Isoform-specific effects of a novel BmK 11(2) peptide toxin on Na channels.

BmK 11(2) is a 7216Da polypeptide toxin purified from the venom of the scorpion Buthus martensii Karsch. Nanomolar concentrations of the toxin prolong amphibian nerve action potentials without attenuation of the amplitude. The pharmacological action of the toxin and its sequence similarity to other alpha-scorpion toxins suggest that BmK 11(2) selectively alters voltage-gated Na channels. In order to test whether BmK 11(2) preferentially modulates the gating or kinetics of certain channel isoforms, we applied BmK 11(2) to muscle, heart and neuronal Na channels. 100nM BmK 11(2) increased the peak current amplitude of skeletal muscle (micro1) and neuronal (N1E-115) Na currents by 40 and 20%, respectively, and reduced the cardiac Na (hH1) current by 15%. The toxin slowed current decay of all isoforms, most prominently in N1E-115 (tau(BmK)/tau(Control)=12), micro1 (11), and less so for hH1 (1.3). BmK 11(2) shifted the voltage dependence of activation of micro1 and N1E-115 currents. BmK 11(2) had no effect on steady-state inactivation, use-dependent availability, and the kinetics of entry into slowly recovering inactivated states.     

The binding of BmK abT,a unique neurotoxin,to mammal brain and insect Na(+) channels using biosensor

The binding properties of BmK abT (a novel neurotoxic polypeptide abT from Chinese scorpion Buthus martensi Karsch), a unique neurotoxin from Chinese scorpion, on mammal brain and insect sodium channels were investigated using the BIAcore assay. Results showed that BmK abT could bind to rat brain synaptosomes with an association rate constant of about 2.49 x 10(6) M(-1) s(-1) and a dissociation rate constant of about 1.57 x 10(-4) s(-1), and to Heliothis nerve cord synaptosomes with an association rate constant of about 1.21 x 10(7) M(-1) s(-1) and a dissociation rate constant of about 0.99 x 10(-3) s(-1). The binding of BmK abT to rat brain synaptosomes could be partially inhibited by increasing the membrane potential, but not by BmK AS (a novel active polypeptide AS from B. martensi Karsch), BmK IT2 (a depressant insect-selective toxin IT2 from B. martensi Karsch), and BmK I (an alpha-like anti-mammal toxin I from B. martensi Karsch). Binding was not modulated by veratridine. In addition, the binding of BmK abT to Heliothis nerve cord synaptosomes was significantly enhanced by increasing the membrane potential and veratridine concentration and was inhibited by BmK IT2, but not by BmK AS or BmK I. The results suggest that BmK abT binds to a distinct receptor site on mammal brain Na(+) channels and associates with a related site for depressant insect-selective toxins on insect sodium channels.     

基于毒素多肽BmK NaTx-13的全蝎质控工艺研究

目的 基于毒素多肽建立一种新型的全蝎质量检测工艺。方法 从东亚钳蝎毒液中分离得到了一种新型钠通道毒素BmK NaTx-13,制备并鉴定了BmK NaTx-13的特异性抗体,并通过竞争性ELISA法检测全蝎提取物中的BmK NaTx-13的含量。结果 建立的竞争性酶联免疫吸附法可快速检测全蝎提取物中的BmK NaTx-13的含量并呈现良好的浓度线性依赖。结论 该研究为全蝎质控提供了一种快速免疫检测方法,为提升全蝎入药质量标准提供了借鉴。      

Suppression by intrathecal BmK IT2 on rat spontaneous pain behaviors and spinal c-Fos expression induced by formalin

The central anti-nociception of BmK IT2, a sodium channel modulator from scorpion Buthus martensi Karsh (BmK) was investigated in this study. It was found that the formalin-induced rat spontaneous flinches and spinal c-Fos expression could be significantly suppressed by intrathecal BmK IT2 pre- or post-formalin injection in a dose-dependent manner. The time course of inhibitory effect exerted by intrathecal BmK IT2 on spontaneous flinches was longer in the pre-treatment group than in post-treatment group. This was consistent with the stronger suppression on spinal c-Fos expression exerted by intrathecal BmK IT2 pre-treatment. In addition, the suppression by intrathecal BmK IT2 on formalin-induced c-Fos expression in superficial laminae was more significant than that in deeper laminae. These results indicate that BmK IT2 can induce central anti-nociceptive response and might thus be a valuable molecular tool for the understanding of pain mechanisms.     

两种具有双功能活性蝎毒蛋白融合体的构建

目的首次报道利用东亚钳蝎镇痛抗肿瘤缬精甘肽-BmKAGAP产生两种不同的融合蛋白,目的是获得镇痛和抗肿瘤的双功能活性。方法融合蛋白是以嵌合毒素的形式进行构建,由三部分组成,包括促性腺激素释放激素(luteinizing hormone-releasing hormoneL,HRH),两种不同类型的柔性连接物,以及BmKAGAP。克隆编码两种融合蛋白的基因并在大肠杆菌中实现可溶性表达。通过金属离子螯合亲和层析和阳离子交换层析方法对融合蛋白分离纯化,采用小鼠醋酸扭体法和MTT法测定融合蛋白的镇痛活性与细胞抑制活性。结果融合蛋白在小鼠模型中体现出镇痛活性(rLHRH-Tag(His)AGAP>rTag(His)-LHRH-L8-AGAP>rBmKAGAP),同时对肝癌细胞株Hep3B具有细胞毒活性(rLHRH-Tag(His)-AGAP>rBmKAGAP>rTag(His)-LHRH-L8-AGAP)。结论得到优化的双功能融合蛋白候选者为嵌合毒素rLHRH-Tag(His)-AGAP。     

