2-DE-based proteomic investigation of the saliva of the Amazonian triatomine vectors of Chagas disease: Rhodnius brethesi and Rhodnius robustus

Comparative proteomic analysis of the hemolymph and salivary glands of Rhodnius prolixus and R. colombiensis reveals candidates associated with differential lytic activity against Trypanosoma cruzi Dm28c and T. cruzi Y

BACKGROUND

Immune response of triatomines plays an important role in the success or failure of transmission of T. cruzi. Studies on parasite-vector interaction have shown the presence of trypanolytic factors and have been observed to be differentially expressed among triatomines, which affects the transmission of some T. cruzi strains or DTUs (Discrete Typing Units).

METHODOLOGY/PRINCIPAL FINDINGS

Trypanolytic factors were detected in the hemolymph and saliva of R. prolixus against epimastigotes and trypomastigotes of the Y strain (T. cruzi II). To identify the components of the immune response that could be involved in this lytic activity, a comparative proteomic analysis was carried out, detecting 120 proteins in the hemolymph of R. prolixus and 107 in R. colombiensis. In salivary glands, 1103 proteins were detected in R. prolixus and 853 in R. colombiensis. A higher relative abundance of lysozyme, prolixin, nitrophorins, and serpin as immune response proteins was detected in the hemolymph of R. prolixus. Among the R. prolixus salivary proteins, a higher relative abundance of nitrophorins, lipocalins, and triabins was detected. The higher relative abundance of these immune factors in R. prolixus supports their participation in the lytic activity on Y strain (T. cruzi II), but not on Dm28c (T. cruzi I), which is resistant to lysis by hemolymph and salivary proteins of R. prolixus due to mechanisms of evading oxidative stress caused by immune factors.

CONCLUSIONS/SIGNIFICANCE

The lysis resistance observed in the Dm28c strain would be occurring at the DTU I level. T. cruzi I is the DTU with the greatest geographic distribution, from the south of the United States to central Chile and Argentina, a distribution that could be related to resistance to oxidative stress from vectors. Likewise, we can say that lysis against strain Y could occur at the level of DTU II and could be a determinant of the vector inability of these species to transmit T. cruzi II. Future proteomic and transcriptomic studies on vectors and the interactions of the intestinal microbiota with parasites will help to confirm the determinants of successful or failed vector transmission of T. cruzi DTUs in different parts of the Western Hemisphere.

Angiotensin-(1-7) Central Mechanisms After ICV Infusion in Hypertensive Transgenic (mRen2)27 Rats

Previous data showed hypertensive rats subjected to chronic intracerebroventricular (ICV) infusion of angiotensin-(1-7) presented attenuation of arterial hypertension, improvement of baroreflex sensitivity, restoration of cardiac autonomic balance and a shift of cardiac renin-angiotensin system (RAS) balance toward Ang-(1-7)/Mas receptor. In the present study, we investigated putative central mechanisms related to the antihypertensive effect induced by ICV Ang-(1-7), including inflammatory mediators and the expression/activity of the RAS components in hypertensive rats. Furthermore, we performed a proteomic analysis to evaluate differentially regulated proteins in the hypothalamus of these animals. For this, Sprague Dawley (SD) and transgenic (mRen2)27 hypertensive rats (TG) were subjected to 14 days of ICV infusion with Ang-(1-7) (200 ng/h) or 0.9% sterile saline (0.5 μl/h) through osmotic mini-pumps. We observed that Ang-(1-7) treatment modulated inflammatory cytokines by decreasing TNF-α levels while increasing the anti-inflammatory IL-10. Moreover, we showed a reduction in ACE activity and gene expression of AT1 receptor and iNOS. Finally, our proteomic evaluation suggested an anti-inflammatory mechanism of Ang-(1-7) toward the ROS modulators Uchl1 and Prdx1.

