Proteomic analysis provides insights on venom processing in Conus textile

Proteomic analysis of the venom of Conus flavidus from Red Sea reveals potential pharmacological applications

BACKGROUND

Venomous marine cone snails produce unique neurotoxins called conopeptides or conotoxins, which are valuable for research and drug discovery. Characterizing Conus venom is important, especially for poorly studied species, as these tiny and steady molecules have considerable potential as research tools for detecting new pharmacological applications. In this study, a worm-hunting cone snail, Conus flavidus inhabiting the Red Sea coast were collected, dissected and the venom gland extraction was subjected to proteomic analysis to define the venom composition, and confirm the functional structure of conopeptides.

RESULTS

Analysis of C. flavidus venom identified 117 peptide fragments and assorted them to conotoxin precursors and non-conotoxin proteins. In this procedure, 65 conotoxin precursors were classified and identified to 16 conotoxin precursors and hormone superfamilies. In the venom of C. flavidus, the four conotoxin superfamilies T, A, O2, and M were the most abundant peptides, accounting for 75.8% of the total conotoxin diversity. Additionally, 19 non-conotoxin proteins were specified in the venom, as well as several potentially biologically active peptides with putative applications.

CONCLUSION

Our research displayed that the structure of the C. flavidus-derived proteome is similar to other Conus species and includes toxins, ionic channel inhibitors, insulin-like peptides, and hyaluronidase. This study provides a foundation for discovering new conopeptides from C. flavidus venom for pharmaceutical use.

Coordinated adaptations define the ontogenetic shift from worm- to fish-hunting in a venomous cone snail

Marine cone snails have attracted researchers from all disciplines but early life stages have received limited attention due to difficulties accessing or rearing juvenile specimens. Here, we document the culture of Conus magus from eggs through metamorphosis to reveal dramatic shifts in predatory feeding behaviour between post-metamorphic juveniles and adult specimens. Adult C. magus capture fish using a set of paralytic venom peptides combined with a hooked radular tooth used to tether envenomed fish. In contrast, early juveniles feed exclusively on polychaete worms using a unique "sting-and-stalk" foraging behaviour facilitated by short, unbarbed radular teeth and a distinct venom repertoire that induces hypoactivity in prey. Our results demonstrate how coordinated morphological, behavioural and molecular changes facilitate the shift from worm- to fish-hunting in C. magus, and showcase juvenile cone snails as a rich and unexplored source of novel venom peptides for ecological, evolutionary and biodiscovery studies.

Venom biotechnology: casting light on nature's deadliest weapons using synthetic biology

Venoms are complex chemical arsenals that have evolved independently many times in the animal kingdom. Venoms have attracted the interest of researchers because they are an important innovation that has contributed greatly to the evolutionary success of many animals, and their medical relevance offers significant potential for drug discovery. During the last decade, venom research has been revolutionized by the application of systems biology, giving rise to a novel field known as venomics. More recently, biotechnology has also made an increasing impact in this field. Its methods provide the means to disentangle and study venom systems across all levels of biological organization and, given their tremendous impact on the life sciences, these pivotal tools greatly facilitate the coherent understanding of venom system organization, development, biochemistry, and therapeutic activity. Even so, we lack a comprehensive overview of major advances achieved by applying biotechnology to venom systems. This review therefore considers the methods, insights, and potential future developments of biotechnological applications in the field of venom research. We follow the levels of biological organization and structure, starting with the methods used to study the genomic blueprint and genetic machinery of venoms, followed gene products and their functional phenotypes. We argue that biotechnology can answer some of the most urgent questions in venom research, particularly when multiple approaches are combined together, and with other venomics technologies.

Principal Component and Structural Element Analysis Provide Insights into the Evolutionary Divergence of Conotoxins

Predatory cone snails (Conus) developed a sophisticated neuropharmacological mechanism to capture prey, escape against other predators, and deter competitors. Their venom's remarkable specificity for various ion channels and receptors is an evolutionary feat attributable to the venom's variety of peptide components (conotoxins). However, what caused conotoxin divergence remains unclear and may be related to the role of prey shift. Principal component analysis revealed clustering events within diet subgroups indicating peptide sequence similarity patterns based on the prey they subdue. Molecular analyses using multiple sequence alignment and structural element analysis were conducted to observe the events at the molecular level that caused the subgrouping. Three distinct subgroups were identified. Results showed homologous regions and conserved residues within diet subgroups but divergent between other groups. We specified that these structural elements caused subgrouping in alpha conotoxins that may play a role in function specificity. In each diet subgroup, amino acid character, length of intervening amino acids between cysteine residues, and polypeptide length influenced subgrouping. This study provides molecular insights into the role of prey shift, specifically diet preference, in conotoxin divergence.

Anti-Ovarian Cancer Conotoxins Identified from Conus Venom

Conotoxins constitute a treasury of drug resources and have attracted widespread attention. In order to explore biological candidates from the marine cone snail, we isolated and identified three novel conopeptides named as Vi14b, Vi002, Vi003, three conotoxin variants named as Mr3d.1, Mr3e.1, Tx3a.1, and three known conotoxins (Vi15a, Mr3.8 and TCP) from crude venoms of Conus virgo, Conus marmoreus and Conus texile. Mr3.8 (I-V, II-VI, III-IV) and Tx3a.1 (I-III, II-VI, IV-V) both showed a novel pattern of disulfide connectivity, different from that previously established for the µ- and ψ-conotoxins. Concerning the effect on voltage-gated sodium channels, Mr3e.1, Mr3.8, Tx3a.1, TCP inhibited Na_v1.4 or Na_v1.8 by 21.51~24.32% of currents at semi-activated state (TP2) at 10 μmol/L. Certain anti-ovarian cancer effects on ID-8 cells were exhibited by Tx3a.1, Mr3e.1 and Vi14b with IC₅₀ values of 24.29 µM, 54.97 µM and 111.6 µM, respectively. This work highlights the role of conotoxin libraries in subsequent drug discovery for ovarian cancer treatment.

