insulinoma cell
lines βTC6 (ATCC) and MIN6 were maintained in Dulbecco’s
modified Eagle’s medium (DMEM) supplemented with 15% fetal
bovine serum (FBS), 1× GlutaMAX, 1× nonessential amino acids,
and 1 mM sodium pyruvate. INS-1 rat insulinoma cells were maintained
in RPMI medium supplemented with 10% FBS, 1× GlutaMAX, 1×
nonessential amino acids, and 1 mM sodium pyruvate. Human islets were
obtained from the Integrated Islet Distribution Program (Duarte, CA)
in accordance with Oklahoma Medical Research Foundation internal review
board (IRB) and ethical guidelines for the use of human tissue. Standard
viability was 80–90% and purity was >80%. Islets were maintained
in CMRL medium supplemented with 10% FBS. All cells were grown at
37 °C in a humidified 5% CO2 atmosphere. Tunicamycin
(Tm), brefeldin A (BFA), and thapsigargin (Tg) were from Sigma. CellTiter-Glo
and Caspase-Glo 3/7 reagents were from Promega. Salubrinal, guanabenz
acetate, STF083013, and kaempferol were from Tocris, quercetin and
apigenin were from Cayman, and PP1 Analog II was from Calbiochem.