A novel family of RGD-containing disintegrins (Tablysin-15) from the salivary gland of the horsefly Tabanus yao targets αIIbβ3 or αVβ3 and inhibits platelet aggregation and angiogenesis

FS145, the first flea-derived disintegrin, inhibits angiogenesis through specifically binding integrin αvβ3

FS145, a protein containing a WGD motif, was previously described from the salivary transcriptome of the flea Xenopsylla cheopis. Nevertheless, its biological function and complete structure are still uncertain. Herein, FS145 was confirmed to adopt a common αββ structure with the WGD motif exposed on its surface and located right at the top of a loop composed of residues 72-81. Furthermore, FS145 dose-dependently inhibited the proliferation, adhesion, migration, and tube formation of HUVECs by not only binding to integrin αvβ3 but also by subsequently inactivating the FAK/Src/MAPK pathway along with the reduction of the expression of MMP-2, MMP-9, VEGFA, bFGF, Ang2, Tie2, HIF-1α, and FAK. Moreover, FS145 also inhibited aortic vessel sprout and showed strong anti-angiogenic activities as assessed ex vivo, by employing the rat aortic ring assay, chick embryo chorioallantoic membrane, and zebrafish embryo models. Altogether, our results suggest that FS145 suppresses angiogenesis ex vivo and in vitro by blocking integrin αvβ3. The current study reveals the first anti-angiogenesis disintegrin with WGD motif from invertebrates and provides a beneficial pharmacological activity to inhibit abnormal angiogenesis.

A minireview of the medicinal and edible insects from the traditional Chinese medicine (TCM)

Entomoceuticals define a subset of pharmaceuticals derived from insects. The therapeutic effect of insect-derived drugs has been empirically validated by the direct use of various folk medicines originating from three sources in particular: the glandular secretions of insects (e.g., silk, honey, venom), the body parts of the insect or the whole used live or by various processing (e.g., cooked, toasted, ground), and active ingredients extracted from insects or insect-microbe symbiosis. Insects have been widely exploited in traditional Chinese medicine (TCM) relative to other ethnomedicines, especially in the prospect of insect species for medicinal uses. It is noticeable that most of these entomoceuticals are also exploited as health food for improving immune function. In addition, some edible insects are rich in animal protein and have high nutritional value, which are used in the food field, such as insect wine, health supplements and so on. In this review, we focused on 12 insect species that have been widely used in traditional Chinese herbal formulae but have remained less investigated for their biological properties in previous studies. We also combined the entomoceutical knowledge with recent advances in insect omics. This review specifies the underexplored medicinal insects from ethnomedicine and shows their specific medicinal and nutritional roles in traditional medicine.

A Deeper Insight into the Tick Salivary Protein Families under the Light of Alphafold2 and Dali: Introducing the TickSialoFam 2.0 Database

Hard ticks feed for several days or weeks on their hosts and their saliva contains thousands of polypeptides belonging to dozens of families, as identified by salivary transcriptomes. Comparison of the coding sequences to protein databases helps to identify putative secreted proteins and their potential functions, directing and focusing future studies, usually done with recombinant proteins that are tested in different bioassays. However, many families of putative secreted peptides have a unique character, not providing significant matches to known sequences. The availability of the Alphafold2 program, which provides in silico predictions of the 3D polypeptide structure, coupled with the Dali program which uses the atomic coordinates of a structural model to search the Protein Data Bank (PDB) allows another layer of investigation to annotate and ascribe a functional role to proteins having so far being characterized as "unique". In this study, we analyzed the classification of tick salivary proteins under the light of the Alphafold2/Dali programs, detecting novel protein families and gaining new insights relating the structure and function of tick salivary proteins.

Cloning, Expression and Inhibitory Effects on Lewis Lung Carcinoma Cells of rAj-Tspin from Sea Cucumber (Apostichopus japonicus)

In recent years, sea cucumber has become a favorite healthcare food due to its characteristic prevention of cardiovascular diseases, suppression of tumors, as well as enhancement of immunity. In order to screen the anti-tumoral proteins or peptides from sea cucumber (Apostichopus japonicus), its cDNA library was analyzed, and a disintegrin-like and metalloproteinase with thrombospondin type 1 motif, member 13 (ADAMTS13)-like was found. ADAMTS13-like contains 10 thrombospondin 1 (TSP1) domains. Based on analysis of bioinformatics, the third TSP1 domain of this protein, which is further named Aj-Tspin, contains an arginine-glycine-aspartate (RGD) motif. Since our previous studies showed that the recombinant RGD-containing peptide from lampreys showed anti-tumoral activity, the third TSP1 domain of ADAMTS13-like was chosen to evaluate it's effect on tumor proliferation and metastasis, despite the fact it shares almost no homologue with disintegrins from other species. After artificial synthesis, its cDNA sequence, Aj-Tspin, which is composed of 56 amino acids, was subcloned into a pET23b vector and expressed as a recombinant Aj-Tspin (rAj-Tspin) in a soluble form with a molecular weight of 6.976 kDa. Through affinity chromatography, rAj-Tspin was purified as a single protein. Both anti-proliferation and immunofluorescence assays showed that rAj-Tspin suppressed the proliferation of Lewis lung carcinoma (LLC) cells through apoptosis. Adhesion assay also displayed that rAj-Tspin inhibited the adhesion of LLC cells to ECM proteins, including fibronectin, laminin, vitronectin and collagen. Lastly, rAj-Tspin also suppressed the migration and invasion of LLC cells across the filter in transwells. Thus, the above indicates that rAj-Tspin might act as a potential anti-tumoral drug in the future and could also provide information on the nutritional value of sea cucumber.

Vitronectin stabilizes intravascular adhesion of neutrophils by coordinating β2 integrin clustering

The recruitment of neutrophils from the microvasculature to the site of injury or infection represents a key event in the inflammatory response. Vitronectin (VN) is a multifunctional macromolecule abundantly present in blood and extracellular matrix. The role of this glycoprotein in the extravasation process of circulating neutrophils remains elusive. Employing advanced in vivo/ex vivo imaging techniques in different mouse models as well as in vitro methods, we uncovered a previously unrecognized function of VN in the transition of dynamic to static intravascular interactions of neutrophils with microvascular endothelial cells. These distinct properties of VN require the heteromerization of this glycoprotein with plasminogen activator inhibitor-1 (PAI- 1) on the activated venular endothelium and subsequent interactions of this protein complex with the scavenger receptor low-density lipoprotein receptor-related protein-1 on intravascularly adhering neutrophils. This induces p38 mitogen-activated protein kinases-dependent intracellular signaling events which, in turn, regulates the proper clustering of the b2 integrin lymphocyte function associated antigen-1 on the surface of these immune cells. As a consequence of this molecular interplay, neutrophils become able to stabilize their adhesion to the microvascular endothelium and, subsequently, to extravasate to the perivascular tissue. Hence, endothelial-bound VN-PAI-1 heteromers stabilize intravascular adhesion of neutrophils by coordinating b2 integrin clustering on the surface of these immune cells, thereby effectively controlling neutrophil trafficking to inflamed tissue. Targeting this protein complex might be beneficial for the prevention and treatment of inflammatory pathologies.

FM-CATH, A Novel Cathelicidin From Fejervarya Multistriata, Shows Therapeutic Potential for Treatment of CLP-Induced Sepsis

Sepsis is an exacerbated inflammatory reaction induced by severe infection. As important defensive molecules in innate immunity, several AMPs are reported to prevent septic shock. In this study, we characterized a novel cathelicidin, FM-CATH, from the frog skin of F. multistriata. FM-CATH was found to adopt an amphipathic α-helix structural in membrane-mimetic environments and possess favorable antimicrobial effects against bacteria and fungus. In addition, it triggered the agglutination of bacteria. It could also strongly bind to LPS and LTA. Additionally, FM-CATH affected the enzymatic activities of thrombin, plasmin, β-tryptase, and tPA, leading to coagulation inhibition in vitro and in vivo. Finally, we observed that FM-CATH improved survival rate and inhibited pathological alteration, bacterial count, serum biochemistry, and pro-inflammatory cytokine expression in the cecal ligation and puncture-induced sepsis mice. Taken together, these findings suggest that FM-CATH might be served as a promising agent for the treatment of sepsis.

