bims-tofagi 2025-08-31 papers

Issue of 2025–08–31
five papers selected by
Michele Frison, University of Cambridge

Sci Adv. 2025 Aug 29. 11(35): eady0240

Putative PINK1/Parkin activators lower the threshold for mitophagy by sensitizing cells to mitochondrial stress.

William M Rosencrans, Ryan W Lee, Logan McGraw, Ian Horsburgh, Ting-Yu Wang, Baiyi Quan, Diana Huynh, Jennifer A Johnston, David C Chan, Tsui-Fen Chou.

The PINK1/Parkin pathway targets damaged mitochondria for degradation via mitophagy. Genetic evidence implicates impaired mitophagy in Parkinson's disease, making its pharmacological enhancement a promising therapeutic strategy. Here, we characterize two mitophagy activators: a novel Parkin activator, FB231, and the reported PINK1 activator MTK458. Both compounds lower the threshold for mitochondrial toxins to induce PINK1/Parkin-mediated mitophagy. However, global proteomics revealed that FB231 and MTK458 independently induce mild mitochondrial stress, resulting in impaired mitochondrial function and activation of the integrated stress response, effects that result from PINK1/Parkin-independent off-target activities. We find that these compounds impair mitochondria by distinct mechanisms and synergistically decrease mitochondrial function and cell viability in combination with classical mitochondrial toxins. Our findings support a model whereby weak or "silent" mitochondrial toxins potentiate other mitochondrial stressors, enhancing PINK1/Parkin-mediated mitophagy. These insights highlight important considerations for therapeutic strategies targeting mitophagy activation in Parkinson's disease.

DOI: https://doi.org/10.1126/sciadv.ady0240

Autophagy. 2025 Sep 01. 1-18

PRMT1 (protein arginine methyltransferase 1) is essential for neuromuscular junction and mitochondrial homeostasis via mitophagy regulation.

Ju-Hyeon Bae, Chang-Lim You, Yideul Jeong, June Kim, Jinwoo Lee, Hyeon-Ju Jeong, Hyebeen Kim, Tuan Anh Vuong, Youngdae Gwon, Gyu-Un Bae, Jong-Sun Kang.

The neuromuscular junction (NMJ) is essential for transmitting neural stimulus to muscles, triggering muscle contraction. Mitochondria are enriched in NMJ to support the energy needs required for neuromuscular function and stability. Thus, maintaining mitochondrial homeostasis through the clearance of damaged mitochondria, a process known as mitophagy, is vital for preserving neuromuscular health. Here, we highlight the crucial role of muscle PRMT1 in maintaining NMJ and mitochondrial homeostasis via mitophagy regulation. PRMT1 is distinctively expressed in myofibers, accumulating in the postsynaptic area, with its levels upregulated in denervated muscles. PRMT1-ablated muscles displayed disrupted NMJs and an accumulation of abnormal mitochondria, accompanied by increased mitochondrial oxidative stress. Additionally, prmt1 depletion in muscles specifically impaired TBK1 (TANK binding kinase 1)-OPTN (optineurin)-mediated mitophagy. Overall, our findings suggest that PRMT1 plays a critical role in maintaining NMJ and mitochondrial health by regulating selective mitophagy through TBK1-OPTN.Abbreviations: ADMA: asymmetric arginine dimethylation; BTX: α-bungarotoxin; EDL: extensor digitorum longus; FDB: flexor digitorum brevis; GAS: gastrocnemius; NMJ: Neuromuscular junction; Mko: mice with muscle-specific prmt1 ablation; MTOR: mechanistic target of rapamycin kinase; OPTN: optineurin; PRMT1: protein arginine methyltransferase 1; SA: sodium arsenate; SNI: sciatic nerve crush injury; Sol: soleus; SQSTM1/p62: sequestosome 1; TBK1: TANK binding kinase 1; TOMM20: translocase of outer mitochondrial membrane 20; TA: tibialis anterior; VDAC1: voltage dependent anion channel 1.

Keywords: Mitophagy; PRMT1; TBK1; neuromuscular junction; skeletal muscle

DOI: https://doi.org/10.1080/15548627.2025.2551477

J Mol Biol. 2025 Aug 19. pii: S0022-2836(25)00463-2. [Epub ahead of print] 169397

Complex Conformational Interplay for Parkin Activation is Revealed by 19F NMR Spectroscopy.

Elizabeth M Connelly, Gary S Shaw.

