Reactivations of Latent Viral Infections Are Associated with an Increased Thr389 p70S6k Phosphorylation in Peripheral Lymphocytes of Renal Transplant Recipients

Reactivations of BK polyoma virus (BKPyV) and human cytomegalovirus (HCMV) frequently cause life- and graft-threatening complications after renal transplantation. Both viruses are dependent on the mTOR pathway for replication. In this study we investigated the association of viral replication with mTOR activity in peripheral lymphocytes of renal transplant recipients. A flow-cytometry based assay for the measurement of Thr389 p70S6k phosphorylation, a surrogate marker of the mTOR pathway was established. Forty-eight adult renal transplant recipients were recruited to measure p70S6k activity in their peripheral blood mononuclear cells. This data set in conjunction with information concerning previous replication of BKPyV and HCMV was examined for correlations. Episodes of BKPyV replication were significantly associated with increased p70S6k phosphorylation in CD4⁺ T lymphocytes (p = 0.0002) and CD19⁺ B lymphocytes (p = 0.0073). HCMV infection of patients with a high-risk HCMV constellation of donor and recipient (D+/R−) was associated with increased p70S6k phosphorylation in CD19⁺ B lymphocytes (p = 0.0325). These associations were found to be independent of the trough levels of the immunosuppressive drugs. Conclusion: P70S6k phosphorylation in peripheral lymphocytes is associated with BKPyV reactivations and to a lesser extent with HCMV infections in renal transplant recipients.

S6K1/S6 axis-regulated lymphocyte activation is important for adaptive immune response of Nile tilapia

Ribosomal protein S6 kinase beta-1 (S6K1) is a serine/threonine kinase downstream of the mechanistic target of rapamycin (mTOR) pathway, and plays crucial roles in immune regulation. Although remarkable progress has been achieved with a mouse model, how S6K1 regulates adaptive immunity is largely unknown in early vertebrates. In this study, we identified an S6K1 from Nile tilapia Oreochromis niloticus (OnS6K1), and further investigated its potential regulatory role on the adaptive immunity of this fish species. Both sequence and structure of OnS6K1 were highly conserved with its homologs from other vertebrates and invertebrates. OnS6K1 was widely expressed in immune tissues, and with a relative higher expression level in the liver, spleen and head kidney. At the adaptive immune stage of Nile tilapia that infected with Aeromonas hydrophila, mRNA expression of OnS6K1 and its downstream effector S6 was significantly up-regulated in spleen lymphocytes. Meanwhile, their phosphorylation level was also enhanced during this process, suggesting that S6K1/S6 axis participated in the primary response of anti-bacterial adaptive immunity in Nile tilapia. Furthermore, after spleen lymphocytes were activated by the T cell-specific mitogen PHA or lymphocytes agonist PMA in vitro, mRNA and phosphorylation levels of S6K1 were elevated, and phosphorylation of S6 was also enhanced. Once S6K1 activity was blocked by a specific inhibitor, both mRNA and phosphorylation levels of S6 were severely impaired. More importantly, blockade of S6K1/S6 axis reduced the expression of T cell activation marker IFN-γ and CD122 in PHA-activated spleen lymphocytes, indicating the essential role of S6K1/S6 axis in regulating T cell activation of Nile tilapia. Together, our study suggests that S6K1 and its effector S6 regulate lymphocyte activation of Nile tilapia, and in turn promote lymphocyte-mediated adaptive immunity. This study enriched the mechanism of adaptive immune response in teleost and provided useful clues to understand the evolution of adaptive immune system.

IL-37b suppresses T cell priming by modulating dendritic cell maturation and cytokine production via dampening ERK/NF-κB/S6K signalings

Interleukin 37b (IL-37b) plays a key role in suppressing immune responses, partially by modulating the function of dendritic cells (DCs). However, the precise mechanisms are still largely unknown. Here, we investigated the effects of IL-37b on DC maturation and T cell responses induced by DCs, and explored the involved signaling pathways. It was found that IL-37b down-regulated the expressions of co-stimulatory molecules CD80 and CD86 on DCs in vitro. At the same time, the expressions of pro-inflammatory cytokines, such as TNF-α and IL-6, were suppressed, while the expression of the T cell inhibitory cytokine TGF-β was increased in IL-37b-treated DCs. In addition, the activation effect of DCs on T cells was impaired by IL-37b. We further revealed that extracellular single-regulated kinase (ERK), nuclear factor-κB (NF-κB), and mTOR-S6K signaling pathways were involved in the inhibition of DCs induced by IL-37b. This was confirmed by the similarly suppressive effect of chemical inhibitors against NF-κB, ERK, and S6K on the expressions of IL-6 and TNF-α in DCs. In conclusion, these results demonstrated that IL-37b suppressed DC maturation and immunostimulatory capacity in T cell priming by involving in ERK, NF-κB, and S6K-based inhibitory signaling pathways.

