bims-tofagi 2024-07-14 papers

on Mitophagy

Issue of 2024‒07‒14
six papers selected by
Michele Frison, University of Cambridge and Aitor Martínez Zarate, Euskal Herriko Unibertsitatea

PINK1 regulated mitophagy is evident in skeletal muscles.
Dual-localized PPTC7 limits mitophagy through proximal and dynamic interactions with BNIP3 and NIX.
PPTC7 antagonizes mitophagy by promoting BNIP3 and NIX degradation via SCFFBXL4.
Compartmentalized mitochondrial ferroptosis converges with optineurin-mediated mitophagy to impact airway epithelial cell phenotypes and asthma outcomes.
Differential distribution of PINK1 and Parkin in the primate brain implies distinct roles.
BL-918 activates PINK1/Parkin signaling pathway to ameliorate the progression of Parkinson's disease.

Autophagy Rep. 2024 Mar 11. 3(1): 2326402

PINK1 regulated mitophagy is evident in skeletal muscles.

Francois Singh, Lea Wilhelm, Alan R Prescott, Kevin Ostacolo, Jin-Feng Zhao, Margret H Ogmundsdottir, Ian G Ganley.

  PINK1, mutated in familial forms of Parkinson's disease, initiates mitophagy following mitochondrial depolarization. However, it is difficult to monitor this pathway physiologically in mice as loss of PINK1 does not alter basal mitophagy levels in most tissues. To further characterize this pathway in vivo, we used mito-QC mice in which loss of PINK1 was combined with the mitochondrial-associated POLGD257A mutation. We focused on skeletal muscle as gene expression data indicates that this tissue has the highest PINK1 levels. We found that loss of PINK1 in oxidative hindlimb muscle significantly reduced mitophagy. Of interest, the presence of the POLGD257A mutation, while having a minor effect in most tissues, restored levels of muscle mitophagy caused by the loss of PINK1. Although our observations highlight that multiple mitophagy pathways operate within a single tissue, we identify skeletal muscle as a tissue of choice for the study of PINK1-dependant mitophagy under basal conditions.

Keywords:  PINK1; POLG; Parkinson’s; mitophagy; muscle; mutator

DOI:  https://doi.org/10.1080/27694127.2024.2326402
Life Sci Alliance. 2024 Sep;pii: e202402765. [Epub ahead of print]7(9):

Dual-localized PPTC7 limits mitophagy through proximal and dynamic interactions with BNIP3 and NIX.

Lianjie Wei, Mehmet Oguz Gok, Jordyn D Svoboda, Keri-Lyn Kozul, Merima Forny, Jonathan R Friedman, Natalie M Niemi.

PPTC7 is a mitochondrial-localized phosphatase that suppresses BNIP3- and NIX-mediated mitophagy, but the mechanisms underlying this regulation remain ill-defined. Here, we demonstrate that loss of PPTC7 upregulates BNIP3 and NIX post-transcriptionally and independent of HIF-1α stabilization. Loss of PPTC7 prolongs the half-life of BNIP3 and NIX while blunting their accumulation in response to proteasomal inhibition, suggesting that PPTC7 promotes the ubiquitin-mediated turnover of BNIP3 and NIX. Consistently, overexpression of PPTC7 limits the accumulation of BNIP3 and NIX protein levels, which requires an intact catalytic motif but is surprisingly independent of its targeting to mitochondria. Consistently, we find that PPTC7 is dual-localized to the outer mitochondrial membrane and the matrix. Importantly, anchoring PPTC7 to the outer mitochondrial membrane is sufficient to blunt BNIP3 and NIX accumulation, and proximity labeling and fluorescence co-localization experiments demonstrate that PPTC7 dynamically associates with BNIP3 and NIX within the native cellular environment. Collectively, these data reveal that a fraction of PPTC7 localizes to the outer mitochondrial membrane to promote the proteasomal turnover of BNIP3 and NIX, limiting basal mitophagy.

DOI: https://doi.org/10.26508/lsa.202402765
EMBO Rep. 2024 Jul 11.

PPTC7 antagonizes mitophagy by promoting BNIP3 and NIX degradation via SCFFBXL4.

Giang Thanh Nguyen-Dien, Brendan Townsend, Prajakta Gosavi Kulkarni, Keri-Lyn Kozul, Soo Siang Ooi, Denaye N Eldershaw, Saroja Weeratunga, Meihan Liu, Mathew Jk Jones, S Sean Millard, Dominic Ch Ng, Michele Pagano, Alexis Bonfim-Melo, Tobias Schneider, David Komander, Michael Lazarou, Brett M Collins, Julia K Pagan.

  Mitophagy must be carefully regulated to ensure that cells maintain appropriate numbers of functional mitochondria. The SCFFBXL4 ubiquitin ligase complex suppresses mitophagy by controlling the degradation of BNIP3 and NIX mitophagy receptors, and FBXL4 mutations result in mitochondrial disease as a consequence of elevated mitophagy. Here, we reveal that the mitochondrial phosphatase PPTC7 is an essential cofactor for SCFFBXL4-mediated destruction of BNIP3 and NIX, suppressing both steady-state and induced mitophagy. Disruption of the phosphatase activity of PPTC7 does not influence BNIP3 and NIX turnover. Rather, a pool of PPTC7 on the mitochondrial outer membrane acts as an adaptor linking BNIP3 and NIX to FBXL4, facilitating the turnover of these mitophagy receptors. PPTC7 accumulates on the outer mitochondrial membrane in response to mitophagy induction or the absence of FBXL4, suggesting a homoeostatic feedback mechanism that attenuates high levels of mitophagy. We mapped critical residues required for PPTC7-BNIP3/NIX and PPTC7-FBXL4 interactions and their disruption interferes with both BNIP3/NIX degradation and mitophagy suppression. Collectively, these findings delineate a complex regulatory mechanism that restricts BNIP3/NIX-induced mitophagy.

