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A new p38 MAP kinase-regulated transcriptional coactivator that stimulates p53-dependent apoptosis.

ABSTRACT: The p38 mitogen-activated protein kinase (MAPK) signaling pathway plays an important role in stress-induced cell-fate decisions by orchestrating responses that go from cell-cycle arrest to apoptosis. We have identified a new p38 MAPK-regulated protein that we named p18(Hamlet), which becomes stabilized and accumulates in response to certain genotoxic stresses such as UV or cisplatin treatment. Overexpression of p18(Hamlet) is sufficient to induce apoptosis, whereas its downregulation reduces the apoptotic response to these DNA damage-inducing agents. We show that p18(Hamlet) interacts with p53 and stimulates the transcription of several proapoptotic p53 target genes such as PUMA and NOXA. This correlates with enhanced p18(Hamlet)-induced recruitment of p53 to the promoters. In proliferating cells, low steady-state levels of p18(Hamlet) are probably maintained by a p53-dependent negative feedback loop. Therefore, p18(Hamlet) is a new cell-fate regulator that links the p38 MAPK and p53 pathways and contributes to the establishment of p53-regulated stress responses.

SUBMITTER: Cuadrado A

PROVIDER: S-EPMC1852783 | biostudies-literature | 2007 Apr

REPOSITORIES: biostudies-literature

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A new p38 MAP kinase-regulated transcriptional coactivator that stimulates p53-dependent apoptosis.

Cuadrado Ana A Lafarga Vanesa V Cheung Peter C F PC Dolado Ignacio I Llanos Susana S Cohen Philip P Nebreda Angel R AR

The EMBO journal 20070322 8

The p38 mitogen-activated protein kinase (MAPK) signaling pathway plays an important role in stress-induced cell-fate decisions by orchestrating responses that go from cell-cycle arrest to apoptosis. We have identified a new p38 MAPK-regulated protein that we named p18(Hamlet), which becomes stabilized and accumulates in response to certain genotoxic stresses such as UV or cisplatin treatment. Overexpression of p18(Hamlet) is sufficient to induce apoptosis, whereas its downregulation reduces the ...[more]

PMID: 17380123

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Project description:BackgroundConventional p38α inhibitors have limited efficacy in rheumatoid arthritis, possibly because p38 blockade suppresses the counter-regulatory mechanisms that limit inflammation. In contrast, targeting the upstream MAP kinase kinases, MKK3 and MKK6, partially maintains p38-mediated anti-inflammatory responses in bone marrow-derived macrophages (BMDM). In this study, we explored the mechanisms that preserve anti-inflammatory gene expression by evaluating differential regulation of IL-10 and p38-dependent anti-inflammatory genes in MKK3-/-, MKK6-/-, and p38 inhibitor-treated wildtype cells.MethodsBMDM from wild type (WT), MKK3-/-, and MKK6-/- mice were pre-treated with p38 inhibitor SB203580 (SB), JNK inhibitor SP600125 (SP), and/or ERK inhibitor PD98059 (PD) and stimulated with LPS. Supernatant protein levels were measured by multiplex bead immunoassay. mRNA expression was determined by qPCR and protein expression by Western blot analysis. De novo IL-10 mRNA synthesis was quantified in cells treated with ethynyl-uridine and LPS followed by reverse transcription and qPCR. mRNA half-life was measured in LPS-treated cells that were then incubated with actinomycin D ± SB203580.ResultsPre-treatment of WT BMDM with p38 inhibitor significantly reduced IL-10 production in the three groups, while ERK and JNK inhibitors had minimal effects. IL-10 production was significantly decreased in MKK3-/- BMDM compared with either WT or MKK6-/- cells. IL-10 mRNA expression was modestly reduced in MKK3-/- BMDM but was preserved in MKK6-/- cells compared with WT. De novo IL-10 mRNA synthesis was inhibited in MKK3-/- and p38 inhibitor pre-treated cells, but not MKK6-/- cells compared with WT. IL-10 mRNA half-life was markedly reduced in p38 inhibitor-treated WT cells while MKK-deficiency had minimal effect. DUSP1 mRNA levels were preserved in MKK-deficient cells but not in p38 inhibitor-treated WT cells. Tristetraprolin mRNA and protein levels were reduced in p38 inhibitor-treated WT cells compared with MKK6-/- cells.ConclusionUnlike p38-inhibition, the absence of MKK6 mostly preserves IL-10 and TTP protein expression in BMDM. MKK6-deficiency also spares DUSP1 and IL-1RA, which are key negative regulators of the inflammatory response. Together, these data suggest that MKK6 is a potential therapeutic target in RA.

Project description:TFEB (transcription factor EB) and TFE3 (transcription factor E3) are "master regulators" of autophagy and lysosomal biogenesis. The stress response p38 mitogen-activated protein (MAP) kinases affect multiple intracellular responses including inflammation, cell growth, differentiation, cell death, senescence, tumorigenesis, and autophagy. Small molecule p38 MAP kinase inhibitors such as SB202190 are widely used in dissection of related signal transduction mechanisms including redox biology and autophagy. Here, we initially aimed to investigate the links between p38 MAP kinase and TFEB/TFE3-mediated autophagy and lysosomal biogenesis. Unexpectedly, we found that only SB202190, rather than several other p38 inhibitors, promotes TFEB and TFE3 to translocate from the cytosol into the nucleus and subsequently enhances autophagy and lysosomal biogenesis. In addition, siRNA-mediated Tfeb and Tfe3 knockdown effectively attenuated SB202190-induced gene expression and lysosomal biogenesis. Mechanistical studies showed that TFEB and TFE3 activation in response to SB202190 is dependent on PPP3/calcineurin rather than on the inhibition of p38 or MTOR signaling, the main pathway for regulating TFEB and TFE3 activation. Importantly, SB202190 increased intracellular calcium levels, and calcium chelator BAPTAP-AM blocked SB202190-induced TFEB and TFE3 activation as well as autophagy and lysosomal biogenesis. Moreover, endoplasmic reticulum (ER) calcium is required for TFEB and TFE3 activation in response to SB202190. In summary, we identified a previously uncharacterized role of SB202190 in activating TFEB- and TFE3-dependent autophagy and lysosomal biogenesis via ER calcium release and subsequent calcium-dependent PPP3/calcineurin activation, leading to dephosphorylation of TFEB and TFE3. Given the importance of p38 MAP kinase invarious conditions including oxidative stress, the findings collectively indicate that SB202190 should not be used as a specific inhibitor for elucidating the p38 MAP kinase biological functions due to its potential effect on activating autophagy-lysosomal axis.

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A new p38 MAP kinase-regulated transcriptional coactivator that stimulates p53-dependent apoptosis.

Publications

A new p38 MAP kinase-regulated transcriptional coactivator that stimulates p53-dependent apoptosis.

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