Purification, characterization, and cDNA cloning of a novel growth factor from the conditioned medium of NIH-Sape-4, an embryonic cell line of Sarcophaga peregrina (flesh fly)

Getting to know adenosine deaminase 2 deficiency inside and out

Ten years after the description of the first cohorts of patients with adenosine deaminase (ADA2) deficiency (DADA2), the pathomechanisms underlying the disease on a cellular level remain poorly understood. With the establishment of the lysosomal localization of the ADA2 protein and its involvement in nucleic acid sensing, the pathophysiologic focus has shifted to the inside of the cell. At the same time, extracellular (serum) ADA2 enzyme activity continues to be the diagnostic reference standard in patients with suspected DADA2. The diverse clinical phenotype and weak genotype-phenotype correlations further complicate the identification of shared cellular mechanisms that cause inflammation, immunodeficiency, and bone marrow failure in the absence of functional ADA2. This review inspects the characteristics of the ADA2 protein and its proposed function. The latter is discussed in the context of possible mechanisms driving the clinical phenotype in patients lacking functional ADA2. We discuss established processes and introduce unexplored pathways in the pathogenesis of DADA2.

Structural basis of substrate specificity of Helix pomatia AMP deaminase and a chimeric ADGF adenosine deaminase

HPAMPD, an enzyme enriched in the foot muscle of the mollusk Helix pomatia, exhibits deaminase activity on adenosine-5'-monophosphate (AMP). HPAMPD is the first member of the adenosine deaminase-related growth factor (ADGF) family to prefer the nucleotide, AMP, over the nucleoside, adenosine. To investigate the substrate selectivity of HPAMPD, we determined its structure in the apo form and in complex with the adenosine analogs pentostatin (2'-deoxycoformycin) and pentostatin-5'-monophosphate. Structurally, HPAMPD adopts a fold similar to human ADA2, an ADGF family member. HPAMPD has acquired the ability to interact with the 5'-monophosphate group of AMP through polar and charged residues located in three key structural elements: (1) the loop immediately following strand β1, (2) the loop between helices αH and αI, and (3) the end of strand β5 and its adjacent loop. We engineered a chimeric deaminase by integrating these elements from HPAMPD into another related mollusk nucleoside adenosine deaminase, the A. californica ADGF. The chimeric enzyme efficiently deaminates AMP, demonstrating a gained substrate specificity, while retaining the adenosine deamination activity of Aplysia ADGF. The phosphate-binding feature of HPAMPD is a hallmark of nucleotide deaminases, conserved among AMP and N6-methyl-AMP (6mAMP) deaminases. We discuss the human adenosine deaminases each with distinct substrate specificities for the nucleoside, the nucleotide (AMP), and the methylated form, 6mAMP.

Identification and localization of growth factor genes in the sea cucumber, Holothuria scabra

The sea cucumber Holothuria scabra is both an economically important species in Asian countries and an emerging experimental model for research studies in regeneration and medicinal bioactives. Growth factors and their receptors are known to be key components that guide tissue repair and renewal, yet validation of their presence in H. scabra has not been established. We performed a targeted in silico search of H. scabra transcriptome data to elucidate conserved growth factor family and receptor genes. In total, 42 transcripts were identified, of which 9 were validated by gene cloning and sequencing. The H. scabra growth factor genes, such as bone morphogenetic protein 2A (BMP 2A), bone morphogenetic protein 5-like (BMP5-like), neurotrophin (NT) and fibroblast growth factor 18 (FGF18), were selected for further analyses, including phylogenetic comparison and spatial gene expression using RT-PCR and in situ hybridization. Expression of all genes investigated were widespread in multiple tissues. However, BMP 2A, BMP5-like and NT were found extensively in the radial nerve cord cells, while FGF18 was highly expressed in connective tissue layer of the body wall. Our identification and expression analysis of the H. scabra growth factor genes provided the molecular information of growth factors in this species which may ultimately complement the research in regenerative medicine.

Sepsis target validation for repurposing and combining complement and immune checkpoint inhibition therapeutics

Introduction: Sepsis is a disease that occurs due to an adverse immune response to infection by bacteria, viruses and fungi and is the leading pathway to death by infection. The hallmarks for maladapted immune reactions in severe sepsis, which contribute to multiple organ failure and death, are bookended by the exacerbated activation of the complement system to protracted T-cell dysfunction states orchestrated by immune checkpoint control. Despite major advances in our understanding of the condition, there remains to be either a definitive test or an effective therapeutic intervention.Areas covered: The authors consider a combinational drug therapy approach using new biologics, and mathematical modeling for predicting patient responses, in targeting innate and adaptive immune mediators underlying sepsis. Special consideration is given for emerging complement and immune checkpoint inhibitors that may be repurposed for sepsis treatment.Expert opinion: In order to overcome the challenges inherent to finding new therapies for the complex dysregulated host response to infection that drives sepsis, it is necessary to move away from monotherapy and promote precision for personalized combinatory therapies. Notably, combinatory therapy should be guided by predictive systems models of the immune-metabolic characteristics of an individual's disease progression.

Human adenosine deaminase 2 deficiency: A multi-faceted inborn error of immunity

Human adenosine deaminase 1 deficiency was described in the 1970s to cause severe combined immunodeficiency. The residual adenosine deaminase activity in these patients was attributed to adenosine deaminase 2. Human adenosine deaminase type 2 deficiency (DADA2), due to biallelic deleterious mutations in the ADA2 gene, is the first described monogenic type of small- and medium-size vessel vasculitis. The phenotype of DADA2 also includes lymphoproliferation, cytopenia, and variable degrees of immunodeficiency. The physiological role of ADA2 is still enigmatic hence the pathophysiology of the condition is unclear. Preliminary data showed that in the absence of ADA2, macrophage differentiation is skewed to a pro-inflammatory M1 subset, which is detrimental for endothelial integrity. The inflammatory phenotype responds well to anti-TNF therapy with etanercept and that is the first-line treatment for prevention of severe vascular events including strokes. The classic immunosuppressive drugs are not successful in controlling the disease activity. However, hematopoietic stem cell transplantation (HSCT) has been shown to be a definitive cure in DADA2 patients who present with a severe cytopenia. HSCT can also cure the vascular phenotype and is the treatment modality for patients' refractory to anti-cytokine therapies. In this review, we describe what is currently known about the molecular mechanisms of DADA2. Further research on the pathophysiology of this multifaceted condition is needed to fine-tune and steer future therapeutic strategies.

