Endosomal signaling and a novel pathway defined by the natural killer receptor KIR2DL4 (CD158d)

Beyond CAR-T: The rise of CAR-NK cell therapy in asthma immunotherapy

Asthma poses a major public health burden. While existing asthma drugs manage symptoms for many, some patients remain resistant. The lack of a cure, especially for severe asthma, compels exploration of novel therapies. Cancer immunotherapy successes with CAR-T cells suggest its potential for asthma treatment. Researchers are exploring various approaches for allergic diseases including membrane-bound IgE, IL-5, PD-L2, and CTLA-4 for asthma, and Dectin-1 for fungal asthma. NK cells offer several advantages over T cells for CAR-based immunotherapy. They offer key benefits: (1) HLA compatibility, meaning they can be used in a wider range of patients without the need for matching tissue types. (2) Minimal side effects (CRS and GVHD) due to their limited persistence and cytokine profile. (3) Scalability for "off-the-shelf" production from various sources. Several strategies have been introduced that highlight the superiority and challenges of CAR-NK cell therapy for asthma treatment including IL-10, IFN-γ, ADCC, perforin-granzyme, FASL, KIR, NCRs (NKP46), DAP, DNAM-1, TGF-β, TNF-α, CCL, NKG2A, TF, and EGFR. Furthermore, we advocate for incorporating AI for CAR design optimization and CRISPR-Cas9 gene editing technology for precise gene manipulation to generate highly effective CAR constructs. This review will delve into the evolution and production of CAR designs, explore pre-clinical and clinical studies of CAR-based therapies in asthma, analyze strategies to optimize CAR-NK cell function, conduct a comparative analysis of CAR-T and CAR-NK cell therapy with their respective challenges, and finally present established novel CAR designs with promising potential for asthma treatment.

Bioinformatic Analysis of the Significance of the KIR2DL4 Gene in Recurrent Implantation Failure

Related studies have pointed out that Killer immunoglobulin-like receptor 2DL4 (KIR2DL4) was associated with vascular remodeling in early pregnancy, and it might play an important role in immunity. In this study, recurrent implantation failure (RIF)-related GSE58144 dataset was extracted from the Gene Expression Omnibus (GEO) database. Firstly, the immune micro-environment analyses were conducted to analyze the pathogenesis of KIR2DL4 in RIF. Then, the gene set enrichment analysis (GSEA) was performed to investigate the function of KIR2DL4. Moreover, the TF-mRNA-miRNA and the co-expression networks were constructed to reveal the potential regulation of KIR2DL4. Furthermore, the genes that were associated with KIR2DL4 and differentially expressed in RIF were obtained and defined as key genes, and the functions of these genes were further explored. KIR2DL4 could be used for clinical diagnosis of RIF, and it was correlated with the changes in the immune micro-environment in RIF. From the perspective of function, KIR2DL4 was associated with complement and coagulation cascades, natural killer cell-mediated cytotoxicity, etc. Moreover, the TF-mRNA-miRNA regulatory network was constructed with KIR2DL4, 9 TFs, and 29 miRNAs. Furthermore, KIR2DL4, ACSM1, IL2RB, and PTPN11 were screened as key genes, which were associated with immune-related functions. This study deeply analyzed the function of KIR2DL4 and its role in RIF, and we found that STAT1 might up-regulate KIR2DL4 by INF-γ/JAK2/STAT1 signaling pathway. Besides, over-expressed KIR2DL4 in the mid-luteal endometrium might influence embryo implantation by affecting the embryo implantation microenvironment, which might help deepen the understanding of the molecular mechanism of RIF.

HLA-G isoforms, HLA-C allotype and their expressions differ between early abortus and placenta in relation to spontaneous abortions

INTRODUCTION

Spontaneous abortion (SAB) affects approximately 10% of clinically recognized pregnancies. Fetal trophobalst invasion and remodeling of maternal spiral arteries is reported to be dependent on crosstalk between HLA-C/HLA-G expressed on extra villous trophoblast (EVTs)and Killer cell Immunoglobin like receptors (KIRs) of decidual NK (dNK). Immune dysfunction in decidua contributes to early miscarriage.

METHODOLOGY

The study used mother neonate paired cord blood and term placenta samples (n = 46), elective abortus (n = 17,gestational age = 10-12 weeks of pregnancy) and SAB abortus (n = 24, gestational age = 12-15 weeks of pregnancy) for HLA-G, KIR2D and HLA-C. In addition, term placenta was collected from women with history of spontaneous pregnancy loss (n = 24) and women with history of live birth (n = 32). SSP-PCR was used for genotyping, RT-PCR for gene expression, copy number variation (CNVs) and HLA-C allotyping and ELISA for protein expression studies.

RESULTS

Membrane bound HLA-G4 isoform proportion was higher 39.28%, p = 0.02) in term placenta. SAB abortus had higher proportion of HLA-G3 (50%),while elective abortus exhibited higher proportion of soluble isoforms (HLA-G5, = 5.9, HLA-G6 = 5.9%, HLA-G7 = 11.8%). Higher inhibitory KIR2DL1 content and copy numbers with lower HLA-C2 in SAB contrasted with higher copy numbers of KIR2DS1(p = 0.001), KIR2DS1+/2DL1+- HLA-C2 combined genotype in healthy placenta. Elevated KIR2D protein levels (p = 0.001), and concurrently, HLA-C levels were upregulated in healthy placenta.

CONCLUSION

Our data supports lower cognate receptor ligand KIR2DS1+/2DL1+ HLA-C2 together with predominance of HLA-G3 isoform in SAB as confounding factors in spontaneous pregnancy loss. HLA-G isoforms and expression differed between first trimester abortus and term placenta suggesting temporal modulation and marks novelty of the study.

Decidual γδT cells of early human pregnancy produce angiogenic and immunomodulatory proteins while also possessing cytotoxic potential

During pregnancy, the maternal immune system must allow and support the growth of the developing placenta while maintaining the integrity of the mother's body. The trophoblast's unique HLA signature is a key factor in this physiological process. This study focuses on decidual γδT cell populations and examines their expression of receptors that bind to non-classical HLA molecules, HLA-E and HLA-G. We demonstrate that decidual γδT cell subsets, including Vδ1, Vδ2, and double-negative (DN) Vδ1-/Vδ2- cells express HLA-specific regulatory receptors, such as NKG2C, NKG2A, ILT2, and KIR2DL4, each with varying dominance. Furthermore, decidual γδT cells produce cytokines (G-CSF, FGF2) and cytotoxic mediators (Granulysin, IFN-γ), suggesting functions in placental growth and pathogen defense. However, these processes seem to be controlled by factors other than trophoblast-derived non-classical HLA molecules. These findings indicate that decidual γδT cells have the potential to actively contribute to the maintenance of healthy human pregnancy.

