Calcium saccharate/DUSP6 suppresses renal cell carcinoma glycolytic metabolism and boosts sunitinib efficacy via the ERK-AKT pathway.

Current therapeutic options for renal cell carcinoma (RCC) are very limited, which is largely due to inadequate comprehension of molecular pathological mechanisms as well as RCC's resistance to chemotherapy. Dual-specificity phosphatase 6 (DUSP6) has been associated with numerous human diseases. However, its role in RCC is not well understood. Here, we show that diminished DUSP6 expression is linked to RCC progression and unfavorable prognosis. Mechanistically, DUSP6 serves as a tumor suppressor in RCC by intervening the TAF10 and BSCL2 via the ERK-AKT pathway. Further, DUSP6 is also transcriptionally regulated by HNF-4a. Moreover, docking experiments have indicated that DUSP6 expression is enhanced when bound by Calcium saccharate, which also inhibits RCC cell proliferation, metabolic rewiring, and sunitinib resistance. In conclusion, our study identifies Calcium saccharate as a prospective pharmacological therapeutic approach for RCC.

Long non-coding RNA NORAD regulates megakaryocyte differentiation and proplatelet formation via the DUSP6/ERK signaling pathway.

Megakaryopoiesis and platelet production is a complex process that is underpotential regulation at multiple stages. Many long non-coding RNAs (lncRNAs) are distributed in hematopoietic stem cells and platelets. lncRNAs may play important roles as key epigenetic regulators in megakaryocyte differentiation and proplatelet formation. lncRNA NORAD can affect cell ploidy by sequestering PUMILIO proteins, although its direct effect on megakaryocyte differentiation and thrombopoiesis is still unknown. In this study, we demonstrate NORAD RNA is highly expressed in the cytoplasm during megakaryocyte differentiation. Interestingly, we identified for the first time that NORAD has a strong inhibitory effect on megakaryocyte differentiation and proplatelet formation from cultured megakaryocytes. DUSP6/ERK1/2 pathway is activated in response to NORAD knockdown during megakaryocytopoiesis, which is achieved by sequestering PUM2 proteins. Finally, compared with the wild-type control mice, NORAD knockout mice show a faster platelet recovery after severe thrombocytopenia induced by 6 Gy total body irradiation. These findings demonstrate lncRNA NORAD has a key role in regulating megakaryocyte differentiation and thrombopoiesis, which provides a promising molecular target for the treatment of platelet-related diseases such as severe thrombocytopenia.

Inactivation of ERK1/2 Signaling in Dopaminergic Neurons by Map Kinase Phosphatase MKP3 Regulates Dopamine Signaling and Motivation for Cocaine.

The mesolimbic dopamine system is a crucial component of reward and reinforcement processing, including the psychotropic effects of drugs of abuse such as cocaine. Drugs of abuse can activate intracellular signaling cascades that engender long-term molecular changes to brain reward circuitry, which can promote further drug use. However, gaps remain about how the activity of these signaling pathways, such as ERK1/2 signaling, can affect cocaine-induced neurochemical plasticity and cocaine-associated behaviors specifically within dopaminergic cells. To enable specific modulation of ERK1/2 signaling in dopaminergic neurons of the ventral tegmental area, we utilize a viral construct that Cre dependently expresses Map kinase phosphatase 3 (MKP3) to reduce the activity of ERK1/2, in combination with transgenic rats that express Cre in tyrosine hydroxylase (TH)-positive cells. Following viral transfection, we found an increase in the surface expression of the dopamine transporter (DAT), a protein associated with the regulation of dopamine signaling, dopamine transmission, and cocaine-associated behavior. We found that inactivation of ERK1/2 reduced post-translational phosphorylation of the DAT, attenuated the ability of cocaine to inhibit the DAT, and decreased motivation for cocaine without affecting associative learning as tested by conditioned place preference. Together, these results indicate that ERK1/2 signaling plays a critical role in shaping the dopamine response to cocaine and may provide additional insights into the function of dopaminergic neurons. Further, these findings lay important groundwork toward the assessment of how signaling pathways and their downstream effectors influence dopamine transmission and could ultimately provide therapeutic targets for treating cocaine use disorders.

