Gandhi Rádis-Baptista

Crotamine is a novel cell-penetrating protein from the venom of rattlesnake Crotalus durissus terrificus

Herein we report that crotamine, a small lysine‐ and cysteine‐rich protein from the venom of the South American rattlesnake, can rapidly penetrate into different cell types and mouse blastocysts in vitro. In vivo, crotamine strongly labels cells from mouse bone marrow and spleen and from peritoneal liquid, as shown by fluorescent confocal laser‐scanning microscopy. Nuclear localization of crotamine was observed in both fixed and unfixed cells. In the cytoplasm, crotamine specifically associates with centrosomes and thus allows us to follow the process of centriole duplication and separation. In the nucleus, it binds to the chromosomes at S/G2 phase, when centrioles start dividing. Moreover, crotamine appears as a marker of actively proliferating cells, as shown by 5‐BrdU cell‐proliferation assay. Crotamine in the micromolar range proved nontoxic to any of the cell cultures tested and did not affect the pluripotency of ES cells or the development of mouse embryos.

Crotamine Mediates Gene Delivery into Cells through the Binding to Heparan Sulfate Proteoglycans

Recently we have shown that crotamine, a toxin from the South American rattlesnake Crotalus durissus terrificus venom, belongs to the family of cell-penetrating peptides. Moreover, crotamine was demonstrated to be a marker of centrioles, of cell cycle, and of actively proliferating cells. Herein we show that this toxin at non-toxic concentrations is also capable of binding electrostatically to plasmid DNA forming DNA-peptide complexes whose stabilities overcome the need for chemical conjugation for carrying nucleic acids into cells. Interestingly, crotamine demonstrates cell specificity and targeted delivery of plasmid DNA into actively proliferating cells both in vitro and in vivo, which distinguishes crotamine from other known natural cell-penetrating peptides. The mechanism of crotamine penetration and cargo delivery into cells was also investigated, showing the involvement of heparan sulfate proteoglycans in the uptake phase, which is followed by endocytosis and peptide accumulation within the acidic endosomal vesicles. Finally, the permeabilization of endosomal membranes induced by crotamine results in the leakage of the vesicles contents to the cell cytosol.

Transcriptome analysis of the Amazonian viper Bothrops atrox venom gland using expressed sequence tags (ESTs)

Bothrops atrox is a highly dangerous pit viper in the Brazilian Amazon region. We produced a global catalogue of gene transcripts to identify the main toxin and other protein families present in the B. atrox venom gland. We prepared a directional cDNA library, from which a set of 610 high quality expressed sequence tags (ESTs) were generated by bioinformatics processing. Our data indicated a predominance of transcripts encoding mainly metalloproteinases (59% of the toxins). The expression pattern of the B. atrox venom was similar to Bothrops insularis, Bothrops jararaca and Bothrops jararacussu in terms of toxin type, although some differences were observed. B. atrox showed a higher amount of the PIII class of metalloproteinases which correlates well with the observed intense hemorrhagic action of its toxin. Also, the PLA2 content was the second highest in this sample compared to the other three Bothrops transcriptomes. To our knowledge, this work is the first transcriptome analysis of an Amazonian rain forest pit viper and it will contribute to the body of knowledge regarding the gene diversity of the venom gland of members of the Bothrops genus. Moreover, our results can be used for future studies with other snake species from the Amazon region to investigate differences in gene patterns or phylogenetic relationships.

Crotamine, a small basic polypeptide myotoxin from rattlesnake venom with cell-penetrating properties.

Crotamine, a low molecular weight cationic polypeptide from the venom of the South American rattlesnake Crotalus durissus terrificus is a natural cell-penetrating peptide with functional versatility. The presence of nine lysine residues and three disulfide bonds renders crotamine highly compact, stable and positively charged. Topologically, crotamine adopts an ancient β-defensin fold that is found in diverse families of endogenous and venom polypeptides dedicated to host defense. Crotamine is unique among several classes of bioactive peptides because it possesses both cell penetrating and antimicrobial activities and selective biological action toward some cell types at a given cell cycle phase. Because it can rapidly and efficiently translocate into actively proliferating cells, crotamine is being investigated for labeling highly replicating cells and for use as a chemotherapeutic adjuvant. Peptides derived from crotamine, nucleolar targeting peptides (NrTPs), have been designed and are being studied. NrTPs retain some crotamine properties, such as efficient cellular uptake and preferential nuclear localization whereas they improve upon other properties. For example, NrTPs are smaller than crotamine, show higher preferential nucleolar localization, and better facilitate ZIP-code localization of therapeutic proteins.

