Sepsis-associated encephalopathy: From pathophysiology to clinical management.

Sepsis-associated encephalopathy, which presents as delirium and coma, is a significant complication of sepsis characterized by acute brain dysfunction. The presence of inflammatory pathological changes in the brain of sepsis patients and animal models has been recognized since the 1920 s, initially attributed to the entry of microbial toxins into the brain. In the early 2000 s, attention shifted towards the impact of oxidative stress, the cholinergic system, and cytokines on brain function following sepsis onset. More recently, sepsis-associated encephalopathy has been defined as a diffuse brain dysfunction not directly caused by pathogenic infection of the brain. Currently, there is no evidence-based standard for diagnosing sepsis-associated encephalopathy, and clinical management is primarily focused on symptomatic and supportive measures. This review aims to explore the pathophysiology of sepsis-associated encephalopathy and establish the connection between pathophysiological mechanisms and clinical characteristics. We hope that this work will spark the interest of researchers from various fields and contribute to the advancement of sepsis-associated encephalopathy research.

Inhibition of cluster antigen 36 protects against fatty acid-induced lipid accumulation, oxidative stress, and inflammation in bovine hepatocytes.

When ketosis occurs, supraphysiological concentrations of nonesterified fatty acids (NEFA) display lipotoxicity and are closely related to the occurrence of hepatic lipid accumulation, oxidative stress, and inflammation, resulting in hepatic damage and exacerbating the progression of ketosis. However, the mechanism of these lipotoxic effects caused by high concentrations of NEFA in ketosis is still unclear. Cluster antigen 36 (CD36), a fatty acid transporter, plays a vital role in the development of hepatic pathological injury in nonruminants. Thus, the aim of this study was to investigate whether CD36 plays a role in NEFA-induced hepatic lipotoxicity in dairy cows with clinical ketosis. Liver tissue and blood samples were collected from healthy (n = 10) and clinically ketotic (n = 10) cows at 3 to 15 d in milk. In addition, hepatocytes isolated from healthy calves were treated with 0, 0.6, 1.2, or 2.4 mM NEFA for 12 h; or infected with CD36 expressing adenovirus or CD36 silencing small interfering RNA for 48 h and then treated with 1.2 mM NEFA for 12 h. Compared with healthy cows, clinically ketotic cows had greater concentrations of serum NEFA and ß-hydroxybutyrate and activities of aspartate aminotransferase and alanine aminotransferase but lower serum glucose. In addition, dairy cows with clinical ketosis displayed excessive hepatic lipid accumulation. More importantly, these alterations were accompanied by an increased abundance of hepatic CD36. In the cell culture model, exogenous NEFA (0, 0.6, 1.2, or 2.4 mM) treatment could dose-dependently increase the abundance of CD36. Meanwhile, NEFA (1.2 mM) increased the content of triacylglycerol, reactive oxygen species and malondialdehyde, and decreased the activities of glutathione peroxidase and superoxide dismutase. Moreover, NEFA upregulated phosphorylation levels of nuclear factor κB (NF-κB) and the inhibitor of NF-κB (IκB) α, along with the upregulation of protein abundance of NLR family pyrin domain containing 3 (NLRP3) and caspase-1, and mRNA abundance of IL1B, IL6, and tumor necrosis factor α (TNFA). These alterations induced by NEFA in bovine hepatocytes were associated with increased lipid accumulation, oxidative stress and inflammation, which could be further aggravated by CD36 overexpression. Conversely, silencing CD36 attenuated these NEFA-induced detriments. Overall, these data suggest that CD36 may be a potential therapeutic target for NEFA-induced hepatic lipid accumulation, oxidative stress, and inflammation in dairy cows.

[Production and characterization of a novel aminopeptidase A from Lactococcus lactis].