Preparation and Functional Identification of a Novel Conotoxin QcMNCL-XIII0.1 from Conus quercinus

Conotoxins are tools used by marine Conus snails to hunt and are a significant repository for marine drug research. Conotoxins highly selectively coordinate different subtypes of various ion channels, and a few have been used in pain management. Although more than 8000 conotoxin genes have been found, the biological activity and function of most have not yet been examined. In this report, we selected the toxin gene QcMNCL-XIII0.1 from our previous investigation and studied it in vitro. First, we successfully prepared active recombinant QcMNCL-XIII0.1 using a TrxA (Thioredoxin A)-assisted folding expression vector based on genetic engineering technology. Animal experiments showed that the recombinant QcMNCL-XIII0.1 exhibited nerve conduction inhibition similar to that of pethidine hydrochloride. With flow cytometry combined fluorescent probe Fluo-4 AM, we found that 10 ng/μL recombinant QcMNCL-XIII0.1 inhibited the fluorescence intensity by 31.07% in the 293T cell model transfected with Cav3.1, implying an interaction between α1G T-type calcium channel protein and recombinant QcMNCL-XIII0.1. This toxin could be an important drug in biomedical research and medicine for pain control.

Mobilizing molluscan models and genomes in biology

Molluscs are among the most ancient, diverse, and important of all animal taxa. Even so, no individual mollusc species has emerged as a broadly applied model system in biology. We here make the case that both perceptual and methodological barriers have played a role in the relative neglect of molluscs as research organisms. We then summarize the current application and potential of molluscs and their genomes to address important questions in animal biology, and the state of the field when it comes to the availability of resources such as genome assemblies, cell lines, and other key elements necessary to mobilising the development of molluscan model systems. We conclude by contending that a cohesive research community that works together to elevate multiple molluscan systems to 'model' status will create new opportunities in addressing basic and applied biological problems, including general features of animal evolution. This article is part of the Theo Murphy meeting issue 'Molluscan genomics: broad insights and future directions for a neglected phylum'.

Morphological Analysis Reveals a Compartmentalized Duct in the Venom Apparatus of the Wasp Spider (Argiope bruennichi)

Spiders are one of the most successful groups of venomous animals, but surprisingly few species have been examined in sufficient detail to determine the structure of their venom systems. To learn more about the venom system of the family Araneidae (orb-weavers), we selected the wasp spider (Argiope bruennichi) and examined the general structure and morphology of the venom apparatus by light microscopy. This revealed morphological features broadly similar to those reported in the small number of other spiders subject to similar investigations. However, detailed evaluation of the venom duct revealed the presence of four structurally distinct compartments. We propose that these subunits facilitate the expression and secretion of venom components, as previously reported for similar substructures in pit vipers and cone snails.

3-Hydroxypropane-1,2-Diyl Dipalmitoleate-A Natural Compound with Dual Roles (CB1 Agonist/FAAH1 Blocker) in Inhibiting Ovarian Cancer Cell Line

Though it was once known that upregulated Cannabinoid Receptor (CB1) and downregulated Fatty Acid Amide Hydrolase (FAAH1) are associated with tumour aggressiveness and metastasis, it is now clear that upregulated CB1 levels more than a certain point cause accumulation of ceramide and directs cells to apoptosis. Hence, CB1 analogues/FAAH1 blockers are explored widely as anticancer drugs. There are reports on CB1-agonists and FAAH1-blockers separately, however, dual activities along with ovarian cancer-specific links are not established for any natural compound. With this setting, we describe for the first time the isolation of 3-hydroxypropane-1,2-diyl dipalmitoleate (564.48 Da) from a marine snail, Conus inscriptus, which binds to both CB1 and FAAH1 (glide energies: −70.61 and −30.52 kcal/mol, respectively). MD simulations indicate stable compound–target interaction for a minimum of 50 nanoseconds with relative invariabilities in R_g. The compound inhibited ovarian cancer cell line, PA1 at 1.7 μM. Structural and chemical interpretation of the compound (C2) was done using FT-IR, GC-MS, ESI-MS, ¹H and ¹³C-NMR (1 and 2D). Furthermore, a probable route for gram-scale synthesis of C2 is hinted herein. With the available preliminary data, molecular mechanisms involving dual roles for this potent molecule must be elucidated to understand the possibilities of usage as an anticancer drug.

Insights into how development and life-history dynamics shape the evolution of venom

Venomous animals are a striking example of the convergent evolution of a complex trait. These animals have independently evolved an apparatus that synthesizes, stores, and secretes a mixture of toxic compounds to the target animal through the infliction of a wound. Among these distantly related animals, some can modulate and compartmentalize functionally distinct venoms related to predation and defense. A process to separate distinct venoms can occur within and across complex life cycles as well as more streamlined ontogenies, depending on their life-history requirements. Moreover, the morphological and cellular complexity of the venom apparatus likely facilitates the functional diversity of venom deployed within a given life stage. Intersexual variation of venoms has also evolved further contributing to the massive diversity of toxic compounds characterized in these animals. These changes in the biochemical phenotype of venom can directly affect the fitness of these animals, having important implications in their diet, behavior, and mating biology. In this review, we explore the current literature that is unraveling the temporal dynamics of the venom system that are required by these animals to meet their ecological functions. These recent findings have important consequences in understanding the evolution and development of a convergent complex trait and its organismal and ecological implications.

Multi-omics investigations within the Phylum Mollusca, Class Gastropoda: from ecological application to breakthrough phylogenomic studies

Gastropods are the largest and most diverse class of mollusc and include species that are well studied within the areas of taxonomy, aquaculture, biomineralization, ecology, microbiome and health. Gastropod research has been expanding since the mid-2000s, largely due to large-scale data integration from next-generation sequencing and mass spectrometry in which transcripts, proteins and metabolites can be readily explored systematically. Correspondingly, the huge data added a great deal of complexity for data organization, visualization and interpretation. Here, we reviewed the recent advances involving gastropod omics ('gastropodomics') research from hundreds of publications and online genomics databases. By summarizing the current publicly available data, we present an insight for the design of useful data integrating tools and strategies for comparative omics studies in the future. Additionally, we discuss the future of omics applications in aquaculture, natural pharmaceutical biodiscovery and pest management, as well as to monitor the impact of environmental stressors.

