RP105 Engages Phosphatidylinositol 3-Kinase p110δ To Facilitate the Trafficking and Secretion of Cytokines in Macrophages during Mycobacterial Infection

Polymorphisms in PI3K/AKT genes and gene‑smoking interaction are associated with susceptibility to tuberculosis

BACKGROUND

Phosphatidylinositol 3-kinase (PI3K) and protein kinase B (AKT) are involved in the clearance of Mycobacterium tuberculosis (MTB) by macrophages.

AIM

This study aimed to investigate the effects of polymorphisms in the PI3K/AKT genes and the gene-smoking interaction on susceptibility to TB.

METHODS

This case-control study used stratified sampling to randomly select 503 TB patients and 494 control subjects. Logistic regression analysis was used to determine the association between the polymorphisms and TB. Simultaneously, the marginal structure linear dominance model was used to estimate the gene-smoking interaction.

RESULTS

Genotypes GA (OR 1.562), AA (OR 2.282), and GA + AA (OR 1.650) at rs3730089 of the PI3KR1 gene were significantly associated with the risk to develop TB. Genotypes AG (OR 1.460), GG (OR 2.785), and AG + GG (OR 1.622) at rs1130233 of the AKT1 gene were significantly associated with the risk to develop TB. In addition, the relative excess risk of interaction (RERI) between rs3730089 and smoking was 0.9608 (95% CI: 0.5959, 1.3256, p < 0.05), which suggests a positive interaction.

CONCLUSION

We conclude that rs3730089 and rs1130233 are associated with susceptibility to TB, and there was positive interaction between rs3730089 and smoking on susceptibility to TB.

MiR-92a/KLF4/p110δ regulates titanium particles-induced macrophages inflammation and osteolysis

As total joint replacement is widely applied for severe arthropathy, peri-prosthetic aseptic loosening as one of the main causes of implant failure has drawn wide attention. Wear particles such as titanium particles (TiPs) derived from prosthesis can initiate macrophages inflammation and sequentially activate osteoclasts, which results in bone resorption and osteolysis for long-term. Therefore, inhibiting wear particles induced macrophages inflammation is considered as a promising therapy for AL. In this research, we found that the inhibition of p110δ, a member of class IA PI3Ks family, could significantly dampen the TiPs-induced secretion of TNFα and IL-6. By the transfection of siRNA targeting p110δ, we confirmed that p110δ was responsible for TNFα and IL-6 trafficking out of Golgi complex without affecting their expression in TiPs-treated macrophages. As the upstream transcription-repressor of p110δ, Krüppel-like factor 4 (KLF4), targeted by miR-92a, could also attenuate TiPs-induced inflammation by mediating NF-κB pathway and M1/M2 polarization. To further ascertain the roles of KLF4/p110δ, TiPs-induced mice cranial osteolysis model was established and vivo experiments validated that KLF4-knockdown could exacerbate TiPs-induced osteolysis, which was strikingly ameliorated by knockdown of p110δ. In summary, our study suggests the key role of miR-92a/KLF4/p110δ signal in TiPs-induced macrophages inflammation and osteolysis.

Rab6b localizes to the Golgi complex in murine macrophages and promotes tumor necrosis factor release in response to mycobacterial infection

The proinflammatory cytokine tumor necrosis factor (TNF) plays a central role in the host control of mycobacterial infections. Expression and release of TNF are tightly regulated, yet the molecular mechanisms that control the release of TNF by mycobacteria-infected host cells, in particular macrophages, are incompletely understood. Rab GTPases direct the transport of intracellular membrane-enclosed vesicles and are important regulators of macrophage cytokine secretion. Rab6b is known to be predominantly expressed in the brain where it functions in retrograde transport and anterograde vesicle transport for exocytosis. Whether it executes similar functions in the context of immune responses is unknown. Here we show that Rab6b is expressed by primary mouse macrophages, where it localized to the Golgi complex. Infection with Mycobacterium bovis bacille Calmette-Guérin (BCG) resulted in dynamic changes in Rab6b expression in primary mouse macrophages in vitro as well as in organs from infected mice in vivo. We further show that Rab6b facilitated TNF release by M. bovis BCG-infected macrophages, in the absence of discernible impact on Tnf messenger RNA and intracellular TNF protein expression. Our observations identify Rab6b as a positive regulator of M. bovis BCG-induced TNF trafficking and secretion by macrophages and positions Rab6b among the molecular machinery that orchestrates inflammatory cytokine responses by macrophages.

