Romero Eneida A, Valdivieso Elizabeth, Cohen B Eleazar
Institute of Experimental Biology, Faculty of Sciences, Central University of Venezuela, Caracas, Venezuela.
J Membr Biol. 2009 Jul;230(2):69-81. doi: 10.1007/s00232-009-9187-z. Epub 2009 Jul 23.
The polyene antibiotic amphotericin B (AmB) is known to form aqueous pores in lipid membranes and biological membranes. Here, membrane potential and ion permeability measurements were used to demonstrate that AmB can form two types of selective ion channels in human erythrocytes, differing in their interaction with cholesterol. We show that AmB induced a cation efflux (negative membrane polarization) across cholesterol-containing liposomes and erythrocytes at low concentrations (< or =1.0 x 10(-6) M), but a sharp reversal of such polarization was observed at concentrations greater than 1.0 x 10(-6) M AmB, an indication that aqueous pores are formed. Cation-selective AmB channels are also formed across sterol-free liposomes, but aqueous pores are only formed at AmB concentrations 10 times greater. The effect of temperature on the AmB-mediated K+ efflux across erythrocytes revealed that the energies of activation for channel formation are negative and positive at AmB concentrations that lead predominantly to the formation of cation-selective channels and aqueous pores, respectively. These findings support the conclusion that the two types of AmB channels formed in human erythrocytes differ in their interactions with cholesterol and other membrane components. In effect, a membrane lipid reorganization, as induced by incubation of erythrocytes with tetrathionate, a cross-linking agent of the lipid raft-associated protein spectrin, led to differential changes in the activation parameters for the formation of both types of channels, reflecting the different lipid environments in which such structures are formed.
多烯抗生素两性霉素B（AmB）已知可在脂质膜和生物膜中形成水通道。在此，通过膜电位和离子通透性测量来证明AmB可在人红细胞中形成两种类型的选择性离子通道，它们与胆固醇的相互作用有所不同。我们发现，在低浓度（≤1.0×10⁻⁶ M）时，AmB可诱导阳离子流出（负膜极化）穿过含胆固醇的脂质体和红细胞，但在AmB浓度大于1.0×10⁻⁶ M时，观察到这种极化的急剧逆转，这表明形成了水通道。阳离子选择性的AmB通道也可在无甾醇脂质体中形成，但仅在AmB浓度高出10倍时才会形成水通道。温度对AmB介导的K⁺穿过红细胞流出的影响表明，在主要导致形成阳离子选择性通道和水通道的AmB浓度下，通道形成的活化能分别为负和正。这些发现支持了这样的结论：在人红细胞中形成的两种类型的AmB通道与胆固醇及其他膜成分的相互作用不同。实际上，用四硫代酸盐（一种脂质筏相关蛋白血影蛋白的交联剂）孵育人红细胞所诱导的膜脂质重组，导致两种类型通道形成的活化参数发生不同变化，这反映了形成这些结构的不同脂质环境。
