RK1, the first very short peptide from Buthus occitanus tunetanus inhibits tumor cell migration, proliferation and angiogenesis.

International audienceScorpion toxins have been the subject of many studies which explore their pharmacological potential toward diverse molecular targets, known to monitor key mechanisms in cancer such as proliferation, migration and angiogenesis. The few peptides from scorpion venom that have an anti-tumor effect are generally cytotoxic. Herein, we present the first description of a short 14 amino acid peptide (called RK1), purified from the venom of Buthus occitanus tunetanus, with the particular capabilities, among different other scorpion peptides, to inhibit cell proliferation, migration and angiogenesis of U87 (Glioblastoma) and IGR39 (Melanoma). Moreover, RK1 is a first peptide derived from scorpion venom exhibiting a potential anti-tumoral activity with no manifest toxicity. Our results suggest that, in terms of its primary structure, RK1 is unique compared to a variety of known peptides purified from scorpion venoms. In addition, RK1 is the first natural peptide able to abolish completely the proliferation of cancer cells. The Chicken chorioallantoic membrane model revealed that RK1 strongly inhibits ex-vivo vascular growth. RK1 could open new perspective for the pharmaceutical application of short scorpion venom peptides in anticancer activity and may represent the first member of a new group of scorpion peptides

Characterization of Kbot21 Reveals Novel Side Chain Interactions of Scorpion Toxins Inhibiting Voltage-Gated Potassium Channels.

Scorpion toxins are important pharmacological tools for probing the physiological roles of ion channels which are involved in many physiological processes and as such have significant therapeutic potential. The discovery of new scorpion toxins with different specificities and affinities is needed to further characterize the physiology of ion channels. In this regard, a new short polypeptide called Kbot21 has been purified to homogeneity from the venom of Buthus occitanus tunetanus scorpion. Kbot21 is structurally related to BmBKTx1 from the venom of the Asian scorpion Buthus martensii Karsch. These two toxins differ by only two residues at position 13 (R /V) and 24 (D/N).Despite their very similar sequences, Kbot21 and BmBKTx1 differ in their electrophysiological activities. Kbot21 targets KV channel subtypes whereas BmBKTx1 is active on both big conductance (BK) and small conductance (SK) Ca2+-activated K+ channel subtypes, but has no effects on Kv channel subtypes. The docking model of Kbot21 with the Kv1.2 channel shows that the D24 and R13 side-chain of Kbot21 are critical for its interaction with KV channels

Kbot55, purified from Buthus occitanus tunetanus venom, represents the first member of a novel α-KTx subfamily

Kbot55 is a 39 amino acid peptide isolated from the venom of the Tunisian scorpion Buthus occitanus tunetanus. This peptide is cross-linked by 3 disulfide bridges and has a molecular mass of 4128.65Da. Kbot55 is very low represented in the venom and thus represents a challenge for biochemical characterization. In this study, Kbot55 has been subjected to a screening on ion channels expressed in Xenopus laevis oocytes. It was found that Kbot55 targets voltage-gated potassium channels with high affinity. Kbot55 shows very low amino acid identity with other scorpion potassium toxins and therefore was considered a bona fide novel type of scorpion toxin. Sequence alignment analysis indicated that Kbot55 is the first representative of the new α-Ktx31 subfamily and therefore was classified as α-Ktx31.1.publisher: Elsevier articletitle: Kbot55, purified from Buthus occitanus tunetanus venom, represents the first member of a novel α-KTx subfamily journaltitle: Peptides articlelink: http://dx.doi.org/10.1016/j.peptides.2015.05.015 content_type: article copyright: © 2015 Elsevier Inc. All rights reserved.status: publishe

Kbot55, purified from Buthus occitanus tunetanus venom, represents the first member of a novel alpha-KTx subfamily

Invertebrate Neuropeptide Conference 2015 (INC2015)., Bagan, MYANMAR, 2015International audienceKbot55 is a 39 amino acid peptide isolated from the venom of the Tunisian scorpion Buthus occitanus tunetanus. This peptide is cross-linked by 3 disulfide bridges and has a molecular mass of 4128.65 Da. Kbot55 is very low represented in the venom and thus represents a challenge for biochemical characterization. In this study, Kbot55 has been subjected to a screening on ion channels expressed in Xenopus laevis oocytes. It was found that Kbot55 targets voltage-gated potassium channels with high affinity. Kbot55 shows very low amino acid identity with other scorpion potassium toxins and therefore was considered a bona fide novel type of scorpion toxin. Sequence alignment analysis indicated that Kbot55 is the first representative of the new alpha-Ktx31 subfamily and therefore was classified as alpha-Ktx31.1. (C) 2015 Elsevier Inc. All rights reserved

