A peptidoglycan recognition protein in innate immunity conserved from insects to humans

Mechanisms of Action of the PGLYRP1/Tag7 Protein in Innate and Acquired Immunity

One of the promising fields of modern molecular biology is the search for new proteins that regulate the various stages of the immune response and the investigation of the molecular mechanisms of action of these proteins. Such proteins include the multifunctional protein PGLYRP1/Tag7, belonging to the PGRP-S protein family, whose gene was discovered in mice at the Institute of Gene Biology, Russian Academy of Sciences, in 1996. PGLYRP1/Tag7 is classified as a protein of innate immunity; however, it can also participate in the regulation of acquired immunity mechanisms. In this paper, we consider the involvement of PGLYRP1/Tag7 in the triggering of antimicrobial defense mechanisms and formation of subsets of cytotoxic lymphocytes that kill tumor cells. The paper emphasizes that the multifaceted functional activity of Tag7 in the immune response has to do with its ability to interact with various proteins to form stable protein complexes. Hsp70-associated Tag7 can induce the death of tumor cells carrying the TNFR1 receptor. Tag7, associated with the Mts1 (S100A4) protein, can stimulate the migration of innate and adaptive immune cytotoxic lymphocytes to a lesion site. Involvement of Tag7 in the regulation of immunological processes suggests that it may be considered as a promising agent in cancer therapy. These properties of Tag7 were used to develop autologous vaccines that have passed the first and second phases of clinical trials in patients with end-stage melanoma and renal cancer. The C-terminal peptide of Tag7, isolated by limited proteolysis, was shown to protect the cartilage and bone tissue of the ankle joint in mice with induced autoimmune arthritis and may be a promising drug for suppressing the development of inflammatory processes.

Rhodnius prolixus uses the peptidoglycan recognition receptor rpPGRP-LC/LA to detect Gram-negative bacteria and activate the IMD pathway

Insects rely on an innate immune system to recognize and eliminate pathogens. Key components of this system are highly conserved across all invertebrates. To detect pathogens, insects use Pattern recognition receptors (PRRs) that bind to signature motifs on the surface of pathogens called Pathogen Associated Molecular Patterns (PAMPs). In general, insects use peptidoglycan recognition proteins (PGRPs) in the Immune Deficiency (IMD) pathway to detect Gram-negative bacteria, and other PGRPs and Gram-negative binding proteins (GNBPs) in the Toll pathway to detect Gram-positive bacteria and fungi, although there is crosstalk and cooperation between these and other pathways. Once pathogens are recognized, these pathways activate the production of potent antimicrobial peptides (AMPs). Most PRRs in insects have been reported from genome sequencing initiatives but few have been characterized functionally. The initial studies on insect PRRs were done using established dipteran model organisms such as Drosophila melanogaster, but there are differences in the numbers and functional role of PRRs in different insects. Here we describe the genomic repertoire of PGRPs in Rhodnius prolixus, a hemimetabolous hemipteran vector of the parasite Trypanosoma cruzi that causes Chagas disease in humans. Using a de novo transcriptome from the fat body of immune activated insects, we found 5 genes encoding PGRPs. Phylogenetic analysis groups R. prolixus PGRPs with D. melanogaster PGRP-LA, which is involved in the IMD pathway in the respiratory tract. A single R. prolixus PGRP gene encodes isoforms that contain an intracellular region or motif (cryptic RIP Homotypic Interaction Motif-cRHIM) that is involved in the IMD signaling pathway in D. melanogaster. We characterized and silenced this gene using RNAi and show that the PGRPs that contain cRHIMs are involved in the recognition of Gram-negative bacteria, and activation of the IMD pathway in the fat body of R. prolixus, similar to the PGRP-LC of D. melanogaster. This is the first functional characterization of a PGRP containing a cRHIM motif that serves to activate the IMD pathway in a hemimetabolous insect.

Cytokines TNFα, IFNγ and IL-2 Are Responsible for Signal Transmission from the Innate Immunity Protein Tag7 (PGLYRP1) to Cytotoxic Effector Lymphocytes

Studies on the mechanisms of activation of cytotoxic lymphocyte subpopulations are an important research direction in modern immunology. This study provides a detailed analysis of the effect of Tag7 (PGRP-S, PGLYRP1) on the development of lymphocyte subpopulations cytotoxic against MHC-negative tumor cells in a pool of peripheral blood mononuclear cells (PBMCs). The results show that Tag7 can bind to the TREM-1 receptor on the surfaces of monocytes, thereby triggering the expression of mRNA TNFα and IFNγ. The appearance of these cytokines in conditioned medium leads to IL-2 cytokine secretion by CD3⁺CD4⁺ lymphocytes. In turn, IL-2 facilitates unspecific activation of three cytotoxic cell subpopulations in the PBMC pool: NK (CD16⁺CD56⁺), CD3⁺CD4⁺ and CD3⁺CD8⁺. These subpopulations appear after a certain period of incubation with Tag7 and show toxicity against tumor cells.

Gene identification and functional analysis of peptidoglycan recognition protein from the spotted sea bass (Lateolabrax maculatus)

Peptidoglycan recognition proteins (PGRPs), which are structurally conserved innate immune molecules in invertebrate and vertebrate animals, play the important roles in regulation of innate immune responses. In this paper, three PGRP genes of spotted sea bass, Lateolabrax maculatus, were cloned, designated as Ssb-PGRP2, Ssb-PGRP-L2 and Ssb-PGRP-SC2, respectively. Sequence analysis showed that the deduced amino acid sequences of Ssb-PGRP2, Ssb-PGRP-L2 and Ssb-PGRP-SC2 proteins contained respectively 468, 482 and 167 amino acid residues, and had the typical structural features of PGRPs, i.e. conserved PGRP domain and Zn²⁺ binding domain including four specific amino acid residues which were required for amidase activity. q-PCR analysis of total mRNA showed that the mRNA expression of three PGRP genes were detected in all the examined tissues and the expression patterns of Ssb-PGRP2, Ssb-PGRP-L2 and Ssb-PGRP-SC2 were different. After injected with LPS, Poly (I:C) and Edwardsiella tarda, there was a clear time-dependent expression pattern for each of the three PGRP genes in head kidney, spleen, intestine and gill of the spotted sea bass. In our study, three recombinant proteins corresponding to the three members of the peptidoglycan recognition protein family were expressed and purified. Moreover, all of the three recombinant PGRP proteins significantly inhibited bacterial survival and growth, and expressed bactericidal effects on Vibrio harveyi, Staphylococcus aureus and Edwardsiella tarda. In particular, it was firstly verified that their antimicrobial activity presented the superimposed effect. Overall, these findings indicated that three PGRP genes of spotted sea bass were at least involved in host defense against bacterial infections.

