Regulation Of MKP-1 Research Articles

Bone Marrow Mesenchymal Stem Cells (BMSCs)-Exosome Inhibits Epithelial Ovarian Cancer (EOC) Cell Proliferative Ability Through Regulating Mitogen-Activated Protein Kinase (MKP)-1 and Mitogen-Activated Protein Kinases (MAPK)/Extracellular-Signal-Regulated Kinase (ERK) Signal Pathway

The BMSCs-exosome plays a role in regulating tumor micro-environment so as to affect tumor cell biological behaviors. However, whether it affects the biological characteristics of epithelial ovarian cancer (EOC) cells remains unclear. Our study aimed to discuss whether BMSCs-exosome affects EOC cell proliferative ability. BMSCs cells were cultivated to isolate exosome which was used to treat EOC cells at different concentrations (25, 50, and 100 μmol/L) followed by measuring cell proliferation by CCK-8, cell invasion and migration by Transwell, MKP-1and MAPK/ERK protein level by Western Blot. BMSCs-exosome showed positive expression of CD9, CD63 and CD81 and negative CD116 and CD19. It could significantly inhibit EOC cell proliferation, invasion and migration in a dose-dependent manner along with reduced expression of MAPK/ERK. In conclusion, BMSCs-exosome inhibits EOC cell biological behaviors possibly through regulation of MKP-1 and MAPK/ERK signal pathway, indicating that it might be used as a novel approach for treating EOC.

Abstract 2360: Regulation of the MAPK phosphatase MKP-1 by the E3 ligase GP78 in cancer cells

Abstract Mitogen-activated protein kinase (MAPK) phosphatase 1 (DUSP1/MKP-1) is a member of the threonine-tyrosine dual-specificity phosphatase family that is endogenous inhibitor for extracellular signal-regulated protein kinases (ERKs), p38 MAPKs, and JNKs signaling. MKP-1 plays a key role in determining the magnitude and duration of MAPK activation in response to extracellular stimuli. In human cancers, abnormal expression of DUSP1 is associated with tumor development, chemoresistance and prognosis. However, the mechanism by which MKP-1 is regulated is not fully understood. Here, we show that GP78, an E3 ligase, plays an important role in regulation of MKP-1 protein levels. Specifically, we found that MKP-1 interacts with GP78 both in vitro and in vivo. Their interaction occurs between the N-terminal, Rhodanese domain of MKP-1 and C-terminal E3 ligase domain of GP78. We also found that K230, 280, and 289 residues on MKP-1 are responsible for its ubiquitination. Importantly, this interaction causes MKP-1 ubiquitination and subsequent degradation. Furthermore, we showed by overexpression and knockdown studies that GP78 downregulates the level of MKP-1 protein in cancer cells. Therefore, we identify a novel mechanism by which GP78 controls MKP-1 protein levels and suggest that this regulatory mechanism may play an important in cancer. Citation Format: Dhonghyo Kho, Gen Sheng Wu. Regulation of the MAPK phosphatase MKP-1 by the E3 ligase GP78 in cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2360. doi:10.1158/1538-7445.AM2017-2360

Abstract 203: Redox Regulation of MKP-1 and the Functional Reprogramming of Monocyte-Derived Macrophages by Metabolic Stress

Objective: To determine the mechanisms through which MKP-1 deficiency in monocytes and macrophages promotes atherogenesis. Methods and Results: Transplantation of MKP-1-deficient (MKP KO ) bone marrow into LDL-R -/- (MKP-1 LeuKO ) mice accelerated high fat diet (HFD)-induced atherosclerotic lesion formation. After 12 weeks of HFD feeding, MKP-1 LeuKO mice showed increases in lesion size in both the aortic root and the aorta, despite reduced plasma cholesterol levels. Macrophage content was increased in lesions of MKP-1 LeuKO mice compared to mice that received wt bone marrow. After only 6 weeks on a HFD, the in vivo chemotactic activity of monocytes was already significantly increased in MKP-1 LeuKO mice. Macrophages isolated from MKP KO mice showed impaired autophagy, increased sensitivity to 7-ketocholesterol-induced apoptosis, and IL-4-induced M2 polarization of these macrophages was blocked. Importantly, macrophages in atherosclerotic lesion of MKP-1 LeuKO mice showed increased macrophage apoptosis and decreased autophagy. Metabolic stress in vitro mimicked the functional phenotype of MKP-1 deficiency, and overexpression of MKP-1 protected macrophages from metabolic stress-induced dysfunction and reprogramming. Conclusions: Loss of MKP-1 activity promotes monocyte dysfucntion and the functional reprogramming of monocyte-derived macrophages. MKP-1 deficiency accelerates atherosclerotic lesion formation by hyper-sensitizing monocytes to chemokine-induced recruitment, predisposing macrophages to M1 polarization, impaired autophagy and oxysterol-induced cell death. Reduced MKP-1 levels and activity in blood monocytes may therefore be a sensitive biomarker of increased risk of atherosclerosis.

