CSE1L promotes nuclear accumulation of transcriptional coactivator TAZ and enhances invasiveness of human cancer cells.

The transcriptional coactivator with PDZ-binding motif (TAZ) (WWTR1) induces epithelial-mesenchymal transition and enhances drug resistance in multiple cancers. TAZ has been shown to interact with transcription factors in the nucleus, but when phosphorylated, translocates to the cytoplasm and is degraded through proteasomes. Here, we identified a compound TAZ inhibitor 4 (TI-4) that shifted TAZ localization to the cytoplasm independently of its phosphorylation. We used affinity beads to ascertain a putative target of TI-4, chromosomal segregation 1 like (CSE1L), which is known to be involved in the recycling of importin α and as a biomarker of cancer malignancy. We found that TI-4 suppressed TAZ-mediated transcription in a CSE1L-dependent manner. CSE1L overexpression increased nuclear levels of TAZ, whereas CSE1L silencing delayed its nuclear import. We also found via the in vitro coimmunoprecipitation experiments that TI-4 strengthened the interaction between CSE1L and importin α5 and blocked the binding of importin α5 to TAZ. WWTR1 silencing attenuated CSE1L-promoted colony formation, motility, and invasiveness of human lung cancer and glioblastoma cells. Conversely, CSE1L silencing blocked TAZ-promoted colony formation, motility, and invasiveness in human lung cancer and glioblastoma cells. In human cancer tissues, the expression level of CSE1L was found to correlate with nuclear levels of TAZ. These findings support that CSE1L promotes the nuclear accumulation of TAZ and enhances malignancy in cancer cells.

Short DNA/RNA heteroduplex oligonucleotide interacting proteins are key regulators of target gene silencing.

Antisense oligonucleotide (ASO)-based therapy is one of the next-generation therapy, especially targeting neurological disorders. Many cases of ASO-dependent gene expression suppression have been reported. Recently, we developed a tocopherol conjugated DNA/RNA heteroduplex oligonucleotide (Toc-HDO) as a new type of drug. Toc-HDO is more potent, stable, and efficiently taken up by the target tissues compared to the parental ASO. However, the detailed mechanisms of Toc-HDO, including its binding proteins, are unknown. Here, we developed native gel shift assays with fluorescence-labeled nucleic acids samples extracted from mice livers. These assays revealed two Toc-HDO binding proteins, annexin A5 (ANXA5) and carbonic anhydrase 8 (CA8). Later, we identified two more proteins, apurinic/apyrimidinic endodeoxyribonuclease 1 (APEX1) and flap structure-specific endonuclease 1 (FEN1) by data mining. shRNA knockdown studies demonstrated that all four proteins regulated Toc-HDO activity in Hepa1-6, mouse hepatocellular cells. In vitro binding assays and fluorescence polarization assays with purified recombinant proteins characterized the identified proteins and pull-down assays with cell lysates demonstrated the protein binding to the Toc-HDO and ASO in a biological environment. Taken together, our findings provide a brand new molecular biological insight as well as future directions for HDO-based disease therapy.

Epigenetic modulation of Fgf21 in the perinatal mouse liver ameliorates diet-induced obesity in adulthood.

The nutritional environment to which animals are exposed in early life can lead to epigenetic changes in the genome that influence the risk of obesity in later life. Here, we demonstrate that the fibroblast growth factor-21 gene (Fgf21) is subject to peroxisome proliferator-activated receptor (PPAR) α-dependent DNA demethylation in the liver during the postnatal period. Reductions in Fgf21 methylation can be enhanced via pharmacologic activation of PPARα during the suckling period. We also reveal that the DNA methylation status of Fgf21, once established in early life, is relatively stable and persists into adulthood. Reduced DNA methylation is associated with enhanced induction of hepatic FGF21 expression after PPARα activation, which may partly explain the attenuation of diet-induced obesity in adulthood. We propose that Fgf21 methylation represents a form of epigenetic memory that persists into adulthood, and it may have a role in the developmental programming of obesity.

Multiple target autoantigens on endothelial cells identified in juvenile dermatomyositis using proteomics.

Objective: Although generally classified within the group of inflammatory myopathies, JDM displays many pathological features of vasculitis. Previous work has shown that AECA are abundant in other forms of vasculitis. We therefore investigated whether such antibodies might also be detected in JDM. Methods: We screened plasma from children with JDM for the presence of AECA by western blotting and 2D gel electrophoresis (2DE) using proteins extracted from human aortic endothelial cells as the substrate. We performed mass spectrometry to identify candidate antigens from 2DE gels and used ELISA to confirm the presence of specific antibodies. Results: We identified 22 candidate target autoantigens for AECA probed with JDM plasma. Interestingly, 17 of these 22 target antigens were proteins associated with antigen processing and protein trafficking. ELISA confirmed the presence of antibodies to heat shock cognate 71 kDa protein in JDM plasma, particularly in children with active, untreated disease. Conclusion: Children with JDM express antibodies to autoantigens in endothelial cells. The clinical and pathological significance of such autoantibodies require further investigation.