Transcriptome Analysis in Venom Gland of the Predatory Giant Ant Dinoponera quadriceps: Insights into the Polypeptide Toxin Arsenal of Hymenopterans

Background Dinoponera quadriceps is a predatory giant ant that inhabits the Neotropical region and subdues its prey (insects) with stings that deliver a toxic cocktail of molecules. Human accidents occasionally occur and cause local pain and systemic symptoms. A comprehensive study of the D. quadriceps venom gland transcriptome is required to advance our knowledge about the toxin repertoire of the giant ant venom and to understand the physiopathological basis of Hymenoptera envenomation. Results We conducted a transcriptome analysis of a cDNA library from the D. quadriceps venom gland with Sanger sequencing in combination with whole-transcriptome shotgun deep sequencing. From the cDNA library, a total of 420 independent clones were analyzed. Although the proportion of dinoponeratoxin isoform precursors was high, the first giant ant venom inhibitor cysteine-knot (ICK) toxin was found. The deep next generation sequencing yielded a total of 2,514,767 raw reads that were assembled into 18,546 contigs. A BLAST search of the assembled contigs against non-redundant and Swiss-Prot databases showed that 6,463 contigs corresponded to BLASTx hits and indicated an interesting diversity of transcripts related to venom gene expression. The majority of these venom-related sequences code for a major polypeptide core, which comprises venom allergens, lethal-like proteins and esterases, and a minor peptide framework composed of inter-specific structurally conserved cysteine-rich toxins. Both the cDNA library and deep sequencing yielded large proportions of contigs that showed no similarities with known sequences. Conclusions To our knowledge, this is the first report of the venom gland transcriptome of the New World giant ant D. quadriceps. The glandular venom system was dissected, and the toxin arsenal was revealed; this process brought to light novel sequences that included an ICK-folded toxins, allergen proteins, esterases (phospholipases and carboxylesterases), and lethal-like toxins. These findings contribute to the understanding of the ecology, behavior and venomics of hymenopterans.

A Novel Cell-Penetrating Peptide Sequence Derived by Structural Minimization of a Snake Toxin Exhibits Preferential Nucleolar Localization

Structural simplification of a 42-residue venom peptideby N-to-C-terminal splicing led to two sequences [YKQCHKKGGXKKGSG, where X = nil (1) or 6-aminohexanoyl (2)], both efficiently uptaken by HeLa cells and, most interestingly, specifically localized at the nucleolus. Retro-2 was uptaken less efficiently, but a single (His --> Ile) replacement recovered the translocation ability. None of the peptides were cytotoxic up to 100 microM. Enantio-1 did not translocate, suggesting that peptide uptake was receptor-mediated.

Crotamine toxicity and efficacy in mouse models of melanoma

Objectives: Selective anticancer cell activity for both cell-penetrating and cationic antimicrobial peptides has previously been reported. As crotamine possesses activities similar to both of these, this study investigates crotamines anticancer toxicity in vitro and in vivo. Research design and methods: In vitro cancer cell viability was evaluated after treatment with 1 and 5 μg/ml of crotamine. In vivo crotamine cytotoxic effects in C57Bl/6J mice bearing B16-F10 primary cutaneous melanoma were tested, with two groups each containing 35 mice. The crotamine-treated group received 1 μg/day of crotamine per animal, subcutaneously which was well tolerated; the untreated group received a placebo. Results: Crotamine at 5 μg/ml was lethal to B16-F10, Mia PaCa-2 and SK-Mel-28 cells and inoffensive to normal cells. In vivo crotamine treatment over 21 days significantly delayed tumor implantation, inhibited tumor growth and prolonged the lifespan of the mice. Mice in the crotamine-treated group survived at significantly higher rates (n = 30/35) than those in the untreated group (n = 7/35) (significance calculated with the Kaplan–Meier estimator). The average tumor weight in the untreated group was 4.60 g but was only about 0.27 g in the crotamine-treated mice, if detectable. Conclusions: These data warrant further exploration of crotamine as a tumor inhibition compound.

