Caspase-independent apoptosis induced in rat liver cells by plancitoxin I, the major lethal factor from the crown-of-thorns starfish Acanthaster planci venom

Injury affects coelomic fluid proteome of the common starfish, Asterias rubens

Echinoderms, possessing outstanding regenerative capabilities, provide a unique model system for the study of response to injury. However, little is known about the proteomic composition of coelomic fluid, an important biofluid circulating throughout the animal's body and reflecting the overall biological status of the organism. In this study, we used LC-MALDI tandem mass spectrometry to characterize the proteome of the cell-free coelomic fluid of the starfish Asterias rubens and to follow the changes occurring in response to puncture wound and blood loss. In total, 91 proteins were identified, of which 61 were extracellular soluble and 16 were bound to the plasma membrane. The most represented functional terms were 'pattern recognition receptor activity' and 'peptidase inhibitor activity'. A series of candidate proteins involved in early response to injury was revealed. Ependymin, β-microseminoprotein, serum amyloid A and avidin-like proteins, which are known to be involved in intestinal regeneration in the sea cucumber, were also identified as injury-responsive proteins. Our results expand the list of proteins potentially involved in defense and regeneration in echinoderms and demonstrate dramatic effects of injury on the coelomic fluid proteome.

In Vitro Anticancer and Proapoptotic Activities of Steroidal Glycosides from the Starfish Anthenea aspera

New marine glycoconjugates—the steroidal glycosides designated as anthenosides V–X (1–3)—and the seven previously known anthenosides E (4), G (5), J (6), K (7), S1 (8), S4 (9), and S6 (10) were isolated from the extract of the tropical starfish Anthenea aspera. The structures of 1–3 were elucidated by extensive NMR and ESIMS techniques. Glycoside 1 contains a rare 5α-cholest-8(14)-ene-3α,7β,16α-hydroxysteroidal nucleus. Compounds 2 and 3 were isolated as inseparable mixtures of epimers. All investigated compounds (1–10) at nontoxic concentrations inhibited colony formation of human melanoma RPMI-7951, breast cancer T-47D, and colorectal carcinoma HT-29 cells to a variable degree. The mixture of 6 and 7 possessed significant anticancer activity and induced apoptosis of HT-29 cells. The molecular mechanism of the proapoptotic action of this mixture was shown to be associated with the regulation of anti- and proapoptotic protein expression followed by the activation of initiator and effector caspases.

Chemical Ecology of Chemosensation in Asteroidea: Insights Towards Management Strategies of Pest Species

Within the Phylum Echinodermata, the class Asteroidea, commonly known as starfish and sea stars, encompasses a large number of benthos inhabiting genera and species with various feeding modalities including herbivores, carnivores, omnivores and detritivores. The Asteroidea rely on chemosensation throughout their life histories including hunting prey, avoiding or deterring predators, in the formation of spawning aggregations, synchronizing gamete release and targeting appropriate locations for larval settlement. The identities of many of the chemical stimuli that mediate these physiological and behavioural processes remain unresolved even though evidence indicates they play pivotal roles in the functionality of benthic communities. Aspects of chemosensation, as well as putative chemically-mediated behaviours and the molecular mechanisms of chemoreception, within the Asteroidea are reviewed here, with particular reference to the coral reef pest the Crown-of-Thorns starfish Acanthaster planci species complex, in the context of mitigation of population outbreaks.

Combined proteomics and transcriptomics identifies sting-related toxins of jellyfish Cyanea nozakii

Jellyfish sting has become a worldwide issue of critical concern to human health and safety in coastal areas in recent decades. Cyanea nozakii is one of the dominant blooming species and dangerous stingers in China. However, it remains unclear how many and what types of toxins are present in the venom. So, we used a combined transcriptomics and proteomics approach to investigate the venom composition of jellyfish C. nozakii. In total 4,608,524 Illumina valid reads were obtained to de novo assemble to 40,434 unigenes in the transcriptomics analysis. And, a total of 311,635 MS/MS spectra with 12,247 unique MS/MS spectra were generated to 1556 homologous proteins in the proteomics analysis. 174 potential toxin proteins were identified, with 27 proteins homology to the toxins from venomous animals, including phospholipase A2, zinc metalloproteinase-disintegrin agkistin, serine protease inhibitor, plancitoxin-1, alpha-latrocrustotoxin-Lt1a, etc. This study described the transcriptomics and venom proteomics of jellyfish C. nozakii for the first time. Our findings provide a comprehensive understanding of the venom composition of C. nozakii. Furthermore, the results may also be very helpful for the discovery of novel bioactive proteins, as well as the development of effective treatments for jellyfish sting in the future.