A novel immunotoxin reveals a new role for CD321 in endothelial cells.

There are currently several antibody therapies that directly target tumors, and antibody-drug conjugates represent a novel moiety as next generation therapeutics. Here, we used a unique screening probe, DT3C, to identify functional antibodies that recognized surface molecules and functional epitopes, and which provided toxin delivery capability. Accordingly, we generated the 90G4 antibody, which induced DT3C-dependent cytotoxicity in endothelial cells. Molecular analysis revealed that 90G4 recognized CD321, a protein localized at tight junctions. Although CD321 plays a pivotal role in inflammation and lymphocyte trans-endothelial migration, little is known about its mechanism of action in endothelial cells. Targeting of CD321 by the 90G4 immunotoxin induced cell death. Moreover, 90G4 immunotoxin caused cytotoxicity primarily in migratory endothelial cells, but not in those forming sheets, suggesting a critical role for CD321 in tumor angiogenesis. We also found that hypoxia triggered redistribution of CD321 to a punctate localization on the basal side of cells, resulting in functional impairment of tight junctions and increased motility. Thus, our findings raise the intriguing possibility that endothelial CD321 presented cellular localization in tight junction as well as multifunctional dynamics in several conditions, leading to illuminate the importance of widely-expressed CD321 as a potential target for antitumor therapy.

The mevalonate pathway regulates primitive streak formation via protein farnesylation.

The primitive streak in peri-implantation embryos forms the mesoderm and endoderm and controls cell differentiation. The metabolic cues regulating primitive streak formation remain largely unknown. Here we utilised a mouse embryonic stem (ES) cell differentiation system and a library of well-characterised drugs to identify these metabolic factors. We found that statins, which inhibit the mevalonate metabolic pathway, suppressed primitive streak formation in vitro and in vivo. Using metabolomics and pharmacologic approaches we identified the downstream signalling pathway of mevalonate and revealed that primitive streak formation requires protein farnesylation but not cholesterol synthesis. A tagging-via-substrate approach revealed that nuclear lamin B1 and small G proteins were farnesylated in embryoid bodies and important for primitive streak gene expression. In conclusion, protein farnesylation driven by the mevalonate pathway is a metabolic cue essential for primitive streak formation.

Hematopoiesis-dependent expression of CD44 in murine hepatic progenitor cells.

The fetal liver serves as the predominant hematopoietic organ until birth. However, the mechanisms underlying this link between hematopoiesis and hepatogenesis are unclear. Previously, we reported the isolation of a monoclonal antibody (anti-Liv8) that specifically recognizes an antigen (Liv8) present in murine fetal livers at embryonic day 11.5 (E11.5). Liv8 is a cell surface molecule expressed by hematopoietic cells in both fetal liver and adult mouse bone marrow. Here, we report that Liv8 is also transiently expressed by hepatoblasts at E11.5. Using protein purification and mass spectrometry, we have identified Liv8 as the CD44 protein. Interestingly, the expression of Liv8/CD44 in fetal liver was completely lost in AML1(-/-) murine embryos, which lack definitive hematopoiesis. These results show that hepatoblasts change from Liv8/CD44-negative to Liv8/CD44-positive status in a hematopoiesis-dependent manner by E11.5, and indicate that Liv8/CD44 expression is an important link between hematopoiesis and hepatogenesis during fetal liver development.

Expression of transcriptional repressor ATF3/LRF1 in human atherosclerosis: colocalization and possible involvement in cell death of vascular endothelial cells.

Vascular endothelial cell death contributes to the progression of atherosclerotic lesion, and several transcriptional regulators are involved in the process. Activating transcription factor 3/liver regenerating factor-1 (ATF3/LRF-1), a stress-inducible transcriptional repressor, was shown to be highly expressed in vascular endothelial cells and macrophages of human atherosclerotic lesions by immunohistological assay. The expression was colocalized in these cells which were positive for TdT-mediated dUTP nick-end labeling (TUNEL) and annexin V. Treatment of human umbilical vein endothelial cells (HUVECs) by tumor necrosis factor (TNF)-alpha, oxidized low density lipoprotein (oxLDL), and lysophosphatidylcholine (LPC) rapidly induced ATF3/LRF-1, which showed an increased DNA binding to the consensus ATF/CRE sequence by supershift of gel shift assay. Flow cytometry analysis and immunostaining analysis with TUNEL assay showed that ATF3/LRF-1 was highly expressed in cell death induced by these agents. Moreover, antisense ATF3/LRF-1 cDNA partly suppressed the cell death induced by TNF-alpha, oxLDL, and LPC. From these results, it is indicated that ATF3/LRF-1 is one of the immediate early response genes in vascular endothelial cells in response to atherogenic stimuli, and may play a role in the endothelial cell death associated with atherogenesis.