HLA-G in asthma and its potential as an effective therapeutic agent

OBJECTIVE

Asthma is a heterogeneous disease. Severity of asthma and sensitivity to medications vary across asthma subtypes. Human leukocyte antigen (HLA)-G has a wide range of functions in normal and pathological physiology. Due to its powerful immune function, HLA-G participates in the pathogenesis of different asthma phenotypes by regulating the activity and function of various immune cells. The mechanism of HLA-G in asthma is not fully clear, and there is no consensus on its mechanism in asthma. Further studies are needed to explore the role of HLA-G in different phenotypes of human asthma.

METHODS

Observational study.

RESULTS

HLA-G is an important immunomodulatory factor in asthma. Studies have found different levels of HLA-G in patients with different asthma subtypes and healthy controls, but other studies have come to the opposite conclusion.

CONCLUSION

We speculate that further study on the mechanism of HLA-G in asthma pheno-types may explain some of the contradictions in current studies. Findings should provide information regarding the potential of HLA-G as a novel target for asthma diagnosis and treatment.

KIR3DL05 and KIR3DS02 Recognition of a Nonclassical MHC Class I Molecule in the Rhesus Macaque Implicated in Pregnancy Success

Knowledge of the MHC class I ligands of rhesus macaque killer-cell Ig-like receptors (KIRs) is fundamental to understanding the role of natural killer (NK) cells in this species as a nonhuman primate model for infectious diseases, transplantation and reproductive biology. We previously identified Mamu-AG as a ligand for KIR3DL05. Mamu-AG is a nonclassical MHC class I molecule that is expressed at the maternal-fetal interface of the placenta in rhesus macaques similar to HLA-G in humans. Although Mamu-AG and HLA-G share similar molecular features, including limited polymorphism and a short cytoplasmic tail, Mamu-AG is considerably more polymorphic. To determine which allotypes of Mamu-AG serve as ligands for KIR3DL05, we tested reporter cell lines expressing five different alleles of KIR3DL05 (KIR3DL05*001, KIR3DL05*004, KIR3DL05*005, KIR3DL05*008 and KIR3DL05*X) for responses to target cells expressing eight different alleles of Mamu-AG. All five allotypes of KIR3DL05 responded to Mamu-AG2*01:01, two exhibited dominant responses to Mamu-AG1*05:01, and three had low but detectable responses to Mamu-AG3*03:01, -AG3*03:02, -AG3*03:03 and -AG3*03:04. Since KIR3DL05*X is the product of recombination between KIR3DL05 and KIR3DS02, we also tested an allotype of KIR3DS02 (KIR3DS02*004) and found that this activating KIR also recognizes Mamu-AG2*01:01. Additional analysis of Mamu-AG variants with single amino acid substitutions identified residues in the α1-domain essential for recognition by KIR3DL05. These results reveal variation in KIR3DL05 and KIR3DS02 responses to Mamu-AG and define Mamu-AG polymorphisms that differentially affect KIR recognition.

HLA-G/ILTs Targeted Solid Cancer Immunotherapy: Opportunities and Challenges

Immune checkpoint inhibitors (ICIs) have become a promising immunotherapy for cancers. Human leukocyte antigen-G (HLA-G), a neoantigen, its biological functions and clinical relevance have been extensively investigated in malignancies, and early clinical trials with “anti-HLA-G strategy” are being launched for advance solid cancer immunotherapy. The mechanism of HLA-G as a new ICI is that HLA-G can bind immune cell bearing inhibitory receptors, the immunoglobulin-like transcript (ILT)-2 and ILT-4. HLA-G/ILT-2/-4 (HLA-G/ILTs) signaling can drive comprehensive immune suppression, promote tumor growth and disease progression. Though clinical benefits could be expected with application of HLA-G antibodies to blockade the HLA-G/ILTs signaling in solid cancer immunotherapy, major challenges with the diversity of HLA-G isoforms, HLA-G/ILTs binding specificity, intra- and inter-tumor heterogeneity of HLA-G, lack of isoform-specific antibodies and validated assay protocols, which could dramatically affect the clinical efficacy. Clinical benefits of HLA-G-targeted solid cancer immunotherapy may be fluctuated or even premature unless major challenges are addressed.

Application of a classifier combining bronchial transcriptomics and chest computed tomography features facilitates the diagnostic evaluation of lung cancer in smokers and nonsmokers

Lung cancer screening by computed tomography (CT) reduces mortality but exhibited high false-positive rates. We established a diagnostic classifier combining chest CT features with bronchial transcriptomics. Patients with CT-detected suspected lung cancer were enrolled. The sample collected by bronchial brushing was used for RNA sequencing. The e1071 and pROC packages in R software was applied to build the model. Eventually, a total of 283 patients, including 183 with lung cancer and 100 with benign lesions, were included into final analysis. When incorporating transcriptomic data with radiological characteristics, the advanced model yielded 0.903 AUC with 81.1% NPV. Moreover, the classifier performed well regardless of lesion size, location, stage, histologic type or smoking status. Pathway analysis showed enhanced epithelial differentiation, tumor metastasis, and impaired immunity were predominant in smokers with cancer, whereas tumorigenesis played a central role in nonsmokers with cancer. Apoptosis and oxidative stress contributed critically in metastatic lung cancer; by contrast, immune dysfunction was pivotal in locally advanced lung cancer. Collectively, we devised a minimal-to-noninvasive, efficient diagnostic classifier for smokers and nonsmokers with lung cancer, which provides evidence for different mechanisms of cancer development and metastasis associated with smoking. A negative classifier result will help the physician make conservative diagnostic decisions.

Decidual Natural Killer Cells: A Good Nanny at the Maternal-Fetal Interface During Early Pregnancy

Decidual natural killer (dNK) cells are the tissue-resident and major subpopulation of NK cells at the maternal-fetal interface. It has been demonstrated that dNK cells play pivotal roles in pregnancy, including keeping maternal-fetal immune tolerance, promoting extravillous trophoblast (EVT) cell invasion, and driving uterine spiral artery remodeling. However, the molecular mechanisms haven't been elucidated until recent years. In this review, we systemically introduce the generation, subsets, and surface or soluble molecules of dNK cells, which are critical for maintaining the functions of dNK cells. Further, new functions of dNK cells including well-controlled cytotoxicity, immunosurveillance and immunotrophism supporting via the cell-cell interaction between dNK cells and EVT cells are mainly focused. The molecular mechanisms involved in these functions are also illustrated. Moreover, pregnancy-associated diseases caused by the dNK cells abnormalities are discussed. It will be important for future investigations about the mechanism of maintenance of pregnancy and parturition and potential clinical applications of dNK cells.

