Townsend-Nicholson A, King B F, Wildman S S, Burnstock G
Autonomic Neuroscience Institute, Royal Free and University College Medical School, University College London, Royal Free Campus, Rowland Hill Street, London NW3 2PF,
Brain Res Mol Brain Res. 1999 Feb 5;64(2):246-54. doi: 10.1016/s0169-328x(98)00328-3.
We have cloned and functionally characterised the mouse orthologue of the P2X4 receptor, mP2X4, and a splice variant of this receptor, mP2X4a. mP2X4 is 388 amino acids in length and shares 94% and 87% identity with the rat and human P2X4 receptors, respectively, while mP2X4a is 361 amino acids in length and lacks a 27-amino acid region in the extracellular domain corresponding to exon 6 of the known P2X receptor gene structures. When expressed in Xenopus laevis oocytes, mP2X4 produces a rapid inward current in response to ATP with an EC50 of 1.68+/-0.2 microM, consistent with the affinity of the rat and human P2X4 receptors for ATP. This agonist response is potentiated by the P2X receptor antagonists suramin, Reactive blue 2 and, over a limited concentration range, by PPADS. Although mP2X4a forms a poorly functional homomeric receptor, it appears able to interact with the full-length mP2X4 subunit to result in a functional channel with a reduced affinity for ATP. These results suggest a possible role for splice variants of P2X receptors in the formation of functional heteromeric ion channels.
我们已经克隆并对P2X4受体的小鼠同源物mP2X4及其一个剪接变体mP2X4a进行了功能特性分析。mP2X4全长388个氨基酸，与大鼠和人类的P2X4受体分别具有94%和87%的同一性，而mP2X4a全长361个氨基酸，在细胞外结构域中缺少一个对应于已知P2X受体基因结构外显子6的27个氨基酸的区域。当在非洲爪蟾卵母细胞中表达时，mP2X4对ATP产生快速内向电流，其EC50为1.68±0.2微摩尔，这与大鼠和人类P2X4受体对ATP的亲和力一致。P2X受体拮抗剂苏拉明、活性蓝2以及在有限浓度范围内的PPADS可增强这种激动剂反应。尽管mP2X4a形成的同聚体受体功能较差，但它似乎能够与全长mP2X4亚基相互作用，从而形成一个对ATP亲和力降低的功能性通道。这些结果表明P2X受体的剪接变体在功能性异聚离子通道形成中可能发挥作用。
