Identification of a peptide toxin from Grammostola spatulata spider venom that blocks cation-selective stretch-activated channels.
Identification of a peptide toxin from Grammostola spatulata spider venom that blocks cation-selective stretch-activated channels.
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DOI：
10.1085/jgp.115.5.583
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发表时间：
2000-05
期刊：
影响因子：
--
通讯作者：
Sachs F
中科院分区：
文献类型：
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作者：
Suchyna TM;Johnson JH;Hamer K;Leykam JF;Gage DA;Clemo HF;Baumgarten CM;Sachs F
我们已经鉴定出一种35个氨基酸的多肽毒素，属于半胱氨酸结抑制剂家族，它可以阻断阳离子拉伸激活的离子通道。这种毒素被命名为GsMTx-4，是从平铲蜘蛛的毒液中分离出来的，与其他神经活性多肽有50%的同源性。用反相高效液相色谱分离整个蛇毒，然后测定成年大鼠星形胶质细胞外向贴片拉伸激活通道(SACS)上的部分组分。尽管电池贴片和自外向外贴片的通道门控动力学不同，但与通道孔相关的特性，如对碱性阳离子的选择性、电导(在∼100 mV时为−45ps)和温和的整流不受自外向外形成的影响。GsMTx-4在外向外贴片中产生了完整的囊泡块，由于它对整个细胞的电压敏感电流没有影响，因此看起来是特异的。根据缔合速率常数和离解速率常数的比值计算了∼630 nm的平衡离解常数。在低张肿胀的星形胶质细胞中，GsMTx-4使肿胀激活的全细胞电流的∼减少40%。同样，在兔扩张型心肌病模型的分离的心室细胞中，GsMTx-4几乎完全阻断了容量敏感的阳离子选择电流，但不影响阴离子电流。在肌病心肌细胞中，膨胀诱导的电流在张力上是活跃的，GsMTx-4也缩小了细胞大小。这是首次报道一种特定阻断伸展激活电流的多肽毒素。毒素对肿胀激活的全细胞电流的影响与囊的容量调节有关。
We have identified a 35 amino acid peptide toxin of the inhibitor cysteine knot family that blocks cationic stretch-activated ion channels. The toxin, denoted GsMTx-4, was isolated from the venom of the spider Grammostola spatulata and has <50% homology to other neuroactive peptides. It was isolated by fractionating whole venom using reverse phase HPLC, and then assaying fractions on stretch-activated channels (SACs) in outside-out patches from adult rat astrocytes. Although the channel gating kinetics were different between cell-attached and outside-out patches, the properties associated with the channel pore, such as selectivity for alkali cations, conductance (∼45 pS at −100 mV) and a mild rectification were unaffected by outside-out formation. GsMTx-4 produced a complete block of SACs in outside-out patches and appeared specific since it had no effect on whole-cell voltage-sensitive currents. The equilibrium dissociation constant of ∼630 nM was calculated from the ratio of association and dissociation rate constants. In hypotonically swollen astrocytes, GsMTx-4 produces ∼40% reduction in swelling-activated whole-cell current. Similarly, in isolated ventricular cells from a rabbit dilated cardiomyopathy model, GsMTx-4 produced a near complete block of the volume-sensitive cation-selective current, but did not affect the anion current. In the myopathic heart cells, where the swell-induced current is tonically active, GsMTx-4 also reduced the cell size. This is the first report of a peptide toxin that specifically blocks stretch-activated currents. The toxin affect on swelling-activated whole-cell currents implicates SACs in volume regulation.