Fig. 6. The IB1/JIP-1 content is crucial to mediate JNK activity and apoptosis. (A,B) Western-blot analysis and solid-phase kinase assay using glutathione-S-transferase/Jun as substrate revealed a decrease of IB1/JIP-1 expression in isolated islets associated with an increase of JNK activity (P-GST/Jun) in mice islets from heterozygous (IB1/JIP-1^+/–) compared with wild-type mice (IB1/JIP-1^+/+). The JNK content was evaluated by western blotting. Equal loading of substrate was confirmed by Coomassie-blue staining of the gel (GST-Jun). (C) Apoptosis rate in whole mouse islets from heterozygous (IB1/JIP-1^+/–) compared with wild-type mice (IB1/JIP-1^+/+). Quantitative assessment of 12 measurements showed that apoptosis levels were increased approximately fourfold over control values. Columns represent mean ± s.e.m. **P<0.01