The p38 MAPK Regulates IL-24 Expression by Stabilization of the 3′ UTR of IL-24 mRNA

Abstract

BackgroundIL-24 (melanoma differentiation-associated gene-7 (mda-7)), a member of the IL-10 cytokine family, possesses the properties of a classical cytokine as well as tumor suppressor effects. The exact role of IL-24 in the immune system has not been defined but studies have indicated a role for IL-24 in inflammatory conditions such as psoriasis. The tumor suppressor effects of IL-24 include inhibition of angiogenesis, sensitization to chemotherapy, and p38 mitogen-activated protein kinase (MAPK)-mediated apoptosis. Current knowledge on the regulation of IL-24 expression is sparse. Previous studies have suggested that mRNA stabilization is of major importance to IL-24 expression. Yet, the mechanisms responsible for the regulation of IL-24 mRNA stability remain unidentified. As p38 MAPK is known to regulate gene expression by interfering with mRNA degradation we examined the role of p38 MAPK in the regulation of IL-24 gene expression in cultured normal human keratinocytes.Methodology/Principal FindingsIn the present study we show that anisomycin- and IL-1β- induced IL-24 expression is strongly dependent on p38 MAPK activation. Studies of IL-24 mRNA stability in anisomycin-treated keratinocytes reveal that the p38 MAPK inhibitor SB 202190 accelerates IL-24 mRNA decay suggesting p38 MAPK to regulate IL-24 expression by mRNA-stabilizing mechanisms. The insertion of the 3′ untranslated region (UTR) of IL-24 mRNA in a tet-off reporter construct induces degradation of the reporter mRNA. The observed mRNA degradation is markedly reduced when a constitutively active mutant of MAPK kinase 6 (MKK6), which selectively activates p38 MAPK, is co-expressed.Conclusions/SignificanceTaken together, we here report p38 MAPK as a regulator of IL-24 expression and determine interference with destabilization mediated by the 3′ UTR of IL-24 mRNA as mode of action. As discussed in the present work these findings have important implications for our understanding of IL-24 as a tumor suppressor protein as well as an immune modulating cytokine.

Induction of phenotype modifying cytokines by FERMT1 mutations

“…These results extend observations on stimulation of IL-20 upon hypoxia (Chen and Chang, 2009) and UVB irradiation (Hunt, et al, 2006). Both IL-20 and IL-24 expression is dependent on p38 MAPK (Otkjaer, et al 2010;Otkjaer, et al, 2007), which is increased in KS cells (own unpublished results). This cytokine has been shown to specifically inhibit the activation of NF-kappaB induced by interleukin 1 family, member 6 (Blumberg, et al, 2007), but its contribution to KS phenotypes remains to be established.…”

“…Thus far, little has been known about the functions of these cytokines in the skin. A recent study reported their induction after skin injury (Roupe, et al, 2010), and previous investigations suggested regulation of these interleukins through stress induced pathways (Chen and Chang, 2009;Hunt, et al, 2006;Otkjaer, et al, 2010;Otkjaer, et al, 2007). To corroborate this in KS, we used three different well-established methods -hypoxia, oxidative stress and UVB irradiation -to induce cell stress in normal and KS keratinocytes and showed that stress enhances expression and secretion of IL-20 and IL-24 by KS cells.…”

IL-1-induced Post-transcriptional Mechanisms Target Overlapping Translational Silencing and Destabilizing Elements in IκBζ mRNA*

“…Reverse transcription and quantitative PCR were carried out essentially as described earlier (35). TaqMan probes (Applied Biosystems, assay-IDs as follows: NFKBIA, Hs00153283_m1; NFKBID, Hs00262018_m1; IL-6, Hs00174131_m1; GAPDH, Hs99999905_m1; IL-8, Hs00174103_m1) were used with TaqMan Fast Universal PCR Master Mix (2ϫ) (Applied Biosystems).…”

Expression analysis of miRNAs in BmN cells

“…This may be because the hairpin structure of pri-miRNA and its insertion changed the secondary structure of 3′UTR of GFP gene. Some studies confirmed that 3′UTR can affect the gene expression (Mazumder et al, 2005;Otkjaer et al, 2010;Wang et al, 2006;Zearfoss et al, 2011). In mouse, miR-1 and miR-133 are clustered together on the same chromosomal loci, where they are separated by 9.3 kb, and transcribed together in a tissue-specific manner during development .…”