Peptidoglycan derived from Lactobacillus rhamnosus MLGA up-regulates the expression of chicken -defensin 9 without triggering an inflammatory response

Defensins are critical components of the innate immune system and play an important role in the integration of innate and adaptive immune responses. Although information on the immunomodulatory properties of peptidoglycan from bacteria is abundant, little is known about the β-defensin induction effect of peptidoglycan from the probiotic Lactobacillus. This study investigated the effect of intact peptidoglycan from L. rhamnosus MLGA on the induction of avian β-defensin 9 in chicken immune cells and intestinal explants. Peptidoglycan from Lactobacillus rhamnosus MLGA dose dependently promoted avian β-defensin 9 mRNA expression in chicken PBMCs, splenocytes, thymocytes, hepatocytes, and chicken embryo jejunum, ileum, and cecum explants and increased the capacity of PBMC or splenocyte lysates to inhibit the growth of Salmonella Enteritidis. In contrast to the effect of L. rhamnosus MLGA-derived peptidoglycan, peptidoglycan derived from pathogenic Staphylococcus aureus reduced avian β-defensin 9 mRNA expression in chicken PBMCs and splenocytes. The inducible effect of peptidoglycan from L. rhamnosus MLGA on avian β-defensin 9 expression in PBMCs and splenocytes was observed without activation of the expression of associated pro-inflammatory cytokines IL-1β, IL-8, and IL-12p40, whereas these cytokine expressions were suppressed by peptidoglycan hydrolysate obtained by lysozyme digestion. The results of the present study show the capability of peptidoglycan derived from L. rhamnosus MLGA to induce the antimicrobial peptide defensin while simultaneously avoiding the deleterious risks of an inflammatory response.

Pattern recognition receptors from lepidopteran insects and their biological functions

Lepidopteran insects have potent innate immunity to fight against the invading pathogens. As the initiation step, pattern recognition receptors (PRRs) recognize and bind microbial surface configurations known as pathogen-associated molecular patterns (PAMPs). Aftermath, they initiate both cellular and humoral immune responses, including phagocytosis, agglutination, nodulation, encapsulation, prophenoloxidase activation, and synthesis of antimicrobial peptides. In this review, we summarize the recent findings concerning PRRs in lepidoptaeran insects, mostly agriculture pests including Helicoverpa armigera, Plutella xylostella, and Spodoptera exigua. We mainly focus on the function and phylogeny of C-type lectins (CTLs), peptidoglycan recognition proteins (PGRPs), β-1,3-glucan recognition proteins (βGRPs), and galectins (GALEs). It enriches our understanding of the immune system of lepidopteran insects and provides directions in the future research.

Activity of mammalian peptidoglycan-targeting immunity against Pseudomonas aeruginosa

Pseudomonas aeruginosa is one of the most important opportunistic pathogens, whose clinical relevance is not only due to the high morbidity/mortality of the infections caused, but also to its striking capacity for antibiotic resistance development. In the current scenario of a shortage of effective antipseudomonal drugs, it is essential to have thorough knowledge of the pathogen's biology from all sides, so as to find weak points for drug development. Obviously, one of these points could be the peptidoglycan, given its essential role for cell viability. Meanwhile, immune weapons targeting this structure could constitute an excellent model to be taken advantage of in order to design new therapeutic strategies. In this context, this review gathers all the information regarding the activity of mammalian peptidoglycan-targeting innate immunity (namely lysozyme and peptidoglycan recognition proteins), specifically against P. aeruginosa. All the published studies were considered, from both in vitro and in vivo fields, including works that envisage these weapons as options not only to potentiate their innate effects within the host or for use as exogenously administered treatments, but also harnessing their inflammatory and immune regulatory capacity to finally reduce damage in the patient. Altogether, this review has the objective of anticipating and discussing whether these innate immune resources, in combination or not with other drugs attacking certain P. aeruginosa targets leading to its increased sensitization, could be valid therapeutic antipseudomonal allies.

Tenebrio molitor PGRP-LE Plays a Critical Role in Gut Antimicrobial Peptide Production in Response to Escherichia coli

Invading pathogens are recognized by peptidoglycan recognition proteins (PGRPs) that induce translocation of NF-κB transcription proteins and expression of robust antimicrobial peptides (AMPs). Tenebrio molitor PGRP-LE (TmPGRP-LE) has been previously identified as a key sensor of Listeria monocytogenes infection. Here, we present that TmPGRP-LE is highly expressed in the gut of T. molitor larvae and 5-day-old adults in the absence of microbial infection. In response to Escherichia coli and Candida albicans infections, TmPGRP-LE mRNA levels are significantly upregulated in both the fat body and gut. Silencing of TmPGRP-LE by RNAi rendered T. molitor significantly more susceptible to challenge by E. coli infection and, to a lesser extent, Staphylococcus aureus and C. albicans infections. Reduction of TmPGRP-LE levels in the larval gut resulted in downregulation of eight AMP genes following exposure to E. coli, S. aureus, and C. albicans. However, the transcriptional levels of AMPs more rapidly reached a higher level in the dsEGFP-treated larval gut after challenge with E. coli, which may suggest that AMPs induction were more sensitive to E. coli than S. aureus and C. albicans. In addition, TmPGRP-LE RNAi following E. coli and C. albicans challenges had notable effects on TmRelish, TmDorsal X1 isoform (TmDorX1), and TmDorX2 expression level in the fat body and gut. Taken together, TmPGRP-LE acts as an important gut microbial sensor that induces AMPs via Imd activation in response to E. coli, whereas involvement of TmPGRP-LE in AMPs synthesize is barely perceptible in the hemocytes and fat body.

Identification and characterization of a novel short-type peptidoglycan recognition protein in Apostichopus japonicus

Peptidoglycan recognition proteins (PGRPs) are pattern recognition molecules of the innate immune system via specific recognizing peptidoglycan, a unique component of bacterial cell wall. In the present study, a homologous gene encoding PGRP-S was identified and characterized from Apostichopus japonicus and designated as AjPGRP-S. The open reading frame of AjPGRP-S is 756 bp encoding a polypeptide of 251 amino acids (aa) with a signal peptide (1-24 aa) and a typical PGRP domain (37-178 aa). Phylogenetic analysis and sequence alignment revealed that AjPGRP-S is a member of the PGRP-S family. In healthy sea cucumbers, AjPGRP-S was expressed in all examined tissues with the highest distribution in body wall, muscle, and intestine. In Vibrio splendidus-infected sea cucumbers, AjPGRP-S was remarkably induced in coelomocytes. The recombinant AjPGRP-S (rAjPGRP-S) was shown to possess the highly amidase activity in the presence of Zn²⁺. Moreover, rAjPGRP-S exhibited agglutination abilities and strong bacteriostatic activities against V. splendidus, V. harveyi, V. parahaemolyticus, Staphylococcus aureus, and Micrococcus luteus. Furthermore, the agglutination ability can be enhanced in the presence of Zn²⁺. In conclusion, our results suggested that AjPGRP-S serves as a pattern recognition molecule involved in the immune response towards various pathogenic infections.