Aminopeptidase A (Pep A) is a metal-dependent enzyme that specifically hydrolyze peptides with the N-terminal amino acids glutamic acid (Glu) and aspartic acid (Asp). A possible application of PepA is the hydrolysis of Glu/Asp-rich food proteins such as wheat gluten and casein, increasing the flavor and solubility of food protein. In the present study, the gene encoding a Pep A from Lactococcus lactis ssp. lactis IL1403 was synthesized and introduced into Pichia pastoris GS115 (His4). Lc-Pep A was successfully expressed and secreted to the culture medium, followed by identification and purification to homogeneity. Characteristics study demonstrated that Lc-Pep A could specifically hydrolyze the substrates Glu-pNA and Asp-pNA with similar catalytic activity, and this was further confirmed by the kinetics parameters measured. Additionally, Lc-Pep A showed a broad thermostability and pH stability with an optimum temperature of 60 ℃ and an optimum pH of 8.0. The enzyme activity of Lc-Pep A was activated by metal ions Co2+, Mn2+, and Zn2+ but was strongly inhibited by Ni2+and Cu2+. The routine proteinase inhibitor had no effect on the activity of Lc-Pep A. However, Lc-Pep A was strongly inhibited by the metallopeptidase inhibitor, EDTA, and disulfide bond-reducing agents. The study may facilitate production and application of Lc-Pep A.

Low abundance of insulin-induced gene 1 contributes to SREBP-1c processing and hepatic steatosis in dairy cows with severe fatty liver.

Fatty liver is a major metabolic disorder of high-producing dairy cows during the transition period. In nonruminants, it is well established that insulin-induced gene 1 (INSIG1) plays a crucial role in regulating hepatic lipogenesis by controlling the anchoring of sterol regulatory element-binding protein 1 (SREBP-1) on the endoplasmic reticulum along with SREBP cleavage-activating protein (SCAP). Whether the INSIG1-SCAP-SREBP-1c transport axis is affected in cows experiencing fatty liver is unknown. Thus, the aim of this study was to investigate the potential role of INSIG1-SCAP-SREBP-1c axis in the progression of fatty liver in dairy cows. For in vivo experiments, 24 dairy cows at the start of their fourth lactation (median; range 3-5) and 8 d in milk (median; range 4-12 d) were selected into a healthy group [n = 12; triglyceride (TG) content <1%] and a severe fatty liver group (n = 12; TG content >10%) according to their hepatic TG content. Blood samples were collected for detecting serum concentrations of free fatty acids, ß-hydroxybutyrate, and glucose. Compared with healthy cows, cows with severe fatty liver had higher serum concentrations of ß-hydroxybutyrate and free fatty acids and lower concentration of glucose. Liver biopsies were used to detect the status of INSIG1-SCAP-SREBP-1c axis, and the mRNA expression of SREBP-1c-target lipogenic genes acetyl-CoA carboxylase α (ACACA), fatty acid synthase (FASN), and diacylglycerol acyltransferase 1 (DGAT1). Cows with severe fatty liver had lower protein expression of INSIG1 in the hepatocyte endoplasmic reticulum fraction, greater protein expression of SCAP and precursor SREBP-1c in the hepatocyte Golgi fraction, and greater protein expression of mature SREBP-1c in the hepatocyte nuclear fraction. In addition, the mRNA expression of SREBP-1c-target lipogenic genes ACACA, FASN, and DGAT1 was greater in the liver of dairy cows with severe fatty liver. In vitro experiments were conducted on hepatocytes isolated from 5 healthy 1-d-old female Holstein calves, and hepatocytes from each calf were run independently. First, hepatocytes were treated with 0, 200, or 400 µM palmitic acid (PA) for 12 h. Exogenous PA treatment decreased INSIG1 protein abundance, enhanced the endoplasmic reticulum to Golgi export of SCAP-precursor SREBP-1c complex and the nuclear translocation of mature SREBP-1c, all of which was associated with increased transcriptional activation of lipogenic genes and TG synthesis. Second, hepatocytes were transfected with INSIG1-overexpressing adenovirus for 48 h and treated with 400 µM PA 12 h before the end of transfection. Overexpressing INSIG1 inhibited PA-induced SREBP-1c processing, upregulation of lipogenic genes, and TG synthesis in hepatocytes. Overall, the present in vivo and in vitro results indicated that the low abundance of INSIG1 contributed to SREBP-1c processing and hepatic steatosis in dairy cows. Thus, the INSIG1-SCAP-SREBP-1c axis may be a novel target for treatment of fatty liver in dairy cows.