Conus coronatus and Conus frigidus Venom: A New Source of Conopeptides with Analgesic Activity

BACKGROUND

Cone snails are a natural source of complex peptides with analgesic properties called conotoxins. These peptides are secreted in a complex venomic mixture and are predominantly smaller than 5 kDa. The present study aimed to document the analgesic activity of two species of Conus coronatus (C. coronatus) and Conus frigidus (C. frigidus) venom collected off the Iranian coast in a mouse behavioral test.

METHODS

Conotoxin containing fractions was extracted from the venom ducts and initially purified by column chromatography. The analgesic effect of the fractions was determined on formalin pain model and hot-plate test.

RESULTS

The results led to the identification of four fractions with analgesic activity in C. coronatus and two in C. frigidus. Only one fraction was able to reduce the flinching and licking in both acute pain and chronic pain phases of the formalin test. Moreover, the activity of this fraction remained 30 minutes on the hot-plate test. Purification of the fractions was carried out by RP-HPLC. LC-ESI-MS analysis of the fractions showed that the conotoxins of the analgesic fraction had molecular weights not previously reported.

CONCLUSION

The findings give insight into the venom of two previously under-investigated Conus species and reveal the therapeutic potential of the containing conopeptides.

Discovery Methodology of Novel Conotoxins from Conus Species

Cone snail venoms provide an ideal resource for neuropharmacological tools and drug candidates discovery, which have become a research hotspot in neuroscience and new drug development. More than 1,000,000 natural peptides are produced by cone snails, but less than 0.1% of the estimated conotoxins has been characterized to date. Hence, the discovery of novel conotoxins from the huge conotoxin resources with high-throughput and sensitive methods becomes a crucial key for the conotoxin-based drug development. In this review, we introduce the discovery methodology of new conotoxins from various Conus species. It focuses on obtaining full N- to C-terminal sequences, regardless of disulfide bond connectivity through crude venom purification, conotoxin precusor gene cloning, venom duct transcriptomics, venom proteomics and multi-omic methods. The protocols, advantages, disadvantages, and developments of different approaches during the last decade are summarized and the promising prospects are discussed as well.

Conotoxin Diversity in Chelyconus ermineus (Born, 1778) and the Convergent Origin of Piscivory in the Atlantic and Indo-Pacific Cones

The transcriptome of the venom duct of the Atlantic piscivorous cone species Chelyconus ermineus (Born, 1778) was determined. The venom repertoire of this species includes at least 378 conotoxin precursors, which could be ascribed to 33 known and 22 new (unassigned) protein superfamilies, respectively. Most abundant superfamilies were T, W, O1, M, O2, and Z, accounting for 57% of all detected diversity. A total of three individuals were sequenced showing considerable intraspecific variation: each individual had many exclusive conotoxin precursors, and only 20% of all inferred mature peptides were common to all individuals. Three different regions (distal, medium, and proximal with respect to the venom bulb) of the venom duct were analyzed independently. Diversity (in terms of number of distinct members) of conotoxin precursor superfamilies increased toward the distal region whereas transcripts detected toward the proximal region showed higher expression levels. Only the superfamilies A and I3 showed statistically significant differential expression across regions of the venom duct. Sequences belonging to the alpha (motor cabal) and kappa (lightning-strike cabal) subfamilies of the superfamily A were mainly detected in the proximal region of the venom duct. The mature peptides of the alpha subfamily had the α4/4 cysteine spacing pattern, which has been shown to selectively target muscle nicotinic-acetylcholine receptors, ultimately producing paralysis. This function is performed by mature peptides having a α3/5 cysteine spacing pattern in piscivorous cone species from the Indo-Pacific region, thereby supporting a convergent evolution of piscivory in cones.

Molecular diversity and function of jasmintides from Jasminum sambac

BACKGROUND

Jasmintides jS1 and jS2 from Jasminum sambac were previously identified as a novel family of cysteine-rich peptides (CRPs) with an unusual disulfide connectivity. However, very little else is known about jasmintides, particularly their molecular diversity and functions. Here, we report the discovery and characterization of a novel suite of jasmintides from J. sambac using transcriptomic, peptidomic, structural and functional tools.

RESULTS

Transcriptomic analysis of leaves, flowers and roots revealed 14 unique jasmintide precursors, all of which possess a three-domain architecture comprising a signal peptide, a pro-domain and a mature jasmintide domain. Peptidomic analysis, using fractionated mixtures of jasmintides and chemical derivatization of cysteine to pseudolysine, trypsin digestion and MS/MS sequencing, revealed an additional 86 jasmintides, some of which were post-translationally modified. NMR analysis showed that jasmintide jS3 has three anti-parallel β-strands with a three-disulfide connectivity of CysI-CysV, CysII-CysIV and CysIII-CysVI, which is similar to jasmintide jS1. Jasmintide jS3 was able to withstand thermal, acidic and enzymatic degradation and, importantly, exhibited antifeedant activity against mealworm Tenebrio molitor.

CONCLUSION

Together, this study expands the existing library of jasmintides and furthers our understanding of the molecular diversity and cystine framework of CRPs as scaffolds and tools for engineering peptides targeting pests.

Combined Transcriptomic and Proteomic Analysis of the Posterior Salivary Gland from the Southern Blue-Ringed Octopus and the Southern Sand Octopus

This study provides comprehensive proteomic profiles from the venom producing posterior salivary glands of octopus (superorder Octopodiformes) species. A combined transcriptomic and proteomic approach was used to identify 1703 proteins from the posterior salivary gland of the southern blue-ringed octopus, Hapalochlaena maculosa and 1300 proteins from the posterior salivary gland of the southern sand octopus, Octopus kaurna. The two proteomes were broadly similar; clustering of proteins into orthogroups revealed 937 that were shared between species. Serine proteases were particularly diverse and abundant in both species. Other abundant proteins included a large number of secreted proteins, many of which had no known conserved domains, or homology to proteins with known function. On the basis of homology to known venom proteins, 23 putative toxins were identified in H. maculosa and 24 in O. kaurna. These toxins span nine protein families: CAP (cysteine rich secretory proteins, antigen 5, parthenogenesis related), chitinase, carboxylesterase, DNase, hyaluronidase, metalloprotease, phospholipase, serine protease and tachykinin. Serine proteases were responsible for 70.9% and 86.3% of putative toxin expression in H. maculosa and O. kaurna, respectively, as determined using intensity based absolute quantification (iBAQ) measurements. Phylogenetic analysis of the putative toxin serine proteases revealed a similar suite of diverse proteins present in both species. Posterior salivary gland composition of H. maculosa and O. kaurna differ in several key aspects. While O. kaurna expressed the proteinaceous neurotoxin, tachykinin, this was absent from H. maculosa, perhaps reflecting the acquisition of a potent nonproteinaceous neurotoxin, tetrodotoxin (TTX) produced by bacteria in the salivary glands of that species. The dispersal factor, hyaluronidase was particularly abundant in H. maculosa. Chitinase was abundant in both species and is believed to facilitate envenomation in chitinous prey such as crustaceans. Cephalopods represent a largely unexplored source of novel proteins distinct from all other venomous taxa and are of interest for further inquiry, as novel proteinaceous toxins derived from venoms may contribute to pharmaceutical design.