TmPGRP-SA regulates Antimicrobial Response to Bacteria and Fungi in the Fat Body and Gut of Tenebrio molitor

Antimicrobial immune response is mediated by a signal-transducing sensor, peptidoglycan recognition protein-SA (PGRP-SA), that can recognize non-self molecules. Although several studies have focused on the involvement of Drosophila PGRP-SA in antimicrobial peptide (AMP) expression in response to infections, studies on its role in Tenebrio molitor are lacking. Here, we present a functional analysis of T. molitor PGRP-SA (TmPGRP-SA). In the absence of microbes, TmPGRP-SA was highly expressed in the late-larval fat body, followed by hemocytes, and gut. Interestingly, following Escherichia coli, Staphylococcus aureus, and Candida albicans infections, the mRNA level of TmPGRP-SA was significantly upregulated in both the fat body and gut. TmPGRP-SA silencing had a significant effect on the mortality rates for all the microbes tested. Moreover, TmPGRP-SA is required for regulating the expression of eight AMP genes namely TmTenecin-1, -2, and -4; TmDefensin-1 and -2; TmColeoptericin-1; and TmAttacin-1b and -2 in the fat body in response to E. coli and S. aureus infections. TmPGRP-SA is essential for the transcription of TmTenecin-2, -4; TmDefensin-2; TmColeoptericin-1, -2; and TmAttacin-1a, -1b, and -2 in the gut upon E. coli and C. albicans infections. However, TmPGRP-SA does not regulate AMP expression in the hemocytes. Additionally, TmDorsal isoform X2, a downstream Toll transcription factor, was downregulated in TmPGRP-SA-silenced larval fat body following E. coli and S. aureus challenges, and in the gut following E. coli and C. albicans challenges.

Role of Glia in the Regulation of Sleep in Health and Disease

Sleep is a naturally occurring physiological state that is required to sustain physical and mental health. Traditionally viewed as strictly regulated by top-down control mechanisms, sleep is now known to also originate locally. Glial cells are emerging as important contributors to the regulation of sleep-wake cycles, locally and among dedicated neural circuits. A few pioneering studies revealed that astrocytes and microglia may influence sleep pressure, duration as well as intensity, but the precise involvement of these two glial cells in the regulation of sleep remains to be fully addressed, across contexts of health and disease. In this overview article, we will first summarize the literature pertaining to the role of astrocytes and microglia in the regulation of sleep under normal physiological conditions. Afterward, we will discuss the beneficial and deleterious consequences of glia-mediated neuroinflammation, whether it is acute, or chronic and associated with brain diseases, on the regulation of sleep. Sleep disturbances are a main comorbidity in neurodegenerative diseases, and in several brain diseases that include pain, epilepsy, and cancer. Identifying the relationships between glia-mediated neuroinflammation, sleep-wake rhythm disruption and brain diseases may have important implications for the treatment of several disorders. © 2020 American Physiological Society. Compr Physiol 10:687-712, 2020.

A 12-mer Peptide of Tag7 (PGLYRP1) Forms a Cytotoxic Complex with Hsp70 and Inhibits TNF-Alpha Induced Cell Death

Investigation of interactions between a pro-inflammatory cytokine tumor necrosis factor (TNFα) and its receptor is required for the development of new treatments for autoimmune diseases associated with the adverse effects of TNFα. Earlier, we demonstrated that the innate immunity protein Tag7 (PGRP-S, PGLYRP1) can interact with the TNFα receptor, TNFR1, and block the transduction of apoptotic signals through this receptor. A complex formed between the Tag7 protein and the major heat shock protein Hsp70 can activate TNFR1 receptor and induce tumor cell death via either apoptotic or necroptotic pathway. In this study, we show that a 12-mer peptide, designated 17.1, which was derived from the Tag7 protein, can be regarded as a novel TNFα inhibitor, also is able to form a cytotoxic complex with the heat shock protein Hsp70. This finding demonstrates a new role for Hsp70 protein in the immune response. Also, this new inhibitory 17.1 peptide demonstrates an anti-inflammatory activity in the complete Freund's adjuvant (CFA)-induced autoimmune arthritis model in laboratory mice. It appears that the 17.1 peptide could potentially be used as an anti-inflammatory agent.

An immune-responsive PGRP-S1 regulates the expression of antibacterial peptide genes in diamondback moth, Plutella xylostella (L.)

Peptidoglycan recognition proteins (PGRPs) are family of pattern recognition receptors (PRRs) and triggers the innate immune system (IIS) against the microbial infection. Although PGRPs have been intensively studied in model insects, they remain uncharacterized in most of the non-model insects. Here, we cloned and characterized a full-length cDNA of PGRP, from P. xylostella (PxPGRP-S1), which encodes a protein of 239 amino acids with PGRP domain, Ami2 domain and transmembrane region. The phylogenetic analysis revealed that the PxPGRP-S1 was closely related to the unigene of Plutella xylostella. Quantitative real-time PCR and immunohistochemistry revealed that PxPGRP-S1 is mainly expressed in the fat body of the healthy larva. The expression of PxPGRP-S1 was significantly upregulated in the midgut at 24 h postinfection by Bacillus thuringiensis. Silencing of the PxPGRP-S1 expression by RNAi, significantly decrease the expression of the antimicrobial peptides (AMPs) in the 4th instar larvae of P. xylostella. Similarly injection of an anti-PxPGRP-S1 serum caused the low expression of the AMPs in P. xylostella. Additionally, PxPGRP-S1 depleted P. xylostella by oral administration of bacterial expressed dsRNA decreased the resistance against B. thuringiensis challenge, leads to high mortality. Together, our result indicates that PxPGRP-S1, served as a bacterial pattern recognition receptor (PRR) and triggers the expression of AMPs in P. xylostella.

Functional characterization of short-type peptidoglycan recognition proteins (PGRPs) from silkworm Bombyx mori in innate immunity

Peptidoglycan recognition proteins (PGRPs) are members of an important class of pattern recognition receptors in insects that can specifically recognize peptidoglycan (PGN) in bacterial cell walls and participate in immune regulation and bacterial clearance. Although the role of PGRPs in regulating the innate immune response in Drosophila melanogaster has been studied, little is known regarding PGRPs in Lepidoptera species. In this study, five short (S)-type Bombyx mori PGRPs (BmPGRPs) were cloned, expressed, and evaluated for their function in innate immunity. B. mori larvae that were injected with the gram-positive bacterium Bacillus megaterium or the gram-negative bacterium Escherichia coli exhibited a rapid and significant upregulation in S-type BmPGRP expression. The results showed that the five evaluated BmPGRPs have significant agglutination activity toward E. coli and B. megaterium and more notable amidase activity toward meso-diaminopimelic acid peptidoglycan (DAP-PGN). Furthermore, only in the presence of BmPGRP-S5 did B. mori larval hemocytes exhibit significant phagocytosis against E. coli and B. megaterium.

The Dual Role of Neutrophils in HIV Infection

PURPOSE OF REVIEW

We summarize what is known about neutrophils in HIV infection, focusing on their potential roles in HIV protection, acquisition, and pathogenesis.

RECENT FINDINGS

Recent studies have demonstrated that neutrophil-associated proteins and cytokines in genital tissue pre-infection associate with HIV acquisition. However, recent in vivo assessment of highly exposed seronegative individuals and in vitro studies of anti-HIV functions of neutrophils add to older literature evidence that neutrophils may be important in a protective response to HIV infection. Neutrophils are important for containment of pathogens but can also contribute to tissue damage due to their release of reactive oxygen species, proteases, and other potentially harmful effector molecules. Overall, there is a clear evidence for both helpful and harmful roles of neutrophils in HIV acquisition and pathogenesis. Further study, particularly of tissue neutrophils, is needed to elucidate the kinetics, phenotype, and functionality of neutrophils in HIV infection to better understand this dichotomy.

