Extracellular signal-regulated kinase 8 (ERK8), also known as mitogen-activated protein kinase 15 (MAPK15), is the most recently identified protein kinase of the ERK family members and yet the least has been studied so far. Here, we report that ERK8 is highly expressed in several human lung cancer cell lines and is positively correlated with their sensitivities to the anti-cancer drug arsenic trioxide (As2O3). As2O3 at physiologically relevant concentrations (5–20 μM) potently stimulates the phosphorylation of ERK8 at Thr175 and Tyr177 within the TEY motif in the kinase domain, leading to its activation. Interestingly, activated ERK8 interacts and directly phosphorylates IkappaBalpha (IκBα) at Ser32 and Ser36, resulting in IκBα degradation. This in turn promotes nuclear factor-kappaB (NF-κB) p65 nuclear translocation and chromatin-binding, as well as the subsequent induction and activation of proteins involved in apoptosis. We also show that stable short-hairpin RNA-specific knockdown of endogenous ERK8 or inhibition of NF-κB activity by NF-κB inhibitor in high ERK8 expressing lung cancer H1299 cells blunted the As2O3-induced NF-κB activation and cytotoxicity towards these cells, indicating the critical role of ERK8 and NF-κB in mediating the As2O3 effects. Taken together, our findings suggest for the first time a regulatory paradigm of NF-κB activation by ERK8 upon As2O3 treatment in human lung cancer cells; and implicate a potential therapeutic advantage of As2O3 that might gain more selective killing of cancer cells with high ERK8 expression.

Background Circular RNAs (circRNAs) have been considered as pivotal biomarkers in Diabetic nephropathy (DN). CircRNA ARP2 actin-related protein 2 homolog (circ-ACTR2) could promote the HG-induced cell injury in DN. However, how circ-ACTR2 acts in DN is still unclear. This study aimed to explore the molecular mechanism of circ-ACTR2 in DN progression, intending to provide support for the diagnostic and therapeutic potentials of circ-ACTR2 in DN. Methods RNA expression analysis was conducted by the quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Cell growth was measured via Cell Counting Kit-8 and EdU assays. Inflammatory response was assessed by Enzyme-linked immunosorbent assay. The protein detection was performed via western blot. Oxidative stress was evaluated by the commercial kits. The molecular interaction was affirmed through dual-luciferase reporter and RNA immunoprecipitation assays. Results Circ-ACTR2 level was upregulated in DN samples and high glucose (HG)-treated human renal mesangial cells (HRMCs). Silencing the circ-ACTR2 expression partly abolished the HG-induced cell proliferation, inflammation and extracellular matrix accumulation and oxidative stress in HRMCs. Circ-ACTR2 was confirmed as a sponge for miR-205-5p. Circ-ACTR2 regulated the effects of HG on HRMCs by targeting miR-205-5p. MiR-205-5p directly targeted high-mobility group AT-hook 2 (HMGA2), and HMGA2 downregulation also protected against cell injury in HG-treated HRMCs. HG-mediated cell dysfunction was repressed by miR-205-5p/HMGA2 axis. Moreover, circ-ACTR2 increased the expression of HMGA2 through the sponge effect on miR-205-5p in HG-treated HRMCs. Conclusion All data have manifested that circ-ACTR2 contributed to the HG-induced DN progression in HRMCs by the mediation of miR-205-5p/HMGA2 axis.

Extracellular signal-regulated kinase 8 (ERK8), proposed as a novel potential therapeutic target for cancer, has been implicated in cell transformation, apoptosis, the protection of genomic integrity, and autophagy. To facilitate ERK8 research, a highly specific anti-ERK8 antibody is needed. In this article, we use the Immune Epitope Database and Analysis Resource online tool to predict B-cell epitopes of human ERK8 protein, and choose a 28 aa-peptide sequence to generate the GST-ERK8(28aa) fusion protein as the antigen for developing polyclonal antibody against ERK8. The specificity and sensitivity of anti-ERK8 antibody were robustly validated by immunoblotting, immunocytochemical and immunohistochemical analyses; and we found that both the endogenous and ectopically-expressed human ERK8 proteins can be recognized by our anti-ERK8 antibody. This suggested that our characterized anti-ERK8 antibody will be a valuable tool for the elucidation of the distribution of ERK8 at cellular and histological levels. Finally, our tissue array analysis also demonstrated that the ERK8 protein was localized in both the nucleus and cytoplasm of human lung cancers.

We attempted to analyze the clinical value of microRNA (miR)-590-3p in diabetic nephropathy (DN) patients and its role in high glucose (HG)-induced renal tubular epithelial cell (HK-2) injury. Serum levels of miR-590-3p were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Spearman correlation coefficient analysis of the correlation between miR-590-3p and clinical indicators. The diagnostic value of miR-590-3p was analyzed by the receiver operating characteristic (ROC) curve. Then, the DN cell model induced by HG in HK-2 cells was established. Enzyme-linked immunosorbent assay (ELISA), flow cytometry, and CCK-8 assay were employed to assess cell inflammation, oxidative stress, apoptosis, and proliferation. Dual-luciferase reporter assay confirmed the target of miR-590-3p. Serum miR-590-3p was reduced in patients of DN, which was positively correlated with eGFR and negatively associated with albuminuria. Furthermore, miR-590-3p also can diagnose patients of DN from healthy subjects or patients of T2DM. Furthermore, miR-590-3p was decreased in a concentration- and time-dependent manner during HG-induction. miR-590-3p overexpression bated HG-induced inhibition effect on cell proliferation and promotion effects on apoptosis, oxidative stress, and inflammation. C-X3-C motif chemokine ligand1 (CX3CL1) is the target of miR-590-3p, whose levels were enhanced in DN patients and are negatively regulated by miR-590-3p. Our discoveries offered new insights that reduced miR-590-3p as a potential biomarker for the diagnosis of DN, and elevated miR-590-3p can alleviate renal tubular injury by HG-induced through targeting CX3XL1, which may be a novel target for improving the development of DN.

No abstract