AdipoRon alleviates fatty acid-induced lipid accumulation and mitochondrial dysfunction in bovine hepatocytes by promoting autophagy.

During the transition period in dairy cows, high circulating concentrations of nonesterified fatty acids (NEFA) increase hepatic lipid deposits and are considered a major pathological factor for liver damage. We investigated whether AdipoRon, a synthetic small-molecule agonist of adiponectin receptors 1 and 2 shown to prevent liver lipid accumulation in nonruminants, could alleviate NEFA-induced lipid accumulation and mitochondrial dysfunction. Bovine hepatocytes were isolated from 5 healthy Holstein female newborn calves (1 d of age, 30-40 kg, fasting), and independently isolated hepatocytes from at least 3 different calves were used for each subsequent experiment. The composition and concentration of NEFA used in this study were selected according to hematological criteria of dairy cows with fatty liver or ketosis. First, hepatocytes were cultured with various concentrations of NEFA (0, 0.6, 1.2, or 2.4 mM) for 12 h. In a second experiment, hepatocytes were treated with AdipoRon at different concentrations (0, 5, 25, or 50 µM for 12 h) and times (25 µM for 0, 6, 12, or 24 h) with or without NEFA (1.2 mM) treatment. In the last experiment, hepatocytes were treated with AdipoRon (25 µM), NEFA (1.2 mM), or both for 12 h after treatment with or without the autophagy inhibitor chloroquine. Hepatocytes treated with NEFA had increased protein abundance of sterol regulatory element-binding protein 1c (SREBP-1c) and mRNA abundance of acetyl-CoA carboxylase 1 (ACACA), and decreased protein abundance of peroxisome proliferator-activated receptor α (PPARA), proliferator-activated receptor gamma coactivator-1 α (PGC-1α), mitofusin 2 (MFN2), cytochrome c oxidase subunit IV (COX IV), and mRNA abundance of carnitine palmitoyltransferase 1A (CPT1A), along with lower ATP concentrations. AdipoRon treatment reversed these effects, suggesting this compound had a positive effect on lipid metabolism and mitochondrial dysfunction during the NEFA challenge. In addition, upregulated expression of microtubule-associated protein 1 light chain 3-II (LC3-II, encoded by MAP1LC3) and downregulated expression of sequestosome-1 (SQSTM1, also called p62) indicated that AdipoRon enhanced autophagic activity in hepatocytes. The fact that chloroquine impeded the beneficial effects of AdipoRon on lipid accumulation and mitochondrial dysfunction suggested a direct role for autophagy during NEFA challenge. Our results suggest that autophagy is an important cellular mechanism to prevent NEFA-induced lipid accumulation and mitochondrial dysfunction in bovine hepatocytes, which is consistent with other studies. Overall, AdipoRon may represent a promising therapeutic agent to maintain hepatic lipid homeostasis and mitochondrial function in dairy cows during the transition period.

The E3 ubiquitin ligase NEDD4-1 protects against acetaminophen-induced liver injury by targeting VDAC1 for degradation.

