Parkin coordinates mitochondrial lipid remodeling to execute mitophagy.
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2022-12
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Abstract
Autophagy has emerged as the prime machinery for implementing organelle quality control. In the context of mitophagy, the ubiquitin E3 ligase Parkin tags impaired mitochondria with ubiquitin to activate autophagic degradation. Although ubiquitination is essential for mitophagy, it is unclear how ubiquitinated mitochondria activate autophagosome assembly locally to ensure efficient destruction. Here, we report that Parkin activates lipid remodeling on mitochondria targeted for autophagic destruction. Mitochondrial Parkin induces the production of phosphatidic acid (PA) and its subsequent conversion to diacylglycerol (DAG) by recruiting phospholipase D2 and activating the PA phosphatase, Lipin-1. The production of DAG requires mitochondrial ubiquitination and ubiquitin-binding autophagy receptors, NDP52 and optineurin (OPTN). Autophagic receptors, via Golgi-derived vesicles, deliver an autophagic activator, EndoB1, to ubiquitinated mitochondria. Inhibition of Lipin-1, NDP52/OPTN, or EndoB1 results in a failure to produce mitochondrial DAG, autophagosomes, and mitochondrial clearance, while exogenous cell-permeable DAG can induce autophagosome production. Thus, mitochondrial DAG production acts downstream of Parkin to enable the local assembly of autophagosomes for the efficient disposal of ubiquitinated mitochondria.
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Lin, Chao-Chieh, Jin Yan, Meghan D Kapur, Kristi L Norris, Cheng-Wei Hsieh, De Huang, Nicolas Vitale, Kah-Leong Lim, et al. (2022). Parkin coordinates mitochondrial lipid remodeling to execute mitophagy. EMBO reports, 23(12). p. e55191. 10.15252/embr.202255191 Retrieved from https://hdl.handle.net/10161/33653.
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Scholars@Duke
Chao-Chieh Lin
Ziqiang Guan
We develop and apply mass spectrometry techniques to address biochemical and biomedical questions that are lipid-related. Research projects include:
1) Structural lipidomics
o Develop and apply high resolution tandem mass spectrometry-based lipidomics for the discovery, structural elucidation and functional study of novel lipids.
2) Elucidation of novel pathways/enzymes of lipid biosynthesis and metabolism
o Genetic, biochemical and MS approaches are employed to identify the substrates and pathways involved in lipid biosynthesis and metabolism
3) Identification of lipid biomarkers of genetic diseases and cancers
o Provide molecular insights into the disease mechanisms, as well as to serve as the diagnostic and prognostic tools of diseases.
Xiao-Fan Wang
The current research in the Wang laboratory mainly focuses on the elucidation of molecular nature and signaling mechanisms associated with the initiation of cellular senescence. In addition, we continue to study changes in tumor microenvironment that promotes tumor progression and metastasis, particularly how tumor cells interact with the immune system. Ultimately, we hope that our studies in these areas to lead to the development of novel therapeutics for the treatment of various types of human cancer.
Jen-Tsan Ashley Chi
We are using functional genomic approaches to investigate the nutrient signaling and stress adaptations of cancer cells when exposed to various nutrient deprivations and microenvironmental stress conditions. Recently, we focus on two areas. First, we are elucidating the genetic determinants and disease relevance of ferroptosis, a newly recognized form of cell death. Second, we have identified the mammalian stringent response pathway which is highly similar to bacterial stringent response, but with some very interesting twists and novel mechanisms.
A. The genetic determinants and disease relevance of ferroptosis
Ferroptosis is a newly recognized form of cell death that is characterized by iron dependency and lipid peroxidation. The importance of ferroptosis is being recognized in many human diseases, including cancers, ischemia injuries, and neurodegeneration. Previously, we have identified the profound cystine addiction of renal cell carcinoma (1), breast cancer cells (2, 3), and ovarian cancer cells (4). Based on the concept that cystine deprivation triggers the ferroptosis due to the unopposed oxidative stresses, we have performed functional genomic screens to identify many novel genetic determinants of ferroptosis. For example, we have found that DNA damage response and ATM kinase regulate ferroptosis via affecting iron metabolism (5). This finding supports the potential of ionizing radiation to trigger DNA damage response and synergize with ferroptosis to treat human cancers. In addition, we found that ferroptosis is highly regulated by cell density. When cells are grown at low density, they are highly susceptible to ferroptosis. In contrast, the same cells become resistant to ferroptosis when grown at high density and confluency. we have found the Hippo pathway effectors TAZ and YAP are responsible for the cell density-dependent ferroptosis (4, 6, 7). Right now, we are pursuing several other novel determinants of ferroptosis that will reveal surprising insights into this new form of cell death.
