Changes in AKT phosphorylation are independent to PI3K activation.
(A) HEK-293 cells expressing SSTR4 and /or δOR were treated as indicated for 15 min at 37°C and cell lysate prepared post treatment was subjected to western blot analysis to detect phospho and total-PI3K and AKT expression. The status of phospho-PI3K remained comparable to basal upon treatment with SST or SSTR specific agonist in cells expressing SSTR4. In contrast, δOR monotransfectant were devoid of phospho-PI3K expression with or without receptor specific treatment. (B) Significant activation of phospho-PI3K was observed in cotransfected cells at the basal level which remained comparable upon agonist treatments as indicated. (C) δOR monotransfected cells displayed significant increase in phospho-AKT expression upon treatment with receptor specific agonist in comparison to control, whereas, no discernible changes in phospho-AKT were observed in SSTR4 monotransfected cells. (D) In cotransfected cells, SSTR4 activation with SST or L-803087 alone or in combination with SB-205607 significantly enhanced AKT phosphorylation, with pronounced effect upon combined agonist treatment. Histograms illustrate densitometry for the blots for respective panels using β-actin or total as loading control. Data analysis was done by using ANOVA and post hoc Dunnett’s to compare against basal level (*, p<0.05).