Acute Endoplasmic Reticulum Stress Suppresses Hepatic Gluconeogenesis by Stimulating MAPK Phosphatase 3 Degradation.

Drug-induced liver injury (DILI) is a widespread and harmful disease, and is closely linked to acute endoplasmic reticulum (ER) stress. Previous reports have shown that acute ER stress can suppress hepatic gluconeogenesis and even leads to hypoglycemia. However, the mechanism is still unclear. MAPK phosphatase 3 (MKP-3) is a positive regulator for gluconeogenesis. Thus, this study was conducted to investigate the role of MKP-3 in the suppression of gluconeogenesis by acute ER stress, as well as the regulatory role of acute ER stress on the expression of MKP-3. Results showed that acute ER stress induced by tunicamycin significantly suppressed gluconeogenesis in both hepatocytes and mouse liver, reduced glucose production level in hepatocytes, and decreased fasting blood glucose level in mice. Additionally, the protein level of MKP-3 was reduced by acute ER stress in both hepatocytes and mouse liver. Mkp-3 deficiency eliminated the inhibitory effect of acute ER stress on gluconeogenesis in hepatocytes. Moreover, the reduction effect of acute ER stress on blood glucose level and hepatic glucose 6-phosphatase (G6pc) expression was not observed in the liver-specific Mkp-3 knockout mice. Furthermore, activation of protein kinase R-like ER kinase (PERK) decreased the MKP-3 protein level, while inactivation of PERK abolished the reduction effect of acute ER stress on the MKP-3 protein level in hepatocytes. Taken together, our study suggested that acute ER stress could suppress hepatic gluconeogenesis by stimulating MKP-3 degradation via PERK, at least partially. Thus, MKP-3 might be a therapeutic target for DILI-related hypoglycemia.

LncRNA SPRY4-IT1 regulates 16HBE cell malignant transformation induced by particulate matter through DUSP6-ERK1/2-Chk1 signaling pathway.

Particulate matter (PM), one of the most serious air contaminants, could easily pass through the airway and deposit at the deep alveoli. Thus, it might trigger respiratory diseases like inflammation, asthma and lung cancer on human. Long non-coding RNAs (lncRNAs) are considered as important regulator in promotion and progression of diverse cancers. However, the molecular mechanism of lncRNAs mediating PM-induced lung carcinogenesis remains unclear. In this study, we established a 16HBE malignant transformed cell induced by PM (Cells were treated with 20 µg/ml PM, which named PM-T cells) and explored the roles and mechanisms of lncRNAs in the malignant transformation induced by PM. Compared with 16HBE cells, various biological functions were changed in PM-T cells, such as cell proliferation, migration, cell cycle and apoptosis. LncRNA SPRY4-IT1 was significant down-regulated expression and associated with these biological effects. Our results showed that lncRNA SPRY4-IT1 overexpression reversed these functional changes mentioned above. The further studies indicated that lncRNA SPRY4-IT1 involved in PM-induced cell transformation by modulating Chk1 expression via negative regulation of DUSP6-ERK1/2. In conclusion, our studies suggested that lncRNA SPRY4-IT1 played the role as a tumor suppressor gene and might mediate 16HBE cells malignant transformation induced by PM through regulating DUSP6-ERK1/2-Chk1 signaling pathway.