Characterization and functional analysis of cathelicidin-MH, a novel frog-derived peptide with anti-septicemic properties

Antimicrobial peptides form part of the innate immune response and play a vital role in host defense against pathogens. Here we report a new antimicrobial peptide belonging to the cathelicidin family, cathelicidin-MH (cath-MH), from the skin of Microhyla heymonsivogt frog. Cath-MH has a single α-helical structure in membrane-mimetic environments and is antimicrobial against fungi and bacteria, especially Gram-negative bacteria. In contrast to other cathelicidins, cath-MH suppresses coagulation by affecting the enzymatic activities of tissue plasminogen activator, plasmin, β-tryptase, elastase, thrombin, and chymase. Cath-MH protects against lipopolysaccharide (LPS)- and cecal ligation and puncture-induced sepsis, effectively ameliorating multiorgan pathology and inflammatory cytokine through its antimicrobial, LPS-neutralizing, coagulation suppressing effects as well as suppression of MAPK signaling. Taken together, these data suggest that cath-MH is an attractive candidate therapeutic agent for the treatment of septic shock.

Exogenous Integrin αIIbβ3 Inhibitors Revisited: Past, Present and Future Applications

The integrin αIIbβ3 is the most abundant integrin on platelets. Upon platelet activation, the integrin changes its conformation (inside-out signalling) and outside-in signalling takes place leading to platelet spreading, platelet aggregation and thrombus formation. Bloodsucking parasites such as mosquitoes, leeches and ticks express anticoagulant and antiplatelet proteins, which represent major sources of lead compounds for the development of useful therapeutic agents for the treatment of haemostatic disorders or cardiovascular diseases. In addition to hematophagous parasites, snakes also possess anticoagulant and antiplatelet proteins in their salivary glands. Two snake venom proteins have been developed into two antiplatelet drugs that are currently used in the clinic. The group of proteins discussed in this review are disintegrins, low molecular weight integrin-binding cysteine-rich proteins, found in snakes, ticks, leeches, worms and horseflies. Finally, we highlight various oral antagonists, which have been tested in clinical trials but were discontinued due to an increase in mortality. No new αIIbβ3 inhibitors are developed since the approval of current platelet antagonists, and structure-function analysis of exogenous disintegrins could help find platelet antagonists with fewer adverse side effects.

The functions of CAP superfamily proteins in mammalian fertility and disease

BACKGROUND

Members of the cysteine-rich secretory proteins (CRISPS), antigen 5 (Ag5) and pathogenesis-related 1 (Pr-1) (CAP) superfamily of proteins are found across the bacterial, fungal, plant and animal kingdoms. Although many CAP superfamily proteins remain poorly characterized, over the past decade evidence has accumulated, which provides insights into the functional roles of these proteins in various processes, including fertilization, immune defence and subversion, pathogen virulence, venom toxicology and cancer biology.

OBJECTIVE AND RATIONALE

The aim of this article is to summarize the current state of knowledge on CAP superfamily proteins in mammalian fertility, organismal homeostasis and disease pathogenesis.

SEARCH METHODS

The scientific literature search was undertaken via PubMed database on all articles published prior to November 2019. Search terms were based on following keywords: 'CAP superfamily', 'CRISP', 'Cysteine-rich secretory proteins', 'Antigen 5', 'Pathogenesis-related 1', 'male fertility', 'CAP and CTL domain containing', 'CRISPLD1', 'CRISPLD2', 'bacterial SCP', 'ion channel regulator', 'CatSper', 'PI15', 'PI16', 'CLEC', 'PRY proteins', 'ASP proteins', 'spermatogenesis', 'epididymal maturation', 'capacitation' and 'snake CRISP'. In addition to that, reference lists of primary and review article were reviewed for additional relevant publications.

OUTCOMES

In this review, we discuss the breadth of knowledge on CAP superfamily proteins with regards to their protein structure, biological functions and emerging significance in reproduction, health and disease. We discuss the evolution of CAP superfamily proteins from their otherwise unembellished prokaryotic predecessors into the multi-domain and neofunctionalized members found in eukaryotic organisms today. At least in part because of the rapid evolution of these proteins, many inconsistencies in nomenclature exist within the literature. As such, and in part through the use of a maximum likelihood phylogenetic analysis of the vertebrate CRISP subfamily, we have attempted to clarify this confusion, thus allowing for a comparison of orthologous protein function between species. This framework also allows the prediction of functional relevance between species based on sequence and structural conservation.

WIDER IMPLICATIONS

This review generates a picture of critical roles for CAP proteins in ion channel regulation, sterol and lipid binding and protease inhibition, and as ligands involved in the induction of multiple cellular processes.

Necator americanus Ancylostoma Secreted Protein-2 (Na-ASP-2) Binds an Ascaroside (ascr#3) in Its Fatty Acid Binding Site

During their infective stages, hookworms release excretory-secretory (E-S) products, small molecules, and proteins to help evade and suppress the host's immune system. Small molecules found in E-S products of mammalian hookworms include nematode derived metabolites like ascarosides, which are composed of the sugar ascarylose linked to a fatty acid side chain. The most abundant proteins found in hookworm E-S products are members of the protein family known as Ancylostoma secreted protein (ASP). In this study, two ascarosides and their fatty acid moieties were synthesized and tested for in vitro binding to Na-ASP-2 using both a ligand competition assay and microscale thermophoresis. The fatty acid moieties of both ascarosides tested and ascr#3, an ascaroside found in rat hookworm E-S products, bind to Na-ASP-2's palmitate binding cavity. These molecules were confirmed to bind to the palmitate but not the sterol binding sites. An ascaroside, oscr#10, which is not found in hookworm E-S products, does not bind to Na-ASP-2. More studies are required to determine the structural basis of ascarosides binding by Na-ASP-2 and to understand the physiological significance of these observations.

Salivary complement inhibitors from mosquitoes: Structure and mechanism of action

Inhibition of the alternative pathway (AP) of complement by saliva from Anopheles mosquitoes facilitates feeding by blocking production of the anaphylatoxins C3a and C5a, which activate mast cells leading to plasma extravasation, pain, and itching. We have previously shown that albicin, a member of the SG7 protein family from An. Albimanus, blocks the AP by binding to and inhibiting the function of the C3 convertase, C3bBb. Here we show that SG7.AF, the albicin homolog from An. freeborni, has a similar potency to albicin but is more active in the presence of properdin, a plasma protein that acts to stabilize C3bBb. Conversely, albicin is highly active in the absence or presence of properdin. Albicin and SG7.AF stabilize the C3bBb complex in a form that accumulates on surface plasmon resonance (SPR) surfaces coated with properdin, but SG7.AF binds with lower affinity than albicin. Albicin induces oligomerization of the complex in solution, suggesting that it is oligomerization that leads to stabilization on SPR surfaces. Anophensin, the albicin ortholog from An. stephensi, is only weakly active as an inhibitor of the AP, suggesting that the SG7 family may play a different functional role in this species and other species of the subgenus Cellia, containing the major malaria vectors in Africa and Asia. Crystal structures of albicin and SG7.AF reveal a novel four-helix bundle arrangement that is stabilized by an N-terminal hydrogen bonding network. These structures provide insight into the SG7 family and related mosquito salivary proteins including the platelet-inhibitory 30 kDa family.

Disintegrin Tablysin-15 Suppresses Cancer Hallmarks in Melanoma Cells by Blocking FAK/Akt/ERK and NF-κB Signaling

BACKGROUND

Integrins are crucial anti-cancer therapy targets. We previously showed that tablysin-15 is an integrin antagonist with its Arg-Gly-Asp motif in a novel structural context.

OBJECTIVE

Here we investigated the anti-cancer effects and mechanisms of action of tablysin-15 in melanoma cells.

METHODS

Cell adhesion, competitive binding, cell viability, and ATP chemiluminescence assays were used to analyze the binding of tablysin-15 to αvβ3 integrin and its phenotypic effects. Wound healing, transwells, and zymography were performed to detect motility and matrix metalloproteinase- 2/-9 activities. PARP and caspase-3 cleavage were used as apoptosis assays, while LDH release and flow cytometry were used for necrosis and cell cycle analysis. The expression of mRNAs and proteins of target molecules was measured by qRT-PCR and western blotting, respectively.

RESULTS

Tablysin-15 dose-dependently inhibited the proliferation, migration, and invasion of M21 cells through integrin αvβ3. The proliferation inhibition caused by tablysin-15 was attributable to G0/G1 phase arrest rather than apoptosis or necrosis. Furthermore, tablysin-15 suppressed MMP-2/- 9 activities and the mRNA expression of MMP-2/-9 and COX-2 but was upregulated TIMP-1 in M21 cells. Meanwhile, tablysin-15 suppressed the expression of cyclin D1/E and CDK 2/6, the phosphorylation of FAK, Akt, and ERK, and nuclear translocation of NF-κB, while increasing the expression of the CDK inhibitor p21waf1/C1. Taken together, tablysin-15 might inhibit melanoma cell metastasis and proliferation by competing with αvβ3 integrin, thereby blocking FAK-associated signaling pathways and nuclear translocation of NF-κB.

CONCLUSION

Tablysin-15 has reliable anti-cancer effects against M21 melanoma cells, suggesting tablysin-15 is a promising anti-tumor drug.