From Mollusks to Medicine: A Venomics Approach for the Discovery and Characterization of Therapeutics from Terebridae Peptide Toxins

Animal venoms comprise a diversity of peptide toxins that manipulate molecular targets such as ion channels and receptors, making venom peptides attractive candidates for the development of therapeutics to benefit human health. However, identifying bioactive venom peptides remains a significant challenge. In this review we describe our particular venomics strategy for the discovery, characterization, and optimization of Terebridae venom peptides, teretoxins. Our strategy reflects the scientific path from mollusks to medicine in an integrative sequential approach with the following steps: (1) delimitation of venomous Terebridae lineages through taxonomic and phylogenetic analyses; (2) identification and classification of putative teretoxins through omics methodologies, including genomics, transcriptomics, and proteomics; (3) chemical and recombinant synthesis of promising peptide toxins; (4) structural characterization through experimental and computational methods; (5) determination of teretoxin bioactivity and molecular function through biological assays and computational modeling; (6) optimization of peptide toxin affinity and selectivity to molecular target; and (7) development of strategies for effective delivery of venom peptide therapeutics. While our research focuses on terebrids, the venomics approach outlined here can be applied to the discovery and characterization of peptide toxins from any venomous taxa.

Rapid expansion of the protein disulfide isomerase gene family facilitates the folding of venom peptides

Formation of correct disulfide bonds in the endoplasmic reticulum is a crucial step for folding proteins destined for secretion. Protein disulfide isomerases (PDIs) play a central role in this process. We report a previously unidentified, hypervariable family of PDIs that represents the most diverse gene family of oxidoreductases described in a single genus to date. These enzymes are highly expressed specifically in the venom glands of predatory cone snails, animals that synthesize a remarkably diverse set of cysteine-rich peptide toxins (conotoxins). Enzymes in this PDI family, termed conotoxin-specific PDIs, significantly and differentially accelerate the kinetics of disulfide-bond formation of several conotoxins. Our results are consistent with a unique biological scenario associated with protein folding: The diversification of a family of foldases can be correlated with the rapid evolution of an unprecedented diversity of disulfide-rich structural domains expressed by venomous marine snails in the superfamily Conoidea.

Specialized insulin is used for chemical warfare by fish-hunting cone snails

More than 100 species of venomous cone snails (genus Conus) are highly effective predators of fish. The vast majority of venom components identified and functionally characterized to date are neurotoxins specifically targeted to receptors, ion channels, and transporters in the nervous system of prey, predators, or competitors. Here we describe a venom component targeting energy metabolism, a radically different mechanism. Two fish-hunting cone snails, Conus geographus and Conus tulipa, have evolved specialized insulins that are expressed as major components of their venoms. These insulins are distinctive in having much greater similarity to fish insulins than to the molluscan hormone and are unique in that posttranslational modifications characteristic of conotoxins (hydroxyproline, γ-carboxyglutamate) are present. When injected into fish, the venom insulin elicits hypoglycemic shock, a condition characterized by dangerously low blood glucose. Our evidence suggests that insulin is specifically used as a weapon for prey capture by a subset of fish-hunting cone snails that use a net strategy to capture prey. Insulin appears to be a component of the nirvana cabal, a toxin combination in these venoms that is released into the water to disorient schools of small fish, making them easier to engulf with the snail's distended false mouth, which functions as a net. If an entire school of fish simultaneously experiences hypoglycemic shock, this should directly facilitate capture by the predatory snail.

Intraspecific variations in Conus geographus defence-evoked venom and estimation of the human lethal dose

Conus geographus is the most dangerous cone snail species known, with reported human fatality rates as high as 65%. Crude venom gland extracts have been used to determine animal LD50 and to aid the isolation of several potent paralytic toxins. However, not only is the composition of injected venoms known to differ significantly from that in dissected venom glands, but also to vary according to predatory or defensive stimuli. Therefore, to study the venom that is directly relevant to human envenomation, the defense-evoked venom of several specimens of C. geographus was collected and analyzed by standard LC-MS methods. The molecular composition of individual defense-evoked venom showed significant intraspecific variations, but a core of paralytic conotoxins including α-GI, α-GII, μ-GIIIA, ω-GVIA and ω-GVIIA was always present in large amounts, consistent with the symptomology and high fatality rate in humans. Differences between injected and dissected venoms obtained from the same specimen were also evident. Interestingly, an apparent linear correlation between the dry weight/volume of injected venom and the size of the shell allowed extrapolation to a human lethal dose (0.038-0.029 mg/kg) from an historic fatal case of C. geographus envenomation, which may help in the management of future victims.

Analgesic effect of Persian Gulf Conus textile venom

OBJECTIVES

Cone snails are estimated to consist of up to 700 species. The venom of these snails has yielded a rich source of novel peptides. This study was aimed to study the analgesic effect of Persian Gulf Conus textile and its comparison with morphine in mouse model.

MATERIALS AND METHODS

Samples were collected in Larak Island. The venom ducts were Isolated and kept on ice then homogenized. The mixture centrifuged at 10000 × g for 20 min. Supernatant was considered as extracted venom. The protein profile of venom determined using 15% sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Venom was administered intraperitoneally (IP) to evaluate the LD50 in Swiss albino mice. Different concentrations of Conus textile venom were injected intrathecally to mice to evaluate their analgesic effect in comparison to morphine. Injection was carried out between the L5 and L6 vertebrae. Differences between groups in the first and second phase were tested with Two-Way analysis of variance (ANOVA).