Deficiency of Adenosine Deaminase 2 (DADA2): Updates on the Phenotype, Genetics, Pathogenesis, and Treatment

Deficiency of ADA2 (DADA2) is the first molecularly described monogenic vasculitis syndrome. DADA2 is caused by biallelic hypomorphic mutations in the ADA2 gene that encodes the adenosine deaminase 2 (ADA2) protein. Over 60 disease-associated mutations have been identified in all domains of ADA2 affecting the catalytic activity, protein dimerization, and secretion. Vasculopathy ranging from livedo reticularis to polyarteritis nodosa (PAN) and life-threatening ischemic and/or hemorrhagic stroke dominate the clinical features of DADA2. Vasculitis and inflammation can affect many organs, explaining the intestinal, hepatological, and renal manifestations. DADA2 should be primarily considered in patients with early-onset fevers, rashes, and strokes even in the absence of positive family history. Hematological manifestations include most commonly hypogammaglobulinemia, although pure red cell aplasia (PRCA), immune thrombocytopenia, and neutropenia have been increasingly reported. Thus, DADA2 may unify a variety of syndromes previously not thought to be related. The first-line treatment consists of TNF-inhibitors and is effective in controlling inflammation and in preserving vascular integrity. Hematopoietic stem cell transplantation (HSCT) has been successful in a group of patients presenting with hematological manifestations. ADA2 is highly expressed in myeloid cells and plays a role in the differentiation of macrophages; however, its function is still largely undetermined. Deficiency of ADA2 has been linked to an imbalance in differentiation of monocytes towards proinflammatory M1 macrophages. Future research on the function of ADA2 and on the pathophysiology of DADA2 will improve our understanding of the condition and promote early diagnosis and targeted treatment.

Effects of tussah immunoreactive substances on growth, immunity, disease resistance against Vibrio splendidus and gut microbiota profile of Apostichopus japonicus

Tussah immunoreactive substance (TIS) comprises a number of active chemicals with various bioactivities. The current study investigated the effects of these substances on the sea cucumber Apostichopus japonicus. The specific growth rate (SGR) of TIS-fed sea cucumbers was significantly enhanced, whereas no significant difference in SGR was observed between those soaked in antibiotics and those fed with basal diet only. TIS also improved the immune response of the animals when given at a dose of 1.0% or 2.0%, as shown by increased phagocytic, lysozyme, superoxide dismutase, alkaline phosphatase, acid phosphatase, and catalase activities following injection with live Vibrio splendidus. At a dose of 1.0% or 2.0%, TIS significantly enhanced the immune ability (P < 0.05) of the sea cucumbers, but except for lysozyme activity, other immune indices were reduced one day after the animals were injected with Vibrio splendidus. However, the values of these immune indexes were still significantly higher compared to those of the control groups (P < 0.05). Intestinal micro flora counts and high-throughput sequencing showed that dietary TIS could improve the amount of probiotic bacteria, yielding a 6-fold increase in Bacillus and 10-fold increase in Lactobacillus for sea cucumbers fed with 2.0% TIS diet compared to the control. Furthermore, TIS-containing diet also greatly reduced the number of harmful bacteria, with the number of Vibrio in sea cucumbers fed with 1%TIS diet decreased by 67% compared to the control. The results thus indicated that TIS increased the growth of sea cucumbers and enhanced their resistance to V. splendidus infection by improving the immunity of the animals. TIS also improved the gut microbiota profiles of the animals by increasing the probiotics and reducing the harmful bacteria within their guts.

Ficolins and infectious diseases

Ficolins are serum complement lectins, with a structure similar to mannose-binding lectin (MBL) and lung surfactant protein (SP)-A and SP-D. Ficolins activate the lectin complement system and play important roles in host innate immunity. Ficolins are members of the collectin family of proteins, which act as pattern recognition receptors (PRRs). They are soluble oligomeric defense proteins with lectin-like activity, and are able to recognize pathogen-associated molecular patterns (PAMPs), which are carbohydrate molecules on the surface of pathogens, and of apoptotic, necrotic, and malignant cells. Upon binding to their specific PAMPs, ficolins may trigger activation of the immune system either (1) by initiating activation of complement via the lectin pathway, (2) by a primitive type of opsonophagocytosis, or (3) by stimulating secretion of the inflammatory cytokines interferon (IFN)-Γ, interleukin (IL)-17, IL-6, and tumor necrosis factor (TNF)-α, and production of nitric oxide (NO) by macrophages, thus limiting the infection and concurrently orchestrating the subsequent adaptive immune response. Recently, a number of reports have shown that dysfunction or abnormal expression of ficolins may play crucial roles in viral and bacterial diseases and in inflammation. This review summarizes the reports on the roles of ficolins in the infectious diseases, and provides insight into ficolins as novel innate immune therapeutic options to treat these diseases.

Purification, measurement of concentration, and functional complement assay of human ficolins

Ficolins constitute a group of lectins involved in innate immunity. L-Ficolin, H-ficolin, and M-ficolin are present in human serum. The human ficolins differ in carbohydrate-binding specificity, but they have in common the ability to recognize the acetyl group. L-Ficolin and H-ficolin are associated with serine proteases termed MASPs (MBL-associated serine proteases) and their truncated proteins, and the complexes (L/H-ficolin-MASP) activate the lectin pathway of complement upon binding to their ligands. Recombinant M-ficolin is also able to form a complex with MASP, resulting in complement activation. L-Ficolin and H-ficolin can be purified as a complex with MASP from serum by utilizing their binding specificities. These ficolin-MASP complexes have an ability to activate C4. Human ficolins are quantified by ELISA using specific antibodies or ligands.

