Protein phosphorylation plays critical roles in many regulatory mechanisms controlling cell activities and thus involved in various diseases. The cellular equilibrium of phosphorylation is regulated through the actions of protein kinases and phosphatases. Therefore, these regulatory proteins have emerged as promising targets for drug development. In this study, we screened protein tyrosine phosphatases (PTPs) by in vitro phosphatase assays to identify PTPs that are inhibited by 8-hydroxy-7-(6-sulfonaphthalen-2-yl)diazenyl-quinoline-5-sulfonic acid (NSC-87877), a potent inhibitor of SHP-1 and SHP-2 PTPs. Phosphatase activity of dual-specificity protein phosphatase 26 (DUSP26) was decreased by the inhibitor in a dose-dependent manner. Kinetic studies with NSC-87877 and DUSP26 revealed a competitive inhibition. NSC-87877 effectively inhibited DUSP26-mediated dephosphorylation of p38, a member of mitogen-activated protein kinase (MAPK) family. Since DUSP26 is involved in survival of anaplastic thyroid cancer (ATC) cells, NSC-87877 could be a therapeutic reagent for treating ATC.

Nonalcoholic fatty liver disease (NAFLD) is featured by hepatic steatosis, insulin resistance, lipid deposition and inflammation. However, the pathogenic mechanism of NAFLD is still poorly understood. Dual-specificity phosphatase 16 (DUSP16), a c-Jun N-terminal kinase-specific phosphatase, has been reported to negatively modulate the mitogen-activated protein kinases (MAPKs) signaling, and it has never been investigated in NAFLD progression. In the study, we identified that DUSP16 could directly interact with TAK1 in human hepatocytes. DUSP16 knockdown in the isolated primary hepatocytes stimulated by palmitate (PA) showed accelerated lipid deposition and inflammatory response, along with the exacerbated activation of c-Jun NH2-terminal kinase (JNK), Transforming growth factor β (TGF-β)-activated kinase (TAK1) and nuclear factor-κB (NF-κB) signaling pathways; however, the opposite results were detected in PA-treated hepatocytes with DUSP16 over-expression. The in vivo experiments confirmed that DUSP16 knockout significantly aggravated the metabolic disorder and insulin resistance in high fat diet (HFD)-challenged mice. In addition, HFD-provoked hepatic lipid accumulation and inflammation were further promoted in mice with DUSP16 knockout through the same molecular mechanism as detected in vitro. Herein, these findings demonstrated that DUSP16 could directly interact with TAK1 and negatively regulate JNK signaling to alleviate metabolic stress-induced hepatic steatosis, and thus could be considered as a promising new molecular target for NAFLD treatment.

Osteoporosis is a progressive systematic skeletal disorder featured by decreased bone and enhanced risk of fracture due to an uncoupling of bone resorption. Chronic inflammatory response plays an essential role in osteoporosis progression. Unfortunately, the pathogenesis that contributes to osteoporosis still remains unclear. Dual-specificity phosphatase 14 (Dusp14, also known as MKP6) is a MAP kinase phosphatase, and has important roles in regulating various cellular processes. In the study, we attempted to explore the effects of Dusp14 on osteoporosis development. The results indicated that Dusp14 expression was decreased during osteoclast differentiation and that Dusp14 over-expression markedly alleviated osteoclast generation regulated by macrophage colony-stimulating factor (M-CSF) and receptor activator of NF-κB ligand (RANKL). In M-CSF/RANKL-treated bone marrow-derived cells (BMMs), promoting Dusp14 expression significantly alleviated inflammation and apoptosis by suppressing nuclear factor (NF)-κB and Caspase-3 signaling pathways, respectively. Furthermore, AMP-activated protein kinase (AMPK)-α activation was markedly increased by Dusp14 over-expression in M-CSF/RANKL-incubated BMMs. Importantly, we found that AMPKα blockage obviously abolished the role of Dusp14 in preventing osteoclasts differentiation at least partly via elevating M-CSF/RANKL-elicited inflammation and apoptosis. In vivo, magnesium silicate-induced inflammatory osteoporosis was obviously alleviated in Dusp14 transgenic (TG) mice. Taken together, we defined Dusp14 as an important molecular switch resulting in osteoporosis through an AMPKα-dependent manner.

