Human FAM173A is a mitochondrial lysine-specific methyltransferase that targets adenine nucleotide translocase and affects mitochondrial respiration
Human FAM173A is a mitochondrial lysine-specific methyltransferase that targets adenine nucleotide translocase and affects mitochondrial respiration
复制标题
DOI：
10.1074/jbc.ra119.009045
复制
发表时间：
2019-08-02
影响因子：
4.8
通讯作者：
Falnes, Pal O.
中科院分区：
文献类型：
--
作者：
Malecki, Jedrzej;Willemen, Hanneke L. D. M.;Falnes, Pal O.
赖氨酸甲基化是核蛋白和细胞质蛋白的常见翻译后修饰，但也存在于线粒体中。最近发现，具有序列相似性的人类蛋白质家族 173 成员 B (FAM173B) 是一种靶向线粒体 ATP 合酶 (ATPSc) c 亚基的线粒体赖氨酸 (K) 特异性甲基转移酶 (KMT)，因此被更名为 ATPSc-KMT。我们在这里着手研究其尚未表征的旁系同源物 FAM173A 的生化功能。我们证明 FAM173A 定位于线粒体，由部分保留在成熟蛋白中的非规范靶向序列介导。使用甲基赖氨酸特异性抗体进行的免疫印迹分析表明，FAM173A 敲除 (KO) 会消除人类细胞中单个线粒体蛋白的赖氨酸甲基化。质谱分析鉴定出该蛋白为腺嘌呤核苷酸转位酶 (ANT)，由两个高度相似的亚型 ANT2 和 ANT3 代表。我们发现ANT的Lys-52位点发生甲基化，之前报道该位点是三甲基化的。用 WT 或酶死 FAM173A 补充 KO 细胞表明，FAM173A 的酶活性是 ANT 在 Lys-52 处发生甲基化所必需的。在人类细胞和大鼠器官中，Lys-52 均被三甲基化，表明这种修饰是组成性的，而不是调节性和动态的。此外，与 FAM173A 充足的细胞相比，FAM173A 缺陷的细胞显示线粒体呼吸增加。总之，我们证明FAM173A是长期以来寻找的负责ANT Lys-52甲基化的KMT，并指出了Lys-52甲基化在ANT中的功能意义。根据既定的 KMT 命名规则，我们建议将 FAM173A 重命名为 ANT-KMT（基因名称 ANTKMT）。
Lysine methylation is a common posttranslational modification of nuclear and cytoplasmic proteins but is also present in mitochondria. The human protein denoted family with sequence similarity 173 member B (FAM173B) was recently uncovered as a mitochondrial lysine (K)-specific methyltransferase (KMT) targeting the c-subunit of mitochondrial ATP synthase (ATPSc), and was therefore renamed ATPSc-KMT. We here set out to investigate the biochemical function of its yet uncharacterized paralogue FAM173A. We demonstrate that FAM173A localizes to mitochondria, mediated by a noncanonical targeting sequence that is partially retained in the mature protein. Immunoblotting analysis using methyllysine-specific antibodies revealed that FAM173A knock-out (KO) abrogates lysine methylation of a single mitochondrial protein in human cells. Mass spectrometry analysis identified this protein as adenine nucleotide translocase (ANT), represented by two highly similar isoforms ANT2 and ANT3. We found that methylation occurs at Lys-52 of ANT, which was previously reported to be trimethylated. Complementation of KO cells with WT or enzyme-dead FAM173A indicated that the enzymatic activity of FAM173A is required for ANT methylation at Lys-52 to occur. Both in human cells and in rat organs, Lys-52 was exclusively trimethylated, indicating that this modification is constitutive, rather than regulatory and dynamic. Moreover, FAM173A-deficient cells displayed increased mitochondrial respiration compared with FAM173A-proficient cells. In summary, we demonstrate that FAM173A is the long-sought KMT responsible for ANT methylation at Lys-52, and point out the functional significance of Lys-52 methylation in ANT. Based on the established naming nomenclature for KMTs, we propose to rename FAM173A to ANT-KMT (gene name ANTKMT).