FIG 8.

Impaired recovery of E354Q GIPR after desensitization affects receptor function. (A) Dose-response of WT and E354Q BTX-GIPR stably expressed in adipocytes. The data are averages of data from 3 experiments ± standard errors of the means. (B) Elevated cAMP levels in adipocytes stably expressing WT or E354Q BTX-GIPR as a function of time of GIP stimulation. Data are averages of data from 2 experiments ± SD. (C) The amount of HA-GLUT4-GFP in the plasma membrane of adipocytes stably expressing WT BTX-GIPR or E354Q BTX-GIPR after a 30-min stimulation with 0.2 nM insulin or 0.2 nM insulin and 100 nM GIP or with no stimulation (basal) was determined. (D) In parallel, the amount of HA-GLUT4-GFP in the plasma membrane of adipocytes preincubated with 100 nM GIP for 60 min, washed free of GIP, and allowed to recover for either 60 min or 240 min before stimulation with 0.2 nM insulin or 0.2 nM insulin and 100 nM GIP was determined. Each bar represents the average ± standard error of the mean from 3 independent experiments (*, P < 0.02; ns, not significant).