Figure 8.

Disruption of lipid raft integrity potentiates homologous desensitization of the hGLP-2R. (A) DLD-1:hGLP-2R cells were incubated with either vehicle or 4 μg/ml filipin for 30 min before and during a 20-min incubation in the absence (-) or presence of 10 nM hGLP-2 (+). This was followed by recovery in media alone for the indicated periods of time and assessment of maximal agonist-induced cAMP_i accumulation. The controls (C, white bars) represent normalized data for cells pretreated with media alone and allowed to recover for each of the times shown in the presence or absence of inhibitor. (B) To assess the effect of the inhibitors on agonist-induced cAMP production, transfected DLD-1 cells were incubated with either vehicle or the indicated inhibitor for 80 min (30 min for MβCD) before and during a 10-min incubation in the absence (basal) or presence of 100 nM hGLP-2. (C) Desensitization/recovery experiments, as described in A, were performed on DLD-1 cells 24 h after cotransfection with FLAG-hGLP-2R and either wild-type dynamin-I (Dyn wt) or the dominant-negative mutant (Dyn K44A). Data (means ± SD of triplicate values) are representative of three independent experiments and are expressed relative to their corresponding control. Statistical comparisons between recovery time and corresponding control values are indicated with asterisks (^*p < 0.05, ^**p < 0.01, ^***p < 0.001). Statistical significance between recovery time points in the presence or absence of inhibitors is represented by ^#p < 0.05, ^##p < 0.01.