The role of KIR positive NK cells in diseases and its importance in clinical intervention

Natural killer (NK) cells are essential for the elimination of the transformed and cancerous cells. Killer cell immunoglobulin-like receptors (KIRs) which expressed by T and NK cells, are key regulator of NK cell function. The KIR and their ligands, MHC class I (HLA-A, B and C) molecules, are highly polymorphic and their related genes are located on 19 q13.4 and 6 q21.3 chromosomes, respectively. It is clear that particular interaction between the KIRs and their related ligands can influence on the prevalence, progression and outcome of several diseases, like complications of pregnancy, viral infection, autoimmune diseases, and hematological malignancies. The mechanisms of immune signaling in particular NK cells involvement in causing pathological conditions are not completely understood yet. Therefore, better understanding of the molecular mechanism of KIR-MHC class I interaction could facilitate the treatment strategy of diseases. The present review focused on the main characteristics and functional details of various KIR and their combination with related ligands in diseases and also highlights ongoing efforts to manipulate the key checkpoints in NK cell-based immunotherapy.

Footprint of the COVID-19 Pandemic in India: A Study of Immune Landscape and Other Factors Shielding Mortality

The impact of the SARS-CoV-2 pandemic has significantly affected global health and created a world crisis. The exponentially increasing numbers of infection and mortality have made preventive measures challenging. India being a highly populated nation has so far effectively counteracted the pandemic outbreak with a significantly lower rate of mortality despite the high infection rates. The genetic architecture of the immune response genes in the Indian population, BCG vaccination, the predominantly young age group of people, and their traditional food habits might contribute to the lower rate of mortality. Human leukocyte antigens (HLA) play a vital role in triggering T cells, and natural killer (NK) cells can immediately react to eliminate infected cells. Activation of virus-specific CD4+ T cells and CD8+ cytotoxic T cells selectively targets the infected cells and strengthens the immunoregulatory system. The checkpoint for NK cell function is the engagement of killer Ig-like receptors (KIR) molecules with their respective HLA ligands overexpressed or expressed on the compromised virus-infected cells which have shown polymorphism among different ethnic groups. Here, we explore if certain KIR-HLA motifs grant Indians a survival advantage in terms of the low rate of mortality. Additionally, enhanced immunity through BCG vaccination may favor fruitful eradication of SARS-CoV-2 and provide the way out as in therapeutic intervention and vaccination strategies.

Identification of immune-related genes with prognostic significance in the microenvironment of cutaneous melanoma

Cutaneous melanoma is one of the most aggressive cancers characterized by increasing incidence and mortality. In recent years, the emergence of immunotherapy has greatly raised the survival rate of patients suffering from cutaneous melanoma, yet some sufferers remain to have poor outcomes after treatment mainly due to the tumor microenvironment (TME). In this study, cutaneous melanoma-associated TME was systematically analyzed using the ESTIMATE algorithm based on the gene transcriptome data obtained from the TCGA database. Totally, 471 patients were included and 553 TME-related genes were screened. Afterwards, a 3-gene signature-based model (CLEC4A, GBP4, KIR2DL4) was constructed via univariate Cox, LASSO, and multivariate Cox regression analyses. To validate the validity of this model, ROC analysis was conducted, and the model was further validated to be an independent prognostic biomarker through univariate and multivariate regression analyses. Finally, the three genes in the model were studied by GSEA and GSVA for their biological significance. We found that the three genes could promote cancer immune response predominantly through affecting immune-related pathways such as antigen processing and presentation, and they may help tumor cells in escaping from surveillance of the immune system when their expression levels were decreased. Additionally, we as well discovered that the expression of the three genes was significantly and positively correlated with the infiltration of related immune cells, but negatively associated with tumor purity. Overall, this study comprehensively analyzed the TME of cutaneous melanoma, identified related biomarkers, and discovered their association with immune system.

Killer Immunoglobulin-Like Receptor 2DL4 (CD158d) Regulates Human Mast Cells both Positively and Negatively: Possible Roles in Pregnancy and Cancer Metastasis

Killer immunoglobulin-like receptor (KIR) 2DL4 (CD158d) was previously thought to be a human NK cell-specific protein. Mast cells are involved in allergic reactions via their KIT-mediated and FcɛRI-mediated responses. We recently detected the expression of KIR2DL4 in human cultured mast cells established from peripheral blood of healthy volunteers (PB-mast), in the human mast cell line LAD2, and in human tissue mast cells. Agonistic antibodies against KIR2DL4 negatively regulate the KIT-mediated and FcɛRI-mediated responses of PB-mast and LAD2 cells. In addition, agonistic antibodies and human leukocyte antigen (HLA)-G, a natural ligand for KIR2DL4, induce the secretion of leukemia inhibitory factor and serine proteases from human mast cells, which have been implicated in pregnancy establishment and cancer metastasis. Therefore, KIR2DL4 stimulation with agonistic antibodies and recombinant HLA-G protein may enhance both processes, in addition to suppressing mast-cell-mediated allergic reactions.

NK Cells as Potential Targets for Immunotherapy in Endometriosis

Endometriosis is a common gynecological disease defined by the presence of endometrial-like tissue outside the uterus, most frequently on the pelvic viscera and ovaries, which is associated with pelvic pains and infertility. It is an inflammatory disorder with some features of autoimmunity. It is accepted that ectopic endometriotic tissue originates from endometrial cells exfoliated during menstruation and disseminating into the peritoneum by retrograde menstrual blood flow. It is assumed that the survival of endometriotic cells in the peritoneal cavity may be partially due to their abrogated elimination by natural killer (NK) cells. The decrease of NK cell cytotoxic activity in endometriosis is associated with an increased expression of some inhibitory NK cell receptors. It may be also related to the expression of human leukocyte antigen G (HLA-G), a ligand for inhibitory leukocyte immunoglobulin-like receptor subfamily B member 1 (LILRB1) receptors. The downregulated cytotoxic activity of NK cells may be due to inhibitory cytokines present in the peritoneal milieu of patients with endometriosis. The role of NK cell receptors and their ligands in endometriosis is also confirmed by genetic association studies. Thus, endometriosis may be a subject of immunotherapy by blocking NK cell negative control checkpoints including inhibitory NK cell receptors. Immunotherapies with genetically modified NK cells also cannot be excluded.

Human Natural Killer Receptors, Co-Receptors, and Their Ligands

In the last 20 years, the study of human natural killer (NK) cells has moved from the first molecular characterizations of very few receptor molecules to the identification of a plethora of receptors displaying surprisingly divergent functions. We have contributed to the description of inhibitory receptors and their signaling pathways, important in fine regulation in many cell types, but unknown until their discovery in the NK cells. Inhibitory function is central to regulating NK-mediated cytolysis, with different molecular structures evolving during speciation to assure its persistence. More recently, it has become possible to characterize the NK triggering receptors mediating natural cytotoxicity, unveiling the existence of a network of cellular interactions between effectors of both natural and adaptive immunity. This unit reviews the contemporary history of molecular studies of receptors and ligands involved in NK cell function, characterizing the ligands of the triggering receptor and the mechanisms for finely regulating their expression in pathogen-infected or tumor cells. © 2018 by John Wiley & Sons, Inc.