Parkin is a 52 kDa RING-Between-RING E3 ligase that ubiquitinates proteins at the outer mitochondrial membrane in response to oxidative stress. Part of a neuroprotective pathway, over 100 mutations in the PRKN gene have been associated with Early Onset Parkinson's Disease. To be fully active parkin requires interaction with phosphorylated ubiquitin and phosphorylation of its N-terminal Ubl domain, both dependent on the PINK1 kinase. Along with recruitment of an E2 ∼ Ubiquitin conjugate these events form a ∼90 kDa complex, undergoing a series of conformational changes that regulate transthiolation of ubiquitin from the E2 enzyme to the catalytic domain in parkin (Rcat) prior to substrate labeling. Numerous crystal and NMR structures have captured snapshots of parkin activation and its catalytic mechanism, yet questions surrounding the relative abundance, timing and interplay of parkin conformations remain. Further, most studies use truncated versions of the E3 ligase that may hide details of conformational dependencies. To examine parkin through its activation cycle from inactive (autoinhibited) to E2 ∼ Ubiquitin binding states we incorporated 5-19F-tryptophan into the full-length enzyme and used 19F NMR spectroscopy to identify structural and dynamics changes. Using chemical shift perturbation and T2 analysis, we show that phosphorylation of parkin leads to a population of unbound and bound forms of the phosphorylated Ubl domain and that release of the catalytic Rcat domain is dependent upon E2 ∼ Ub conjugate binding. This study shows the unique abilities of 19F NMR spectroscopy to provide details of the structural rearrangements required for catalysis for the large E3 ligase parkin.

Keywords: NMR spectroscopy; conformational change; dynamics; protein structure; ubiquitination

DOI: https://doi.org/10.1016/j.jmb.2025.169397

Autophagy Rep. 2025 ;4(1): 2547194

During Aspergillus nidulans nitrogen-limited biofilm formation, mitophagy is independent of mitochondrial fission.

Hari Krishnan Balasubramanian, Stephen A Osmani.

During chronic infections, biofilms are resistant to both antimicrobial agents as well as the host immune system, often giving rise to recalcitrant persister cells with reduced mitochondrial function rendering biofilm infections difficult to cure. How mitochondrial dynamics and fate are regulated during fungal biofilm formation is poorly understood. In this study, we used live cell microscopy to track mitochondrial morphology during Aspergillus nidulans in vitro biofilm formation. We show that mitochondria undergo fragmentation during early biofilm development, and that externally induced oxidative stress similarly induces mitochondrial fragmentation, indicating a role for redox regulation in this process. Deletion of core components of the mitochondrial fission machinery resulted in a swollen mitochondrial phenotype. Mitochondria in the fission-mutant strains are known not to complete fragmentation in response to externally induced oxidative stress, and we show that this results in a "beads on a string" phenotype. We further show that mitochondria remain unfragmented during biofilm formation in the fission-mutant strains, although other biofilm cellular modifications, like disassembly of microtubules, are unaffected. We report that mitophagy is triggered during biofilm development in nitrogen-limiting conditions independently of mitochondrial fission. This indicates mitochondrial fission is dispensable for mitophagy during biofilm development with limiting nitrogen. We further note that general autophagy, but notably not mitophagy, is triggered during biofilm development in carbon-limiting conditions, demonstrating differential regulation of mitochondrial fate in response to specific nutritional limitations during fungal biofilm formation.

Keywords: Aspergillus nidulans; autophagy; biofilm formation; carbon; mitochondrial fission; mitophagy; nitrogen; redox regulation

DOI: https://doi.org/10.1080/27694127.2025.2547194

J Neurochem. 2025 Aug;169(8): e70205

Impact of O-GlcNAcylation Elevation on Mitophagy and Glia in the Dentate Gyrus.

Joshua Kramer, Sarah Fu, Xiaosen Ouyang, Eric Rohwer, John C Chatham, Martin E Young, Victor Darley-Usmar, Jianhua Zhang.

O-GlcNAcylation is a dynamic and reversible protein posttranslational modification of serine or threonine residues which modulates the activity of transcriptional and signaling pathways and controls cellular responses to metabolic and inflammatory stressors. We and others have shown that O-GlcNAcylation has the potential to regulate autophagy and mitophagy to play a critical role in mitochondrial quality control, but this has not been assessed in vivo in the brain. This is important since mitochondrial dysfunction contributes to the development of neurodegenerative diseases. We used mito-QC reporter mice to assess mitophagy in diverse cells in the dentate gyrus in response to pharmacological inhibition of O-GlcNAcase (OGA) with thiamet G which leads to elevation of protein O-GlcNAcylation. We demonstrate that mitophagy occurs predominantly in the GFAP-positive astrocytes and is significantly decreased in response to elevated O-GlcNAcylation. Furthermore, with increased O-GlcNAcylation, the levels of astrocyte markers GFAP and S100B, and the microglial cell marker IBA1, decreased in the dentate gyrus, while the levels of microglial cell marker TMEM119 were increased, indicating significant changes in glia homeostasis. These results provide strong evidence of the regulation of mitophagy and glia signatures by the O-GlcNAc pathway.

Keywords: O‐GlcNAc; astrocyte; hippocampus; microglia; mitophagy

DOI: https://doi.org/10.1111/jnc.70205