E3 ubiquitin ligases STUB1/CHIP contributes to the Th17/Treg imbalance via the ubiquitination of aryl hydrocarbon receptor in rheumatoid arthritis

STIP1-homologous U-Box containing protein 1 (STUB1) is involved in the development of immune pathologies and the regulation of T cell. However, the potential role of STUB1 in the pathogenesis of rheumatoid arthritis (RA), especially in the regulation of T cells, remains elusive. Here we show that STUB1 promotes the imbalance of Th17/Treg cells through non-degradative ubiquitination of aryl hydrocarbon receptor (AHR). Using Western blot and flow cytometry analysis, we observe that the level of STUB1 was increased in RA patients compared with healthy controls. In particular, the expression of STUB1 protein was different in Th17 cells and Treg cells of RA patients. We also demonstrated that STUB1 facilitates Th17/Treg imbalance by up- or downregulating the expression of STUB1. In a subsequent series of in vitro experiments, we revealed that STUB1 promoted the imbalance of Th17 and Treg cells through non-degradative ubiquitination of AHR. Both knockdown of the AHR expression by siRNA and assays of CYP1A1 enzymatic activity by ethoxyresorufin-O-deethylase (EROD) supported this conclusion. Furthermore, we explored the ubiquitination sites of AHR responsible for STUB1-mediated ubiquitination and revealed that STUB1 promotes ubiquitination of AHR via K63 chains. Together, STUB1 may induce the imbalance of Th17/Treg cells via ubiquitination of AHR and serve as a potential therapeutic target for RA.     

Sublytic C5b-9 complexes induce proliferative changes of glomerular mesangial cells in rat Thy-1 nephritis through TRAF6-mediated PI3K-dependent Akt1 activation

The proliferation of glomerular mesangial cells (GMCs) and secretion of extracellular matrix (ECM) in rat Thy-1 nephritis (Thy-1N), resembling human mesangioproliferative glomerulonephritis (MsPGN), have been studied for many years, but the mechanisms, especially the role of signalling pathway activation and its regulation in GMCs triggered by sublytic C5b-9 complexes in Thy-1N rats remain largely unclear. In the study, the proliferation of GMCs and production of ECM as well as the role of PI3K/Akt and its regulation, both in GMCs induced by sublytic C5b-9 (in vitro) and in the renal tissues of rats with Thy-1N (in vivo), were determined and the results revealed that GMCs proliferation and ECM secretion, both in vitro and in vivo, were notably increased, and that PI3K/Akt1 activation and its regulation, such as TNF receptor-associated factor 6 (TRAF6)-mediated Akt1 ubiquitination and PI3K-dependent Akt1 phosphorylation, were involved in the process of Thy-1N induction. On the other hand, silence of the TRAF6, PI3K or Akt1 genes could obviously diminish the proliferative damages and urinary protein secretion of Thy-1N rats. Together, these data implicated that sublytic C5b-9 complexes in Thy-1N rats could promote GMCs proliferation and ECM production through TRAF6-mediated PI3K-dependent Akt1 activation, in which the ubiquitination and phosphorylation of the Akt1 signal molecule played an important role in the initiation and development of the proliferative changes in the rats with Thy-1N.     

A novel missense mutation of the CYLD gene identified in a Hungarian family with Brooke–Spiegler syndrome

Brooke–Spiegler syndrome (BSS; OMIM 605041) is an autosomal dominant disease characterized by skin appendage tumors due to mutations in the cylindromatosis gene (CYLD). We investigated a Hungarian BSS pedigree with two affected members, father and daughter. Direct sequencing demonstrated a novel missense mutation (c.2613C>G; p.His871Gln) in exon 19 within the ubiquitin‐specific protease domain of the encoded protein. We performed preliminary analysis to reveal the functional role of this novel mutation. Our data suggest that this novel CYLD mutation leads to increased ubiquitination of NEMO through influencing deubiquitinating activity of the CYLD protein and thus may result in enhanced NF‐κB signalling.     

Sense-Antisense lncRNA Pair Encoded by Locus 6p22.3 Determines Neuroblastoma Susceptibility via the USP36-CHD7-SOX9 Regulatory Axis

1. Download high-res image (388KB)
2. Download full-size image

     

ARL4C stabilized by AKT/mTOR pathway promotes the invasion of PTEN-deficient primary human glioblastoma

