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

Abstract

By performing in vitro kinase assays we found in papilloma producing 308 mouse keratinocytes that okadaic acid elevated activities of extracellular signalregulated kinase (ERK) 1/2, c-Jun N-terminal kinases (JNKs) and p38 mitogen-activated protein kinases (MAPKs). This okadaic acid mediated activation of MAP kinases correlated with increased AP-1 binding to a consensus TPA responsive element (TRE) and elevated TRE dependent transcription. To determine the role of p38 MAP kinases in these processes we employed the speci®c p38 MAP kinase inhibitor SB 203580. Using orthophosphate labeling we showed a decrease in phosphorylation of MAPK activated protein kinase-2 (MAPKAP-K2) indicating reduced activity of p38 MAPKs utilizing this kinase as substrate. In contrast, we found that SB 203580 raised activities of ERK-1/2 and JNKs. Electrophoretic mobility shift assays revealed an increase in TRE binding activity in response to SB 203580 most likely resulting from increased expression of the major TRE binding components JunD and FosB as indicated by Western blot analyses. Increased TRE DNA binding failed to lead to increased transactivation correlating with the inability of SB 203580 to increase phosphorylation of these AP-1 proteins. These data indicate that SB 203580 sensitive p38 MAP kinases are not involved in okadaic acid mediated increases in TRE DNA binding and transactivation.

Proasthmatic effects and mechanisms of action of the dust mite allergen, Der p 1, in airway smooth muscle

“…The latter finding concurs with earlier observations made in other cell systems wherein inhibition of p38 MAPK was also found to enhance ERK1/2 phosphorylation and thereby augment ERK1/2-mediated cellular responses. [23][24][25][26] These previous findings, together with our current observations, are consistent with the concept that p38 MAPK negatively regulates the ERK1/2 signaling pathway. Supporting this concept, a direct 1-way cross-talk between p38 MAPK and ERK1/2 was recently demonstrated, wherein phosphorylated p38a was found to couple with ERK1/2 and thereby sterically block ERK1/2 phosphorylation by MEK1/2, 22 and possibly also act via a protein kinase that lies upstream of MEK1/2.…”

“…This consideration appeared consistent with the findings in recent reports that demonstrated a negative regulatory interaction between the ERK1/2 and p38 MAPK signaling pathways, wherein p38 MAPK activation was found to inhibit ERK1/2 signaling 22 and, conversely, inhibition of p38 MAPK was shown to activate ERK1/2. [23][24][25][26] To address the latter mechanism herein, we examined the separate effects of inhibition and stimulation of p38 MAPK on Der p 1-induced activation of ERK1/2. As exemplified by the Western blots depicted in Fig 6 (top panel), relative to tissues that were not pretreated with the p38 MAPK inhibitor, Der p 1-exposed ASM tissues pretreated with SB202190 displayed distinctly enhanced time-related expression of phosphorylated ERK1/2.…”

Bile Acid-induced Activation of Activator Protein-1 Requires Both Extracellular Signal-regulated Kinase and Protein Kinase C Signaling

“…6B). As reported by previous studies (27), blocking of p38 activity by the p38 inhibitor SB 202190 stimulated DCA-induced ERK activation and p38 phosphorylation (Fig. 6, A and B).…”

CD28 Signaling Augments Elk-1-Dependent Transcription at the c-fosGene During Antigen Stimulation

“…We have found that this GST-Elk-1 fusion protein binds only activated (dual phosphorylated) ERK, and does not bind either resting or activated JNK (data not shown). Incorporation of 32 P into all substrates was found to be linear with time over the course of the in vitro kinase reactions and sensitive to differences in enzyme activity, as established by SDS-PAGE and autoradiography. Dualspecific phosphorylation of p38 indicative of its activation was detected using phospho-p38 MAPK (Thr 180 /Tyr 182 ) Ab obtained from New England Biolabs (Beverly, MA) to probe a Western blot.…”