Mother-fetus immunogenetic dialogue as a factor of progeny immune system development

Despite the advances in medicine, about 4 million children under the age of 6 months die annually around the world due to infection, which is 450 deaths per hour (UNISEF, 2009). The degree of development of the immune system of children born in time is determined by many factors, including the immunogenetic similarity or difference of mother and fetus organisms, which, in turn, is due to the genotypes of mating pairs, as well as the selection of surrogate mothers duringin vitrofertilization. From our review of the literature, it follows that immunogenetic interactions of mother and fetus organisms, which occur at all stages of pre- and postnatal development, have a signifcant effect on the resistance of offspring to infections and allergens. Before implantation, the mother’s immune responses are formed under the influence of semen fluid antigens, leukocytes and cytokines, as well as under the influence of the genes of the major histocompatibility complex, which are expressed in embryos at the stage of two cells. After implantation, transplacental transfer of immunoglobulins and immunocompetent cells becomes of immunomodulating importance. It is important to emphasize that, although substances with a high molecular weight usually do not pass through the placenta, this rule does not apply to immunoglobulin G (IgG), which, with a molecular weight of about 160 kDa, overcomes the transplacental barrier due to binding to the fetal Fc receptor. The level of IgG in newborns usually correlates with the level of maternal antibodies. During the period of natural feeding, the immune protection of newborns is provided by the mechanisms of innate immunity and the factors of humoral immunity of mothers. It has been shown that immunoglobulins from the milk of many animal species are transferred through the neonatal intestinal epithelium to the blood. Since breast milk contains large amounts of various immunoactive components, including proteins, cytokines, hormones, immunoglobulins, exosomes containing micro-RNA, and viable immune cells, the immunomodulating effects of breast milk persist even after elimination of maternal immunoglobulins from the blood of the offspring, up to maturation. Analysis of a large body of experimental data shows that the study of mechanisms of “motherfetus” and “mother-newborn” interactions are the basis of a knowledge base needed to fnd means of life-long directed modulation of the descendants’ immune status.

Diversification of Bw4 Specificity and Recognition of a Nonclassical MHC Class I Molecule Implicated in Maternal-Fetal Tolerance by Killer Cell Ig-like Receptors of the Rhesus Macaque

The rhesus macaque is an important animal model for AIDS and other infectious diseases; however, studies to address NK cell function in this species have been limited by the lack of defined ligands for killer cell Ig-like receptors (KIRs). To identify ligands for rhesus macaque KIRs, we adopted a novel approach based on a pair of stable cell lines. NFAT-responsive luciferase reporter cell lines expressing the extracellular domains of macaque KIRs fused to the transmembrane and cytoplasmic domains of CD28 and CD3ζ were incubated with target cells expressing individual MHC class I molecules, and ligand recognition was detected by the MHC class I-dependent upregulation of luciferase. Using this approach, we found that Mamu-KIR3DL01, -KIR3DL06, -KIR3DL08, and -KIR3DSw08 all recognize Mamu-Bw4 molecules but with differing allotype specificity. In contrast, Mamu-KIR3DL05 recognizes Mamu-A and Mamu-A-related molecules, including Mamu-A1*002 and -A3*13, Mamu-B*036, the product of a recombinant Mamu-B allele with α1 and α2 domain sequences derived from a MHC-A gene, and Mamu-AG*01, a nonclassical molecule expressed on placental trophoblasts that originated from an ancestral duplication of a MHC-A gene. These results reveal an expansion of the lineage II KIRs in macaques that recognize Bw4 ligands and identify a nonclassical molecule implicated in placental development and pregnancy as a ligand for Mamu-KIR3DL05. In addition to offering new insights into KIR-MHC class I coevolution, these findings provide an important foundation for investigating the role of NK cells in the rhesus macaque as an animal model for infectious diseases and reproductive biology.

Role of MAPK/MNK1 signaling in virus replication

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Viruses are known to exploit cellular signaling pathways.

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MAPK is a major cell signaling pathway activated by diverse group of viruses.

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MNK1 regulates both cap-dependent and IRES-mediated mRNA translation.

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This review discuss the role of MAPK, particularly the role of MNK1 in virus replication.

Viruses are obligate intracellular parasites; they heavily depend on the host cell machinery to effectively replicate and produce new progeny virus particles. Following viral infection, diverse cell signaling pathways are initiated by the cells, with the major goal of establishing an antiviral state. However, viruses have been shown to exploit cellular signaling pathways for their own effective replication. Genome-wide siRNA screens have also identified numerous host factors that either support (proviral) or inhibit (antiviral) virus replication. Some of the host factors might be dispensable for the host but may be critical for virus replication; therefore such cellular factors may serve as targets for development of antiviral therapeutics. Mitogen activated protein kinase (MAPK) is a major cell signaling pathway that is known to be activated by diverse group of viruses. MAPK interacting kinase 1 (MNK1) has been shown to regulate both cap-dependent and internal ribosomal entry sites (IRES)-mediated mRNA translation. In this review we have discuss the role of MAPK in virus replication, particularly the role of MNK1 in replication and translation of viral genome.

Multiple Transceptors for Macro- and Micro-Nutrients Control Diverse Cellular Properties Through the PKA Pathway in Yeast: A Paradigm for the Rapidly Expanding World of Eukaryotic Nutrient Transceptors Up to Those in Human Cells

The nutrient composition of the medium has dramatic effects on many cellular properties in the yeast Saccharomyces cerevisiae. In addition to the well-known specific responses to starvation for an essential nutrient, like nitrogen or phosphate, the presence of fermentable sugar or a respirative carbon source leads to predominance of fermentation or respiration, respectively. Fermenting and respiring cells also show strong differences in other properties, like storage carbohydrate levels, general stress tolerance and cellular growth rate. However, the main glucose repression pathway, which controls the switch between respiration and fermentation, is not involved in control of these properties. They are controlled by the protein kinase A (PKA) pathway. Addition of glucose to respiring yeast cells triggers cAMP synthesis, activation of PKA and rapid modification of its targets, like storage carbohydrate levels, general stress tolerance and growth rate. However, starvation of fermenting cells in a glucose medium for any essential macro- or micro-nutrient counteracts this effect, leading to downregulation of PKA and its targets concomitant with growth arrest and entrance into G0. Re-addition of the lacking nutrient triggers rapid activation of the PKA pathway, without involvement of cAMP as second messenger. Investigation of the sensing mechanism has revealed that the specific high-affinity nutrient transporter(s) induced during starvation function as transporter-receptors or transceptors for rapid activation of PKA upon re-addition of the missing substrate. In this way, transceptors have been identified for amino acids, ammonium, phosphate, sulfate, iron, and zinc. We propose a hypothesis for regulation of PKA activity by nutrient transceptors to serve as a conceptual framework for future experimentation. Many properties of transceptors appear to be similar to those of classical receptors and nutrient transceptors may constitute intermediate forms in the development of receptors from nutrient transporters during evolution. The nutrient-sensing transceptor system in yeast for activation of the PKA pathway has served as a paradigm for similar studies on candidate nutrient transceptors in other eukaryotes and we succinctly discuss the many examples of transceptors that have already been documented in other yeast species, filamentous fungi, plants, and animals, including the examples in human cells.

