Asian Scorpion Buthus Martensi Karsch Research Articles

Short‐chain peptides identification of scorpion Buthus martensi Karsch venom by employing high orthogonal 2D‐HPLC system and tandem mass spectrometry

Scorpion venom contains a considerable variety of neurotoxic peptides that can act on ionic channels. Here, we describe an orthogonal 2D-reversed phase/hydrophilic interaction chromatography system (RPLC/HILIC) and use it to separate short-chain peptides from Asian scorpion Buthus martensi Karsch (BmK) venom in a high throughput format. Due to its high orthogonality and efficiency, 18 homogenous peptides were purified and sequence identified by MS/MS with collision-induced dissociation. Among them, four peptides were discovered, which only have evidence at transcript-level, were first purified from crude venom in this study. Two peptides named BmKK2-b and Martentoxin-b were found the new cleaved chains of known BmKK2 and Martentoxin. In addition, two novel peptides named BmKK12 and BmKK16 in this paper were sequenced by de novo MS/MS, which we predict, are members of potassium channel toxin α-KTx 17 subfamily by homology to other known peptides found in the Swiss-Prot protein database.

Exploring the obscure profiles of pharmacological binding sites on voltage-gated sodium channels by BmK neurotoxins

Diverse subtypes of voltage-gated sodium channels (VGSCs) have been found throughout tissues of the brain, muscles and the heart. Neurotoxins extracted from the venom of the Asian scorpion Buthus martensi Karsch (BmK) act as sodium channel-specific modulators and have therefore been widely used to study VGSCs. α-type neurotoxins, named BmK I, BmK αIV and BmK abT, bind to receptor site-3 on VGSCs and can strongly prolong the inactivation phase of VGSCs. In contrast, β-type neurotoxins, named BmK AS, BmK AS-1, BmK IT and BmK IT2, occupy receptor site-4 on VGSCs and can suppress peak currents and hyperpolarize the activation kinetics of sodium channels. Accumulating evidence from binding assays of scorpion neurotoxins on VGSCs, however, indicate that pharmacological sensitivity of VGSC subtypes to different modulators is much more complex than that suggested by the simple α-type and β-type neurotoxin distinction. Exploring the mechanisms of possible dynamic interactions between site 3-/4-specific modulators and region- and/or species-specific subtypes of VGSCs would therefore greatly expand our understanding of the physiological and pharmacological properties of diverse VGSCs. In this review, we discuss the pharmacological and structural diversity of VGSCs as revealed by studies exploring the binding properties and cross-competitive binding of site 3- or site 4-specific modulators in VGSC subtypes in synaptosomes from distinct tissues of diverse species.

Effects of BmKNJX11, A Bioactive Polypeptide Purified from Buthus martensi Karsch, on Sodium Channels in Rat Dorsal Root Ganglion Neurons

A long-chain polypeptide BmKNJX11 was purified from the venom of Asian scorpion Buthus martensi Karsch (BmK) by a combination of gel filtration, ion-exchange chromatography, and reverse-phase high-performance liquid chromatography. The molecular mass was found to be 7036.85 Da by electrospray ionization mass spectrometry. The first 15 N-terminal amino acid sequence of BmKNJX11 was determined to be GRDAY IADSE NCTYT by Edman degradation. With whole cell recording, BmKNJX11 inhibited tetrodotoxin-sensitive voltage-gated sodium channels (TTX-S VGSC) in freshly isolated rat dorsal root ganglion (DRG) neurons in a concentration- and voltage-dependent manner. At a concentration of 40 μg/ml BmKNJX11 lowered the activation threshold and produced negative shifting of TTX-S sodium current (I Na) activation curve. In addition, BmKNJX11 induced shifting of the steady-state inactivation curve to the left, delayed the recovery of TTX-S I Na from inactivation, and also reduced the fraction of available sodium channels. These results suggested that BmKNJX11 might exert effects on VGSC by binding to a specific site. Considering that TTX-S VGSC expressed in DRG neurons play a critical role in nociceptive transmission, the interaction of BmKNJX11 with TTX-S VGSC might lead to a change in excitability of nociceptive afferent fibers, which may be involved in the observed peripheral pain expression.

Turning a Scorpion Toxin into an Antitumor Miniprotein

The oncoproteins MDM2 and MDMX negatively regulate the activity and stability of the tumor suppressor protein p53 and are important molecular targets for anticancer therapy. Grafting four residues of p53 critical for MDM2/MDMX binding to the N-terminal alpha-helix of BmBKTx1, a scorpion toxin isolated from the venom of the Asian scorpion Buthus martensi Karsch, converts the miniature protein into an effective inhibitor of p53 interactions with MDM2 and MDMX. Additional mutations enable the 27-residue miniprotein inhibitor to traverse the cell membrane and selectively kill tumor cells in a p53 dependent manner.

