TRIM65 E3 ligase targets VCAM-1 degradation to limit LPS-induced lung inflammation

Although the adhesion molecules-mediated leukocyte adherence and infiltration into tissues is an important step of inflammation,the post-translational regulation of these proteins on the endothelial cells is poorly understood.Here,we report that TRIM65,an ubiquitin E3 iigase of tripartite protein family,selectively targets vascular cell adhesion molecule 1(VCAM-1)and promotes its ubiq-uitination and degradation,by which it critically controls the duration and magnitude of sepsis-induced pulmonary inflammation.TRIM65 is constitutively expressed in human vascular endothelial cells.During TNFa-induced endothelial activation,the protein levels ofTRIM65 and VCAM-1 are inversely correlated.Expression of wild-type TRIM65,but not expression of aTRIM65 mutant that lacks E3 ubiquitin ligase function in endothelial cells,promotes VCAM-1 ubiquitination and degradation,whereas small interference RNA-mediated knockdown of TRIM65 attenuates VCAM-1 protein degradation.Further experiments show that TRIM65 directly interacts with VCAM-1 protein and directs its polyubiquitination,by which TRIM65 controls monocyte adherence and infiltration into tissues during inflammation.Importantly,TRIM65-deficient mice are more sensitive to lipopolysaccharide-induced death,due to sustained and severe pulmonary inflammation.Taken together,our studies suggest that TRIM65-mediated degradation of VCAM-1 represents a potential mechanism that controls the duration and magnitude of infiammation.

TRIM14 promotes endothelial activation via activating NF-κB signaling pathway

Endothelial activation by proinflammatory cytokines is closely associated to the pathogenesis of atherosclerosis and other vascular diseases;however, the molecular mechanisms controlling endothelial activation are not fully understood. Here we identify TRIM14 as a new positive regulator of endothelial activation via activating NF-κB signal pathway. TRIM14 is highly expressed in human vascular endothelial cells (ECs) and markedly induced by inflammatory stimuli such as TNF-α, IL-1β, and LPS. Overexpression of TRIM14 significantly increased the expression of adhesion molecules such as VCAM-1, ICAM-1, E-selectin, and cytokines such as CCL2, IL-8, CXCL-1, and TNF-α in activated ECs and by which it facilitated monocyte adhesion to ECs. Conversely, knockdown of TRIM14 has opposite effect on endothelial activation. Upon TNF-α stimulation, TRIM14 is recruited to IKK complex via directly binding to NEMO and promotes the phosphorylation of IκBα and p65, which is dependent on its K63-linked ubiquitination. Meanwhile, p65 can directly bind to the promoter regions of human TRIM14 gene and control its mRNA transcription. Finally, TRIM14 protein level is significantly upregulated in mouse and human atheroma compared to normal arteries. Taken together, these results indicate that TRIM14-NF-κB forms a positive feedback loop to enhance EC activation and TRIM14 may be a potential therapeutic target for vascular inflammatory diseases such as atherosclerosis.

TRIM47 is a novel endothelial activation factor that aggravates lipopolysaccharide-induced acute lung injury in mice via K63-linked ubiquitination of TRAF2

Endothelial activation plays an essential role in the pathogenesis of sepsis-induced acute lung injury,however,the detailed regulatory mechanisms remain largely unknown.Here,we reported that TRIM47,an E3 ubiquitin ligase of the tripartite motifcontaining protein family,was highly expressed in vascular endothelial cells.TRIM47-deficient mice were effectively resistant to lipopolysaccharide(LPS)-induced acute lung injury and death by attenuating pulmonary inflammation.TRIM47 was upregulated during TNFα-induced endothelial activation in vitro.Knockdown of TRIM47 in endothelial cells inhibited the transcription of multiple pro-inflammatory cytokines,reduced monocyte adhesion and the expression of adhesion molecules,and suppressed the secretion of IL-1βand IL-6 in endothelial cells.By contrast,overexpression of TRIM47 promoted inflammatory response and monocyte adhesion upon TNFαstimulation.In addition,TRIM47 was able to activate the NF-κB and MAPK signaling pathways during endothelial activation.Furthermore,our experiments revealed that TRIM47 resulted in endothelial activation by promoting the K63-linked ubiquitination of TRAF2,a key component of the TNFαsignaling pathway.Taken together,our studies demonstrated that TRIM47 as a novel activator of endothelial cells,promoted LPS-induced pulmonary inflammation and acute lung injury through potentiating the K63-linked ubiquitination of TRAF2,which in turn activates NF-κB and MAPK signaling pathways to trigger an inflammatory response in endothelial cells.

Identification of Global DNA Methylation Signatures in Glioblastoma-Derived Cancer Stem Cells

Glioblastoma （GBM） is the most common and most aggressive primary brain tumor in adults. The existence of a small population of stem-like tumor cells that efficiently propagate tumors and resist cytotoxic therapy is one proposed mechanism leading to the resilient behavior of tumor cells and poor prognosis. In this study, we performed an in-depth analysis of the DNA methylation landscape in GBM- derived cancer stem ceils （GSCs）. Parallel comparisons of primary tumors and GSC lines derived from these tumors with normal controls （a neural stem cell （NSC） line and normal brain tissue） identified groups of hyper- and hypomethylated genes that display a trend of either increasing or decreasing methylation levels in the order of controls, primary GBMs, and their counterpart GSC lines, respectively. Interestingly, concurrent promoter hypermethylation and gene body hypomethylation were observed in a subset of genes including MGMT, AJAP1 and PTPRN2. These unique DNA methylation signatures were also found in primary GBM-derived xenograft tumors indicating that they are not tissue culture-related epigenetic changes. Integration of GSC-specific epigenetic signatures with gene expression analysis further identified candidate tumor suppressor genes that are frequently down-regulated in GBMs such as SPINT2, NEFM and PENK. Forced re-expression of SPINT2 reduced glioma cell proliferative capacity, anchorage independent growth, cell motility, and tumor sphere formation in vitro. The results from this study demonstrate that GSCs possess unique epigenetic signatures that may play important roles in the pathogenesis of GBM.

Mediator complex components are frequent targets for genetic alterations in various types of human cancer

The Mediator co-activator complex is a highly conserved,multisubunit protein complex required for gene transcription by RNA polymerase Ⅱ（RNAPⅡ）in all eukaryotes（Allen and Taatjes,2015）.This complex,which consists of at least 30 polypeptides,can be divided into four structurally distinct sub-modules including the head,middle,tail,and cyclin-dependent kinase 8（CDK8）modules （CKM） （Fig. 1A） （Yin and Wang, 2014; Allen and Taatjes, 2015）.