Microtubule Integrity Regulates Src-like and Extracellular Signal-regulated Kinase Activities in Human Pro-monocytic Cells. IMPORTANCE FOR INTERLEUKIN-1 PRODUCTION (original) (raw)
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Microtubule acetylation amplifies p38 kinase signalling and anti-inflammatory IL-10 production
Nature Communications, 2014
Reversible acetylation of α-tubulin is an evolutionarily conserved modification in microtubule networks. Despite its prevalence, the physiological function and regulation of microtubule acetylation remains poorly understood. Here we report that macrophages challenged by bacterial lipopolysaccharides (LPS) undergo extensive microtubule acetylation. Suppression of LPSinduced microtubule acetylation by inactivating the tubulin acetyltransferase, MEC17, profoundly inhibits the induction of anti-inflammatory interlukin-10 (IL-10), a phenotype effectively reversed by an acetylation-mimicking α-tubulin mutant. Conversely, elevating microtubule acetylation by inhibiting the tubulin deacetylase, HDAC6, or stabilizing microtubules via Taxol, stimulates IL-10 hyper-induction. Supporting the anti-inflammatory function of microtubule acetylation, HDAC6 inhibition significantly protects mice from LPS toxicity. In HDAC6-deficient macrophages challenged by LPS, p38 kinase signaling becomes selectively amplified, leading to SP1-dependent IL-10 transcription. Remarkably, the augmented p38 signaling is suppressed by MEC17 inactivation. Our findings identify reversible microtubule acetylation as a kinase signaling modulator and a key component in the inflammatory response. Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:
Association of Mitogen-activated Protein Kinases with Microtubules in Mouse Macrophages
1996
Taxol, a microtubule-binding diterpene, mimics many effects of lipopolysaccharide (LPS) on mouse macrophages. The LPS-mimetic effects of taxol appear to be under the same genetic control as responses to LPS itself. Thus we have postulated a role for microtubule-associated proteins (MAP) in the response of macrophages to LPS. Stimulation of macrophages by LPS quickly induces the activation of mitogen-activated protein kinases (MAPK). MAPK are generally considered cytosolic enzymes. Herein we report that much of the LPS-activatable pool of MAPK in primary mouse peritoneal macrophages is microtubule associated. By immunofluorescence, MAPK were localized to colchicine-and nocodazole-disruptible filaments. From both mouse brain and RAW 264.7 macrophages, MAPK could be coisolated with polymerized tubulin. Fractionation of primary macrophages into cytosol-, microfilament-, microtubule-, and intermediate filament-rich extracts revealed that "~10% of MAPK but none ofMAPK kinase (MEK1 and MEK2) was microtubule bound. Exposure of macrophages to LPS did not change the proportion of MAPK bound to microtubules, but preferentially activated the microtubule-associated pool. These findings confirm the prediction that LPS activates a kinase bound to microtubules. Together with LPS-mimetic actions of taxol and the shared genetic control of responses to LPS and taxol, these results support the hypothesis that a major LPS-signaling pathway in mouse macrophages may involve activation of one or more microtubuleassociated kinases.
Microtubule-mediated NF-κB activation in the TNF-α signaling pathway
Experimental Cell Research, 2009
The microtubule cytoskeleton is known to play a role in cell structure and serve as a scaffold for a variety of active molecules in processes as diverse as motility and cell division. The literature on the role of microtubules in signal transduction, however, is marked by inconsistencies. We have investigated a well-studied signaling pathway, TNF-α-induced NF-κB activation, and found a connection between the stability of microtubules and the regulation of NF-κB signaling in C2C12 myotubes. When microtubules are stabilized by paclitaxel (taxol), there is a strong induction of NF-κB even in the absence of TNF-α. Although there was no additive effect of taxol and TNF-α on NF-κB activity suggesting a shared mechanism of activation, taxol strongly induced the NF-κB reporter in the presence of a TNF receptor (TNFR) blocking antibody while TNF-α did not. Both TNF-α and taxol induce the degradation of endogenous IκBα and either taxol or TNF-α induction of NF-κB activity was blocked by inhibitors of NF-κB acting at different sites in the signaling pathway. Both TNF-α and taxol strongly induce known NF-κB chemokine target genes. On the other hand, if microtubules are destabilized by colchicine, then the induction of NF-κB by TNF-α or taxol is greatly reduced. Taken together, we surmise that the activity of microtubules is at the level of the TNFR intracellular domain. This phenomenon may indicate a new level of signaling organization in cell biology, actively created by the state of the cytoskeleton, and has ramifications for therapies where microtubule regulating drugs are used.
IL-1R–Associated Kinase-1 Mediates Protein Kinase Cδ-Induced IL-1β Production in Monocytes
2011
The role of IL-1R-associated kinase (IRAK)1 and its interaction with protein kinase C (PKC)d in monocytes to regulate IL-1b production has not been reported so far. The present study thus investigates such mechanisms in the THP1 cell line and human monocytes. PMA treatment to THP1 cells induced CD11b, TLR2, TLR4, CD36, IRAK1, IRAK3, and IRAK4 expression, IRAK1 kinase activity, PKCd and JNK phosphorylation, AP-1 and NF-kB activation, and secretory IL-1b production. Moreover, PMAinduced IL-1b production was significantly reduced in the presence of TLR2, TLR4, and CD11b Abs. Rottlerin, a PKCd-specific inhibitor, significantly reduced PMA-induced IL-1b production as well as CD11b, TLR2 expression, and IRAK1-JNK activation. In PKCd wild-type overexpressing THP1 cells, IRAK1 kinase activity and IL-1b production were significantly augmented, whereas recombinant inactive PKCd and PKCd small interfering RNA significantly inhibited basal and PMA-induced IRAK1 activation and IL-1b production. Endogenous PKCd-IRAK1 interaction was observed in quiescent cells, and this interaction was regulated by PMA. IRAK1/4 inhibitors, their small interfering RNAs, and JNK inhibitor also attenuated PMA-induced IL-1b production. NF-kB activation inhibitor and SN50 peptide inhibitor, however, failed to affect PMA-induced IL-1b production. A similar role of IRAK1 in IL-1b production and its regulation by PKCd was evident in the primary human monocytes, thus signifying the importance of our finding. To our knowledge, the results obtained demonstrate for the first time that IRAK1 and PKCd functionally interact to regulate IL-1b production in monocytic cells. A novel mechanism of IL-1b production that involves TLR2, CD11b, and the PKCd/IRAK1/JNK/AP-1 axis is thus being proposed.
Cellular Immunology, 1990
The production of interleukin 1 (ILl), a pleiotropic monocyte-derived interleukin, can be induced in vitro by various stimuli. The present study shows that cytochalasins which inhibit actin filament polymerization in various cell types have no significant effect on IL1 production from human monocytic cells. On the contrary, microtubule disrupters such as colchicine, vinbiastine, and vincristine dramatically potentiate (15 to 35-fold), in a dose-dependent fashion, cell-associated IL1 and to a lesser extent (2.5 to 'I-fold) released IL1 in the myelomonocytic THPl cell line and in adherent peripheral blood mononuclear cells. The enhancing effect of the drugs was blocked by actinomycin D and by cycloheximide and was accompanied by an increase of specific IL1 fi mRNA expression as measured by Northern blot analysis, thus indicating that these drugs act at a transcriptional or post-transcriptional IL1 gene expression level. o 1990 Academic Press, Inc.