A peptidoglycan recognition protein involved in immune recognition and immune defenses in Ruditapes philippinarum

Peptidoglycan recognition proteins (PGRPs) are important pattern recognition receptors in the innate immune system of invertebrates. In the study, a short PGRP (designed as RpPGRP) was identified and characterized from the manila clam Ruditapes philippinarum. The open reading frame of RpPGRP encoded a polypeptide of 249-amino acids with a calculated molecular mass of 27.2 kDa and an isoelectric point of 6.62. Multiple alignments and phylogenetic analysis strongly suggested that RpPGRP was a new member of the PGRP superfamily. In non-stimulated clams, RpPGRP exhibited different tissue expression pattern, and highly expressed in hepatopancreas and hemocytes. Expression of RpPGRP transcripts was significantly up-regulated in hemocytes of clams post Vibrio anguillarum or Micrococcus luteus challenge. The recombinant RpPGRP (rRpPGRP) exhibited high affinity to PGN, LPS and zymosan in a concentration-dependent manner. With a broad spectrum of bacterial binding activities, rRpPGRP exhibited strong agglutination activity to Escherichia coli, Vibrio splendidus, V. anguillarum and M. luteus. Furthermore, rRpPGRP exhibited Zn²⁺-dependent amidase activity and catalyzed the degradation of insoluble PGN. Especially, rRpPGRP exhibited significant antibacterial activity against E. coli and M. luteus. Moreover, the biofilm formation of E. coli could be inhibited after rRpPGRP incubation in the presence of Zn²⁺. This inhibitory effect of rRpPGRP might attribute to its amide bactericidal activity. Taken together, rRpPGRP played important roles in PGRP-mediated immune defense mechanisms, especially by recognizing antigens and eliminating bacteria.

Molecular characterisation of immunological memory following homologous or heterologous challenges in the schistosomiasis vector snail, Biomphalaria glabrata

Invertebrate immune response may be primed by a current infection in a sustained manner, leading to the failure of a secondary infection with the same pathogen. The present study focuses on the Schistosomiasis vector snail Biomphalaria glabrata, in which a specific genotype-dependent immunological memory was demonstrated as a shift from a cellular to a humoral immune response. Herein, we investigate the complex molecular bases associated with this genotype-dependant immunological memory response. We demonstrate that Biomphalaria regulates a polymorphic set of immune recognition molecules and immune effector repertoires to respond to different strains of Schistosoma parasites. These results suggest a combinatorial usage of pathogen recognition receptors (PRRs) that distinguish different strains of parasites during the acquisition of immunological memory. Immunizations also show that snails become resistant after exposure to parasite extracts. Hemolymph transfer and a label-free proteomic analysis proved that circulating hemolymph compounds can be produced and released to more efficiently kill the newly encountered parasite of the same genetic lineage.

Transcriptional Analysis of HELA Cells - Producers of the Recombinant Peptidoglycan Recognition Protein PGLYRP1 at Different Stages of the Chlamydia Trachomatis Infection Development

Human peptidoglycan recognition proteins (PGLYRPs) are the components of innate immunity that exhibit antibacterial activity. In this study a cell line secreting recombinant PGLYRP1 into a culture medium was obtained. Transcriptional profiling of cell lines expressing PGLYRP1 was performed at different stages of C. trachomatis infection. Differential gene expression was studied using the whole transcriptome profiling method on the HumanHT-12 v4 Expression BeadChip microchip using the Illumina Direct Hybridization Whole-Gene Expression Assay protocol. Sample clustering followed by bioinformatics analysis revealed about 100 differentially expressed genes in response to infection with C. trachomatis. PGLYRP1- expressing cells infected with C. trachomatis had a similar transcriptional profile as non-infected cells.

Characterization of PGRP-S1 from the oriental armyworm, Mythimna separata

Peptidoglycan is the key component forming the backbone of bacterial cell wall. It can be recognized by a group of pattern recognition receptors, known as peptidoglycan recognition proteins (PGRPs) in insects and higher animals. PGRPs may serve as immune receptors or N-acetylmuramoyl-L-alanine amidases (EC 3.5.1.28). Here, we report the characterization of a short PGRP, PGRP-S1, from the oriental armyworm, Mythimna separata. MsePGRP-S1 cDNA encodes a protein of 197 amino acids (aa) with a PGRP domain of about 150 aa. MsePGRP-S1 was expressed in several tissues of naïve larvae, including hemocytes, midgut, fat body and epidermis. Bacterial challenges caused variable changes in different tissues at the mRNA level. The recombinant protein bound strongly to Staphylococcus aureus and purified peptidoglycans from Staphylococcus aureus and Bacillus subtilis. It can inhibit the growth of gram-negative and gram-positive bacteria by disrupting bacterial surface. It can degrade peptidoglycans from Escherichia coli and Staphylococcus aureus. Taken together, these data demonstrate that M. separata PGRP-S1 is involved in defending against bacteria.

Peptidoglycan recognition proteins in insect immunity

Insects lack an acquired immune system and rely solely on the innate immune system to combat microbial infection. The innate immunity of insects mainly depends on the interaction between the host's pattern recognition receptor (PRR) and pathogen-associated molecular pattern (PAMP). The peptidoglycan recognition proteins (PGRPs) family is the most important pattern recognition receptor (PRR) for insects. It can recognize the main component of the cell wall of the pathogenic microorganism, peptidoglycan (PGN), and plays an important role in the innate immunity of insects. In this paper, the structure, classification, and function of PGRPs is summarized, and the role of PGRPs in the innate immunity of insects is also discussed.

Tilorone activates NK cells and cytotoxic lymphocytes that kill HLA-negative tumor cells

Tilorone hydrochloride, a low-molecular-weight synthetic compound, induces interferon production and has been reported to have both antiviral and antitumor activities. Here, we have demonstrated the ability of tilorone to activate NK cells and specific subpopulations of cytotoxic CD4+ and CD8+ T lymphocytes that recognize immune-evasive tumor cells and kill them via the FasL-Fas interaction. We have also performed a comparative analysis of characteristics between lymphocytes activated in the fraction of human peripheral blood mononuclear cells (PBMCs) upon treatment with different stimulants of the immune response: tilorone, innate immunity protein Tag7, and cytokine IL-2, a regulator of adaptive immunity. The results show that all the three stimulants, regardless of their nature, activate lymphocytes that are identical with respect to the spectrum of target cells, phenotype, and mechanism of cytotoxic action However, these stimulants induce different mechanisms of lymphocyte activation at early stages of the immune response. © 2018 IUBMB Life, 71(3):376-384, 2019.

Competing RNA pairings in complex alternative splicing of a 3' variable region

Alternative pre-mRNA splicing remarkably expands protein diversity in eukaryotes. Drosophila PGRP-LC can generate three major 3' splice isoforms that exhibit distinct innate immune recognition and defenses against various microbial infections. However, the regulatory mechanisms underlying the uniquely biased splicing pattern at the 3' variable region remain unclear. Here we show that competing RNA pairings control the unique splicing of the 3' variable region of Drosophila PGRP-LC pre-mRNA. We reveal three roles by which these RNA pairings jointly regulate the 3' variant selection through activating the proximal 3' splice site and concurrently masking the intron-proximal 5' splice site, in combination with physical competition of RNA pairing. We also reveal that competing RNA pairings regulate alternative splicing of the highly complex 3' variable regions of Drosophila CG42235 and Pip Our findings will facilitate a better understanding of the regulatory mechanisms of highly complex alternative splicing as well as highly variable 3' processing.

