Race: a Drosophila homologue of the angiotensin converting enzyme

fos genes in mainly invertebrate model systems: A review of commonalities and some diversities

fos genes, transcription factors with a common basic region and leucine zipper domains binding to a consensus DNA sequence (TGA{}TCA), are evolutionarily conserved in eukaryotes. Homologs can be found in many different species from yeast to vertebrates. In yeast, the homologous GCN4 gene is required to mediate "emergency" situations like nutrient deprivation and the unfolded protein response. The C. elegans homolog fos-1 is required for reproduction and vulval development, as well as in adult homeostasis. In Drosophila melanogaster, there is also a sole fos homolog: the gene kayak, with five isoforms. The kayak locus has been studied in detail. It was originally described as embryonic lethal with a "dorsal open" phenotype. Since then, kayak has been shown to be required for oocyte maturation and as a source for piRNA; for early dorsoventral specification, macrophage function, dorsal closure, endoderm differentiation, and finally during metamorphosis in wing and eye-antennal development. In mammals there are multiple fos loci, each one with alternative splicing giving rise to multiple isoforms. Overall, mammalian fos genes are required for bone, cartilage and tooth formation, and in some instances for placental angiogenesis and retinal function. We review here mainly what is known about fos function in invertebrate model systems, especially during embryogenesis. We propose that fos genes, evolutionarily conserved transcription factors, evolved early during eukaryotic development, and from its inception as part of an environmental stress response machinery, were co-opted several times during development to regulate processes that may require similar cellular responses.

A simple MiMIC-based approach for tagging endogenous genes to visualise live transcription in Drosophila

Live imaging of transcription in the Drosophila embryo using the MS2 or PP7 systems is transforming our understanding of transcriptional regulation. However, insertion of MS2/PP7 stem-loops into endogenous genes requires laborious CRISPR genome editing. Here, we exploit the previously described Minos-mediated integration cassette (MiMIC) transposon system in Drosophila to establish a method for simply and rapidly inserting MS2/PP7 cassettes into any of the thousands of genes carrying a MiMIC insertion. In addition to generating a variety of stem-loop donor fly stocks, we have made new stocks expressing the complementary coat proteins fused to different fluorescent proteins. We show the utility of this MiMIC-based approach by MS2/PP7 tagging of endogenous genes and the long non-coding RNA roX1, then imaging their transcription in living embryos. We also present live transcription data from larval brains, the wing disc and ovary, thereby extending the tissues that can be studied using the MS2/PP7 system. Overall, this first high-throughput method for tagging mRNAs in Drosophila will facilitate the study of transcription dynamics of thousands of endogenous genes in a range of Drosophila tissues.

Control of aging by the renin–angiotensin system: a review of C. elegans, Drosophila, and mammals

The free-living, non-parasitic nematode Caenorhabditis elegans is a premier model organism for the study of aging and longevity due to its short lifespan, powerful genetic tools, and conservation of fundamental mechanisms with mammals. Approximately 70 percent of human genes have homologs in C. elegans, including many that encode proteins in pathways that influence aging. Numerous genetic pathways have been identified in C. elegans that affect lifespan, including the dietary restriction pathway, the insulin/insulin-like growth factor (IGF) signaling pathway, and the disruption of components of the mitochondrial electron transport chain. C. elegans is also a powerful system for performing drug screens, and many lifespan-extending compounds have been reported; notably, several FDA-approved medications extend the lifespan in C. elegans, raising the possibility that they can also extend the lifespan in humans. The renin–angiotensin system (RAS) in mammals is an endocrine system that regulates blood pressure and a paracrine system that acts in a wide range of tissues to control physiological processes; it is a popular target for drugs that reduce blood pressure, including angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs). Emerging evidence indicates that this system influences aging. In C. elegans, decreasing the activity of the ACE homolog acn-1 or treatment with the ACE-inhibitor Captopril significantly extends the lifespan. In Drosophila, treatment with ACE inhibitors extends the lifespan. In rodents, manipulating the RAS with genetic or pharmacological interventions can extend the lifespan. In humans, polymorphisms in the ACE gene are associated with extreme longevity. These results suggest the RAS plays a conserved role in controlling longevity. Here, we review studies of the RAS and aging, emphasizing the potential of C. elegans as a model for understanding the mechanism of lifespan control.

Proteolysis in Reproduction: Lessons From Gene-Modified Organism Studies

The physiological roles of proteolysis are not limited to degrading unnecessary proteins. Proteolysis plays pivotal roles in various biological processes through cleaving peptide bonds to activate and inactivate proteins including enzymes, transcription factors, and receptors. As a wide range of cellular processes is regulated by proteolysis, abnormalities or dysregulation of such proteolytic processes therefore often cause diseases. Recent genetic studies have clarified the inclusion of proteases and protease inhibitors in various reproductive processes such as development of gonads, generation and activation of gametes, and physical interaction between gametes in various species including yeast, animals, and plants. Such studies not only clarify proteolysis-related factors but the biological processes regulated by proteolysis for successful reproduction. Here the physiological roles of proteases and proteolysis in reproduction will be reviewed based on findings using gene-modified organisms.

ACE and ACE2: insights from Drosophila and implications for COVID-19

Angiotensin-converting enzyme (ACE) and its homologue ACE2 are key regulators of the renin-angiotensin system and thereby cardiovascular function through their zinc-metallopeptidase activity on vasoactive peptides. ACE2 also serves as the receptor for the cellular entry of various coronaviruses including the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is responsible for the coronavirus disease 2019 (COVID-19). The unprecedented scale of the COVID-19 pandemic has spurred the use of mammalian models to investigate the SARS-ACE2 relationship and knowledge gained from such research has accelerated development of vaccines and therapeutics. Recent studies have just started to underscore the utility of the fruit fly Drosophila melanogaster as a model system to study virus-host interactions and pathogenicity. Notably, the remarkable existence of catalytically functional ACE and ACE2 orthologues in Drosophila, discovered more than two decades ago, provides a unique opportunity for further developing this model organism to better understand COVID-19 in addition to identifying coronavirus preventative and therapeutic interventions targeting ACE2. Here, we review the studies that revealed crucial insights on the biochemistry and physiology of Ance and Acer, two out of the six Drosophila ACE family members with the greatest homology to human ACE and ACE2. We highlight shared in vivo functions outside of the renin-angiotensin system, which is not conserved in flies. Importantly, we identify knowledge gaps that can be filled by further research and outline ways that can raise Drosophila to a powerful model system to combat SARS-CoV-2 and its threatening vaccine-evading variants.

