Mechanism of Zinc Potentiation of P2X Receptors

描述(申请人提供)：P2X受体是由细胞外ATP调控的阳离子通道。这些通道的信号缺陷会导致痛觉、男性生育能力和声音传导的缺陷。当细胞外加锌时，由P2X2亚单位组成的同源通道显示出对ATP诱导电流的增强。在P2X2中，锌增强独立地需要胞外组氨酸120和213。假设这些残基直接参与一个锌结合部位，当锌结合时，这两个残基之间的距离改变，从而使离子通道的开放状态稳定下来。为了验证这一假设，将搜索可能与锌结合有关的其他残基。此外，残基120和213将被一个小分子的结合所阻断，并将测量锌的增效量。根据这一假说，预计锌的增强作用将会减弱。最后，残基120和213将与各种分子交联。预计一定大小的刚性交联剂将产生永久处于增强或非增强状态的通道，而与锌的存在无关。

DESCRIPTION (provided by applicant): P2X receptors are cation channels gated by extra cellular ATP. Defects in signaling by these channels result in deficits in pain perception, male fertility, and sound transduction. Homomeric channels made up of the P2X2 subunit show potentiation of ATP-induced current when extra cellular zinc is applied. In P2X2, extra cellular histidines 120 and 213 are independently required for zinc potentiation. It is hypothesized that these residues directly participate in a zinc binding site, and that when zinc is bound, the distance between these two residues changes such that the open state of the ion channel is stabilized. To test this hypothesis, a search will be made for other residues potentially involved in binding zinc. Additionally, residues 120 and 213 will be blocked by the binding of a small molecule, and the amount of zinc potentiation will be measured. Based on the hypothesis, it is expected that zinc potentiation will decrease. Finally, residues 120 and 213 will be cross-linked with various molecules. It is expected that rigid cross linkers of certain size will yield channels that are permanently either in the potentiated or non-potentiated state, regardless of the presence of zinc.