Involvement of a short-type peptidoglycan recognition protein (PGRP) from Chinese giant salamanders Andrias davidianus in the immune response against bacterial infection

PGRPs (Peptidoglycan recognition proteins) could recognize peptidoglycan and play vital roles in innate immunity among different animals. Till present, the functions of PGRP have been studied in various animals, but few reports have studied the amphibian PGRPs. In the current research, a short type PGRP was identified from Chinese giant salamander and its involvement in the innate immunity was studied. The ORF of AdPGRP-SC2 cDNA was 573 bp, which encoded 190 amino acids, and contained a PGRP and an amidase_2 domain. The qPCR analysis revealed that AdPGRP-SC2 mRNA transcripts expressed in different tissues, with the highest expression level in muscle, intestine and spleen. Results of immune challenges with peptidoglycan (PGN) demonstrated that expression patterns of AdPGRP-SC2 were significantly up-regulated in erythrocyte and spleen at the early injection stage. The recombinant AdPGRP-SC2 protein was successfully produced and purified, and it could show binding affinity to different bacteria. In the presence of Zn²⁺, the rAdPGRP-SC2 could exhibit a broad PAMPs binding activities, strongly agglutinate bacteria and exhibit amidase enzyme activity. Collectively, these data indicate AdPGRP-SC2 could act as PRR to recognize the invading microorganisms and as the antimicrobial effectors during the innate immune response of A. davidianus.

A novel peptidoglycan recognition protein involved in the prophenoloxidase activation system and antimicrobial peptide production in Antheraea pernyi

Pattern recognition receptors (PRRs) are employed in insects to defend against infectious pathogens by triggering various immune responses. Peptidoglycan recognition proteins (PGRPs), a vital family of PRRs, are widely distributed and highly conserved from vertebrates to invertebrates. To date, five PGRP genes have been identified in Antheraea pernyi, but their biochemical roles still remain unknown. In this study, we focused on the immune functions of PGRP-SA in A. pernyi (ApPGRP-SA), which was confirmed to be immune-related according to its significantly up-regulated expression level post microbial injection. In addition, the binding properties of ApPGRP-SA were investigated using a recombinant protein produced in a prokaryotic expression system, revealing that rApPGRP-SA displayed a multi-binding ability to various microbes, including the Gram-positive bacteria Staphylococcus aureus and Micrococcus luteus, Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa, and fungus Candida albicans, together with their surface pathogen associated molecular patterns (PAMPs). Further studies showed that after recognition, the mixture of rApPGRP-SA/PAMP remarkably stimulated prophenoloxidase (PPO) activation in the hemolymph of A. pernyi in vitro, while the ds-PGRP-SA-treated hemolymph exhibited a lower sensitivity to PAMPs in comparison to the native sample. Moreover, the transcriptional level of the three antimicrobial peptides was also decreased in PGRP-SA knock-down larvae in response to immune-challenge. In summary, we conclude that ApPGRP-SA is a novel identified PGRP in A. pernyi that might act as a broad-spectrum pattern recognition receptor and is involved in the PPO activation system as well as antimicrobial peptide production.

FasL on the surface of Tag7 (PGRP-S)-activated lymphocytes induces necroptosis in HLA-negative tumor cells with the involvement of lysosomes and mitochondria

Recently we have found that cytokine IL-2 and innate immunity protein Tag7 activate cytotoxic lymphocytes that kill HLA-negative tumor cells, inducing both apoptosis and necroptosis. Here we decrypt the processes, taking part in necroptosis execution after FasL-Fas interaction. Necroptosis begins with RIPK1 activation and necrosome formation. Subsequent activation of MLKL results in the increase of Ca2+ level in the cell and activation of Ca2+-dependent enzymes causing lysosomal membrane permeabilization and the release of cathepsins to the cytosol. STAT3 translocation to the mitochondria and binding to a component of the respiratory chain complex I causes ROS accumulation. We have shown that transduction of necroptotic signal via TNFR1 and Fas has many common points. It is known that apoptosis plays a major role in physiological cell death; however, under pathological conditions necroptosis is very common. That is why the detailed mechanisms of FasL-Fas necroptosis can help in understanding the processes of elimination of tumor cells that have blocked apoptosis signal transduction.

Molecular characterization, expression and functional analysis of peptidoglycan recognition protein-SC2 from rock bream, Oplegnathus fasciatus

Peptidoglycan recognition proteins are members of the family of pattern recognition receptors (PRRs), that play important roles in the recognition of peptidoglycan and various biological processes. In this study, we have characterized peptidoglycan recognition protein-SC2 (PGRP-SC2) in rock bream (Oplegnathus fasciatus) (RbPGRP-SC2) and analysed its expression in various tissues after pathogen challenge. A sequence alignment revealed that the residues essential to zinc binding of the deduced protein were highly conserved among all the organisms. Phylogenetic analysis revealed that RbPGRP-SC2 is most closely related to the large yellow croaker PGRP-SC2. RbPGRP-SC2 was ubiquitously expressed in all tissues analysed, predominantly distributed in muscle and skin. After challenge with microbial pathogens (Edwardsiella piscicida), Streptococcus iniae or red seabream iridovirus [RSIV]), RbPGRP-SC2 was up-regulated in all the tissues examined, especially in liver. We produced recombinant RbPGRP-SC2 (rRbPGRP-SC2) using an Escherichia coli expression system. The rRbPGRP-SC2 had agglutination activity towards both Gram-negative (E. piscicida) and Gram-positive bacteria (S. iniae). In addition, rRbPGRP-SC2 induced leukocyte apoptosis and promoted leukocyte phagocytosis. These results suggest that the RbPGRP-SC2 plays an important role in the immune system and in maintaining cellular homeostasis of rock bream.

Innate immune responses in the Chinese oak silkworm, Antheraea pernyi

Innate immunity, the evolutionarily conserved defense system, has been extensively analyzed in insect models over recent decades. The significant progress in this area has formed our dominant conceptual framework of the innate immune system, but critical advances in other insects have had a profound impact on our insights into the mystery of innate immunity. In recent years, we focused on the immune responses in Antheraea pernyi, an important commercial silkworm species reared in China. Here, we review the immune responses of A. pernyi based on immune-related gene-encoded proteins that are divided into five categories, namely pattern recognition receptors, hemolymph proteinases and their inhibitors, prophenoloxidase, Toll pathway factors and antimicrobial peptides, and others. Although the summarized information is limited since the research on A. pernyi immunity is in its infancy, we hope to provide evidence for further exploration of innate immune mechanisms.