Cell Adhesion-Mediated Actomyosin Assembly Regulates the Activity of Cubitus Interruptus for Hematopoietic Progenitor Maintenance in Drosophila

The actomyosin network is involved in crucial cellular processes including morphogenesis, cell adhesion, apoptosis, proliferation, differentiation, and collective cell migration in Drosophila, Caenorhabditiselegans, and mammals. Here, we demonstrate that Drosophila larval blood stem-like progenitors require actomyosin activity for their maintenance. Genetic loss of the actomyosin network from progenitors caused a decline in their number. Likewise, the progenitor population increased upon sustained actomyosin activation via phosphorylation by Rho-associated kinase. We show that actomyosin positively regulates larval blood progenitors by controlling the maintenance factor Cubitus interruptus (Ci). Overexpression of the maintenance signal via a constitutively activated construct (ci.HA) failed to sustain Ci-155 in the absence of actomyosin components like Zipper (zip) and Squash (sqh), thus favoring protein kinase A (PKA)-independent regulation of Ci activity. Furthermore, we demonstrate that a change in cortical actomyosin assembly mediated by DE-cadherin modulates Ci activity, thereby determining progenitor status. Thus, loss of cell adhesion and downstream actomyosin activity results in desensitization of the progenitors to Hh signaling, leading to their differentiation. Our data reveal how cell adhesion and the actomyosin network cooperate to influence patterning, morphogenesis, and maintenance of the hematopoietic stem-like progenitor pool in the developing Drosophila hematopoietic organ.

Loss of angiotensin-converting enzyme-related (ACER) peptidase disrupts behavioural and metabolic responses to diet in Drosophila melanogaster

Drosophila Acer (Angiotensin-converting enzyme-related) encodes a member of the angiotensin-converting enzyme (ACE) family of metallopeptidases that in mammals play roles in the endocrine regulation of blood homeostasis. ACE is also expressed in adipose tissue, where it is thought to play a role in metabolic regulation. Drosophila ACER is expressed in the adult fat body of the head and abdomen and is secreted into the haemolymph. Acer null mutants have previously been found to have reduced night-time sleep and greater sleep fragmentation. ACER may thus be part of a signalling system linking metabolism with sleep. To further understand the role of ACER in response to diet, we measured sleep and other nutrient-responsive phenotypes in Acer null flies under different dietary conditions. We show that loss of Acer disrupts the normal response of sleep to changes in nutrition. Other nutrient-sensitive phenotypes, including survival and glycogen storage, were also altered in the Acer mutant but lipid storage was not. Although the physiological substrate of the ACER peptidase has not been identified, an alteration of the normal nutrient-dependent control of Drosophila insulin-like peptide 5 protein in the Acer mutant suggests insulin/IGF-like signalling as a candidate pathway modulated by ACER in the nutrient-dependent control of sleep, survival and metabolism.

The angiotensin converting enzyme (ACE) inhibitor, captopril disrupts the motility activation of sperm from the silkworm, Bombyx mori

Angiotensin I-converting enzyme (also known as peptidyl dicarboxypeptidase A, ACE, and EC 3.4.15.1), which is found in a wide range of organisms, cleaves C-terminal dipeptides from relatively short oligopeptides. Mammalian ACE plays an important role in the regulation of blood pressure. However, the precise physiological functions of insect ACE homologs have not been understood. As part of our effort to elucidate new physiological roles of insect ACE, we herein report a soluble ACE protein in male reproductive secretions from the silkmoth, Bombyx mori. Seminal vesicle sperm are quiescent in vitro, but vigorous motility is activated by treatment with either a glandula (g.) prostatica homogenate or trypsin in vitro. When seminal vesicle sperm were pre-incubated with captopril, a strong and specific inhibitor of mammalian ACE, and then stimulated to initiate motility by the addition of the g. prostatica homogenate or trypsin, the overall level of acquired motility was reduced in an inhibitor-concentration-dependent manner. In the course of this project, we detected ACE-related carboxypeptidase activity that was inhibited by captopril in both the vesicular (v.) seminalis of the noncopulative male reproductive tract and in the spermatophore that forms in the female bursa copulatrix at the time of mating, just as in an earlier report on the tomato moth, Lacanobia oleracea, which belongs to a different lepidopteran species (Ekbote et al., 2003a). Two distinct genes encoding ACE-like proteins were identified by analysis of B. mori cDNA, and were named BmAcer and BmAcer2, respectively [the former was previously reported by Quan et al. (2001) and the latter was first isolated in this paper]. RT-qPCR and Western blot analyses indicated that the BmAcer2 was predominantly produced in v. seminalis and transferred to the spermatophore during copulation, while the BmAcer was not detected in the adult male reproductive organs. A recombinant protein of BmAcer2 (devoid of a signal peptide) that was expressed in Escherichia coli cells exhibited captopril-sensitive carboxypeptidase activities. Our findings show that the BmAcre2 gene encodes a secreted ACE protein included in the Bombyx seminal plasma. In particular, the silkworm ACE protein in the seminal fluid might be involved in the signaling pathway that leads to the activation and regulation of sperm motility.

Angiotensin-converting enzyme Ance is cooperatively regulated by Mad and Pannier in Drosophila imaginal discs

Angiotensin-converting enzyme (ACE) is an evolutionarily conserved peptidyl dipeptidase. Mammalian ACE converts angiotensin I to the active vasoconstrictor angiotensin II, thus playing a critical role for homeostasis of the renin-angiotensin system. In Drosophila, the ACE homolog Ance is expressed in specific regions of developing organs, but its regulatory mechanism has not been identified. Here we provide evidence that Ance expression is regulated by a combination of Mad and Pannier (Pnr) in imaginal discs. We demonstrate that Ance expression in eye and wing discs depends on Dpp signaling. The Mad binding site of Ance regulatory region is essential for Ance expression. Ance expression in imaginal discs is also regulated by the GATA family transcription factor Pnr. Pnr directly regulates Ance expression by binding to a GATA site of Ance enhancer. In addition, Pnr and Mad physically and genetically interact. Ance null mutants are morphologically normal but show genetic interaction with dpp mutants. Furthermore, we show that human SMAD2 and GATA4 physically interact and ACE expression in HEK293 cells is regulated by SMAD2 and GATA4. Taken together, this study reveals a cooperative mechanism of Ance regulation by Mad and Pnr. Our data also suggest a conserved transcriptional regulation of human ACE.

Insights into the Hypertensive Effects of Tityus serrulatus Scorpion Venom: Purification of an Angiotensin-Converting Enzyme-Like Peptidase

The number of cases of envenomation by scorpions has grown significantly in Brazil since 2007, with the most severe cases being caused by the Tityus serrulatus scorpion. Although envenomed patients mostly suffer neurotoxic manifestations, other symptoms, such as hypertension, cannot be exclusively attributed to neurotoxins. Omics analyses have detected plentiful amounts of metalloproteases in T. serrulatus venom. However, the roles played by these enzymes in envenomation are still unclear. Endeavoring to investigate the functions of scorpion venom proteases, we describe here for the first time an Angiotensin I-Converting Enzyme-like peptidase (ACE-like) purified from T. serrulatus venom. The crude venom cleaved natural and fluorescent substrates and these activities were inhibited by captopril. Regarding the serum neutralization, the scorpion antivenom was more effective at blocking the ACE-like activity than arachnid antivenom, although neither completely inhibited the venom cleavage action, even at higher doses. ACE-like was purified from the venom after three chromatographic steps and its identity was confirmed by mass spectrometric and transcriptomic analyses. Bioinformatics analysis showed homology between the ACE-like transcript sequences from Tityus spp. and human testis ACE. These findings advance our understanding of T. serrulatus venom components and may improve treatment of envenomation victims, as ACE-like may contribute to envenomation symptoms, especially the resulting hypertension.