Comprehensive Analysis of Human Cytomegalovirus- and HIV-Mediated Plasma Membrane Remodeling in Macrophages

The plasma membrane (PM) must be overcome by viruses during entry and release. Furthermore, the PM represents the cellular communication compartment and the immune system interface. Hence, viruses have evolved sophisticated strategies to remodel the PM, for instance to avoid immune sensing and clearance of infected cells. We performed a comprehensive analysis of cell surface dysregulation by two human-pathogenic viruses, human cytomegalovirus (HCMV) and human immunodeficiency virus type 1 (HIV-1), in primary macrophages, which are classical antigen-presenting cells and orchestrators of the immune system. Scanning ion conductance microscopy revealed a loss of roughness and an overall smooth phenotype of HCMV-infected macrophages, in contrast to HIV-1 infection. This phenotype was also evident on the molecular level. When we screened for cell surface receptors modulated by HCMV, 42 of 332 receptors tested were up- or downregulated, whereas HIV-1 affected only 7 receptors. In particular CD164, CD84, and CD180 were targeted by HCMV. Mechanistically, HCMV induced transcriptional silencing of these receptors in an interferon (IFN)-independent manner, and expression was reduced not only by lab-adapted HCMV but also by clinical HCMV isolates. Altogether, our plasma membrane profiling of human macrophages provides clues to understand how viruses evade the immune system and identified novel cell surface receptors targeted by HCMV. IMPORTANCE The PM is a key component that viruses have to cope with. It is a barrier for infection and egress and is critically involved in antiviral immune signaling. We hence asked the question how two immunomodulatory viruses, HIV-1 and HCMV, dysregulate this compartment in infected macrophages, relevant in vivo targets of both viruses. We employed a contact-free microscopic technique to image the PM of infected cells and performed a phenotypic flow cytometry-based screen to identify receptor modulations on a molecular level. Our results show that HIV-1 and HCMV differentially manipulate the PM of macrophages. While HIV-1-mediated changes are relatively subtle, HCMV induces major alterations of the PM. We identify novel immune receptors manipulated by HCMV and define mechanisms of how HCMV interferes with receptor expression. Altogether, our study reveals differential strategies of how two human-pathogenic viruses manipulate infected cells and identifies potential novel pathways of HCMV immune evasion.

The Potential Role of RP105 in Regulation of Inflammation and Osteoclastogenesis During Inflammatory Diseases

Inflammatory diseases have a negative impact on bone homeostasis via exacerbated local and systemic inflammation. Bone resorbing osteoclasts are mainly derived from hematopoietic precursors and bone marrow monocytes. Induced osteoclastogenesis during inflammation, autoimmunity, metabolic diseases, and cancers is associated with bone loss and osteoporosis. Proinflammatory cytokines, pathogen-associated molecular patterns, or endogenous pathogenic factors induce osteoclastogenic differentiation by binding to the Toll-like receptor (TLR) family expressed on surface of osteoclast precursors. As a non-canonical member of the TLRs, radioprotective 105 kDa (RP105 or CD180) and its ligand, myeloid differentiation protein 1 (MD1), are involved in several bone metabolic disorders. Reports from literature had demonstrated RP105 as an important activator of B cells, bone marrow monocytes, and macrophages, which regulates inflammatory cytokines release from immune cells. Reports from literature had shown the association between RP105 and other TLRs, and the downstream signaling mechanisms of RP105 with different “signaling-competent” partners in immune cells during different disease conditions. This review is focused to summarize: (1) the role of RP105 on immune cells’ function and inflammation regulation (2) the potential regulatory roles of RP105 in different disease-mediated osteoclast activation and the underlying mechanisms, and (3) the different “signaling-competent” partners of RP105 that regulates osteoclastogenesis.