Peptidoglycan recognition proteins in hematophagous arthropods

Hematophagous arthropods are medically important disease vectors that transmit a variety of pathogens. Unlike mammals that employ both innate and adaptive immunity to clear invading pathogens, these vectors rely mainly on an innate immune system to combat pathogens. Peptidoglycan recognition proteins (PGRPs) are important components of innate immune signaling pathways and are responsible for recognizing microbe-associated molecular patterns (MAMPs), thus regulating host immune interactions with both harmful and helpful microbes. Here we review a number of recent studies in different vectors that address the function of PGRPs in immune regulation. Further, we discuss the variation of PGRPs between vectors and Drosophila.

Immune responses to bacterial and fungal infections in the silkworm, Bombyx mori

The silkworm Bombyx mori, an economically important insect that is usually reared indoors, is susceptible to various pathogens, including bacteria, fungi, viruses, and microsporidia. As with other insects, the silkworm lacks an adaptive immune system and relies solely on innate immunity to defend itself against infection. Compared to other intensively studied insects, such as the fruit fly and tobacco hornworm, the principal immune pathways in the silkworm remain unclear. In this article, we review the literature concerning silkworm immune responses to bacteria and fungi and present our perspectives on future research into silkworm immunity.

Diapause in a tropical oil-collecting bee: molecular basis unveiled by RNA-Seq

BACKGROUND

Diapause is a natural phenomenon characterized by an arrest in development that ensures the survival of organisms under extreme environmental conditions. The process has been well documented in arthropods. However, its molecular basis has been mainly studied in species from temperate zones, leaving a knowledge gap of this phenomenon in tropical species. In the present study, the Neotropical and solitary bee Tetrapedia diversipes was employed as a model for investigating diapause in species from tropical zones. Being a bivoltine insect, Tetrapedia diversipes produce two generations of offspring per year. The first generation, normally born during the wet season, develops faster than individuals from the second generation, born after the dry season. Furthermore, it has been shown that the development of the progeny, of the second generation, is halted at the 5th larval instar, and remains in larval diapause during the dry season. Towards the goal of gaining a better understanding of the diapause phenomenon we compared the global gene expression pattern, in larvae, from both reproductive generations and during diapause. The results demonstrate that there are similarities in the observed gene expression patterns to those already described for temperate climate models, and also identify diapause-related genes that have not been previously reported in the literature.

RESULTS

The RNA-Seq analysis identified 2275 differentially expressed transcripts, of which 1167 were annotated. Of these genes, during diapause, 352 were upregulated and 815 were downregulated. According to their biological functions, these genes were categorized into the following groups: cellular detoxification, cytoskeleton, cuticle, sterol and lipid metabolism, cell cycle, heat shock proteins, immune response, circadian clock, and epigenetic control.

CONCLUSION

Many of the identified genes have already been described as being related to diapause; however, new genes were discovered, for the first time, in this study. Among those, we highlight: Niemann-Pick type C1, NPC2 and Acyl-CoA binding protein homolog (all involved in ecdysteroid synthesis); RhoBTB2 and SASH1 (associated with cell cycle regulation) and Histone acetyltransferase KAT7 (related to epigenetic transcriptional regulation). The results presented here add important findings to the understanding of diapause in tropical species, thus increasing the comprehension of diapause-related molecular mechanisms.

Tag7 (PGLYRP1) Can Induce an Emergence of the CD3+CD4+CD25+CD127+ Cells with Antitumor Activity

We have shown that in the human peripheral blood cells, the innate immunity protein Tag7 can activate a subpopulation of CD3+CD4+CD25+ cells, which have antitumor activity. These cells can induce lysis of HLA-negative tumor cell lines. The Hsp70 stress molecule on the surface of the tumor cells is used as a recognition target, while the Tag7 protein on the lymphocyte membrane acts as a receptor for Hsp70. We have also demonstrated that this subpopulation of the CD4+CD25+ cells is CD127 positive and hence is not the Treg cells. Our data suggest that this subpopulation of cells is identical to the CD4+CD25+ lymphocytes, which are activated in the leukocyte pool by the IL-2 cytokine.

Novel approach to study gastropod-mediated innate immune reactions against metastrongyloid parasites

The anthropozoonotic metastrongyloid nematodes Angiostrongylus cantonensis and Angiostrongylus costaricensis, as well as Angiostrongylus vasorum, Crenosoma vulpis, Aelurostrongylus abstrusus and Troglostrongylus brevior are currently considered as emerging gastropod-borne parasites and have gained growing scientific attention in the last years. However, the knowledge on invertebrate immune responses and on how metastrongyloid larvae are attacked by gastropod immune cells is still limited. This work aims to describe an in vitro system to investigate haemocyte-derived innate immune responses of terrestrial gastropods induced by vital axenic metastrongyloid larvae. We also provide protocols on slug/snail management and breeding under standardized climate conditions (circadian cycle, temperature and humidity) for the generation of parasite-free F0 stages which are essential for immune-related investigations. Adult slug species (Arion lusitanicus, Limax maximus) and giant snails (Achatina fulica) were maintained in fully automated climate chambers until mating and production of fertilized eggs. Newly hatched F0 juvenile specimens were kept under parasite-free conditions before experimental use. An improved protocol for gastropod haemolymph collection and haemocyte isolation was established. Giemsa-stained haemolymph preparations showed adequate haemocyte isolation in all three gastropod species. Additionally, a protocol for the production of axenic first and third stage larvae (L1, L3) was established. Haemocyte functionality was tested in haemocyte-nematode-co-cultures. Scanning electron microscopy (SEM) and light microscopy analyses revealed that gastropod-derived haemocytes formed clusters as well as DNA-rich extracellular aggregates catching larvae and decreasing their motility. These data confirm the usefulness of the presented methods to study haemocyte-mediated gastropod immune responses to better understand the complex biology of gastropod-borne diseases.

Molecular cloning and characterization of a short peptidoglycan recognition protein from silkworm Bombyx mori

Peptidoglycan is the major bacterial component recognized by the insect immune system. Peptidoglycan recognition proteins (PGRPs) are a family of pattern-recognition receptors that recognize peptidoglycans and modulate innate immune responses. Some PGRPs retain N-acetylmuramoyl-L-alanine amidase (Enzyme Commission number: 3.5.1.28) activity to hydrolyse bacterial peptidoglycans. Others have lost the enzymatic activity and work only as immune receptors. They are all important modulators for innate immunity. Here, we report the cloning and functional analysis of PGRP-S4, a short-form PGRP from the domesticated silkworm, Bombyx mori. The PGRP-S4 gene encodes a protein of 199 amino acids with a signal peptide and a PGRP domain. PGRP-S4 was expressed in the fat body, haemocytes and midgut. Its expression level was significantly induced by bacterial challenges in the midgut. The recombinant PGRP-S4 bound bacteria and different peptidoglycans. In addition, it inhibited bacterial growth and hydrolysed an Escherichia coli peptidoglycan in the presence of Zn²⁺ . Scanning electron microscopy showed that PGRP-S4 disrupted the bacterial cell surface. PGRP-S4 further increased prophenoloxidase activation caused by peptidoglycans. Taken together, our data suggest that B. mori PGRP-S4 has multiple functions in immunity.

