Life Science Unit, School of Medical Sciences, University of Fukui, Fukui 910-1193, Japan; Life Science Innovation Center, University of Fukui, Fukui 910-1193, Japan.
Molecular Neuroscience Unit, School of Medical Sciences, University of Fukui, Fukui 910-1193, Japan.
Biochim Biophys Acta Mol Cell Res. 2020 Oct;1867(10):118792. doi: 10.1016/j.bbamcr.2020.118792. Epub 2020 Jul 2.
Human Mpv17-like protein (M-LPH/Mpv17L) is thought to play a role in minimizing mitochondrial dysfunction caused by mitochondrial DNA (mtDNA) damage. We have recently demonstrated that, in addition to an increase of mtDNA damage, M-LPH-knockout (M-LPH-KO) in HepG2 cells causes a significant reduction of mitochondrial transcription factor A (TFAM) protein, an essential factor for mtDNA maintenance, along with an increase in its phosphorylation. These intracellular changes suggested an association of M-LPH with the cAMP/PKA signaling pathway, as selective degradation of TFAM by mitochondrial protease is driven by protein kinase A (PKA)-dependent phosphorylation. In the present study, we observed that M-LPH-KO in HepG2 cells caused an increase in the level of mitochondrial cAMP and a reduction of total cellular cyclic nucleotide phosphodiesterase (PDE) activity. In vitro-synthesized M-LPH showed PDE activity, which was inhibited by IBMX, a non-selective inhibitor of PDE. Furthermore, M-LPH-KO promoted PKA-dependent phosphorylation of some mitochondrial proteins. Taken together, the present findings suggest that M-LPH, which has structural features atypical of PDE family members, might be a novel human PDE involved in cAMP/PKA signaling in the mitochondrial matrix.
人 Mpv17 样蛋白（M-LPH/Mpv17L）被认为在最小化线粒体 DNA（mtDNA）损伤引起的线粒体功能障碍方面发挥作用。我们最近证明，除了 mtDNA 损伤增加外，HepG2 细胞中的 M-LPH 敲除（M-LPH-KO）还导致线粒体转录因子 A（TFAM）蛋白的显著减少，TFAM 是 mtDNA 维持的必需因素，同时其磷酸化增加。这些细胞内变化表明 M-LPH 与 cAMP/PKA 信号通路有关，因为线粒体蛋白酶对 TFAM 的选择性降解是由蛋白激酶 A（PKA）依赖性磷酸化驱动的。在本研究中，我们观察到 HepG2 细胞中的 M-LPH-KO 导致线粒体 cAMP 水平增加和总细胞环核苷酸磷酸二酯酶（PDE）活性降低。体外合成的 M-LPH 显示 PDE 活性，该活性被 PDE 的非选择性抑制剂 IBMX 抑制。此外，M-LPH-KO 促进了一些线粒体蛋白的 PKA 依赖性磷酸化。总之，这些发现表明，具有非典型 PDE 家族成员结构特征的 M-LPH 可能是一种新型人类 PDE，参与线粒体基质中的 cAMP/PKA 信号转导。