Standardization and Validation of Fluorescence-Based Quantitative Assay to Study Human Platelet Adhesion to Extracellular-Matrix in a 384-Well Plate

Platelets play a crucial role in the immunological response and are involved in the pathological settings of vascular diseases, and their adhesion to the extracellular matrix is important to bring leukocytes close to the endothelial cells and to form and stabilize the thrombus. Currently there are several methods to study platelet adhesion; however, the optimal parameters to perform the assay vary among studies, which hinders their comparison and reproducibility. Here, a standardization and validation of a fluorescence-based quantitative adhesion assay to study platelet-ECM interaction in a high-throughput screening format is proposed. Our study confirms that fluorescence-based quantitative assays can be effectively used to detect platelet adhesion, in which BCECF-AM presents the highest sensitivity in comparison to other dyes.

Tablysin-15 inhibits osteoclastogenesis and LPS-induced bone loss via attenuating the integrin αvβ3 pathway

Excessive osteoclast leads to the imbalance in bone reconstruction and results in osteolytic diseases, such as osteoporosis and rheumatic arthritis. Integrin α_vβ₃ abundantly expresses on osteoclast and plays a critical role in the formation and function of osteoclast, therefore, blockage of α_vβ₃ has become an attractive therapeutic option for osteolytic diseases. In this study, we find that Tablysin-15, a RGD motif containing disintegrin, concentration-dependently suppresses RANKL-induced osteoclastogenesis, F-actin ring formation and bone resorption without affecting the cell viabilities. Tablysin-15 binds to integrin α_vβ₃ and inhibits the activation of FAK-associated signaling pathways. Tablysin-15 also suppresses the activation of NF-кB, MAPK, and Akt-NFATc1 signaling pathways, which are crucial transcription factors during osteoclast differentiation. Moreover, Tablysin-15 decreases the osteoclastogenesis marker gene expression, including MMP-9, TRAP, CTSK, and c-Src. Finally, Tablysin-15 significantly inhibits LPS-induced bone loss in a mouse model. Taken together, our results indicate that Tablysin-15 significantly suppresses osteoclastogenesis in vitro and in vivo, thus it might be a excellent candidate for treating osteolytic-related diseases.

In-vitro effects of the FS50 protein from salivary glands of Xenopsylla cheopis on voltage-gated sodium channel activity and motility of MDA-MB-231 human breast cancer cells

Voltage-gated sodium channel activity enhances the motility and oncogene expression of metastasic cancer cells that express a neonatal alternatively spliced form of the NaV1.5 isoform. We reported previously that FS50, a salivary protein from Xenopsylla cheopis, showed inhibitory activity against the NaV1.5 channel when assayed in HEK 293T cells and antiarrhythmia effects on rats and monkeys after induction of arrhythmia by BaCl2. This study aims to identify the effect of FS50 on voltage-gated sodium channel activity and the motility of MDA-MB-231 human breast cancer cells in vitro. NaV1.5 was abnormally expressed in the highly metastatic breast cancer cell line MDA-MB-231, but not in the MCF-7 cell line. FS50 significantly inhibited sodium current, migration, and invasion in a dose-dependent manner, but had no effect on the proliferation of MDA-MB-231 cells at the working concentrations (1.5-12 μmol/l) after a long-term treatment for 48 h. Meanwhile, FS50 decreased NaV1.5 mRNA expression without altering the total protein level in MDA-MB-231 cells. Correspondingly, the results also showed that MMP-9 activity and the ratio of MMP-9 mRNA to TIMP-1 mRNA were markedly decreased by FS50. Taken together, our findings highlighted for the first time an inhibitory effect of a salivary protein from a blood-feeding arthropod on breast cancer cells through the NaV1.5 channel. Furthermore, this study provided a new candidate leading molecule against antitumor cells expressing NaV1.5.

An insight into the sialome, mialome and virome of the horn fly, Haematobia irritans

BACKGROUND

The horn fly (Haematobia irritans) is an obligate blood feeder that causes considerable economic losses in livestock industries worldwide. The control of this cattle pest is mainly based on insecticides; unfortunately, in many regions, horn flies have developed resistance. Vaccines or biological control have been proposed as alternative control methods, but the available information about the biology or physiology of this parasite is rather scarce.

RESULTS

We present a comprehensive description of the salivary and midgut transcriptomes of the horn fly (Haematobia irritans), using deep sequencing achieved by the Illumina protocol, as well as exploring the virome of this fly. Comparison of the two transcriptomes allow for identification of uniquely salivary or uniquely midgut transcripts, as identified by statistically differential transcript expression at a level of 16 x or more. In addition, we provide genomic highlights and phylogenetic insights of Haematobia irritans Nora virus and present evidence of a novel densovirus, both associated to midgut libraries of H. irritans.

CONCLUSIONS

We provide a catalog of protein sequences associated with the salivary glands and midgut of the horn fly that will be useful for vaccine design. Additionally, we discover two midgut-associated viruses that infect these flies in nature. Future studies should address the prevalence, biological effects and life cycles of these viruses, which could eventually lead to translational work oriented to the control of this economically important cattle pest.

An insight into the sialotranscriptome and virome of Amazonian anophelines

Background

Saliva of mosquitoes contains anti-platelet, anti-clotting, vasodilatory, anti-complement and anti-inflammatory substances that help the blood feeding process. The salivary polypeptides are at a fast pace of evolution possibly due to their relative lack of structural constraint and possibly also by positive selection on their genes leading to evasion of host immune pressure.

Results

In this study, we used deep mRNA sequence to uncover for the first time the sialomes of four Amazonian anophelines species (Anopheles braziliensis, A. marajorara, A. nuneztovari and A. triannulatus) and extend the knowledge of the A. darlingi sialome. Two libraries were generated from A. darlingi mosquitoes, sampled from two localities separated ~ 1100 km apart. A total of 60,016 sequences were submitted to GenBank, which will help discovery of novel pharmacologically active polypeptides and the design of specific immunological markers of mosquito exposure. Additionally, in these analyses we identified and characterized novel phasmaviruses and anpheviruses associated to the sialomes of A. triannulatus, A. marajorara and A. darlingi species.

Conclusions

Besides their pharmacological properties, which may be exploited for the development of new drugs (e.g. anti-thrombotics), salivary proteins of blood feeding arthropods may be turned into tools to prevent and/or better control vector borne diseases; for example, through the development of vaccines or biomarkers to evaluate human exposure to vector bites. The sialotranscriptome study reported here provided novel data on four New World anopheline species and allowed to extend our knowledge on the salivary repertoire of A. darlingi. Additionally, we discovered novel viruses following analysis of the transcriptomes, a procedure that should become standard within future RNAseq studies.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5545-0) contains supplementary material, which is available to authorized users.

The anticancer properties and mechanism of action of tablysin-15, the RGD-containing disintegrin, in breast cancer cells

α_vβ₃ integrin expressed on cancer cell surfaces is associated with important cancer hallmarks including survival and metastasis and is thus a potential anticancer drug target. Tablysin-15 contains the RGD motif and is a high-affinity α_vβ₃ integrin antagonist. The aim of this study was to investigate the antitumor effect and mechanism of action of tablysin-15 against α_vβ₃ integrin high-expressing breast cancer cell lines in vitro and in vivo. Tablysin-15 dose-dependently inhibited the proliferation, migration, and invasion of two breast cancer cell lines via the α_vβ₃ integrin in vitro. Proliferation inhibition was attributable to G0/G1 phase cell cycle arrest rather than apoptosis or necrosis. Furthermore, tablysin-15 downregulated the activity and mRNA expression of MMP-2/-9, VEGF, and COX-2 but upregulated TIMP-1/-2 mRNA in both cell lines. Further, tablysin-15 suppressed the expression of CDK2, CDK6, cyclin D1, and cyclin E, the phosphorylation of FAK, Akt, GSK-3β, and ERK, and the nuclear translocation of NF-κB while increasing the expression of the CDK inhibitor p21^waf1/C1. Lastly, tablysin-15 provided effective antitumor protection in vivo. Thus, tablysin-15 inhibits the metastasis and proliferation of breast cancer cells through binding α_vβ₃ integrin and blocking FAK-associated signaling pathways as well as nuclear translocation of NF-κB.

