Interaction of heme and heme-hemopexin with an extracellular oxidant system used to measure cell growth-associated plasma membrane electron transport.
Interaction of heme and heme-hemopexin with an extracellular oxidant system used to measure cell growth-associated plasma membrane electron transport.
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血红素和血红素-血红素结合蛋白与细胞外氧化剂系统的相互作用，用于测量细胞生长相关的质膜电子传递。
DOI：
10.1016/j.bbabio.2007.06.003
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发表时间：
2007
期刊：
影响因子：
--
通讯作者：
Smith,Ann
中科院分区：
文献类型：
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作者：
Rish,KimberlyR;Swartzlander,Ryan;Sadikot,TakrimaN;Berridge,MichaelV;Smith,Ann
由于氧化还原活性金属通常以还原状态跨膜转运到细胞中，因此我们研究了外源铁血红素或与血红素结合蛋白（HPX）结合的血红素是否与细胞生长相关的质膜电子传递（PMET）途径相互作用，HPX通过受体介导的内吞作用将血红素递送至细胞。在强制低电位中间电子受体 mPMS 存在的情况下，PMET 会还原细胞不可渗透的四唑盐 WST-1。在人早幼粒细胞 (HL60) 细胞中，原血红素（铁原卟啉 IX；2,4-乙烯基）、中血红素（2,4-乙基）和次血红素 (2,4-H) 以可饱和的方式抑制 WST-1/mPMS 的还原，支持与有限数量的高亲和力受体位点的相互作用（天然存在的原血红素的 Kd 221 nM）。使用镓原卟啉 IX (PPIX) 和锡-PPIX 显示了对氧化还原活性铁的需求。血红素血红素（而非载脂血红素结合蛋白）也抑制 WST-1 还原，并且需要铜。重要的是，由于血红素和血红素-血红素结合蛋白都不能取代 mPMS 作为中间电子受体，并且由于抑制 WST-1/mPMS 还原需要活细胞，因此实验证据支持血红素和血红素-血红素结合蛋白与来自 PMET 的电子相互作用的观点。因此，我们认为血红素和血红素-血红素结合蛋白是这种与生长相关的电子跨质膜转移的天然底物。
Since redox active metals are often transported across membranes into cells in the reduced state, we have investigated whether exogenous ferri-heme or heme bound to hemopexin (HPX), which delivers heme to cells via receptor-mediated endocytosis, interact with a cell growth-associated plasma membrane electron transport (PMET) pathway. PMET reduces the cell-impermeable tetrazolium salt, WST-1, in the presence of the mandatory low potential intermediate electron acceptor, mPMS. In human promyelocytic (HL60) cells, protoheme (iron protoporphyrin IX; 2,4-vinyl), mesoheme (2,4-ethyl) and deuteroheme (2,4-H) inhibited reduction of WST-1/mPMS in a saturable manner supporting interaction with a finite number of high affinity acceptor sites (Kd 221 nM for naturally occurring protoheme). A requirement for the redox-active iron was shown using gallium-protoporphyrin IX (PPIX) and tin-PPIX. Heme–hemopexin, but not apo-hemopexin, also inhibited WST-1 reduction, and copper was required. Importantly, since neither heme nor heme–hemopexin replace mPMS as an intermediate electron acceptor and since inhibition of WST-1/mPMS reduction requires living cells, the experimental evidence supports the view that heme and heme–hemopexin interact with electrons from PMET. We therefore propose that heme and heme–hemopexin are natural substrates for this growth-associated electron transfer across the plasma membrane.