Jia Nie

FOXP3+ Treg Cells and Gender Bias in Autoimmune Diseases

CD4+CD25+ regulatory T (Treg) cells play a pivotal role in the maintenance of immune homeostasis, where the X-linked master transcription factor forkhead box P3 (FOXP3) determines Treg cell development and function. Genetic deficiency of foxp3 induces dysfunction of Treg cells and immuno-dysregulation, polyendocrinopathy, enteropathy, and X-linked syndrome in humans. Functionally deficient Treg cells or the development of exTreg cells positively correlate with autoimmune diseases, such as systemic lupus erythematosus (SLE), multiple sclerosis (MS), and ankylosing spondylitis (AS). In general, females are more susceptible to SLE and MS but less susceptible to AS, where the expression of FOXP3 and its protein complex are perturbed by multiple factors, including hormonal fluctuations, inflammatory cytokines, and danger signals. Therefore, it is critical to explore the potential molecular mechanisms involved and these differences linked to gender. Here, we review recent findings on the regulation of FOXP3 activity in Treg cells and also discuss gender difference in the determination of Treg cell function in autoimmune diseases.

Nuclear-enriched abundant transcript 1 as a diagnostic and prognostic biomarker in colorectal cancer

BackgroundHigh expression of the long non-coding RNA nuclear-enriched abundant transcript 1 (NEAT1) in whole blood has been reported in colorectal cancer patients; however, its’ clinical significance and origin are unclear. We evaluated the diagnostic and prognostic value, and origin of whole blood NEAT1 in colorectal cancer.MethodsExpression of NEAT1 variants, NEAT1_v1 and NEAT1_v2 were determined using real-time quantitative PCR. The diagnostic value of whole blood NEAT1 expression was evaluated in test (n = 60) and validation (n = 200) cohorts of colorectal cancer patients and normal controls (NCs). To identify the origin of NEAT1, its expression was analyzed in blood, matched primary tumor tissues, para-tumor tissues, metastatic tissues, and also immune cells from patients or NCs. Function of NEAT1 in colorectal cell lines was also assessed. The correlation of NEAT1 expression with clinical outcomes was assessed in 191 patients.ResultsWhole blood NEAT1 expression was significantly higher in colorectal cancer patients than in NCs. NEAT1_v1 and NEAT1_v2 expression were highly accurate in distinguishing colorectal cancer patients from NCs (area under the curve: 0.787 and 0.871, respectively). Knockdown of NEAT1_v1 in vitro could inhibit cell invasion and proliferation, while knockdown of NEAT1_v2 promoted cell growth. However, whole blood expression was not correlated with matched tissues. An elevated expression was seen in neutrophils from CRC patients. Furthermore, high expression of NEAT1_v1 was correlated with worse overall survival. In contrast, high expression of NEAT1_v2 alone was correlated with better overall survival.ConclusionWhole blood NEAT1 expression is a novel diagnostic and prognostic biomarker of overall survival in colorectal cancer. Elevated NEAT1 may derive from neutrophils.

Cutting Edge: Ubiquitin-Specific Protease 4 Promotes Th17 Cell Function under Inflammation by Deubiquitinating and Stabilizing RORγt

RORγt is a key transcription factor that controls the development and function of inflammatory Th17. The mechanisms that regulate RORγt stability remain unclear. We report that Th17 cells highly express the deubiquitinase ubiquitin-specific protease (USP)4, which is essential for maintaining RORγt and Th17 cell function. Inhibition of the catalytic activity of USP4 with vialinin A, a compound derived from Chinese traditional medicine, dampened Th17 differentiation. USP4 interacted and deubiquitinated K48-linked polyubiquitination of RORγt, thereby promoting RORγt function and IL-17A transcription. Interestingly, TGF-β plus IL-6 enhanced USP4-mediated deubiquitination of RORγt. Moreover, USP4 and IL-17 mRNA, but not RORγt mRNA, were significantly elevated in CD4+ T cells from patients with rheumatic heart disease. Thus, USP4 could be a novel therapeutic target for the treatment of Th17-modulated autoimmune diseases.

