Fig. 5.

Menin decreases GLP1R signaling downstream of adenylyl cyclase without affecting cAMP accumulation. A: menin does not affect cAMP levels upon GLP1R agonist stimulation. MIN6 cells overexpressing menin or vector controls were starved for 48 h followed by pretreatment with the phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (IBMX; 45 μM) for 5 min and then treated with different concentrations of exendin-4 (2 and 20 nM) for another 30 min, and cells were collected for cAMP accumulation assay. While both exendin-4 and IBMX induced cAMP accumulation as expected, menin overexpression did not differentially affect cAMP accumulation compared with vector controls, both in the presence and absence of IBMX (two experiments). B: MIN6 cells were starved in low-glucose, serum-free DMEM for 3 h, at which time, the cells were treated with either vehicle or MI-2-2 (500 nM) for a total of 48 h before treatment with varying concentrations of exendin (2 nM or 20 nM) for an additional 30 min. MI22 treatment did not affect cAMP accumulation compared with vehicle (DMSO) controls (representative plot of two similar experiments).