A quantitative peptidomics approach to unravel immunological functions of angiotensin converting enzyme in Locusta migratoria

Locusta migratoria angiotensin converting enzyme (LmACE) is encoded by multiple exons displaying variable number of genomic duplications. Treatments of lipopolysaccharide (LPS) as well as peptidoglycan but not β-1-3 glucan resulted in enhanced expression of angiotensin converting enzyme in hemocytes of Locusta migratoria. No such effect was observed in fat body cells. Differential peptidomics using locust plasma samples post infection with LPS in combination with both an LmACE transcript knockdown by RNAi and a functional knockdown using captopril allowed the identification of 5 circulating LPS induced peptides which only appear in the hemolymph of locust having full LmACE functionality. As these peptides originate from larger precursor proteins such as locust hemocyanin-like protein, having known antimicrobial properties, the obtained results suggest a possible direct or indirect role of LmACE in the release of these peptides from their precursors. Additionally, this experimental setup confirmed the role of LmACE in the clearance of multiple peptides from the hemolymph.

The venomous cocktail of the vampire snail Colubraria reticulata (Mollusca, Gastropoda)

Background

Hematophagy arose independently multiple times during metazoan evolution, with several lineages of vampire animals particularly diversified in invertebrates. However, the biochemistry of hematophagy has been studied in a few species of direct medical interest and is still underdeveloped in most invertebrates, as in general is the study of venom toxins. In cone snails, leeches, arthropods and snakes, the strong target specificity of venom toxins uniquely aligns them to industrial and academic pursuits (pharmacological applications, pest control etc.) and provides a biochemical tool for studying biological activities including cell signalling and immunological response. Neogastropod snails (cones, oyster drills etc.) are carnivorous and include active predators, scavengers, grazers on sessile invertebrates and hematophagous parasites; most of them use venoms to efficiently feed. It has been hypothesized that trophic innovations were the main drivers of rapid radiation of Neogastropoda in the late Cretaceous.

We present here the first molecular characterization of the alimentary secretion of a non-conoidean neogastropod, Colubraria reticulata. Colubrariids successfully feed on the blood of fishes, throughout the secretion into the host of a complex mixture of anaesthetics and anticoagulants. We used a NGS RNA-Seq approach, integrated with differential expression analyses and custom searches for putative secreted feeding-related proteins, to describe in detail the salivary and mid-oesophageal transcriptomes of this Mediterranean vampire snail, with functional and evolutionary insights on major families of bioactive molecules.

Results

A remarkably low level of overlap was observed between the gene expression in the two target tissues, which also contained a high percentage of putatively secreted proteins when compared to the whole body. At least 12 families of feeding-related proteins were identified, including: 1) anaesthetics, such as ShK Toxin-containing proteins and turripeptides (ion-channel blockers), Cysteine-rich secretory proteins (CRISPs), Adenosine Deaminase (ADA); 2) inhibitors of primary haemostasis, such as novel vWFA domain-containing proteins, the Ectonucleotide pyrophosphatase/phosphodiesterase family member 5 (ENPP5) and the wasp Antigen-5; 3) anticoagulants, such as TFPI-like multiple Kunitz-type protease inhibitors, Peptidases S1 (PS1), CAP/ShKT domain-containing proteins, Astacin metalloproteases and Astacin/ShKT domain-containing proteins; 4) additional proteins, such the Angiotensin-Converting Enzyme (ACE: vasopressive) and the cytolytic Porins.

Conclusions

Colubraria feeding physiology seems to involve inhibitors of both primary and secondary haemostasis, anaesthetics, a vasoconstrictive enzyme to reduce feeding time and tissue-degrading proteins such as Porins and Astacins. The complexity of Colubraria venomous cocktail and the divergence from the arsenal of the few neogastropods studied to date (mostly conoideans) suggest that biochemical diversification of neogastropods might be largely underestimated and worth of extensive investigation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1648-4) contains supplementary material, which is available to authorized users.

Angiotensin-converting enzymes modulate aphid-plant interactions

Angiotensin-converting enzymes (ACEs) are key components of the renin–angiotensin system in mammals. However, the function of ACE homologs in insect saliva is unclear. Aphids presumably deliver effector proteins via saliva into plant cells to maintain a compatible insect–plant interaction. In this study, we showed that ACE modulates aphid–plant interactions by affecting feeding behavior and survival of aphids on host plants. Three ACE genes were identified from the pea aphid Acyrthosiphon pisum genome. ACE1 and ACE2 were highly expressed in the salivary glands and are predicted to function as secretory proteins. The ACE2 transcript level decreased in aphids fed on artificial diet compared with aphids fed on Vicia faba. The knockdown of the expression of each ACE by RNAi failed to affect aphid survival. When ACE1 and ACE2 were simultaneously knocked down, aphid feeding was enhanced. Aphids required less time to find the phloem sap and showed longer passive ingestion. However, the simultaneous knockdown of ACE1 and ACE2 resulted in a higher mortality rate than the control group when aphids were fed on plants. These results indicated that ACE1 and ACE2 function together to modulate A. pisum feeding and survival on plants.

ACE for all - a molecular perspective

Angiotensin-I converting enzyme (ACE, EC 3.4.15.1) is a zinc dependent dipeptidyl carboxypeptidase with an essential role in mammalian blood pressure regulation as part of the renin-angiotensin aldosterone system (RAAS). As such, it has long been targeted in the treatment of hypertension through the use of ACE inhibitors. Although ACE has been studied since the 1950s, only recently have the full range of functions of this enzyme begun to truly be appreciated. ACE homologues have been found in a host of other organisms, and are now known to be conserved in insects. Insect ACE homologues typically share over 30 % amino acid sequence identity with human ACE. Given that insects lack a mammalian type circulatory system, they must have crucial roles in other physiological processes. The first ACE crystal structures were reported during the last decade and have enabled these enzymes to be studied from an entirely different perspective. Here we review many of these key developments and the implications that they have had on our understanding of the diverse functions of these enzymes. Specifically, we consider how structural information is being used in the design of a new generation of ACE inhibitors with increased specificity, and how the structures of ACE homologues are related to their functions. The Anopheles gambiae genome is predicted to code for ten ACE homologues, more than any genome studied so far. We have modelled the active sites of some of these as yet uncharacterised enzymes to try and infer more about their potential roles at the molecular level.

Heart- and muscle-derived signaling system dependent on MED13 and Wingless controls obesity in Drosophila

Obesity develops in response to an imbalance of energy homeostasis and whole-body metabolism. Muscle plays a central role in the control of energy homeostasis through consumption of energy and signaling to adipose tissue. We reported previously that MED13, a subunit of the Mediator complex, acts in the heart to control obesity in mice. To further explore the generality and mechanistic basis of this observation, we investigated the potential influence of MED13 expression in heart and muscle on the susceptibility of Drosophila to obesity. Here, we show that heart/muscle-specific knockdown of MED13 or MED12, another Mediator subunit, increases susceptibility to obesity in adult flies. To identify possible muscle-secreted obesity regulators, we performed an RNAi-based genetic screen of 150 genes that encode secreted proteins and found that Wingless inhibition also caused obesity. Consistent with these findings, muscle-specific inhibition of Armadillo, the downstream transcriptional effector of the Wingless pathway, also evoked an obese phenotype in flies. Epistasis experiments further demonstrated that Wingless functions downstream of MED13 within a muscle-regulatory pathway. Together, these findings reveal an intertissue signaling system in which Wingless acts as an effector of MED13 in heart and muscle and suggest that Wingless-mediated cross-talk between striated muscle and adipose tissue controls obesity in Drosophila. This signaling system appears to represent an ancestral mechanism for the control of systemic energy homeostasis.