BIOLOGICAL SIGNIFICANCE

Jellyfish Cyanea nozakii is one of the most dangerous stingers in the coast of china. Hundreds of thousands of people would be stung every year and victims suffered a severe pain, itch, swelling, inflammation, wheal and even more serious consequence. However, it remains unclear how many and what types of toxins are present as well as the relationship between the clinical symptoms and toxins. Our combined transcriptomics and proteomics findings can provide a comprehensive understanding of the venom composition of C. nozakii and will also be helpful for the development of effective treatments for jellyfish sting in the future.

Global Transcriptome Analysis of the Tentacle of the Jellyfish Cyanea capillata Using Deep Sequencing and Expressed Sequence Tags: Insight into the Toxin- and Degenerative Disease-Related Transcripts

BACKGROUND

Jellyfish contain diverse toxins and other bioactive components. However, large-scale identification of novel toxins and bioactive components from jellyfish has been hampered by the low efficiency of traditional isolation and purification methods.

RESULTS

We performed de novo transcriptome sequencing of the tentacle tissue of the jellyfish Cyanea capillata. A total of 51,304,108 reads were obtained and assembled into 50,536 unigenes. Of these, 21,357 unigenes had homologues in public databases, but the remaining unigenes had no significant matches due to the limited sequence information available and species-specific novel sequences. Functional annotation of the unigenes also revealed general gene expression profile characteristics in the tentacle of C. capillata. A primary goal of this study was to identify putative toxin transcripts. As expected, we screened many transcripts encoding proteins similar to several well-known toxin families including phospholipases, metalloproteases, serine proteases and serine protease inhibitors. In addition, some transcripts also resembled molecules with potential toxic activities, including cnidarian CfTX-like toxins with hemolytic activity, plancitoxin-1, venom toxin-like peptide-6, histamine-releasing factor, neprilysin, dipeptidyl peptidase 4, vascular endothelial growth factor A, angiotensin-converting enzyme-like and endothelin-converting enzyme 1-like proteins. Most of these molecules have not been previously reported in jellyfish. Interestingly, we also characterized a number of transcripts with similarities to proteins relevant to several degenerative diseases, including Huntington's, Alzheimer's and Parkinson's diseases. This is the first description of degenerative disease-associated genes in jellyfish.

CONCLUSION

We obtained a well-categorized and annotated transcriptome of C. capillata tentacle that will be an important and valuable resource for further understanding of jellyfish at the molecular level and information on the underlying molecular mechanisms of jellyfish stinging. The findings of this study may also be used in comparative studies of gene expression profiling among different jellyfish species.

Plancitoxin I from the venom of crown-of-thorns starfish (Acanthaster planci) induces oxidative and endoplasmic reticulum stress associated cytotoxicity in A375.S2 cells

The crown-of-thorns starfish Acanthaster planci is a venomous starfish whose venom provokes strong cytotoxicity. In the present study, the purified cytotoxic toxin of A. planci venom (CAV) was identified as plancitoxin I protein by mass spectrum analyses. This study aims to investigate the molecular mechanism underlying the cytotoxicity function of plancitoxin I by focusing on the oxidative stress, mitochondrial dysfunction and endoplasmic reticulum (ER) stress pathway in human melanoma A375.S2 cells. The results indicated that after being treated with CAV toxin, A375.S2 cells significantly decreased viability in a dose-dependent manner. The CAV was found to reduce the cellular antioxidant enzymes such as SOD and CAT, and there was a significant decrease in total thiol level and mtDNA integrity, and it enhanced the lipid peroxidation. In addition, CAV increased cytosolic Ca(2+) concentration, and enhanced the expression of the ER molecular chaperones GRP78 and CHOP in a dose-dependent manner. CAV significantly elevated the activity of caspase-3, -8 and -9, and reduced the ratio of Bcl-2/Bax. The cells exhibited apoptosis were determined by using propidium iodide (PI) staining of DNA fragmentation (sub-G1 peak). In summary, the results demonstrated that plancitoxin I inhibits the proliferation of A375.S2 cells through induction of oxidative stress, mitochondrial dysfunction and ER stress associated apoptosis.