Salivary proteins electrophoretic patterns enabled differentiating Colombian Rhodnius Trans-Andean and Cis-Andean groups

Introduction: Rhodnius (Hemiptera: Reduviidae: Triatominae) species are made up of haematophagous insect vectors for Trypanosoma cruzi (Chagas’ disease aetiological agent) and T. rangeli, an infective parasite that is not pathogenic for vertebrate hosts. The study of their salivary protein diversity enables the obtention of characteristic one-dimensional electrophoretic profiles of some triatomine species; however, few reports have dealt with Rhodnius species salivary proteins electrophoretic patterns. Objective: To compare R. colombiensis, R. pallescens, R. pictipes, R. prolixus, and R. robustus’ salivary proteins one-dimensional electrophoretic profiles. Materials and methods: SDS-PAGE was used for obtaining electrophoretic profiles of saliva from the species under study. The unweighted pair group method with arithmetic mean (UPGMA) was used for constructing a phenogram. Results: Electrophoretic profiles of soluble saliva had protein bands ranging from 15 to 45 kDa, thereby enabling the five species studied to be differentiated. The phenogram revealed two main groups, one formed by the Pictipes and Prolixus cis-Andean groups and another consisting of the Pallescens trans-Andean group. Conclusion: Differences were revealed regarding R. colombiensis, R. pallescens, R. pictipes, R. prolixus, and R. robustus electrophoretic profiles of salivary proteins; their variability facilitated constructing a phenogram which was taxonomically congruent with the groups from the genus Rhodnius.

The Pharmacopea within Triatomine Salivary Glands

Triatomines are blood-feeding insects that prey on vertebrate hosts. Their saliva is largely responsible for their feeding success. The triatomine salivary content has been studied over the past decades, revealing multifunctional bioactive proteins targeting the host´s hemostasis and immune system. Recently, sequencing of salivary-gland mRNA libraries revealed increasingly complex and complete transcript databases that have been used to validate the expression of deduced proteins through proteomics. This review provides an insight into the journey of discovery and characterization of novel molecules in triatomine saliva.

Insight Into the Salivary Secretome of Varroa destructor and Salivary Toxicity to Apis cerana

The Varroa destructor (Acari Varroidae) mite is a serious threat to honey bee due to hemolymph feeding and virus transmission. Mite salivary proteins are involved in these interactions. However, the salivary secretome has not been previously characterized. In this paper, the saliva of V. destructor was found to be toxic to the worker larvae of Apis cerana (Hymenoptera Apidae) in the absence of deformed wing virus (DWV) and to stimulate the development of deformed wings in Apis mellifera (Hymenoptera Apidae) adults in the presence of DWV. The salivary secretome was analyzed by nano-liquid chromatography coupled to tandem mass spectrometry (nano-LC-MS/MS). A search of the resulting data against peptide databases using the software Mascot yielded 356, 53, and 9 matched proteins from V. destructor, A. mellifera, and DWV, respectively. The saliva contained Varroa mite proteins identified as important for potential virulence to A. cerana larvae, for the inhibition of harmful microorganisms, for the utilization of bee nutrients, and for antioxidant, oxidation-reduction and detoxification functions as well as A. mellifera proteins identified as nutrients important for mite reproduction. The saliva proteins also contained viral proteins from one virus, DWV. These results provide a strong foundation for understanding the interactions among the Varroa mite, honeybee, and DWV.

Giant fish-killing water bug reveals ancient and dynamic venom evolution in Heteroptera

True Bugs (Insecta: Heteroptera) produce venom or saliva with diverse bioactivities depending on their feeding strategies. However, little is known about the molecular evolution of the venom toxins underlying these biological activities. We examined venom of the giant fish-killing water bug Lethocerus distinctifemur (Insecta: Belostomatidae) using infrared spectroscopy, transcriptomics, and proteomics. We report 132 venom proteins including putative enzymes, cytolytic toxins, and antimicrobial peptides. Over 73% (96 proteins) showed homology to venom proteins from assassin bugs (Reduviidae), including 21% (28 proteins from seven families) not known from other sources. These data suggest that numerous protein families were recruited into venom and diversified rapidly following the switch from phytophagy to predation by ancestral heteropterans, and then were retained over > 200 my of evolution. In contrast, trophic switches to blood-feeding (e.g. in Triatominae and Cimicidae) or reversions to plant-feeding (e.g., in Pentatomomorpha) were accompanied by rapid changes in the composition of venom/saliva, including the loss of many protein families.