Methylome Analysis in Chickens Immunized with Infectious Laryngotracheitis Vaccine

In this study we investigated the methylome of chickens immunized with Infectious laryngotracheitis (ILT) vaccine derived from chicken embryos. Methyl-CpG binding domain protein-enriched genome sequencing (MBD-Seq) method was employed in the detection of the 1,155 differentially methylated regions (DMRs) across the entire genome. After validation, we ascertained the genomic DMRs distribution and annotated them regarding genes, transcription start sites (TSS) and CpG islands. We found that global DNA methylation decreased in vaccinated birds, presenting 704 hypomethylated and 451 hypermethylated DMRs, respectively. Additionally, we performed an enrichment analysis detecting gene networks, in which cancer and RNA post-transcriptional modification appeared in the first place, followed by humoral immune response, immunological disease and inflammatory disease. The top four identified canonical pathways were EIF2 signaling, regulation of EIF4 and p70S6K signaling, axonal guidance signaling and mTOR signaling, providing new insight regarding the mechanisms of ILT etiology. Lastly, the association between DNA methylation and differentially expressed genes was examined, and detected negative correlation in seventeen of the eighteen genes.

Expression of S6K1 in human visceral adipose tissue is upregulated in obesity and related to insulin resistance and inflammation

The ribosomal protein S6 kinase 1 (S6K1) is a component of the insulin signalling pathway that has been proposed as a key molecular factor in insulin resistance development under conditions of nutrient overload. The aim was to evaluate the involvement of S6K1 in obesity as well as to explore their association with visceral adipose tissue (VAT) inflammation. Samples obtained from 40 subjects were used. Gene expression levels of RPS6KB1 and key inflammatory markers were analysed in VAT. The effect of insulin on transcript levels of RPS6KB1 in human differentiated adipocytes was also explored. RPS6KB1 mRNA levels in VAT were increased (P < 0.05) in obese patients. Insulin treatment significantly enhanced (P < 0.01) gene expression levels of RPS6KB1 and a positive association (P < 0.05) of RPS6KB1 expression with different markers of insulin resistance was observed. Moreover, RPS6KB1 gene expression levels were positively correlated with VAT gene expression levels of the inflammatory markers CCL2, CD68, MMP2, MMP9, VEGFA and CHI3L1 as well as with mRNA levels of MTOR and MAPK8, representative players involved in signalling pathways related to S6K1. The increased levels of S6K1 in obesity and its positive association with insulin resistance and inflammation suggest a role for this protein in the changes that take place in VAT in obesity establishing a link between inflammation and a higher risk for the development of metabolic diseases.

Signaling in Lipopolysaccharide-Induced Stabilization of Formyl Peptide Receptor 1 mRNA in Mouse Peritoneal Macrophages

To identify the TLR4-initiated signaling events that couple to formyl peptide receptor (FPR)1 mRNA stabilization, macrophages were treated with LPS along with a selection of compounds targeting several known signaling pathways. Although inhibitors of protein tyrosine kinases, MAPKs, and stress-activated kinases had little or no effect on the response to LPS, LY294002 (LY2) and parthenolide (an IkappaB kinase inhibitor) were both potent inhibitors. LY2 but not parthenolide blocked the LPS-induced stabilization of FPR1 mRNA. Although both LY2 and wortmannin effectively blocked PI3K activity, wortmannin had little effect on FPR1 expression and did not modulate the decay of FPR1 mRNA. Moreover, although LY2 was demonstrated to be a potent inhibitor of PI3K activity, a structural analog of LY2, LY303511 (LY3), which did not inhibit PI3K, was equally effective at preventing LPS-stimulated FPR1 expression. The mammalian target of rapamycin activity (measured as phospho-p70S6 kinase) was activated by LPS but not significantly blocked by LY2. In addition, although rapamycin blocked mTOR activity, it did not inhibit FPR1 mRNA expression. Finally, the mechanisms involved in stabilization of FPR1 by LPS could be distinguished from those involved in stabilization of AU-rich mRNAs because the prolonged half-life of FPR1 mRNA was insensitive to the inhibition of p38 MAPK. These findings demonstrate that LY2/LY3 targets a novel TLR4-linked signaling pathway that selectively couples to the stabilization of FPR1 mRNA.

Functional characterization of a maize ribosomal S6 protein kinase (ZmS6K), a plant ortholog of metazoan p70(S6K)

Ribosomal protein S6 (S6rp) is phosphorylated by the p70S6K enzyme in mammals, under mitogen/IGF regulation. This event has been correlated with an increase in 5'TOP mRNA translation. In this research, a maize S6 kinase (ZmS6K) was isolated from maize (Zea mays L.) embryonic axes by human p70S6K antibody immunoprecipitation. This enzyme, a 62 kDa peptide, proved to be specific for S6rp phosphorylation, as revealed by in vivo and in vitro kinase activity using either the 40S ribosomal subunit or the RSK synthetic peptide as the substrates. ZmS6K activation was achieved by phosphorylation on serine/threonine residues. Specific phospho-Threo recognition by the p70S6K antibody directed to target phospho-Threo residue 389 correlated with ZmS6K activation. The ZmS6K protein content remained almost steady during maize seed germination, whereas the ZmS6K activity increased during this process, consistent with Zm6SK phosphorylation. Addition of insulin to germinating maize axes proved to increase ZmS6K activity and the extent of S6rp phosphorylation. These events were blocked by rapamycin, an inhibitor of the insulin signal transduction pathway in mammals, at the TOR (target of rapamycin) enzyme level. We conclude that ZmS6K is a kinase, structurally and functionally ortholog of the mammalian p70S6K, responsible for in vivo S6rp phosphorylation in maize. Its activation is induced by insulin in a TOR-dependent manner by phosphorylation on conserved serine/threonine residues.