BOP1 Promotes Prostate Cancer through the DUSP6/MAPK Pathway

Background: Nucleolar prominence is a biomarker of prostate cancer (CaP), and the nucleolar protein block of proliferation 1 (BOP1) participates in the development of CaP, which has great significance for CaP therapy. Thus, this study explored the mechanism of BOP1 in CaP development. Methods: BOP1 expression levels in the tumor tissues of CaP patients and in PC3 tumor cells were determined. The viability, apoptosis rate of PC3 cells, and apoptosis-related proteins levels were determined to explore the effect of BOP1 on tumor-cell growth in vitro. BOP1 function in the metastasis of PC3 cells was further assessed by Transwell experiment. We also studied the influence of BOP1 on the expression of mitogen-activated protein kinase (MAPK) pathway-related proteins and investigated the regulatory effect of BOP1 on dual-specificity phosphatase 6 (DUSP6). Results: BOP1 expression was upregulated in the tumor tissues and PC3 cells of CaP patients. BOP1 knockout reduced the activity of PC3 cells and induced apoptosis, significantly inhibiting the metastasis of PC3 cells. DUSP6 was overexpressed in tumor tissues and PC3 cells. BOP1 knockout inhibited DUSP6 expression and the MAPK pathway. DUSP6 overexpression reversed the inhibition of BOP1 siRNA (si-BOP1) on PC3 cells and the activated MAPK signaling pathway. Conclusions: This finding demonstrated that BOP1 promoted CaP progression by regulating the DUSP6/MAPK pathway (AU)

miR-101-5p suppresses trophoblast cell migration and invasion via modulating the DUSP6-ERK1/2 axis in preeclampsia.

PURPOSE: Dysregulated behaviors of trophoblast cells leading to defective placentation are considered the main cause of preeclampsia (PE). Abnormal miRNA expression profiles have been observed in PE placental tissue, indicating the significant role of miRNAs in PE development. This study aimed to investigate the expression of miR-101-5p in PE placental tissue and its biological functions. METHODS: The expression of miR-101-5p in placental tissue was detected by quantitative real-time PCR (qRT-PCR). The localization of miR-101-5p in term placental tissue and decidual tissue was determined by the fluorescence in situ hybridization (FISH)-immunofluorescence (IF) double labeling assay. The effect of miR-101-5p on the migration, invasion, proliferation, and apoptosis of the HTR8/SVneo trophoblast cells was investigated. Online databases combined with transcriptomics were used to identify potential target genes and related pathways of miR-101-5p. Finally, the interaction between miR-101-5p and the target gene was verified by qRT-PCT, WB, dual-luciferase reporter assay, and rescue experiments. RESULTS: The study found that miR-101-5p was upregulated in PE placental tissue compared to normal controls and was mainly located in various trophoblast cell subtypes in placental and decidual tissues. Overexpression of miR-101-5p impaired the migration and invasion of HTR8/SVneo cells. DUSP6 was identified as a potential downstream target of miR-101-5p. The expression of miR-101-5p was negatively correlated with DUSP6 expression in HTR8/SVneo cells, and miR-101-5p directly bound to the 3' UTR region of DUSP6. DUSP6 upregulation rescued the migratory and invasive abilities of HTR8/SVneo cells in the presence of miR-101-5p overexpression. Additionally, miR-101-5p downregulated DUSP6, resulting in enhanced ERK1/2 phosphorylation. CONCLUSION: This study revealed that miR-101-5p inhibits the migration and invasion of HTR8/SVneo cells by regulating the DUSP6-ERK1/2 axis, providing a new molecular mechanism for the pathogenesis of PE.

Quercetin induces dual specificity phosphatase 5 via serum response factor.

The phytochemical quercetin has gained attention for its antiinflammatory and anti-tumorigenic properties in various types of cancer. Tumorigenesis involves the aberrant regulation of kinase/phosphatase, highlighting the importance of maintaining homeostasis. Dual Specificity Phosphatase (DUSP) plays a crucial role in controlling the phosphorylation of ERK. The current study aimed to clone the DUSP5 promoter, and investigate its transcriptional activity in the presence of quercetin. The results revealed that quercetin-induced DUSP5 expression is associated with the serum response factor (SRF) binding site located in the DUSP5 promoter. The deletion of this site abolished the luciferase activity induced by quercetin, indicating its vital role in quercetin-induced DUSP5 expression. SRF protein is a transcription factor that potentially contributes to quercetin-induced DUSP5 expression at the transcriptional level. Additionally, quercetin enhanced SRF binding activity without changing its expression. These findings provide evidence of how quercetin affects anti-cancer activity in colorectal tumorigenesis by inducing SRF transcription factor activity, thereby increasing DUSP5 expression at the transcriptional level. This study highlights the importance of investigating the molecular mechanisms underlying the anti-cancer properties of quercetin, and suggests its potential use in cancer therapy. [BMB Reports 2023; 56(9): 508-513].

