FIGURE 6.

iPLA₂β regulates Bcl-x 5′SS selection through both ceramide-dependent and -independent mechanisms. A, INS-1 cells were treated with DMSO (c) or 50 μm C₆-ceramide (Cer) for 24 h. RNA was harvested and RT-PCR performed to amplify Bcl-x splice variants. Shown is the ratio of Bcl-x(L)/Bcl-x(S) in four independent experiments. B, INS-1 cells were treated with DMSO (c), 10 μm (S)-BEL (BEL), or 1 μm thapsigargin (T) alone or pretreated with (S)-BEL prior to treatment with thapsigargin ± 50 μm C₆-ceramide (Cer) for 13 h. RNA was isolated and RT-PCR performed to amplify Bcl-x splice variants. A representative experiment is shown. C, INS-1 cells were treated with DMSO (c) or thapsigargin alone or pretreated with (S)-BEL (BEL) or 10 μm GW4869 (GW) prior to treatment with thapsigargin for 13 h, and Bcl-x RNAs were amplified. A representative experiment is shown. Each representative experiment was performed at least twice. Each quantification is presented as mean ± S.E.