B. A new stress pathway – mammalian stress response
All living organisms encounter a wide variety of nutrient deprivations and environmental stresses. Therefore, all organisms have developed various mechanisms to respond and promote survival under stress. In bacteria, the main strategy is “stringent response” triggered by the accumulation of the alarmone (p)ppGpp (shortened to ppGpp below) via regulation of its synthetase RelA and its hydrolase SpoT (8). The ppGpp binds to the transcription factor DksA and RNA polymerase to orchestrate extensive transcriptional changes that repress proliferation and promote stress survival (8, 9). While highly conserved among bacteria, the stringent response had not been reported in metazoans. However, a recent study identified Drosophila and human MESH1 (Metazoan SpoT Homolog 1) as the homologs of the ppGpp hydrolase domain of the bacterial SpoT (10). Both MESH1 proteins exhibit ppGpp hydrolase activity, and the deletion of Mesh1 in Drosophila led to a transcriptional response reminiscent of the bacterial stringent response (10). Recently, we have found that the genetic removal of MESH1 in tumor cells triggers extensive transcriptional changes and confers protection against oxidative stress-induced ferroptosis (11). Importantly, MESH1 removal also triggers proliferative arrest and other robust anti-tumor effects. Therefore, MESH1 knockdown leads to both stress survival and proliferation arrest, two cardinal features highly reminiscent of the bacterial stringent response. Therefore, we termed this pathway as “mammalian stringent response” (12). We have found that NADPH is the relevant MESH1 in the contexts of ferroptosis (13). Now, we are investigating how MESH1 removal leads to proliferation of arrests and anti-tumor phenotypes. Furthermore, we have found several other substrates of MESH1. We are investigating their function using culture cells, MESH1 KO mice, and other model organisms.
C. Genomic and single cell RNA analysis of Red Blood Cells
Red blood cells (RBC) are responsible for oxygen delivery to muscles during vigorous exercise. Therefore, many doping efforts focus on increasing RBC number and function to boost athletic performance during competition. For many decades, RBC were thought to be merely identical “sacs of hemoglobin” with no discernable differences due to factors such as age or pre-transfusion storage time. Additionally, because RBC lose their nuclei during terminal differentiation, they were not believed to retain any genetic materials. These long-held beliefs have now been disproven and the results have significant implications for detecting autologous blood transfusion (ABT) doping in athletes. We were among the first to discover that RBCs contain abundant and diverse species of RNAs. Using this knowledge, we subsequently optimized protocols and performed genomic analysis of the RBC transcriptome in sickle cell disease; these results revealed that heterogeneous RBCs could be divided into several subpopulations, which had implications for the mechanisms of malaria resistance. As an extension of these studies, we used high resolution Illumina RNA-Seq approaches to identify hundreds of additional known and novel microRNAs, mRNAs, and other RNA species in RBCs. This dynamic RBC transcriptome represents a significant opportunity to assess the impact that environmental factors (such as pre-transfusion refrigerate storage) on the RBC transcriptome. We have now identified a >10-fold change in miR-720 as well as several other RNA transcripts whose levels are significantly altered by RBC storage (14) which gained significant press coverage. We are pursuing the genomic and single cell analysis of RNA transcriptome in the context of blood doping, sickle cell diseases and other red cell diseases.
1. Tang X, Wu J, Ding CK, Lu M, Keenan MM, Lin CC, et al. Cystine Deprivation Triggers Programmed Necrosis in VHL-Deficient Renal Cell Carcinomas. Cancer Res. 2016;76(7):1892-903.
2. Tang X, Ding CK, Wu J, Sjol J, Wardell S, Spasojevic I, et al. Cystine addiction of triple-negative breast cancer associated with EMT augmented death signaling. Oncogene. 2017;36(30):4379.
3. Lin CC, Mabe NW, Lin YT, Yang WH, Tang X, Hong L, et al. RIPK3 upregulation confers robust proliferation and collateral cystine-dependence on breast cancer recurrence. Cell Death Differ. 2020.
