Scorpion venoms are known as a rich mixture of components, including peptides that can interact with different ion channels, particularly voltage-gated potassium channels (Kv), calcium channels (Cav) ...and sodium channels (Nav), essential membrane proteins for various physiological functions in organisms. The present work aimed to characterize the modulation of hNa+-channels by Tst1, a peptide purified from the venom of Tityus stigmurus, using whole-cell patch clamp. Tst1 at 100 nM provoked current inhibition in Nav 1.3 (85.23%), Nav 1.2 (67.26%) and Nav 1.4 (63.43%), while Nav 1.1, 1.5, 1.6, and 1.7 were not significantly affected. Tst1 also shifted the voltage of activation and steady-state inactivation to more hyperpolarized states and altered the recovery from inactivation of the channels, reducing repetitive firing of cells, which was more effective in Nav 1.3. Tst1 also demonstrated that the effect on Nav 1.3 is dose-dependent, with an IC50 of 8.79 nM. Taken together, these results confirmed that Tst1, the first Tityus stigmurus NaScTx assayed in relation to Nav channels, is a β-toxin, as was previously suggested due to its amino acid sequence.
First β-toxin purified from the venom of Tityus stigmurus scorpion broadly characterized in hNa+-channels.
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•First Tityus stigmurus β-toxin tested on different subtypes of voltage-gated sodium channels (Nav 1.1–1.7).•Tst1 alters the kinetic of activation and steady-state inactivation (SSI) of different Nav isoforms.•On Nav 1.3, Tst1 significantly inhibited (about 85%) the current and shifted the activation in −35 mV.•Tityus scorpion toxin described until now that highly affected Nav 1.3 at 100 nM in HEK cells.•Tst1 had an IC50 of 8.79 nM on Nav 1.3.
Scorpionism is a public health problem in Brazil, and Tityus serrulatus (Ts) is primarily responsible for severe accidents. The main toxic components of Ts venom are low-molecular-weight neurotoxins; ...however, the venom also contains poorly characterized high-molecular-weight enzymes. Hyaluronidase is one such enzyme that has been poorly characterized.
We examined clones from a cDNA library of the Ts venom gland and described two novel isoforms of hyaluronidase, TsHyal-1 and TsHyal-2. The isoforms are 83% identical, and alignment of their predicted amino acid sequences with other hyaluronidases showed conserved residues between evolutionarily distant organisms. We performed gel filtration followed by reversed-phase chromatography to purify native hyaluronidase from Ts venom. Purified native Ts hyaluronidase was used to produce anti-hyaluronidase serum in rabbits. As little as 0.94 µl of anti-hyaluronidase serum neutralized 1 LD50 (13.2 µg) of Ts venom hyaluronidase activity in vitro. In vivo neutralization assays showed that 121.6 µl of anti-hyaluronidase serum inhibited mouse death 100%, whereas 60.8 µl and 15.2 µl of serum delayed mouse death. Inhibition of death was also achieved by using the hyaluronidase pharmacological inhibitor aristolochic acid. Addition of native Ts hyaluronidase (0.418 µg) to pre-neutralized Ts venom (13.2 µg venom+0.94 µl anti-hyaluronidase serum) reversed mouse survival. We used the SPOT method to map TsHyal-1 and TsHyal-2 epitopes. More peptides were recognized by anti-hyaluronidase serum in TsHyal-1 than in TsHyal-2. Epitopes common to both isoforms included active site residues.
Hyaluronidase inhibition and immunoneutralization reduced the toxic effects of Ts venom. Our results have implications in scorpionism therapy and challenge the notion that only neurotoxins are important to the envenoming process.
•A previously undescribed peptide (Cl13) was obtained from C. limpidus scorpion venom.•The amino acid sequence and function were determined.•It contains 66 amino acids, 4 disulfide bonds and ...functions as a β-SCTx.•Cl13 affects mainly the human voltage dependent sodium channels 1.4, 1.5 and 1.6.•Antibody fragments specific for Cll1m and Cll2 do not recognize Cl13.
