Identification and characterization of a novel gene EOLA1 stimulating ECV304 cell proliferation

Transcriptomics of angiotensin II-induced long noncoding and coding RNAs in endothelial cells

OBJECTIVE

Angiotensin II (Ang II)-induced endothelial dysfunction plays an important role in the pathogenesis of cardiovascular diseases such as systemic hypertension, cardiac hypertrophy and atherosclerosis. Recently, long noncoding RNAs (lncRNAs) have been shown to play an essential role in the pathobiology of cardiovascular diseases; however, the effect of Ang II on lncRNAs and coding RNAs expression in endothelial cells has not been evaluated. Accordingly, we sought to evaluate the expression profiles of lncRNAs and coding RNAs in endothelial cells following treatment with Ang II.

METHODS

Human umbilical vein endothelial cells (HUVECs) were cultured and treated with Ang II (10-6 mol/l) for 24 h. The cells were then profiled for the expression of lncRNAs and mRNAs using the Arraystar Human lncRNA Expression Microarray V3.0.

RESULTS

In HUVECs following Ang II treatment, from a total of 30 584 lncRNA targets screened, 25 targets were significantly upregulated, while 69 were downregulated. In the same HUVECs samples, from 26 106 mRNA targets screened, 28 targets were significantly upregulated and 67 were downregulated. Of the differentially expressed lncRNAs, RP11-354P11.2 and RP11-360F5.1 were the most upregulated (11-fold) and downregulated (three-fold) lncRNAs, respectively. Assigning the differentially regulated genes into functional groups using bioinformatics reveals numerous genes involved in the nucleotide excision repair and ECM-receptor interaction.

CONCLUSION

This is the first study to profile the Ang II-induced differentially expressed lncRNAs and mRNAs in human endothelial cells. Our results reveal novel targets and substantially extend the list of potential candidate genes involved in Ang II-induced endothelial dysfunction and cardiovascular diseases.

Crystal Structure of Human EOLA1 Implies Its Possibility of RNA Binding

Human endothelial-overexpressed lipopolysaccharide-associated factor 1 (EOLA1) has been suggested to regulate inflammatory responses in endothelial cells by controlling expression of proteins, interleukin-6 and vascular cell adhesion molecule-1, and by preventing apoptosis. To elucidate the structural basis of the EOLA1 function, we determined its crystal structure at 1.71 Å resolution and found that EOLA1 is structurally similar to an activating signal cointegrator-1 homology (ASCH) domain with a characteristic β-barrel fold surrounded by α-helices. Despite its low sequence identity with other ASCH domains, EOLA1 retains a conserved 'GxKxxExR' motif in its cavity structure. The cavity harbors aromatic and polar residues, which are speculated to accommodate nucleotide molecules as do YT521-B homology (YTH) proteins. Additionally, EOLA1 exhibits a positively charged cleft, similar to those observed in YTH proteins and the ASCH protein from Zymomonas mobilis that exerts ribonuclease activity. This implies that the positively charged cleft in EOLA1 could stabilize the binding of RNA molecules. Taken together, we suggest that EOLA1 controls protein expression through RNA binding to play protective roles against endothelial cell injuries resulting from lipopolysaccharide (LPS)-induced inflammation responses.

The Reduced Expression of EOLA1 May Be Related to Refractory Diabetic Foot Ulcer

BACKGROUND

Chronic diabetic foot ulcer (DFU) is one of the most intractable complications of diabetes mellitus (DM). Its pathogenesis is complex, and uncontrolled chronic inflammation is an important factor. Endothelial overexpressed lipopolysaccharide-associated factor 1 (EOLA1) discovered in our laboratory is an intracellular protein with the function of inflammatory regulation. This study was aimed at observing the expression of EOLA1 in DFU skin tissues and its relationship with inflammation and at exploring the possible role of EOLA1 in DFU and its mechanism.

METHODS

The patients with DFU were divided into 2 groups based on the formation time of ulcer: the acute wound (AW) group with the course of disease ≤ 4 weeks and the chronic wound (CW) group with the course of disease > 4 weeks. The relevant clinical data of patients were collected, and the skin tissues around the ulcer were used for immunofluorescence detection and immunohistochemical staining to observe inflammation. The expression levels of EOLA1, metallothionein 2A (MT2A), nuclear factor-κB (NF-κB), and interleukin-6 (IL-6) were detected by western blot.

RESULTS

A total of 79 patients were enrolled in the study. The results of immunofluorescence and immunohistochemistry showed that EOLA1 was expressed in the epithelial tissues of DFU. However, the expression of EOLA1 in the CW group was significantly lower than that in the AW group (P < 0.05), and the expression of NF-κB and IL-6 was obviously increased (P < 0.05).

