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An ATP-dependent mechanism protects spectrin against glycation in human erythrocytes

ATP 依赖性机制可保护血影蛋白免受人红细胞糖化的影响

基本信息

批准号：
19590289
负责人：
MANNO Sumie
金额：
$ 2.91万
依托单位：
Tokyo Women's Medical University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2007
资助国家：
日本
起止时间：
2007 至 2009
项目状态：
已结题

项目摘要

Human erythrocytes are continuously exposed to glucose which reacts with the amino terminus of the ・-chain of hemoglobin (Hb) to form glycated Hb, HbA1c, levels of which increase with the age of the circulating cell. In contrast to extensive insights into glycation of hemoglobin, little is known about glycation of erythrocyte membrane proteins. In the present study, we explored the conditions under which glucose and ribose can glycate spectrin, both on the intact membrane and in solution and the functional consequences of spectrin glycation. While purified spectrin could be readily glycated, membrane-associated spectrin could be glycated only after ATP depletion and consequent translocation of phosphatidylserine (PS) from the inner to the outer lipid monolayer. Glycation of membrane-associated spectrin led to a marked decrease in membrane deformability. We further observed that only PS-binding spectrin repeats are glycated. We infer that the absence of glycation in situ is the consequence of the interaction of the target lysine and arginine residues with PS and thus being inaccessible for glycation. The reduced membrane deformability following glycation in the absence of ATP is likely the result of the inability of the glycated spectrin repeats to undergo the obligatory unfolding as a consequence of inter-helix crosslinks. We thus postulate that erythrocytes through the use of an ATP-driven phospholipids translocase have evolved a protective mechanism against spectrin glycation and thus maintain their optimal membrane function during their long circulatory life span.

人红细胞持续暴露于葡萄糖，葡萄糖与血红蛋白（Hb）的·-链的氨基末端反应形成糖化Hb，HbA 1c，其水平随着循环细胞的年龄而增加。与对血红蛋白糖化的深入了解相反，对红细胞膜蛋白的糖化知之甚少。在本研究中，我们探讨了葡萄糖和核糖可以糖化血影蛋白的条件下，无论是在完整的膜和溶液和血影蛋白糖化的功能后果。虽然纯化的血影蛋白可以很容易地糖化，膜相关血影蛋白可以糖化后，ATP耗尽和随之而来的移位磷脂酰丝氨酸（PS）从内部到外部的脂质单层。膜相关血影蛋白的糖基化导致膜变形能力显著降低。我们进一步观察到，只有PS结合血影蛋白重复被糖化。我们推断，原位糖化的情况下是目标赖氨酸和精氨酸残基与PS的相互作用的结果，因此无法进行糖化。在不存在ATP的情况下糖基化后降低的膜变形性可能是由于糖化血影蛋白重复序列由于螺旋间交联而不能进行强制性解折叠的结果。因此，我们假设红细胞通过使用ATP驱动的磷脂移位酶已经进化出一种针对血影蛋白糖化的保护机制，从而在其长循环寿命期间保持其最佳膜功能。