DUSP6 is a memory retention feedback regulator of ERK signaling for cellular resilience of human pluripotent stem cells in response to dissociation.

Cultured human pluripotent stem cells (hPSCs) grow as colonies that require breakdown into small clumps for further propagation. Although cell death mechanism by single-cell dissociation of hPSCs has been well defined, how hPSCs respond to the deadly stimulus and recover the original status remains unclear. Here we show that dissociation of hPSCs immediately activates ERK, which subsequently activates RSK and induces DUSP6, an ERK-specific phosphatase. Although the activation is transient, DUSP6 expression persists days after passaging. DUSP6 depletion using the CRISPR/Cas9 system reveals that DUSP6 suppresses the ERK activity over the long term. Elevated ERK activity by DUSP6 depletion increases both viability of hPSCs after single-cell dissociation and differentiation propensity towards mesoderm and endoderm lineages. These findings provide new insights into how hPSCs respond to dissociation in order to maintain pluripotency.

LncTUG1 ameliorates renal tubular fibrosis in experimental diabetic nephropathy through the miR-145-5p/dual-specificity phosphatase 6 axis.

The renal interstitial fibrosis contributes to the progression and deterioration of diabetic nephropathy (DN). Long noncoding RNA taurine-up-regulated gene 1 (TUG1) in kidneys may be down-regulated by hyperglycemia. We aim to explore its role in tubular fibrosis caused by high glucose and the possible target genes of TUG1. In this study, a streptozocin-induced accelerated DN mouse model and a high glucose-stimulated HK-2 cells model was established to evaluate TUG1 expression. Potential targets of TUG1 were analyzed by online tools and confirmed by luciferase assay. A rescue experiment and gene silencing assay were used to investigate whether TUG1 plays its regulation role via miR-145-5p/dual-specificity phosphatase 6 (DUSP6) in HK2 cells. The effects of TUG1 on inflammation and fibrosis in high glucose treated tubular cells were evaluated by in vitro study, as well as in vivo DN mice model through AAV-TUG1 delivery. Results showed TUG1was downregulated in HK2 cells incubated with high glucose while miR-145-5p was upregulated. Overexpression of TUG1 alleviated renal injury by suppressing inflammation and fibrosis in vivo. Overexpression of TUG1 inhibited HK-2 cell fibrosis and relieved the inflammation. A mechanism study demonstrated that TUG1 directly sponged to miR-145-5p, and DUSP6 was identified as a target downstream of miR-145-5p. In addition, miR-145-5 overexpression and DUSP6 inhibition countervailed the impacts of TUG1. Our findings revealed that TUG1 overexpression alleviates kidney injury in DN mice and decreases the inflammatory response and fibrosis of high glucose-stimulated HK-2 cells via miR-145-5p/DUSP6 axis.

N6-methyadenosine modified SUV39H2 regulates homologous recombination through epigenetic repression of DUSP6 in gastric cancer.

Despite many advances in treatment over the past few years, the poor 5-year survival rate and high recurrence rate of gastric cancer (GC) remain unsatisfactory. As the most abundant epigenetic modification in the eukaryotic mRNA, N6-methyladenosine (m6A) methylation participates in tumor progression and tissue development. During tumor progression, DNA damage repair mechanisms can be reprogrammed to give new growth advantages on tumor clones whose genomic integrity is disturbed. Here we detected the elevated SUV39H2 expression in GC tissues and cell lines. Functionally, SUV39H2 promoted GC proliferation and inhibited apoptosis in vitro and in vivo. Mechanistically, METTL3-mediated m6A modification promotes mRNA stability of SUV39H2 in an IGF2BP2 dependent manner, resulting in upregulated mRNA expression of SUV39H2. As a histone methyltransferase, SUV39H2 was verified to increase the phosphorylation level of ATM through transcriptional repression of DUSP6, thereby promoting HRR and ultimately inhibiting GC chemosensitivity to cisplatin. Collectively, these results indicate the specific mechanism of m6A-modified SUV39H2 as a histone methyltransferase promoting HRR to inhibit the chemosensitivity of GC. SUV39H2 is expected to become a key target in the precision targeted therapy of GC.