CONCLUSION

The refractory wounds in patients with DFU may be closely related to the uncontrolled activation of inflammatory pathways in cells caused by the reduced expression of negative regulators of inflammation (e.g., EOLA1), and such decreased expression may be also strongly linked to the persistent state of inflammation.

EOLA1 Inhibits Lipopolysaccharide-Induced Vascular Cell Adhesion Molecule-1 Expression by Association with MT2A in ECV304 Cells

Our research group firstly discovered endothelial-overexpressed lipopolysaccharide-associated factor 1 (EOLA1, GenBank number AY074889) as a lipopolysaccharide (LPS) responsive gene in ECV304 cells. The previous studies have further demonstrated the association of EOLA1 with metallothionein 2A (MT2A), while the role of EOLA1 during LPS-induced inflammatory response in ECV304 cells is unknown. In this report, we determined the subcellular localization of EOLA1 and the regulatory capacity of EOLA1 on vascular cell adhesion molecule-1 (VCAM-1) in response to LPS in ECV304 cells. Our results show that EOLA1 is broadly diffuse in the cells, and EOLA1 expression is dramatically induced by LPS. EOLA1 knockdown results in significant enhancement of LPS-induced VCAM-1 production. Consistent with this, overexpression of EOLA1 leads to the reduction of LPS-induced VCAM-1 production. Furthermore, MT2A knockdown reduces LPS-induced VCAM-1 production. Collectively, our results demonstrate a negative regulatory role of EOLA1 on LPS-induced VCAM-1 expression involving its association with MT2A in ECV304 cells.

HMBOX1 interacts with MT2A to regulate autophagy and apoptosis in vascular endothelial cells

We previously found that Homeobox containing 1 (HMBOX1) was required for bone mesenchymal stem cell (BMSC) and mouse embryonic stem cell (ESC) differentiation into vascular endothelial cells (VECs). However, the function of HMBOX1 in VECs is still unknown. In this study, we found that HMBOX1 was abundantly expressed in the cytoplasm of human umbilical vascular endothelial cells (HUVECs). Knockdown of HMBOX1 induced apoptosis and inhibited autophagy. Overexpression of HMBOX1 inhibited apoptosis induced by fibroblast growth factor 2 deprivation and promoted autophagy. Metallothionein 2A (MT2A) was identified as an interaction protein with HMBOX1 by yeast two-hybrid assay, and confirmed by co-immunoprecipitation. Overexpression of HMBOX1 elevated intracellular free zinc level. Knockdown of MT2A inhibited this phenomenon. Moreover, N,N,N = ,N = -tetrakis (2-pyridylmethyl) ethylenediamine (TPEN), a zinc chelator, reversed the anti-apoptosis and pro-autophagy effects of HMBOX1. In conclusion, HMBOX1 regulated intracellular free zinc level by interacting with MT2A to inhibit apoptosis and promote autophagy in VECs.

EOLA1 protects lipopolysaccharide induced IL-6 production and apoptosis by regulation of MT2A in human umbilical vein endothelial cells

Endothelial cell (EC) injury or dysfunction is believed to be mediated at least in part by lipopolysaccharide (LPS). Recent studies have shown that LPS induces apoptosis in different types of endothelium, including HUVEC. Previously we used EOLA1 (endothelial-overexpressed LPS-associated factor 1) cDNA as a bait and performed a yeast two-hybrid screening of a human liver cDNA library and identified metallothionein 2a (MT2a) as the associated protein. EOLA1 protein plays a role as a signal transduction factor. But the mechanism of EOLA1 mediated the protection of cell production of IL-6 and apopotosis in HUVEC is not known. MT2a is expressed in many kinds of cells and plays a role in inflammation. In this study, we demonstrated that LPS could induce EOLA1 expression in time-dependent and apparently contributed to the inhibition of IL-6 production and apoptosis induced by LPS treatment. We also found that deletion of EOLA1 promoted IL-6 production and apoptosis in the treatment of LPS in HUVEC. Furthermore, we demonstrated that MT2a was activated by LPS, and played a key role in LPS-induced IL-6 expression in HUVEC. We further provided the evidence that EOLA1 functioned as a negative regulator for LPS response by regulation of MT2a. These findings suggest that EOLA1 may have an important regulatory role during EC inflammatory responses.

