Université de Paris, UMR_S1134, BIGR, Inserm, F-75015 Paris, France.
Institut National de Transfusion Sanguine, F-75015 Paris, France.
Int J Mol Sci. 2020 Nov 28;21(23):9066. doi: 10.3390/ijms21239066.
Translocator protein (TSPO) and voltage dependent anion channels (VDAC) are two proteins forming a macromolecular complex in the outer mitochondrial membrane that is involved in pleiotropic functions. Specifically, these proteins were described to regulate the clearance of damaged mitochondria by selective mitophagy in non-erythroid immortalized cell lines. Although it is well established that erythroblast maturation in mammals depends on organelle clearance, less is known about mechanisms regulating this clearance throughout terminal erythropoiesis. Here, we studied the effect of TSPO1 downregulation and the action of Ro5-4864, a drug ligand known to bind to the TSPO/VDAC complex interface, in ex vivo human terminal erythropoiesis. We found that both treatments delay mitochondrial clearance, a process associated with reduced levels of the PINK1 protein, which is a key protein triggering canonical mitophagy. We also observed that TSPO1 downregulation blocks erythroblast maturation at the orthochromatic stage, decreases the enucleation rate, and increases cell death. Interestingly, TSPO1 downregulation does not modify reactive oxygen species (ROS) production nor intracellular adenosine triphosphate (ATP) levels. Ro5-4864 treatment recapitulates these phenotypes, strongly suggesting an active role of the TSPO/VDAC complex in selective mitophagy throughout human erythropoiesis. The present study links the function of the TSPO/VDAC complex to the PINK1/Parkin-dependent mitophagy induction during terminal erythropoiesis, leading to the proper completion of erythroid maturation.
转位蛋白（TSPO）和电压依赖性阴离子通道（VDAC）是在外膜线粒体形成大分子复合物的两种蛋白质，涉及多种功能。具体来说，这些蛋白质被描述为通过非红细胞永生化细胞系中的选择性自噬来调节受损线粒体的清除。尽管已经充分证实哺乳动物红细胞成熟依赖于细胞器的清除，但对于调节整个红细胞生成末期的清除的机制知之甚少。在这里，我们研究了 TSPO1 下调和 Ro5-4864 的作用，Ro5-4864 是一种已知与 TSPO/VDAC 复合物界面结合的药物配体，在体外人类终末红细胞生成中的作用。我们发现，这两种处理都延迟了线粒体的清除，这一过程与 PINK1 蛋白水平降低有关，PINK1 蛋白是触发经典自噬的关键蛋白。我们还观察到 TSPO1 下调会阻止正染质期的红细胞成熟，降低去核率，并增加细胞死亡。有趣的是，TSPO1 下调不会改变活性氧（ROS）的产生或细胞内三磷酸腺苷（ATP）的水平。Ro5-4864 处理再现了这些表型，强烈表明 TSPO/VDAC 复合物在整个人类红细胞生成中的选择性自噬中发挥着积极作用。本研究将 TSPO/VDAC 复合物的功能与 PINK1/Parkin 依赖性自噬诱导联系起来，在终末红细胞生成过程中导致红细胞成熟的正常完成。
