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

Inborn Errors of Purine Salvage and Catabolism

Cellular purine nucleotides derive mainly from de novo synthesis or nucleic acid turnover and, only marginally, from dietary intake. They are subjected to catabolism, eventually forming uric acid in humans, while bases and nucleosides may be converted back to nucleotides through the salvage pathways. Inborn errors of the purine salvage pathway and catabolism have been described by several researchers and are usually referred to as rare diseases. Since purine compounds play a fundamental role, it is not surprising that their dysmetabolism is accompanied by devastating symptoms. Nevertheless, some of these manifestations are unexpected and, so far, have no explanation or therapy. Herein, we describe several known inborn errors of purine metabolism, highlighting their unexplained pathological aspects. Our intent is to offer new points of view on this topic and suggest diagnostic tools that may possibly indicate to clinicians that the inborn errors of purine metabolism may not be very rare diseases after all.

Imaginal disc growth factor is involved in melanin synthesis and energy metabolism in Bombyx mori

The imaginal disc growth factor (IDGF), belonging to the glycoside hydrolase 18 family, plays an important role in various physiological processes in insects. However, the detail physiological function of IDGF is still unclear. In this study, transcriptome analysis was performed on the fatbody isolated from staged control and BmIDGF mutant silkworm larvae. Transcriptional profiling revealed that the absence of BmIDGF significantly affected differentially expressed genes involved in tyrosine and purine metabolism, as well as multiple energy metabolism pathways, including glycolysis, galactose, starch, and sucrose metabolism. The interruption of BmIDGF caused similar and specific gene expression changes to male and female fatbody. Furthermore, a genome-scale metabolic network integrating metabolomic and transcriptomic datasets revealed 11 pathways significantly altered at the transcriptional and metabolic levels, including amino acid, carbohydrate, uric acid metabolism pathways, insect hormone biosynthesis, and ABC transporters. In conclusion, this multiomics analysis suggests that IDGF is involved in gene-metabolism interactions, revealing its unique role in melanin synthesis and energy metabolism. This study provides new insights into the physiological function of IDGF in insects.

Characterization and Expression Analysis of Mollusk-like Growth Factor: A Secreted Protein Involved in Pacific Abalone Embryonic and Larval Development

Simple Summary

The Pacific abalone, Haliotis discus hannai, is a gastropod mollusk in high demand, which is extensively cultured in many Asian countries. The growth and development of Pacific abalone depend on the activation of growth factors and other growth-regulating proteins. Growth factors are secreted, biologically active molecules that stimulate cell growth through signal transduction pathways. The mollusk-like growth factor (MLGF) is a mollusk specific growth factor in the adenosine deaminase related growth factor subfamily having a conserved adenosine deaminase (ADA) domain. Molecular functions of this growth factor include adenosine deaminase activity, growth factor activity, and zinc binding activity. For this growth factor activity, enzymatic activity (ADA activity) that converts adenosine to inosine to stimulate cell growth is essential. As abalone aquaculture completely depends on hatchery-produced seed, proper embryonic and larval development is essential, and MLGF is one of the main growth factors that can regulate this activity. In Pacific abalone, higher expression of Hdh-MLGF mRNA in the embryonic and larval development stages is an indication of higher production of adenosine and increases the growth factor activity that stimulates embryonic and larval cell growth through signal transduction pathways.

Abstract

Growth factors are mostly secreted proteins that play key roles in an organism’s biophysical processes through binding to specific receptors on the cell surface. The mollusk-like growth factor (MLGF) is a novel cell signaling protein in the adenosine deaminase-related growth factor (ADGF) subfamily. In this study, the MLGF gene was cloned and characterized from the digestive gland tissue of Pacific abalone and designated as Hdh-MLGF. The transcribed full-length sequence of Hdh-MLGF was 1829 bp long with a 1566 bp open reading frame (ORF) encoding 521 amino acids. The deduced amino acid sequence contained a putative signal peptide and two conserved adenosine deaminase domains responsible for regulating molecular function. Fluorescence in situ hybridization localized Hdh-MLGF in the submucosa layer of digestive tubules in the digestive gland. The mRNA expression analysis indicated that Hdh-MLGF expression was restricted to the digestive gland in the adult Pacific abalone. However, Hdh-MLGF mRNA expressions were observed in all stages of embryonic and larval development, suggesting Hdh-MLGF might be involved in the Pacific abalone embryonic and larval development. This is the first study describing Hdh-MLGF and its involvement in the Pacific abalone embryonic and larval development.

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.

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.

Characteristics common to a cytokine family spanning five orders of insects

Growth-blocking peptide (GBP) is a member of an insect cytokine family with diverse functions including growth and immunity controls. Members of this cytokine family have been reported in 15 species of Lepidoptera, and we have recently identified GBP-like peptides in Diptera such as Lucilia cuprina and Drosophila melanogaster, indicating that this peptide family is not specific to Lepidoptera. In order to extend our knowledge of this peptide family, we purified the same family peptide from one of the tenebrionids, Zophobas atratus,(1) isolated its cDNA, and sequenced it. The Z. atratus GBP sequence together with reported sequence data of peptides from the same family enabled us to perform BLAST searches against EST and genome databases of several insect species including Coleoptera, Diptera, Hymenoptera, and Hemiptera and identify homologous peptide genes. Here we report conserved structural features in these sequence data. They consist of 19-30 amino acid residues encoded at the C terminus of a 73-152 amino acid precursor and contain the motif C-x(2)-G-x(4,6)-G-x(1,2)-C-[KR], which shares a certain similarity with the motif in the mammalian EGF peptide family. These data indicate that these small cytokines belonging to one family are present in at least five insect orders.