Vampire Venom: Vasodilatory Mechanisms of Vampire Bat (Desmodus rotundus) Blood Feeding

Animals that specialise in blood feeding have particular challenges in obtaining their meal, whereby they impair blood hemostasis by promoting anticoagulation and vasodilation in order to facilitate feeding. These convergent selection pressures have been studied in a number of lineages, ranging from fleas to leeches. However, the vampire bat (Desmondus rotundus) is unstudied in regards to potential vasodilatory mechanisms of their feeding secretions (which are a type of venom). This is despite the intense investigations of their anticoagulant properties which have demonstrated that D. rotundus venom contains strong anticoagulant and proteolytic activities which delay the formation of blood clots and interfere with the blood coagulation cascade. In this study, we identified and tested a compound from D. rotundus venom that is similar in size and amino acid sequence to human calcitonin gene-related peptide (CGRP) which has potent vasodilatory properties. We found that the vampire bat-derived form of CGRP (i.e., vCGRP) selectively caused endothelium-independent relaxation of pre-contracted rat small mesenteric arteries. The vasorelaxant efficacy and potency of vCGRP were similar to that of CGRP, in activating CGRP receptors and Kv channels to relax arteriole smooth muscle, which would facilitate blood meal feeding by promoting continual blood flow. Our results provide, for the first time, a detailed investigation into the identification and function of a vasodilatory peptide found in D. rotundus venom, which provides a basis in understanding the convergent pathways and selectivity of hematophagous venoms. These unique peptides also show excellent drug design and development potential, thus highlighting the social and economic value of venomous animals.

A Short Half-Life αIIbβ₃ Antagonist ANTP266 Reduces Thrombus Formation

Integrin α_IIbβ₃ plays a pivotal role in platelet aggregation. Three α_IIbβ₃ antagonists have been approved by the Food and Drug Administration (FDA) for the treatment of cardiovascular diseases. Unfortunately, all of these three drugs can cause the side effect of severe bleeding. Therefore, developing a new α_IIbβ₃ antagonist with low bleeding was needed. In the present study, we screened compounds by using a fibrinogen/integrin α_IIbβ₃ enzyme-linked immunosorbent assay (ELISA), and a novel α_IIbβ₃ antagonist ANTP266 was attained. The antithrombotic effects of ANTP266 were estimated by using two animal models, the bleeding risk was estimated by using a mice tail cutting assay, and the plasma half-life time was tested by LC-MS/MS. The results showed that ANTP266 potently decreased thrombosis formation, while not prolonging bleeding time at its effective dosage. The bleeding of ANTP266 reduced rapidly as time went on from 5 to 60 min, but tirofiban produced high bleeding continuously. The plasma half-life of ANTP266 in rats was 10.8 min. Taken together, ANTP266 is an effective antithrombotic agent with a low bleeding risk. The shorter bleeding time benefits from its short plasma half-life. ANTP266 could be a candidate for developing the α_IIbβ₃ antagonist of rapid elimination for a patient undergoing percutaneous coronary intervention.

Crystal structure of Brugia malayi venom allergen-like protein-1 (BmVAL-1), a vaccine candidate for lymphatic filariasis

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The vaccine candidate Brugia malayi venom allergen-like 1 protein (BmVAL-1) has three distinct binding cavities.

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The cavities are the central cavity; the sterol-binding caveolin-binding motif (CBM); and the palmitate-binding cavity.

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These cavities are connected by channels, which can accommodate water molecules, ions and small ligands.

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The channels explain how blocking divalent ions in the central cavity affects sterol binding in the distinct CBM cavity.

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BmVAL-1 has a glycosylated CBM, is an effective sterol transporter in vivo and binds cholesterol and palmitate in vitro.

Brugia malayi is a causative agent of lymphatic filariasis, a major tropical disease. The infective L3 parasite stage releases immunomodulatory proteins including the venom allergen-like proteins (VALs), which are members of the SCP/TAPS (Sperm-coating protein/Tpx/antigen 5/pathogenesis related-1/Sc7) superfamily. BmVAL-1 is a major target of host immunity with >90% of infected B. malayi microfilaraemic cases being seropositive for antibodies to BmVAL-1. This study is part of ongoing efforts to characterize the structures and functions of important B. malayi proteins. Recombinant BmVAL-1 was produced using a plant expression system, crystallized and the structure was solved by molecular replacement and refined to 2.1 Å, revealing the characteristic alpha/beta/alpha sandwich topology of eukaryotic SCP/TAPS proteins. The protein has more than 45% loop regions and these flexible loops connect the helices and strands, which are longer than predicted based on other parasite SCP/TAPS protein structures. The large central cavity of BmVAL-1 is a prototypical CRISP cavity with two histidines required to bind divalent cations. The caveolin-binding motif (CBM) that mediates sterol binding in SCP/TAPS proteins is large and open in BmVAL-1 and is N-glycosylated. N-glycosylation of the CBM does not affect the ability of BmVAL-1 to bind sterol in vitro. BmVAL-1 complements the in vivo sterol export phenotype of yeast mutants lacking their endogenous SCP/TAPS proteins. The in vitro sterol-binding affinity of BmVAL-1 is comparable with Pry1, a yeast sterol transporting SCP/TAPS protein. Sterol binding of BmVAL-1 is dependent on divalent cations. BmVAL-1 also has a large open palmitate-binding cavity, which binds palmitate comparably to tablysin-15, a lipid-binding SCP/TAPS protein. The central cavity, CBM and palmitate-binding cavity of BmVAL-1 are interconnected within the monomer with channels that can serve as pathways for water molecules, cations and small molecules.

Heligmosomoides polygyrus Venom Allergen-like Protein-4 (HpVAL-4) is a sterol binding protein

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Heligmosomoides polygyrus Venom Allergen-like Protein-4 (HpVAL-4) was produced in plants as a glycosylated protein.

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The crystal structure of HpVAL-4 was solved and reveals three distinct cavities.

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These cavities are the central cavity; the sterol-binding caveolin-binding motif (CBM); and the palmitate-binding cavity.

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The central cavity of Hp-VAL-4 lacks the characteristic histidines that coordinate divalent cations.

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Hp-VAL-4 binds sterol in vivo and in vitro.

Heligmosomoides polygyrus bakeri is a model parasitic hookworm used to study animal and human helminth diseases. During infection, the parasite releases excretory/secretory products that modulate the immune system of the host. The most abundant protein family in excretory/secretory products comprises the venom allergen-like proteins (VALs), which are members of the SCP/TAPS (sperm-coating protein/Tpx/antigen 5/pathogenesis related-1/Sc7) superfamily. There are >30 secreted Heligmosomoides polygyrus VAL proteins (HpVALs) and these proteins are characterised by having either one or two 15 kDa CAP (cysteine-rich secretory protein (CRISP)/antigen 5/pathogenesis related-1) domains. The first known HpVAL structure, HpVAL-4, refined to 1.9 Å is reported. HpVAL-4 was produced as a homogeneously glycosylated protein in leaves of Nicotiana benthamiana infiltrated with recombinant plasmids, making this plant expression platform amenable for the production of biological products. The overall topology of HpVAL-4 is a three layered αβα sandwich between a short N-terminal loop and a C-terminal cysteine rich extension. The C-terminal cysteine rich extension has two strands stabilized by two disulfide bonds and superposes well with the previously reported extension from the human hookworm Necator americanus Ancylostoma secreted protein-2 (Na-ASP-2). The N-terminal loop is connected to alpha helix 2 via a disulfide bond previously observed in Na-ASP-2. HpVAL-4 has a central cavity that is more similar to the N-terminal CAP domain of the two CAP Na-ASP-1 from Necator americanus. Unlike Na-ASP-2, mammalian CRISP, and the C-terminal CAP domain of Na-ASP-1, the large central cavity of HpVAL-4 lacks the two histidines required to coordinate divalent cations. HpVAL-4 has both palmitate-binding and sterol-binding cavities and is able to complement the in vivo sterol export phenotype of yeast mutants lacking their endogenous CAP proteins. More studies are required to determine endogenous binding partners of HpVAL-4 and unravel the possible impact of sterol binding on immune-modulatory functions.

