ACTIVATION OF C-JUN N-TERMINAL KINASE STRESS-ACTIVATED PROTEIN-KINASEIN PRIMARY GLIAL CULTURES

Glial cells in the mammalian CNS are subject to environmental stress r esulting from a variety of neuropathological conditions, In this study , we have examined the activation of a stress signal responsive kinase , i.e., stress-activated protein kinase (SAPK) or c-Jun N-terminal kin ase (JNK), in primary cultures of rat brain glial cells (i.e., astrocy tes and oligodendrocytes) and an oligodendrocyte progenitor cell line, CG4, in response to cytokines and other stress inducers, JNK/SAPK act ivity was measured by an immune complex kinase assay using polyclonal anti-JNK antibodies along with GST c-Jun (1-79) as the substrate, Amon g the cytokines tested, TNF-alpha had the strongest effect on JNK acti vation followed by TNF-beta in both the glial cell types while a subst antial level of kinase activation was observed in response to IL-1 in astrocytes, JNK activation by TNF-alpha in astrocytes, but not in olig odendrocytes, showed a biphasic response, An in-gel kinase assay of ce ll extracts and immunoprecipitated JNK confirmed the activation of JNK 1 in cells treated with TNF-alpha. JNK was also activated by several o ther stress-inducing factors including UV light, heat shock, inhibitor s of protein synthesis, and mechanical injury, Incubation of cells wit h bacterial sphingomyelinase and a cell-permeable ceramide stimulated JNK activity, suggesting that the ceramide pathway may play a role in JNK activation, although the time course of activation did not corresp ond to that of TNF-alpha. The results are discussed in terms of possib le roles of JNK activation in signaling for gliosis in astrocytes and as a protective/toxic response in oligodendrocytes. (C) 1996 Wiley-Lis s, Inc.