Increased plasma soluble human leukocyte antigen-G in persistent wheezy infants

BACKGROUND

Human leukocyte antigen (HLA)-G is a non-classical major histocompatibility complex class I antigen characterized by limited polymorphism in its coding region, unique tissue expression pattern in physiologic conditions and immunomodulatory properties. Recently, the level of soluble (s)HLA-G was found to be higher in atopic asthma and allergic rhinitis, but this remains to be clarified in wheezy infants. The aim of the present study was therefore to investigate sHLA-G in wheezy infants.

METHODS

The subjects consisted of infants with persistent wheezing and positive modified asthma predictive index (mAPI; n = 30; persistent group) and those with transient wheezing and negative mAPI (n = 17; transient group). sHLA-G was measured in plasma using enzyme-linked immunosorbent assay. Total immunoglobulin E (IgE) and eosinophil count were measured, and skin testing was performed with a battery of 13 antigens with appropriate positive and negative controls.

RESULTS

sHLA-G was significantly higher in the persistent wheezing (positive mAPI) group compared with the transient wheezing (negative mAPI) group (P = 0.008). There was no significant difference in peripheral blood eosinophil count and total IgE between the groups.

CONCLUSIONS

The increased sHLA-G in infants with persistent wheeze suggests that sHLA-G may be able to be used to distinguish persistent from transient wheeze. Further comprehensive studies are needed on this topic.

Diagnostic and Biological Significance of KIR Expression Profile Determined by RNA-Seq in Natural Killer/T-Cell Lymphoma

Natural killer/T-cell lymphoma (NKTCL) is a rare, aggressive form of non-Hodgkin lymphoma that is generally incurable at more advanced stages with systemic involvement. Clonal diagnostic markers (eg, unique T- or B-cell receptor rearrangements) are not available for NKTCLs. Killer cell immunoglobulin like receptors (KIRs) are a family of type I transmembrane glycoproteins involved in the inhibition or activation of NK cells. A restricted expression profile of KIRs has been proposed as clonal markers of NK-cell proliferations. Here we evaluated the transcription profile of all KIR family genes and C-type lectin receptor genes using RNA sequencing on NKTCL cases (n = 17) and NK-cell lines (n = 3). The expression of all KIRs tended to be markedly reduced or absent in NKTCL, except for the KIR family member killer Ig-like receptor 2DL4 (KIR2DL4; alias CD158D), which was selectively overexpressed in the majority (59%) of cases. No specific expression pattern was observed for C-type lectin receptors. KIR2DL4 is an unusual member of the KIR family that recognizes human leukocyte antigen G and mediates NK-cell activation through inducing proliferation and survival pathways such as AKT and NF-κB. Stable knockdown of KIR2DL4 in two malignant NK-cell lines with high KIR2DL4 expression significantly reduced cell growth. Selective overexpression of KIR2DL4 and down-regulation of inhibitory KIRs may contribute to NKTCL pathogenesis.

The evolution of natural killer cell receptors

Natural killer (NK) cells are immune cells that play a crucial role against viral infections and tumors. To be tolerant against healthy tissue and simultaneously attack infected cells, the activity of NK cells is tightly regulated by a sophisticated array of germline-encoded activating and inhibiting receptors. The best characterized mechanism of NK cell activation is “missing self” detection, i.e., the recognition of virally infected or transformed cells that reduce their MHC expression to evade cytotoxic T cells. To monitor the expression of MHC-I on target cells, NK cells have monomorphic inhibitory receptors which interact with conserved MHC molecules. However, there are other NK cell receptors (NKRs) encoded by gene families showing a remarkable genetic diversity. Thus, NKR haplotypes contain several genes encoding for receptors with activating and inhibiting signaling, and that vary in gene content and allelic polymorphism. But if missing-self detection can be achieved by a monomorphic NKR system why have these polygenic and polymorphic receptors evolved? Here, we review the expansion of NKR receptor families in different mammal species, and we discuss several hypotheses that possibly underlie the diversification of the NK cell receptor complex, including the evolution of viral decoys, peptide sensitivity, and selective MHC-downregulation.

The structure of the atypical killer cell immunoglobulin-like receptor, KIR2DL4

The engagement of natural killer cell immunoglobulin-like receptors (KIRs) with their target ligands, human leukocyte antigen (HLA) molecules, is a critical component of innate immunity. Structurally, KIRs typically have either two (D1-D2) or three (D0-D1-D2) extracellular immunoglobulin domains, with the D1 and D2 domain recognizing the α1 and α2 helices of HLA, respectively, whereas the D0 domain of the KIR3DLs binds a loop region flanking the α1 helix of the HLA molecule. KIR2DL4 is distinct from other KIRs (except KIR2DL5) in that it does not contain a D1 domain and instead has a D0-D2 arrangement. Functionally, KIR2DL4 is also atypical in that, unlike all other KIRs, KIR2DL4 has both activating and inhibitory signaling domains. Here, we determined the 2.8 Å crystal structure of the extracellular domains of KIR2DL4. Structurally, KIR2DL4 is reminiscent of other KIR2DL receptors, with the D0 and D2 adopting the C2-type immunoglobulin fold arranged with an acute elbow angle. However, KIR2DL4 self-associated via the D0 domain in a concentration-dependent manner and was observed as a tetramer in the crystal lattice by size exclusion chromatography, dynamic light scattering, analytical ultracentrifugation, and small angle x-ray scattering experiments. The assignment of residues in the D0 domain to forming the KIR2DL4 tetramer precludes an interaction with HLA akin to that observed for KIR3DL1. Accordingly, no interaction was observed to HLA by direct binding studies. Our data suggest that the unique functional properties of KIR2DL4 may be mediated by self-association of the receptor.

Genetic polymorphisms and expression of HLA-G and its receptors, KIR2DL4 and LILRB1, in non-small cell lung cancer

Human leukocyte antigen-G (HLA-G) is a nonclassical HLA class I molecule absent from most normal tissues but detected in many malignant tumors. It is recognized by cells of the immune system using LILRB1, KIR2DL4 and LILRB2 receptors. We attempted to find out whether some polymorphisms of HLA-G, LILRB1 and KIR2DL4 genes are associated with susceptibility to nonsmall cell lung cancer (NSCLC). Four polymorphisms in HLA-G, i.e. -964A>G (rs1632947), -725C>G>T (rs1233334), -716T>G (rs2249863) in the promoter, and a 14 base pair insertion/deletion (14 bp indel) in the 3'-untranslated region (3'UTR), and five in LILRB1 - 5651G>A (rs41308748) in intron 14, 5717C>T L622L (rs1061684), 5724G>A E625K (rs16985478), 5774 C>A P641P (rs41548213) in exon 15, and 5806C>T (rs8101240) in 3'UTR - as well as 9620 9A/10A (rs11410751) polymorphism in exon 7 of KIR2DL4 were typed using different laboratory techniques. Only one single nucleotide polymorphism (SNP) in HLA-G (-964A>G) and one in LILRB1 (5724G>A) were found to influence the risk of NSCLC. In addition, 5724G>A was associated with protection from tumor cell infiltration of regional lymph nodes. Most importantly, we detected HLA-G and LILRB1 expression in tumor specimens, but no correlation with genetic polymorphisms was observed. HLA-G and LILRB1 protein expression levels in tumor tissue were significantly correlated with tumor stage.