Negative Regulation of Interferon-induced Transmembrane Protein 3 by SET7-mediated Lysine Monomethylation

Background: IFITM3 is a general antiviral host restriction factor against RNA viruses. Results: SET7-mediated monomethylation of IFITM3 at Lys-88 negatively affected its antiviral activity toward vesicular stomatitis virus (VSV) and influenza A virus (IAV) infection. Conclusion: The monomethylation of antiviral host restriction factors may perturb their function. Significance: Targeting the SET7 pathway could provide new antiviral therapeutic strategies. Although lysine methylation is classically known to regulate histone function, its role in modulating antiviral restriction factor activity remains uncharacterized. Interferon-induced transmembrane protein 3 (IFITM3) was found monomethylated on its lysine 88 residue (IFITM3-K88me1) to reduce its antiviral activity, mediated by the lysine methyltransferase SET7. Vesicular stomatitis virus and influenza A virus infection increased IFITM3-K88me1 levels by promoting the interaction between IFITM3 and SET7, suggesting that this pathway could be hijacked to support infection; conversely, IFN-α reduced IFITM3-K88me1 levels. These findings may have important implications in the design of therapeutics targeting protein methylation against infectious diseases.

Inflammation negatively regulates FOXP3 and regulatory T-cell function via DBC1.

Significance Treg cells suppress excessive and aberrant immune responses. Impaired function or homeostasis of Treg cells would induce severe autoimmune and inflammatory diseases. Forkhead box P3 (FOXP3), as a master regulator of Treg cells, forms a large complex with other binding factors to modulate Treg-cell function subtly in pathological and physiological conditions. We identified that Deleted in breast cancer 1 (DBC1) is an essential subunit of the FOXP3 complex in human CD4+ Treg cells. Our results show that the inflammatory cytokines TNF-α or IL-6 trigger FOXP3 degradation, whereas downregulation of DBC1 expression prevents FOXP3 degradation and maintains Treg-cell function under inflammatory stimuli in vitro and in vivo. These findings unveil a previously unidentified pathway for therapeutically modulating FOXP3+ Treg-cell stability under inflammation. Forkhead box P3 (FOXP3)-positive Treg cells are crucial for maintaining immune homeostasis. FOXP3 cooperates with its binding partners to elicit Treg cells’ signature and function, but the molecular mechanisms underlying the modulation of the FOXP3 complex remain unclear. Here we report that Deleted in breast cancer 1 (DBC1) is a key subunit of the FOXP3 complex. We found that DBC1 interacts physically with FOXP3, and depletion of DBC1 attenuates FOXP3 degradation in inflammatory conditions. Treg cells from Dbc1-deficient mice were more resistant to inflammation-mediated abrogation of Foxp3 expression and function and delayed the onset and severity of experimental autoimmune encephalomyelitis and colitis in mice. These findings establish a previously unidentified mechanism regulating FOXP3 stability during inflammation and reveal a pathway for potential therapeutic modulation and intervention in inflammatory diseases.

Reciprocal regulation of RORγt acetylation and function by p300 and HDAC1

T helper 17 (Th17) cells not only play critical roles in protecting against bacterial and fungal infections but are also involved in the pathogenesis of autoimmune diseases. The retinoic acid-related orphan receptor (RORγt) is a key transcription factor involved in Th17 cell differentiation through direct transcriptional activation of interleukin 17(A) (IL-17). How RORγt itself is regulated remains unclear. Here, we report that p300, which has histone acetyltransferase (HAT) activity, interacts with and acetylates RORγt at its K81 residue. Knockdown of p300 downregulates RORγt protein and RORγt-mediated gene expression in Th17 cells. In addition, p300 can promote RORγt-mediated transcriptional activation. Interestingly, the histone deacetylase (HDAC) HDAC1 can also interact with RORγt and reduce its acetylation level. In summary, our data reveal previously unappreciated posttranslational regulation of RORγt, uncovering the underlying mechanism by which the histone acetyltransferase p300 and the histone deacetylase HDAC1 reciprocally regulate the RORγt-mediated transcriptional activation of IL-17.

MicroRNA‐191 acts as a tumor promoter by modulating the TET1–p53 pathway in intrahepatic cholangiocarcinoma