Structural and functional overview of the lectin complement pathway: its molecular basis and physiological implication

The complement system is an effector mechanism in immunity. It is activated in three ways, the classical, alternative and lectin pathways. The lectin pathway is initiated by the binding of mannose-binding lectin (MBL) or ficolins to carbohydrates on the surfaces of pathogens. In humans, MBL and three types of ficolins (L-ficolin, H-ficolin, and M-ficolin) are present in plasma. Of these lectins, at least, MBL, L-ficolin, and H-ficolin are complexed with three types of MBL-associated serine proteases (MASPs), MASP-1, MASP-2, and MASP-3 and their truncated proteins (MAp44 and sMAP). In the lectin pathway, the lectin-MASP complex (i.e., a complex of lectin, MASPs and their truncated proteins) binds to pathogens, resulting in the activation of C4 and C2 to generate a C3 convertase capable of activating C3. MASP-2 is involved in the activation of C4 and C2. MASP-1 activates C2 and MASP-2. The functions of MASP-3, sMAP, and MAp44 in the lectin pathway remain unknown. MASP-1 and MASP-3 also have a role in the alternative pathway. MBL and ficolins are able to bind to a variety of pathogens depending on their carbohydrate binding specificity, resulting in the activation of the lectin pathway. Deficiencies of the components of the lectin pathway are associated to susceptibility to infection, indicating an important role of the lectin pathway in innate immunity. The lectin-MASP complex is also involved in innate immunity by activating the coagulation system. Recent findings suggest a crucial role of MASP-3 in development.

Swierzko A, Cedzynski M. Cost-effective procedures for genotyping of human FCN2 gene single nucleotide polymorphisms

L-ficolin (ficolin-2) is a complement-activating pattern-recognition lectin taking part in the innate immune response. Both its serum concentration and sugar binding capacity are influenced by single nucleotide polymorphisms (SNP) of the corresponding FCN2 gene. Cost-effective and simple procedures, based on polymerase chain reaction (PCR) or PCR-restriction fragment length polymorphism for an investigation of four FCN2 SNPs are proposed: -64 A > C (rs7865453), -4 A > G (rs17514136; both located in the promoter region), +6359 C > T (rs17549193), +6424 G > T (rs7851696; both in exon 8). Variant alleles of -64 and +6424 (in strong linkage disequlibrium) are known to be associated with low L-ficolin level or activity. In contrast, variant alleles at positions -4 and +6359 (also in strong linkage disequlibrium) correspond to higher values. Since several L-ficolin clinical associations have been reported, FCN2 genotyping seems to be a valuable tool for disease association studies.

The role of MASP-1/3 in complement activation

The complement system, which consists of more than 30 plasma and cell surface proteins, is activated by three pathways: the classical, lectin, and alternative pathways, leading to the generation of opsonins and pathogen destruction. In the lectin pathway, mannose-binding lectin (MBL) and ficolins act as pattern recognition molecules for pathogens, resulting in the activation of MBL-associated serine proteases (MASPs: MASP-1, MASP-2, and MASP-3). Among these proteases, MASP-2 is a key enzyme that cleaves C4 and C2 to assemble a C3 convertase (C4b2a). However, the physiological function of MASP-1 and MASP-3 remains unclear. To investigate the roles of MASP-1 and MASP-3, we generated a MASP-1- and MASP-3-deficient (M1/3 KO) mouse model and found that the deficient mice lacked alternative pathway activation because factor D (Df) remained as a proenzyme in the serum. MASP-1 and MASP-3 were able to convert the proenzyme of Df to an active form in vitro. In addition, MASP-1 was able to activate MASP-2 and MASP-3 as C1r activates C1s. Thus, MASP-1 and MASP-3 seem to be involved in activation of both the lectin and alternative pathways.

Characterization of a gene coding for a putative adenosine deaminase-related growth factor by RNA interference in the basidiomycete Flammulina velutipes

A full-length cDNA coding for a putative adenosine deaminase (Fv-ada) was isolated from the basidiomycete Flammulina velutipes. Fv-ada encodes a polypeptide consisting of 537 amino acid residues, which has a consensus sequence conserved among adenosine deaminase-related growth factors (ADGF) found in several metazoa, including chordates and insects. Fv-ada transcript was detected at all stages of growth in dikaryotic F. velutipes cells, with a peak at the primordial stage. Heterologous expression of Fv-ada in the yeast Pichia pastoris produced recombinant Fv-ADA that catalyzed the conversion of adenosine to inosine. Dikaryotic mycelia from F. velutipes were transformed with the binary plasmid pFungiway-Fv-ada, which was designed to suppress the expression of Fv-ada through RNA interference. The growth rates of the resulting transformants were retarded in response to the degree of suppression, indicating that Fv-ada plays an important role in the mycelial growth of F. velutipes. These results suggested that ADGF could function as growth factors in fungi, as is seen in other eukaryotes.

Expression of Drosophila adenosine deaminase in immune cells during inflammatory response

Extra-cellular adenosine is an important regulator of inflammatory responses. It is generated from released ATP by a cascade of ectoenzymes and degraded by adenosine deaminase (ADA). There are two types of enzymes with ADA activity: ADA1 and ADGF/ADA2. ADA2 activity originates from macrophages and dendritic cells and is associated with inflammatory responses in humans and rats. Drosophila possesses a family of six ADGF proteins with ADGF-A being the main regulator of extra-cellular adenosine during larval stages. Herein we present the generation of a GFP reporter for ADGF-A expression by a precise replacement of the ADGF-A coding sequence with GFP using homologous recombination. We show that the reporter is specifically expressed in aggregating hemocytes (Drosophila immune cells) forming melanotic capsules; a characteristic of inflammatory response. Our vital reporter thus confirms ADA expression in sites of inflammation in vivo and demonstrates that the requirement for ADA activity during inflammatory response is evolutionary conserved from insects to vertebrates. Our results also suggest that ADA activity is achieved specifically within sites of inflammation by an uncharacterized post-transcriptional regulation based mechanism. Utilizing various mutants that induce melanotic capsule formation and also a real immune challenge provided by parasitic wasps, we show that the acute expression of the ADGF-A protein is not driven by one specific signaling cascade but is rather associated with the behavior of immune cells during the general inflammatory response. Connecting the exclusive expression of ADGF-A within sites of inflammation, as presented here, with the release of energy stores when the ADGF-A activity is absent, suggests that extra-cellular adenosine may function as a signal for energy allocation during immune response and that ADGF-A/ADA2 expression in such sites of inflammation may regulate this role.