Beyond the Matrix: The Many Non-ECM Ligands for Integrins

The traditional view of integrins portrays these highly conserved cell surface receptors as mediators of cellular attachment to the extracellular matrix (ECM), and to a lesser degree, as coordinators of leukocyte adhesion to the endothelium. These canonical activities are indispensable; however, there is also a wide variety of integrin functions mediated by non-ECM ligands that transcend the traditional roles of integrins. Some of these unorthodox roles involve cell-cell interactions and are engaged to support immune functions such as leukocyte transmigration, recognition of opsonization factors, and stimulation of neutrophil extracellular traps. Other cell-cell interactions mediated by integrins include hematopoietic stem cell and tumor cell homing to target tissues. Integrins also serve as cell-surface receptors for various growth factors, hormones, and small molecules. Interestingly, integrins have also been exploited by a wide variety of organisms including viruses and bacteria to support infectious activities such as cellular adhesion and/or cellular internalization. Additionally, the disruption of integrin function through the use of soluble integrin ligands is a common strategy adopted by several parasites in order to inhibit blood clotting during hematophagy, or by venomous snakes to kill prey. In this review, we strive to go beyond the matrix and summarize non-ECM ligands that interact with integrins in order to highlight these non-traditional functions of integrins.

rLj-RGD3 Suppresses the Growth of HeyA8 Cells in Nude Mice

In the previous study, rLj-RGD3, a recombinant toxin protein which contains three RGD motifs, was reported to not only inhibit the proliferation of an ovarian cancer cell line, HeyA8 cells, by inducing apoptosis, but also block their adhesion, migration and invasion processes. However, whether rLj-RGD3 could also suppress the tumor growth in HeyA8 xenografted mice has not been reported yet. In the present study, rLj-RGD3 was intraperitoneally injected in the nude mice bearing HeyA8 tumors. Compared with the control group (normal saline), rLj-RGD3 inhibited the tumor growth significantly in the HeyA8 xenografted mice in a dose-dependent manner without affecting their body weights. Based on the H&E, Hoechst 33258 and TUNEL staining assays, as well as western blot analysis, rLj-RGD3 reduced the weight and volume of the solid tumors, probably by disturbing the tissue structure, inducing apoptosis and suppressing the FAK/PI3K/AKT pathway. Most importantly, rLj-RGD3 was found to prolong the survival days of the ovarian tumor xenografted mice, which suggested rLj-RGD3 might act as an effective and safe drug to treat ovarian cancer patients.

Crystal Structure of Borrelia turicatae protein, BTA121, a differentially regulated gene in the tick-mammalian transmission cycle of relapsing fever spirochetes

Tick-borne relapsing fever (RF) borreliosis is a neglected disease that is often misdiagnosed. RF species circulating in the United States include Borrelia turicatae, which is transmitted by argasid ticks. Environmental adaptation by RF Borrelia is poorly understood, however our previous studies indicated differential regulation of B. turicatae genes localized on the 150 kb linear megaplasmid during the tick-mammalian transmission cycle, including bta121. This gene is up-regulated by B. turicatae in the tick versus the mammal, and the encoded protein (BTA121) is predicted to be surface localized. The structure of BTA121 was solved by single-wavelength anomalous dispersion (SAD) using selenomethionine-derivative protein. The topology of BTA121 is unique with four helical domains organized into two helical bundles. Due to the sequence similarity of several genes on the megaplasmid, BTA121 can serve as a model for their tertiary  structures. BTA121 has large interconnected tunnels and cavities that can accommodate ligands, notably long parallel helices, which have a large hydrophobic central pocket. Preliminary in-vitro studies suggest that BTA121 binds lipids, notably palmitate with a similar order of binding affinity as tablysin-15, a known palmitate-binding protein. The reported data will guide mechanistic studies to determine the role of BTA121 in the tick-mammalian transmission cycle of B. turicatae.

Crystal Structure of MpPR-1i, a SCP/TAPS protein from Moniliophthora perniciosa, the fungus that causes Witches' Broom Disease of Cacao

The pathogenic fungi Moniliophthora perniciosa causes Witches’ Broom Disease (WBD) of cacao. The structure of MpPR-1i, a protein expressed by M. perniciosa when it infects cacao, are presented. This is the first reported de novo structure determined by single-wavelength anomalous dispersion phasing upon soaking with selenourea. Each monomer has flexible loop regions linking the core alpha-beta-alpha sandwich topology that comprise ~50% of the structure, making it difficult to generate an accurate homology model of the protein. MpPR-1i is monomeric in solution but is packed as a high ~70% solvent content, crystallographic heptamer. The greatest conformational flexibility between monomers is found in loops exposed to the solvent channel that connect the two longest strands. MpPR-1i lacks the conserved CAP tetrad and is incapable of binding divalent cations. MpPR-1i has the ability to bind lipids, which may have roles in its infection of cacao. These lipids likely bind in the palmitate binding cavity as observed in tablysin-15, since MpPR-1i binds palmitate with comparable affinity as tablysin-15. Further studies are required to clarify the possible roles and underlying mechanisms of neutral lipid binding, as well as their effects on the pathogenesis of M. perniciosa so as to develop new interventions for WBD.

A Naphthalenic Derivative ND-1 Inhibits Thrombus Formation by Interfering the Binding of Fibrinogen to Integrin αIIbβ3

Integrin αIIbβ3 plays a crucial role in the process of platelet aggregation. Three integrin αIIbβ3 antagonists (abciximab, eptifibatide, and tirofiban) have been approved by FDA for clinical use. Unfortunately, they all showed severe side effects such as thrombocytopenia and bleeding risk. Thus, researches on the development of more effective and safer antiplatelet agents are needed. In this manuscript we reported a novel naphthalenic derivative compound ND-1 with potent antithrombotic effect and lower bleeding risk. ND-1 inhibited ADP-, collagen-, thrombin-, and U46619-induced platelet aggregation with IC₅₀ values of 1.29, 14.46, 12.84, and 40.24 μM, respectively. Mechanism studies indicated that ND-1 inhibited the binding of fibrinogen to integrin αIIbβ3 in a dose-dependent manner with an IC₅₀ value of 3.12 μM. ND-1 inhibited P-selectin expression induced by ADP, collagen, thrombin, and U46619 on the surface of platelets. Additionally, this compound reduced platelets spreading to the immobilized fibrinogen. In vivo, ND-1 potently decreased thrombus formation in an arteriovenous shunt thrombosis model in rats and slightly prolonged bleeding time in a tail cutting model in mice. Taken together, our results reveal that ND-1 is a novel antagonist of αIIbβ3 with strong antithrombotic effect and lower bleeding risk.

The pyrrolidinoindoline alkaloid Psm2 inhibits platelet aggregation and thrombus formation by affecting PI3K/Akt signaling

AIM

Psm2, one of the pyrrolidinoindoline alkaloids isolated from whole Selaginella moellendorffii plants, has shown a potent antiplatelet activity. In this study, we further evaluated the antiplatelet effects of Psm2, and elucidated the underlying mechanisms.

METHODS

Human platelet aggregation in vitro and rat platelet aggregation ex vivo were investigated. Agonist-induced platelet aggregation was measured using a light transmission aggregometer. The antithrombotic effects of Psm2 were evaluated in arteriovenous shunt thrombosis model in rats. To elucidate the mechanisms underlying the antiplatelet activity of Psm2, ELISAs, Western blotting and molecular docking were performed. The bleeding risk of Psm2 administration was assessed in a mouse tail cutting model, and the cytotoxicity of Psm2 was measured with MTT assay in EA.hy926 cells.

RESULTS

Psm2 dose-dependently inhibited human platelet aggregation induced by ADP, U4619, thrombin and collagen with IC50 values of 0.64, 0.37, 0.35 and 0.87 mg/mL, respectively. Psm2 (1, 3, 10 mg/kg) administered to rats significantly inhibited platelet aggregation ex vivo induced by ADP. Psm2 (1, 3, 10 mg/mL, iv) administered to rats with the A-V shunt dose-dependently decreased the thrombus formation. Psm2 inhibited platelet adhesion to fibrinogen and collagen with IC50 values of 84.5 and 96.5 mg/mL, respectively, but did not affect the binding of fibrinogen to GPIIb/IIIa. Furthermore, Psm2 inhibited AktSer473 phosphorylation, but did not affect MAPK signaling and Src kinase activation. Molecular docking showed that Psm2 bound to phosphatidylinositol 3-kinase β (PI3Kβ) with a binding free energy of -13.265 kcal/mol. In addition, Psm2 did not cause toxicity in EA.hy926 cells and produced only slight bleeding in a mouse tail cutting model.

CONCLUSION

Psm2 inhibits platelet aggregation and thrombus formation by affecting PI3K/Akt signaling. Psm2 may be a lead compound or drug candidate that could be developed for the prevention or treatment of thrombotic diseases.

New approaches in tail-bleeding assay in mice: improving an important method for designing new anti-thrombotic agents

This report describes a modified, simple, low-cost and more sensitive method to determine bleeding patterns and haemoglobin concentration in a tail-bleeding assay using BALB/c mice and tail tip amputation. The cut tail was immersed in Drabkin's reagent to promote erythrocyte lysis and haemoglobin release, which was monitored over 30 min. The operator was blinded to individual conditions of the mice, which were treated with either saline (NaCl 0.15m), DMSO (0.5%) or clinical anti-thrombotic drugs. Our experimental protocols showed good reproducibility and repeatability of results when using Drabkin's reagent than water. Thus, the use of Drabkin's reagent offered a simple and low-cost method to observe and quantify the bleeding and rebleeding episodes. We also observed the bleeding pattern and total haemoglobin loss using untreated animals or those under anti-coagulant therapy in order to validate the new Drabkin method and thus confirm that it is a useful protocol to quantify haemoglobin concentrations in tail-bleeding assay. This modified method provided a more accurate results for bleeding patterns in mice and for identifying new anti-thrombotic drugs.