Biological versatility of crotamine – a cationic peptide from the venom of a South American rattlesnake

Importance of the field: Molecules isolated from animals, insects, plants or microorganisms can provide prototypes for design of biopharmaceutical products. Some venom toxins and their derivatives are used in medicine, while others provide templates for development of new drugs. Areas covered in this review: The mild toxin, crotamine, a small basic low-molecular-weight polypeptide purified from the venom of a South American rattlesnake, Crotalus durissus terrificus. Crotamine was discovered more than 50 years ago and only in the past six years has its exceptional biological versatility been demonstrated. Particularly, its cell-penetrating ability, which allows crotamine to cross cell membranes and to accumulate in the nucleus; its use for intracellular vesicle tracking and as a cell cycle marker and its capability for delivering DNA into replicating mammalian cells. Both antimicrobial action and potential selective antitumor activity of crotamine have also been found. What the reader will gain: Multidisciplinary approaches and pathways of discovery placed crotamine in a rare category of versatile biomolecules, in which concentration, molecular target preference, structural ancestry and specificity toward biological membranes play an integral role. Take home message: Crotamine is a druggable peptide with high potential for use as an imaging agent for detecting dividing cells, for intracellular delivery of hydrophilic biomolecules, and as an alternative chemotherapeutic compound against aggressive types of cancer.

cDNA cloning and 1.75 Å crystal structure determination of PPL2, an endochitinase and N-acetylglucosamine-binding hemagglutinin from Parkia platycephala seeds

Parkia platycephala lectin 2 was purified from Parkia platycephala (Leguminosae, Mimosoideae) seeds by affinity chromatography and RP‐HPLC. Equilibrium sedimentation and MS showed that Parkia platycephala lectin 2 is a nonglycosylated monomeric protein of molecular mass 29 407 ± 15 Da, which contains six cysteine residues engaged in the formation of three intramolecular disulfide bonds. Parkia platycephala lectin 2 agglutinated rabbit erythrocytes, and this activity was specifically inhibited by N‐acetylglucosamine. In addition, Parkia platycephala lectin 2 hydrolyzed β(1–4) glycosidic bonds linking 2‐acetoamido‐2‐deoxy‐β‐d‐glucopyranose units in chitin. The full‐length amino acid sequence of Parkia platycephala lectin 2, determined by N‐terminal sequencing and cDNA cloning, and its three‐dimensional structure, established by X‐ray crystallography at 1.75 Å resolution, showed that Parkia platycephala lectin 2 is homologous to endochitinases of the glycosyl hydrolase family 18, which share the (βα)8 barrel topology harboring the catalytic residues Asp125, Glu127, and Tyr182.

Crotacetin, a Novel Snake Venom C-Type Lectin Homolog of Convulxin, Exhibits an Unpredictable Antimicrobial Activity

Snake venom (sv) C-type lectins encompass a group of hemorrhagic toxins that are capable of interfering with blood stasis. A very well-studied svC-type lectin is the heterodimeric toxin, convulxin (CVX), from the venom of South American rattlesnake Crotalus durissus terrificus. CVX is able to activate platelets and induce their aggregation by acting via p62/GPVI collagen receptor. By using polymerase chain reaction homology screening, we have cloned several cDNA precursors of CVX subunit homologs. One of them, named crotacetin (CTC) β-subunit, predicts a polypeptide with a topology very similar to the tridimensional conformations of other subunits of CVX-like snake toxins, as determined by computational analysis. Using gel permeation and reverse-phase high-performance liquid chromatography, CTC was purified from C. durissus venoms. CTC can be isolated from the venom of several C. durissus subspecies, but its quantitative predominance is in the venom of C. durissus cascavella. Functional analysis indicates that CTC induces platelet aggregation, and, importantly, exhibits an antimicrobial activity against Gram-positive and-negative bacteria, comparable with CVX.