Quo vadis venomics? A roadmap to neglected venomous invertebrates

Venomics research is being revolutionized by the increased use of sensitive -omics techniques to identify venom toxins and their transcripts in both well studied and neglected venomous taxa. The study of neglected venomous taxa is necessary both for understanding the full diversity of venom systems that have evolved in the animal kingdom, and to robustly answer fundamental questions about the biology and evolution of venoms without the distorting effect that can result from the current bias introduced by some heavily studied taxa. In this review we draw the outlines of a roadmap into the diversity of poorly studied and understood venomous and putatively venomous invertebrates, which together represent tens of thousands of unique venoms. The main groups we discuss are crustaceans, flies, centipedes, non-spider and non-scorpion arachnids, annelids, molluscs, platyhelminths, nemerteans, and echinoderms. We review what is known about the morphology of the venom systems in these groups, the composition of their venoms, and the bioactivities of the venoms to provide researchers with an entry into a large and scattered literature. We conclude with a short discussion of some important methodological aspects that have come to light with the recent use of new -omics techniques in the study of venoms.

Nemertean toxin genes revealed through transcriptome sequencing

Nemerteans are one of few animal groups that have evolved the ability to utilize toxins for both defense and subduing prey, but little is known about specific nemertean toxins. In particular, no study has identified specific toxin genes even though peptide toxins are known from some nemertean species. Information about toxin genes is needed to better understand evolution of toxins across animals and possibly provide novel targets for pharmaceutical and industrial applications. We sequenced and annotated transcriptomes of two free-living and one commensal nemertean and annotated an additional six publicly available nemertean transcriptomes to identify putative toxin genes. Approximately 63–74% of predicted open reading frames in each transcriptome were annotated with gene names, and all species had similar percentages of transcripts annotated with each higher-level GO term. Every nemertean analyzed possessed genes with high sequence similarities to known animal toxins including those from stonefish, cephalopods, and sea anemones. One toxin-like gene found in all nemerteans analyzed had high sequence similarity to Plancitoxin-1, a DNase II hepatotoxin that may function well at low pH, which suggests that the acidic body walls of some nemerteans could work to enhance the efficacy of protein toxins. The highest number of toxin-like genes found in any one species was seven and the lowest was three. The diversity of toxin-like nemertean genes found here is greater than previously documented, and these animals are likely an ideal system for exploring toxin evolution and industrial applications of toxins.

Spine venom of crown-of-thorns starfish (Acanthaster planci) induces antiproliferation and apoptosis of human melanoma cells (A375.S2)

The crown-of-thorns starfish (Acanthaster planci) is a venomous starfish. In this study, the extraction of A. planci spine venom (ASV) was performed by phosphate saline buffer, followed by assaying the cytotoxicity on human normal and tumor cells. It was found that human melanoma cells (A375.S2) were the most sensitive to the ASV solution. The cells, after incubation with ASV, significantly appeared to decrease cell viability and increase lactate dehydrogenase (LDH) release with a dose-dependent relationship. The extract of spine promoted loss of mitochondrial membrane potential (ΔΨm) and induced inter-nucleosomal DNA fragmentation in human melanoma cells. The cells exhibited apoptosis by using propidium iodide (PI) staining of DNA fragmentation; it was then determined by flow cytometry (sub-G1 peak). The molecular cytotoxicity of ASV was tested through evaluation of the apoptosis/necrosis ratio by double staining with annexin V and PI assay. The A. planci spine venom showed significant antiproliferation. The human melanoma cells revealed apoptosis at low dose (1.25 μg/ml), and necrosis occurred at high dose (5 μg/ml).

Cytotoxic and apoptotic activities of the plancitoxin I from the venom of crown-of-thorns starfish (Acanthaster planci) on A375.S2 cells

This study reports on a cytotoxic toxin derived from the venom of the crown-of-thorns starfish Acanthaster planci (CAV). The protein toxin was isolated through both ion-exchange and gel-filtration chromatography, and characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and mass spectrum analyzes. The CAV was identified as plancitoxin I protein. The mechanistic role of the CAV toxin was explored in human malignant melanoma A375.S2 cell death. The results indicated that after incubation with CAV toxin, cells significantly decreased in A375.S2 cell viability and increased in the lactate dehydrogenase (LDH) level in a dose-dependent manner. The assays indicated that CAV toxin promoted reactive oxygen species (ROS) production, induced nitric oxide (NO) formation, lost mitochondrial membrane potential (ΔΨm) and induced inter-nucleosomal DNA fragmentation in A375.S2 cells. The molecular cytotoxicity of the CAV toxin was tested through evaluation of the apoptosis/necrosis ratio by double staining with annexin V-FITC and a propidium iodide (PI) assay. The results suggested that CAV toxin induced a cytotoxic effect in A375.S2 cells via the apoptotic procedure, and may be associated with the regulation of the p38 pathways.

