PDF(Pubmed)
Abstract：
Abcb10 is a mitochondrial membrane protein involved in hemoglobinization of red cells. Abcb10 topology and ATPase domain localization suggest it exports a substrate, likely biliverdin, out of mitochondria that is necessary for hemoglobinization. In this study, we generated Abcb10 deletion cell lines in both mouse murine erythroleukemia and human erythroid precursor human myelogenous leukemia (K562) cells to better understand the consequences of Abcb10 loss. Loss of Abcb10 resulted in an inability to hemoglobinize upon differentiation in both K562 and mouse murine erythroleukemia cells with reduced heme and intermediate porphyrins and decreased levels of aminolevulinic acid synthase 2 activity. Metabolomic and transcriptional analyses revealed that Abcb10 loss gave rise to decreased cellular arginine levels, increased transcripts for cationic and neutral amino acid transporters with reduced levels of the citrulline to arginine converting enzymes argininosuccinate synthetase and argininosuccinate lyase. The reduced arginine levels in Abcb10-null cells gave rise to decreased proliferative capacity. Arginine supplementation improved both Abcb10-null proliferation and hemoglobinization upon differentiation. Abcb10-null cells showed increased phosphorylation of eukaryotic translation initiation factor 2 subunit alpha, increased expression of nutrient sensing transcription factor ATF4 and downstream targets DNA damage inducible transcript 3 (Chop), ChaC glutathione specific gamma-glutamylcyclotransferase 1 (Chac1), and arginyl-tRNA synthetase 1 (Rars). These results suggest that when the Abcb10 substrate is trapped in the mitochondria, the nutrient sensing machinery is turned on remodeling transcription to block protein synthesis necessary for proliferation and hemoglobin biosynthesis in erythroid models.
摘要：
Abcb10是参与红细胞血红蛋白化的线粒体膜蛋白。Abcb10拓扑结构和ATP酶结构域定位表明它输出了一个底物，可能是胆绿素,来自血红蛋白化所必需的线粒体。在这项研究中，我们在小鼠鼠红白血病（MEL）和人红系前体人髓性白血病（K562）细胞中产生了Abcb10缺失细胞系，以更好地了解Abcb10丢失的后果。Abcb10的丢失导致K562和MEL细胞分化后无法血红蛋白化，血红素和中间卟啉减少，氨基乙酰丙酸合酶2活性水平降低。代谢组学和转录分析显示，Abcb10丢失导致细胞精氨酸水平降低，阳离子和中性氨基酸转运蛋白的转录物增加，瓜氨酸向精氨酸转化酶精氨酸琥珀酸合成酶和精氨酸琥珀酸裂解酶的水平降低。Abcb10无效细胞中精氨酸水平的降低导致增殖能力降低。精氨酸补充改善了Abcb10无效增殖和分化后的血红蛋白化。Abcb10无效细胞显示真核翻译起始因子2亚基α（eIF2A）的磷酸化增加，营养敏感转录因子ATF4和下游靶DNA损伤诱导型转录物3（Chop）的表达增加，ChaC谷胱甘肽特异性γ-谷氨酰环基转移酶1(Chac1)和精氨酰-tRNA合成酶1(Rars)。这些结果表明，当Abcb10底物被捕获在线粒体中时，在红系模型中，营养感知机制开启重塑转录以阻断增殖和血红蛋白生物合成所必需的蛋白质合成。
