Fig. 7. Effect of Spint1 or Hepsin depletion on GLP1R signaling-induced phospho-CREB, Mafa, and Ins1 in β cells.

a Roles of Spint1 and Hepsin in Ex4-induced CREB phosphorylation and MAFA expression in NIT-1 cells. Cells were transfected with siSpint1 and siHepsin. Control cells were transfected with scramble siRNAs. After transfection, cells were starved for 24 h and then treated with or without 25 nM Ex4 or 25 nM Exendin 9–36 (Ex9–36, a GLP1R antagonist) for 24 h. Cell lysates were then collected and subjected to western blot analysis using anti-phospho-CREB, anti-CREB, and anti-MAFA antibodies. GAPDH served as a loading control. The ratios of phospho-CREB to total CREB levels (middle panel) and MAFA protein levels (right panel), normalized to GAPDH, were statistically analyzed across four independent experiments (n = 4). b Analysis of Spint1, Hepsin, Mafa, and Ins1 expression in NIT-1 cells silenced for Spint1, Hepsin, or both, with or without Ex4 treatment. Cells were transfected with siSpint1, siHepsin, or both. Controls were transfected with scramble siRNAs. Transfectants were serum-starved for 24 h and then treated with or without 25 nM Ex4 for another 24 h. RNA was then extracted and subjected to Q-RT-PCR analysis. Results were statistically analyzed by normalizing to Gapdh relative to the control from three independent experiments (n = 3). Statistical significance was determined using a two-tailed Student’s t-test for all panels. All data were represented as mean ± SEM. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001. Below the asterisks are the precise statistical results. Source data are provided as a Source Data file.