Acetaminophen (APAP) overdose is a major cause of liver injury. Neural precursor cell expressed developmentally downregulated 4-1 (NEDD4-1) is an E3 ubiquitin ligase that has been implicated in the pathogenesis of numerous liver diseases; however, its role in APAP-induced liver injury (AILI) is unclear. Thus, this study aimed to investigate the role of NEDD4-1 in the pathogenesis of AILI. We found that NEDD4-1 was dramatically downregulated in response to APAP treatment in mouse livers and isolated mouse hepatocytes. Hepatocyte-specific NEDD4-1 knockout exacerbated APAP-induced mitochondrial damage and the resultant hepatocyte necrosis and liver injury, while hepatocyte-specific NEDD4-1 overexpression mitigated these pathological events both in vivo and in vitro. Additionally, hepatocyte NEDD4-1 deficiency led to marked accumulation of voltage-dependent anion channel 1 (VDAC1) and increased VDAC1 oligomerization. Furthermore, VDAC1 knockdown alleviated AILI and weakened the exacerbation of AILI caused by hepatocyte NEDD4-1 deficiency. Mechanistically, NEDD4-1 was found to interact with the PPTY motif of VDAC1 through its WW domain and regulate K48-linked ubiquitination and degradation of VDAC1. Our present study indicates that NEDD4-1 is a suppressor of AILI and functions by regulating the degradation of VDAC1.

Nuciferine Ameliorates Nonesterified Fatty Acid-Induced Bovine Mammary Epithelial Cell Lipid Accumulation, Apoptosis, and Impaired Migration via Activating LKB1/AMPK Signaling Pathway.

High blood concentrations of nonesterified fatty acids (NEFAs) provoke various metabolic disorders and are associated with mammary tissue injury and decreased milk production in dairy cows. Nuciferine, an alkaloid found in Nelumbo nucifera leaves, has great potential for correcting lipid metabolism derangements and lipotoxicity. In this study, we evaluated the lipotoxicity induced by excessive NEFA in bovine mammary epithelial cells (bMECs) and investigated whether nuciferine alleviates NEFA-induced lipotoxicity and the underlying molecular mechanisms. We found that excessive NEFA (1.2 and 2.4 mM) induced lipid accumulation, apoptosis, and migration ability impairment in bMECs, whereas nuciferine could ameliorate these disarrangements, as indicated by decreasing triglyceride content, protein abundance of SREBP-1c, cytoplasmic cytochrome c, and cleaved caspase-3 and increasing protein abundance of PPARα and migration ability. Moreover, nuciferine could reverse NEFA-induced LKB1/AMPK signaling inhibition, and the protective effect of nuciferine on lipotoxicity caused by NEFA was abrogated by AMPK inhibitor dorsomorphin. Furthermore, transfection with LKB1 siRNA (si-LKB1) largely abolished the activation effect of nuciferine on AMPK. Overall, nuciferine can protect bMECs from excessive NEFA-induced lipid accumulation, apoptosis, and impaired migration by activating LKB1/AMPK signaling pathway.

Enhanced Programmed Cell Death Protein 1/Programmed Cell Death Ligand 1 Expression Induced by Severe Influenza A Virus Infection Impairs Host's Antiviral Response.

Emerging research shows that the Programmed Cell Death Protein 1/Programmed Cell Death Ligand 1(PD-1/PD-L1) pathway modulates the antiviral response following influenza A virus (IAV) infection, and there is a need to understand further the role of the PD-1/PD-L1 signaling pathway in IAV infection. BALB/c mice were infected with different types of IAV to establish models of varying degrees of infection (mild and severe). The mice were pretreated with or without a PD-1 antagonist to evaluate the role of the PD-1/PD-L1 pathway in IAV infection. The general activity, degree of weight change, viral titer, pathological damage, protein expression, transcriptome level, and cytokine expression were evaluated in the mice. IAV infection, especially severe infection, induced expression of PD-1 and PD-L1 in the lungs and spleen of the mice at 6 days postinfection. Moreover, the expression level was positively correlated with the degree of pathological damage in the lung. PD-1 antagonists can alleviate weight loss in severely infected mice, reduce the viral load and pathological damage, enhance immune response-related gene expression, and induce the most robust responses of interferon-gamma without inducing an obvious Th1/Th17 response. The PD-1/PD-L1 signaling pathway induced by severe IAV infection seriously impairs the host's antiviral response; thus, blocking this signaling pathway may promote IAV recovery.

Bioinformatic analysis of PD-1 checkpoint blockade response in influenza infection.