SILAC-based quantitative proteomics reveals pleiotropic, phenotypic modulation in primary murine macrophages infected with the protozoan pathogen Leishmania donovani

Leishmaniases are major vector-borne tropical diseases responsible for great human morbidity and mortality, caused by protozoan, trypanosomatid parasites of the genus Leishmania. In the mammalian host, parasites survive and multiply within mononuclear phagocytes, especially macrophages. However, the underlying mechanisms by which Leishmania spp. affect their host are not fully understood. Herein, proteomic alterations of primary, bone marrow-derived BALB/c macrophages are documented after 72 h of infection with Leishmania donovani insect-stage promastigotes, applying a SILAC-based, quantitative proteomics approach. The protocol was optimised by combining strong anion exchange and gel electrophoresis fractionation that displayed similar depth of analysis (combined total of 6189 mouse proteins). Our analyses revealed 86 differentially modulated proteins (35 showing increased and 51 decreased abundance) in response to Leishmania donovani infection. The proteomics results were validated by analysing the abundance of selected proteins. Intracellular Leishmania donovani infection led to changes in various host cell biological processes, including primary metabolism and catabolic process, with a significant enrichment in lysosomal organisation. Overall, our analysis establishes the first proteome of bona fide primary macrophages infected ex vivo with Leishmania donovani, revealing new mechanisms acting at the host/pathogen interface. SIGNIFICANCE: Little is known on proteome changes that occur in primary macrophages after Leishmania donovani infection. This study describes a SILAC-based quantitative proteomics approach to characterise changes of bone marrow-derived macrophages infected with L. donovani promastigotes for 72 h. With the application of SILAC and the use of SAX and GEL fractionation methods, we have tested new routes for proteome quantification of primary macrophages. The protocols developed here can be applicable to other diseases and pathologies. Moreover, this study sheds important new light on the "proteomic reprogramming" of infected macrophages in response to L. donovani promastigotes that affects primary metabolism, cellular catabolic processes, and lysosomal/vacuole organisation. Thus, our study reveals key molecules and processes that act at the host/pathogen interface that may inform on new immuno- or chemotherapeutic interventions to combat leishmaniasis.

Inhibition of microRNA-141-3p Reduces Hypoxia-Induced Apoptosis in H9c2 Rat Cardiomyocytes by Activating the RP105-Dependent PI3K/AKT Signaling Pathway

BACKGROUND Oxidative stress in myocardial ischemia results in cardiomyocyte apoptosis. The expression of microRNA-141-3p (miR-141-3p) and the 105 kD toll-like receptor protein (TLR), RP105, have been identified in cardiomyocytes in vitro. This study aimed to investigate the effects of hypoxia in H9c2 rat cardiomyoblasts with and without the inhibition of miR-141-3p and to investigate the expression of RP105 and the PI3K/AKT signaling pathway. MATERIAL AND METHODS H9c2 rat cardiomyoblasts were cultured in conditions of hypoxia and treated with a specific miR-141-3p-inhibitor. RP105 short-interfering RNA (siRNA) was constructed, and LY294002 was used to inhibit the PI3KA/AKT pathway. The fluorescent probe, dihydroethidium (DHE), was used to detect reactive oxygen species (ROS). Flow cytometry evaluated ROS and apoptosis. Quantitative real-time polymerase chain reaction (RT-qPCR) and Western blot studied the expression of the PI3K/AKT pathway genes and proteins. Bioinformatics and dual-luciferase reporter assays were used to identify the targets for miR-141-3p. RESULTS A predictive TargetScan algorithm showed that the RP105 gene was a potential target of miR-141-3p. Expression of miR-141-3p was significantly increased in hypoxic H9c2 cells, and inhibition of miR-141-3p increased cell viability and reduced apoptosis. Also, miR-141-3p was shown to target 3'-UTR of RP105. Down-regulation of RP105 associated with hypoxia and its downstream PI3K/AKT pathway were significantly increased following miR-141-3p inhibition. The protective effect of miR-141-3p inhibition in hypoxic H9c2 cells was abolished by the absence of RP105 and inhibition of PI3K/AKT. CONCLUSIONS Inhibition of miR-141-3p reduced hypoxia-induced apoptosis in H9c2 cardiomyocytes in vitro by activating the RP105-dependent PI3K/AKT signaling pathway.

