Role of glucose carrier in human erythrocyte water permeability.
Role of glucose carrier in human erythrocyte water permeability.
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DOI：
10.1021/bi00117a041
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发表时间：
1992-01
期刊：
影响因子：
2.9
通讯作者：
M. Zeidel;A. Albalak;E. Grossman;A. Carruthers
中科院分区：
文献类型：
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作者：
M. Zeidel;A. Albalak;E. Grossman;A. Carruthers
尽管人类红细胞水通道的运输特性已经被很好地描述，但介导水流动的蛋白质(S)的身份仍然不清楚。最近的证据表明，葡萄糖载体可以传导水，这增加了这样一种可能性，即人体红细胞中丰富的葡萄糖载体就是水通道。为了验证这种可能性，我们测量了含有人红细胞脂的大单层囊泡(LUV)、重组纯化的人红细胞葡萄糖载体(Glut1 LUV)和含有其他人红细胞幽灵蛋白的重组葡萄糖载体(Ghost LUV)的水通透性和葡萄糖通量。在葡萄糖和Glut1LUV中，葡萄糖载体的密度为天然红细胞密度的25%，在双层中随机定向，并在细胞松弛素B作用下表现出典型的葡萄糖通量抑制。渗透水渗透率(PF，单位为厘米/秒；n=4)平均为0.0012+/-0.00033，0.0032+/-0.0015，0.006+/-0.0014。3种制剂的水流活化能在10~13kcal/mol之间，有机汞离子通道阻滞剂对氯汞苯磺酸盐(PCMBS)和细胞松弛素B不改变Pf。这些结果表明，葡萄糖载体在高密度下的重组增加了水的通透性，但不会导致水通道的活动。然而，由于重组载体的周转次数比天然载体少，因此也在具有完整水通道功能的红细胞幽灵上进行了实验。在幽灵中，Pf平均为0.038+/-0.013(n=9)，而水流的激活能平均为3.0+/-0.3kcal/mo.(摘要截断250字)
Although the transport properties of human erythrocyte water channels have been well characterized, the identity of the protein(s) mediating water flow remains unclear. Recent evidence that glucose carriers can conduct water raised the possibility that the glucose carrier, which is abundant in human erythrocytes, is the water channel. To test this possibility, water permeabilities and glucose fluxes were measured in large unilamellar vesicles (LUV) containing human erythrocyte lipid alone (lipid LUV), reconstituted purified human erythrocyte glucose carrier (Glut1 LUV), or reconstituted glucose carrier in the presence of other human erythrocyte ghost proteins (ghost LUV). In glucose and ghost LUV, glucose carriers were present at 25% of the density of native erythrocytes, were oriented randomly in the bilayer, and exhibited characteristic inhibition of glucose flux when exposed to cytochalasin B. Osmotic water permeability (Pf, in centimeters per second; n = 4) averaged 0.0012 +/- 0.00033 in lipid LUV, 0.0032 +/- 0.0015 in Glut1 LUV, and 0.006 +/- 0.0014 in ghost LUV. Activation energies of water flow for the three preparations ranged between 10 and 13 kcal/mol; p-(chloromercuri)benzenesulfonate (pCMBS), an organic mercurial inhibitor of erythrocyte water channels, and cytochalasin B did not alter Pf. These results indicate that reconstitution of glucose carriers at high density increases water permeability but does not result in water channel activity. However, because the turnover number of reconstituted carriers is reduced from that of native carriers, experiments were also performed on erythrocyte ghosts with intact water channel function. In ghosts, Pf averaged 0.038 +/- 0.013 (n = 9), while the activation energy for water flow averaged 3.0 +/- 0.3 kcal/mol.(ABSTRACT TRUNCATED AT 250 WORDS)