Effects of divalent cations, protons and calmidazolium at the rat P2X(7) receptor
Effects of divalent cations, protons and calmidazolium at the rat P2X(7) receptor
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DOI：
10.1016/s0028-3908(97)00141-x
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发表时间：
1997-09-01
影响因子：
4.7
通讯作者：
Surprenant, A
中科院分区：
文献类型：
--
作者：
Virginio, C;Church, D;Surprenant, A
P2 X（7）受体是一种独特的双功能分子，ATP可通过其打开离子型受体典型的小阳离子通道，并诱导可渗透高分子量分子（>600 Dal.这个大孔的激活可导致细胞在1-2分钟内溶解。我们通过在稳定表达大鼠P2 X（7）受体的HEK 293细胞中测量全细胞电流和丙啶染料（YO-PRO; M-W 629）的摄取，并比较这两种测定中二价阳离子和质子的作用，来询问阳离子通道和细胞透化孔之间是否存在药理学差异。响应于2 '-3'-（0）-（4-苯甲酰基苯甲酰基）ATP（BzATP，30 μ M）的电流被细胞外钙、镁、锌、铜和质子抑制，半最大抑制浓度（IC 50）分别为2.9 mM、0.5 mM、11 μ M、0.5 μ M和0.4 μ M。在每种情况下，抑制是电压无关的。BzATP诱导的YO-PRO摄取也受到抑制，IC 50值相似。一系列二价体的效价排序为Cu 2 + > Cd 2 + = Zn 2 + > Ni 2+，远大于Mg 2 + = Co 2 + > Mn 2 + > Ca 2 + = Ba 2 + = Sr 2+。这些结果表明，这些二价阳离子和质子都主要作为变构调节剂，以改变ATP与P2 X（7）受体结合的亲和力。相反，细胞外（而非细胞内）calmidazolium抑制BzATP诱发电流高达90%（IC 50 = 15 nM），但对YO-PRO摄取没有影响。因此，钙咪唑鎓可以阻断离子通道的活化，但这不能阻止大的透化孔的形成。(C)1997 Elsevier Science Ltd.
The P2X(7) receptor is a uniquely bifunctional molecule through which ATP can open a small cationic channel typical of ionotropic receptors and also induce a large pore permeable to high molecular weight molecules (>600 Dal. Activation of this large pore can lead to cell lysis within 1-2 min. We asked whether pharmacological differences existed between the cationic channel and the cell permeabilizing pore by measuring whole-cell currents and uptake of a propidium dye (YO-PRO; M-W 629) in HEK293 cells stably expressing the rat P2X(7) receptor, and comparing the actions of divalent cations and protons in these two assays. Currents in response to 2'-3'-(0)-(4-benzoyl benzoyl) ATP (BzATP, 30 mu M) were inhibited by extracellular calcium, magnesium, zinc, copper and protons with half-maximal inhibitory concentrations (IC50) of 2.9 mM, 0.5 mM, 11 mu M, 0.5 mu M and 0.4 mu M, respectively. The inhibition was voltage independent in each case. YO-PRO uptake induced by BzATP was also inhibited with similar IC50 values. The rank order of potency of a range of divalents was Cu2+ > Cd2+ = Zn2+ > Ni2+ much greater than Mg2+ = Co2+ > Mn2+ > Ca2+ = Ba2+ = Sr2+. These results suggest that these divalent cations and protons all act primarily as allosteric modulators to alter the affinity of ATP binding to the P2X(7) receptor. In contrast, extracellular (but not intracellular) calmidazolium inhibited the BzATP-evoked current by up to 90% (IC50 = 15 nM) but had no effect on YO-PRO uptake. Thus, calmidazolium can block activation of the ionic channel but this does not prevent the formation of the large permeabilizing pore. (C) 1997 Elsevier Science Ltd.