PI3K-p110δ contributes to antibody responses by macrophages in chronic lymphocytic leukemia

Fcγ receptor (FcγR) signalling in monocyte derived macrophages from chronic lymphocytic leukaemia (CLL) patients is poorly understood. This signalling pathway is the key determinant of the ability of the macrophages to respond to therapeutic antibodies in current clinical use for CLL. Muted FcγR signalling activity accompanies disease progression and results in resistance to therapeutic antibodies. The molecular mechanisms controlling FcγR signalling and resistance are unknown. Here, we demonstrate that the class I phosphoinositide 3-kinase (PI3K) catalytic subunit p110δ is essential for CLL-derived macrophages to respond to therapeutic antibodies. Inhibition of p110δ in the macrophages reduces FcγR-mediated antibody immune responses. Surprisingly, our studies indicated that FcγR downstream signalling is independent of SYK and BTK activity. Thus, we show that FcγR antibody responses occur via a previously unidentified p110δ-dependent pathway, which is independent of the previously described SYK/BTK activation pathway. These data provide novel insights into the effectors of antibody responses. Our data also provide mechanistic insights into therapy resistance in CLL.

Deciphering the molecular basis of mycobacteria and lipoglycan recognition by the C-type lectin Dectin-2

Dectin-2 is a C-type lectin involved in the recognition of several pathogens such as Aspergillus fumigatus, Candida albicans, Schistosoma mansonii, and Mycobacterium tuberculosis that triggers Th17 immune responses. Identifying pathogen ligands and understanding the molecular basis of their recognition is one of the current challenges. Purified M. tuberculosis mannose-capped lipoarabinomannan (ManLAM) was shown to induce signaling via Dectin-2, an activity that requires the (α1 → 2)-linked mannosides forming the caps. Here, using isogenic M. tuberculosis mutant strains, we demonstrate that ManLAM is a bona fide and actually the sole ligand mediating bacilli recognition by Dectin-2, although M. tuberculosis produces a variety of cell envelope mannoconjugates, such as phosphatidyl-myo-inositol hexamannosides, lipomannan or manno(lipo)proteins, that bear (α1 → 2)-linked mannosides. In addition, we found that Dectin-2 can recognize lipoglycans from other bacterial species, such as Saccharotrix aerocolonigenes or the human opportunistic pathogen Tsukamurella paurometabola, suggesting that lipoglycans are prototypical Dectin-2 ligands. Finally, from a structure/function relationship perspective, we show, using lipoglycan variants and synthetic mannodendrimers, that dimannoside caps and multivalent interaction are required for ligand binding to and signaling via Dectin-2. Better understanding of the molecular basis of ligand recognition by Dectin-2 will pave the way for the rational design of potent adjuvants targeting this receptor.