RESULTS

SDS-PAGE indicated 12 bands ranged between 6 and 180 KDa. Finally, ten ng of Conus crude venom showed the best analgesic activity in formalin test. No death observed up to 100 mg/kg. Analgesic activity of crude venom was more significant (P<0.05) in acute pain than inflammatory pain. The analgesic effect of 10 ng Conus venom was the same as morphine for reduction of inflammatory pain (P=0.27).

CONCLUSION

The venom of Persian Gulf Conus textile contains an analgesic component for reliving of acute pain which can lead to find an analgesic drug.

Venom variation during prey capture by the cone snail, Conus textile

Observations of the mollusc-hunting cone snail Conus textile during feeding reveal that prey are often stung multiple times in succession. While studies on the venom peptides injected by fish-hunting cone snails have become common, these approaches have not been widely applied to the analysis of the injected venoms from mollusc-hunters. We have successfully obtained multiple injected venom samples from C. textile individuals, allowing us to investigate venom compositional variation during prey capture. Our studies indicate that C. textile individuals alter the composition of prey-injected venom peptides during single feeding events. The qualitative results obtained by MALDI-ToF mass spectrometry are mirrored by quantitative changes in venom composition observed by reverse-phase high performance liquid chromatography. While it is unclear why mollusc-hunting cone snails inject prey multiple times prior to engulfment, our study establishes for the first time a link between this behavior and compositional changes of the venom during prey capture. Changes in venom composition during hunting may represent a multi-step strategy utilized by these venomous animals to slow and incapacitate prey prior to engulfment.

Sample limited characterization of a novel disulfide-rich venom peptide toxin from terebrid marine snail Terebra variegata

Disulfide-rich peptide toxins found in the secretions of venomous organisms such as snakes, spiders, scorpions, leeches, and marine snails are highly efficient and effective tools for novel therapeutic drug development. Venom peptide toxins have been used extensively to characterize ion channels in the nervous system and platelet aggregation in haemostatic systems. A significant hurdle in characterizing disulfide-rich peptide toxins from venomous animals is obtaining significant quantities needed for sequence and structural analyses. Presented here is a strategy for the structural characterization of venom peptide toxins from sample limited (4 ng) specimens via direct mass spectrometry sequencing, chemical synthesis and NMR structure elucidation. Using this integrated approach, venom peptide Tv1 from Terebra variegata was discovered. Tv1 displays a unique fold not witnessed in prior snail neuropeptides. The novel structural features found for Tv1 suggest that the terebrid pool of peptide toxins may target different neuronal agents with varying specificities compared to previously characterized snail neuropeptides.

Evolution of separate predation- and defence-evoked venoms in carnivorous cone snails

Venomous animals are thought to inject the same combination of toxins for both predation and defence, presumably exploiting conserved target pharmacology across prey and predators. Remarkably, cone snails can rapidly switch between distinct venoms in response to predatory or defensive stimuli. Here, we show that the defence-evoked venom of Conus geographus contains high levels of paralytic toxins that potently block neuromuscular receptors, consistent with its lethal effects on humans. In contrast, C. geographus predation-evoked venom contains prey-specific toxins mostly inactive at human targets. Predation- and defence-evoked venoms originate from the distal and proximal regions of the venom duct, respectively, explaining how different stimuli can generate two distinct venoms. A specialized defensive envenomation strategy is widely evolved across worm, mollusk and fish-hunting cone snails. We propose that defensive toxins, originally evolved in ancestral worm-hunting cone snails to protect against cephalopod and fish predation, have been repurposed in predatory venoms to facilitate diversification to fish and mollusk diets.

Combined proteomic and transcriptomic interrogation of the venom gland of Conus geographus uncovers novel components and functional compartmentalization

Cone snails are highly successful marine predators that use complex venoms to capture prey. At any given time, hundreds of toxins (conotoxins) are synthesized in the secretory epithelial cells of the venom gland, a long and convoluted organ that can measure 4 times the length of the snail's body. In recent years a number of studies have begun to unveil the transcriptomic, proteomic and peptidomic complexity of the venom and venom glands of a number of cone snail species. By using a combination of DIGE, bottom-up proteomics and next-generation transcriptome sequencing the present study identifies proteins involved in envenomation and conotoxin maturation, significantly extending the repertoire of known (poly)peptides expressed in the venom gland of these remarkable animals. We interrogate the molecular and proteomic composition of different sections of the venom glands of 3 specimens of the fish hunter Conus geographus and demonstrate regional variations in gene expression and protein abundance. DIGE analysis identified 1204 gel spots of which 157 showed significant regional differences in abundance as determined by biological variation analysis. Proteomic interrogation identified 342 unique proteins including those that exhibited greatest fold change. The majority of these proteins also exhibited significant changes in their mRNA expression levels validating the reliability of the experimental approach. Transcriptome sequencing further revealed a yet unknown genetic diversity of several venom gland components. Interestingly, abundant proteins that potentially form part of the injected venom mixture, such as echotoxins, phospholipase A2 and con-ikots-ikots, classified into distinct expression clusters with expression peaking in different parts of the gland. Our findings significantly enhance the known repertoire of venom gland polypeptides and provide molecular and biochemical evidence for the compartmentalization of this organ into distinct functional entities.

Influence of disulfide connectivity on structure and bioactivity of α-conotoxin TxIA

Cone snails express a sophisticated arsenal of small bioactive peptides known as conopeptides or conotoxins (CTxs). Through evolutionary selection, these peptides have gained the ability to interact with a range of ion channels and receptors, such as nicotinic acetylcholine receptors (nAChRs). Here, we used reversed-phase high performance liquid chromatography (RP-HPLC) and electrospray ionization-mass spectrometry (ESI-MS) to explore the venom peptide diversity of Conus textile, a species of cone snail native to Hainan, China. One fraction of C. textile crude venom potently blocked α3β2 nAChRs. Subsequent purification, synthesis, and tandem mass spectrometric analysis demonstrated that the most active compound in this fraction was identical to α-CTx TxIA, an antagonist of α3β2 nAChRs. Then three disulfide isoforms of α-CTx TxIA were synthesized and their activities were investigated systematically for the first time. As we observed, disulfide isomerisation was particularly important for α-CTx TxIA potency. Although both globular and ribbon isomers showed similar retention times in RP-HPLC, globular TxIA potently inhibited α3β2 nAChRs with an IC50 of 5.4 nM, while ribbon TxIA had an IC50 of 430 nM. In contrast, beads isomer had little activity towards α3β2 nAChRs. Two-step oxidation synthesis produced the highest yield of α-CTx TxIA native globular isomer, while a one-step production process based on random oxidation folding was not suitable. In summary, this study demonstrated the relationship between conotoxin activity and disulfide connectivity on α-CTx TxIA.