A previously undescribed toxic peptide named Cl13 was purified from the venom of the Mexican scorpion Centruroides limpidus. It contains 66 amino acid residues, including four disulfide bonds. The physiological effects assayed in 7 different subtypes of voltage gated Na+-channels, showed that it belongs to the β-scorpion toxin type. The most notorious effects were observed in subtypes Nav1.4, Nav1.5 and Nav1.6. Although having important sequence similarities with two other lethal toxins from this scorpion species (Cll1m and Cll2), the recently developed single chain antibody fragments (scFv) of human origin were not capable of protecting against Cl13. At the amino acid sequence level, in 3 stretches of peptide Cl13 (positions 7–9, 30–38 and 62–66) some differences with respect to other similar toxins are observed. Some of these differences coincide with contact points with the human antibody fragments.
Scorpionism is responsible for most accidents involving venomous animals in Brazil, which leads to severe symptoms that can evolve to death. Scorpion venoms consist of complexes cocktails, including ...peptides, proteins, and non-protein compounds, making separation and purification procedures extremely difficult and time-consuming. Scorpion toxins target different biological systems and can be used in basic science, for clinical, and biotechnological applications. This study is the first to explore the venom content of the unexplored scorpion species
, which inhabits exclusively the northernmost state of Brazil, named Roraima, and southern region of Guyana. Here, we pioneer the fractionation of the
venom and isolated and characterized a novel scorpion beta-neurotoxin, designated Rc1, and a monomeric hyaluronidase.
venom and Rc1 (6,882 Da) demonstrated pro-inflammatory activities
and a nociceptive response
. Moreover, Rc1 toxin showed specificity for activating Na
1.4, Na
1.6, and BgNa
1 voltage-gated ion channels. This study also represents a new perspective for the treatment of envenomings in Roraima, since the Brazilian scorpion and arachnid antivenoms were not able to recognize
venom and its fractions (with exception of hyaluronidase). Our work provides useful insights for the first understanding of the painful sting and pro-inflammatory effects associated with
envenomings.
This communication describes the general characteristics of the venom from the Brazilian scorpion Tityus fasciolatus, which is an endemic species found in the central Brazil (States of Goiás and ...Minas Gerais), being responsible for sting accidents in this area. The soluble venom obtained from this scorpion is toxic to mice being the LD50 is 2.984 mg/kg (subcutaneally). SDS-PAGE of the soluble venom resulted in 10 fractions ranged in size from 6 to 10–80 kDa. Sheep were employed for anti-T. fasciolatus venom serum production. Western blotting analysis showed that most of these venom proteins are immunogenic. T. fasciolatus anti-venom revealed consistent cross-reactivity with venom antigens from Tityus serrulatus. Using known primers for T. serrulatus toxins, we have identified three toxins sequences from T. fasciolatus venom. Linear epitopes of these toxins were localized and fifty-five overlapping pentadecapeptides covering complete amino acid sequence of the three toxins were synthesized in cellulose membrane (spot-synthesis technique). The epitopes were located on the 3D structures and some important residues for structure/function were identified.
•The Tityus fasciolatus and Tityus serrulatus venoms are molecular and immunogically similar.•We obtained three new sequences of T. fasciolatus toxins.•The T. fasciolatus can be considered medical importance as it has a very toxic venom.•The commercial scorpion serum may be used with caution for the T. fasciolatus.•The mapped epitopes have important defined residues for structure/function.