Current treatment of intrahepatic cholangiocarcinoma (ICC) remains ineffective because knowledge of ICC carcinogenesis is unclear. Increasing evidence suggests that microRNAs (miRNAs), including miR‐191, play an important role in tumorigenesis; but expression and biological functions of miR‐191 in ICC remain to be established. This study investigated the functions and underlying mechanisms of miR‐191 in ICC. ICC miRNA profiles were generated in five pairs of ICC and matched to normal bile duct tissues by next‐generation sequencing technology; ICC miRNA profiles were verified in 18 pairs of ICC tissues and normal bile duct tissues by quantitative RT‐PCR. The miR‐191‐associated mechanisms in ICC were investigated in vitro and in vivo, and clinical outcomes associated with miR‐191 were correlated in 84 patients. Our results showed that miR‐191 expression was significantly increased in ICC compared with the adjacent normal bile duct tissues (P < 0.001). Overexpression of miR‐191 promoted proliferation, invasion, and migration of cholangiocarcinoma cells in vitro and in vivo. The elevated miR‐191 expression reduced the expression level of ten‐eleven translocation 1 (TET1)—a direct target gene of miR‐191 in ICC, which catalyzes demethylation. The reduced TET1 expression level allowed the methylated CpG‐rich regions at the p53 gene transcription start site stay methylated, leading to reduced p53 expression level, which compromises p53s anticancer vigor. Finally, miR‐191 was found to be an independent risk factor for poor prognosis in patients with ICC (overall survival, hazard ratio = 3.742, 95% confidence interval 2.080‐6.733, P < 0.001; disease‐free survival, hazard ratio = 2.331, 95% confidence interval 1.346‐4.037, P = 0.003). Conclusion: Our results suggest that overexpressed miR‐191 is associated with ICC progression through the miR‐191/TET1/p53 pathway. (Hepatology 2017;66:136–151).

The Deubiquitinase USP17 Regulates the Stability and Nuclear Function of IL-33

IL-33 is a new member of the IL-1 family cytokines, which is expressed by different types of immune cells and non-immune cells. IL-33 is constitutively expressed in the nucleus, where it can act as a transcriptional regulator. So far, no direct target for nuclear IL-33 has been identified, and the regulation of IL-33 nuclear function remains largely unclear. Here, we report that the transcription of type 2 inflammatory cytokine IL-13 is positively regulated by nuclear IL-33. IL-33 can directly bind to the conserved non-coding sequence (CNS) before the translation initiation site in the IL13 gene locus. Moreover, IL-33 nuclear function and stability are regulated by the enzyme ubiquitin-specific protease 17 (USP17) through deubiquitination of IL-33 both at the K48 and at the K63 sites. Our data suggest that IL13 gene transcription can be directly activated by nuclear IL-33, which is negatively regulated by the deubiquitinase USP17.

Poly(ADP-ribosyl)ation of FOXP3 Protein Mediated by PARP-1 Protein Regulates the Function of Regulatory T Cells

Background: PARP-1 has importance in the immune system. Results: Poly(ADP-ribosyl)ation of FOXP3 mediated by PARP-1 destabilizes FOXP3 and negatively regulates the suppressive activity of Treg cells. Conclusion: PARP-1 negatively regulates Treg function via FOXP3 poly(ADP-ribosyl)ation. Significance: This study helps the development of PARP-1 inhibitors to prevent autoimmune diseases. Poly(ADP-ribose) polymerase 1 (PARP-1) is an ADP-ribosylating enzyme participating in diverse cellular functions. The roles of PARP-1 in the immune system, however, have not been well understood. Here we find that PARP-1 interacts with FOXP3 and induces its poly(ADP-ribosyl)ation. By using PARP-1 inhibitors, we show that reduced poly(ADP-ribosyl)ation of FOXP3 results in not only FOXP3 stabilization and increased FOXP3 downstream genes but also enhanced suppressive function of regulatory T cells. Our results suggest that PARP-1 negatively regulates the suppressive function of Treg cells at the posttranslational level via FOXP3 poly(ADP-ribosyl)ation. This finding has implications for developing PARP-1 inhibitors as potential agents for the prevention and treatment of autoimmune diseases.

USP22 is a positive regulator of NFATc2 on promoting IL2 expression

Nuclear factor of activated T cells (NFAT) is an important regulator of T cell activation. However, the molecular mechanism whereby NFATc2 regulates IL2 transcription is not fully understood. In this study, we showed that ubiquitin‐specific protease 22 (USP22), known as a cancer stem cell marker, specifically interacted with and deubiquitinated NFATc2. USP22 stabilized NFATc2 protein levels, which required its deubiquitinase activity. Consistent with these observations, depletion of USP22 in T cells reduced the expression of IL2, which is a cytokine that signifies T effector cell activation. Our findings thus unveil a previously uncharacterized positive regulator of NFATc2, suggesting that targeting the deubiquitinase activity of USP22 could have therapeutic benefit to control IL2 expression and T cell function.