Proteomic analysis of the kissing bug Rhodnius prolixus antenna

Reception of odorants is essential in insects' life since the chemical signals in the environment (=semiochemicals) convey information about availability of hosts for a blood meal, mates for reproduction, sites for oviposition and other relevant information for fitness in the environment. Once they reach the antennae, these semiochemicals bind to odorant-binding proteins and are transported through the sensillar lymph until reach the odorant receptors. Such perireceptor events, particularly the interactions with transport proteins, are the liaison between the external environment and the entire neuroethological system and, therefore, a potential target to disrupt insect chemical communication. In this study, a proteomic profile of female and male antennae of Rhodnius prolixus, a vector of Chagas disease, was obtained in an attempt to unravel the entire repertoire of olfactory proteins involved in perireceptor events. Using shotgun proteomics and two-dimensional gel electrophoresis approaches followed by nano liquid chromatography coupled with tandem LTQ Velos Orbitrap mass spectrometry, we have identified 581 unique proteins. Putative olfactory proteins, including 17 odorant binding proteins, 6 chemosensory proteins, 2 odorant receptors, 3 transient receptor channels and 1 gustatory receptor were identified. Proteins involved in general cellular functions such as generation of precursor metabolites, energy generation and catabolism were expressed at high levels. Additionally, proteins that take part in signal transduction, ion binding, and stress response, kinase and oxidoreductase activity were frequent in antennae from both sexes. This proteome strategy unraveled for the first time the complex nature of perireceptor and other olfactory events that occur in R. prolixus antennae, including evidence for phosphorylation of odorant-binding and chemosensory proteins. These findings not only increase our understanding of the olfactory process in triatomine species, but also identify potential molecular targets to be explored for population control of such insect vectors.

Proteomic and transcriptomic analysis of saliva components from the hematophagous reduviid Triatoma pallidipennis

Species belonging to the Triatominae subfamily are commonly associated with Chagas disease, as they are potential vectors of the parasite Trypanosoma cruzi. However, their saliva contains a cocktail of diverse anti-hemostatic proteins that prevent blood coagulation, vasodilation and platelet aggregation of blood; components with indisputable therapeutic potential. We performed a transcriptomic and proteomic analyses of salivary glands and protein spots from 2DE gels of milked saliva, respectively, from the Mexican Triatoma pallidipennis. Massive sequencing techniques were used to reveal this protein diversity. A total of 78 out of 233 transcripts were identified as proteins in the saliva, divided among 43 of 55 spots from 2DE gels of saliva, identified by LC-MS/MS analysis. Some of the annotated transcripts putatively code for anti-hemostatic proteins, which share sequence similarities with proteins previously described for South American triatomines. The most abundant as well as diverse transcripts and proteins in the saliva were the anti-hemostatic triabins. For the first time, a transcriptomic analysis uncovered other unrelated but relevant components in triatomines, including antimicrobial and thrombolytic polypeptides. Likewise, unique proteins such as the angiotensin-converting enzyme were identified not just in the salivary gland transcriptome but also at saliva proteome of this North American bloodsucking insect.

BIOLOGICAL SIGNIFICANCE

This manuscript is the first report of the correlation between proteome and transcriptome of Triatoma pallidipennis, which shows for the first time the presence of proteins in this insect that have not been characterized in other species of this family. This information contributes to a better understanding of the multiple host defense mechanisms that are being affected at the moment of blood ingestion by the insect. Furthermore, this report gives a repertoire of possible therapeutic proteins.

A Deep Insight into the Sialome of Rhodnius neglectus, a Vector of Chagas Disease

BACKGROUND

Triatomines are hematophagous insects that act as vectors of Chagas disease. Rhodnius neglectus is one of these kissing bugs found, contributing to the transmission of this American trypanosomiasis. The saliva of hematophagous arthropods contains bioactive molecules responsible for counteracting host haemostatic, inflammatory, and immune responses.

METHODS/PRINCIPAL FINDINGS

Next generation sequencing and mass spectrometry-based protein identification were performed to investigate the content of triatomine R. neglectus saliva. We deposited 4,230 coding DNA sequences (CDS) in GenBank. A set of 636 CDS of proteins of putative secretory nature was extracted from the assembled reads, 73 of them confirmed by proteomic analysis. The sialome of R. neglectus was characterized and serine protease transcripts detected. The presence of ubiquitous protein families was revealed, including lipocalins, serine protease inhibitors, and antigen-5. Metalloproteases, disintegrins, and odorant binding protein families were less abundant.

CONCLUSIONS/SIGNIFICANCE

The data presented improve our understanding of hematophagous arthropod sialomes, and aid in understanding hematophagy and the complex interplay among vectors and their vertebrate hosts.