BACKGROUND: The programmed cell death 1 (PD-1)/PD-1 ligand 1 (PD-L1) signaling pathway is significantly upregulated in influenza virus infection, which impairs the antiviral response. Blocking this signaling pathway may reduce the damage, lower the virus titer in lung tissue, and alleviate the symptoms of infection to promote recovery. In addition to the enhanced viral immune response, using of immune checkpoint inhibitors in influenza virus infection is controversial, the aim of this study was to identify the key factors and regulatory mechanisms in the PD-1 checkpoint blockade response microenvironment in influenza infection. METHODS: A BALB/c mouse model of influenza A/PR8(H1N1) infection was established then constructed, and whole-transcriptome sequencing including mRNAs, miRNAs (microRNAs), lncRNAs (long noncoding RNAs), and circRNAs (circular RNAs) of mice treated with PD-1 checkpoint blockade by antibody treatment and IgG2a isotype control before infection with A/PR8(H1N1) were performed. Subsequently, the differential expression of transcripts between these two groups was analyzed, followed by functional interaction prediction analysis to investigate gene-regulatory circuits. RESULTS: In total, 84 differentially expressed dif-mRNAs, 36 dif-miRNAs, 90 dif-lncRNAs and 22 dif-circRNAs were found in PD-1 antagonist treated A/PR8(H1N1) influenza-infected lungs compared with the controls (IgG2a isotype control treated before infection). In spleens between the above two groups, 45 dif-mRNAs, 36 dif-miRNAs, 57 dif-lncRNAs, and 24 dif-circRNAs were identified. Direct function enrichment analysis of dif-mRNAs and dif-miRNAs showed that these genes were mainly involved in myocardial damage related to viral infection, mitogen activated protein kinase (MAPK) signaling pathways, RAP1 (Ras-related protein 1) signaling pathway, and Axon guidance. Finally, 595 interaction pairs were obtained for the lungs and 462 interaction pairs for the spleens were obtained in the competing endogenous RNA (ceRNA) complex network, in which the downregulated mmu-miR-7043-3p and Vps39-204 were enriched significantly in PD-1 checkpoint blockade treated A/PR8(H1N1) infection group. CONCLUSIONS: The present study provided a basis for the identification of potential pathways and hub genes that might be involved in the PD-1 checkpoint blockade response microenvironment in influenza infection.

Increased adipose tissue lipolysis in dairy cows with fatty liver is associated with enhanced autophagy activity.

