experiment was repeated three times. The results are means ± SD of three experiments from two independently isolated stable cell lines, and all experiments were performed in the GFP-tagged PPR cell lines. Bars with * or ** indicate significance compared with the corresponding control (P value <0.05). For reference, corresponding Western blot for protein expression of endogenous β-arrestin (control), WT β-arrestin2, and β-arrestin2 (R169E) in the PD-PPR cells is shown on the bottom. Corresponding β-actin housekeeping protein is shown as a control. Band densities were quantified and normalized to β-actin. The number at the bottom of each blot indicates band density relative to its own β-actin band.