Comparative gene expression analysis of Dtg, a novel target gene of Dpp signaling pathway in the early Drosophila melanogaster embryo

In the early Drosophila melanogaster embryo, Dpp, a secreted molecule that belongs to the TGF-β superfamily of growth factors, activates a set of downstream genes to subdivide the dorsal region into amnioserosa and dorsal epidermis. Here, we examined the expression pattern and transcriptional regulation of Dtg, a new target gene of Dpp signaling pathway that is required for proper amnioserosa differentiation. We showed that the expression of Dtg was controlled by Dpp and characterized a 524-bp enhancer that mediated expression in the dorsal midline, as well as, in the differentiated amnioserosa in transgenic reporter embryos. This enhancer contained a highly conserved region of 48-bp in which bioinformatic predictions and in vitro assays identified three Mad binding motifs. Mutational analysis revealed that these three motifs were necessary for proper expression of a reporter gene in transgenic embryos, suggesting that short and highly conserved genomic sequences may be indicative of functional regulatory regions in D. melanogaster genes. Dtg orthologs were not detected in basal lineages of Dipterans, which unlike D. melanogaster develop two extra-embryonic membranes, amnion and serosa, nevertheless Dtg orthologs were identified in the transcriptome of Musca domestica, in which dorsal ectoderm patterning leads to the formation of a single extra-embryonic membrane. These results suggest that Dtg was recruited as a new component of the network that controls dorsal ectoderm patterning in the lineage leading to higher Cyclorrhaphan flies, such as D. melanogaster and M. domestica.

A modern understanding of the traditional and nontraditional biological functions of angiotensin-converting enzyme

Angiotensin-converting enzyme (ACE) is a zinc-dependent peptidase responsible for converting angiotensin I into the vasoconstrictor angiotensin II. However, ACE is a relatively nonspecific peptidase that is capable of cleaving a wide range of substrates. Because of this, ACE and its peptide substrates and products affect many physiologic processes, including blood pressure control, hematopoiesis, reproduction, renal development, renal function, and the immune response. The defining feature of ACE is that it is composed of two homologous and independently catalytic domains, the result of an ancient gene duplication, and ACE-like genes are widely distributed in nature. The two ACE catalytic domains contribute to the wide substrate diversity of ACE and, by extension, the physiologic impact of the enzyme. Several studies suggest that the two catalytic domains have different biologic functions. Recently, the X-ray crystal structure of ACE has elucidated some of the structural differences between the two ACE domains. This is important now that ACE domain-specific inhibitors have been synthesized and characterized. Once widely available, these reagents will undoubtedly be powerful tools for probing the physiologic actions of each ACE domain. In turn, this knowledge should allow clinicians to envision new therapies for diseases not currently treated with ACE inhibitors.

A crucial role in fertility for the oyster angiotensin-converting enzyme orthologue CgACE

Angiotensin-converting enzyme (ACE) is a highly conserved metallopeptidase. In mammals, the somatic isoform governs blood pressure whereas the germinal isoform (tACE) is required for fertility. In Ecdysozoans, ACE-like enzymes are implicated in reproduction. Despite ACE orthologues being present from bacteria to humans, their function(s) remain(s) unknown in distant organisms such as Lophotrochozoans. In silico analysis of an oyster (Crassostrea gigas) EST library suggested the presence of an ACE orthologue in molluscs. Primer walking and 5'-RACE revealed that the 1.9 kb cDNA encodes CgACE, a 632 amino acid protein displaying a conserved single active site and a putative C-terminal transmembrane anchor, thus resembling human tACE, as supported by molecular modelling. FRET activity assays and Maldi-TOF spectrometry indicated that CgACE is a functional dipeptidyl-carboxypeptidase which is active on Angiotensin I and sensitive to ACE inhibitors and chloride ion concentration. Immunocytochemistry revealed that, as its human counterpart, recombinant CgACE is synthesised as a transmembrane enzyme. RT-qPCR, in-situ hybridization and immunohistochemistry shed light on a tissue, and development stage, specific expression pattern for CgACE, which is increased in the gonad during spermatogenesis. The use of ACE inhibitors in vivo indicates that the dipeptidase activity of CgACE is crucial for the oyster fertilization. Our study demonstrates that a transmembrane active ACE is present in the oyster Crassostrea gigas, and for the first time ascribes a functional role for ACE in Lophotrochozoans. Its biological function in reproduction is conserved from molluscs to humans, a finding of particular evolutionary interest especially since oysters represent the most important aquaculture resource worldwide.

Angiotensin-converting enzyme in Spodoptera littoralis: molecular characterization, expression and activity profile during development

The characterization of the full-length angiotensin-converting enzyme (ACE) cDNA sequence of the lepidopteran Spodoptera littoralis is reported in this study. The predicted open reading frame encodes a 647 amino acids long protein (SlACE) and shows 63.6% identity with the Bombyx mori ACE sequence. A 3D-model, consisting of 26 alpha-helices and three beta-sheets, was predicted for the sequence. SlACE expression was studied in the embryonic, larval and pupal stages of S. littoralis and in different tissues of the last larval stage by reverse-transcribed PCR. This revealed that the gene is expressed throughout the life cycle and especially in brain, gut and fat body tissue of the last stage. These results are in agreement with a role of ACE in the metabolism of neuropeptides and gut hormones. In addition, ACE activity has been studied in more detail during development, making use of a fluorescent assay. High ACE peptidase activity coincides with every transition state, from embryo to larva, from larva to larva and from larva to pupa. A peak value in activity occurs during the early pupal stage. These results indicate the importance of SlACE during metamorphosis and reveal the high correlation of ACE activity with the insect's development, which is regulated by growth and developmental hormones.

Genome-wide analysis of the interaction between the endosymbiotic bacterium Wolbachia and its Drosophila host

Background

Intracellular Wolbachia bacteria are obligate, maternally-inherited, endosymbionts found frequently in insects and other invertebrates. The success of Wolbachia can be attributed in part to an ability to alter host reproduction via mechanisms including cytoplasmic incompatibility (CI), parthenogenesis, feminization and male killing. Despite substantial scientific effort, the molecular mechanisms underlying the Wolbachia/host interaction are unknown.

