The gp91phox component of NADPH oxidase is not a voltage-gated proton channel.
The gp91phox component of NADPH oxidase is not a voltage-gated proton channel.
复制标题
DOI：
10.1085/jgp.20028704
复制
发表时间：
2002-12
影响因子：
3.8
通讯作者：
Cherny, Vladimir V
中科院分区：
文献类型：
--
作者：
DeCoursey, Thomas E;Morgan, Deri;Cherny, Vladimir V
在吞噬细胞的“呼吸爆发”期间，NADPH氧化酶通过产生超氧阴离子O2 J来帮助杀死微生物。如图1中的卡通图所示，NADPH氧化酶复合体有几个组成部分。在未受刺激的细胞中，四种组分(p67Phox、p40Phox、p47Phox和一个G蛋白Rac)位于胞浆中，gp91Phox和p22Phox是膜结合的。在细菌、佛波酯或趋化肽的刺激下，复合体组装并开始产生O2-J。这是通过传输电子从细胞内的NADPH穿过细胞膜将细胞外的O2还原为O2-J来完成的。在没有电荷补偿的情况下，人类嗜酸性粒细胞中的电子外流将使膜去极化12V/S，而相反的电压将在20ms内关闭氧化酶。Henderson等人(1987,1988a，b)证明了人中性粒细胞中的电源性H+外流通过NADPH氧化酶复合体补偿了电源性电子转移。人们的共识是，电子电流是由电压门控质子通道介导的质子外流来平衡的。最近的一项建议认为，K+外流贡献了总电荷补偿的6%(Reeves等人，2002年)，仍然将94%的工作留给了质子通道。这些H+通道的分子身份尚不清楚。许多证据表明gp91Phox可以作为质子通道发挥作用，但对证据的严格检查表明情况并非如此。双方的证据大致分为两大类：异源表达研究和间接证据。声称gp91Phox具有质子通道功能的异源表达研究不能令人信服，原因有二。(A)在某些情况下，gp91Phox细胞中假定的H+电流根本不具有天然细胞中电压门控质子电流的特性。(B)那些显示gp91Phox细胞中真实H+电流的研究是在一个表达系统中完成的，该表达系统具有与报告的电压门控质子电流类似的幅度。当我们在没有内源性H+通道的COS-7细胞中表达gp91Phox时，没有检测到H+电流，
During the “respiratory burst” in phagocytes, NADPH oxidase helps kill microbes by producing superoxide anion, O2 J. As illustrated in the cartoon in Fig. 1, the NADPH oxidase complex has several components. In unstimulated cells, four components (p67phox, p40phox, p47phox, and a G protein, Rac) are located in the cytosol, and gp91phox and p22phox are membrane bound. Upon stimulation by bacteria, PMA (phorbol ester), or chemotactic peptides, the complex assembles and begins to generate O2 J. This is accomplished by transporting electrons from NADPH inside the cell, across the cell membrane to reduce extracellular O2 to O2 J. Without charge compensation, the electron efflux in a human eosinophil would depolarize the membrane by 12 V/s, and this opposing voltage would shut down the oxidase within 20 ms. Henderson et al.(1987, 1988a, b) demonstrated that electrogenic H+ efflux in human neutrophils compensates for electrogenic electron translocation through the NADPH oxidase complex. The consensus is that the electron current is balanced by proton efflux mediated by voltage-gated proton channels. A recent suggestion that K+ efflux contributes 6% of the total charge compensation (Reeves et al., 2002), still leaves 94% of the job to proton channels. The molecular identity of these H+ channels is not known.A variety of evidence has been interpreted to suggest that gp91phox can function as a proton channel, but critical examination of the evidence shows that this is not the case. The evidence on both sides falls into two general categories: heterologous expression studies and circumstantial evidence. The heterologous expression studies claiming proton channel function for gp91phox are unconvincing for two reasons.(a) In some cases, the putative H+ currents in gp91phox transfected cells simply do not have the properties of voltage-gated proton currents in native cells.(b) Those studies showing genuine H+ currents in gp91phox-transfected cells were done in an expression system that constitutively exhibits voltage-gated proton currents of amplitude similar to that reported in the transfected cells. When we expressed gp91phox in COS-7 cells that have no endogenous H+ channels, no H+ current could be detected,