Transcriptome Analysis Provides Insights into the Markers of Resting and LPS-Activated Macrophages in Grass Carp (Ctenopharyngodon idella)

Macrophages are very versatile immune cells, with the characteristics of a proinflammatory phenotype in response to pathogen-associated molecular patterns. However, the specific activation marker genes of macrophages have not been systematically investigated in teleosts. In this work, leukocytes (WBC) were isolated using the Percoll gradient method. Macrophages were enriched by the adherent culture of WBC, then stimulated with lipopolysaccharide (LPS). Macrophages were identified by morphological features, functional activity and authorized cytokine expression. Subsequently, we collected samples, constructed and sequenced transcriptomic libraries including WBC, resting macrophage (Mø) and activated macrophage (M(LPS)) groups. We gained a total of 20.36 Gb of clean data including 149.24 million reads with an average length of 146 bp. Transcriptome analysis showed 708 differential genes between WBC and Mø, 83 differentially expressed genes between Mø and M(LPS). Combined with RT-qPCR, we proposed that four novel cell surface marker genes (CD22-like, CD63, CD48 and CD276) and two chemokines (CXCL-like and CCL39.3) would be emerging potential marker genes of macrophage in grass carp. Furthermore, CD69, CD180, CD27, XCL32a.2 and CXCL8a genes can be used as marker genes to confirm whether macrophages are activated. Transcriptome profiling reveals novel molecules associated with macrophages in C. Idella, which may represent a potential target for macrophages activation.

Comparative study of interruption of signaling pathways in lung epithelial cell by two different Mycobacterium tuberculosis lineages

Alveolar epithelial cell (AEC) provides a replication niche for Mycobacterium tuberculosis. Based on the role of AEC in M. tuberculosis pathogenesis and existence of genetic diversity within this bacterium, we investigated interactions between AEC II and two different M. tuberculosis lineages. We have compared the transcriptome and cytokines/chemokines levels of A549 infected by M. tuberculosis lineage three and four using qRT-PCR and ELISA arrays, respectively. We showed different M.  tuberculosis strains induced changes in different effectors that involved in TLRs and NF-κB signaling pathways. We observed different reaction of the studied lineages specifically in pathogenesis, immune evasion mechanism, IL-12/IFN-γ axis, and autophagy. Similar behavior was detected in regarding to apoptosis, necroptosis, anti-inflammatory responses, and canonical inflammasome. Our findings contribute to elucidate more details in pathogenesis, immune evasion strategies, novel target and druggable pathway for therapeutic intervention, and host directed therapy in tuberculosis infection. Also, different M.  tuberculosis lineages-dependent host-pathogen interactions suggested using only one strain for this kind of research will be controversial.

A multi-omic analysis reveals the regulatory role of CD180 during the response of macrophages to Borrelia burgdorferi

Macrophages are cells of the innate immune system with the ability to phagocytose and induce a global pattern of responses that depend on several signaling pathways. We have determined the biosignature of murine bone marrow-derived macrophages and human blood monocytes using transcriptomic and proteomic approaches. We identified a common pattern of genes that are transcriptionally regulated and overall indicate that the response to B. burgdorferi involves the interaction of spirochetal antigens with several inflammatory pathways corresponding to primary (triggered by pattern-recognition receptors) and secondary (induced by proinflammatory cytokines) responses. We also show that the Toll-like receptor family member CD180 is downregulated by the stimulation of macrophages, but not monocytes, with the spirochete. Silencing Cd180 results in increased phagocytosis while tempering the production of the proinflammatory cytokine TNF. Cd180-silenced cells produce increased levels of Itgam and surface CD11b, suggesting that the regulation of CD180 by the spirochete initiates a cascade that increases CR3-mediated phagocytosis of the bacterium while repressing the consequent inflammatory response.

RP105 protects PC12 cells from oxygen‑glucose deprivation/reoxygenation injury via activation of the PI3K/AKT signaling pathway

