Park Seung Pyo, Kim Byung Moon, Koo Jae Yeon, Cho Hawon, Lee Chang Hoon, Kim Misook, Na Heung Sik, Oh Uhtaek
The Sensory Research Center, Creative Research Initiatives Seoul National University, College of Pharmacy, Kwanak, Shillim 9-dong, Seoul 151-742, Republic of Korea Department of Physiology, College of Medicine, Korea University, 126-1 Anam-dong 5 Ga, Sungbuk, Seoul 136-705, Republic of Korea.
Pain. 2008 Jul;137(1):208-217. doi: 10.1016/j.pain.2008.02.013. Epub 2008 Mar 24.
Mechanosensitive channels mediate various physiological functions including somatic sensation or pain. One of the peptide toxins isolated from the venom of the Chilean rose tarantula spider (Grammostola spatulata), mechanotoxin 4 (GsMTx4) is known to block stretch-activated cation channels. Since mechanosensitive channels in sensory neurons are thought to be molecular sensors for mechanotransduction, i.e., for touch, pressure, proprioception, and pain, we considered that the venom might block some types of mechanical pain. In order to prepare sufficiently large amounts of GsMTx4 for in vivo nociceptive behavioral tests, we constructed recombinant peptide of GsMTx4. Because the amino-acid sequence of the toxin, but not the nucleotide sequence, is known, we back-translated its amino-acid sequence to nucleotide sequence of yeast codons, constructed a template DNA, subcloned this into a Pichia pastoris expression vector, and purified the recombinant peptide. Intraperitoneal injection of the recombinant GsMTx4 to rats significantly increased the mechanical threshold for paw withdrawal in Randall Sellito test, eliciting significant analgesic responses to inflammation-induced mechanical hyperalgesia. GsMTx4 also reduced mechanical allodynia induced by inflammation and by sciatic nerve injury in Von Frey test. However, the venom was ineffective at changing withdrawal latency in hot plate and tail-flick tests. These results suggest that GsMTx4 selectively alleviates mechanical hyperalgesia, which it presumably achieves by blocking mechanosensitive channels. Because the peptide venom induces analgesia for some forms of mechanical pain, GsMTx4 appears to have potential clinical use as a pain treatment.
机械敏感通道介导包括躯体感觉或疼痛在内的多种生理功能。从智利玫瑰捕鸟蛛（Grammostola spatulata）毒液中分离出的一种肽毒素——机械毒素4（GsMTx4），已知可阻断牵张激活阳离子通道。由于感觉神经元中的机械敏感通道被认为是机械转导的分子传感器，即用于触觉、压力、本体感觉和疼痛，我们认为该毒液可能会阻断某些类型的机械性疼痛。为了制备足够大量的GsMTx4用于体内伤害性感受行为测试，我们构建了GsMTx4的重组肽。由于该毒素的氨基酸序列已知而核苷酸序列未知，我们将其氨基酸序列反向翻译成酵母密码子的核苷酸序列，构建了一个模板DNA，将其亚克隆到毕赤酵母表达载体中，并纯化了重组肽。给大鼠腹腔注射重组GsMTx4可显著提高兰德尔·塞利托试验中爪部撤离的机械阈值，对炎症诱导的机械性痛觉过敏产生显著的镇痛反应。GsMTx4还可减轻在冯·弗雷试验中由炎症和坐骨神经损伤诱导的机械性异常性疼痛。然而，该毒液在热板试验和甩尾试验中对改变撤离潜伏期无效。这些结果表明，GsMTx4选择性地减轻机械性痛觉过敏，这可能是通过阻断机械敏感通道实现的。由于该肽毒液对某些形式的机械性疼痛具有镇痛作用，GsMTx4似乎具有作为疼痛治疗的潜在临床用途。