Factors affecting proliferation and differentiation of Lepidopteran midgut stem cells

Midgut stem cells of last instar larvae and pupae of Heliothis virescens, Lymantria dispar and several other Lepidopteran species have been cultured in vitro and have been induced to proliferate using low titers of ecdysteroids and the 77-Kda peptide fragment, alpha-arylphorin, isolated and identified from pupal fat body tissue. The insulin-related hormone, Bombyxin, also induced mitosis in cultured midgut stem cells; it appeared to be fast-acting and quickly inactivated, while alpha-arylphorin was slower to act and had a longer lasting effect in vitro, indicating different functions for these proliferation agents. Changes in Calcium ion concentration within or outside the cells discretely affected stem cell differentiation, indicating a role for second messenger participation in peptide regulation of this process. Four different peptides (MDFs 1-4) that induced midgut stem cells to differentiate to mature midgut cell types in vitro were isolated and characterized from conditioned media and hemolymph of H. virescens and L. dispar. However, platelet-derived growth factor (PDGF), epidermal growth factor (EGF), and all-trans retinoic acid (RA) from vertebrate sources induced differentiation to non-midgut cell types as well. MDF1 was located in basal areas of columnar cells of midgut epithelium, although MDF2 was observed in all of the cytoplasm of columnar cells and in droplets of antibody positive material in the midgut lumen, suggesting a digestive function as well for this peptide. Anti-MDF-3 stained the central areas of cultured midgut columnar cells and the bases of columnar cells of midgut epithelium in vivo. Midgut secretory cells stained with anti-MDF-4; streams of MFD-4-positive material were observed extending from secretory cells facing the epithelial lumen, and as a layer on the hemolymph-facing side, suggesting an endocrine or paracrine function for this or an immunologically similar peptide.

Structural basis for the growth factor activity of human adenosine deaminase ADA2

Two distinct adenosine deaminases, ADA1 and ADA2, are found in humans. ADA1 has an important role in lymphocyte function and inherited mutations in ADA1 result in severe combined immunodeficiency. The recently isolated ADA2 belongs to the novel family of adenosine deaminase growth factors (ADGFs), which play an important role in tissue development. The crystal structures of ADA2 and ADA2 bound to a transition state analogue presented here reveal the structural basis of the catalytic/signaling activity of ADGF/ADA2 proteins. In addition to the catalytic domain, the structures discovered two ADGF/ADA2-specific domains of novel folds that mediate the protein dimerization and binding to the cell surface receptors. This complex architecture is in sharp contrast with that of monomeric single domain ADA1. An extensive glycosylation and the presence of a conserved disulfide bond and a signal peptide in ADA2 strongly suggest that ADA2, in contrast to ADA1, is specifically designed to act in the extracellular environment. The comparison of catalytic sites of ADA2 and ADA1 demonstrates large differences in the arrangement of the substrate-binding pockets. These structural differences explain the substrate and inhibitor specificity of adenosine deaminases and provide the basis for a rational design of ADA2-targeting drugs to modulate the immune system responses in pathophysiological conditions.

Humoral pattern recognition molecules: mannan-binding lectin and ficolins

Innate immunity comprises a sophisticated network of molecules, which recognize pathogens, and effector molecules, working together to establish a quick and efficient immune response to infectious agents. Complement activation triggered by mannan binding lectin (MBL) or ficolins represents a beautiful example of this network Both MBL and ficolins recognize specific chemical structures on the surface of antigens and pathogens, thus bind to a broad variety of pathogens. Once bound further complement deposition is achieved through a cascade of proteolytic reactions. MBL and ficolin induced complement activation is critical for adequate anti-bacterial, anti-fungal and anti-viral responses. This is well illustrated by numerous and convincing studies that demonstrate associations between MBL deficiency and infections. Recent work has also highlighted that MBL and ficolins recognize self-structures, thus extending the role of these molecules beyond the traditional view of first line defense molecules. It appears that MBL deficiency may modulate the prognosis of inflammatory and autoimmune diseases. What is known about the mechanisms behind this broad scope of activities of MBL and ficolins is discussed in this chapter.

Study of the reactivity of quinohemoprotein alcohol dehydrogenase with heterocycle-pentacyanoferrate(III) complexes and the electron transfer path calculations

The reactivity of alcohol dehydrogenase IIG (ADH IIG) from Pseudomonas putida HK5 with new heterocycle-pentacyanoferrate(III) complexes and hexacyanoferrate(III) was determined at pH 7.2. The pentacyanoferrate(III) complexes contained imidazole, pyrazole, pyridine, their derivatives and 2-aminobenzothiazole as the sixth ligand. The largest reactivity of the complexes with ADH IIG was estimated for the complex containing pyridine. An apparent bimolecular constant (k ox) for this complex was 8.7 × 105 M−1s−1. The lowest value of k ox was estimated for the complex with benzotriazole (k ox = 3.1 × 104 M−1s−1). The investigation of the hexacyanoferrate(III) enzymatic reduction rate at different ionic strength gave a single negative charge of reduced ADH IIG. Docking calculations revealed two binding sites of the complexes in ADH-IIG structure. The first one is located at the entrance to the PQQ pocket, and the second is at the site of cytochrome domain. The calculations of electron transfer (ET) path indicated that the most effective ET takes place from heme to the complex docked at the entrance to the PQQ pocket. This shortest path is constructed of amino acids Ser607 and Cys606.

The extracellular adenosine deaminase growth factor, ADGF/CECR1, plays a role in Xenopus embryogenesis via the adenosine/P1 receptor

Adenosine deaminase-related growth factors (ADGF), also known as CECR1 in vertebrates, are a novel family of growth factors with sequence similarity to classical cellular adenosine deaminase. Although genes for ADGF/CECR1 have been identified in both invertebrates as well as vertebrates, their in vivo functions in vertebrates remain unknown. We isolated cDNA clones for two cerc 1s from Xenopus laevis. Both recombinant Xenopus CECR1s exhibited adenosine deaminase and growth factor activity, and the adenosine deaminase activity was found to be indispensable for growth factor activity. The Xenopus cerc 1s are expressed in the somites, pronephros, eyes, cement gland, neural tube, and neural floor plate of the embryos. Knock-down of these two genes using morpholino oligonucleotides caused a reduction in the body size and abnormalities of the body axis in the Xenopus embryos, accompanied by selective changes in the expression of developmental marker genes. Injection of adenosine, agonists for adenosine/P1 receptors, or adenosine deaminase inhibitor into late gastrula archenteron embryos resulted in developmental defects similar to those caused by morpholino oligonucleotide injection. These results show, for the first time, the involvement of CECR1s via the adenosine/P1 receptors in vertebrate embryogenesis via regulation of extracellular adenosine concentrations.