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) deficiency in primary human glioblastoma (GBM) is associated with increased invasiveness and poor prognosis with unknown mechanisms. Therefore, how loss of PTEN promotes GBM progression remains to be elucidated. Herein, we identified that ADP-ribosylation factor like-4C (ARL4C) was highly expressed in PTEN-deficient human GBM cells and tissues. Mechanistically, loss of PTEN stabilized ARL4C protein due to AKT/mTOR pathway-mediated inhibition of ARL4C ubiquitination. Functionally, ARL4C enhanced the progression of GBM cells in vitro and in vivo. Moreover, microarray profiling and GST pull-down assay identified that ARL4C accelerated tumor progression via RAC1-mediated filopodium formation. Importantly, targeting PTEN potently inhibited GBM tumor progression in vitro and in vivo, whereas overexpression of ARL4C reversed the tumor progression impaired by PTEN overexpression. Clinically, analyses with patients' specimens validated a negative correlation between PTEN and ARL4C expression. Elevated ARL4C expression but PTEN deficiency in tumor was associated with poorer disease-free survival and overall survival of GBM patients. Taken together, ARL4C is critical for PTEN-deficient GBM progression and acts as a novel prognostic biomarker and a potential therapeutic candidate. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Molecular and physiological roles of Pellino E3 ubiquitin ligases in immunity

The sensing of foreign agents by the innate and adaptive immune system triggers complex signal transduction cascades that culminate in expression of gene patterns that facilitate host protection from the invading agent. Post-translational modification of intracellular signaling proteins in these pathways is a key regulatory mechanism with ubiquitination being one of the important processes that controls levels and activities of signaling molecules. E3 ubiquitin ligases are the determining enzymes in dictating the ubiquitination status of individual proteins. Among these hundred E3 ubiquitin ligases are a family of Pellino proteins that are emerging to be important players in immunity and beyond. Herein, we review the roles of the Pellino E3 ubiquitin ligases in innate and adaptive immunity. We discuss their early discovery and characterization and how this has been aided by the highly conserved nature of innate immune signaling across evolution. We describe the molecular roles of Pellino proteins in immune signaling with particular emphasis on their involvement in pathogen recognition receptor (PRR) signaling. The growing appreciation of the importance of Pellino proteins in a wide range of immune-mediated diseases are also evaluated.     

Linear ubiquitination in immunity

Linear ubiquitination is a post-translational protein modification recently discovered to be crucial for innate and adaptive immune signaling. The function of linear ubiquitin chains is regulated at multiple levels: generation, recognition, and removal. These chains are generated by the linear ubiquitin chain assembly complex (LUBAC), the only known ubiquitin E3 capable of forming the linear ubiquitin linkage de novo. LUBAC is not only relevant for activation of nuclear factor-κB (NF-κB) and mitogen-activated protein kinases (MAPKs) in various signaling pathways, but importantly, it also regulates cell death downstream of immune receptors capable of inducing this response. Recognition of the linear ubiquitin linkage is specifically mediated by certain ubiquitin receptors, which is crucial for translation into the intended signaling outputs. LUBAC deficiency results in attenuated gene activation and increased cell death, causing pathologic conditions in both, mice, and humans. Removal of ubiquitin chains is mediated by deubiquitinases (DUBs). Two of them, OTULIN and CYLD, are constitutively associated with LUBAC. Here, we review the current knowledge on linear ubiquitination in immune signaling pathways and the biochemical mechanisms as to how linear polyubiquitin exerts its functions distinctly from those of other ubiquitin linkage types.     

Golgi phosphoprotein 3 (GOLPH3) promotes hepatocellular carcinoma cell aggressiveness by activating the NF‐κB pathway

Hepatocellular carcinoma (HCC) is one of the most lethal malignancies, in which the NF‐κB pathway plays an important role and is constitutively activated. Better understanding of the molecular pathogenesis of HCC and the NF‐κB pathway are needed to improve patient outcomes. Herein, we identified an unappreciated protein involved in NF‐κB‐induced activation, Golgi phosphoprotein 3 (GOLPH3). The mRNA and protein expression levels of GOLPH3 were frequently up‐regulated in HCC and GOLPH3 expression correlated closely with clinical stage and survival in both the testing and validation cohorts. Ectopic over‐expression of GOLPH3 in PLC/PRF/5 (PLC) and Huh7 HCC cells protected against cisplatin‐induced apoptosis, promoted angiogenesis and proliferation and increased the aggressiveness of HCC cells in vitro and in vivo, whereas inhibition of GOLPH3 led to decreased aggressiveness. Through analysis of two published HCC patient profiles, GOLPH3 expression significantly correlated with NF‐κB signalling. Furthermore, we demonstrated that GOLPH3 promoted K63‐linked polyubiquitination of tumour necrosis factor receptor‐associated factor 2 (TRAF2), receptor interacting protein (RIP) and NF‐κB essential modulator (NEMO) and substantially sustained the activation of NF‐κB in HCC cells. Taken together, our findings provided evidence that GOLPH3 is a prognostic and/or potential therapeutic biomarker for HCC patients and plays an important role in activation of the NF‐κB pathway during HCC progression. Copyright © 2014 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.