Results

Here, an in vitro Wolbachia infection was generated in the Drosophila S2 cell line, and transcription profiles of infected and uninfected cells were compared by microarray. Differentially-expressed patterns related to reproduction, immune response and heat stress response are observed, including multiple genes that have been previously reported to be involved in the Wolbachia/host interaction. Subsequent in vivo characterization of differentially-expressed products in gonads demonstrates that Angiotensin Converting Enzyme (Ance) varies between Wolbachia infected and uninfected flies and that the variation occurs in a sex-specific manner. Consistent with expectations for the conserved CI mechanism, the observed Ance expression pattern is repeatable in different Drosophila species and with different Wolbachia types. To examine Ance involvement in the CI phenotype, compatible and incompatible crosses of Ance mutant flies were conducted. Significant differences are observed in the egg hatch rate resulting from incompatible crosses, providing support for additional experiments examining for an interaction of Ance with the CI mechanism.

Conclusion

Wolbachia infection is shown to affect the expression of multiple host genes, including Ance. Evidence for potential Ance involvement in the CI mechanism is described, including the prior report of Ance in spermatid differentiation, Wolbachia-induced sex-specific effects on Ance expression and an Ance mutation effect on CI levels. The results support the use of Wolbachia infected cell cultures as an appropriate model for predicting in vivo host/Wolbachia interactions.

Male accessory glands of Drosophila melanogaster make a secreted angiotensin I-converting enzyme (ANCE), suggesting a role for the peptide-processing enzyme in seminal fluid

Angiotensin I-converting enzyme (ACE) expressed on the surface of endothelial cells is responsible for the last step in the synthesis of circulating angiotensin II and the inactivation of bradykinin. Mammalian ACE is also expressed in the prostate with other components of the renin-angiotensin system, and in developing spermatids, where the peptidase activity is known to be critical for normal sperm function. The importance of an ACE gene to male fertility has also been demonstrated in Drosophila melanogaster, where Ance is expressed in spermatids, and hypomorphic alleles of Ance cause a defect in spermiogenesis. Here we show that ANCE, which shares many enzymatic properties with mammalian ACE, is also a product of the male accessory gland of D. melanogaster. It is expressed in the secondary cells and is associated with the electron dense granule within the large vesicles of these cells. ACE proteolytic activity is lost from the accessory glands during mating, consistent with transfer to the mated female in the seminal fluid. The accessory gland ACE-like activity might have an evolutionarily conserved function processing biologically active peptides with a role in male fertility.

Characterization of the first angiotensin-converting like enzyme in bacteria: Ancestor ACE is already active

Angiotensin-converting enzyme (ACE) is a metallopeptidase that converts angiotensin I into angiotensin II. ACE is crucial in the control of cardiovascular and renal homeostasis and fertility in mammals. In vertebrates, both transmembrane and soluble ACE, containing one or two active sites, have been characterized. So far, only soluble, single domain ACEs from invertebrates have been cloned, and these have been implicated in reproduction in insects. Furthermore, an ACE-related carboxypeptidase was recently characterized in Leishmania, a unicellular eukaryote, suggesting the existence of ACE in more distant organisms.

Interestingly, in silico databank analysis revealed that bacterial DNA sequences could encode putative ACE-like proteins, strikingly similar to vertebrates' enzymes. To gain more insight into the bacterial enzymes, we cloned the putative ACE from the phytopathogenic bacterium, Xanthomonas axonopodis pv. citri, named XcACE. The 2 kb open reading frame encodes a 672-amino-acid soluble protein containing a single active site. In vitro expression and biochemical characterization revealed that XcACE is a functional 72 kDa dipeptidyl-carboxypeptidase. As in mammals, this metalloprotease hydrolyses angiotensin I into angiotensin II. XcACE is sensitive to ACE inhibitors and chloride ions concentration. Variations in the active site residues, highlighted by structural modelling, can account for the different substrate selectivity and inhibition profile compared to human ACE. XcACE characterization demonstrates that ACE is an ancestral enzyme, provoking questions about its appearance and structure/activity specialisation during the course of evolution.

Angiotensin-converting enzyme as a target for the development of novel insect growth regulators

Insect angiotensin converting enzyme (ACE) is a zinc metallopeptidase capable of inactivating a variety of small to medium size peptide hormones by cleavage of C-terminal dipeptides and dipeptideamides. High levels of ACE activity are found in the hemolymph and in reproductive tissues of insects, where the enzyme is considered to have an important role in the metabolism of bioactive peptides. Therefore, inhibiting ACE activity is expected to interfere with the peptidergic endocrine system and to have detrimental effects on growth, development and reproduction. We will review the studies showing that ACE inhibitors do indeed disrupt growth and reproduction in various insect species. We will also present some new genetic and pharmacological data that strengthens our conclusion that ACE should be considered as a potential target for the development of new insect growth regulators.

Presence of angiotensin converting enzyme isoforms in larval lepidoptera (Spodoptera littoralis)

In this research the presence of angiotensin converting enzyme (ACE) in larvae of the lepidopteran Spodoptera littoralis was evaluated. Making use of the substrate Abz-FRK-(Dnp)P-OH and the specific inhibitor captopril at 10 microM, ACE activity was determined in a fluorescence assay for intact larvae, hemolymph, head, midgut and dorsal tissue. In dorsal tissue and hemolymph, ACE activity was highest. These data are consistent with a possible role for ACE in contractions of the dorsal vessel and metabolism of circulating peptide hormones in the hemolymph. After the presence of ACE was confirmed, a sequential procedure of anion exchange and size exclusion chromatography was applied to purify ACE from whole wandering larvae (last stage). With this procedure, three different ACE pools were collected that cleaved the fluorogenic substrate Abz-FRK-(Dnp)P-OH. Activity could be inhibited by a final concentration of 2.5 microM captopril. In addition, two out of three samples eluted at different salt concentration and thus ACE 1, 2 and 3 represent at least two different ACE isoforms. These data reveal that ACE is present in S. littoralis and that at least two out of three isolated ACE forms are truly isoforms.

Threshold response of C15 to the Dpp gradient in Drosophila is established by the cumulative effect of Smad and Zen activators and negative cues

Morphogen gradients determine a range of cell fates by specifying multiple transcriptional threshold responses. In the dorsal ectoderm of the Drosophila embryo, a BMP gradient is translated into an activated Smad transcription factor gradient, which elicits at least three threshold responses - high, intermediate and low. However, the mechanism underlying differential response to Dpp is poorly understood, due in part to the insufficient number of well-studied target genes. We analyzed the regulation of the C15 gene, which can be activated in cells containing intermediate levels of Dpp. We show that C15 expression requires both dpp and zen, thus forming a genetic feed-forward loop. The C15 regulatory element contains clusters of Smad- and Zen-binding sites in close proximity. Mutational analysis shows that the number of intact Smad- and Zen-binding sites is essential for the C15 transcriptional response, and that the spatial limits of C15 expression are established through a repression mechanism in the dorsolateral cells of the embryo. Thus, the combinatorial action of Smad and Zen activators bound to a number of adjacent sites, and competing negative cues allows for proper gene response to lower than peak levels of the Dpp morphogen.