Mitogen-activated protein kinase phosphatase-1: a critical phosphatase manipulating mitogen-activated protein kinase signaling in cardiovascular disease (review).

Mitogen-activated protein kinase (MAPK) cascades are important players in the overall representation of cellular signal transduction pathways, and the deregulation of MAPKs is involved in a variety of diseases. The activation of MAPK signals occurs through phosphorylation by MAPK kinases at conserved threonine and tyrosine (Thr-Xaa-Tyr) residues. The mitogen-activated protein kinase phosphatases (MKPs) are a major part of the dual-specificity family of phosphatases and specifically inactivate MAPKs by dephosphorylating both phosphotyrosine and phosphoserine/phosphothreonine residues within the one substrate. MAPKs binding to MKPs can enhance MKP stability and activity, providing an important negative-feedback control mechanism that limits the MAPK cascades. In recent years, accumulating and compelling evidence from studies mainly employing cultured cells and mouse models has suggested that the archetypal MKP family member, MKP-1, plays a pivotal role in cardiovascular disease as a major negative modulator of MAPK signaling pathways. In the present review, we summarize the current knowledge on the pathological properties and the regulation of MKP-1 in cardiovascular disease, which may provide valuable therapeutic options.

The mechanism by which MEK/ERK regulates JNK and p38 activity in polyamine depleted IEC-6 cells during apoptosis

Polyamine-depletion inhibited apoptosis by activating ERK1/2, while, preventing JNK1/2 activation. MKP-1 knockdown by SiRNA increased ERK1/2, JNK1/2, and p38 phosphorylation and apoptosis. Therefore, we predicted that polyamines might regulate MKP1 via MEK/ERK and thereby apoptosis. We examined the role of MEK/ERK in the regulation of MKP1 and JNK, and p38 activities and apoptosis. Inhibition of MKP-1 activity with a pharmacological inhibitor, sanguinarine (SA), increased JNK1/2, p38, and ERK1/2 activities without causing apoptosis. However, pre-activation of these kinases by SA significantly increased camptothecin (CPT)-induced apoptosis suggesting different roles for MAPKs during survival and apoptosis. Inhibition of MEK1 activity prevented the expression of MKP-1 protein and augmented CPT-induced apoptosis, which correlated with increased activities of JNK1/2, caspases, and DNA fragmentation. Polyamine depleted cells had higher levels of MKP-1 protein and decreased JNK1/2 activity and apoptosis. Inhibition of MEK1 prevented MKP-1 expression and increased JNK1/2 and apoptosis. Phospho-JNK1/2, phospho-ERK2, MKP-1, and the catalytic subunit of PP2Ac formed a complex in response to TNF/CPT. Inactivation of PP2Ac had no effect on the association of MKP-1 and JNK1. However, inhibition of MKP-1 activity decreased the formation of the MKP-1, PP2Ac and JNK complex. Following inhibition by SA, MKP-1 localized in the cytoplasm, while basal and CPT-induced MKP-1 remained in the nuclear fraction. These results suggest that nuclear MKP-1 translocates to the cytoplasm, binds phosphorylated JNK and p38 resulting in dephosphorylation and decreased activity. Thus, MEK/ERK activity controls the levels of MKP-1 and, thereby, regulates JNK activity in polyamine-depleted cells.

Regulation of the expression of MKP-1 and MKP-2 by ERK MAP kinases in macrophages following LPS stimulation (P1214)