Anticoagulant activity of crude extract of Holotrichia diomphalia larvae

ETHNOPHARMACOLOGICAL RELEVANCE

Holotrichia diomphalia larvae are one classical folk medicinal material in East Asia which has clinically been used to promote blood circulation and dispel blood stasis for several hundred years.

AIM OF THE STUDY

The anticoagulant activity of crude extract of H. diomphalia larvae (CEHDL) in vitro and in vivo was evaluated to explore its mechanism as antithrombotic medicine.

MATERIALS AND METHODS

The effects of CEHDL on plasma recalcification time, platelet aggregation, bleeding time, hydrolysis of fibrinogen and fibrin were measured with normal human plasma, plasma-rich platelet, transected mouse tails and bovine fibrinogen; the anti-thrombosis activities of CEHDL in vitro and in vivo were analyzed with clots lysis assay and carrageenan-induced mouse tail thrombosis model.

RESULTS

CEHDL was found to contain large numbers of proteins and could inhibit blood coagulation and platelet aggregation in a dose-dependent manner. Furthermore, CEHDL preferentially cleaved α- and β-chains followed by γ-chains of fibrinogen. Besides, CEHDL could directly degrade fibrin rather than activate plasminogen. It has been noted that fibrinogenolytic activity of CEHDL could be unaffected by metal ions such as Mg(2+), Ca(2+), Zn(2+), Fe(2+), Fe(3+), Cu(2+) and buffers with pH 3-10. Moreover, protease inhibitors like TPSI, aprotinin, leupetin, PMSF, DTT and EDTA only slightly or not inhibited fibrinogenolytic activity of CEHDL. However, CEHDL could be completely inactivated at 75°C and 100°C. In addition, CEHDL exhibited anti-thrombosis activities in both blood clot lysis assay and carrageenan-induced thrombosis model.

CONCLUSION

CEHDL possessed potent anticoagulant activity and several fibrin(ogen)olytic agents from H. diomphalia larvae were responsible for its antithrombotic effect as medicine.

A potent anti-inflammatory peptide from the salivary glands of horsefly

Background

A diverse group of physiologically active peptides/proteins are present in the salivary glands of horsefly Tabanus yao (Diptera, Tabanidae) that facilitate acquisition of blood meal. However, their roles in the regulation of local inflammation remains poorly understood.

Methods

Induction expression profiles of immune-related molecules in the salivary glands of T. yao was analyzed by quantitative PCR (qPCR) after bacterial feeding. A significantly up-regulated molecule (cecropin-TY1) was selected for anti-inflammatory assay in lipopolysaccharide (LPS)-stimulated mouse peritoneal macrophages. The transcription levels of inducible NO synthase (iNOS) and pro-inflammatory cytokines were quantified by qPCR. Nitric oxide (NO) production was determined by Griess reagent. Pro-inflammatory cytokine production was determined by an enzyme-linked immunosorbent assay (ELISA). The inflammatory signals were assayed by Western blotting analysis. The secondary structure of cecropin-TY1 was measured by Circular dichroism (CD) spectroscopy. Interaction of cecropin-TY1 with LPS was evaluated by the dissociation of fluorescein isothiocyanate (FITC)-conjugated LPS aggregates and neutralization of LPS determined by a quantitative Chromogenic End-point Tachypleus amebocyte lysate (TAL) assay kit. Homology modeled structure analysis and mutation of key residues/structures were performed to understand its structure-activity relationship.

Results

Cecropin-TY1 was demonstrated to possess high anti-inflammatory activity and low cytotoxicity toward mouse macrophages. In LPS-stimulated mouse peritoneal macrophage, addition of cecropin-TY1 significantly inhibited the production of nitric oxide (NO) and pro-inflammatory cytokines. Further study revealed that cecropin-TY1 inhibited inflammatory cytokine production by blocking activation of mitogen-activated protein kinases (MAPKs) and transcriptional nuclear factor-κB (NF-κB) signals. Cecropin-TY1 even interacted with LPS and neutralized LPS. The secondary structure analysis revealed that cecropin-TY1 adopted unordered structures in hydrophobic environment but converted to α-helical confirmation in membrane mimetic environments. Homology modeled structure analysis demonstrated that cecropin-TY1 adopted two α-helices (Leu3-Thr24, Ile27-Leu38) linked by a hinge (Leu25-Pro26) and the structure surface was partly positively charged. Structure-activity relationship analysis indicated that several key residues/structures are crucial for its anti-inflammatory activity including α-helices, aromatic residue Trp2, positively charged residues Lys and Arg, hinge residue Pro26 and N-terminal amidation.

Conclusions

We found a novel anti-inflammatory function of horsefly-derived cecropin-TY1 peptide, laying groundwork for better understanding the ectoparasite-host interaction of horsefly with host and highlighting its potency in anti-inflammatory therapy for sepsis and endotoxin shock caused by Gram-negative bacterial infections.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-015-1149-y) contains supplementary material, which is available to authorized users.

An insight into the sialome of the horse fly, Tabanus bromius

Blood feeding animals face their host's defenses against tissue injury and blood loss while attempting to feed. One adaptation to surmount these barriers involves the evolution of a salivary potion that disarms their host's inflammatory and anti-hemostatic processes. The composition of the peptide moiety of this potion, or sialome (from the Greek sialo = saliva), can be deducted in part by proper interpretation of the blood feeder' sialotranscriptome. In this work we disclose the sialome of the blood feeding adult female Tabanus bromius. Following assembly of over 75 million Illumina reads (101 nt long) 16,683 contigs were obtained from which 4078 coding sequences were extracted. From these, 320 were assigned as coding for putative secreted proteins. These 320 contigs mapped 85% of the reads. The antigen-5 proteins family was studied in detail, indicating three Tabanus specific clades with and without disintegrin domains, as well as with and without leukotriene binding domains. Defensins were also detailed; a clade of salivary tabanid peptides was found lacking the propeptide domain ending in the KR dipeptide signaling furin cleavage. Novel protein families were also disclosed. Viral transcripts were identified closely matching the Kotonkan virus capsid proteins. Full length Mariner transposases were also identified. A total of 3043 coding sequences and their protein products were deposited in Genbank. Hyperlinked excel spreadsheets containing the coding sequences and their annotation are available at http://exon.niaid.nih.gov/transcriptome/T_bromius/Tbromius-web.xlsx (hyperlinked excel spreadsheet, 11 MB) and http://exon.niaid.nih.gov/transcriptome/T_bromius/Tbromius-SA.zip (Standalone excel with all local links, 360 MB). These sequences provide for a platform from which further proteomic studies may be designed to identify salivary proteins from T. bromius that are of pharmacological interest or used as immunological markers of host exposure.

An immunoregulatory peptide from tsetse fly salivary glands of Glossina morsitans morsitans

Tsetse fly Glossina morsitans morsitans is an important insect vector of African trypanosomes, which cause human African trypanosomiasis (HAT). As other hematophagous arthropods, tsetse fly relies heavily on the pharmacological propriety of their saliva to suppress host's immune reactions and get blood meal. However little information is available on immune regulators from testes fly. An immunoregulatory peptide named Gloss 2 containing amino acid sequence of QKNDTAFSCHFFEIYL SNCFNKEKYIKNYLQIM has been identified from salivary glands of the tsetse fly of G. morsitans morsitans (Diptera: Glossinidae). Gloss 2 has the ability to inhibit the secretion of tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ),interleukin-6 (IL-6) and interleukin-10 (IL-10) induced by lipopolysaccharide (LPS) in mouse splenocytes. Besides, Gloss 2 significantly suppressed the LPS-induced activation of MAPK signaling pathway through blocking phosphorylations of JNK, Erk and P38. Gloss 2 probably inhibits host inflammatory responses by inhibiting secretion of TNF-α, IFN-γ and IL-6. Considering IL-10's ability to promote humoral immune responses by enhancing class II expression B cells and inducing immunoglobulin (Ig) production, Gloss 2 may inhibit host humoral immune response by inhibiting IL-10 secretion. The immune-suppression may facilitate the blood feeding of tsetse fly and transmission of African trypanosomes to hosts.

