Centre for Innovation in Molecular and Pharmaceutical Sciences (CIMPS), Dr. Reddy's Institute of Life Sciences, University of Hyderabad Campus, Hyderabad 500046, India; Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal, Karnataka 576104, India.
Centre for Innovation in Molecular and Pharmaceutical Sciences (CIMPS), Dr. Reddy's Institute of Life Sciences, University of Hyderabad Campus, Hyderabad 500046, India.
Biochim Biophys Acta Mol Basis Dis. 2023 Aug;1869(6):166718. doi: 10.1016/j.bbadis.2023.166718. Epub 2023 Apr 13.
Adaptability to intracellular or extracellular cues is essential for maintaining cellular homeostasis. Metabolic signals intricately control the morphology and functions of mitochondria by regulating bioenergetics and metabolism. Here, we describe the involvement of PHLPP1, a Ser/Thr phosphatase, in mitochondrial homeostasis. Microscopic analysis showed the enhanced globular structure of mitochondria in PHLPP1-depleted HEK 293T and C2C12 cells, while forced expression of PHLPP1 promoted mitochondrial tubularity. We show that PHLPP1 promoted pro-fusion markers MFN2 and p-DRP1 levels using over-expression and knockdown strategies. Contrastingly, PHLPP1 induced mitochondrial fragmentation by augmenting pro-fission markers, t-DRP1 and pDrp1 upon mitochondrial stress. At the molecular level, PHLPP1 interacted with and caused dephosphorylation of calcineurin, a p-DRP1 phosphatase, under basal conditions. Likewise, PHLPP1 dimerized with PINK1 under basal conditions. However, the interaction of PHLPP1 with both calcineurin and PINK1 was impaired upon CCCP and oligomycin-induced mitochondrial stress. Interestingly, upon mitochondrial membrane depolarization, PHLPP1 promoted PINK1 stabilization and parkin recruitment to mitochondria, and thereby activated the mitophagy machinery providing a molecular explanation for the dual effects of PHLPP1 on mitochondria under different conditions. Consistent with our in-vitro findings, depletion of phlp-2, ortholog of PHLPP1 in C. elegans, led to mitochondrial fission under basal conditions, extended the lifespan of the worms, and enhanced survival of worms subjected to paraquat-induced oxidative stress.
适应细胞内或细胞外的信号对于维持细胞内稳态至关重要。代谢信号通过调节生物能量和代谢来精细控制线粒体的形态和功能。在这里，我们描述了丝氨酸/苏氨酸磷酸酶 PHLPP1 如何参与线粒体的动态平衡。显微镜分析显示，在 PHLPP1 耗尽的 HEK 293T 和 C2C12 细胞中，线粒体呈现增强的球状结构，而 PHLPP1 的强制表达则促进了线粒体的管状结构。我们表明，PHLPP1 通过上调促融合标记物 MFN2 和 p-DRP1 的水平来促进融合。相比之下，PHLPP1 通过增加促分裂标记物 t-DRP1 和 pDrp1 来诱导线粒体碎片化，这是在受到线粒体应激时发生的。在分子水平上，PHLPP1 在基础条件下与钙调神经磷酸酶相互作用并使其去磷酸化，钙调神经磷酸酶是 p-DRP1 的磷酸酶。同样，在基础条件下，PHLPP1 与 PINK1 二聚化。然而，在 CCCP 和寡霉素诱导的线粒体应激下，PHLPP1 与钙调神经磷酸酶和 PINK1 的相互作用受损。有趣的是，在线粒体膜去极化时，PHLPP1 促进 PINK1 的稳定和 parkin 向线粒体的募集，并激活了线粒体自噬机制，为 PHLPP1 在不同条件下对线粒体的双重影响提供了分子解释。与我们的体外研究结果一致，秀丽隐杆线虫中 PHLPP1 的同源物 phlp-2 的耗竭导致基础条件下的线粒体分裂，延长了线虫的寿命，并增强了对线虫遭受百草枯诱导的氧化应激的生存能力。