Molecular characterization of MbADGF, a novel member of the adenosine deaminase-related growth factor in the cabbage armyworm, Mamestra brassicae: the functional roles in the midgut cell proliferation

To clarify the functional mechanism of the adenosine deaminase-related growth factor (ADGF) particularly in the regulation of insect development, the cDNA encoding a homologue of ADGF proteins was cloned from the cabbage armyworm, Mamestra brassicae, named MbADGF. The purified MbADGF recombinant protein stimulated cell proliferation in a dose-dependent manner of SES-MaBr-4 and NIAS-MaBr-93 cell lines that were derived from fat bodies and haemocytes of M. brassicae. The adenosine deaminase activity of MbADGF was detected using adenosine and 2'-deoxyadenosine as substrates. Northern analysis demonstrated that during the larval development the level of MbADGF in the midgut increased. In situ hybridization showed that MbADGF mRNA was expressed in midgut goblet cells and in the apical cytoplasm of columnar cells, which suggests that MbADGF protein may execute its adenosine deaminase activity at the apical cytoplasm of columnar cells to convert adenosine into inosine.

Mannose-binding lectin without the aid of its associated serine proteases alters lipopolysaccharide-mediated cytokine/chemokine secretion from human endothelial cells

Coupling between certain pathogen-associated molecular patterns and corresponding pattern recognition receptors of endothelial cells is important for the mediation of vascular inflammatory responses. Mannose-binding lectin (MBL) recognizes certain carbohydrate structures of microbes and subsequently activates the complement system as well as facilitates the phagocytosis of targets. We investigated whether MBL can intervene in the interaction between bacterial lipopolysaccharide (LPS) and endothelial cells to modulate subsequent inflammatory responses. In response to LPS, human umbilical vein endothelial cells (HUVEC) produced various cytokines/chemokines. Addition of the purified human MBL/MBL-associated serine proteases (MASP) complex or recombinant human MBL enhanced LPS-mediated cytokine/chemokine secretion by HUVEC, including interleukin-8 (IL-8), IL-6 and monocyte chemoattractant protein-1 in a dose-dependent manner. This enhancing effect was ameliorated by the addition of anti-MBL antibody or mannan. Among the cytokines/chemokines we analysed, IL-6 showed the greatest increase of secretion in the presence of native MBL/MASP complex or recombinant MBL. MBL, regardless of its association with MASP, alters LPS-mediated cytokine/chemokine secretion of HUVEC. Besides the well-known functions of MBL, to activate the lectin-complement pathway and to facilitate clearance of targets, alteration of cytokine/chemokine secretion may provide an additional role for MBL in modulating vascular inflammation.

Involvement of insect-derived growth factor (IDGF) in the cell growth of an embryonic cell line of flesh fly

Insect-derived growth factor (IDGF) is the first adenosine deaminase-related growth factor (ADGF) purified from the conditioned medium of NIH-Sape-4, an embryonic cell line of Sarcophaga peregrina (flesh fly). Here we show the requirement of IDGF for the growth of NIH-Sape-4 cells. Growth factor activity was abolished by adsorption of IDGF from the conditioned medium of NIH-Sape-4 cells. In addition, knockdown of IDGF gene expression by RNA interference (RNAi) significantly reduced IDGF secretion from the cells following cell growth inhibition. The IDGF gene was strongly expressed in the hemocytes, and IDGF increased the viability of the larval hemocytes. These data provide evidence that IDGF is required for the growth of NIH-Sape-4 cells and possibly for hemocyte viability.

Isolation and analysis of genes specifically expressed during fruiting body development in the basidiomycete Flammulina velutipes by fluorescence differential display

Using fluorescence differential display, cDNAs specifically expressed at the primordial stage of fruiting body development were isolated from the basidiomycete, Flammulina velutipes. Seventy-five cDNAs were sequenced and compared with the amino-acid sequences of proteins in the database by BLASTX search. Significant similarity was found for 29 cDNAs coding for proteins with known function, GTP-binding protein, growth factor, ubiquitin-proteasome, cytochrome P450 and hydrophobin, all of which would be associated with fruiting body development. Seventeen cDNAs were not similar to proteins in the database and may represent unique genes that play specific roles in the process of fruiting in F. velutipes.

Phylogenetic analysis reveals a novel protein family closely related to adenosine deaminase

Adenosine deaminase (ADA) is a well-characterized enzyme involved in the depletion of adenosine levels. A group of proteins with similarity to ADA, the adenosine deaminase-related growth factors (ADGF; known as CECR1 in vertebrates), has been described recently in various organisms. We have determined the phylogenetic relationships of various gene products with significant amino acid similarity to ADA using parsimony and Bayesian methods, and discovered a novel paralogue, termed ADA-like (ADAL). The ADGF proteins share a novel amino acid motif, "MPKG," within which the proline and lysine residues are also conserved in the ADAL and ADA subfamilies. The significance of this new domain is unknown, but it is located just upstream of two ADA catalytic residues, of which all eight are conserved among the ADGF and ADAL proteins. This conservation suggests that ADGF and ADAL may share the same catalytic function as ADA, which has been proven for some ADGF members. These analyses also revealed that some genes previously thought to be classic ADAs are instead ADAL or ADGFs. We here define the ADGF, ADAL, ADA, adenine deaminase (ADE), and AMP deaminase (AMPD) groups as subfamilies of the adenyl-deaminase family. The availability of genomic data for the members of this family allowed us to reconstruct the intron evolution within the phylogeny and strengthen the introns-late hypothesis of the synthetic introns theory. This study shows that ADA activity is clearly more complex than once thought, perhaps involving a delicately balanced pattern of temporal and spatial expression of a number of paralogous proteins.

Transgenic expression of CECR1 adenosine deaminase in mice results in abnormal development of heart and kidney

Cat eye syndrome is a rare developmental defect associated with duplication of chromosome 22q11. The patients demonstrate specific abnormalities of heart, kidney, and eye. Here we attempted to produce a model for this defect by expressing CECR1 adenosine deaminase, a gene duplicated in cat eye syndrome patients, in mice. The transgenic mice expressed CECR1 under the control of either beta-actin promoter for ubiquitous expression or myosin heavy chain for heart-specific expression. The transgenics expressing CECR1 in the heart demonstrated high rate of embryonic and neonatal lethality. The mice from all the lines examined showed enlargement of the heart. Abnormalities of the kidney and eye were also detected in mice expressing CECR1 under control of the actin promoter.

