Jo Yongsam, Kim Byeongmo, Shin Deug Y
Department of Microbiology, Dankook University College of Medicine, Cheonan, South Chungcheong 31116, Republic of Korea.
Exp Ther Med. 2021 Nov;22(5):1195. doi: 10.3892/etm.2021.10629. Epub 2021 Aug 20.
Previously, we reported on a novel anti-apoptotic E3 ubiquitin ligase, apoptosis-resistant E3 ubiquitin protein ligase 1 (AREL1), that ubiquitinates inhibitors of apoptosis proteins antagonists. The present study demonstrated that AREL1 ubiquitinated Metaxin 2 (MTX2), which was involved in TNF-induced necroptosis. MTX2 has been identified as a protein that belongs to the Metaxin family. It interacts with another Metaxin protein, Metaxin 1 (MTX1), which is localized in the outer membrane of mitochondria, and is involved in TNF-induced necroptosis. This study found that AREL1 interacted with MTX2, but not MTX1, while the amino-terminal domain of MTX2 interacted with MTX1, AREL1 interacted with the carboxyl-terminal domain of MTX2. Furthermore, AREL1 expression led to a decrease in the protein expression of MTX2, but not MTX1. However, a mutant form of AREL1, AREL1C790A, which is deficient for E3 activity, did not cause MTX2 degradation. Moreover, the protein levels of MTX2 were increased by AREL1 knockdown. Therefore, these results implied that AREL1 ubiquitinates and promotes the degradation of MTX2. The expression of MTX2, together with MTX1, enhanced TNF-induced necroptosis. However, AREL1 inhibited necroptosis even in cells expressing Metaxin proteins. Therefore, these results suggested that the inhibition of AREL1-dependent ubiquitination of MTX2 could be beneficial to sensitize tumor cells to TNF-induced necroptosis.
此前，我们报道了一种新型抗凋亡E3泛素连接酶——抗凋亡E3泛素蛋白连接酶1（AREL1），它可使凋亡蛋白拮抗剂的抑制剂发生泛素化。本研究表明，AREL1使参与肿瘤坏死因子（TNF）诱导的坏死性凋亡的变轴蛋白2（MTX2）发生泛素化。MTX2已被鉴定为属于变轴蛋白家族的一种蛋白质。它与另一种变轴蛋白——定位于线粒体外膜且参与TNF诱导的坏死性凋亡的变轴蛋白1（MTX1）相互作用。本研究发现，AREL1与MTX2相互作用，但不与MTX1相互作用，而MTX2的氨基末端结构域与MTX1相互作用，AREL1与MTX2的羧基末端结构域相互作用。此外，AREL1的表达导致MTX2的蛋白表达下降，但不影响MTX1。然而，缺乏E3活性的AREL1突变体形式AREL1C790A不会导致MTX2降解。此外，敲低AREL1会使MTX2的蛋白水平升高。因此，这些结果表明AREL1使MTX2发生泛素化并促进其降解。MTX2与MTX1共同表达可增强TNF诱导的坏死性凋亡。然而，即使在表达变轴蛋白的细胞中，AREL1也能抑制坏死性凋亡。因此，这些结果表明，抑制AREL1依赖的MTX2泛素化可能有助于使肿瘤细胞对TNF诱导的坏死性凋亡敏感。