The significance of differential expression of genes and proteins in human primary cells caused by microgrooved biomaterial substrata

We demonstrate that etched microgrooves, with truncated V-shape in cross-section and subsequent acid etching, on titanium substrata alter the expression of various genes and proteins in human primary cells. Etched microgrooves with 30 or 60 μm width and 10 μm depth promoted human gingival fibroblast proliferation and significantly enhanced the osteoblast differentiation of human bone marrow-derived mesenchymal stem cells and human periodontal ligament cells by inducing differential expression of various genes involved in cell adhesion, migration, proliferation, mitosis, cytoskeletal reorganization, translation initiation, vesicular trafficking, proton transportation, transforming growth factor-β signaling, mitogen-activated protein kinase signaling, simvastatin's anabolic effect on bone, inhibitory guanine nucleotide binding protein (G protein)'s action, sumoylation pathway, survival/apoptosis, mitochondrial distribution, type I collagen production, osteoblast differentiation, and bone remodeling that were verified by the differential display PCR and quantitative real-time PCR. The most influential genes on the enhancement of fibroblast proliferation or osteoblast differentiation were determined by multiple regression analysis, and the expression of relevant proteins was confirmed by western blotting and protein quantitation.

A potential transcriptional regulator is out-of-frame translated from the metallothionein 2A messenger RNA

In a number of yeast two-hybrid screens, we have found clones that contained parts of the human metallothionein 2A (MT2A) nucleotide sequence. All of these clones were out-of-frame relative to the MT2A coding sequence and activated the yeast reporters in the presence of the Gal4 DNA binding domain but irrespective of the bait protein. Reporter gene activation was abolished when activation domain and MT2A coding sequences were brought in-frame. In light of these findings, we evaluated all recently reported interactions with metallothioneins because our out-of-frame proline-rich protein might have been the actual interaction partner in some of these studies.

Changes in the expression of endothelial-overexpressed lipopolysaccharide-associated factor 1 in grafts during acute rejection following liver transplantation in rats

This study investigated changes in expression of endothelial-overexpressed lipopolysaccharide-associated factor 1 (EOLA1) in grafts following liver transplantation in rats. Thirty Lewis rats received liver transplants from Lewis rats (tolerance group); 30 received liver transplants from dark Agouti rats (acute rejection group). Changes in serum biochemical indexes (alanine aminotransferase and total bilirubin), graft histology and EOLA1 expression were measured on days 1, 3, 5, 7 and 10 post-operatively. Mean survival time was >100 days in the tolerance group and 16.2 +/- 1.4 days in the acute rejection group. Pathological evidence of acute rejection in grafts was seen after day 5 in the acute rejection group. Serum biochemical indexes were significantly higher in the acute rejection group than in the tolerance group from day 5 post-operatively, whereas EOLA1 expression in the liver graft was significantly higher in the tolerance group than in the acute rejection group. EOLA1 expression seems to be negatively correlated with severity of rejection after liver transplantation.

ECSM2, an endothelial specific filamin a binding protein that mediates chemotaxis

OBJECTIVE

We aimed to characterize the expression and function of a novel transcript that bioinformatics analysis predicted to be endothelial specific, called endothelial-specific molecule-2 (ECSM2).

METHODS AND RESULTS

A full-length cDNA was isolated and predicted ECSM2 to be a putative 205-amino acid transmembrane protein that bears no homology to any known protein. Quantitative polymerase chain reaction analysis in vitro and in situ hybridization analysis in vivo confirmed ECSM2 expression to be exclusively endothelial, and localization to the plasma membrane was shown. Knockdown of ECSM2 expression in human umbilical vein endothelial cells using siRNA resulted in both reduced chemotaxis and impaired tube formation on matrigel, a solubilized basement membrane, both processes involved in angiogenesis. A yeast 2 hybrid analysis using the ECSM2 intracellular domain identified filamin A as an interacting protein. This interaction was confirmed by precipitation of filamin-A from endothelial cell lysates by a GST-tagged intracellular domain of ECSM2.

CONCLUSIONS

This study is the first to characterize a novel cell surface protein ECSM2 that regulates endothelial chemotaxis and tube formation, and interacts with filamin A. These studies implicate a role for ECSM2 in angiogenesis via modulation of the actin cytoskeleton.

Production of the polyclonal anti-human metallothionein 2A antibody with recombinant protein technology

Metallothionein 2A (MT2A) is a small stress response protein that can be induced by exposure to toxic metals. It is highly expressed in breast cancer cells. In this study, the cDNA encoding the human MT2A protein was expressed as glutathione S-transferase (GST) fusion protein in Escherichia coli. Recombinant MT2A proteins were loaded onto 12% sodium dodecylsulfate-polyacrylamide gel and separated by electrophoresis, the recombinant protein was visualized by Coomassie blue staining and the 33 kDa recombinant GST-MT2A fusion protein band was cut out from the gel. The gel slice was minced and used to generate polyclonal antisera. Immunization of rabbit against MT2A protein allowed the production of high titer polyclonal antiserum. This new polyclonal antibody recognized recombinant MT2A protein in western blot analysis. This low-cost antibody will be useful for detection in various immuno-assays.