A role for adenosine deaminase in Drosophila larval development

Adenosine deaminase (ADA) is an enzyme present in all organisms that catalyzes the irreversible deamination of adenosine and deoxyadenosine to inosine and deoxyinosine. Both adenosine and deoxyadenosine are biologically active purines that can have a deep impact on cellular physiology; notably, ADA deficiency in humans causes severe combined immunodeficiency. We have established a Drosophila model to study the effects of altered adenosine levels in vivo by genetic elimination of adenosine deaminase-related growth factor-A (ADGF-A), which has ADA activity and is expressed in the gut and hematopoietic organ. Here we show that the hemocytes (blood cells) are the main regulator of adenosine in the Drosophila larva, as was speculated previously for mammals. The elevated level of adenosine in the hemolymph due to lack of ADGF-A leads to apparently inconsistent phenotypic effects: precocious metamorphic changes including differentiation of macrophage-like cells and fat body disintegration on one hand, and delay of development with block of pupariation on the other. The block of pupariation appears to involve signaling through the adenosine receptor (AdoR), but fat body disintegration, which is promoted by action of the hemocytes, seems to be independent of the AdoR. The existence of such an independent mechanism has also been suggested in mammals.

Adenosine deaminase is critically important to survival; congenital deficiency in humans leads to severe immunodeficiency. Here, the authors demonstrate that adenosine deaminase deficiency in flies results in severe developmental defects.

The emerging role of adenosine deaminases in insects

Adenosine deaminases catalyze the deamination of adenosine and deoxyadenosine into their respective inosine nucleosides. Recent sequencing of the genomes of several model organisms and human reveal that Metazoa usually have more than one adenosine deaminase gene. A deficiency in the gene encoding the major enzyme is lethal in mouse and Drosophila and leads to severe combined deficiency (SCID) in human. In these organisms, enzyme deficiency causes increased adenosine/deoxyadenosine concentration in body fluids and some organs. Elevated levels of adenosine and deoxyadenosine are toxic to certain mammalian and insect cells, and it was shown for human and mouse that it is a primary cause of pathophysiological effects. Data suggest that the major role of adenosine deaminases in various taxa is the protection of tissues against increased levels of adenosine and deoxyadenosine. This review also discusses potential roles of adenosine deaminases in Drosophila metamorphosis and the employment of a Drosophila model to study the cell-specific toxicity of elevated nucleoside levels.

BOMBYXIN STIMULATES PROLIFERATION OF CULTURED STEM CELLS DERIVED FROM HELIOTHIS VIRESCENS AND MAMESTRA BRASSICAE LARVAE1

Bombyxin stimulated proliferation of cultured midgut stem cells that were derived from two noctuiid moth larvae, Heliothis virescens and Mamestra brassicae. Bombyxin exhibited the highest activity at 10(-12) M. The number of cells increased for 3 d after the addition of bombyxin. Although a single addition of bombyxin did not maintain proliferation, a second addition, made 3 d after the first treatment, retained the effect. Results suggest that the decline of effect after the first addition was not due to the loss of sensitivity of the cultured cells but to the loss of effect of the growth factor added. Addition of bombyxin at more than 10(-10) M was less effective. Bombyxin did not affect the number of cultured midgut cells without pupal fat body extract (FBX). The data suggest that FBX contains the factors that maintain sensitivity of midgut cells to proliferate in the presence of bombyxin. Bombyxin must be a unique growth factor that stimulates proliferation of midgut stem cells in vitro from lepidopteran larvae.

A novel lectin with a fibrinogen-like domain and its potential involvement in the innate immune response of Armigeres subalbatus against bacteria

Mosquitoes have an efficient cellular innate immune response that includes phagocytosis of microbial pathogens and encapsulation of metozoan parasites. In this study, we describe a novel lectin in the mosquito, Armigeres subalbatus (aslectin or AL-1). The 1.27 kb cDNA clone for the AL-1 gene (AL-1) encodes a 279 deduced amino acid sequence that contains a C-terminal fibrinogen-like domain. AL-1 is transcribed in all life stages. AL-1 mainly exists in the haemolymph of adult female mosquitoes, and is upregulated following both Escherichia coli and Micrococcus luteus challenge. AL-1 specifically recognizes N-acetyl-d-glucosamine and is able to bind both E. coli and M. luteus. These results suggest that AL-1 might function as a pattern recognition receptor in the immune response in Ar. subalbatus.

The lectin-complement pathway--its role in innate immunity and evolution

Innate immunity was formerly thought to be a non-specific immune response characterized by phagocytosis. However, innate immunity has considerable specificity and is capable of discriminating between pathogens and self. Recognition of pathogens is mediated by a set of pattern recognition receptors, which recognize conserved pathogen-associated molecular patterns (PAMPs) shared by broad classes of microorganisms, thereby successfully defending invertebrates and vertebrates against infection. Lectins, carbohydrate-binding proteins, play an important role in innate immunity by recognizing a wide range of pathogens. Mannose-binding lectin (MBL) and ficolin are lectins composed of a lectin domain attached to collagenous region. However, they use a different lectin domain: a carbohydrate recognition domain (CRD) is responsible for MBL and a fibrinogen-like domain for ficolin. These two collagenous lectins are pattern recognition receptors, and upon recognition of the infectious agent, they trigger the activation of the lectin-complement pathway through attached serine proteases, MBL-associated serine proteases (MASPs). A similar lectin-based complement system, consisting of the lectin-protease complex and C3, is present in ascidians, our closest invertebrate relatives, and functions in an opsonic manner. We isolated several lectins homologous to MBLs and ficolins and several MASPs in invertebrates and lower vertebrates, and herein we discuss the molecular evolution of these molecules. Based on these findings, it seems likely that the complement system played a pivotal role in innate immunity before the evolution of an acquired immune system in jawed vertebrates.