4. Yang WH, Huang Z, Wu J, Ding C-KC, Murphy SK, Chi J-T. A TAZ-ANGPTL4-NOX2 axis regulates ferroptotic cell death and chemoresistance in epithelial ovarian cancer. Molecular Cancer Research. 2019: molcanres.0691.2019.
5. Chen PH, Wu J, Ding CC, Lin CC, Pan S, Bossa N, et al. Kinome screen of ferroptosis reveals a novel role of ATM in regulating iron metabolism. Cell Death Differ. 2019.
6. Yang W-H, Chi J-T. Hippo pathway effectors YAP/TAZ as novel determinants of ferroptosis. Molecular & Cellular Oncology. 2019:1699375.
7. Yang WH, Ding CKC, Sun T, Hsu DS, Chi JT. The Hippo Pathway Effector TAZ Regulates Ferroptosis in Renal Cell Carcinoma Cell Reports. 2019;28(10):2501-8.e4.
8. Potrykus K, Cashel M. (p)ppGpp: still magical? Annu Rev Microbiol. 2008;62:35-51.
9. Kriel A, Bittner AN, Kim SH, Liu K, Tehranchi AK, Zou WY, et al. Direct regulation of GTP homeostasis by (p)ppGpp: a critical component of viability and stress resistance. Mol Cell. 2012;48(2):231-41.
10. Sun D, Lee G, Lee JH, Kim HY, Rhee HW, Park SY, et al. A metazoan ortholog of SpoT hydrolyzes ppGpp and functions in starvation responses. Nat Struct Mol Biol. 2010;17(10):1188-94.
11. Dixon SJ, Lemberg KM, Lamprecht MR, Skouta R, Zaitsev EM, Gleason CE, et al. Ferroptosis: an iron-dependent form of nonapoptotic cell death. Cell. 2012;149(5):1060-72.
12. Ding C-KC, Rose J, Wu J, Sun T, Chen K-Y, Chen P-H, et al. Mammalian stringent-like response mediated by the cytosolic NADPH phosphatase MESH1. bioRxiv. 2018.
13. Ding C-KC, Rose J, Sun T, Wu J, Chen P-H, Lin C-C, et al. MESH1 is a cytosolic NADPH phosphatase that regulates ferroptosis. Nature Metabolism. 2020.
14. Yang WH, Doss JF, Walzer KA, McNulty SM, Wu J, Roback JD, et al. Angiogenin-mediated tRNA cleavage as a novel feature of stored red blood cells. Br J Haematol. 2018.
Tso-Pang Yao
My laboratory studies the regulatory functions of protein acetylation in cell signaling and human disease. We focus on a class of protein deacetylases, HDACs, which we have discovered versatile functions beyond gene transcription. We wish to use knowledge of HDAC biology to develop smart and rational clinical strategies for HDAC inhibitors, a growing class of compounds that show potent anti-tumor and other clinically relevant activities. Currently, there two major research major areas in the laboratory: aging/age-related disease, and mitochondrial biology/cancer metabolism.
(1) Quality control (QC) autophagy in aging and neurodegenerative disease. The accumulation of damaged proteins and mitochondria is prominently linked to aging and age-associated disease, including neurodegeneration, metabolic disorders and cancer. Autophagy has emerged as specialized degradation machinery for the disposal of damaged protein aggregates and mitochondria, two common denominators in neurodegenerative diseases. We have discovered that this form of quality control (QC) autophagy is controlled by a ubiquitin-binding deacetylase, HDAC6. Using both mouse and cell models, we are investigating how HDAC6 enforces QC autophagy and its importance in neurodegenerative disease and metabolic disorders. The potential of HDAC6 as a therapeutic target is being actively pursued.
(2) HDAC in mitochondria function and quality control. Acetyl-CoA is the donor of acetyl group for protein acetylation and numerous metabolic reactions. Remarkably, many mitochondrial enzymes and proteins are subject to acetylation. We are interested in characterizing the roles of HDAC in mitochondrial adaptation to changing metabolic demands and elucidating the intimate relationship between metabolism and protein acetylation.
(3) HDAC, skeletal muscle remodeling, regeneration and neuromuscular disease. Skeletal muscle undergoes active remodeling in response to change in neural inputs or damage. Loss in neural input causes dramatic muscle dysfunction and disease, such as ALS. We have discovered that neural activity controls muscle phenotype through HDAC4, whose activity becomes deregulated in ALS patients. We have characterized this novel HDAC4-dependent signaling pathway and are evaluating modulators of this pathway for potential clinical utility in motor neuron disease.
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