Radioprotective 105 kDa protein (RP105) has been reported to produce favorable outcomes in various cardiovascular disorders via a toll‑like receptor 4‑dependent or ‑independent manner. However, whether RP105 exerts neuroprotective effects against oxygen‑glucose deprivation (OGD)/reoxygenation (OGD/R) injury remains to be elucidated. In the present study, the PC12 neuronal cell line was exposed to 4 h of OGD followed by 24 h of reoxygenation. Adenoviral vectors encoding RP105 were utilized to upregulate the level of RP105 in PC12 cells prior to OGD/R induction. The results demonstrated that OGD/R reduced the expression of RP105 at the mRNA and protein levels. The overexpression of RP105 significantly reversed OGD/R‑induced neuronal injuries, as demonstrated by the reduced release of lactate dehydrogenate and enhanced cellular viability, in addition to decreased inflammation, apoptosis and reactive oxygen species. The mechanistic evaluations indicated that the neuroprotective functions of RP105 were, in part, a result of activation of the phosphatidylinositol 3‑kinase (PI3K)/protein kinase B (AKT) pathway. In addition, elimination of the PI3K/AKT axis via the use of a pharmacological inhibitor inhibited the OGD/R‑inhibitory effects induced by the overexpression of RP105. Taken together, RP105 protected PC12 cells from OGD/R injury through promotion of the PI3K/AKT pathway; therefore, the RP105‑PI3K‑AKT axis may provide a novel therapeutic target for the prevention of cerebral ischemia/reperfusion injury.

Experimental infection of cattle with Mycobacterium tuberculosis isolates shows the attenuation of the human tubercle bacillus for cattle

The Mycobacterium tuberculosis complex (MTBC) is the collective term given to the group of bacteria that cause tuberculosis (TB) in mammals. It has been reported that M. tuberculosis H37Rv, a standard reference MTBC strain, is attenuated in cattle compared to Mycobacterium bovis. However, as M. tuberculosis H37Rv was isolated in the early 1930s, and genetic variants are known to exist, we sought to revisit this question of attenuation of M. tuberculosis for cattle by performing a bovine experimental infection with a recent M. tuberculosis isolate. Here we report infection of cattle using M. bovis AF2122/97, M. tuberculosis H37Rv, and M. tuberculosis BTB1558, the latter isolated in 2008 during a TB surveillance project in Ethiopian cattle. We show that both M. tuberculosis strains caused reduced gross pathology and histopathology in cattle compared to M. bovis. Using M. tuberculosis H37Rv and M. bovis AF2122/97 as the extremes in terms of infection outcome, we used RNA-Seq analysis to explore differences in the peripheral response to infection as a route to identify biomarkers of progressive disease in contrast to a more quiescent, latent infection. Our work shows the attenuation of M. tuberculosis strains for cattle, and emphasizes the potential of the bovine model as a ‘One Health’ approach to inform human TB biomarker development and post-exposure vaccine development.

Guanine nucleotide exchange factor -H1 promotes inflammatory cytokine production and intracellular mycobacterial elimination in macrophages

Mycobacterium tuberculosis (M.tb), which causes tuberculosis, is a host-adapted intracellular pathogen that can live within macrophages owning to its ability to arrest phagolysosome biogenesis. The guanine nucleotide exchange factor H1 (GEF-H1) may contribute to the phagocytosis of bacteria by macrophages through mediating the crosstalk between microtubules and the actin cytoskeleton. Its role in Shigella infection has been determined but little is known about the role of GEF-H1 in mycobacterial infection. In the present study, we demonstrated that GEF-H1 functioned as a key regulator of the macrophage-mediated anti-mycobacterial response. We found that both mRNA and protein expression levels of GEF-H1 were significantly upregulated in macrophage during mycobacterial infection. Moreover, silencing of GEF-H1 with specific siRNAs reduced the phosphorylation of p38 mitogen-activated protein kinase and TANK binding kinase 1 as well as the expression of interleukin-1β (IL-1β), IL-6, and interferon-β (IFN-β), without affecting nitric oxide production or autophagy. Importantly, GEF-H1 depletion attenuated macrophages-mediated mycobacterial phagocytosis and elimination. Taken together, our data supported that GEF-H1 was a novel regulator of inflammatory cytokine production and mycobacterial elimination, and may serve as a novel potential target for clinical treatment of tuberculosis.