The classical and alternative pathways of complement activation play distinct roles in spontaneous C3 fragment deposition and membrane attack complex (MAC) formation on human B lymphocytes

The contributions of the classical (CP) and alternative (AP) pathways of complement activation to the spontaneous deposition of C3 fragments and the formation of membrane attack complexes (MAC) on human B lymphocytes, were assessed by incubating peripheral blood mononuclear cells with autologous serum in the absence and presence of selective inhibitors of the AP and CP, respectively. While the total amount of C3 fragments deposited was relatively unaffected by blocking either pathway individually, deposition was virtually abrogated by their combined blockade. A marked difference was observed, however, in the nature of the fragments deposited as a result of CP and AP activation: C3b fragments deposited via the CP were extensively ( approximately 90%) converted to the terminal degradation product, C3dg, whereas about 50% of those deposited by the AP persisted as C3b/iC3b fragments. The extent of MAC formation was also found to be highly pathway dependent, with the AP being about 15-fold more efficient at initiating this process than the CP. A model accounting for the effectiveness of the AP in both preserving C3 fragment integrity and initiating MAC is presented.

In vitro studies of hematopoiesis in the silkworm: cell proliferation in and hemocyte discharge from the hematopoietic organ

The lepidopteran hematopoietic process is poorly understood. We therefore examined the fundamental properties of hematopoiesis in the silkworm Bombyx mori using hematopoietic organ culture. In a medium containing larval plasma taken from the fourth day of the final larval stadium, over 50,000 hemocytes per hematopoietic organ were discharged within 48 h, with the number of cells comprising the hematopoietic organ simultaneously increasing from approximately 20,000 to 40,000. However, in the absence of plasma, cell numbers comprising the hematopoietic organ were unchanged and the number of discharged cells was much less. Hematopoietic organs cultured with plasma showed strong mitotic indices in a BrdU incorporation assay, but did not when cultured without plasma, indicating that plasma contains hematopoietic factor(s). The hematopoietic stimulation ability of larval plasma was observed from the last day of the penultimate larval stadium to the prepupal stage. The response of the hematopoietic organs to larval plasma was highest at the beginning of the final larval stadium and decreased with aging. Most cells discharged from the hematopoietic organ were plasmatocytes and prohemocytes, irrespective of location and developmental stage. Using this in vitro culture method, we tested the effects of 20-hydroxyecdysone (20E) and juvenile hormone-I (JH-I) on B. mori hematopoiesis. 20E showed a weak, but significant, hematopoietic activity, whereas JH-I did not, suggesting that a part of larval hematopoiesis is endocrinally regulated.

Peptide products of the atrial gland are not water-borne reproductive pheromones during egg laying in Aplysia

Mate attraction in Aplysia involves long-distance water-borne signaling via the secretion of the peptide pheromone attractin from the exocrine albumen gland during egg laying. Previous studies have shown that a second exocrine organ, the atrial gland, produces abundant egg-laying hormone (ELH) precursor-related peptides and mollusk-derived growth factor (MDGF), and crude extracts of the atrial gland are attractive in T-maze attraction assays. However, it is not known whether these peptides and proteins are secreted during egg laying. In this report, seawater eluates of freshly laid egg cordons were concentrated and fractionated by C18 RP-HPLC, and the resulting major peaks were examined by amino acid compositional analysis, microsequence analysis, and electrospray mass spectrometry. Concentrated egg cordon eluates were also examined by immunoblot analysis using anti-MDGF antisera as probe. The combined data demonstrated that the atrial gland of Aplysia californica does not secrete detectable levels of either ELH precursor-related peptides or MDGF during egg laying. Although the atrial gland is the last major exocrine organ to make contact with eggs before they are laid, the gland does not appear to secrete water-borne peptide pheromones during egg laying.

Molecular cloning and characterization of novel ficolins from Xenopus laevis

Ficolins are proteins characterized by the presence of collagen- and fibrinogen-like domains. Two of three human ficolins, L-ficolin and H-ficolin, are serum lectins and are thought to play crucial roles in host defense through opsonization and complement activation. To elucidate the evolution of ficolins and the primordial complement lectin pathway, we cloned four ficolin cDNAs from Xenopus laevis, termed Xenopus ficolin (XeFCN) 1, 2, 3 and 4. The deduced amino acid sequences of the four ficolins revealed the conserved collagen- and fibrinogen-like domains. The full sequences of the four ficolins showed a 42-56% identity to human ficolins, and 60-83% between one another. Northern blots showed that XeFCN1 was expressed mainly in liver, spleen and heart, and XeFCN2 and XeFCN4 mainly in peripheral blood leukocytes, lung and spleen. We isolated ficolin proteins from Xenopus serum by affinity chromatography on N-acetylglucosamine-agarose, followed by ion-exchange chromatography. The final eluate showed polymeric bands composed of two components of 37 and 40 kDa. The N-terminal amino acid sequences and treatment with endoglycosidase F showed that the two bands are the same XeFCN1 protein with different masses of N-linked sugar. The polymeric form of the two types of XeFCN1 specifically recognized GlcNAc and GalNAc residues. These results suggest that like human L-ficolin, XeFCN1 functions in the circulation through its lectin activity.

Peptides that elicit midgut stem cell differentiation isolated from chymotryptic digests of hemolymph from Lymantria dispar pupae

Isolated stem cells of Heliothis virescens, cultured in vitro, were induced to differentiate by Midgut Differentiation Factors 3 and 4. These were peptides identified from a chymotrypsin digest of hemolymph taken from newly pupated Lymantria dispar. Partial purification was obtained by filtration through size exclusion filters. The most active preparation was subsequently subjected to a series of 3 Reverse Phase-HPLC procedures. Partial sequences of the peptides were identified via automated Edman degradation as the nanomers EEVVKNAIA-OH (MDF 3) and ITPTSSLAT-OH (MDF 4). These sequences were commercially synthesized. The synthetic compounds proved active in a dose-dependent manner. Stem cells responded to synthetic MDF 3 and MDF 4 as they did to previously identified peptides MDF 1 and 2, which have quite different amino acid sequences. All of the 4 MDFs administered singly induced statistically similar differentiation responses at 2 x 10(-8), 2 x 10(-9), and 2 x 10(-10) M. However, pairs of the 4 MDFs produced even more differentiation, the same response as one alone, no response, or were inhibitory, dependent on the MDF pair and its concentration. The data suggests complicated receptor interactions.

