Espino Samuel S, Robinson Samuel D, Safavi-Hemami Helena, Gajewiak Joanna, Yang Weishan, Olivera Baldomero M, Liu Qin
Department of Anesthesiology and Center for the Study of Itch, Washington University School of Medicine, St. Louis MO 63110, USA.
Department of Biology, University of Utah, Salt Lake City UT 84112, USA.
Toxicon. 2018 Nov;154:28-34. doi: 10.1016/j.toxicon.2018.09.002. Epub 2018 Sep 21.
Members of Mas related G-protein coupled receptors (Mrgpr) are known to mediate itch. To date, several compounds have been shown to activate these receptors, including chloroquine, a common antimalarial drug, and peptides of the RF-amide family. However, specific ligands for these receptors are still lacking and there is a need for novel compounds that can be used to modulate the receptors in order to understand the cellular and molecular mechanism in which they mediate itch. Some cone snail venoms were previously shown to induce itch in mice. Here, we show that the venom of Conus textile induces itch through activation of itch-sensing sensory neurons, marked by their sensitivity to chloroquine. Two RF-amide peptides, CNF-Tx1 and CNF-Tx2, were identified in a C. textile venom gland transcriptome. These belong to the conorfamide family of peptides which includes previously described peptides from the venoms of Conus victoriae (CNF-Vc1) and Conus spurius (CNF-Sr1 and CNF-Sr2). We show that CNF-Vc1 and CNF-Sr1 activate MrgprC11 whereas CNF-Vc1 and CNF-Tx2 activate the human MrgprX1 (hMrgprX1). The peptides CNF-Tx1 and CNF-Sr2 do not activate MrgprC11 or hMrgprX1. Intradermal injection of CNF-Vc1 and CNF-Tx2 into the cheek of a transgenic mouse expressing hMrgprX1 instead of endogenous mouse Mrgprs resulted in itch-related scratching thus demonstrating the in vivo activity of these peptides. Using truncated analogues of CNF-Vc1, we identified amino acids at positions 7-14 as important for activity against hMrgprX1. The conopeptides reported here are tools that can be used to advance our understanding of the cellular and molecular mechanism of itch mediated by Mrgprs.
已知 Mas 相关 G 蛋白偶联受体（Mrgpr）成员介导瘙痒。迄今为止，已有几种化合物被证明可激活这些受体，包括常见的抗疟药物氯喹以及 RF-酰胺家族的肽。然而，这些受体的特异性配体仍然缺乏，需要新型化合物来调节这些受体，以便了解它们介导瘙痒的细胞和分子机制。此前有研究表明，一些芋螺毒液可在小鼠中诱发瘙痒。在此，我们表明，织锦芋螺毒液通过激活对氯喹敏感的瘙痒感觉神经元来诱发瘙痒。在织锦芋螺毒液腺转录组中鉴定出两种 RF-酰胺肽，即 CNF-Tx1 和 CNF-Tx2。这些肽属于芋螺酰胺肽家族，该家族包括先前描述的来自维多利亚芋螺毒液的肽（CNF-Vc1）以及尖芋螺毒液的肽（CNF-Sr1 和 CNF-Sr2）。我们发现，CNF-Vc1 和 CNF-Sr1 激活 MrgprC11，而 CNF-Vc1 和 CNF-Tx2 激活人类 MrgprX1（hMrgprX1）。肽 CNF-Tx1 和 CNF-Sr2 不激活 MrgprC11 或 hMrgprX1。将 CNF-Vc1 和 CNF-Tx2 皮内注射到表达 hMrgprX1 而非内源性小鼠 Mrgprs 的转基因小鼠脸颊中，会导致与瘙痒相关的抓挠行为，从而证明了这些肽在体内的活性。使用 CNF-Vc1 的截短类似物，我们确定了第 7 - 14 位的氨基酸对于抗 hMrgprX1 活性很重要。本文报道的芋螺肽是可用于推进我们对 Mrgprs 介导瘙痒的细胞和分子机制理解的工具。
