Effects of the inhibition of p38/RK MAP kinase on induction of five fos and jun genes by diverse stimuli

Abstract

The ERK, JNK/SAPK and p38/RK MAP kinase subtypes are di erentially activated by physiological, pharmacological and stress stimuli; all three subtypes are implicated in immediate-early (IE) gene induction by these agents. Here, we have asked whether inhibition of a single MAP kinase subtype under these conditions would generally alter induction of several IE genes in a similar way or whether this would di erentially up-and down-regulate particular IE genes, an issue which bears on the question of whether individual MAP kinases are strictly targeted to speci®c IE genes, or whether they might catalyse phosphorylation events that a ect several IE genes in the same way. SB 203580, an inhibitor of p38/RK, has been used to analyse the role of this kinase in the induction of ®ve IE genes (c-fos, fosB, c-jun, junB and junD) under diverse conditions of stimulation. In C3H 10T cells, p38/RK and its downstream kinase MAPKAP K-2 are activated by all stimuli used with the exception of TPA. The speci®city of SB 203580 as a p38/RK inhibitor in these cells is demonstrated; it does not a ect ERKs or JNK/SAPKs but does result in a small increase in the activity of the upstream kinase MKK6, the principal p38/RK activator in these cells. We ®nd that inhibition of p38/RK under these conditions produces general e ects on all ®ve IE genes as a group in three ways. First, induction of all ®ve genes in response to okadaic acid or tumour necrosis factor-a (TNF-a) is not signi®cantly altered by SB 203580. Second, in cells stimulated with anisomycin or U.V. radiation, SB 203580 potently inhibits all of the induced IE genes. Finally, SB 203580 enhances induction of all ®ve IE genes in EGF-treated cells; these enhanced mRNA levels are not due to stabilisation of labile mRNA transcripts. The signi®cance of these results to current thinking on the relationship between distinct MAP kinase subtypes and speci®c IE genes is discussed.

Inhibition of p38 MAP kinase increases okadaic acid mediated AP-1 expression and DNA binding but has no effect on TRE dependent transcription

“…This increased AP-1 activity correlated with activation of the MAP kinases ERK-1/ 2, JNK and p38 MAPK, and ERK-1/2 activation appeared to play a critical role in okadaic acid mediated e ects on this transcription factor complex (Rosenberger et al, 1999). Various other studies implying p38 MAP kinase in AP-1 regulation (Hazzalin et al, 1996(Hazzalin et al, , 1997 suggest that p38 MAP kinase may also be involved in okadaic acid induced AP-1 activation. To test this hypothesis we used SB 203580, a pyridinyl-imidazole compound described as speci®c inhibitor of this enzyme (Lee et al, 1994;Cuenda et al, 1995), in an attempt to block p38 MAP kinase activation.…”

“…This hypothesis is consistent with our preliminary ®nding that while SB 203580 decreases MAPKAP kinase-2 phosphorylation it increases p38 MAP kinase mediated phosphorylation of Elk-1 (data not shown). Further evidence comes from a report by Hazzalin et al (1997) who documented elevated activity of the p38 MAP kinase activator MKK6 without an increase in MAKAP kinase-2 phosphorylation.…”

The neuroprotective agents chlomethiazole and SB203580 inhibit IL‐1β signalling but not its biosynthesis in rat cortical glial cells

“…Thus, an explanation for this effect of SB203580 might be provided by a potential feedback between kinase pathways, so that inhibition of p38 MAP kinase activity by SB203580 might result in the up-regulation of another kinase activity which would positively regulate IL-1b release. Such feedback is already demonstrated for MKK6, an upstream activator of p38 MAP kinase, whose activity is potentiated by SB-like compounds (Hazzalin et al 1997). Recently, p38 MAP kinase was found to down-regulate ERK activity by direct protein-protein interaction (Hong Zhang et al 2001), and additionally, monocytes treated with the MEK inhibitor U0126 failed to release IL-1b, TNF-a, IL-8 and prostaglandin E 2 (PGE 2 ), indicating the involvement of the ERK pathway in cytokine and PG synthesis and/or release (Scherle et al 1998).…”

Effect of SB 203580 on the activity of c-Raf in vitro and in vivo

“…The ®nding that c-Raf is inhibited by SB 203580 at micromolar concentrations was surprising because we have reported previously that the activation of MAPK1 and MAPK2 by NGF in rat PC12 cells , by EGF or IGF-1 in human KB cells Gould et al, 1995), or by EGF or phorbol esters in mouse C3H 10T1/2 cells (Hazzalin et al, 1997), is not inhibited by SB 203580. In the present study we con®rmed this result for EGFstimulated Swiss 3T3 cells ( Figure 2) and IGF-1 stimulated rat L6 myotubes (data not shown).…”

“…SB 203580 does not a ect the activation of the classical MAP kinase cascade by a variety of agonists Gould et al, 1995;Hazzalin et al, 1997). However, the protein kinase that is thought to lie at the head of this cascade, the proto-oncogene cRaf, contains threonine at the position equivalent to Thr 106 of SAPK2a/p38a.…”