Anti-nociceptive effects induced by intrathecal injection of BmK AS, a polypeptide from the venom of Chinese-scorpion Buthus martensi Karsch, in rat formalin test

Aim of the study Asian scorpion Buthus martensi Karsch (BmK) is widely used to treat neurological symptoms, especially chronic pain, in traditional Chinese medicine for thousands of years. BmK AS, a polypeptide from BmK venom, could produce peripheral potent anti-nociceptive effects in rats. In the present study, spinal anti-nociceptive effects of BmK AS were investigated in rat formalin test. Materials and Methods Spinal anti-nociceptive activity of BmK AS was studied using formalin test in rats. BmK AS in doses of 0.02, 0.1 and 0.5 μg was administered intrathecally before formalin injection 10 min. The suppression by intrathecal injection of BmK AS on formalin-induced spontaneous nociceptive behaviors and spinal c-Fos expression were investigated. Results Intrathecal injection of BmK AS markedly reduced formalin-evoked biphasic spontaneous nociceptive behaviors in a dose-dependent manner. Formalin-induced c-Fos expression could be dose-dependently inhibited by BmK AS in superficial (I–II), the nucleus proprius (III and IV) and deep (V–VI) dorsal horn laminae, but not in the ventral gray laminae (VII–X) of lumbar spinal cord. The suppression by BmK AS on c-Fos expression in superficial laminaes was much stronger than that in deep laminaes. Conclusion The present study demonstrates that BmK AS is capable of producing remarkable anti-nociceptive effects not only in periphery but also in spinal cord.

BmBKTx1, a Novel Ca2+-activated K+ Channel Blocker Purified from the Asian Scorpion Buthus martensi Karsch

BmBKTx1 is a novel short chain toxin purified from the venom of the Asian scorpion Buthus martensi Karsch. It is composed of 31 residues and is structurally related to SK toxins. However, when tested on the cloned rat SK2 channel, it only partially inhibited rSK2 currents, even at a concentration of 1 microm. To screen for other possible targets, BmBKTx1 was then tested on isolated metathoracic dorsal unpaired median neurons of Locusta migratoria, in which a wide variety of ion channels are expressed. The results suggested that BmBKTx1 could specifically block voltage-gated Ca(2+)-activated K(+) currents (BK-type). This was confirmed by testing the BmBKTx1 effect on the alpha subunits of BK channels of the cockroach (pSlo), fruit fly (dSlo), and human (hSlo), heterologously expressed in HEK293 cells. The IC(50) for channel blocking by BmBKTx1 was 82 nm for pSlo and 194 nm for dSlo. Interestingly, BmBKTx1 hardly affected hSlo currents, even at concentrations as high as 10 microm, suggesting that the toxin might be insect specific. In contrast to most other scorpion BK blockers that also act on the Kv1.3 channel, BmBKTx1 did not affect this channel as well as other Kv channels. These results show that BmBKTx1 is a novel kind of blocker of BK-type Ca(2+)-activated K(+) channels. As the first reported toxin active on the Drosophila Slo channel dSlo, it will also greatly facilitate studying the physiological role of BK channels in this model organism.

Purification and pharmacological characterization of BmKK2 (α-KTx 14.2), a novel potassium channel-blocking peptide, from the venom of Asian scorpion Buthus martensi Karsch

BmKK2 (α-KTx 14.2) is one of the novel short-chain peptides found in molecular cloning of a venom gland cDNA library from Asian scorpion Buthus martensi Karsch. Based upon its amino acid sequence, the peptide was proposed to adopt a classical α/β-scaffold for α-KTxs. In the present study, we purified BmKK2 from the venom of B. martensi Karsch, and investigated its action on voltage-dependent K + currents in dissociated hippocampal neurons from neonatal rats. BmKK2 (10–100 μM) selectively inhibited the delayed rectifier K + current, but did not affect the fast transient K + current. The inhibition of BmKK2 on the delayed rectifier K + current was reversible and voltage-independent. The peptide did not affect the steady-state activation of the current, but caused a depolarizing shift (about 9 mV) of its steady-state inactivation curve. The results demonstrate that BmKK2 is a novel K + channel-blocking scorpion peptide.

