FIGURE 6.

Endogenous Bok is stabilized by IP₃R1. A, levels of IP₃R1 and Bok and other pertinent proteins in lysates from αT3 control and IP₃R1KO cells obtained by targeting exon 5 (lane 2) and exon 13 (lane 4). B, comparison of Bok immunoreactivity in αT3 control and IP₃R1KO cells obtained by loading different amounts of cell lysate. C, Bok mRNA levels (normalized to peptidylprolyl isomerase A) in exon 5 and exon 13 targeted αT3IP₃R1KO cells, relative to the amount present in αT3 control cells. D, αT3 IP₃R1KO cells were transfected with cDNAs encoding the IP₃R1HA constructs indicated and cell lysates were probed for Bok. The asterisk marks the same species described in Fig. 4. E, αT3 control and IP₃R1KO cells were treated as indicated with 10 μm MG132 and 20 μg/ml CHX, and 1 μg and 30 μg, respectively, of cell lysates were probed for Bok. The histogram shows combined quantitated Bok immunoreactivity normalized to levels in untreated cells from multiple independent experiments. An exon 5-targeted clone was used for the experiments shown in panels B, D, and E, and erlin2, and p97 served as loading controls.