RGD-modified liposomes enhance efficiency of aclacinomycin A delivery: evaluation of their effect in lung cancer

In this study, long-circulating Arg-Gly-Asp (RGD)-modified aclacinomycin A (ACM) liposomes were prepared by thin film hydration method. Their morphology, particle size, encapsulation efficiency, and in vitro release were investigated. The RGD-ACM liposomes was about 160 nm in size and had the visual appearance of a yellowish suspension. The zeta potential was -22.2 mV and the encapsulation efficiency was more than 93%. The drug-release behavior of the RGD-ACM liposomes showed a biphasic pattern, with an initial burst release and followed by sustained release at a constant rate. After being dissolved in phosphate-buffered saline (pH 7.4) and kept at 4°C for one month, the liposomes did not aggregate and still had the appearance of a milky white colloidal solution. In a pharmacokinetic study, rats treated with RGD-ACM liposomes showed slightly higher plasma concentrations than those treated with ACM liposomes. Maximum plasma concentrations of RGD-ACM liposomes and ACM liposomes were 4,532 and 3,425 ng/mL, respectively. RGD-ACM liposomes had a higher AUC0-∞ (1.54-fold), mean residence time (2.09-fold), and elimination half-life (1.2-fold) when compared with ACM liposomes. In an in vivo study in mice, both types of liposomes inhibited growth of human lung adenocarcinoma (A549) cells and markedly decreased tumor size when compared with the control group. There were no obvious pathological tissue changes in any of the treatment groups. Our results indicate that RGD-modified ACM liposomes have a better antitumor effect in vivo than their unmodified counterparts.

A tryptophan derivative TD-26 attenuates thrombus formation by inhibiting both PI3K/Akt signaling and binding of fibrinogen to integrin αIIbβ3

The incidence and mortality of thrombotic disorders are rapidly increasing worldwide. The existing antithrombotic drugs, however, are associated with side effects, especially bleeding complications. Therefore, there remains a need for the development of more effective and safer antithrombotic agents. In this study, we discovered a new synthetic tryptophan derivative TD-26, producing potent inhibitory effect on platelet aggregation while without causing obvious bleeding risk. It has been shown that TD-26 inhibited platelet aggregation induced by ADP, thrombin, U46619 and collagen in vitro and suppressed the platelet aggregation induced by ADP ex vivo. Mechanism studies indicated that TD-26 inhibited platelet adhesion to fibrinogen-coated surfaces, blocked the binding of fibrinogen to integrin αIIbβ3 and reduced Akt(Ser473) phosphorylation in platelet phosphatidylinositol 3-kinase (PI3K) signaling. Furthermore, TD-26 exhibited potent antithrombotic activity in vivo. In animal models, it decreased death of mice with acute pulmonary thrombosis by 90% and attenuated thrombosis weight by 60.3%, both at a dose of 3 mg/kg. Additionally, TD-26 did not obviously prolong bleeding time in mice. Taken together, our results reveal that TD-26 is a novel antithrombotic compound exhibiting both integrin αIIbβ3 inhibition and PI3K signaling blockage, with a low bleeding risk.

Isolation and characterization of four medium-size disintegrins from the venoms of Central American viperid snakes of the genera Atropoides, Bothrops, Cerrophidion and Crotalus

Four disintegrins were isolated from the venoms of the Central American viperid snakes Atropoides mexicanus (atropoimin), Bothrops asper (bothrasperin), Cerrophidion sasai (sasaimin), and Crotalus simus (simusmin). Purifications were performed by reverse-phase HPLC. The four disintegrins have biochemical characteristics, i.e. molecular mass and location of Cys, which allow their classification within the group of medium-size disintegrins. All of them present the canonical RGD sequence, which determines their interaction with integrins in cell membranes. The disintegrins inhibited ADP and collagen-induced human platelet aggregation, with similar IC50s in the nM range. In addition, disintegrins inhibited the adhesion of an endothelial cell line and a melanoma cell line to the extracellular matrix proteins type I collagen, laminin, fibronectin, and vitronectin, albeit showing variable ability to exert this activity. This study expands the inventory of this family of viperid venom proteins, and reports, for the first time, disintegrins from the venoms of species of the genera Atropoides and Cerrophidion.

rAdinbitor, a disintegrin from Agkistrodon halys brevicaudus stejneger, inhibits tumorigenicity of hepatocarcinoma via enhanced anti-angiogenesis and immunocompetence

Adinbitor is a disintegrin previously obtained from Agkistrodon halys brevicaudus stejneger by our group. Here, we investigated the in vitro and in vivo anti-tumor activities of recombinant Adinbitor (rAdinbitor). rAdinbitor stimulation can inhibit the in vitro proliferation, migration and invasion capacities of murine hepatocarcinoma H22 and Hca-F cells. The administrations of rAdinbitor either by gavage or intraperitoneal injection suppress the tumor malignancy and prolong the survival rate and time of H22-transplanted mice. The number and size of formed blood vessels decreased dramatically in tumorous tissues in that the expression levels of vascular endothelial growth factor (VEGF) and cluster of differentiation 34 (CD34) were significantly decreased in responding to rAdinbitor treatment. The protein levels of IL-18 and IgG increased significantly in the serum of H22-transplanted tumor mice with rAdinbitor treatment. rAdinbitor shows in vitro and in vivo anti-tumor effects as an angiogenesis inhibitor and immunocompetence enhancer.

The structure of hookworm platelet inhibitor (HPI), a CAP superfamily member from Ancylostoma caninum

Secreted protein components of hookworm species include a number of representatives of the cysteine-rich/antigen 5/pathogenesis-related 1 (CAP) protein family known as Ancylostoma-secreted proteins (ASPs). Some of these have been considered as candidate antigens for the development of vaccines against hookworms. The functions of most CAP superfamily members are poorly understood, but one form, the hookworm platelet inhibitor (HPI), has been isolated as a putative antagonist of the platelet integrins αIIbβ3 and α2β1. Here, the crystal structure of HPI is described and its structural features are examined in relation to its possible function. The HPI structure is similar to those of other ASPs and shows incomplete conservation of the sequence motifs CAP1 and CAP2 that are considered to be diagnostic of CAP superfamily members. The asymmetric unit of the HPI crystal contains a dimer with an extensive interaction interface, but chromatographic measurements indicate that it is primarily monomeric in solution. In the dimeric structure, the putative active-site cleft areas from both monomers are united into a single negatively charged depression. A potential Lys-Gly-Asp disintegrin-like motif was identified in the sequence of HPI, but is not positioned at the apex of a tight turn, making it unlikely that it interacts with the integrin. Recombinant HPI produced in Escherichia coli was found not to inhibit the adhesion of human platelets to collagen or fibrinogen, despite having a native structure as shown by X-ray diffraction. This result corroborates previous analyses of recombinant HPI and suggests that it might require post-translational modification or have a different biological function.

Salivary antigen-5/CAP family members are Cu2+-dependent antioxidant enzymes that scavenge O₂₋. and inhibit collagen-induced platelet aggregation and neutrophil oxidative burst

The function of the antigen-5/CAP family of proteins found in the salivary gland of bloodsucking animals has remained elusive for decades. Antigen-5 members from the hematophagous insects Dipetalogaster maxima (DMAV) and Triatoma infestans (TIAV) were expressed and discovered to attenuate platelet aggregation, ATP secretion, and thromboxane A2 generation by low doses of collagen (<1 μg/ml) but no other agonists. DMAV did not interact with collagen, glycoprotein VI, or integrin α2β1. This inhibitory profile resembles the effects of antioxidants Cu,Zn-superoxide dismutase (Cu,Zn-SOD) in platelet function. Accordingly, DMAV was found to inhibit cytochrome c reduction by O2[Symbol: see text] generated by the xanthine/xanthine oxidase, implying that it exhibits antioxidant activity. Moreover, our results demonstrate that DMAV blunts the luminescence signal of O2[Symbol: see text] generated by phorbol 12-myristate 13-acetate-stimulated neutrophils. Mechanistically, inductively coupled plasma mass spectrometry and fluorescence spectroscopy revealed that DMAV, like Cu,Zn-SOD, interacts with Cu(2+), which provides redox potential for catalytic removal of O2[Symbol: see text]. Notably, surface plasmon resonance experiments (BIAcore) determined that DMAV binds sulfated glycosaminoglycans (e.g. heparin, KD ~100 nmol/liter), as reported for extracellular SOD. Finally, fractions of the salivary gland of D. maxima with native DMAV contain Cu(2+) and display metal-dependent antioxidant properties. Antigen-5/CAP emerges as novel family of Cu(2+)-dependent antioxidant enzymes that inhibit neutrophil oxidative burst and negatively modulate platelet aggregation by a unique salivary mechanism.

