Department of Biochemistry and Molecular Biology, Chosun University School of Medicine, 309 Pilmoon-Daero, Dong-Gu, Gwangju, 61452, Republic of Korea.
Gwangju Center, Korea Basic Science Institute, 77 Yongbong-ro, Buk-gu, Gwangju, 61168, Republic of Korea.
Biochem Biophys Res Commun. 2019 Oct 8;518(1):80-86. doi: 10.1016/j.bbrc.2019.08.011. Epub 2019 Aug 14.
Noxa is a weak apoptosis activator consisting of a BH3 domain and a mitochondrial-targeting domain (MTD). BH3 binds Mcl-1 and Bcl2A1 and inactivates their anti-apoptotic activities, while MTD delivers BH3 to mitochondria. Previously we revealed that MTD may also function as an inducer of necrosis via conjugation with octa-arginine, which induces cytosolic Ca influx from mitochondria. However, the mechanism(s) underlying this process has not been elucidated yet. Here, we show that calcium influx induced by an MTD peptide fused with octa-arginine residue (R8:MTD) originates not only from mitochondria but also from the extracellular space. However, calcium spikes were not sufficient for necrosis. R8:MTD induced mitochondrial permeability transition pore opening, fragmentation, and swelling. These mitochondrial events induced by MTD appeared to be necessary for necrosis induction, since DIDS, a VDAC inhibitor, inhibited the mitochondrial swelling and cell death induced by MTD. We show that R8:MTD disrupted endoplasmic reticulum (ER) structures but not peroxisomes or Golgi, indicating that R8:MTD causes necrosis by inducing ER events as well.
Noxa 是一种弱凋亡激活剂，由 BH3 结构域和线粒体靶向结构域（MTD）组成。BH3 结合 Mcl-1 和 Bcl2A1 并使其失活，而 MTD 将 BH3 递送到线粒体。以前我们发现 MTD 还可以通过与八聚精氨酸的结合作为坏死诱导剂发挥作用，这种结合会诱导来自线粒体的细胞质 Ca2+内流。然而，这个过程的机制尚未阐明。在这里，我们表明，与八聚精氨酸残基融合的 MTD 肽（R8:MTD）诱导的钙内流不仅来自线粒体，也来自细胞外空间。然而，钙峰对于坏死并不足够。R8:MTD 诱导线粒体通透性转换孔（MPTP）打开、碎裂和肿胀。MTD 诱导的这些线粒体事件似乎对于坏死诱导是必要的，因为 VDAC 抑制剂 DIDS 抑制了 MTD 诱导的线粒体肿胀和细胞死亡。我们表明，R8:MTD 破坏了内质网（ER）结构，但不破坏过氧化物酶体或高尔基体，表明 R8:MTD 通过诱导 ER 事件引起坏死。