A 'conovenomic' analysis of the milked venom from the mollusk-hunting cone snail Conus textile--the pharmacological importance of post-translational modifications

Cone snail venoms provide a largely untapped source of novel peptide drug leads. To enhance the discovery phase, a detailed comparative proteomic analysis was undertaken on milked venom from the mollusk-hunting cone snail, Conus textile, from three different geographic locations (Hawai'i, American Samoa and Australia's Great Barrier Reef). A novel milked venom conopeptide rich in post-translational modifications was discovered, characterized and named α-conotoxin TxIC. We assign this conopeptide to the 4/7 α-conotoxin family based on the peptide's sequence homology and cDNA pre-propeptide alignment. Pharmacologically, α-conotoxin TxIC demonstrates minimal activity on human acetylcholine receptor models (100 μM, <5% inhibition), compared to its high paralytic potency in invertebrates, PD50 = 34.2 nMol kg(-1). The non-post-translationally modified form, [Pro](2,8)[Glu](16)α-conotoxin TxIC, demonstrates differential selectivity for the α3β2 isoform of the nicotinic acetylcholine receptor with maximal inhibition of 96% and an observed IC50 of 5.4 ± 0.5 μM. Interestingly its comparative PD50 (3.6 μMol kg(-1)) in invertebrates was ~100 fold more than that of the native peptide. Differentiating α-conotoxin TxIC from other α-conotoxins is the high degree of post-translational modification (44% of residues). This includes the incorporation of γ-carboxyglutamic acid, two moieties of 4-trans hydroxyproline, two disulfide bond linkages, and C-terminal amidation. These findings expand upon the known chemical diversity of α-conotoxins and illustrate a potential driver of toxin phyla-selectivity within Conus.

Various conotoxin diversifications revealed by a venomic study of Conus flavidus

Conotoxins are peptide neurotoxins produced by predatory cone snails. They are mostly cysteine-rich short peptides with remarkable structural diversity. The conserved signal peptide sequences of their mRNA-encoded precursors have enabled the grouping of known conotoxins into a limited number of superfamilies. However, the conotoxins within each superfamily often present variable sequences, cysteine frameworks, and post-translational modifications. To understand better how conotoxins are diversified, we performed a venomic study with C. flavidus, an uninvestigated vermivorous Conus species, by combining transcriptomic and proteomic analyses. In order to obtain the full-length conotoxin sequences, protease digestion was not performed with the venom extraction prior to spectra acquisition via tandem mass spectrometry (MS/MS). Because conotoxins are produced from mRNA-encoded precursors by means of proteolytic cleavage, nonspecific digestion of precursors was applied during the database search. Special attention was also paid in interpreting the MS/MS spectra. All together, these analyses identified 69 nonredundant cDNA sequences and 31 conotoxin components with confident MS/MS spectra. A new Q-superfamily was also identified. More importantly, this study revealed that conotoxin-encoding transcripts are diversified by hypermutation, fragment insertion/deletion, and mutation-induced premature termination, and that a single mRNA species can produce multiple toxin products through alternative post-translational modifications and alternative cleavages of the translated precursor. These multiple diversification strategies at different levels may explain, at least in part, the diversity of conotoxins, and provide the basis for further investigation.

Evaluation and optimization of mass spectrometric settings during data-dependent acquisition mode: focus on LTQ-Orbitrap mass analyzers

Mass-spectrometry-based proteomics has evolved as the preferred method for the analysis of complex proteomes. Undoubtedly, recent advances in mass spectrometry instrumentation have greatly enhanced proteomic analysis. A popular instrument platform in proteomics research is the LTQ-Orbitrap mass analyzer. In this tutorial, we discuss the significance of evaluating and optimizing mass spectrometric settings on the LTQ-Orbitrap during CID data-dependent acquisition (DDA) mode to improve protein and peptide identification rates. We focus on those MS and MS/MS parameters that have been systematically examined and evaluated by several researchers and are commonly used during DDA. More specifically, we discuss the effect of mass resolving power, preview mode for FTMS scan, monoisotopic precursor selection, signal threshold for triggering MS/MS events, number of microscans per MS/MS scan, number of MS/MS events, automatic gain control target value (ion population) for MS and MS/MS, maximum ion injection time for MS/MS, rapid and normal scan rate, and prediction of ion injection time. We furthermore present data from the latest generation LTQ-Orbitrap system, the Orbitrap Elite, along with recommended MS and MS/MS parameters. The Orbitrap Elite outperforms the Orbitrap Classic in terms of scan speed, sensitivity, dynamic range, and resolving power and results in higher identification rates. Several of the optimized MS parameters determined on the LTQ-Orbitrap Classic and XL were easily transferable to the Orbitrap Elite, whereas others needed to be reevaluated. Finally, the Q Exactive and HCD are briefly discussed, as well as sample preparation, LC-optimization, and bioinformatics analysis. We hope this tutorial will serve as guidance for researchers new to the field of proteomics and assist in achieving optimal results.

Simultaneous structure-activity studies and arming of natural products by C-H amination reveal cellular targets of eupalmerin acetate

Natural products have a venerable history of, and enduring potential for the discovery of useful biological activity. To fully exploit this, the development of chemical methodology that can functionalize unique sites within these complex structures is highly desirable. Here, we describe the use of rhodium(II)-catalysed C-H amination reactions developed by Du Bois to carry out simultaneous structure-activity relationship studies and arming (alkynylation) of natural products at 'unfunctionalized' positions. Allylic and benzylic C-H bonds in the natural products undergo amination while olefins undergo aziridination, and tertiary amine-containing natural products are converted to amidines by a C-H amination-oxidation sequence or to hydrazine sulfamate zwitterions by an unusual N-amination. The alkynylated derivatives are ready for conversion into cellular probes that can be used for mechanism-of-action studies. Chemo- and site-selectivity was studied with a diverse library of natural products. For one of these-the marine-derived anticancer diterpene, eupalmerin acetate-quantitative proteome profiling led to the identification of several protein targets in HL-60 cells, suggesting a polypharmacological mode of action.