Genetic polymorphism of KIR2DL4 in the Polish population

The KIR2DL4 gene is characterized by alleles with either 9 or 10 consecutive adenines in exon 7, which encodes the transmembrane domain. The 9A variant produces either a protein with a truncated cytoplasmic tail or one lacking the transmembrane region. This causes a lack of KIR2DL4 expression. In contrast, 10A alleles encode receptors that may be expressed at the cell surface. We tested 438 healthy individuals for polymorphism of the KIR2DL4 gene. KIR2DL4 9A/10A alleles were distinguished by the high resolution melting (HRM) method, and restriction fragment length polymorphism (RFLP) was used for genotyping of three other single nucleotide polymorphisms (SNPs) spanning the near vicinity of the poly-adenine fragment. We found a weak difference between males and females in 9769 C/A genotypes and alleles. In addition, we observed complete linkage disequilibrium (LD) between 9A insertion/deletion in the 9620 position and the 9571T/C position of the gene (r(2)  = 1) both in females and males and almost complete LD with the 9797G/A position (r(2)  = 0.963 for females and r(2)  = 0.892 for males). Most importantly, we detected, in a group of fertile women, a high frequency (30.2%) of homozygosity for the defective 9A variant, which suggests that KIR2DL4 as a functional cell surface receptor is not absolutely necessary for reproduction. On the other hand, lower representation of 10A/10A homozygotes and high frequency of 10A/9A heterozygotes indicates a need for both cell membrane-anchored and soluble KIR2DL4 molecules. Finally, cost-reducing RFLP instead of HRM is proposed for typing 9A and 10A variants.

Endosomal trafficking and signaling in plant defense responses

Plant defense responses are initiated by ligand-receptor recognition. The receptor may contain a motif for endocytosis and endocytosis is important for defense signaling in some cases. Recently, endosomal trafficking during defense has begun to be elucidated. In some cases, defense receptors are internalized into early endosomes, recycled back to the plasma membrane (PM) on recycling endosomes, and targeted for degradation via the late endosome pathway in an ESCRT dependent manner. Endosomal signaling has been proposed for several receptors. Defense receptors have been shown to reside on endosomes during the signaling time window. Increasing the endosomal presence of a receptor can cause a concomitant increase in signaling, while abolishing the formation of endosomes after the receptor has already been internalized can cause signaling attenuation.

HLA-G-mediated NK cell senescence promotes vascular remodeling: implications for reproduction

The uterus in early pregnancy is a non-lymphoid organ that is enriched in natural killer (NK) cells. Studies to address the role of these abundant human NK cells at the maternal/fetal interface have focused on their response to the major histocompatibility complex (MHC) molecules on fetal trophoblast cells that they contact. The interaction of maternal NK cell receptors belonging to the killer cell immunoglobulin-like receptor (KIR) family with trophoblast MHC class I molecules in pregnancy can regulate NK cell activation for secretion of pro-angiogenic factors that promote placental development. This review will cover the role of KIR at the maternal/fetal interface and focus on KIR2DL4, a KIR family member that is uniquely poised to play a role in pregnancy due to the restricted expression of its ligand, human leukocyte antigen (HLA)-G, by fetal trophoblast cells early in pregnancy. The pathways by which KIR2DL4-HLA-G interactions induce the cellular senescence of NK cells and the role of the resulting senescence-associated secretory phenotype (SASP) in vascular remodeling will be discussed in the context of reproduction.

TNFR-associated factor 6 and TGF-β-activated kinase 1 control signals for a senescence response by an endosomal NK cell receptor

The endosomal innate receptor CD158d (killer cell Ig-like receptor 2DL4) induces cellular senescence in human NK cells in response to soluble ligand (HLA-G or agonist Ab). These senescent NK cells display a senescence-associated secretory phenotype, and their secretome promotes vascular remodeling and angiogenesis. To understand how CD158d initiates signaling for a senescence response, we mapped the region in its cytoplasmic tail that controls signaling. We identified a conserved TNFR-associated factor 6 (TRAF6) binding motif, which was required for CD158d-induced NF-κB activation and IL-8 secretion, TRAF6 association with CD158d, and TRAF6 recruitment to CD158d(+) endosomes in transfected cells. The adaptor TRAF6 is known to couple proximal signals from receptors such as endosomal TLRs and CD40 through the kinase TGF-β-activated kinase 1 (TAK1) for NF-κB-dependent proinflammatory responses. Small interfering RNA-mediated silencing of TRAF6 and TAK1, and inhibition of TAK1 blocked CD158d-dependent IL-8 secretion. Stimulation of primary, resting NK cells with soluble Ab to CD158d induced TRAF6 association with CD158d, induced TAK1 phosphorylation, and inhibition of TAK1 blocked the CD158d-dependent reprogramming of NK cells that produces the senescence-associated secretory phenotype signature. Our results reveal that a prototypic TLR and TNFR signaling pathway is used by a killer cell Ig-like receptor that promotes secretion of proinflammatory and proangiogenic mediators as part of a unique senescence phenotype in NK cells.

Genome-wide siRNA screen reveals a new cellular partner of NK cell receptor KIR2DL4: heparan sulfate directly modulates KIR2DL4-mediated responses

KIR2DL4 (CD158d) is a distinct member of the killer cell Ig-like receptor (KIR) family in human NK cells that can induce cytokine production and cytolytic activity in resting NK cells. Soluble HLA-G, normally expressed only by fetal-derived trophoblast cells, was reported to be a ligand for KIR2DL4; however, KIR2DL4 expression is not restricted to the placenta and can be found in CD56(high) subset of peripheral blood NK cells. We demonstrated that KIR2DL4 can interact with alternative ligand(s), expressed by cells of epithelial or fibroblast origin. A genome-wide high-throughput siRNA screen revealed that KIR2DL4 recognition of cell-surface ligand(s) is directly regulated by heparan sulfate (HS) glucosamine 3-O-sulfotransferase 3B1 (HS3ST3B1). KIR2DL4 was found to directly interact with HS/heparin, and the D0 domain of KIR2DL4 was essential for this interaction. Accordingly, exogenous HS/heparin can regulate cytokine production by KIR2DL4-expressing NK cells and HEK293T cells (HEK293T-2DL4), and induces differential localization of KIR2DL4 to rab5(+) and rab7(+) endosomes, thus leading to downregulation of cytokine production and degradation of the receptor. Furthermore, we showed that intimate interaction of syndecan-4 (SDC4) HS proteoglycan (HSPG) and KIR2DL4 directly affects receptor endocytosis and membrane trafficking.