Crystal structure of imaginal disc growth factor-2. A member of a new family of growth-promoting glycoproteins from Drosophila melanogaster

Imaginal disc growth factor-2 (IDGF-2) is a member of a recently described family of Drosophila melanogaster-soluble polypeptide growth factors that promote cell proliferation in imaginal discs. Although their precise mode of action has not been established, IDGFs cooperate with insulin in stimulating the growth of imaginal disc cells. We report the crystal structure of IDGF-2 at 1.3-A resolution. The structure shows the classical (betaalpha)(8) barrel-fold of family 18 glycosyl hydrolases, with an insertion of an alpha + beta domain similar to that of Serratia marcescens chitinases A and B. However, amino acid substitutions in the consensus catalytic sequence of chitinases give IDGF-2 a less negatively charged environment in its putative ligand-binding site and preclude the nucleophilic attack mechanism of chitin hydrolysis. Particularly important is the replacement of Glu by Gln at position 132, which has been shown to abolish enzymatic activity in chitinases. Nevertheless, a modest conservation of residues that participate in oligosaccharide recognition suggests that IDGF-2 could bind carbohydrates, assuming several conformational changes to open the partially occluded binding site. Thus, IDGFs may have evolved from chitinases to acquire new functions as growth factors, interacting with cell surface glycoproteins implicated in growth-promoting processes, such as the Drosophila insulin receptor.

Adenosine deaminase-related growth factors stimulate cell proliferation in Drosophila by depleting extracellular adenosine

We describe a protein family in Drosophila containing six adenosine deaminase-related growth factors (ADGFs), which are homologous to a mitogenic growth factor discovered in conditioned medium from cells of a different fly species, Sarcophaga. Closely related proteins have been identified in other animals, and a human homolog is implicated in the genetic disease Cat-Eye Syndrome. The two most abundantly expressed ADGFs in Drosophila larvae are ADGF-A, which is strongly expressed in the gut and lymph glands, and ADGF-D, which is mainly expressed in the fat body and brain. Recombinant ADGF-A and ADGF-D are active adenosine deaminases (ADAs), and they cause polarization and serum-independent proliferation of imaginal disk and embryonic cells in vitro. The enzymatic activity of these proteins is required for their mitogenic function, making them unique among growth factors. A culture medium prepared without adenosine, or depleted of adenosine by using bovine ADA, also stimulates proliferation of imaginal disk cells, and addition of adenosine to this medium inhibits proliferation. Thus ADGFs secreted in vivo may control tissue growth by modulating the level of extracellular adenosine.

Molecular studies of the molluscan response to digenean infection

A classical body of knowledge regarding molluscan immunobiology has developed over the years that indicates an important role for both soluble hemolymph proteins and hemocytes in internal defense. The incorporation of powerful molecular approaches into the toolkit of the molluscan immunobiologist holds considerable promise for allowing a more precise description of the molecules and processes involved. Recent discoveries indicate that the molluscan internal defense system has components that are simultaneously both tantalizingly similar to, and different from, molecules functioning in a defense context in other phyla. Study of molecular components of the internal defense systems of molluscs promises to be a rewarding and surprising field.

Characterization of the adenosine deaminase-related growth factor (ADGF) gene family in Drosophila

A novel family of growth factors, with sequence similarity to adenosine deaminase, has been identified in various organisms including flesh fly, tsetse fly, sand fly, mollusk and human. The human homologue, CECR1, is a candidate gene for the genetic disorder cat eye syndrome. Here, we describe six members of this growth factor family in Drosophila and two in vertebrates. The six Drosophila genes, named adenosine deaminase-related growth factors (ADGF), are found at three different chromosomal locations, with one singleton, two in an inverted orientation, and three in a tandem arrangement. These genes show distinct patterns of expression as measured by RT-PCR and Northern blots, indicating gene-specific function. The presence of six ADGF genes in the Drosophila genome suggests that gene duplication and divergence has been important for these growth factors in insect development. Phylogenetic analysis of the 14 extant ADGF-like gene products shows there are at least three major groups, two of which are found in Drosophila. The third appears specific to the vertebrate line. Seven gene duplications are inferred among the ADGF-like genes, most of which occurred long before the origin of Drosophila. Our analysis predicts the existence of several other unsampled ADGF-like genes, both within the species examined here, and in other related invertebrates.

Adenosine deaminase activity of insect-derived growth factor is essential for its growth factor activity

Insect-derived growth factor (IDGF) was originally isolated from conditioned medium of NIH-Sape-4 cells derived from flesh fly embryos. Here we demonstrated that IDGF has adenosine deaminase activity. The substrate specificity of IDGF was similar to that of the mammalian cytoplasmic adenosine deaminase. The adenosine deaminase activity of IDGF was shown to be indispensable for its growth factor activity toward NIH-Sape-4 cells. We found that there are specific binding sites for IDGF on the surface of NIH-Sape-4 cells and that it binds to these sites with a K(d) value of 2.4 x 10(-10) m. We propose that the cell surface binding sites for IDGF are specific receptors modified with an adenosine moiety. When IDGF binds to these receptors, it may deaminate the adenosine moiety, and this process may be prerequisite for the signal transduction via this receptor.

Pyrroloquinoline quinone (PQQ) and quinoprotein enzymes

This review summarises the characteristics, identification, and measurement of pyrroloquinoline quinone, the prosthetic group of bacterial quinoprotein dehydrogenases whose structures, mechanisms, and electron transport functions are described in detail. Type I alcohol dehydrogenase includes the "classic" methanol dehydrogenase; its x-ray structure and mechanism are discussed in detail. It is likely that its mechanism involves a direct hydride transfer rather than a mechanism involving a covalent adduct. The x-ray structure of a closely related ethanol dehydrogenase is also described. The type II alcohol dehydrogenase is a soluble quinohaemoprotein, having a C-terminal extension containing haem C, which provides an excellent opportunity for the study of intraprotein electron transfer processes. The type III alcohol dehydrogenase is similar but it has two additional subunits (one of which is a multihaem cytochrome c) bound in an unusual way to the periplasmic membrane. One type of glucose dehydrogenase is a soluble quinoprotein whose role in energy transduction is uncertain. Its x-ray structure (in the presence and absence of substrate) is described together with the detailed mechanism, which also involves a direct hydride transfer. The more widely distributed glucose dehydrogenases are integral membrane proteins, bound to the membrane by transmembrane helices at the N-terminus.