Department of Cell Biology and Biophysics, Faculty of Biology, University of Athens, Panepistimiopolis, Athens, Greece.
PLoS One. 2011;6(10):e26033. doi: 10.1371/journal.pone.0026033. Epub 2011 Oct 7.
We have showed that secretory Apolipoprotein J/Clusterin (sCLU) is down-regulated in senescent, stressed or diseased red blood cells (RBCs). It was hypothesized that sCLU loss relates to RBCs vesiculation, a mechanism that removes erythrocyte membrane patches containing defective or potentially harmful components.
METHODOLOGY/PRINCIPAL FINDINGS: To investigate this issue we employed a combination of biochemical and microscopical approaches in freshly prepared RBCs or RBCs stored under standard blood bank conditions, an in vitro model system of cellular aging. We found that sCLU is effectively exocytosed in vivo during membrane vesiculation of freshly prepared RBCs. In support, the RBCs' sCLU content was progressively reduced during RBCs ex vivo maturation and senescence under cold storage due to its selective exocytosis in membrane vesicles. A range of typical vesicular components, also involved in RBCs senescence, like Band 3, CD59, hemoglobin and carbonylated membrane proteins were found to physically interact with sCLU.
CONCLUSIONS/SIGNIFICANCE: The maturation of RBCs is associated with a progressive loss of sCLU. We propose that sCLU is functionally involved in the disposal of oxidized/defected material through RBCs vesiculation. This process most probably takes place through sCLU interaction with RBCs membrane proteins that are implicit vesicular components. Therefore, sCLU represents a pro-survival factor acting for the postponement of the untimely clearance of RBCs.
我们已经表明，分泌载脂蛋白 J/簇蛋白（sCLU）在衰老、应激或患病的红细胞（RBC）中下调。据推测，sCLU 的丢失与 RBC 的囊泡形成有关，这是一种去除含有缺陷或潜在有害成分的红细胞膜片的机制。
方法/主要发现：为了研究这个问题，我们在新鲜制备的 RBC 或在标准血库条件下储存的 RBC（细胞衰老的体外模型系统）中采用了生化和显微镜方法的组合。我们发现 sCLU 在新鲜制备的 RBC 的膜囊泡形成过程中在体内有效地被外排。支持这一观点的是，由于其在膜囊泡中的选择性外排，RBC 的 sCLU 含量在 RBC 体外成熟和冷储存过程中的衰老过程中逐渐减少。一系列典型的囊泡成分，如 Band 3、CD59、血红蛋白和羰基化的膜蛋白，也参与了 RBC 的衰老，与 sCLU 发生物理相互作用。
结论/意义：RBC 的成熟与 sCLU 的逐渐丢失有关。我们提出，sCLU 通过 RBC 囊泡化参与了氧化/缺陷物质的处理。这个过程很可能是通过 sCLU 与 RBC 膜蛋白的相互作用来实现的，这些膜蛋白是囊泡的固有成分。因此，sCLU 代表了一种促生存因子，它通过推迟 RBC 的过早清除来发挥作用。