BmKK4, a novel toxin from the venom of Asian scorpion Buthus martensi Karsch, inhibits potassium currents in rat hippocampal neurons in vitro

A novel short-chain peptide BmKK4 was isolated from the venom of Asian scorpion Buthus martensi Karsch. It is composed of 30 amino acids including six cysteine residues, and shares less than 25% sequence identity with the known α-KTx toxins. The action of BmKK4 on voltage-dependent potassium currents was examined in acutely dissociated hippocampal neurons of rat. BmKK4 (10–100 μM) inhibited both the delayed rectifier and fast transient potassium current in concentration-dependent manners. The inhibition was reversible and voltage-independent. BmKK4 caused a depolarizing shift (about 10 mV) of the steady-state activation curve of the currents, without changing their steady-state inactivation behavior. The unique amino acid sequence and electrophysiological effects suggest that BmKK4 represent a new subfamily of potassium channel toxins.

Exploration of the functional site of a scorpion alpha-like toxin by site-directed mutagenesis.

Scorpion alpha-neurotoxins can be classified into distinct subgroups according to their sequence and pharmacological properties. Using toxicity tests, binding studies, and electrophysiological recordings, BmK M1, a toxin from the Asian scorpion Buthus martensi Karsch, was experimentally identified as an alpha-like toxin. Being the first alpha-like toxin available in a recombinant form, BmK M1 was then modified by site-directed mutagenesis for investigation of the molecular basis of its activity. The results suggested a functional site which protrudes from the molecular scaffold as a unique tertiary arrangement, constituted by the five-residue reverse turn 8-12 and the C-terminal segment. The C-terminal basic residues Lys62 and His64 together with Lys8 in the turn, which are critical for the bioactivities, may directly interact with the receptor site on the sodium channel. Residues Asn11 and Arg58, indispensable for the activities, are mainly responsible for stabilizing the distinct conformation of the putative bioactive site. Among others, His10 and His64 seem to be involved in the preference of BmK M1 for phylogenetically distinct target sites. The comparison of BmK M1 with Aah2 (classical alpha-toxin) and Lqh(alpha)IT (alpha-insect toxin) showed that the specific orientation of the C-terminus mediated by the reverse turn might be relevant to the preference of alpha-toxin subgroups for phylogenetically distinct yet closely related receptor sites. The Y5G mutation indicated the "conserved hydrophobic surface" might be structurally important for stabilizing the beta-sheet in the alpha/beta-scaffold. The observations in this work shed light on the nature and roles of the residues possibly involved in the biological activity of a scorpion alpha-like toxin.

Characterization of Na + currents in isolated dorsal unpaired median neurons of Locusta migratoria and effect of the alpha-like scorpion toxin BmK M1

A primary cell culture was developed for efferent dorsal unpaired median (DUM) neurons of the locust. The isolated somata were able to generate Tetrodotoxin (TTX)-sensitive action potentials in vitro. The α-like scorpion toxin BmK M1, from the Asian scorpion Buthus martensi Karsch, prolonged the duration of the action potential up to 50 times. To investigate the mechanism of action of BmK M1, the TTX-sensitive voltage gated Na + currents were studied in detail using the whole cell patch clamp technique. BmK M1 slowed down and partially inhibited the inactivation of the TTX-sensitive Na + current in a dose dependent manner (EC50=326.8±34.5 nM). Voltage and time dependence of the Na + current were described in terms of the Hodgkin–Huxley model and compared in control conditions and in the presence of 500 nM BmK M1. The BmK M1 shifted steady state inactivation by 10.8 mV to less negative potentials. The steady state activation was shifted by 5.5 mV to more negative potentials, making the activation window larger. Moreover, BmK M1 increased the fast time constant of inactivation, leaving the activation time constant unchanged. In summary, BmK M1 primarily affected the inactivation parameters of the voltage gated Na + current in isolated locust DUM neurons.

Molecular characterization of an anti-epilepsy peptide from the scorpion Buthus martensi Karsch.

For a long time Asian scorpion Buthus martensi Karsch (BmK) has been used in Chinese traditional medicine to cure many diseases of nervous system. Here we report the purification and characterization of a pharmacologically active neurotoxin from the scorpion BmK. This toxin had little toxicity in mice and insects but was found to have an anti-epilepsy effect in rats, and is thus named as BmK anti-epilepsy peptide (BmK AEP). Its amino-acid sequence was determined by lysylendopeptidase digestion, Edman degradation and mass spectrographic analysis. Based on the determined sequence, the gene coding for this peptide was also cloned and sequenced by the 3' and 5' RACE methods. It encodes a precursor of 85 amino-acid residues including a signal peptide of 21 residues, a mature peptide of 61 residues and three additional residues Gly-Lys-Lys at the C-terminus. The additional Gly sometimes followed by one or two basic residues is prerequisite for the amidation of its C-terminus. C-terminal amidation was also verified by the molecular-mass determination of BmK AEP. This anti-epilepsy peptide toxin shares homology with other depressant insect toxins. The remarkable difference between them was mainly focused at residues 6, 7 and 39; these residues might relate to the unique action of BmK AEP.