Keywords:  BNIP3; FBXL4; Mitophagy; NIX; PPTC7

DOI:  https://doi.org/10.1038/s44319-024-00181-y
Nat Commun. 2024 Jul 10. 15(1): 5818

Compartmentalized mitochondrial ferroptosis converges with optineurin-mediated mitophagy to impact airway epithelial cell phenotypes and asthma outcomes.

Kazuhiro Yamada, Claudette St Croix, Donna B Stolz, Yulia Y Tyurina, Vladimir A Tyurin, Laura R Bradley, Alexander A Kapralov, Yanhan Deng, Xiuxia Zhou, Qi Wei, Bo Liao, Nobuhiko Fukuda, Mara Sullivan, John Trudeau, Anuradha Ray, Valerian E Kagan, Jinming Zhao, Sally E Wenzel.

A stable mitochondrial pool is crucial for healthy cell function and survival. Altered redox biology can adversely affect mitochondria through induction of a variety of cell death and survival pathways, yet the understanding of mitochondria and their dysfunction in primary human cells and in specific disease states, including asthma, is modest. Ferroptosis is traditionally considered an iron dependent, hydroperoxy-phospholipid executed process, which induces cytosolic and mitochondrial damage to drive programmed cell death. However, in this report we identify a lipoxygenase orchestrated, compartmentally-targeted ferroptosis-associated peroxidation process which occurs in a subpopulation of dysfunctional mitochondria, without promoting cell death. Rather, this mitochondrial peroxidation process tightly couples with PTEN-induced kinase (PINK)-1(PINK1)-Parkin-Optineurin mediated mitophagy in an effort to preserve the pool of functional mitochondria and prevent cell death. These combined peroxidation processes lead to altered epithelial cell phenotypes and loss of ciliated cells which associate with worsened asthma severity. Ferroptosis-targeted interventions of this process could preserve healthy mitochondria, reverse cell phenotypic changes and improve disease outcomes.

DOI: https://doi.org/10.1038/s41467-024-50222-2
Neural Regen Res. 2025 Apr 01. 20(4): 1124-1134

Differential distribution of PINK1 and Parkin in the primate brain implies distinct roles.

Yanting Liu, Wei Huang, Jiayi Wen, Xin Xiong, Ting Xu, Qi Wang, Xiusheng Chen, Xianxian Zhao, Shihua Li, Xiaojiang Li, Weili Yang.

JOURNAL/nrgr/04.03/01300535-202504000-00028/figure1/v/2024-07-06T104127Z/r/image-tiff The vast majority of in vitro studies have demonstrated that PINK1 phosphorylates Parkin to work together in mitophagy to protect against neuronal degeneration. However, it remains largely unclear how PINK1 and Parkin are expressed in mammalian brains. This has been difficult to address because of the intrinsically low levels of PINK1 and undetectable levels of phosphorylated Parkin in small animals. Understanding this issue is critical for elucidating the in vivo roles of PINK1 and Parkin. Recently, we showed that the PINK1 kinase is selectively expressed as a truncated form (PINK1-55) in the primate brain. In the present study, we used multiple antibodies, including our recently developed monoclonal anti-PINK1, to validate the selective expression of PINK1 in the primate brain. We found that PINK1 was stably expressed in the monkey brain at postnatal and adulthood stages, which is consistent with the findings that depleting PINK1 can cause neuronal loss in developing and adult monkey brains. PINK1 was enriched in the membrane-bound fractionations, whereas Parkin was soluble with a distinguishable distribution. Immunofluorescent double staining experiments showed that PINK1 and Parkin did not colocalize under physiological conditions in cultured monkey astrocytes, though they did colocalize on mitochondria when the cells were exposed to mitochondrial stress. These findings suggest that PINK1 and Parkin may have distinct roles beyond their well-known function in mitophagy during mitochondrial damage.

DOI: https://doi.org/10.4103/NRR.NRR-D-23-01140
J Biol Chem. 2024 Jul 09. pii: S0021-9258(24)02044-1. [Epub ahead of print] 107543

BL-918 activates PINK1/Parkin signaling pathway to ameliorate the progression of Parkinson's disease.

Yi Wang, Siyuan Luo, Huili Su, Zhimeng Wang, Ling Chu, Conggang Zhang.

  The pathogenesis of Parkinson's disease (PD) has been associated with mitochondrial dysfunction. Given that the PINK1/Parkin pathway governs mitochondrial quality control by inducing mitophagy to remove damaged mitochondria, therapeutic approaches to activate PINK1/Parkin-mediated mitophagy have the potential in the treatment of PD. Here, we have identified a new small molecule, BL-918, as an inducer of mitophagy via activating the PINK1/Parkin pathway. BL-918 triggers PINK1 accumulation and Parkin mitochondrial translocation to initiate PINK1/Parkin-mediated mitophagy. We found that mitochondrial membrane potential and mitochondrial permeability transition (mPT) pore were involved in BL-918-induced PINK1/Parkin pathway activation. Moreover, we showed that BL-918 mitigated PD progression in MPTP-induced PD mice in a PINK1-dependent manner. Our results unravel a new activator of the PINK1/Parkin signaling pathway and provide a potential strategy for the treatment of PD and other diseases with dysfunctional mitochondria.

Keywords:  Mitochondrial quality control; Mitophagy; PINK1; Parkin; Parkinson’s disease

DOI:  https://doi.org/10.1016/j.jbc.2024.107543