Venoms of Heteropteran Insects: A Treasure Trove of Diverse Pharmacological Toolkits

The piercing-sucking mouthparts of the true bugs (Insecta: Hemiptera: Heteroptera) have allowed diversification from a plant-feeding ancestor into a wide range of trophic strategies that include predation and blood-feeding. Crucial to the success of each of these strategies is the injection of venom. Here we review the current state of knowledge with regard to heteropteran venoms. Predaceous species produce venoms that induce rapid paralysis and liquefaction. These venoms are powerfully insecticidal, and may cause paralysis or death when injected into vertebrates. Disulfide-rich peptides, bioactive phospholipids, small molecules such as N,N-dimethylaniline and 1,2,5-trithiepane, and toxic enzymes such as phospholipase A2, have been reported in predatory venoms. However, the detailed composition and molecular targets of predatory venoms are largely unknown. In contrast, recent research into blood-feeding heteropterans has revealed the structure and function of many protein and non-protein components that facilitate acquisition of blood meals. Blood-feeding venoms lack paralytic or liquefying activity but instead are cocktails of pharmacological modulators that disable the host haemostatic systems simultaneously at multiple points. The multiple ways venom is used by heteropterans suggests that further study will reveal heteropteran venom components with a wide range of bioactivities that may be recruited for use as bioinsecticides, human therapeutics, and pharmacological tools.

Screening on human hepatoma cell line HepG-2 nucleus and cytoplasm protein after CDK2 silencing by RNAi

The activation of phase-specific cyclin-dependent kinases is associated with ordered cell cycle transitions. Among the mammalian Cdks, Cdk2 is essential for liver cancer cell proliferation. The related cycling protein CDK2 was analyzed by 2D-gel and MALDI-TOF/TOF MS mass assay in liver cancer cells, which CDK2 was silenced. The results showed four significantly different spots in cell ribonucleoprotein (similar to ribosomal protein S12, chaperonin 10-related protein, beta-actin and zinc finger protein 276) and four in plasmosin (aldolase A protein, hCG, anonymous protein and tubulin, gamma complex associated protein 2). In the plasmosin, aldolase A catalyzes the production of tublin and actin. Together they regulate the cell cycle and arrest the cell in the S phage. In the cell ribonucleoprotein, proteins with homology to ribosomal protein S12 and chaperonin 10 play a similar role in cell cycle regulation.

Identifying salivary antigens of Phlebotomus argentipes by a 2DE approach

In the Indian subcontinent visceral leishmaniasis, also known as kala-azar, is caused by the protozoa Leishmania donovani and is transmitted to humans by the bite of infected female sand flies Phlebotomus argentipes in an anthroponotic cycle. Sand fly saliva is known to play an important role in host infection outcome after an infective bite. Immunogenicity of P. argentipes saliva has already been described. However, specific antigens that can contribute to these immunogenic properties are unknown. This work focuses on the identification of antigens present in P. argentipes saliva through the combination of two-dimensional electrophoresis (2DE) and Western blot (WB). Analysis of the salivary protein profile showed a gradual increase of the protein content in relation to the age of sand flies, reaching the complete salivary protein pattern at day five, which marked the minimum age for dissections. The 2DE revealed a reproducible protein profile that matched the classic monodimensional SDS-PAGE pattern (1DE). The resulting salivary proteomic map consisted of at least 30 spots located between 10 and 60 kDa. According to their isoelectric points, spots were mostly distributed around pH ranges: 5-6 and 9-10. In the proteomic maps, the presence of isoforms or posttranslational modifications was also highlighted since several spots were identified as the same protein. Analysis by in silico prediction programs located several potential glycosylation and phosphorylation sites in the aminoacidic sequences. On the other hand, pooled sera of immunized hamsters through the bite of uninfected sand flies showed elevated anti-saliva IgG levels. These sera permitted the detection of 4 protein bands and at least 20 protein spots in 1DE and 2DE respectively, followed by WB. The antigens were identified by MALDI-TOF, MALDI-TOF/TOF and de novo sequencing as D7-related proteins, PpSP15-like proteins, antigen 5-related proteins, apyrases, and several proteins without assigned protein family. Absence of cross-reactivity between P. argentipes and Phlebotomus perniciosus saliva antibodies determined by ELISA and WB was highlighted in this study, confirming that specific salivary antigens from different sand fly vectors need to be sought when designing vector-borne vaccines and markers for vector exposure assays.