The interaction of insect-selective scorpion depressant β-toxins (LqhIT2 and Lqh-dprIT3 from Leiurus quinquestriatus hebraeus) with the Blattella germanica sodium channel, BgNav1-1a, was investigated ...using site-directed mutagenesis, electrophysiological analyses, and structural modeling. Focusing on the pharmacologically defined binding site-4 of scorpion β-toxins at the voltage-sensing domain II (VSD-II), we found that charge neutralization of D802 in VSD-II greatly enhanced the channel sensitivity to Lqh-dprIT3. This was consistent with the high sensitivity of the splice variant BgNav2-1, bearing G802, to Lqh-dprIT3, and low sensitivity of BgNav2-1 mutant, G802D, to the toxin. Further mutational and electrophysiological analyses revealed that the sensitivity of the WT = D802E < D802G < D802A < D802K channel mutants to Lqh-dprIT3 correlated with the depolarizing shifts of activation in toxin-free channels. However, the sensitivity of single mutants involving IIS4 basic residues (K4E = WT << R1E < R2E < R3E) or double mutants (D802K = K4E/D802K = R3E/D802K > R2E/D802K > R1E/D802K > WT) did not correlate with the activation shifts. Using the cryo-EM structure of the Periplaneta americana channel, NavPaS, as a template and the crystal structure of LqhIT2, we constructed structural models of LqhIT2 and Lqh-dprIT3-c in complex with BgNav1-1a. These models along with the mutational analysis suggest that depressant toxins approach the salt-bridge between R1 and D802 at VSD-II to form contacts with linkers IIS1-S2, IIS3-S4, IIIP5-P1 and IIIP2-S6. Elimination of this salt-bridge enables deeper penetration of the toxin into a VSD-II gorge to form new contacts with the channel, leading to increased channel sensitivity to Lqh-dprIT3.
Scorpion Pryke, Louise M
2016., 2016, 2016-06-15, Letnik:
159
eBook
From the back cover: "From the dawn of human civilization the scorpion has been a threatening figure in our imaginations--poisonous, precise and deadly quiet--but their bad reputation has ...overshadowed many exceptional qualities. Older than dinosaurs, these small arthropods have survived for hundreds of millions of years with very few changes to their form, and they have populated every continent--with the exception of Antarctica. Although humans and scorpions have coexisted for thousands of years, the image of the scorpion retains a sense of danger and mystery. Throughout our existence scorpions have served as powerful cultural and religious symbols--sometimes as menacing foes, other times as protectors. From the Egyptian goddess Serket to Zodiac astrology to folk medicine, Scorpion is a fascinating tour that includes ancient warrior deities, the American Civil War and the markets of Southeast Asia. Scorpion is a richly illustrated homage to one of earth's oldest residents."
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•Excitation wavelength-independent fluorescence spectra of scorpion exoskeleton within the visible light range.•Additional excitation wavelength-independent fluorescence spectra of ...scorpion exoskeleton within the ultraviolet light range.•Fluorescence heterogeneity in different segments of adult scorpions under different ultraviolet light ranges.•Fluorescence heterogeneity-dependent fluorescence recovery speed of scorpion exoskeleton.
Scorpion fluorescence under ultraviolet light is a well-known phenomenon, but its features under excitation in the UVA, UVB and UVC bands have not been characterized. Systematic fluorescence characterization revealed indistinguishable fluorescence spectra with a peak wavelength of 475 nm for whole exuviae from second-, third- and fifth-instar scorpions under different ultraviolet light ranges. In-depth investigations of the chelae, mesosoma, metasoma and telson of adult scorpions further indicated heterogeneity in the typical fluorescence spectrum within the visible light range and in the newly reported fluorescence spectrum with a peak wavelength of 320 nm within the ultraviolet light range, which both showed excitation wavelength-independent features. Dynamic fluorescence changes during the molting process of third-instar scorpions revealed the fluorescence heterogeneity-dependent recovery speed of scorpion exoskeletons. The typical fluorescence spectra of the molted chelae and telson rapidly recovered approximately 6 h after ecdysis under UVA light and approximately 36 h after ecdysis under UVB and UVC light. However, it took approximately 12 h and 24 h to obtain the typical fluorescence spectra of the molted metasoma and mesosoma, respectively, under UVA irradiation and 72 h to obtain the typical fluorescence spectra under UVB and UVC irradiation. The fluorescence heterogeneity-dependent fluorescence recovery of the scorpion exoskeleton was further confirmed by tissue section analysis of different segments from molting third-instar scorpions. These findings reveal novel scorpion fluorescence features and provide potential clues on the biological function of scorpion fluorescence.
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