Conus vexillum venom induces oxidative stress in Ehrlich's ascites carcinoma cells: an insight into the mechanism of induction

BACKGROUND

It is estimated that venoms of marine cone snails (genus Conus) contain more than 100,000 different small peptides with a wide range of pharmacological and biological actions. Some of these peptides were developed into potential therapeutic agents and as molecular tools to understand biological functions of nervous and cardiovascular systems. In this study we examined the cytotoxic and anticancer properties of the marine vermivorous cone snail Conus vexillum (collected from Hurgada and Sharm El-Shaikh, Red Sea, Egypt) and suggest the possible mechanisms involved. The in vitro cytotoxic effects of Conus venom were assessed against Ehrlich's ascites carcinoma (EAC) cells.

RESULTS

Conus venom treatment resulted in concentration-dependent cytotoxicity as indicated by a lactate dehydrogenase leakage assay. Apoptotic effects were measured in vivo by measuring levels of reactive oxygen species and oxidative defense agents in albino mice injected with EAC cells. Conus venom (1.25 mg/kg) induced a significant increase (p < 0.05) in several oxidative stress biomarkers (lipid peroxidation, protein carbonyl content and reactive nitrogen intermediates) of EAC cells after 3, 6, 9 and 12 hours of venom injection. Conus venom significantly reduced (p < 0.05) the activities of oxidative defense enzymes (catalase and superoxide dismutase) as well as the total antioxidant capacity of EAC cells, as evidenced by lowered levels of reduced glutathione.

CONCLUSIONS

These results demonstrate the cytotoxic potential of C. vexillum venom by inducing oxidative stress mediated mechanisms in tumor cells and suggest that the venom contains novel molecules with potential anticancer activity.

A GTP affinity probe for proteomics highlights flexibility in purine nucleotide selectivity

GTP affinity probes are important tools for the study of GTP-binding proteins, and proteomic profiling is a powerful methodology well suited for the study of such a diverse class of proteins. Here, we synthesize and characterize a photoreactive GTP affinity probe that covalently photocross-links to protein targets and has an alkyne handle for click chemistry conjugation to reporter tags. The GTP-BP-yne probe facilitated identification of a variety of GTP-binding proteins by mass spectrometry, such as small GTPases and members of the GTP1/OBG family. Several ATP-binding proteins were also identified, highlighting variability in purine nucleotide selectivity of some proteins, and the probe was used to elucidate targets' relative nucleotide selectivities. The GTP-BP-yne probe will be a useful tool for the study of GTP-binding proteins, especially when targets of interest are not known a priori.

Glycosylation of conotoxins

Conotoxins are small peptides present in the venom of cone snails. The snail uses this venom to paralyze and capture prey. The constituent conopeptides display a high level of chemical diversity and are of particular interest for scientists as tools employed in neurological studies and for drug development, because they target with exquisite specificity membrane receptors, transporters, and various ion channels in the nervous system. However, these peptides are known to contain a high frequency and variability of post-translational modifications-including sometimes O-glycosylation-which are of importance for biological activity. The potential application of specific conotoxins as neuropharmalogical agents and chemical probes requires a full characterization of the relevant peptides, including the structure of the carbohydrate part. In this review, the currently existing knowledge of O-glycosylation of conotoxins is described.

Comparative analysis of proteases in the injected and dissected venom of cone snail species

The venom of cone snails has been the subject of intense studies because it contains small neuroactive peptides of therapeutic value. However, much less is known about their larger proteins counterparts and their role in prey envenomation. Here, we analyzed the proteolytic enzymes in the injected venom of Conus purpurascens and Conus ermineus (piscivorous), and the dissected venom of C. purpurascens, Conus marmoreus (molluscivorous) and Conus virgo (vermivorous). Zymograms show that all venom samples displayed proteolytic activity on gelatin. However, the electrophoresis patterns and sizes of the proteases varied considerably among these four species. The protease distribution also varied dramatically between the injected and dissected venom of C. purpurascens. Protease inhibitors demonstrated that serine and metalloproteases are responsible for the gelatinolytic activity. We found fibrinogenolytic activity in the injected venom of C. ermineus suggesting that this venom might have effects on the hemostatic system of the prey. Remarkable differences in protein and protease expression were found in different sections of the venom duct, indicating that these components are related to the storage granules and that they participate in venom biosynthesis. Consequently, different conoproteases play major roles in venom processing and prey envenomation.

Selective inhibitors and tailored activity probes for lipoprotein-associated phospholipase A(2)

Lipoprotein-associated phospholipase A(2) (Lp-PLA(2) or PLA(2)G7) binds to low-density lipoprotein (LDL) particles, where it is thought to hydrolyze oxidatively truncated phospholipids. Lp-PLA(2) has also been implicated as a pro-tumorigenic enzyme in human prostate cancer. Several inhibitors of Lp-PLA(2) have been described, including darapladib, which is currently in phase 3 clinical development for the treatment of atherosclerosis. The selectivity that darapladib and other Lp-PLA(2) inhibitors display across the larger serine hydrolase family has not, however, been reported. Here, we describe the use of both general and tailored activity-based probes for profiling Lp-PLA(2) and inhibitors of this enzyme in native biological systems. We show that both darapladib and a novel class of structurally distinct carbamate inhibitors inactivate Lp-PLA(2) in mouse tissues and human cell lines with high selectivity. Our findings thus identify both inhibitors and chemoproteomic probes that are suitable for investigating Lp-PLA(2) function in biological systems.

Therapeutic potential of conopeptides

Conopeptides from the venoms of marine snails have attracted much interest as leads in drug design. Currently, one drug, Prialt(®), is on the market as a treatment for chronic neuropathic pain. Conopeptides target a range of ion channels, receptors and transporters, and are typically small, relatively stable peptides that are generally amenable to production using solid-phase peptide synthesis. With only a small fraction of the predicted diversity of conopeptides examined so far, these peptides represent an exciting and largely untapped resource for drug discovery. Recent efforts at chemically re-engineering conopeptides to improve their biopharmaceutical properties promise to accelerate the translation of these fascinating marine peptides to the clinic.