DUSP6 mediates resistance to JAK2 inhibition and drives leukemic progression.

Myeloproliferative neoplasms (MPNs) exhibit a propensity for transformation to secondary acute myeloid leukemia (sAML), for which the underlying mechanisms remain poorly understood, resulting in limited treatment options and dismal clinical outcomes. Here, we performed single-cell RNA sequencing on serial MPN and sAML patient stem and progenitor cells, identifying aberrantly increased expression of DUSP6 underlying disease transformation. Pharmacologic dual-specificity phosphatase (DUSP)6 targeting led to inhibition of S6 and Janus kinase (JAK)-signal transducer and activator of transcription (STAT) signaling while also reducing inflammatory cytokine production. DUSP6 perturbation further inhibited ribosomal S6 kinase (RSK)1, which we identified as a second indispensable candidate associated with poor clinical outcome. Ectopic expression of DUSP6 mediated JAK2-inhibitor resistance and exacerbated disease severity in patient-derived xenograft (PDX) models. Contrastingly, DUSP6 inhibition potently suppressed disease development across Jak2V617F and MPLW515L MPN mouse models and sAML PDXs without inducing toxicity in healthy controls. These findings underscore DUSP6 in driving disease transformation and highlight the DUSP6-RSK1 axis as a vulnerable, druggable pathway in myeloid malignancies.

Abundance of Dual Specificity Phosphatase (DUSP) 1 and DUSP6 mRNA Is Regulated by Hippo Signaling in Bovine Pre-ovulatory Granulosa Cells.

Ovulatory disorders are a major cause of infertility in humans as well as economically important species. In physiological conditions, the LH surge induces the expression of epidermal growth factor (EGF)-like ligands that activate the EGR receptor (EGFR) and subsequently the mitogen-activated protein kinase (MAPK) pathway. The magnitude and duration of MAPK phosphorylation are regulated by dual-specificity phosphatases (DUSPs). Besides this well-known cascade, other signaling pathways such as the Hippo pathway modulate the ovulatory cascade and are reported to crosstalk with MAPK signaling. Here, we tested the hypothesis that LH and the Hippo pathway regulate DUSP expression in bovine pre-ovulatory granulosa cells. The abundance of DUSP6 mRNA but not DUSP1 was decreased by LH (P < 0.05). Cells were then pre-treated (1 h) with two inhibitors of Hippo signaling, verteporfin (1 µM) or peptide-17 (25 µM), before exposure for 6 h to LH or to EGF. Treatment with verteporfin increased DUSP1 mRNA levels (P < 0.05) in the presence or absence of EGF or LH and treatment with peptide-17 increased DUSP6 and not DUSP1 mRNA abundance. These data indicate a differential regulation of DUSP1 and DUSP6 mRNA by the Hippo pathway in pre-ovulatory granulosa cells, which suggests a complex control of MAPK signaling around ovulation.

A positive feedback loop of ARF6 activates ERK1/2 signaling pathway via DUSP6 silencing to promote pancreatic cancer progression.

ERK1/2 are essential proteins mediating mitogen-activated protein kinase signaling downstream of RAS in pancreatic adenocarcinoma (PDAC). Our previous study reveals that ARF6 plays a positive regulatory role in ERK1/2 pathway in a feedback loop manner. A significant part of the literature on ARF6 has emphasized its oncogenic effect as an essential downstream molecule of ERK1/2, and no research has been done on the regulation mechanisms of the feedback loop between ARF6 and the ERK1/2 signaling pathway. In the present study, we explore the gene network downstream of ARF6 and find that DUSP6 may be the critical signal molecule in the positive feedback loop between ARF6 and ERK1/2. Specifically, to elucidate the negative correlations between ARF6 and DUSP6 in pancreatic cancer, we examine their expressions in pancreatic cancer tissues by immunohistochemical staining. Then the impact of DUSP6 on the proliferation and apoptosis of PDAC cells are investigated by gain-of-function and loss-of-function approaches. Mechanism explorations uncover that ARF6 suppresses the expression of DUSP6, which is responsible for the dephosphorylation of ERK1/2. Altogether, these results indicate that DUSP6 plays a tumor-suppressive role and acts as an intermediate molecule between ARF6 and ERK1/2 in PDAC cells, thereby forming a positive feedback loop.