Impacts of diarrhea on the immune system, intestinal environment, and expression of PGRPs in New Zealand rabbits

Diarrhea is a syndrome of digestive disorders in young rabbits and may lead to secondary infections resulting in reduced immunity and higher mortality in baby rabbits, with serious impacts on rabbit farming. In this study, we investigated the effects of diarrhea on the health of baby rabbits in terms of intestinal mucosal development, immune function, and intestinal microbial diversity. We found that the duodenal villus length and the villus/crypt ratio in rabbits with diarrhea were significantly reduced compared with those in healthy rabbits (P < 0.01). Rabbits with diarrhea had significantly lower concentrations of acetic acid (P < 0.05), higher pH levels (P < 0.05), and higher levels of ammonia nitrogen (P < 0.01) in the cecum. Moreover, diarrhea in baby rabbits led to significantly reduced levels of total serum protein (P < 0.05) and markedly increased levels of alkaline phosphatase, urea nitrogen, TNF-α, and IL-6 (P < 0.05). Transcriptional analysis of peptidoglycan recognition proteins (PGRPs, including PGLYRP-1, PGLYRP-2, and PGLYRP-3) using real-time PCR revealed that diarrhea induced the upregulation of PGRPs in the cecum and duodenum. Furthermore, through pyrosequencing of the 16S rRNA V4 region in cecum samples, we found that the total number and diversity of microbes were not significantly different between healthy rabbits and those with diarrhea, though there were noticeable differences in the prevalences of Clostridium, Roseburia, and Alistipes. Our results will contribute to a better understanding of the pathological mechanisms of diarrhea in young rabbits.

Fish antimicrobial peptides (AMP's) as essential and promising molecular therapeutic agents: A review

Antimicrobial peptides (AMPs) are generally considered as an essential component of innate immunity, thereby providing the first line of defense against wide range of pathogens. In addition, they can also kill the pathogens which are generally resistant to number of antibiotics, thereby providing the avenues for the development of future therapeutic agents. Fishes are constantly challenged by variety of pathogens which not only shows detrimental effect on their health but also increases risk of becoming resistant to conventional antibiotics. As fishes rely more on innate immunity, AMPs can serve as a potential defensive weapons in fishes for combating emerging devastating diseases. Generally, AMPs show multidimensional properties like rapid diffusion to the site of infection, recruitment of other immune cells to infected tissues and vigorous potential to rapidly neutralize broad range of pathogens (bacterial, fungal and viral). AMPs also exhibit diverse biological effect like endotoxin neutralization, immunomodulation and induction of angiogenesis in mammals. Due to these properties AMPs have become one of the most promising therapeutic agents to be studied. Till date, many AMPs have been isolated from the fishes but not fully characterized at molecular level. This review provides an overview of the structures, functions, and putative mechanisms of major families of fish AMPs. Further, we also highlighted how fish AMPs can be used as a novel therapeutic tool which is the theme of future research in drug development.

Innate immunity protein Tag7 (PGRP-S) activates lymphocytes capable of Fasl-Fas-dependent contact killing of virus-infected cells

The innate immunity protein Tag7 (PGRP-S, PGLYRP1) is involved in antimicrobial and antitumor defense. As shown in our previous studies, Tag7 specifically interacts with the major heat shock protein Hsp70 to form a stable Tag7-Hsp70 complex with cytotoxic activity against tumor cells. A stable complex of Tag7 with the calcium-binding protein Mts1 (S100A4) stimulates migration of lymphocytes. Moreover, Tag7 can activate cytotoxic lymphocytes that recognize and kill HLA-negative tumor cells. Here, we have shown that Tag 7 treatment of human peripheral blood mononuclear cells (PBMCs) results in activation of different cytotoxic lymphocyte populations-natural killer (NK) cells and CD8⁺ NKG2D⁺ T lymphocytes-that kill Moloney murine leukemia virus (MMLV) infected SC-1 cells using different mechanisms of cell death induction. This mechanism in NK cells is based on the release of granzymes, which activate apoptosis in target cells, while CD8⁺ NKG2D⁺ T lymphocytes recognize the noncanonical MicA antigen on the surface of virus-containing cells and kill them via the FasL-Fas interaction, triggering the apoptotic or necroptotic cell death pathway. Preliminary incubation of PBMCs with virus-infected cells and following incubation with Tag7 results in activation of lymphocytes with a different phenotype. These lymphocytes change the spectrum of target cells and the mechanism of cell death induction, and their interaction with target cells is not species-specific. © 2017 IUBMB Life, 69(12):971-977, 2017.

Targeting the permeability barrier and peptidoglycan recycling pathways to disarm Pseudomonas aeruginosa against the innate immune system

Antimicrobial resistance is a continuously increasing threat that severely compromises our antibiotic arsenal and causes thousands of deaths due to hospital-acquired infections by pathogens such as Pseudomonas aeruginosa, situation further aggravated by the limited development of new antibiotics. Thus, alternative strategies such as those targeting bacterial resistance mechanisms, virulence or potentiating the activity of our immune system resources are urgently needed. We have recently shown that mutations simultaneously causing the peptidoglycan recycling blockage and the β-lactamase AmpC overexpression impair the virulence of P.aeruginosa. These findings suggested that peptidoglycan metabolism might be a good target not only for fighting antibiotic resistance, but also for the attenuation of virulence and/or potentiation of our innate immune weapons. Here we analyzed the activity of the innate immune elements peptidoglycan recognition proteins (PGRPs) and lysozyme against P. aeruginosa. We show that while lysozyme and PGRPs have a very modest basal effect over P. aeruginosa, their bactericidal activity is dramatically increased in the presence of subinhibitory concentrations of the permeabilizing agent colistin. We also show that the P. aeruginosa lysozyme inhibitors seem to play a very residual protective role even in permeabilizing conditions. In contrast, we demonstrate that, once the permeability barrier is overpassed, the activity of lysozyme and PGRPs is dramatically enhanced when inhibiting key peptidoglycan recycling components (such as the 3 AmpDs, AmpG or NagZ), indicating a decisive protective role for cell-wall recycling and that direct peptidoglycan-binding supports, at least partially, the activity of these enzymes. Finally, we show that recycling blockade when occurring simultaneously with AmpC overexpression determines a further decrease in the resistance against PGRP2 and lysozyme, linked to quantitative changes in the cell-wall. Thus, our results help to delineate new strategies against P. aeruginosa infections, simultaneously targeting β–lactam resistance, cell-wall metabolism and virulence, ultimately enhancing the activity of our innate immune weapons.

