Human tear viscosity: An interactive role for proteins and lipids
Human tear viscosity: An interactive role for proteins and lipids
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DOI：
10.1016/j.bbapap.2005.08.023
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发表时间：
2005-12-01
影响因子：
3.2
通讯作者：
Tiffany, JM
中科院分区：
文献类型：
--
作者：
Gouveia, SM;Tiffany, JM
人类泪液粘度知之甚少。泪液需要保留在眼表上用于润滑，而不会由于眨眼时的拖拽而对表面上皮细胞造成损伤。整个眼泪是剪切稀化的（非牛顿），这不能用粘蛋白的量来解释，也不能用单个蛋白质来解释。整个眼泪减去脂质变成牛顿流体。虽然没有，但以前在收集的泪液中发现了游离脂质，但已知泪液脂质运载蛋白（TL）是一种主要的泪液蛋白质，可以结合脂质。在这项研究中，我们的目的是确认是否有任何游离脂质在收集的眼泪，并澄清眼泪蛋白质的粘度，包括重组TL的实验，无论是没有（载脂蛋白TL）和（holo-TL）结合脂质的组合贡献。我们还研究了可能的低聚物形成的全息和载脂蛋白TL作为一种机制，粘度使用SDS-PAGE和分析超离心（Au）。为了进行比较，我们纳入了β-乳球蛋白（一种充分表征的脂质运载蛋白）的结果。在整个泪液中未检测到游离脂质。流变学表明，包括溶菌酶或乳铁蛋白的任何蛋白质组合都是剪切稀化的，apo-TL也是如此，尽管holo-TL是牛顿的（线性的）。SDS-PAGE和Au分析结果显示apo-TL完全为单体，而holo-TL则有部分二聚化。载脂蛋白和全β-乳球蛋白均表现出单体-二聚体平衡。我们得出结论，杂蛋白相互作用，可能是静电，涉及脂质结合诱导的结构变化TL，显着有助于人类眼泪的粘度。(c)2005 Elsevier B.V保留所有权利。
Human tear viscosity is poorly understood. Tears need to remain on the ocular surface for lubrication without causing damage to the surface epithelia due to drag when blinking. Whole tears are shear-thinning (non-Newtonian), which cannot be explained by the amount of mucin present, nor by individual proteins. Whole tears minus lipids become Newtonian. Though no, free lipids had previously been found in collected tears, tear lipocalin (TL), a major tear protein, is known to bind lipids. In this study, we aimed to confirm whether there are any free lipids in collected tears, and to clarify the combined contribution of tear proteins to viscosity, including experiments on recombinant TL, both without (apo-TL) and with (holo-TL) bound lipid. We also investigated possible oligomer formation by holo- and apo-TL as a mechanism, for viscosity using SDS-PAGE and analytical ultracentrifugation (AU). For comparison, we have included results for beta-lactoglobulin, a well-characterised lipocalin protein. No free lipids were detected in whole tears. Rheology showed that any protein combination that included lysozyme or lactoferrin was shear-thinning, as was apo-TL, though holo-TL was Newtonian (linear). Results from SDS-PAGE and AU showed apo-TL to be entirely monomeric, but holo-TL showed some dimerization. Both apo- and holo-beta-lactoglobulin exhibited a monomer-dimer equilibrium. We conclude that hetero-protein interactions, possibly electrostatic, involving lipid-binding-induced structural changes to TL, significantly contribute to the viscosity of human tears. (c) 2005 Elsevier B.V All rights reserved.