Abstract Although the MKP family plays an important role during host defense, the regulation of MKPs is poorly understood. We studied the expression of MKP-1 and MKP-2 in RAW264.7 cells during LPS stimulation. We found that pretreatment of cells with U0126 (a MEK1/2 inhibitor), substantially decreased MKP-1 and MKP-2 mRNA levels in LPS-stimulated macrophages. In contrast, SB203580 (a p38 inhibitor), had little effect on the levels of MKP-1 and MKP-2 mRNA. The combination of U0126 and SB203580 resulted in greater decreases in MKP-1 and MKP-2 mRNA levels, suggesting that p38 contributes to MKP-1 and MKP-2 induction in response to LPS. Interestingly, in the absence of LPS, SB203580 enhanced ERK and MEK1/2 activities, suggesting that p38 negatively regulates the ERK pathway by inhibiting a signaling event upstream of MEK1/2. LPS potently stimulated CREB phosphorylation mediated by p38, but not ERK, and enhanced phospho-CREB binding to MKP-1 and MKP-2 chromatins. Interestingly, LPS also enhanced the phosphorylation of RNA polymerase II at serine-2 at the MKP-1 chromatin in a manner dependent on CDK9 and ERK. At the protein level, both MKP-1 and MKP-2 underwent robust phosphorylation mediated by ERKs. Phosphorylation of both MKP-1 and MKP-2 substantially increased the stability of these proteins. Taken together, our studies suggest that the ERK pathway plays a predominant role in the regulation of MKP-1 and MKP-2 through both transcriptional and post-translational mechanisms.

Decreased Total MKP‐1 Protein Levels Predict Poor Prognosis in Breast Cancer

MKP-1 dephosphorylates and inactivates MAPKs, whose constitutive activations have been associated with human cancers. We found that total MKP-1 protein levels were decreased in 63.7 % of breast cancer tissues compared with the paired noncancerous breast tissues. Decreased MKP-1 protein levels were correlated with increased tumor stage and positive recurrence and were associated with poor survival, even when using a multivariate Cox regression model. Intriguingly, nuclear MKP-1 staining was positively correlated with ER status. In vitro, tamoxifen increased MKP-1 expression in ER-positive but not ER-negative breast cancer cells. ER-specific siRNA was able to attenuate tamoxifen-induced MKP-1 expression. Furthermore, tamoxifen prolonged the duration of MKP-1 elevation and the binding time of ER to the promoter of the MKP-1/DUSP-1 gene compared with estrogen. Our results suggest that alterations of MKP-1 may serve as a prognostic factor in breast cancer. In addition, the regulation of MKP-1 may be related to the ER.

The carboxyl-terminal domains of MKP-1 and MKP-2 have inhibitory effects on their phosphatase activity.

Both the mitogen-activated protein kinase (MAPK) phosphatases MKP-1 and MKP-2 exert important feedback control of MAPK-mediated signaling events. The function of MKP-1 and MKP-2 is regulated via complex mechanisms, ranging from increased transcription of the MKP-1 and MKP-2 genes to post-translational catalytic activation of MKP-1 and MKP-2 proteins upon binding to their substrate MAPKs. In addition, MKP-1 stability increases upon ERK-dependent phosphorylation of two serine residues in its C-terminus. The C-terminal regions of MKP-1 and MKP-2, but not those of other MKPs, are homologous. To investigate the role of this domain, we have deleted the C-terminal tails from MKP-1 and MKP-2 and examined the effect of these deletions on their enzymatic activity. C-terminally truncated MKP-1 and MKP-2 exhibited, both in vivo and in vitro, substantially greater phosphatase activity towards their substrate MAPKs than did the full-length counterparts. However, C-terminal truncations did not significantly change either their substrate affinity, or their substrate-mediated catalytic activation. Basal phosphatase activity of the truncated proteins was also significantly higher than that of the wild-type counterparts. Collectively, these results suggest that the C-terminal domain may potentially play a role in the regulation of MKP-1 and MKP-2.

Adhesion to Fibronectin Enhances MKP-1 Activation in Human Endothelial Cells

Integrin-mediated substrate adhesion of endothelial cells leads to intracellular signaling, including the activation of ERK 1/2 (extracellular regulated kinases 1 and 2), members of the mitogen-activated protein kinase (MAPK) family. MKP-1 is a dual-specificity protein phosphatase that may play an important role in regulating MAPK activity through dephosphorylation of threonine and tyrosine. Adhesion of human umbilical vein endothelial cells to fibronectin increased MKP-1 protein and mRNA levels, which reached a maximum at 60 min, while MAPK activity was maximal at 30 min. The MEK inhibitor PD98059 blocked activation of MAPK as well as the induction of MKP-1 during adhesion. The transcription inhibitor actinomycin D blocked MKP-1 induction and produced prolonged MAPK activation during adhesion. In contrast, endothelial adhesion to poly-l-lysine did not alter MAPK activity or MKP-1 levels. These findings demonstrate that integrin-mediated adhesion of endothelial cells to fibronectin results in transcriptional activation of MKP-1 through a MAPK-dependent mechanism. Regulation of MKP-1 by MAPK likely represents an important negative-feedback mechanism.