Parkinson's disease (PD) is the second most common neurodegenerative disorder, characterized by dopaminergic neuron loss, inflammation and oxidative stress injury in the substantia nigra pars compacta (SNpc). Tripartite motif 10 (TRIM10) belongs to the TRIM family of proteins and has been implicated to play a role in in PD, although supporting evidence has yet to be established. 1-methyl-4-phenylpyridinium (MPP+), the metabolite of MPTP (Mitochondrial parkinsonian neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetra-hydropyridine), is often used to generate a cellular model of PD. In this study, we found that MPP + inhibited cell proliferation and induced TRIM10 expression. Knockdown of TRIM10 alleviated cell apoptosis and ROS generation induced by MPP+. Further, MPP + decreased the expression of dual specificity phosphatase 6 (DUSP6) and this effect was reversed by TRIM10 knockdown. Moreover, DUSP6 alleviated cell apoptosis and ROS generation induced by TRIM10. Of note, TRIM10 suppressed DUSP6 by promoting DUSP6 ubiquitination. In conclusion, silencing of TRIM10 reduced cell apoptosis and ROS levels in a cellular model of PD, suggesting a potential role of TRIM10 in PD treatment.

Previous studies have demonstrated that microRNAs (miRNAs) play important roles in the pathogenesis of neuropathic pain. In the present study, we found that miR-32-5p was significantly upregulated in rats after spinal nerve ligation (SNL), specifically in the spinal microglia of rats with SNL. Functional assays showed that knockdown of miR-32-5p greatly suppressed mechanical allodynia and heat hyperalgesia, and decreased inflammatory cytokine (IL-1β, TNF-α and IL-6) protein expression in rats after SNL. Similarly, miR-32-5p knockdown alleviated cytokine production in lipopolysaccharide (LPS)-treated spinal microglial cells, whereas its overexpression had the opposite effect. Mechanistic investigations revealed Dual-specificity phosphatase 5 (Dusp5) as a direct target of miR-32-5p, which is involved in the miR-32-5p-mediated effects on neuropathic pain and neuroinflammation. We demonstrated for the first time that miR-32-5p promotes neuroinflammation and neuropathic pain development through regulation of Dusp5. Our findings highlight a novel contribution of miR-32-5p to the process of neuropathic pain, and suggest possibilities for the development of novel therapeutic options for neuropathic pain.

Tripartite motif-containing protein 7 (TRIM7), which is involved in the biosynthesis of glycogen, has been reported to drive lung tumorigenesis. In the present study, we aimed to examine the expression, roles and underlying molecular mechanisms of TRIM7 in hepatocellular carcinoma (HCC) development. Real-time PCR and immunohistochemical staining were performed to test the expression of TRIM7 in HCC tissues. Cell proliferation, cell cycle and tumorigenicity experiments were conducted to determine the function of TRIM7. The results showed that TRIM7 expression was elevated in human HCC tissues and that TRIM7 expression was significantly associated with tumor size, pTNM stage, serum α-fetoprotein (AFP) concentration, serum hepatitis B virus (HBV) DNA copy number and overall survival (OS) of HCC patients. TRIM7 knockdown inhibited the proliferation of HCC cells in vitro and in vivo. TRIM7 knockdown also induced a G1/S checkpoint in HCC cell lines. Additionally, TRIM7 knockdown led to decreased phosphorylated p38 (p-p38) and increased expression of p53 and p21. Ectopic expression of TRIM7 promoted HCC cell proliferation, cell cycle progression and p38 activation, but not in the presence of the p38 inhibitor SB203580. Moreover, TRIM7 overexpression enhanced the polyubiquitination and degradation of dual specificity phosphatase 6 (DUSP6). DUSP6 overexpression abolished the promotional effect of TRIM7 overexpression on HCC cell proliferation and the activation of p38. Furthermore, HBV X protein (HBx), a protein coded by HBV, was demonstrated to upregulate TRIM7 expression. Collectively, TRIM7 overexpression may contribute to the highly proliferative characteristics of HCC cells, and targeting TRIM7 might be a potential strategy for HCC treatment.