蝎毒素BmK M2的分离鉴定及其电生理活性研究

从东亚钳蝎蝎毒中分离鉴定出新型的Na⁺通道毒素,采用Sephadex-G-50分子筛、高效液相色谱、多肽指纹图谱及氨基酸测序等技术从野生东亚钳蝎毒液中分离鉴定了一种长链多肽毒素BmK M2,其相对分子质量为7 235.5,由64个氨基酸组成,包含4对二硫键。序列比对显示,BmK M2的序列与已发现的Na⁺通道毒素BmK M1、BmK M3、BmK M9等具有较高的序列和结构相似性,是一种潜在的新型Na⁺通道调节剂。全细胞膜片钳实验结果显示,BmK M2可显著增强电压门控Na⁺通道Nav1.7的激活,延迟Nav1.7的稳态失活及关闭状态失活,但对Nav1.8无活性。实验结果表明BmK M2可作为一种新型的Na⁺通道探针,用于Nav1.7结构功能研究以及靶向药物的开发。     

Fos expression in rat spinal cord induced by peripheral injection of BmK I, an alpha-like scorpion neurotoxin

In this paper, the central neuronal activities elicited by BmK I, a specific voltage-gated Na+ channel modulator, were examined by monitoring the c-Fos expression pattern of rat spinal cord. c-Fos protein in laminae I-II, V-VI, and VII-X could be detected at 0.5 h, increased steadily at 1 h, reached a peak at 2 h, and then decreased rapidly from 4 to 24 h after Bmk I was subcutaneously injected into the rat hind paw. However, c-Fos expression in laminae III-IV was activated to a peak at 0.5 h and then declined gradually from 0.5 to 24 h. Furthermore, c-Fos expression could be induced by BmK I in a dose-dependent manner. In addition, the increase of c-Fos expression in laminae I-II, V-VI, and VII-X induced by BmK I, and not in laminae III-IV, could be partially inhibited by systemic morphine in a dose-dependent manner. The results suggested that peripheral administration of BmK I could evoke a profound change of spinal neuronal activities manifested as specific patterns of c-Fos expression, which may be partially attributed to the selective modulation of BmK I on voltage-gated Na+ channels located in peripheral nociceptors.     

Modulation of BmKAS-1 and BmK1-3-2 to sodium channel in rat dorsal root ganglion neurons

Objective To investigate what effects BmKAS-1 (a polypeptide purified from the Chinese sc orpion Buthus martensi Karsch ［BmK］ and named as BmK activator of skeletal -muscle ryanodine receptor) and its upstream mixture BmK1-3-2 have on Na(+) c hannels in dorsal root ganglion (DRG) small diameter neurons.Methods The whole-cell patch-clamp technique was used to investigate the effects of BmKAS-1 and BmK1-3-2 on Na(+) current in rat small diameter DRG neurons.Results About 50% peak Na(+) current was suppressed by 10 μg/ml of BmK1- 3-2. 1.62 μg/ml of BmKAS-1 also blocked 50% peak Na(+) cu rrent, and there was an obvious dose-dependent relationship.Conclusion Both BmK1-3-2 and BmKAS-1 have a blocking effect on Na(+) channels, and this may one of the mechanisms for the analgetic effect of BmK1-3-2 and BmKAS-1.     

Activation of spinal ERK signaling pathway contributes to pain-related responses induced by scorpion Buthus martensi Karch venom

It has been demonstrated that spontaneous nociceptive behaviors, cutaneous hyperalgesia and paw edema can be induced by intraplantar injection of scorpion Buthus martensi Karch (BmK) venom in rats. In the present study, activation of spinal extracellular signal-regulated kinase (ERK) signaling pathway and its contribution to pain-related responses induced by scorpion BmK venom were investigated. It was found that ERK was activated not only in the superficial layers but also in deep layers of L4–L5 spinal cord dorsal horn, which started at 2 min, peaked at 30–60 min and almost disappeared at 4 h following intraplantar injection of BmK venom. Intrathecal injection of U0126 (0.1, 1.0 and 10 μg), a widely used specific MAP kinase kinase (MEK) inhibitor, suppressed spontaneous nociceptive responses and reduced primary heat hyperalgesia and bilateral mechanical hyperalgesia induced by BmK venom. In addition, BmK venom-induced spinal c-Fos expression could be inhibited by U0126 dose-dependently. Intrathecal delivery of NMDA receptor antagonist (5R, 10S)-(+)-5-methyl-10, 11-dihydro-5H-dibenzo [a,d]-cyclohepten-5-10-imine hydrogen maleate (MK-801) and the non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) could partially inhibit activation of spinal ERK induced by BmK venom at 30 min. Thus, activation of ERK in spinal cord dorsal horn, partially mediated by NMDA and non-NMDA receptor, potentially contributes to BmK venom-induced pain-related behaviors.     

Scorpion BmK venom induces nociceptive response of rats by plantar injection

In this study, the nociceptive responses induced by subcutaneous injection of scorpion BmK venom into the plantar surface of rat hind paw were quantified. The suitable dose of the venom is between 0.01 and 0.05 mg. The venom injection could induce local edema and tonic-pain responses, which had lasted more than 1 h. The pain scores reached peak intensity within 20 min, and then decreased slowly. Morphine, as a classic analgesic drug, could inhibit the spontaneous nociceptive response induced by the venom. With Morphine pretreatment, the mean pain scores for the entire 60 min were significantly decreased (P<.05). BmK I, a main lethal component, was also found to induce nociceptive responses with dose-dependent means. The nociceptive responses induced by BmK I could be partially inhibited by morphine.