Regulation of the retinal determination gene dachshund in the embryonic head and developing eye of Drosophila

The retinal determination gene dachshund is distantly related to the family of Ski/Sno proto-oncogenes and influences the development of a wide range of tissues including the embryonic head, optic lobes, brain, central nervous system as well as the post-embryonic leg, wing, genital and eye-antennal discs. We were interested in the regulatory mechanisms that control the dynamic expression pattern of dachshund and in this report we set out to ascertain how the transcription of dachshund is modulated in the embryonic head and developing eye-antennal imaginal disc. We demonstrate that the TGFbeta signaling cascade, the transcription factor zerknullt and several other patterning genes prevent dachshund from being expressed inappropriately within the embryonic head. Additionally, we show that several members of the eye specification cascade influence the transcription of dachshund during normal and ectopic eye development. Our results suggest that dachshund is regulated by a complex combinatorial code of transcription factors and signaling pathways. Unraveling this code may lead to an understanding of how dachshund regulates the development of many diverse tissue types including the eye.

Structural diversity of angiotensin-converting enzyme

The crystal structure of a Drosophila angiotensin-converting enzyme (ANCE) has recently been solved, revealing features important for the binding of ACE inhibitors and allowing molecular comparisons with the structure of human testicular angiotensin-converting enzyme (tACE). ACER is a second Drosophila ACE that displays both common and distinctive properties. Here we report further functional differences between ANCE and ACER and have constructed a homology model of ACER to help explain these. The model predicts a lack of the Cl(-)-binding sites, and therefore the strong activation of ACER activity towards enkephalinamide peptides by NaCl suggests alternative sites for Cl(-) binding. There is a marked difference in the electrostatic charge of the substrate channel between ANCE and ACER, which may explain why the electropositive peptide, MKRSRGPSPRR, is cleaved efficiently by ANCE with a low K(m), but does not bind to ACER. Bradykinin (BK) peptides are excellent ANCE substrates. Models of BK docked in the substrate channel suggest that the peptide adopts an N-terminal beta-turn, permitting a tight fit of the peptide in the substrate channel. This, together with ionic interactions between the guanidino group of Arg9 of BK and the side chains of Asp360 and Glu150 in the S(2)' pocket, are possible reasons for the high-affinity binding of BK. The replacement of Asp360 with a histidine in ACER would explain the higher K(m) recorded for the hydrolysis of BK peptides by this enzyme. Other differences in the S(2)' site of ANCE and ACER also explain the selectivity of RXPA380, a selective inhibitor of human C-domain ACE, which also preferentially inhibits ACER. These structural and enzymatic studies provide insight into the molecular basis for the distinctive enzymatic features of ANCE and ACER.

Oncopeltus fasciatus zen is essential for serosal tissue function in katatrepsis

Unlike most Hox cluster genes, with their canonical role in anterior-posterior patterning of the embryo, the Hox3 orthologue of insects has diverged. Here, we investigate the zen orthologue in Oncopeltus fasciatus (Hemiptera:Heteroptera). As in other insects, the Of-zen gene is expressed extraembryonically, and RNA interference (RNAi) experiments demonstrate that it is functionally required in this domain for the proper occurrence of katatrepsis, the phase of embryonic movements by which the embryo emerges from the yolk and adjusts its orientation within the egg. After RNAi knockdown of Of-zen, katatrepsis does not occur, causing embryos to complete development inside out. However, not all aspects of expression and function are conserved compared to grasshopper, beetle, and fly orthologues. Of-zen is not expressed in the extraembryonic tissue until relatively late, suggesting it is not involved in tissue specification. Within the extraembryonic domain, Of-zen is expressed in the outer serosal membrane, but unlike orthologues, it is not detectable in the inner extraembryonic membrane, the amnion. Thus, the role of zen in the interaction of serosa, amnion, and embryo may differ between species. Of-zen is also expressed in the blastoderm, although this early expression shows no apparent correlation with defects seen by RNAi knockdown.

An endoderm-specific GATA factor gene, dGATAe, is required for the terminal differentiation of the Drosophila endoderm

GATA factors play an essential role in endodermal specification in both protostomes and deuterostomes. In Drosophila, the GATA factor gene serpent (srp) is critical for differentiation of the endoderm. However, the expression of srp disappears around stage 11, which is much earlier than overt differentiation occurs in the midgut, an entirely endodermal organ. We have identified another endoderm-specific Drosophila GATA factor gene, dGATAe. Expression of dGATAe is first detected at stage 8 in the endoderm, and its expression continues in the endodermal midgut throughout the life cycle. srp is required for expression of dGATAe, and misexpression of srp resulted in ectopic dGATAe expression. Embryos that either lacked dGATAe or were injected with double-stranded RNA (dsRNA) corresponding to dGATAe failed to express marker genes that are characteristic of differentiated midgut. Conversely, overexpression of dGATAe induced ectopic expression of endodermal markers even in the absence of srp activity. Transfection of the dGATAe cDNA also induced endodermal markers in Drosophila S2 cells. These studies provide an outline of the genetic pathway that establishes the endoderm in Drosophila. This pathway is triggered by sequential signaling through the maternal torso gene, a terminal gap gene, huckebein (hkb), and finally, two GATA factor genes, srp and dGATAe.

Peak levels of BMP in theDrosophilaembryo control target genes by a feed-forward mechanism

Gradients of morphogens determine cell fates by specifying discrete thresholds of gene activities. In the Drosophila embryo, a BMP gradient subdivides the dorsal ectoderm into amnioserosa and dorsal epidermis,and also inhibits neuroectoderm formation. A number of genes are differentially expressed in response to the gradient, but how their borders of expression are established is not well understood. We present evidence that the BMP gradient, via the Smads, provides a two-fold input in regulating the amnioserosa-specific target genes such as Race. Peak levels of Smads in the presumptive amnioserosa set the expression domain of zen, and then Smads act in combination with Zen to directly activate Race. This situation resembles a feed-forward mechanism of transcriptional regulation. In addition, we demonstrate that ectopically expressed Zen can activate targets like Race in the presence of low level Smads,indicating that the role of the highest activity of the BMP gradient is to activate zen.

Characterization of the first non-insect invertebrate functional angiotensin-converting enzyme (ACE): leech TtACE resembles the N-domain of mammalian ACE

Angiotensin-converting enzyme (ACE) is a zinc metallopeptidase that plays a major role in blood homoeostasis and reproduction in mammals. In vertebrates, both transmembrane and soluble ACE, containing one or two homologous active sites, have been characterized. So far, several ACEs from invertebrates have been cloned, but only in insects. They are soluble and display a single active site. Using biochemical procedures, an ACE-like activity was detected in our model, the leech, Theromyzon tessulatum. Annelida is the most distant phylum in which an ACE activity has been observed. To gain more insight into the leech enzyme, we have developed a PCR approach to characterize its mRNA. The approx. 2 kb cDNA has been predicted to encode a 616-amino-acid soluble enzyme containing a single active site, named TtACE (T. tessulatum ACE). Surprisingly, its primary sequence shows greater similarity to vertebrates than to invertebrates. Stable in vitro expression of TtACE in transfected Chinese-hamster ovary cells revealed that the leech enzyme is a functional metalloprotease. As in mammals, this 79 kDa glycosylated enzyme functions as a dipeptidyl carboxypeptidase capable of hydrolysing angiotensin I to angiotensin II. However, a weak chloride inhibitory effect and acetylated N-acetyl-SDKP (Ac SDAcKP) hydrolysis reveal that TtACE activity resembles that of the N-domain of mammalian ACE. In situ hybridization shows that its cellular distribution is restricted to epithelial midgut cells. Although the precise roles and endogenous substrates of TtACE remain to be identified, characterization of this ancestral peptidase will help to clarify its physiological roles in non-insect invertebrate species.