Impact of uremic environment on peritoneum: a proteomic view

Peritoneal morphology and function are abnormal in uremia patients, but the contributing mechanisms are unclear. Here we attempted to characterize the protein targets that may be related to peritoneal change in patients with uremia and have not exposed to peritoneal dialysis fluid. Protein profiles of peritoneal fluids collected from patients with uremia and patients with normal renal function receiving laparoscopic cholecystectomy were displayed by two-dimensional gel electrophoresis (2-DE). Altered protein spots were excised and subjected to tryptic digestion followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Sixteen 2-DE protein spots were altered between two groups. Western blots confirmed that kininogen-1, apoptosis inhibitor 2, cat eye syndrome critical region protein 1, and apolipoprotein A-I had higher expression levels in the uremia samples. In contrast, synaptic vesicle 2-related protein, glial fibrillary acidic protein, and envelope glycoprotein (C2-V5 region) showed lower levels. The increased expression may result from a change in the permeability of the peritoneal membrane to middle-sized proteins or peritoneal inflammation with proteins sloughing off. All the identified proteins may provide a novel understanding of peritoneal changes caused by uremic toxins and may function as biomarkers or drug targets.

Large-scale label-free quantitative proteomics of the pea aphid-Buchnera symbiosis

Many insects are nutritionally dependent on symbiotic microorganisms that have tiny genomes and are housed in specialized host cells called bacteriocytes. The obligate symbiosis between the pea aphid Acyrthosiphon pisum and the γ-proteobacterium Buchnera aphidicola (only 584 predicted proteins) is particularly amenable for molecular analysis because the genomes of both partners have been sequenced. To better define the symbiotic relationship between this aphid and Buchnera, we used large-scale, high accuracy tandem mass spectrometry (nanoLC-LTQ-Orbtrap) to identify aphid and Buchnera proteins in the whole aphid body, purified bacteriocytes, isolated Buchnera cells and the residual bacteriocyte fraction. More than 1900 aphid and 400 Buchnera proteins were identified. All enzymes in amino acid metabolism annotated in the Buchnera genome were detected, reflecting the high (68%) coverage of the proteome and supporting the core function of Buchnera in the aphid symbiosis. Transporters mediating the transport of predicted metabolites were present in the bacteriocyte. Label-free spectral counting combined with hierarchical clustering, allowed to define the quantitative distribution of a subset of these proteins across both symbiotic partners, yielding no evidence for the selective transfer of protein among the partners in either direction. This is the first quantitative proteome analysis of bacteriocyte symbiosis, providing a wealth of information about molecular function of both the host cell and bacterial symbiont.

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.

Evolutionary origins of the purinergic signalling system

Purines appear to be the most primitive and widespread chemical messengers in the animal and plant kingdoms. The evidence for purinergic signalling in plants, invertebrates and lower vertebrates is reviewed. Much is based on pharmacological studies, but important recent studies have utilized the techniques of molecular biology and receptors have been cloned and characterized in primitive invertebrates, including the social amoeba Dictyostelium and the platyhelminth Schistosoma, as well as the green algae Ostreococcus, which resemble P2X receptors identified in mammals. This suggests that contrary to earlier speculations, P2X ion channel receptors appeared early in evolution, while G protein-coupled P1 and P2Y receptors were introduced either at the same time or perhaps even later. The absence of gene coding for P2X receptors in some animal groups [e.g. in some insects, roundworms (Caenorhabditis elegans) and the plant Arabidopsis] in contrast to the potent pharmacological actions of nucleotides in the same species, suggests that novel receptors are still to be discovered.

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.

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.

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.

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.

Effects of a fat body extract on larval midgut cells and growth of lepidoptera

Treatment with fat body extract (FBX) from pupae of the tobacco hornworm, Manduca sexta, caused mortality in larvae of two pest lepidopterans, the gypsy moth, Lymantria dispar, and the cotton leafworm, Spodoptera littoralis. In FBX-treated larvae, the feeding rate was depressed, causing reduced weight gain and then larval death. Their midgut showed formation of multicellular layers of midgut epidermis, indicating stem-cell hyperplasia. Hence, the integument of FBX-treated larvae had a double cuticle, indicating induction of premature molting. But radioimmunoassay measurements confirmed that the amount of ecdysteroids in FBX was too low to be responsible for the molt-inducing effects observed after treatment with FBX. With midgut stem cell cultures in vitro, addition of FBX to the culture medium stimulated cell proliferation and differentiation in a concentration-dependent manner. This effect was compared with those of insect molting hormones, ecdysone and 20-hydroxyecdysone; an ecdysteroid agonist, RH-2485; and a purified protein from FBX (multiplication factor). This article describes the mode of action of FBX and possible interplay between fat body factor(s) and insect hormones in the development and metamorphosis of the insect midgut.