Lipolysis is increased in adipose tissue of cows with fatty liver during the transition period. Autophagy, a major cellular degradation process, plays a critical role in adipose tissue homeostasis. The objective of this study was to explore the relationship between lipolysis and autophagy in adipose tissue of cows with fatty liver. Using a nested case-control design, we compared blood and adipose tissue samples from 10 control cows [parity: median = 3, range = 2-4; days in milk: median = 8 d, range = 5-10 d; hepatic triacylglycerol content: median = 0.55% liver wt, range = 0.48-0.61% liver wt] and 10 lactation stage-matched cows with fatty liver (parity: median = 3, range = 2-4; days in milk: median = 9 d, range = 5-11 d; hepatic triacylglycerol content: median = 6.28% liver wt, range = 2.86-7.75% liver wt). Data were analyzed using paired t-tests. Serum concentrations of free fatty acids and ß-hydroxybutyrate were greater and glucose concentration was lower in cows with fatty liver, which we determined by using commercially-available kits. Furthermore, western blotting showed that increased protein abundance of ATGL (adipose triglyceride lipase), ATG5 (autophagy-related gene 5), and ATG7; ratio of phosphorylated (p)-HSL (hormone-sensitive lipase) to HSL and MAP1LC3 (microtubule-associated protein 1 light chain 3, also called LC3-II) to LC3-I along with decreased abundance of PLIN1 (perilipin 1), SQSTM1 (sequestosome-1, also called p62), and the ratio of p-mTOR (phosphorylated mechanistic target of rapamycin) to mTOR in cows with fatty liver. Quantitative reverse-transcription PCR revealed an increase in abundance of MAP1LC3 mRNA and a decrease in SQSTM1 mRNA in cows with fatty liver. These findings were replicated using an adipocyte model. Primary cultures of calf adipocytes isolated from the adipose tissue of the peritoneal omentum and mesentery were treated with 10 mM 3-methyladenine (3-MA), 5 nM rapamycin, 1 µM isoproterenol (ISO), and 1 µM ISO + 10 mM 3-MA. Comparisons among groups were analyzed using one-way ANOVA. Compared with the control, the 1 µM ISO treatment upregulated the abundance of ATGL, the ratio of p-HSL to HSL and LC3-II to LC3-I, and the glycerol content, whereas it downregulated the abundance of PLIN1 and p62 in calf adipocytes. Compared with the 1 µM ISO treatment group, 1 µM ISO + 10 mM 3-MA downregulated the abundance of ATGL, the ratio of p-HSL to HSL and LC3-II to LC3-I, and the glycerol content, whereas it upregulated the abundance of PLIN1 and p62. Compared with the control, the 5 nM rapamycin treatment upregulated the abundance of ATGL, the ratio of p-HSL to HSL and LC3-II to LC3-I, and the glycerol content, whereas it downregulated the abundance of PLIN1 and p62 in calf adipocytes. Overall, these data indicated that increased lipolysis in adipose tissue of cows with fatty liver was associated with enhanced autophagy. However, the specific molecular mechanisms that link lipolysis and autophagy need to be further investigated.

Influenza a virus NS1 resembles a TRAF3-interacting motif to target the RNA sensing-TRAF3-type I IFN axis and impair antiviral innate immunity.

BACKGROUND: Influenza A virus (IAV) evolves strategies to counteract the host antiviral defense for establishing infection. The influenza A virus (IAV) non-structural protein 1 (NS1) is a key viral factor shown to counteract type I IFN antiviral response mainly through targeting RIG-I signaling. Growing evidence suggests that viral RNA sensors RIG-I, TLR3, and TLR7 function to detect IAV RNA in different cell types to induce type I IFN antiviral response to IAV infection. Yet, it remains unclear if IAV NS1 can exploit a common mechanism to counteract these RNA sensing pathways to type I IFN production at once, then promoting viral propagation in the host. METHODS: Luciferase reporter assays were conducted to determine the effect of NS1 and its mutants on the RIG-I and TLR3 pathways to the activation of the IFN-ß and NF-κB promoters. Coimmunoprecipitation and confocal microscopic analyses were used to the interaction and colocalization between NS1 and TRAF3. Ubiquitination assays were performed to study the effect of NS1 and its mutants on TRAF3 ubiquitination. A recombinant mutant virus carrying NS1 E152A/E153A mutations was generated by reverse genetics for biochemical, ex vivo, and in vivo analyses to explore the importance of NS1 E152/E153 residues in targeting the RNA sensing-TRAF3-type I IFN axis and IAV pathogenicity. RESULTS: Here we report that NS1 subverts the RIG-I, TLR3, and TLR7 pathways to type I IFN production through targeting TRAF3 E3 ubiquitin ligase. NS1 harbors a conserved FTEE motif (a.a. 150-153), in which the E152/E153 residues are critical for binding TRAF3 to block TRAF3 ubiquitination and type I IFN production by these RNA sensing pathways. A recombinant mutant virus carrying NS1 E152A/E153A mutations induces higher type I IFN production ex vivo and in vivo, and exhibits the attenuated phenotype in infected mice, indicating the importance of E152/E153 residues in IAV pathogenicity. CONCLUSIONS: Together our work uncovers a novel mechanism of IAV NS1-mediated immune evasion to promote viral infection through targeting the RNA sensing-TRAF3-type I IFN axis.

PPARß/δ agonist alleviates NLRP3 inflammasome-mediated neuroinflammation in the MPTP mouse model of Parkinson's disease.