Neuroprotective Effect of Dioscin against Parkinson's Disease via Adjusting Dual-Specificity Phosphatase 6 (DUSP6)-Mediated Oxidative Stress.

Exploration of lead compounds against Parkinson's disease (PD), a neurodegenerative disease, is of great important. Dioscin, a bioactive natural product, shows various pharmacological effects. However, the activities and mechanisms of dioscin against PD have not been well investigated. In this study, the tests on 6-hydroxydopamine (6-OHDA)-induced PC12 cells and rats were carried out. The results showed that dioscin dramatically improved cell viability, decreased reactive oxygen species (ROS) levels, improved motor behavior and tyrosine hydroxylase(TH) levels and restored the levels of glutathione (GSH) and malondialdehyde (MDA) in rats. Mechanism investigation showed that dioscin not only markedly increased the expression level of dual- specificity phosphatase 6 (DUSP6) by 1.87-fold in cells and 2.56-fold in rats, and decreased phospho-extracellular regulated protein kinases (p-ERK) level by 2.12-fold in cells and 2.34-fold in rats, but also increased the levels of nuclear factor erythroid2-related factor 2 (Nrf2), hemeoxygenase-1 (HO-1), superoxide dismutase (SOD) and decreased the levels of kelch-1ike ECH-associated protein l (Keap1) in vitro and in vivo. Furthermore, DUSP6 siRNA transfection experiment in PC12 cells validated the protective effects of dioscin against PD via regulating DUSP6 to adjust the Keap1/Nrf2 pathway. Our data supported that dioscin has protection against PD in regulating oxidative stress via DUSP6 signal, which should be considered as an efficient candidate for the treatment of PD in the future.

Xenopus Dusp6 modulates FGF signaling to precisely pattern pre-placodal ectoderm.

Pre-placodal ectoderm (PPE), a horseshoe-shaped narrow region formed during early vertebrate development, gives rise to multiple types of sensory organs and ganglia. For PPE induction, a certain level of FGF signal activation is required. However, it is difficult to reproducibly induce the narrow region with variations in gene expression, including FGF, among individuals. An intracellular regulatory factor of FGF signaling, Dusp6, is expressed by FGF signal activation and inactivates a downstream regulator, ERK1/2, in adult tissues; however, its role in early development is not well known. Here, we reveal that Dusp6 is expressed in an FGF-dependent manner in Xenopus PPE. Gain- and loss-of-function experiments showed that Dusp6 is required for expression of a PPE gene, Six1, and patterning of adjacent regions, neural plate, and neural crest. To reveal the importance of Dusp6 in variable FGF production, we performed Dusp6 knockdown with FGF-bead implantation, which resulted in varying Six1 expression patterns. Taken together, these results suggest that Dusp6 is required for PPE formation and that it contributes to the robust patterning of PPE by mediating FGF signaling.

microRNA-211-5p predicts the progression of postmenopausal osteoporosis and attenuates osteogenesis by targeting dual specific phosphatase 6.