The janus head of T cell aging - autoimmunity and immunodeficiency

Immune aging is best known for its immune defects that increase susceptibility to infections and reduce adaptive immune responses to vaccination. In parallel, the aged immune system is prone to autoimmune responses and many autoimmune diseases increase in incidence with age or are even preferentially encountered in the elderly. Why an immune system that suboptimally responds to exogenous antigen fails to maintain tolerance to self-antigens appears to be perplexing. In this review, we will discuss age-associated deviations in the immune repertoire and the regulation of signaling pathways that may shed light on this conundrum.

Variable NK cell receptors and their MHC class I ligands in immunity, reproduction and human evolution

Natural killer (NK) cells have roles in immunity and reproduction that are controlled by variable receptors that recognize MHC class I molecules. The variable NK cell receptors found in humans are specific to simian primates, in which they have progressively co-evolved with MHC class I molecules. The emergence of the MHC-C gene in hominids drove the evolution of a system of NK cell receptors for MHC-C molecules that is most elaborate in chimpanzees. By contrast, the human system of MHC-C receptors seems to have been subject to different selection pressures that have acted in competition on the immunological and reproductive functions of MHC class I molecules. We suggest that this compromise facilitated the development of the bigger brains that enabled archaic and modern humans to migrate out of Africa and populate other continents.

Controlling natural killer cell responses: integration of signals for activation and inhibition

Understanding how signals are integrated to control natural killer (NK) cell responsiveness in the absence of antigen-specific receptors has been a challenge, but recent work has revealed some underlying principles that govern NK cell responses. NK cells use an array of innate receptors to sense their environment and respond to alterations caused by infections, cellular stress, and transformation. No single activation receptor dominates; instead, synergistic signals from combinations of receptors are integrated to activate natural cytotoxicity and cytokine production. Inhibitory receptors for major histocompatibility complex class I (MHC-I) have a critical role in controlling NK cell responses and, paradoxically, in maintaining NK cells in a state of responsiveness to subsequent activation events, a process referred to as licensing. MHC-I-specific inhibitory receptors both block activation signals and trigger signals to phosphorylate and inactivate the small adaptor Crk. These different facets of inhibitory signaling are incorporated into a revocable license model for the reversible tuning of NK cell responsiveness.

Human leukocyte antigen-G is frequently expressed in glioblastoma and may be induced in vitro by combined 5-aza-2'-deoxycytidine and interferon-γ treatments: results from a multicentric study

Human leukocyte antigen-G (HLA-G) is a nonclassical major histocompatibility complex (MHC) class I molecule involved in immune tolerance processes, playing an important role in the maintenance of the semi-allogeneic fetus. Although HLA-G expression is restricted in normal tissues, it is broadly expressed in malignant tumors and may favor tumor immune escape. We analyzed HLA-G protein and mRNA expression in tumor samples from patients with glioblastoma collected in France, Denmark, and Brazil. We found HLA-G protein expression in 65 of 108 samples and mRNA in 20 of 21 samples. The absence of HLA-G protein expression was associated with a better long-term survival rate. The mechanisms underlying HLA-G gene expression were investigated in glioma cell lines U251MG, D247MG, and U138MG. Induction of HLA-G transcriptional activity was dependent of 5-aza-2'-deoxycytidine treatment and enhanced by interferon-γ. HLA-G protein expression was observed in U251MG cells only. These cells exhibited a permissive chromatin state at the HLA-G gene promoter and the highest levels of induced HLA-G transcriptional activity following 5-aza-2'-deoxycytidine treatment. Several antigen-presenting machinery components were up-regulated in U251MG cells after demethylating and IFN-γ treatments, suggesting an effect on the up-regulation of HLA-G cell surface expression. Therefore, because of its role in tumor tolerance, HLA-G found to be expressed in glioblastoma samples should be taken into consideration in clinical studies on the pathology and in the design of therapeutic strategies to prevent its expression in HLA-G-negative tumors.

Cellular senescence induced by CD158d reprograms natural killer cells to promote vascular remodeling

Natural killer (NK) cells, which have an essential role in immune defense, also contribute to reproductive success. NK cells are abundant at the maternal-fetal interface, where soluble HLA-G is produced by fetal trophoblast cells during early pregnancy. Soluble HLA-G induces a proinflammatory response in primary, resting NK cells on endocytosis into early endosomes where its receptor, CD158d, resides. CD158d initiates signaling through DNA-PKcs, Akt, and NF-κB for a proinflammatory and proangiogenic response. The physiological relevance of this endosomal signaling pathway, and how activation of CD158d through soluble ligands regulates NK cell fate and function is unknown. We show here that CD158d agonists trigger a DNA damage response signaling pathway involving cyclin-dependent kinase inhibitor p21 expression and heterochromatin protein HP1-γ phosphorylation. Sustained activation through CD158d induced morphological changes in NK cell shape and size, and survival in the absence of cell-cycle entry, all hallmarks of senescence, and a transcriptional signature of a senescence-associated secretory phenotype (SASP). SASP is a program that can be induced by oncogenes or DNA damage, and promotes growth arrest and tissue repair. The secretome of CD158d-stimulated senescent NK cells promoted vascular remodeling and angiogenesis as assessed by functional readouts of vascular permeability and endothelial cell tube formation. Retrospective analysis of the decidual NK cell transcriptome revealed a strong senescence signature. We propose that a positive function of senescence in healthy tissue is to favor reproduction through the sustained activation of NK cells to remodel maternal vasculature in early pregnancy.

KIR2DL5: An Orphan Inhibitory Receptor Displaying Complex Patterns of Polymorphism and Expression

A recently developed anti-KIR2DL5 (CD158f) antibody has demonstrated KIR2DL5 expression on the surface of NK and T lymphocytes, making it the last functional KIR identified in the human genome. KIR2DL5 belongs to an ancestral lineage of KIR with Ig-like domains of the D0-D2 type, of which KIR2DL4, an HLA-G receptor, is the only other human member. Despite KIR2DL4 and KIR2DL5 being encoded by genes with similar domain usage, several KIR2DL5 functions resemble more closely those of KIR recognizing classical HLA class I molecules - surface-expressed KIR2DL5 inhibits NK cells through the SHP-2 phosphatase and displays a clonal distribution on NK and T lymphocytes. No activating homolog of KIR2DL5 has been described in any species. The genetics of KIR2DL5 is complicated by duplication of its gene in an ancestor of modern humans living ∼1.7 million years ago. Both KIR2DL5 paralogs have undergone allelic diversification; the centromeric gene is most often represented by alleles whose expression is silenced epigenetically through DNA methylation, thus providing a natural system to investigate the regulation of KIR transcription. The role of KIR2DL5 in immunity is not completely understood, in spite of different attempts to define its ligand. Here we revisit the most relevant characteristics of KIR2DL5, an NK-cell receptor possessing a unique combination of genetic, structural, and functional features.

