Strong c-Jun/AP-1 immunoreactivity is restricted to apoptotic cells following intracerebral ibotenic acid injection in developing rats

Strong c-Jun immunoreactivity, as revealed with the antibody c-Jun/activator protein 1 (AP-1) which is raised against the amino acids 91-105 mapping with the amino terminal domain of mouse c-Jun p39, is observed in apoptotic cells, but not in necrotic cells, following intracerebral injection of ibotenic acid in the developing rat brain processed for immune histochemistry. Immunostaining occurs in the cytoplasm and dendrites, thus suggesting impaired nuclear translocation of c-Jun in apoptotic cells. Western blotting of total brain homogenates, using the same antibody, shows a band at p39 which is more marked in treated animals than in age-matched controls. In addition, increased c-Jun N-terminal kinase 1 (JNK-1) expression, as revealed on Western blots, is found in rats treated with ibotenic acid when compared with controls. In contrast, apoptotic cells are not stained with antibodies to Jun B and Jun D. These results give further support to previous studies showing strong c-Jun expression in apoptotic cells at determinate stages of development, and emphasize that intracellular distribution of c-Jun, possible post-translational modifications of c-Jun due to phosphorylation at specific transactivation sites, and lack of associated Jun B and Jun D expression may differentiate the Jun response in apoptotic cells from other forms of cellular response involving c-Jun which are not associated with cell death. (C) 1997 Elsevier Science Ireland Ltd.