Postmenopausal osteoporosis (PMOP) is known as one of the prevalent diseases among middle-aged and elderly women. This paper revolves around the alteration of miR-211-5p in PMOP patients and its function in osteogenic differentiation. Quantitative real-time polymerase chain reaction (qRT-PCR) was implemented to check the miR-211-5p level in the plasma of PMOP patients. Knockdown and overexpression experiments were done to verify the influence of miR-211-5p on human-derived mesenchymal stem cell (hMSC) osteogenic differentiation and osteogenesis. The alkaline phosphatase (ALP) assay kit was taken to test ALP activity. Alizarin red staining monitored osteogenic differentiation, while oil red O staining examined adipogenesis. Western blot confirmed the profiles of osteoclastogenesis-concerned factors (TRAP, NFAT2, c-FOS, Runx2, OCN, CTSK), dual specific phosphatase 6 (DUSP6), ERK, SMAD, and ß-catenin. Dual-luciferase reporter and RNA immunoprecipitation assays were implemented to identify the association between miR-211-5p and DUSP6. Our data displayed that miR-211-5p was down-regulated in the PMOP patients' plasma (in contrast with the healthy controls), and it was positively correlated with Vit-D and BMD levels. miR-211-5p overexpression vigorously facilitated hMSC osteogenic differentiation, while miR-211-5p inhibition contributed to the opposite situation. miR-211-5p initiated the ERK/SMAD/ß-catenin pathway and repressed DUSP6's expression. Overexpression of DUSP6 counteracted the miR-211-5p-mediated function to a great extent and inactivated ERK/SMAD/ß-catenin, whereas enhancing ERK phosphorylation weakened the DUSP6 overexpression-induced function. Consequently, this research unveiled that miR-211-5p promotes osteogenic differentiation by interfering with the DUSP6-mediated ERK/SMAD/ß-catenin pathway.

DUSP4 Inactivation Leads to Reduced Extracellular Signal‒Regulated Kinase Activity through Upregulation of DUSP6 in Melanoma Cells.

A subset of dual-specificity phosphatases is a major negative regulator of MAPKs, and their involvement in tumorigenesis remains controversial. Among them, DUSP4 is reported to preferentially dephosphorylate extracellular signal‒regulated kinase (ERK) 1/2 and c-Jun N-terminal kinase over p38. In this study, we aimed to identify a possible role of DUSP4 in melanoma genesis. An examination of large-scale public data on gene expression and dependency revealed a considerably high DUSP4 expression and dependency of the melanoma cell lines compared with those of other tumor cell lines, which was not apparent for the other 24 dual-specificity phosphatases genes encoded in the human genome. Using two melanoma lines, we confirmed that DUSP4 depletion impaired cell growth without notably inducing apoptosis. Interestingly, immunoblotting and kinase translocation reporter data revealed that DUSP4 depletion induces a decrease in ERK1/2 phosphorylation but barely affects c-Jun N-terminal kinase phosphorylation, suggesting that neither ERK nor c-Jun N-terminal kinase is a direct target of DUSP4 in our experimental setting. Notably, DUSP4 depletion led to an increase in DUSP6 level, possibly through a post-transcriptional process, and DUSP6 knockout almost eliminated the DUSP4-depletion effect on cell growth and ERK activity. Our findings suggest that DUSP4 plays a role in maintaining a high ERK1/2 activity by negatively regulating DUSP6 and thus contributes to the survival and growth of melanoma cells.

CCN2-induced lymphangiogenesis is mediated by the integrin αvß5-ERK pathway and regulated by DUSP6.

Lymphangiogenesis is essential for the development of the lymphatic system and is important for physiological processes such as homeostasis, metabolism and immunity. Cellular communication network factor 2 (CCN2, also known as CTGF), is a modular and matricellular protein and a well-known angiogenic factor in physiological and pathological angiogenesis. However, its roles in lymphangiogenesis and intracellular signaling in lymphatic endothelial cells (LECs) remain unclear. Here, we investigated the effects of CCN2 on lymphangiogenesis. In in vivo Matrigel plug assays, exogenous CCN2 increased the number of Podoplanin-positive vessels. Subsequently, we found that CCN2 induced phosphorylation of ERK in primary cultured LECs, which was almost completely inhibited by the blockade of integrin αvß5 and partially decreased by the blockade of integrin αvß3. CCN2 promoted direct binding of ERK to dual-specific phosphatase 6 (DUSP6), which regulated the activation of excess ERK by dephosphorylating ERK. In vitro, CCN2 promoted tube formation in LECs, while suppression of Dusp6 further increased tube formation. In vivo, immunohistochemistry also detected ERK phosphorylation and DUSP6 expression in Podoplanin-positive cells on CCN2-supplemented Matrigel. These results indicated that CCN2 promotes lymphangiogenesis by enhancing integrin αvß5-mediated phosphorylation of ERK and demonstrated that DUSP6 is a negative regulator of excessive lymphangiogenesis by CCN2.