Figure 5.

Desensitization of the T480 receptor-stimulated GTPase activity. The T480 receptor alone or in combination with GRK2-K220R was transiently transfected into COS-1 cells. Cells were stimulated for 5 min with 1 μM PTH or not (control), PTH was washed away, and the receptor-stimulated GTPase activity was determined in membranes prepared from these cells. Experiments were performed in triplicate, and data are mean ± SE of three independent experiments where GTPase activity of the T480 receptor without prestimulation (0.39 ± 0.11 pmol Pi/min per mg of protein) was set to 100%.