RK, the first scorpion peptide with dual disintegrin activity on α1β1 and αvβ3 integrins

International audiencethe first scorpion peptide with dual disintegrin activity on α1β1 and αvβ3 integrins. Abstract: Scorpion peptides are well known for their pharmaceutical potential on different targets. These include mainly the ion channels which were found to be highly expressed in many diseases, including cancer, auto-immune pathologies and Alzheimer. So far, however, the disintegrin activity had only been characterized for snake venom molecules. Herein, we present the first short peptide, purified from the venom of Buthus occitanus tunetanus, (termed RK) able to inhibit the cell adhesion of Glioblastoma, Melanoma and Rat pheochromocytoma to different extracellular matrix (ECM) receptors. Anti-integrin antibody assay suggests that RK interacts with both α1β1 and αvβ3 with a more pronounced effect for the former. The examination of the primary structure of RK suggests the involvement of two motifs: KSS, analogue to KTS which was characterized for α1β1 Snake venom disintegrins, and ECD, analogue to RGD which was found to be active on αvβ3. To assess their roles in the disintegrin activity of RK, we conducted a computational analysis. The molecular docking study shows that RK involves mainly two segments to interact with the α1β1 integrin, but the peptide does not implicate the KSS motif in the interaction. The molecular modeling study, suggests the key contribution of the ECD segment in the interaction with αvβ3 integrin

Electrophysiological charaterisation of Kbot21.

<p><b>(A)</b> Current traces at different voltages in control (left panel) and in the presence of 100 nM toxin (right panel). <b>(B)</b> The plot shows the voltage-current relationship in control conditions and after addition of 100 nM Kbot21. The potentials were tested in a range from -80 mV to +70 mV. Closed circles show the V1/2 in control and the open circles the addition of 100 nM Kbot21. <b>(C)</b> Representative experiment of the time course of Kv1.6 current inhibition with Kbot21 (500 nM) and the reversibility hereof. Control (closed squares); washin (closed squares + black bar); washout (open squares). Blockage occurred rapidly, and binding was reversible upon washout. <b>(D)</b>The plot shows the concentration-response curve for Kbot21 on Kv1.6 channels obtained by plotting the percentage blocked current as a function of increasing toxin concentrations. All data represent at least 3 independent experiments (n ≥ 3) and are presented as mean ± standard error.</p

Molecular modelling.

<p><b>(A)</b> the 3D model of Kbot21 generated from the NMR structure of BmBKTx1. The amino acids of the functional dyad, K21 and Y30, and the different residues between the two peptides at positions 13 and 24 are shown. <b>(B)</b> The interaction mode of Kbot21 on the Kv1.2 potassium channel as predicted from protein-protein docking study. <b>(C)</b> The Kv2.1 and Kv1.4 potassium channels subtype structure model. Only two opposed chains are represented for clarity. The residues K360 and A366 for Kv2.1 and K531 for Kv1.4 are suggested being responsible for the ineffectiveness of Kbot21 on these two potassium channel subtypes.</p

Purification of Kbot21 from scorpion <i>Buthus occitanus tunetanus</i> venom.

<p><b>(A)</b> Chromatography of fraction BotG50 on semi preparative C8 reverse phase HPLC column. <b>(B)</b> Chromatography of fraction B1on C18-RP-HPLC, B’1 was collected at 29min. <b>(C)</b> Kbot21 was purified from the fraction B’1 by C18-RP-HPLC. It is collected at 21min.</p

A multiple sequence alignment of the pore domain segments of the potassium channels Kv1.1, Kv1.2, Kv1.3, Kv1.4, Kv1.6 and Kv2.1 using 3D-Expresso program [43].

<p>Conserved blocks are coloured in blue and the key residues for the interaction of Kbot21 with the channel are coloured in red boxes.</p