title: Tristetraprolin regulates TNF TNF-alpha mRNA stability via a proteasome dependent mechanism involving the combined action of the ERK and p38 pathways.
abstract: Tumor necrosis factor-alpha (TNF-alpha) is a central mediator of inflammation. TNF-alpha expression is regulated by transcriptional and post-transcriptional mechanisms, including mRNA stability and translation. Post-transcriptional control operates through cis-elements in the 3' Untranslated-Region of the TNF-alpha mRNA to which trans-acting proteins bind. One of the best characterized trans-acting proteins is Tristetraprolin (TTP), which regulates TNF-alpha message stability. However, the precise mechanisms controlling TNF-alpha message stability are unclear, with data supporting a role for the proteasome, the exosome, and the RNA processing-body (P-body), as well as the involvement of the microRNAs. We examined the effect of proteasome inhibition on endogenous TNF-alpha mRNA stability, TNF-alpha 3'UTR reporter expression and TTP function in the RAW264.7 cells. These data establish that proteasome inhibition stabilized endogenous TNF-alpha mRNA, increased TTP protein levels but inhibited TTP mediated TNF-alpha mRNA decay. Importantly, proteasome inhibition stabilized the TNF-alpha message to the same degree as LPS stimulation. To further characterize the control of TTP function, we examined the combinatorial effect of p38, ERK and JNK activation on TNF-alpha post-transcriptional expression and TTP function. These data establish that TTP mediated TNF-alpha mRNA decay is inhibited by the combined activation of ERK and p38 and not by p38 activation alone. The combined activation of ERK/p38 was sufficient to stabilize endogenous TNF-alpha mRNA to the same degree as LPS stimulation. Together these data indicate that the proteasome is a critical control point for TTP mediated TNF-alpha mRNA decay and activation of both ERK and p38 is required to inhibit TTP function and stabilize TNF-alpha mRNA.
authors.affiliation: Department of Medicine, Dartmouth Medical School, 1 Medical Center Dr., Lebanon, NH 03756, USA.
authors.forename: Kristen M
authors.initials: KM
authors.lastname: Deleault
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Skinner
authors.forename: Seth A
authors.initials: SA
authors.lastname: Brooks
mesh_terms: D020413:3' Untranslated Regions; D000818:Animals; D002460:Cell Line; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D007976:Leupeptins / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects; D051379:Mice; D008954:Models, Biological; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D061988:Proteasome Inhibitors; D014176:Protein Biosynthesis / Q000187:drug effects; D020871:RNA Stability / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D051816:Tristetraprolin / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D020413:3' Untranslated Regions; D007976:Leupeptins; D008070:Lipopolysaccharides; D061988:Proteasome Inhibitors; D012333:RNA, Messenger; D051816:Tristetraprolin; D014409:Tumor Necrosis Factor-alpha; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde