Circ_HIPK3 alleviates CoCl2-induced apoptotic injury in neuronal cells by depending on the regulation of the miR-222-3p/DUSP19 axis.

Circular RNA (circRNA) homeodomain-interacting protein kinase 3 (circ_HIPK3) has recently reported as regulator in spinal cord injury (SCI). The regulatory mechanism of circ_HIPK3 in SCI was further researched in this study. Circ_HIPK3 expression was inhibited by CoCl2 in AGE1.HN cells. The CoCl2-induced cell cycle arrest, cell proliferation inhibition and apoptosis promotion were mitigated by overexpression of circ_HIPK3. Circ_HIPK3 could target miR-222-3p and circ_HIPK3 repressed the CoCl2-induced neuronal cell injury by sponging miR-222-3p. DUSP19 was a target gene of miR-222-3p and circ_HIPK3 affected the expression of DUSP19 via binding to miR-222-3p. The regulation of circ_HIPK3 in CoCl2-induced injury of AGE1.HN cells was associated with the upregulation of DUSP19. Circ_HIPK3 acted as a pathogenic inhibitor in the progression of SCI via the miR-222-3p-mediated DUSP19 upregulation.

MAP Kinase Phosphatase-5 Deficiency Protects Against Pressure Overload-Induced Cardiac Fibrosis.

Cardiac fibrosis, a pathological condition due to excessive extracellular matrix (ECM) deposition in the myocardium, is associated with nearly all forms of heart disease. The processes and mechanisms that regulate cardiac fibrosis are not fully understood. In response to cardiac injury, macrophages undergo marked phenotypic and functional changes and act as crucial regulators of myocardial fibrotic remodeling. Here we show that the mitogen-activated protein kinase (MAPK) phosphatase-5 (MKP-5) in macrophages is involved in pressure overload-induced cardiac fibrosis. Cardiac pressure overload resulting from transverse aortic constriction (TAC) leads to the upregulation of Mkp-5 gene expression in the heart. In mice lacking MKP-5, p38 MAPK and JNK were hyperactivated in the heart, and TAC-induced cardiac hypertrophy and myocardial fibrosis were attenuated. MKP-5 deficiency upregulated the expression of the ECM-degrading matrix metalloproteinase-9 (Mmp-9) in the Ly6Clow (M2-type) cardiac macrophage subset. Consistent with in vivo findings, MKP-5 deficiency promoted MMP-9 expression and activity of pro-fibrotic macrophages in response to IL-4 stimulation. Furthermore, using pharmacological inhibitors against p38 MAPK, JNK, and ERK, we demonstrated that MKP-5 suppresses MMP-9 expression through a combined effect of p38 MAPK/JNK/ERK, which subsequently contributes to the inhibition of ECM-degrading activity. Taken together, our study indicates that pressure overload induces MKP-5 expression and facilitates cardiac hypertrophy and fibrosis. MKP-5 deficiency attenuates cardiac fibrosis through MAPK-mediated regulation of MMP-9 expression in Ly6Clow cardiac macrophages.

DUSP12 protects against hepatic ischemia-reperfusion injury dependent on ASK1-JNK/p38 pathway in vitro and in vivo.

Hepatic ischemia-reperfusion (I/R) injury is an important risk factor resulting in liver failure during liver surgery. However, there is still lack of effective therapeutic methods to treat hepatic I/R injury. DUSP12 is a member of the dual specific phosphatase (DUSP) family. Some DUSPs have been identified as being involved in the regulation of hepatic I/R injury. However, the role of DUSP12 during hepatic I/R injury is still unclear. In the present study, we observed a significant decrease in DUSP12 expression in a hepatic I/R injury mouse model in vivo and in hypoxia/reoxygenation (H/R) model in vitro. Using hepatocyte-specific DUSP12 knockout mice and DUSP12 transgenic mice, we demonstrated that DUSP12 apparently relieved I/R-induced liver injury. Moreover, DUSP12 inhibited hepatic inflammatory responses and alleviated apoptosis both in vitro and in vivo. Furthermore, we demonstrated that JNK and p38 activity, but not ERK1/2, was increased in the DUSP12-deficient mice and decreased in the DUSP12 transgenic mice under I/R condition. ASK1 was required for DUSP12 function in hepatic I/R injury and inhibition of ASK1 prevented inflammation and apoptosis in DUSP12-deficient hepatocytes and mice. In conclusion, DUSP12 protects against hepatic I/R injury and related inflammation and apoptosis. This regulatory role of DUSP12 is primarily through ASK1-JNK/p38 signaling pathway. Taken together, DUSP12 could be a potential therapeutic target for hepatic I/R injury.

Knockout of Dual-Specificity Protein Phosphatase 5 Protects Against Hypertension-Induced Renal Injury.

Dual-specificity protein phosphatase 5 (DUSP5) is a member of the tyrosine-threonine phosphatase family with the ability to dephosphorylate and inactivate extracellular signal-related kinase (ERK). The present study investigates whether knockout (KO) of Dusp5 improves renal hemodynamics and protects against hypertension-induced renal injury. The renal expression of DUSP5 was reduced, and the levels of phosphorylated (p) ERK1/2 and p-protein kinase C (PKC) α were elevated in the KO rats. KO of Dusp5 enhanced the myogenic tone of the renal afferent arteriole and interlobular artery in vitro with or without induction of deoxycorticosterone acetate-salt hypertension. Inhibition of ERK1/2 and PKC diminished the myogenic response to a greater extent in Dusp5 KO rats. Autoregulation of renal blood flow was significantly impaired in hypertensive wild-type (WT) rats but remained intact in Dusp5 KO animals. Proteinuria was markedly decreased in hypertensive KO versus WT rats. The degree of glomerular injury was reduced, and the expression of nephrin in the glomerulus was higher in hypertensive Dusp5 KO rats. Renal fibrosis and medullary protein cast formation were attenuated in hypertensive Dusp5 KO rats in association with decreased expression of monocyte chemoattractant protein 1, transforming growth factor-ß1, matrix metalloproteinase (MMP) 2, and MMP9. These results indicate that KO of Dusp5 protects against hypertension-induced renal injury, at least in part, by maintaining the myogenic tone of the renal vasculature and extending the range of renal blood flow autoregulation to higher pressures, which diminish glomerular injury, protein cast formation, macrophage infiltration, and epithelial-mesenchymal transformation in the kidney. SIGNIFICANCE STATEMENT: Dual-specificity protein phosphatase 5 (DUSP5) is a tyrosine-threonine phosphatase that inactivates extracellular signal-related kinase (ERK). We previously reported that knockout (KO) of Dusp5 enhanced the myogenic response and autoregulation in the cerebral circulation. The present study investigates whether KO of DUSP5 improves renal hemodynamics and protects against hypertension-induced renal injury. Downregulation of DUSP5 enhanced the myogenic tone of renal arteriole and artery and autoregulation of renal blood flow in association with reduced proteinuria, glomerular injury, and interstitial fibrosis after the induction of hypertension. Inhibition of ERK1/2 and protein kinase C diminished the myogenic response to a greater extent in Dusp5 KO rats. These results suggest that DUSP5 might be a viable drug target for the treatment of hypertension nephropathy.

JNK inactivation suppresses osteogenic differentiation, but robustly induces osteopontin expression in osteoblasts through the induction of inhibitor of DNA binding 4 (Id4).

Osteoblasts are versatile cells involved in multiple whole-body processes, including bone formation and immune response. Secretory amounts and patterns of osteoblast-derived proteins such as osteopontin (OPN) and osteocalcin (OCN) modulate osteoblast function. However, the regulatory mechanism of OPN and OCN expression remains unknown. Here, we demonstrate that p54/p46 c-jun N-terminal kinase (JNK) inhibition suppresses matrix mineralization and OCN expression but increases OPN expression in MC3T3-E1 cells and primary osteoblasts treated with differentiation inducers, including ascorbic acid, bone morphogenic protein-2, or fibroblast growth factor 2. Preinhibition of JNK before the onset of differentiation increased the number of osteoblasts that highly express OPN but not OCN (OPN-OBs), indicating that JNK affects OPN secretory phenotype at the early stage of osteogenic differentiation. Additionally, we identified JNK2 isoform as being critically involved in OPN-OB differentiation. Microarray analysis revealed that OPN-OBs express characteristic transcription factors, cell surface markers, and cytokines, including glycoprotein hormone α2 and endothelial cell-specific molecule 1. Moreover, we found that inhibitor of DNA binding 4 is an important regulator of OPN-OB differentiation and that dual-specificity phosphatase 16, a JNK-specific phosphatase, functions as an endogenous regulator of OPN-OB induction. OPN-OB phenotype was also observed following LPS from Porphyromonas gingivalis stimulation during osteogenic differentiation. Collectively, these results suggest that the JNK-Id4 signaling axis is crucial in the control of OPN and OCN expression during osteoblastic differentiation.-Kusuyama, J., Amir, M. S., Albertson, B. G., Bandow, K., Ohnishi, T., Nakamura, T., Noguchi, K., Shima, K., Semba, I., Matsuguchi, T. JNK inactivation suppresses osteogenic differentiation, but robustly induces osteopontin expression in osteoblasts through the induction of inhibitor of DNA binding 4 (Id4).

DUSP14 knockout accelerates cardiac ischemia reperfusion (IR) injury through activating NF-κB and MAPKs signaling pathways modulated by ROS generation.

Inflammation and oxidative stress are significantly involved in the progression of a variety of diseases, including myocardial ischemia/reperfusion (IR). In the present study, we hypothesized a protective role of dual-specificity phosphatase 14 (DUSP14) in myocardial IR, as well as the underlying molecular mechanism. The results indicated that DUSP14 was down-regulated following cardiac IR injury. Subsequently, the wild type (WT) and DUSP14-knockout (KO) mice were included to further reveal the potential role of DUSP14 in cardiac IR injury progression. DUSP14-KO mice exhibited increased infarction area and elevated apoptosis, as evidenced by the increased TUNEL-positive cells in ischemia heart following reperfusion compared to WT mice. Further, DUSP14-KO significantly aggregated cardiac dysfunction of mice after IR injury. Cardiac IR injury to DUSP14-KO mice led to markedly increased expression of pro-inflammatory cytokines and activated nuclear factor-κB (NF-κB) pathway in the heart in comparison to WT mice. Meanwhile, mitogen-activated protein kinases (MAPKs), including p38, ERK1/2 and JNK, were significantly activated by DUSO14-KO in mice after IR injury. Compared to WT mice, DUSP14-KO mice showed markedly increased oxidative stress markers in cardiac tissues, including malondialdehyde (MDA), NADPH oxidase-4 (NOX4) and p47, while decreased activities or expressions of anti-oxidants, such as glutathione (GSH), glutathione peroxidase (GPx), glutathion reductases (GR), superoxide dismutase (SOD) and hemeoxygenase-1 (HO-1). DUSP14-knockdown (KD) in primary cardiomyocytes using its specific siRNA sequence elevated hypoxia and reoxygenation (HR)-induced activation of NF-κB and MAPKs signaling pathways, and reactive oxygen species (ROS) generation. Intriguingly, pre-treatment of ROS scavenger, N-acetylcysteine (NAC), markedly abolished DUSP14-KD-augmented NF-κB and MAPKs activation in HR-stimulated primary cardiomyocytes. Together, the results above indicated that DUSP14 might be served as a positive regulator to attenuate cardiac IR injury. Suppressing DUSP14 exacerbated cardiac injury through activating NF-κB and MAPKs signaling pathways regulated by ROS production. Thus, DUSP14 could be a valuable target for developing treatments for myocardial IR injury.

Dual-Specificity Phosphatase 3 Deletion Protects Female, but Not Male, Mice from Endotoxemia-Induced and Polymicrobial-Induced Septic Shock.

Dual-specificity phosphatase 3 (DUSP3) is a small phosphatase with poorly known physiological functions and for which only a few substrates are known. Using knockout mice, we recently reported that DUSP3 deficiency confers resistance to endotoxin- and polymicrobial-induced septic shock. We showed that this protection was macrophage dependent. In this study, we further investigated the role of DUSP3 in sepsis tolerance and showed that the resistance is sex dependent. Using adoptive-transfer experiments and ovariectomized mice, we highlighted the role of female sex hormones in the phenotype. Indeed, in ovariectomized females and in male mice, the dominance of M2-like macrophages observed in DUSP3-/- female mice was reduced, suggesting a role for this cell subset in sepsis tolerance. At the molecular level, DUSP3 deletion was associated with estrogen-dependent decreased phosphorylation of ERK1/2 and Akt in peritoneal macrophages stimulated ex vivo by LPS. Our results demonstrate that estrogens may modulate M2-like responses during endotoxemia in a DUSP3-dependent manner.

Abnormal glycogen chain length pattern, not hyperphosphorylation, is critical in Lafora disease.

Lafora disease (LD) is a fatal progressive epilepsy essentially caused by loss-of-function mutations in the glycogen phosphatase laforin or the ubiquitin E3 ligase malin. Glycogen in LD is hyperphosphorylated and poorly hydrosoluble. It precipitates and accumulates into neurotoxic Lafora bodies (LBs). The leading LD hypothesis that hyperphosphorylation causes the insolubility was recently challenged by the observation that phosphatase-inactive laforin rescues the laforin-deficient LD mouse model, apparently through correction of a general autophagy impairment. We were for the first time able to quantify brain glycogen phosphate. We also measured glycogen content and chain lengths, LBs, and autophagy markers in several laforin- or malin-deficient mouse lines expressing phosphatase-inactive laforin. We find that: (i) in laforin-deficient mice, phosphatase-inactive laforin corrects glycogen chain lengths, and not hyperphosphorylation, which leads to correction of glycogen amounts and prevention of LBs; (ii) in malin-deficient mice, phosphatase-inactive laforin confers no correction; (iii) general impairment of autophagy is not necessary in LD We conclude that laforin's principle function is to control glycogen chain lengths, in a malin-dependent fashion, and that loss of this control underlies LD.

Sodium selenate treatment improves symptoms and seizure susceptibility in a malin-deficient mouse model of Lafora disease.

OBJECTIVE: To search for new therapies aimed at ameliorating the neurologic symptoms and epilepsy developing in patients with Lafora disease. METHODS: Lafora disease is caused by loss-of-function mutations in either the EPM2A or EPM2B genes. Epm2a-/- and Epm2b-/- mice display neurologic and behavioral abnormalities similar to those found in patients. Selenium is a potent antioxidant and its deficiency has been related to the development of certain diseases, including epilepsy. In this study, we investigated whether sodium selenate treatment improved the neurologic alterations and the hyperexcitability present in the Epm2b-/- mouse model. RESULTS: Sodium selenate ameliorates some of the motor and memory deficits and the sensitivity observed with pentylenetetrazol (PTZ) treatments in Epm2b-/- mice. Neuronal degeneration and gliosis were also diminished after sodium selenate treatment. SIGNIFICANCE: Sodium selenate could be beneficial for ameliorating some symptoms that present in patients with Lafora disease.

Dual-specificity phosphatase 5 controls the localized inhibition, propagation, and transforming potential of ERK signaling.

Deregulated extracellular signal-regulated kinase (ERK) signaling drives cancer growth. Normally, ERK activity is self-limiting by the rapid inactivation of upstream kinases and delayed induction of dual-specificity MAP kinase phosphatases (MKPs/DUSPs). However, interactions between these feedback mechanisms are unclear. Here we show that, although the MKP DUSP5 both inactivates and anchors ERK in the nucleus, it paradoxically increases and prolongs cytoplasmic ERK activity. The latter effect is caused, at least in part, by the relief of ERK-mediated RAF inhibition. The importance of this spatiotemporal interaction between these distinct feedback mechanisms is illustrated by the fact that expression of oncogenic BRAFV600E, a feedback-insensitive mutant RAF kinase, reprograms DUSP5 into a cell-wide ERK inhibitor that facilitates cell proliferation and transformation. In contrast, DUSP5 deletion causes BRAFV600E-induced ERK hyperactivation and cellular senescence. Thus, feedback interactions within the ERK pathway can regulate cell proliferation and transformation, and suggest oncogene-specific roles for DUSP5 in controlling ERK signaling and cell fate.

Loss of laforin or malin results in increased Drp1 level and concomitant mitochondrial fragmentation in Lafora disease mouse models.

Lafora disease (LD) is an autosomal recessive form of a fatal disorder characterized by the myoclonus epilepsy, ataxia, psychosis, dementia, and dysarthria. A hallmark of LD is the presence of abnormal glycogen inclusions called Lafora bodies in the affected tissues including the neurons. LD can be caused by defects either in the laforin phosphatase coded by the EPM2A gene or in the malin E3 ubiquitin ligase coded by the NHLRC1 gene. The mouse models of LD, created by the targeted disruption of the LD genes, display several neurodegenerative changes. Prominent among them are the autophagic defects, abnormally large lysosomes, neurofibrillary tangles, amyloid beta deposits, and abnormal mitochondria. However, whether or not such neurodegenerative changes are a direct effect of the loss of laforin/malin was not unequivocally established. Here, we show that laforin- or malin-deficient neurons and fibroblasts display a significantly higher number of fragmented mitochondria. Loss of laforin or malin resulted in increased levels of the mitochondrial fission GTPase Drp1, its enhanced mitochondrial targeting, and increased intracellular calcium levels. Intriguingly, laforin and malin display opposite effects on the cellular level of parkin, an ubiquitin ligase of Drp1; loss of laforin led to reduced levels of parkin while the loss of malin resulted in increased parkin levels. Laforin and malin, however, interact with and positively regulate the activity of parkin, thus explaining the molecular basis of increased Drp1 levels in LD tissues. Our results suggest that laforin and malin are novel regulators of mitochondrial quality control pathway and that the mitochondrial dysfunction resulting from the increased Drp1 levels could underlie neuropathology in LD.

Inflammation in Lafora Disease: Evolution with Disease Progression in Laforin and Malin Knock-out Mouse Models.

Lafora progressive myoclonus epilepsy (Lafora disease, LD) is a fatal rare autosomal recessive neurodegenerative disorder characterized by the accumulation of insoluble ubiquitinated polyglucosan inclusions in the cytoplasm of neurons, which is most commonly associated with mutations in two genes: EPM2A, encoding the glucan phosphatase laforin, and EPM2B, encoding the E3-ubiquitin ligase malin. The present study analyzes possible inflammatory responses in the mouse lines Epm2a -/- (laforin knock-out) and Epm2b -/- (malin knock-out) with disease progression. Increased numbers of reactive astrocytes (expressing the GFAP marker) and microglia (expressing the Iba1 marker) together with increased expression of genes encoding cytokines and mediators of the inflammatory response occur in both mouse lines although with marked genotype differences. C3ar1 and CxCl10 messenger RNAs (mRNAs) are significantly increased in Epm2a -/- mice aged 12 months when compared with age-matched controls, whereas C3ar1, C4b, Ccl4, CxCl10, Il1b, Il6, Tnfα, and Il10ra mRNAs are significantly upregulated in Epm2b -/- at the same age. This is accompanied by increased protein levels of IL1-ß, IL6, TNFα, and Cox2 particularly in Epm2b -/- mice. The severity of inflammatory changes correlates with more severe clinical symptoms previously described in Epm2b -/- mice. These findings show for the first time increased innate inflammatory responses in a neurodegenerative disease with polyglucosan intraneuronal deposits which increase with disease progression, in a way similar to what is seen in neurodegenerative diseases with abnormal protein aggregates. These findings also point to the possibility of using anti-inflammatory agents to mitigate the degenerative process in LD.

Knockdown of Cyclin-Dependent Kinase Inhibitor 3 Inhibits Proliferation and Invasion in Human Gastric Cancer Cells.

Cyclin-dependent kinase inhibitor 3 (CDKN3) has been reported to promote tumorigenesis. Since it is unclear whether CDKN3 participates in the development of human gastric cancer, this study assessed the association between CDKN3 expression and cell biological function and demonstrated the clinical significance and prognosis of CDKN3 in human gastric cancer. In this study, we found that CDKN3 showed a high expression in 35 paired human gastric cancer tissues and was correlated with poor patient survival, AJCC clinical staging, and recurrence. Silencing of CDKN3 in human gastric cancer cells can significantly reduce proliferation, migration, invasion, and adhesion abilities. Also, silencing of CDKN3 in human gastric cancer cells can induce G0-G1 cell cycle arrest and apoptosis. Detection of cell cycle marker expression showed that CDKN3 knockdown promotes cell cycle arrest by decreasing the expression of CDK2, CDC25A, CCNB1, and CCNB2 in human gastric cancer cells. The results of this study will help elucidate the oncogene function of CDKN3 in human gastric cancer.

Statins affect ETS1-overexpressing triple-negative breast cancer cells by restoring DUSP4 deficiency.

We investigated the molecular mechanisms underlying statin-induced growth suppression of triple-negative breast cancer (TNBC) that overexpress the transcription factor ets proto-oncogene 1(ets-1) and downregulate dual specific protein phosphatase 4(dusp4) expression. We examined the gene expression of BC cell lines using the nCounter expression assay, MTT viability assay, cell proliferation assay and Western blot to evaluate the effects of simvastatin. Finally, we performed cell viability testing in TNBC cell line-transfected DUSP4. We demonstrated that ETS1 mRNA and protein were overexpressed in TNBC cells compared with other BC cell lines (P = <0.001) and DUSP4 mRNA was downregulated (P = <0.001). MTT viability assay showed that simvastatin had significant antitumor activity (P = 0.002 in 0.1 µM). In addition, simvastatin could restore dusp4 deficiency and suppress ets-1 expression in TNBC. Lastly, we found that si-DUSP4 RNA transfection overcame the antitumor activity of statins. MAPK pathway inhibitor, U0126 and PI3KCA inhibitor LY294002 also decreased levels of ets-1, phosphor-ERK and phosphor-AKT on Western blot assay. Accordingly, our study indicates that simvastatin potentially affects the activity of transcriptional factors such as ets-1 and dusp4 through the MAPK pathway. In conclusion, statins might be potential candidates for TNBC therapy reducing ets-1 expression via overexpression of dusp4.

Differential Roles for DUSP Family Members in Epithelial-to-Mesenchymal Transition and Cancer Stem Cell Regulation in Breast Cancer.

Dual-specificity phosphatases (DUSPs) dephosphorylate threonine/serine and tyrosine residues on their substrates. Here we show that DUSP1, DUSP4, and DUSP6 are involved in epithelial-to-mesenchymal transition (EMT) and breast cancer stem cell (CSC) regulation. DUSP1, DUSP4, and DUSP6 are induced during EMT in a PKC pathway signal-mediated EMT model. We show for the first time that the key chromatin-associated kinase PKC-θ directly regulates a subset of DUSP family members. DUSP1, DUSP4, and DUSP6 globally but differentially co-exist with enhancer and permissive active histone post-translational modifications, suggesting that they play distinct roles in gene regulation in EMT/CSCs. We show that nuclear DUSP4 associates with the key acetyltransferase p300 in the context of the chromatin template and dynamically regulates the interplay between two key phosphorylation marks: the 1834 (active) and 89 (inhibitory) residues central to p300's acetyltransferase activity. Furthermore, knockdown with small-interfering RNAs (siRNAs) shows that DUSP4 is required for maintaining H3K27ac, a mark mediated by p300. DUSP1, DUSP4, and DUSP6 knockdown with siRNAs shows that they participate in the formation of CD44hi/CD24lo/EpCAM+ breast CSCs: DUSP1 knockdown reduces CSC formation, while DUSP4 and DUSP6 knockdown enhance CSC formation. Moreover, DUSP6 is overexpressed in patient-derived HER2+ breast carcinomas compared to benign mammary tissue. Taken together, these findings illustrate novel pleiotropic roles for DUSP family members in EMT and CSC regulation in breast cancer.

DUSP16 ablation arrests the cell cycle and induces cellular senescence.

Dual-specificity phosphatases (DUSPs) are a family of protein phosphatases that dephosphorylate both phosphotyrosine and phosphoserine/phosphothreonine residues. DUSPs are de-regulated in many human diseases, including cancers. However, the function of DUSPs in tumorigenesis remains largely unknown. Here, using short hairpin RNA-based gene knockdown, we found that several members of the DUSP family play critical roles in regulating cell proliferation. In particular, we showed that DUSP16 ablation leads to a G1/S transition arrest, reduced incorporation of 5-bromodeoxyuridine, enhanced senescence-associated ß-galactosidase activity, and formation of senescence-associated heterochromatic foci. Mechanistically, DUSP16 silencing causes cellular senescence by activating the tumor suppressors p53 and Rb. The phosphatase activity of DUSP16 is necessary for antagonizing cellular senescence. Importantly, the expression levels of DUSP16 are up-regulated in human liver cancers, and are positively correlated with tumor cell proliferation. Taken together, our findings indicate that DUSP16 plays a role in tumorigenesis by protecting cancer cells from senescence.

Yvh1 protein phosphatase is required for pre-autophagosomal structure formation after TORC1 inactivation.

The pre-autophagosomal structure (PAS) is a putative site for autophagosome formation in budding yeast. Upon nutrient depletion or rapamycin treatment, target of rapamycin complex 1 (TORC1) becomes inactive, inducing PAS formation and autophagy. Here, we show that Yvh1 phosphatase is critical for PAS formation, but not autophagy induction, after TORC1 inactivation.

DUSP4 deficiency caused by promoter hypermethylation drives JNK signaling and tumor cell survival in diffuse large B cell lymphoma.

The epigenetic dysregulation of tumor suppressor genes is an important driver of human carcinogenesis. We have combined genome-wide DNA methylation analyses and gene expression profiling after pharmacological DNA demethylation with functional screening to identify novel tumor suppressors in diffuse large B cell lymphoma (DLBCL). We find that a CpG island in the promoter of the dual-specificity phosphatase DUSP4 is aberrantly methylated in nodal and extranodal DLBCL, irrespective of ABC or GCB subtype, resulting in loss of DUSP4 expression in 75% of >200 examined cases. The DUSP4 genomic locus is further deleted in up to 13% of aggressive B cell lymphomas, and the lack of DUSP4 is a negative prognostic factor in three independent cohorts of DLBCL patients. Ectopic expression of wild-type DUSP4, but not of a phosphatase-deficient mutant, dephosphorylates c-JUN N-terminal kinase (JNK) and induces apoptosis in DLBCL cells. Pharmacological or dominant-negative JNK inhibition restricts DLBCL survival in vitro and in vivo and synergizes strongly with the Bruton's tyrosine kinase inhibitor ibrutinib. Our results indicate that DLBCL cells depend on JNK signaling for survival. This finding provides a mechanistic basis for the clinical development of JNK inhibitors in DLBCL, ideally in synthetic lethal combinations with inhibitors of chronic active B cell receptor signaling.

MAPK phosphatase 7 regulates T cell differentiation via inhibiting ERK-mediated IL-2 expression.

Members of the MAPK phosphatase (MKP) protein family play critical roles in immune responses through differential regulation of MAPK activation. In this study, we show that MKP7, also known as dual-specificity phosphatase 16, was required for CD4(+) T cell responses in vivo. Mkp7(-/-) CD4(+) T cells exhibited enhanced ERK and JNK activation, and produced increased amount of IL-2 compared with Mkp7(+/+) cells upon activation. Mkp7(-/-) CD4(+) T cells were selectively defective in Th17 differentiation in vitro, which was rescued by blocking IL-2 or inhibition of ERK activation. Furthermore, mice carrying Mkp7(-/-) T cells were deficient in generation of Th17 and T follicular helper cells in vivo, and were resistant to autoimmune experimental encephalomyelitis. Our results thus demonstrate an essential role of MKP7 in effector T cell function.