GIP stimulation of survival in STS-treated INS-1 cells involves Akt.
A, INS-1 cells were treated without or with 100 nm STS and
with or without 10 nm GIP for 10 h, and onset of cell death
(defined as propidium iodide-positive (PI+) incorporation
into cell nuclei) was measured in real time every 30 min. The mean ±
S.E. of dead cells (n = 6) is shown. #, p < 0.05
versus DMSO control; $, p < 0.05 versus STS
without GIP. B, cell death (%) in INS-1 cells treated for 6 h with
STS (100 nm), with or without 10 nm GIP, and without or
with an inhibitor of Akt (500 nm Akt IV), PI3K signaling (15
μm LY294002, 5 μm Akt VIII, or 200 nm
wortmannin), Erk1/2 signaling (5 μm U0126 or 50 μm
PD985002), or PKA signaling (10 μm H89). Mean ± S.E. of
dead cells (n = 6). #, p < 0.05 (comparisons are shown).
C, shown is the cell death (%) in INS-1 cells treated for 6 h with
STS ± 10 nm IGF-I ± PI3K signaling inhibitor, 5
μm Akt VIII. Mean ± S.E. of dead cells (n = 4);
#, p < 0.05 (comparisons are shown). D, shown is the cell
death (%) in INS-1 cells transfected with enhanced green fluorescent protein
(eGFP) or HA-tagged wild-type Akt1 and treated for 6 h with STS
± GIP. Mean ± S.E. of % cell death (n = 4). #,
p < 0.05 (comparisons are shown). E, INS-1 cells were
transfected with green fluorescent protein or HA-tagged wild-type Akt and
treated for 4 h with STS ± GIP, and Western analysis was performed with
indicated antibodies. F, shown is the cell death (%) in INS-1 cells
treated for 6 h with STS (100 nm), without or with 1
μm forskolin, and without or with inhibitors of Akt signaling
(500 nm Akt IV) or PKA signaling (10 μm H89). Mean
± S.E. of dead cells (n = 6); #, p < 0.05
versus DMSO control; $, p < 0.05 versus STS
without inhibitor; %, p < 0.05 versus STS + forskolin.
G, shown is the cell death (%) in INS-1 cells treated for 6 h with
STS (100 nm) + increasing concentrations of the EPAC agonist,
8-cpt-cAMP. Mean ± S.E. of dead cells (n = 6). #, p
< 0.05 versus DMSO control; $, p < 0.05
versus STS without 8-cpt-cAMP. Anti-β-actin blots were internal
controls.