Recent studies have indicated that peroxisome proliferator-activated receptor ß/δ (PPARß/δ) agonists exert neuroprotective effects in the model of Parkinson's disease (PD). Furthermore, PPARß/δ agonists have been shown to have potential anti-inflammatory activity, but the underlying mechanisms remain obscure. Emerging evidence indicates that the nucleotide-binding domain and leucine-rich-repeat-protein 3 (NLRP3) inflammasome-mediated neuroinflammation plays a crucial role in the pathogenesis of PD. In the present study we investigate whether PPARß/δ agonists alleviate NLRP3-mediated neuroinflammation in the 1- methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) mouse model of PD. We administered GW501516, a selective and high-affinity PPARß/δ agonist, via intracerebroventricular infusion. Locomotor activities were tested by open field tests and the pole test. The levels of dopamine and its metabolites were determined using highperformance liquid chromatography.Dopaminergic neurodegeneration was assessed via Western blot analysis. The levels of oxidative stress were detected via spectrophotometric assays. The expressions of pro-inflammatory cytokines were measured by performing quantitative real-time RT-PCR and ELISA. Western blot analysis was used to assess NLRP3 inflammasome activation. Our results show that GW501516 reduced movement impairment in PD mice; furthermore, it attenuated dopaminergic neurodegeneration in the midbrain and the depletion of dopamine in the striatum and it inhibited inflammatory reactions and NLRP3 inflammasome activation in the midbrain of PD mice. More importantly, it attenuated astrocytic reaction but had no significant effect on microglial reaction in the midbrain of PD mice. Collectively, our findings demonstrate for the first time that the specific PPARß/δ agonist GW501516 alleviates NLRP3 inflammasome-mediated neuroinflammation in astrocytes in the MPTP mouse model of PD.

ARHGEF39 promotes gastric cancer cell proliferation and migration via Akt signaling pathway.

Dbl-family guanine nucleotide exchange factors (GEFs) can activate RhoGTPases by facilitating the exchange of GDP for GTP, the aberrant expression of which has been implicated in tumorigenicity and metastasis of human cancers. ARHGEF39, as a member of Dbl-family GEFs, was reported to be a potential oncogene in human hepatocellular carcinoma previously. However, the role of ARHGEF39 in gastric cancer (GC) remains unclear so far. In the current study, we demonstrated that ARHGEF39 expression was significantly upregulated in GC tissues compared with paired adjacent normal tissues by quantitative real-time PCR analysis. Functional analyses revealed that ARHGEF39 overexpression could promote proliferation, colony formation, and migration of GC cells in vitro, whereas ARHGEF39 knockdown markedly suppressed these phenotypes. Moreover, ARHGEF39 enhanced tumorigenicity and lung metastasis potential of GC cells in nude mice model. Mechanistically, we found that overexpressed ARHGEF39 significantly increased the phosphorylation level of Akt (p-Akt), and its effect on cell proliferation was attenuated by PI3K inhibitor LY294002. Thus, our findings suggest that ARHGEF39 may contribute to cell proliferation and migration in GC via a possible mechanism involving Akt signaling.

TBK1-associated protein in endolysosomes (TAPE)/CC2D1A is a key regulator linking RIG-I-like receptors to antiviral immunity.

Retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs) are key RNA viral sensors for triggering antiviral immunity. The underlying mechanisms for RLRs to trigger antiviral immunity have yet to be explored. Here we report the identification of TAPE (TBK1-associated protein in endolysosomes) as a novel regulator of the RLR pathways. TAPE functionally and physically interacts with RIG-I, MDA5, and IPS-1 to activate the IFN-ß promoter. TAPE knockdown impairs IFN-ß activation induced by RLRs but not IPS-1. TAPE-deficient cells are defective in cytokine production upon RLR ligand stimulation. During RNA virus infection, TAPE knockdown or deficiency diminishes cytokine production and antiviral responses. Our data demonstrate a critical role for TAPE in linking RLRs to antiviral immunity.