Structure of Ostertagia ostertagi ASP-1: insights into disulfide-mediated cyclization and dimerization

The cysteine-rich secretory/antigen 5/pathogenesis-related 1 (CAP) protein superfamily is composed of a functionally diverse group of members that are found in both eukaryotes and prokaryotes. The excretome/secretome of numerous helminths (parasitic nematodes) contains abundant amounts of CAP members termed activation-associated secreted proteins (ASPs). Although ASPs are necessary for the parasitic life cycle in the host, the current lack of structural and functional information limits both understanding of their actual role in host-parasite interactions and the development of new routes in controlling parasitic infections and diseases. Alleviating this knowledge gap, a 1.85 Å resolution structure of recombinantly produced Oo-ASP-1 from Ostertagia ostertagi, which is one of the most prevalent gastrointestinal parasites in cattle worldwide, was solved. Overall, Oo-ASP-1 displays the common hallmark architecture shared by all CAP-superfamily members, including the N-terminal CAP and C-terminal cysteine-rich domains, but it also reveals a number of highly peculiar features. In agreement with studies of the natively produced protein, the crystal structure shows that Oo-ASP-1 forms a stable dimer that has been found to be primarily maintained via an intermolecular disulfide bridge, hence the small interaction surface of only 306.8 Å(2). Moreover, unlike any other ASP described to date, an additional intramolecular disulfide bridge links the N- and C-termini of each monomer, thereby yielding a quasi-cyclic molecule. Taken together, the insights presented here form an initial step towards a better understanding of the actual biological role(s) that this ASP plays in host-parasite interactions. The structure is also essential to help to define the key regions of the protein suitable for development of ASP-based vaccines, which would enable the current issues surrounding anthelmintic resistance in the treatment of parasitic infections and diseases to be circumvented.

The "Vampirome": Transcriptome and proteome analysis of the principal and accessory submaxillary glands of the vampire bat Desmodus rotundus, a vector of human rabies

Vampire bats are notorious for being the sole mammals that strictly feed on fresh blood for their survival. While their saliva has been historically associated with anticoagulants, only one antihemostatic (plasminogen activator) has been molecularly and functionally characterized. Here, RNAs from both principal and accessory submaxillary (submandibular) salivary glands of Desmodus rotundus were extracted, and ~200 million reads were sequenced by Illumina. The principal gland was enriched with plasminogen activators with fibrinolytic properties, members of lipocalin and secretoglobin families, which bind prohemostatic prostaglandins, and endonucleases, which cleave neutrophil-derived procoagulant NETs. Anticoagulant (tissue factor pathway inhibitor, TFPI), vasodilators (PACAP and C-natriuretic peptide), and metalloproteases (ADAMTS-1) were also abundantly expressed. Members of the TSG-6 (anti-inflammatory), antigen 5/CRISP, and CCL28-like (antimicrobial) protein families were also sequenced. Apyrases (which remove platelet agonist ADP), phosphatases (which degrade procoagulant polyphosphates), and sphingomyelinase were found at lower transcriptional levels. Accessory glands were enriched with antimicrobials (lysozyme, defensin, lactotransferrin) and protease inhibitors (TIL-domain, cystatin, Kazal). Mucins, heme-oxygenase, and IgG chains were present in both glands. Proteome analysis by nano LC-MS/MS confirmed that several transcripts are expressed in the glands. The database presented herein is accessible online at http://exon.niaid.nih.gov/transcriptome/D_rotundus/Supplemental-web.xlsx. These results reveal that bat saliva emerges as a novel source of modulators of vascular biology.

BIOLOGICAL SIGNIFICANCE

Vampire bat saliva emerges as a novel source of antihemostatics which modulate several aspects of vascular biology.

Purification and characterization of a novel antithrombotic peptide from Scolopendra subspinipes mutilans

ETHNOPHARMACOLOGICAL RELEVANCE

The centipede has been prescribed for the treatment of cardiovascular diseases in Korea, China and other Far Eastern Asian countries for several hundred years.

MATERIALS AND METHODS

A novel antithrombotic peptide was isolated from Scolopendra subspinipes mutilans using a combination of ultrafiltration, Sephadex G-50 column, Source 15Q anion exchange column and RP-HPLC C18 column.

RESULTS

The molecular mass of the purified peptide is 346Da measured by Electrospray Ionization Mass Spectrometry (ESI-MS). The primary structure of the peptide is Ser-Gln-Leu (SQL) determined by Edman degradation. SQL potently prolonged the activated partial thromboplastin time (aPTT), and inhibited platelet aggregation.

CONCLUSIONS

These results help to clarify the mechanism of the antithrombotic activity of the centipede for effective treatment of cardiovascular and cerebrovascular diseases.

Disintegrins from hematophagous sources

Bloodsucking arthropods are a rich source of salivary molecules (sialogenins) which inhibit platelet aggregation, neutrophil function and angiogenesis. Here we review the literature on salivary disintegrins and their targets. Disintegrins were first discovered in snake venoms, and were instrumental in our understanding of integrin function and also for the development of anti-thrombotic drugs. In hematophagous animals, most disintegrins described so far have been discovered in the salivary gland of ticks and leeches. A limited number have also been found in hookworms and horseflies, and none identified in mosquitoes or sand flies. The vast majority of salivary disintegrins reported display a RGD motif and were described as platelet aggregation inhibitors, and few others as negative modulator of neutrophil or endothelial cell functions. This notably low number of reported disintegrins is certainly an underestimation of the actual complexity of this family of proteins in hematophagous secretions. Therefore an algorithm was created in order to identify the tripeptide motifs RGD, KGD, VGD, MLD, KTS, RTS, WGD, or RED (flanked by cysteines) in sialogenins deposited in GenBank database. The search included sequences from various blood-sucking animals such as ticks (e.g., Ixodes sp., Argas sp., Rhipicephalus sp., Amblyommasp.), tabanids (e.g., Tabanus sp.), bugs (e.g., Triatoma sp., Rhodnius prolixus), mosquitoes (e.g., Anopheles sp., Aedes sp., Culex sp.), sand flies (e.g., Lutzomyia sp., Phlebotomus sp.), leeches (e.g., Macrobdella sp., Placobdella sp.) and worms (e.g., Ancylostoma sp.). This approach allowed the identification of a remarkably high number of novel putative sialogenins with tripeptide motifs typical of disintegrins (>450 sequences) whose biological activity remains to be verified. This database is accessible online as a hyperlinked worksheet and displays biochemical, taxonomic, and gene ontology aspects for each putative disintegrin. It is also freely available for download (right click with the mouse) at links http://exon.niaid.nih.gov/transcriptome/RGD/RGD-Peps-WEB.xlsx (web version) and http://exon.niaid.nih.gov/transcriptome/RGD/RGD-sialogenins.zip (stand alone version).

Structure of protein having inhibitory disintegrin and leukotriene scavenging functions contained in single domain

The antihemostatic/antiangiogenic protein tablysin-15 is a member of the CAP (cysteine-rich secretory, antigen 5, and pathogenesis-related 1 protein) superfamily and has been shown to bind the integrins α(IIb)β(3) and α(V)β(3) by means of an Arg-Gly-Asp (RGD) tripeptide sequence. Here we describe the x-ray crystal structure of tablysin-15 and show that the RGD motif is located in a novel structural context. The motif itself is contained in a type II β-turn structure that is similar in its conformation to the RGD sequence of the cyclic pentapeptide cilengitide when bound to integrin α(V)β(3). The CAP domain also contains a hydrophobic channel that appears to bind a fatty acid molecule in the crystal structure after purification from Escherichia coli. After delipidation of the protein, tablysin-15 was found to bind proinflammatory cysteinyl leukotrienes with submicromolar affinities. The structure of the leukotriene E(4)-tablysin-15 complex shows that the ligand binds with the nonfunctionalized end of the fatty acid chain buried in the hydrophobic pocket, whereas the carboxylate end of the ligand binds forms hydrogen bond/salt bridge interactions with polar side chains at the channel entrance. Therefore, tablysin-15 functions as an inhibitor of integrin function and as an anti-inflammatory scavenger of eicosanoids.

A deep insight into the sialotranscriptome of the gulf coast tick, Amblyomma maculatum

Background

Saliva of blood sucking arthropods contains compounds that antagonize their hosts' hemostasis, which include platelet aggregation, vasoconstriction and blood clotting; saliva of these organisms also has anti-inflammatory and immunomodullatory properties. Perhaps because hosts mount an active immune response against these compounds, the diversity of these compounds is large even among related blood sucking species. Because of these properties, saliva helps blood feeding as well as help the establishment of pathogens that can be transmitted during blood feeding.

Methodology/Principal Findings

We have obtained 1,626,969 reads by pyrosequencing a salivary gland cDNA library from adult females Amblyomma maculatum ticks at different times of feeding. Assembly of this data produced 72,441 sequences larger than 149 nucleotides from which 15,914 coding sequences were extracted. Of these, 5,353 had >75% coverage to their best match in the non-redundant database from the National Center for Biotechnology information, allowing for the deposition of 4,850 sequences to GenBank. The annotated data sets are available as hyperlinked spreadsheets. Putative secreted proteins were classified in 133 families, most of which have no known function.

Conclusions/Significance

This data set of proteins constitutes a mining platform for novel pharmacologically active proteins and for uncovering vaccine targets against A. maculatum and the diseases they carry.