Whipworm genome and dual-species transcriptome analyses provide molecular insights into an intimate host-parasite interaction

Matthew Berriman and colleagues report the whole-genome sequences of the human-infective whipworm Trichuris trichiura and the mouse-infective laboratory model Trichuris muris. Their transcriptome analyses and examination of T. muris infection in mice provide insights into host response to infection and potential drug targets for this major soil-transmitted helminth.

Whipworms are common soil-transmitted helminths that cause debilitating chronic infections in man. These nematodes are only distantly related to Caenorhabditis elegans and have evolved to occupy an unusual niche, tunneling through epithelial cells of the large intestine. We report here the whole-genome sequences of the human-infective Trichuris trichiura and the mouse laboratory model Trichuris muris. On the basis of whole-transcriptome analyses, we identify many genes that are expressed in a sex- or life stage–specific manner and characterize the transcriptional landscape of a morphological region with unique biological adaptations, namely, bacillary band and stichosome, found only in whipworms and related parasites. Using RNA sequencing data from whipworm-infected mice, we describe the regulated T helper 1 (T_H1)-like immune response of the chronically infected cecum in unprecedented detail. In silico screening identified numerous new potential drug targets against trichuriasis. Together, these genomes and associated functional data elucidate key aspects of the molecular host-parasite interactions that define chronic whipworm infection.

High-molecular weight protein toxins of marine invertebrates and their elaborate modes of action

High-molecular weight protein toxins significantly contribute to envenomations by certain marine invertebrates, e.g., jellyfish and fire corals. Toxic proteins frequently evolved from enzymes meant to be employed primarily for digestive purposes. The cellular intermediates produced by such enzymatic activity, e.g., reactive oxygen species or lysophospholipids, rapidly and effectively mediate cell death by disrupting cellular integrity. Membrane integrity may also be disrupted by pore-forming toxins that do not exert inherent enzymatic activity. When targeted to specific pharmacologically relevant sites in tissues or cells of the natural enemy or prey, toxic enzymes or pore-forming toxins even may provoke fast and severe systemic reactions. Since toxin-encoding genes constitute "hot spots" of molecular evolution, continuous variation and acquirement of new pharmacological properties are guaranteed. This also makes individual properties and specificities of complex proteinaceous venoms highly diverse and inconstant. In the present chapter we portray high-molecular weight constituents of venoms present in box jellyfish, sea anemones, sea hares, fire corals and the crown-of-thorns starfish. The focus lies on the latest achievements in the attempt to elucidate their molecular modes of action.

Avian influenza virus A/chicken/Hubei/489/2004 (H5N1) induces caspase-dependent apoptosis in a cell-specific manner

The economic damage caused by H5N1 avian influenza virus outbreak in domestic poultry and the threat of this virus to human health make the research of this virus highly significant. During the 2004 outbreak of avian influenza in Hubei province, People's Republic of China, we isolated a new H5N1 subtype avian influenza virus named as A/chicken/Hubei/489/2004(H5N1) (shorten as AIVHubei489 here). In this study, the infectivity and apoptosis-inducing characteristics of AIVHubei489 were studied. We demonstrated that AIVHubei489 could infect MDCK cells and the infection induced apoptosis. Our data also showed that the apoptosis induced by this virus in MDCK cells was caspase activity dependent. Moreover, we proved that caspase 8 but not caspase 9 was involved in this apoptosis. The infectivity and apoptosis-inducing activity of AIVHubei489 in Vero and HeLa cells were also studied. Our results showed that AIVHubei489 could replicate in Vero and HeLa cells, but the infection did not cause apoptosis in either of the two cell lines. Thus, AIVHubei489 induced apoptosis through a caspase-dependent pathway in a cell-specific manner.