Identification of genes expressed during Drosophila melanogaster gastrulation by using subtractive hybridization

A subtractive hybridization approach was used to identify genes that are expressed at the beginning of gastrulation. We used tester DNA complimentary to RNA (cDNA) prepared from stages 6-7 embryos (gastrula) and excess driver cDNA from stages 2-4 embryos (syncytial blastoderm) to generate a gastrula-subtracted cDNA library. A reverse Northern blot procedure used to analyze 105 subtracted clones showed that 65% had a level of expression at least 2.5-fold higher in stages 6-7 versus stages 2-4 embryos. We determined the nucleotide sequence of these clones and identified 49 individual sequences, including 33 previously uncharacterized genes. We verified the level of expression of 24 genes during Drosophila melanogaster embryogenesis using a semiquantitative polymerase chain reaction (PCR) approach. As expected, all of the selected clones showed their highest level of expression after stages 2-4 of embryogenesis, including several that displayed peaks of expression during gastrulation. Three genes that were expressed at their highest levels in stages 6-7 were further analyzed by 5'-rapid amplification of cDNA ends (RACE) analysis, Northern blot assays and in situ hybridization. Our results indicate that these genes exhibited temporal and spatially restricted patterns of expression in developing embryos, and moreover, their transcripts were detected in cells that undergo morphological changes during the gastrulation stage. Characterizing the role of these genes will be important to increase our understanding of the molecular mechanisms that regulate cellular activities during D. melanogaster gastrulation.

The angiotensin converting enzyme inhibitor captopril reduces oviposition and ecdysteroid levels in Lepidoptera

The role of angiotensin converting enzyme (ACE, peptidyl dipeptidase A) in metamorphic- and reproductive-related events in the Egyptian cotton leafworm, Spodoptera littoralis (Lepidoptera, Noctuidae) was studied by using the selective ACE inhibitor captopril. Although oral administration of captopril had no effect on larval growth, topical administration to new pupae resulted in a large decrease of successful adult formation. Oviposition and overall appearance of adults emerging from treated larvae did not differ significantly from those emerging from non-treated larvae. In contrast, topical or oral administration of captopril to newly emerged adults caused a reduction in oviposition. By evaluating the effect of captopril on ecdysteroid titers and trypsin activity, we revealed an additional physiological role for ACE. Captopril exerted an inhibitory effect on ecdysteroid levels in female but not in male adults. Larvae fed a diet containing captopril exhibited increased trypsin activity. A similar captopril-induced increase in trypsin activity was observed in female adults. In male adults, however, captopril elicited reduced levels of trypsin activity. Our results suggest that captopril downregulates oviposition by two independent pathways, one through ecdysteroid biosynthesis regulation, and the other through regulation of trypsin activity. Apparently, fecundity is influenced by a complex interaction of ACE, trypsin activity, and ecdysteroid levels.

Zinc-metalloproteases in insects: ACE and ECE

Research on the angiotensin-converting enzyme (ACE) in insects has substantially advanced during the recent decade. The cloning of this enzyme in many insect species, the determination of the 3D-structure and several molecular and physiological studies have contributed to the characterization of insect ACE as we know it today: a functional enzyme with a putative role in reproduction, development and defense. The discovery of the endothelin-converting enzyme in insects occurred more recently and cloning of the corresponding cDNA has been carried out in only one insect species so far. However, activity studies and analysis of insect genomes indicate that this enzyme is also widely distributed among insect species. Making hypotheses about its putative function would be preliminary, but its wide tissue distribution suggests a major and diverse biological role.

Implications for the functions of the four known midgut differentiation factors: An immunohistologic study of Heliothis virescens midgut

Antibodies to the peptides that induce differentiation of midgut larval stem cells, the midgut differentiating factors MDF-2, MDF-3, and MDF-4, bind to columnar cells in midgut cultures and in intact midgut of Heliothis virescens, in manners similar to the binding of anti- MDF-1 to those tissues. Antibodies to MDF-2 and MDF-3 also stained droplets in the midgut lumen, suggesting that columnar cells may also release MDF-2- and MDF-3-like cytokines to the lumen. Antibody to MDF-4 exhibited similar staining patterns but also recognized stem and differentiating cells, the presumed targets of peptides that regulate stem cell differentiation. Antibody to MDF-4 also bound to one type of endocrine cell in midgut cultures and in sections of midgut, as well as to the endocrine secretion released both to the midgut lumen and the hemolymph. Antibodies to the MDFs 1, 2, and 3, incubated with cultures of midgut cells, did not appear to prevent differentiation of the stem cells in the cultures but affected viability of mature cells, reflected in increased apoptosis and doubling of the number of differentiating cells compared to controls. Only antibody to MDF-4 induced temporary necrosis and inhibition of population recovery, indicating that MDF4 may be the true differentiation factor. The other MDFs may have additional functions beyond regulation of midgut stem cell differentiation in vivo.

Structure, evolutionary conservation, and functions of angiotensin- and endothelin-converting enzymes

Angiotensin-converting enzyme, a member of the M2 metalloprotease family, and endothelin-converting enzyme, a member of the M13 family, are key components in the regulation of blood pressure and electrolyte balance in mammals. From this point of view, they serve as important drug targets. Recently, the involvement of these enzymes in the development of Alzheimer's disease was discovered. The existence of homologs of these enzymes in invertebrates indicates that these enzyme systems are highly conserved during evolution. Most invertebrates lack a closed circulatory system, which excludes the need for blood pressure regulators. Therefore, these organisms represent excellent targets for gaining new insights and revealing additional physiological roles of these important enzymes. This chapter reviews the structural and functional aspects of ACE and ECE and will particularly focus on these enzyme homologues in invertebrates.

Antibacterial and proteolytic activity in venom from the endoparasitic wasp Pimpla hypochondriaca (Hymenoptera: Ichneumonidae)

Venom from the endoparasitic wasp, Pimpla hypochondriaca, is composed of a mixture of high and low molecular weight proteins, possesses phenoloxidase activity, has immunosuppressive properties, and induces paralysis in several insect species. In the present study we demonstrate that P. hypochondriaca venom also contains antibacterial and proteolytic activity. Antibacterial activity was detected against the Gram-negative bacteria Escherichia coli and Xanthamonas campestris but not against Pseudomonas syringae nor against two Gram-positive bacteria, Bacillus cereus and Bacillus subtilis. Endopeptidase and aminopeptidase activity in venom was detected using the synthetic fluorogenic substrates N-t-BOC-Phe-Ser-Arg-AMC, Arg-AMC and Leu-Arg. The aminopeptidase activity towards Arg-AMC was sensitive to amastatin (70% inhibition), an aminopeptidase inhibitor. Angiotensin-converting enzyme (ACE)-like enzyme activity was detected, by reverse-phase HPLC using the synthetic tripeptide Hip-His-Leu as a substrate. This activity was sensitive to captopril, an ACE inhibitor (IC(50) 3.8 x 10(-8) M). Using an antiserum raised against recombinant Drosophila melanogaster ACE-like enzyme, (rAnce), Western blot analysis revealed an immunoreactive protein, with a molecular weight estimate of 74 kDa, in P. hypochondriaca venom. The possibility that the endopeptidase, aminopeptidase and ACE are involved in the processing of peptide precursors in the venom sac is discussed.