Scorpion toxins specific for potassium (K+) channels: a historical overview of peptide bioengineering

Scorpion toxins have been central to the investigation and understanding of the physiological role of potassium (K⁺) channels and their expansive function in membrane biophysics. As highly specific probes, toxins have revealed a great deal about channel structure and the correlation between mutations, altered regulation and a number of human pathologies. Radio- and fluorescently-labeled toxin isoforms have contributed to localization studies of channel subtypes in expressing cells, and have been further used in competitive displacement assays for the identification of additional novel ligands for use in research and medicine. Chimeric toxins have been designed from multiple peptide scaffolds to probe channel isoform specificity, while advanced epitope chimerization has aided in the development of novel molecular therapeutics. Peptide backbone cyclization has been utilized to enhance therapeutic efficiency by augmenting serum stability and toxin half-life in vivo as a number of K⁺-channel isoforms have been identified with essential roles in disease states ranging from HIV, T-cell mediated autoimmune disease and hypertension to various cardiac arrhythmias and Malaria. Bioengineered scorpion toxins have been monumental to the evolution of channel science, and are now serving as templates for the development of invaluable experimental molecular therapeutics.

Marine proteomics: a critical assessment of an emerging technology

The application of proteomics to marine sciences has increased in recent years because the proteome represents the interface between genotypic and phenotypic variability and, thus, corresponds to the broadest possible biomarker for eco-physiological responses and adaptations. Likewise, proteomics can provide important functional information regarding biosynthetic pathways, as well as insights into mechanism of action, of novel marine natural products. The goal of this review is to (1) explore the application of proteomics methodologies to marine systems, (2) assess the technical approaches that have been used, and (3) evaluate the pros and cons of this proteomic research, with the intent of providing a critical analysis of its future roles in marine sciences. To date, proteomics techniques have been utilized to investigate marine microbe, plant, invertebrate, and vertebrate physiology, developmental biology, seafood safety, susceptibility to disease, and responses to environmental change. However, marine proteomics studies often suffer from poor experimental design, sample processing/optimization difficulties, and data analysis/interpretation issues. Moreover, a major limitation is the lack of available annotated genomes and proteomes for most marine organisms, including several "model species". Even with these challenges in mind, there is no doubt that marine proteomics is a rapidly expanding and powerful integrative molecular research tool from which our knowledge of the marine environment, and the natural products from this resource, will be significantly expanded.

Secretion and maturation of conotoxins in the venom ducts of Conus textile

The 700 or more species of cone snail attack prey by employing complex venom which can vary considerably both within species and from one species to another. Cone snail venom is remarkable for the high proportion of conotoxins with varied post-translational modifications (PTMs) and for the production of more diverse toxin scaffolds than any other known venomous animal. The venom gland, which is several times longer than its shell, is also unique in being tubular. These unusual characteristics both raise questions, and provide the opportunity for research, concerning the secretion and maturation of conotoxins along the venom duct, a process which is currently not fully understood. This research uses the two mass spectrometric techniques of isotope Coded Affinity Tagging (ICAT) and label-free quantification to study each of five portions of the venom duct of Conus textile snails from New Caledonia. Fifteen conotoxins, several with different post-translational modifications (PTMs) were identified and quantified. One hundred and forty three non-identified conotoxins were also quantified. Distinctive patterns emerged, with the largest group of conotoxins increasing, then peaking in the central-proximal part, before decreasing; whilst the second largest group peaked in the distal region, generally displaying nothing in the first parts. Conotoxins from different superfamilies were commonly found to have similar distributions. A new conotoxin, PCCSKLHDNSCCGL*, was sequenced. A comparison is made with other studies to see how the process varies in cone snails from different regions.

Constrained de novo sequencing of conotoxins

De novo peptide sequencing by mass spectrometry (MS) can determine the amino acid sequence of an unknown peptide without reference to a protein database. MS-based de novo sequencing assumes special importance in focused studies of families of biologically active peptides and proteins, such as hormones, toxins, and antibodies, for which amino acid sequences may be difficult to obtain through genomic methods. These protein families often exhibit sequence homology or characteristic amino acid content; yet, current de novo sequencing approaches do not take advantage of this prior knowledge and, hence, search an unnecessarily large space of possible sequences. Here, we describe an algorithm for de novo sequencing that incorporates sequence constraints into the core graph algorithm and thereby reduces the search space by many orders of magnitude. We demonstrate our algorithm in a study of cysteine-rich toxins from two cone snail species (Conus textile and Conus stercusmuscarum) and report 13 de novo and about 60 total toxins.

Elucidation of the molecular envenomation strategy of the cone snail Conus geographus through transcriptome sequencing of its venom duct

Background

The fish-hunting cone snail, Conus geographus, is the deadliest snail on earth. In the absence of medical intervention, 70% of human stinging cases are fatal. Although, its venom is known to consist of a cocktail of small peptides targeting different ion-channels and receptors, the bulk of its venom constituents, their sites of manufacture, relative abundances and how they function collectively in envenomation has remained unknown.

Results

We have used transcriptome sequencing to systematically elucidate the contents the C. geographus venom duct, dividing it into four segments in order to investigate each segment’s mRNA contents. Three different types of calcium channel (each targeted by unrelated, entirely distinct venom peptides) and at least two different nicotinic receptors appear to be targeted by the venom. Moreover, the most highly expressed venom component is not paralytic, but causes sensory disorientation and is expressed in a different segment of the venom duct from venoms believed to cause sensory disruption. We have also identified several new toxins of interest for pharmaceutical and neuroscience research.

Conclusions

Conus geographus is believed to prey on fish hiding in reef crevices at night. Our data suggest that disorientation of prey is central to its envenomation strategy. Furthermore, venom expression profiles also suggest a sophisticated layering of venom-expression patterns within the venom duct, with disorientating and paralytic venoms expressed in different regions. Thus, our transcriptome analysis provides a new physiological framework for understanding the molecular envenomation strategy of this deadly snail.