MAP3K2

Abstract: Proper tuning of β-catenin activity in osteoblasts is required for bone homeostasis, because both increased and decreased β-catenin activity have pathologic consequences. In the classical pathway for β-catenin activation, stimulation with WNT ligands suppresses constitutive phosphorylation of β-catenin by glycogen synthase kinase 3β, preventing β-catenin ubiquitination and proteasomal degradation. Here, we have found that mitogen-activated protein kinase kinase kinase 2 (MAP3K2 or MEKK2) mediates an alternative pathway for β-catenin activation in osteoblasts that is distinct from the canonical WNT pathway. FGF2 activates MEKK2 to phosphorylate β-catenin at serine 675, promoting recruitment of the deubiquitinating enzyme, ubiquitin-specific peptidase 15 (USP15). USP15 in turn prevents the basal turnover of β-catenin by inhibiting its ubiquitin-dependent proteasomal degradation, thereby enhancing WNT signaling. Analysis of MEKK2-deficient mice and genetic interaction studies between Mekk2- and β-catenin-null alleles confirm that this pathway is an important physiologic regulator of bone mass in vivo. Thus, an FGF2/MEKK2 pathway mediates an alternative nonclassical pathway for β-catenin activation, and this pathway is a key regulator of bone formation by osteoblasts.

Abstract: Growing evidence indicates that miR-520a was involved in the complement attack and migration of tumor cells, but nonetheless, the role of miR-520a-3p in non-small cell lung cancer (NSCLC) is not clear. Mitogen-activated protein kinase kinase kinase 2 (MAP3K2) is a kinase belonging to the serine/threonine protein kinase family. To develop potential therapy targeting MAP3K2, we studied the roles of miR-520a-3p in the proliferation, apoptosis and metastasis of NSCLC. The expression levels of miR-520a-3p were quantified in tumor tissues of NSCLC by qRT-PCR, and the mimics and inhibitors were used to verify the function of miR-520a-3p. The cell proliferation was evaluated by MTT assay, and the migration and invasion was evaluated by transwell assay. The athymic mice subcutaneous injection was used to research NSCLC cell tumor formation. The bioinformatics tools and luciferase assay was applied to detect the relationship between miR-520a-3p and its target. Protein levels of miR-520a-3p target was determined by western blot analysis. MiR-520a-3p expression was decreased in the NSCLC tissues compared with their normal counterparts and lower expression of miR-520a-3p in NSCLC tissues was associated with a higher clinical stage, NSCLC metastasis and poor prognosis. Inhibition of expression of miR-520a-3p can reduce in vitro NSCLC cell migration and invasion as well as in vivo metastasis. MAP3K2 mRNA contains a binding site for miR-520a-3p in the 3'UTR. MAP3K2 is one of target of miR-520a-3p. Together, our data demonstrated that miR-520a-3p inhibits proliferation, apoptosis and metastasis in NSCLC by targeting MAP3K2, and miR-520a-3p may be used as a prognosis marker for NSCLC in clinical research.

Abstract: Cumulative evidence suggests that microRNAs (miRNAs) promote gene expression in cancers. However, the pathophysiologic relevance of miRNA-mediated RNA activation in hepatocellular carcinoma (HCC) remains to be established. Our previous miRNA expression profiling in seven-paired HCC specimens revealed miR-93-5p as an HCC-related miRNA. In this study, miR-93-5p expression was assessed in HCC tissues and cell lines by quantitative real-time PCR and fluorescence in situ hybridization. The correlation of miR-93-5p expression with survival and clinicopathological features of HCC was determined by statistical analysis. The function and potential mechanism of miR-93-5p in HCC were further investigated by a series of gain- or loss-of-function experiments in vitro and in vivo. We identified that miR-93-5p, overexpressed in HCC specimens and cell lines, leads to poor outcomes in HCC cases and promotes proliferation, migration, and invasion in HCC cell lines. Mechanistically, rather than decreasing target mRNA levels as expected, miR-93-5p binds to the 3'-untranslated region (UTR) of mitogen-activated protein kinase kinase kinase 2 (MAP3K2) to directly upregulate its expression and downstream p38 and c-Jun N-terminal kinase (JNK) pathway, thereby leading to cell cycle progression in HCC. Notably, we also demonstrated that c-Jun, a downstream effector of the JNK pathway, enhances miR-93-5p transcription by targeting its promoter region. Besides, downregulation of miR-93-5p significantly retarded tumor growth, while overexpression of miR-93-5p accelerated tumor growth in the HCC xenograft mouse model. Altogether, we revealed a miR-93-5p/MAP3K2/c-Jun positive feedback loop to promote HCC progression in vivo and in vitro, representing an RNA-activating role of miR-93-5p in HCC development.