Molecular evidence for the expression of angiotensin converting enzyme in hemocytes of Locusta migratoria: stimulation by bacterial lipopolysaccharide challenge

The presence of angiotensin converting enzyme (ACE) in insects has been reported many times, but numerous questions about the functional role of this enzyme in insects remain. Here we show by RT-PCR experiments that ACE has a wide tissue distribution in Locusta migratoria, suggesting diverse roles for this enzyme in the locust. Immune challenge through injection of bacterial lipopolysaccharides resulted in a tenfold increase of ACE gene transcripts in the hemocytes and is suggestive for a role of ACE in the cellular defense of the locust. However, phenotypic knockout experiments with the ACE inhibitor captopril showed that ACE is not essential for the efficient clearance of injected E. coli bacteria.

The T-box-encoding Dorsocross genes function in amnioserosa development and the patterning of the dorsolateral germ band downstream of Dpp

Dpp signals are responsible for establishing a variety of cell identities in dorsal and lateral areas of the early Drosophila embryo, including the extra-embryonic amnioserosa as well as different ectodermal and mesodermal cell types. Although we have a reasonably clear picture of how Dpp signaling activity is modulated spatially and temporally during these processes, a better understanding of how these signals are executed requires the identification and characterization of a collection of downstream genes that uniquely respond to these signals. In the present study, we describe three novel genes, Dorsocross1, Dorsocross2 and Dorsocross3, which are expressed downstream of Dpp in the presumptive and definitive amnioserosa, dorsal ectoderm and dorsal mesoderm. We show that these genes are good candidates for being direct targets of the Dpp signaling cascade. Dorsocross expression in the dorsal ectoderm and mesoderm is metameric and requires a combination of Dpp and Wingless signals. In addition, a transverse stripe of expression in dorsoanterior areas of early embryos is independent of Dpp. The Dorsocross genes encode closely related proteins of the T-box domain family of transcription factors. All three genes are arranged in a gene cluster, are expressed in identical patterns in embryos, and appear to be genetically redundant. By generating mutants with a loss of all three Dorsocross genes, we demonstrate that Dorsocross gene activity is crucial for the completion of differentiation, cell proliferation arrest, and survival of amnioserosa cells. In addition, we show that the Dorsocross genes are required for normal patterning of the dorsolateral ectoderm and, in particular, the repression of wingless and the ladybird homeobox genes within this area of the germ band. These findings extend our knowledge of the regulatory pathways during amnioserosa development and the patterning of the dorsolateral embryonic germ band in response to Dpp signals.

ACE inhibitors reduce fecundity in the mosquito, Anopheles stephensi

Angiotensin-converting enzyme (ACE) is a dipeptidyl carboxypeptidase, which cleaves dipeptides and, in some instances, dipeptide or tripeptide amides from the C-terminus of regulatory peptides (e.g. angiotensin I, bradykinin and substance P). The expression of ACE is highly regulated in insects, where it is thought to have a role in the metabolism of peptide hormones involved in regulating reproduction. After a blood meal, ACE activity in the female mosquito Anopheles stephensi, increases four-fold with much of the enzyme finally accumulating in the ovary. In the present study, we have studied the effect on reproduction of adding two selective inhibitors of ACE, captopril and lisinopril, to the blood meal. Both ACE inhibitors reduced the size of the batch of eggs laid by females in a dose-dependent manner, with no observable effects on the behaviour of the adult insect. The almost total failure to lay eggs after feeding on either 1 mM captopril or 1 mM lisinopril, did not result from interference with the development of the primary follicle, but was due to the inhibition of egg-laying. Since very similar effects on the size of the egg-batch were observed with two selective ACE inhibitors, belonging to different chemical classes, we suggest that these effects are mediated by the selective inhibition of the induced mosquito ACE, a peptidase probably involved in the activation/inactivation of a peptide regulating egg-laying activity in A. stephensi.

Crystal structure of Drosophila angiotensin I-converting enzyme bound to captopril and lisinopril

Angiotensin I-converting enzymes (ACEs) are zinc metallopeptidases that cleave carboxy-terminal dipeptides from short peptide hormones. We have determined the crystal structures of AnCE, a Drosophila homolog of ACE, with and without bound inhibitors to 2.4 A resolution. AnCE contains a large internal channel encompassing the entire protein molecule. This substrate-binding channel is composed of two chambers, reminiscent of a peanut shell. The inhibitor and zinc-binding sites are located in the narrow bottleneck connecting the two chambers. The substrate and inhibitor specificity of AnCE appears to be determined by extensive hydrogen-bonding networks and ionic interactions in the active site channel. The catalytically important zinc ion is coordinated by the conserved Glu395 and histidine residues from a HExxH motif.

The drosophila angiotensin-converting enzyme homologue Ance is required for spermiogenesis

The Angiotensin-converting enzyme (Ance) gene of Drosophila melanogaster is a homologue of mammalian angiotensin-converting enzyme (ACE), a peptidyl dipeptidase implicated in regulation of blood pressure and male fertility. In Drosophila, Ance protein is present in vesicular structures within spermatocytes and immature spermatids. It is also present within the lumen of the testis and the waste bag, and is associated with the surface of elongated spermatid bundles. Ance mRNA is found mainly in large primary spermatocytes and is not detectable in cyst cells. Testes lacking germ cells have reduced levels of ACE activity, and no Ance protein is detectable by immunocytochemistry, indicating that the germ cells are the major site of Ance synthesis. Ance mutant testes lack individualised sperm and have very few actin-based individualisation complexes. Spermatid nuclei undergo scattering along the cyst and have abnormal morphology, similar to other individualisation mutants. Mutant spermatids also have abnormal ultrastructure with grossly defective mitochondrial derivatives. The failure of Ance mutant testes to form individualisation complexes may be due to a failure in correct spermatid differentiation. Taken together, the expression pattern and mutant phenotype suggest that Ance is required for spermatid differentiation, probably through the processing of a regulatory peptide synthesised within the developing cyst.

Whole-genome analysis of dorsal-ventral patterning in the Drosophila embryo

The maternal Dorsal regulatory gradient initiates the differentiation of several tissues in the early Drosophila embryo. Whole-genome microarray assays identified as many as 40 new Dorsal target genes, which encode a broad spectrum of cell signaling proteins and transcription factors. Evidence is presented that a tissue-specific form of the NF-Y transcription complex is essential for the activation of gene expression in the mesoderm. Tissue-specific enhancers were identified for new Dorsal target genes, and bioinformatics methods identified conserved cis-regulatory elements for coordinately regulated genes that respond to similar thresholds of the Dorsal gradient. The new Dorsal target genes and enhancers represent one of the most extensive gene networks known for any developmental process.