Two short peptidoglycan recognition proteins from Crassostrea gigas with similar structure exhibited different PAMP binding activity

Peptidoglycan recognition protein (PGRP) is an essential molecule in innate immunity for both invertebrates and vertebrates, owing to its prominent ability in specifically recognizing bacterial peptidoglycan (PGN) and eliminating the invading bacteria. In the present study, the full length cDNA of two PGRP genes, CgPGRPS2 and CgPGRPS4, were cloned from oyster Crassostrea gigas. Their amino acid sequences both contained one signal peptide, one typical PGRP/amidase domain with conserved catalytic residues responsible for amidase activity (55H, 90Y, 164H, 172C in CgPGRPS2, and 98H, 133Y, 207H, 215C in CgPGRPS4), and specific PGN recognition (84R, 85W, 104R, 109V in CgPGRPS2, and 127G, 128W, 147R, 152V in CgPGRPS4), and they shared 55.9% sequence similarity. The mRNA transcripts of CgPGRPS2 and CgPGRPS4 were constitutively expressed in all the examined tissues, including haemocytes, hepatopancreas, mantle, gonad, heart, adductor muscle and gill, with the highest expression level in adductor muscle and hepatopancreas, respectively. Both CgPGRPS2 and CgPGRPS4 proteins were mainly localized in the cytoplasma. The recombinant protein of CgPGRPS2 (rCgPGRPS2) could bind lipopolysaccharide (LPS), PGN and mannan (Man), as well as various microorganisms including Gram-negative bacteria Escherichia coli, Vibrio anguillarum, Gram-positive bacteria Staphylococcus aureus and fungi Yarrowia lipolytica. The recombinant protein of CgPGRPS4 (rCgPGRPS4) exhibited higher binding affinity to PGN, lower binding affinity to LPS, while no binding activity to Man and Y. lipolytica. The results indicated that CgPGRPS2 and CgPGRPS4 could function as pattern recognition receptors (PRR) in the innate immune response of oyster, and they exhibited a certain degree of functional differentiation in recognition of Man.

Unveiling differentially expressed genes upon regulation of transcription factors in sepsis

In this study, we integrated the gene expression data of sepsis to reveal more precise genome-wide expression signature to shed light on the pathological mechanism of sepsis. Differentially expressed genes via integrating five microarray datasets from the Gene Expression Omnibus database were obtained. The gene function and involved pathways of differentially expressed genes (DEGs) were detected by GeneCodis3. Transcription factors (TFs) targeting top 20 dysregulated DEGs (including up- and downregulated genes) were found based on the TRANSFAC. A total of 1339 DEGs were detected including 788 upregulated and 551 downregulated genes. These genes were mostly involved in DNA-dependent transcription regulation, blood coagulation, and innate immune response, pathogenic escherichia coli infection, epithelial cell signaling in helicobacter pylori infection, and chemokine signaling pathway. TFs bioinformatic analysis of 20 DEGs generated 374 pairs of TF-target gene involving 47 TFs. At last, we found that five top ten upregulated DEGs (S100A8, S100A9, S100A12, PGLYRP1 and MMP9) and three downregulated DEGs (ZNF84, CYB561A3 and BST1) were under the regulation of three hub TFs of Pax-4, POU2F1, and Nkx2-5. The identified eight DEGs may be regarded as the diagnosis marker and drug target for sepsis.

An overview of the synergy and crosstalk between pentraxins and collectins/ficolins: their functional relevance in complement activation

The complement system is an innate immune defense machinery comprising components that deploy rapid immune responses and provide efficient protection against foreign invaders and unwanted host elements. The complement system is activated upon recognition of pathogenic microorganisms or altered self-cells by exclusive pattern recognition molecules (PRMs), such as collectins, ficolins and pentraxins. Recent accumulating evidence shows that the different classes of effector PRMs build up a co-operative network and exert synergistic effects on complement activation. In this review, we describe our updated view of the crosstalk between previously unlinked PRMs in complement activation and the potential pathogenic effects during infection and inflammation.

Lymphocytes incubated in the presence of IL-2 lose the capacity for chemotaxis but acquire antitumor activity

Naïve non-activated lymphocytes are capable of releasing the chemoattractant complex Tag7-Mts1 and can migrate along the gradient of its concentration. After activation of these cells by IL-2, they acquire the abilities to kill tumor cells and to release the cytotoxic Tag7-Hsp70 complex, which is accompanied by a loss of both the Tag7-Mts1-mediated lymphocyte chemotaxis and the ability to release this chemoattractant into the conditioned medium.

Comparative analysis of peptidoglycan recognition proteins in endoparasitoid wasp Microplitis mediator

Peptidoglycan recognition proteins (PGRPs) are a family of innate immune receptors that specifically recognize peptidoglycans (PGNs) on the surface of a number of pathogens. Here, we have identified and characterized six PGRPs from endoparasitoid wasp, Microplitis mediator (MmePGRPs). To understand the roles of PGRPs in parasitoid wasps, we analyzed their evolutionary relationship and orthology, expression profiles during different developmental stages, and transcriptional expression following infection with Gram-positive and -negative bacteria and a fungus. MmePGRP-S1 was significantly induced in response to pathogenic infection. This prompted us to evaluate the effects of RNA interference mediated gene specific knockdown of MmePGRP-S1. The knockdown of MmePGRP-S1 (iMmePGRP-S1) dramatically affected wasps' survival following challenge by Micrococcus luteus, indicating the involvement of this particular PGRP in immune responses against Gram-positive bacteria. This action is likely to be mediated by the Toll pathway, but the mechanism remains to be determined. MmePGRP-S1 does not play a significant role in anti-fungal immunity as indicated by the survival rate of iMmePGRP-S1 wasps. This study provides a comprehensive characterization of PGRPs in the economically important hymenopteran species M. mediator.

Involvement of PGRP-SC2 from Artemia sinica in the innate immune response against bacteria and expression pattern at different developmental stages

Peptidoglycan-recognition protein-SC2 precursor-like protein (PGRP-SC2) is a vital protein in innate immunity with a vita role in response to bacteria challenge in invertebrates. Here, a 678-bp full-length cDNA of pgrp-sc2 from A. sinica was obtained containing a 558-bp open reading frame encoding 185 amino acids with a calculated molecular mass of 19.6 kDa. The predicted protein contains a PGRP and an Amidase2 domain, indicating that PGRP-SC2 is a PGRP family member and has N-acetylmuramoyl-l-alanine amidase activity. The expression and localization of pgrp-sc2/PGRP-SC2 in A.sinica during embryonic development and bacterial challenge were determined by qPCR, WB and ISH. During different A. sinica embryonic development stages, the expression level of pgrp-sc2/PGRP-SC2 was most highly expressed at 0 and 5 h and after challenge by Gram-positive bacteria, it increased with increasing bacterial concentrations, indicating that it plays a vital role in A. sinica early embryonic development and innate immunity.

On the Molecular Basis of Division of Labor in Solenopsis invicta (Hymenoptera: Formicidae) Workers: RNA-seq Analysis

The fire ant Solenopsis invicta Buren is an important invasive pest. Among S. invicta workers behavioral changes depend on age where younger ants are nurses and older ants foragers. To identify potential genes associated with this division of labor, we compared gene expression between foragers and nurses by high-throughput sequencing. In total, we identified 1,618 genes significantly differently expressed between nurses and foragers, of which 542 were upregulated in foragers and 1,076 were upregulated in nurses. Several pathways related to metabolism were significantly enriched, such as lipid storage and fatty acid biosynthesis, which might contribute to the division of labor in S. invicta. Several genes involved in DNA methylation, transcription, and olfactory responses as well as resistance to stress were differentially expressed between nurses and foragers workers. Finally, a comparison between previously published microarray data and our RNA-seq data in S. invicta shows 116 genes overlap, and the GO term myofibril assembly (GO: 0030239) were simultaneously significantly enriched. These results advance knowledge of potentially important genes and molecular pathways associated with worker division of labor in S. invicta. We hope our dataset will provide . candidate target genes to disrupt organization in S. invicta as a control strategy against this invasive pest.