KIR2DL4 (CD158d): An activation receptor for HLA-G

KIR2DL4 is an unusual killer cell immunoglobulin-like receptor (KIR) family member in terms of its structure, expression, cellular localization, and signaling properties. The most conserved KIR in evolution, it is referred to as a framework KIR gene and is expressed by all natural killer (NK) cells and a subset of T cells. Although it has a long cytoplasmic tail that is typical of inhibitory KIR, engagement of this receptor results in the activation of NK cells, not for cytotoxicity, but for cytokine and chemokine secretion. Unlike all other KIRs, which are expressed on the surface of NK cells, KIR2DL4 resides in endosomes. It signals from this intracellular site for a proinflammatory and proangiogenic response, using a novel endosomal signaling pathway that involves the serine/threonine kinases DNA-PKcs and Akt. The only known ligand of KIR2DL4 is HLA-G. Soluble HLA-G accumulates in KIR2DL4⁺ endosomes. Unlike classical HLA molecules that serve as ligands for other KIR family members, in healthy individuals, HLA-G expression is restricted to the fetal trophoblast cells that invade the maternal decidua during early pregnancy. Since NK cells constitute the predominant lymphocyte subset at this site, the proinflammatory/proangiogenic outcome of the interaction between KIR2DL4 and soluble HLA-G supports a role for KIR2DL4 in the extensive remodeling of the maternal vasculature during the early weeks of pregnancy.

Charge injection in solution-processed organic field-effect transistors: physics, models and characterization methods

A high-mobility organic semiconductor employed as the active material in a field-effect transistor does not guarantee per se that expectations of high performance are fulfilled. This is even truer if a downscaled, short channel is adopted. Only if contacts are able to provide the device with as much charge as it needs, with a negligible voltage drop across them, then high expectations can turn into high performances. It is a fact that this is not always the case in the field of organic electronics. In this review, we aim to offer a comprehensive overview on the subject of current injection in organic thin film transistors: physical principles concerning energy level (mis)alignment at interfaces, models describing charge injection, technologies for interface tuning, and techniques for characterizing devices. Finally, a survey of the most recent accomplishments in the field is given. Principles are described in general, but the technologies and survey emphasis is on solution processed transistors, because it is our opinion that scalable, roll-to-roll printing processing is one, if not the brightest, possible scenario for the future of organic electronics. With the exception of electrolyte-gated organic transistors, where impressively low width normalized resistances were reported (in the range of 10 Ω·cm), to date the lowest values reported for devices where the semiconductor is solution-processed and where the most common architectures are adopted, are ∼10 kΩ·cm for transistors with a field effect mobility in the 0.1-1 cm(2)/Vs range. Although these values represent the best case, they still pose a severe limitation for downscaling the channel lengths below a few micrometers, necessary for increasing the device switching speed. Moreover, techniques to lower contact resistances have been often developed on a case-by-case basis, depending on the materials, architecture and processing techniques. The lack of a standard strategy has hampered the progress of the field for a long time. Only recently, as the understanding of the rather complex physical processes at the metal/semiconductor interfaces has improved, more general approaches, with a validity that extends to several materials, are being proposed and successfully tested in the literature. Only a combined scientific and technological effort, on the one side to fully understand contact phenomena and on the other to completely master the tailoring of interfaces, will enable the development of advanced organic electronics applications and their widespread adoption in low-cost, large-area printed circuits.

Peptides induce persistent signaling from endosomes by a nutrient transceptor

The yeast Gap1 transceptor mediates amino acid activation of the protein kinase A pathway and undergoes endocytic internalization following amino acid transport. We identified three specific γ-glutamyl dipeptides that cause persistent cyclic AMP-independent activation of protein kinase A, prevent Gap1 vacuolar sorting and cause Gap1 accumulation in endosomes. To our knowledge, these are the first examples of persistent agonists of a transceptor. In yeast mutants blocked in multivesicular body sorting, L-citrulline mimicked persistent signaling, further supporting that the internalized Gap1 transceptor keeps signaling. Unexpectedly, these dipeptides were transported by Gap1 and not by the regular dipeptide transporters. Their uptake was unusually sensitive to external pH and caused transient intracellular acidification. High external pH, NHA1 deletion or V-ATPase inhibition overcame the vacuolar sorting defect. Hence, this work has identified specific dipeptides that cause enhanced proton influx through the Gap1 symporter, resulting in its defective vacuolar sorting, and independently transform it into a persistently signaling transceptor.

Endosomal signaling of the tomato leucine-rich repeat receptor-like protein LeEix2

Extracellular leucine-rich repeat (LRR) receptor-like proteins (RLPs) represent a unique class of cell-surface receptors, as they lack a functional cytoplasmic domain. Our knowledge of how RLPs that do not contain a kinase or Toll domain function is very limited. The tomato RLP receptor LeEix2 signals to induce defense responses mediated by the fungal protein ethylene-inducing xylanase (EIX). The movement of FYVE-positive endosomes before and after EIX application was examined using spinning disc confocal microscopy. We found that while FYVE-positive endosomes generally observe a random movement pattern, following EIX application a subpopulation of FYVE-positive endosomes follow a directional movement pattern. Further, cellular endosomes travel greater distances at higher speeds following EIX application. Time-course experiments conducted with specific inhibitors demonstrate the involvement of endosomal signaling in EIX-triggered defense responses. Abolishing the existence of endosomes or the endocytic event prevented EIX-induced signaling. Endocytosis/endosome inhibitors, such as Dynasore or 1-butanol, inhibit EIX-induced signaling. Moreover, treatment with Endosidin1, which inhibits an early step in plasma membrane/endosome trafficking, enhances the induction of defense responses by EIX. Our data indicate a distinct endosomal signaling mechanism for induction of defense responses in this RLP system.

From transporter to transceptor: signaling from transporters provokes re-evaluation of complex trafficking and regulatory controls: endocytic internalization and intracellular trafficking of nutrient transceptors may, at least in part, be governed by their signaling function

When cells are starved of their substrate, many nutrient transporters are induced. These undergo rapid endocytosis and redirection of their intracellular trafficking when their substrate becomes available again. The discovery that some of these transporters also act as receptors, or transceptors, suggests that at least part of the sophisticated controls governing the trafficking of these proteins has to do with their signaling function rather than with control of transport. In yeast, the general amino acid permease Gap1 mediates signaling to the protein kinase A pathway. Its endocytic internalization and intracellular trafficking are subject to amino acid control. Other nutrient transceptors controlling this signal transduction pathway appear to be subject to similar trafficking regulation. Transporters with complex regulatory control have also been suggested to function as transceptors in other organisms. Hence, precise regulation of intracellular trafficking in nutrient transporters may be related to the need for tight control of nutrient-induced signaling.