Early diagnosis and effective treatment regimens are the keys to tackle antimicrobial resistance in tuberculosis (TB): A report from Euroscicon's international TB Summit 2016

To say that tuberculosis (TB) has regained a strong foothold in the global human health and wellbeing scenario would be an understatement. Ranking alongside HIV/AIDS as the top reason for mortality due to a single infectious disease, the impact of TB extends far into socio-economic context worldwide. As global efforts led by experts and political bodies converge to mitigate the predicted outcome of growing antimicrobial resistance, the academic community of students, practitioners and researchers have mobilised to develop integrated, inter-disciplinary programmes to bring the plans of the former to fruition. Enabling this crucial requirement for unimpeded dissemination of scientific discovery was the TB Summit 2016, held in London, United Kingdom. This report critically discusses the recent breakthroughs made in diagnostics and treatment while bringing to light the major hurdles in the control of the disease as discussed in the course of the 3-day international event. Conferences and symposia such as these are the breeding grounds for successful local and global collaborations and therefore must be supported to expand the understanding and outreach of basic science research.

Deficiency of Phosphatidylinositol 3-Kinase δ Signaling Leads to Diminished Numbers of Regulatory T Cells and Increased Neutrophil Activity Resulting in Mortality Due to Endotoxic Shock

Despite decades of clinical and biomedical research, the pathogenesis of sepsis and its spectrum of diseases (severe sepsis and septic shock), which are leading causes of death in intensive care units, are still poorly understood. In this article, we show that signaling via the p110δ isoform of PI3K is critical for survival in experimental sepsis. Mice with an inactive knock-in mutation in the p110δ gene (p110δ^D910A) succumbed acutely to nonlethal dose LPS challenge. The susceptibility of p110δ^D910A mice to LPS was associated with increased neutrophil numbers and activities in the tissues, due in part to delayed apoptosis resulting mostly from inherent reduced regulatory T cell (Treg) numbers. Adoptive transfer of wild-type or p110δ^D910A Tregs abrogated exaggerated neutrophil activity, increased neutrophil apoptosis, and rescued p110δ^D910A mice from mortality after LPS challenge. We confirmed the clinical relevance of these findings by showing that human Tregs also regulate neutrophil function and survival. Collectively, our results show that PI3K δ is essential for survival during sepsis. In addition, our data highlight the importance of Tregs in regulating the pathogenesis of sepsis and septic shock via their effects on neutrophil survival and function, and provide evidence of regulation of innate immunity by cells of the adaptive immune system.

Identification of STOML2 as a putative novel asthma risk gene associated with IL6R

BACKGROUND

Functional variants in the interleukin-6 receptor gene (IL6R) are associated with asthma risk. We hypothesized that genes co-expressed with IL6R might also be regulated by genetic polymorphisms that are associated with asthma risk. The aim of this study was to identify such genes.

METHODS

To identify genes whose expression was correlated with that of IL6R, we analyzed gene expression levels generated for 373 human lymphoblastoid cell lines by the Geuvadis consortium and for 38 hematopoietic cell types by the Differentiation Map Portal (DMAP) project. Genes correlated with IL6R were then screened for nearby single nucleotide polymorphisms (SNPs) that were significantly associated with both variation in gene expression levels (eSNPs) and asthma risk.

RESULTS

We identified 90 genes with expression levels correlated with those of IL6R and that also had a nearby eSNP associated with disease risk in a published asthma GWAS (N = 20 776). For 16 (18%) genes, the association between the eSNP and asthma risk replicated with the same direction of effect in a further independent published asthma GWAS (N = 27 378). Among the top replicated associations (FDR < 0.05) were eSNPs for four known (IL18R1, IL18RAP, BCL6, and STAT6) and one putative novel asthma risk gene, stomatin-like protein 2 (STOML2). The expression of STOML2 was negatively correlated with IL6R, while eSNPs that increased the expression of STOML2 were associated with an increased asthma risk.

CONCLUSION

The expression of STOML2, a gene that plays a key role in mitochondrial function and T-cell activation, is associated with both IL-6 signaling and asthma risk.