bims-minimp 2022-01-09 papers

on Mitochondria, innate immunity, proteostasis

Issue of 2022–01–09
ten papers selected by
Hanna Salmonowicz, International Institute of Molecular Mechanisms and Machines of the Polish Academy of Sciences

The SUMO protease SENP3 regulates mitochondrial autophagy mediated by Fis1.
Hierarchical integration of mitochondrial and nuclear positioning pathways by the Num1 EF hand.
Nek4 regulates mitochondrial respiration and morphology.
STING orchestrates the crosstalk between polyunsaturated fatty acid metabolism and inflammatory responses.
Regulation of Mitochondrial Function by the Actin Cytoskeleton.
C10orf10/DEPP activates mitochondrial autophagy and maintains chondrocyte viability in the pathogenesis of osteoarthritis.
Proteomic Identification of the SLC25A46 Interactome in Transgenic Mice Expressing SLC25A46-FLAG.
Mitochondrial STAT3 exacerbates LPS-induced sepsis by driving CPT1a-mediated fatty acid oxidation.
Multidimensional dynamics of the proteome in the neurodegenerative and aging mammalian brain.
Restoration of mitophagy ameliorates cardiomyopathy in Barth syndrome.

EMBO Rep. 2022 Jan 07. e48754

The SUMO protease SENP3 regulates mitochondrial autophagy mediated by Fis1.

Emily Waters, Kevin A Wilkinson, Amy L Harding, Ruth E Carmichael, Darren Robinson, Helen E Colley, Chun Guo.

  Mitochondria are unavoidably subject to organellar stress resulting from exposure to a range of reactive molecular species. Consequently, cells operate a poorly understood quality control programme of mitophagy to facilitate elimination of dysfunctional mitochondria. Here, we used a model stressor, deferiprone (DFP), to investigate the molecular basis for stress-induced mitophagy. We show that mitochondrial fission 1 protein (Fis1) is required for DFP-induced mitophagy and that Fis1 is SUMOylated at K149, an amino acid residue critical for Fis1 mitochondrial localization. We find that DFP treatment leads to the stabilization of the SUMO protease SENP3, which is mediated by downregulation of the E3 ubiquitin (Ub) ligase CHIP. SENP3 is responsible for Fis1 deSUMOylation and depletion of SENP3 abolishes DFP-induced mitophagy. Furthermore, preventing Fis1 SUMOylation by conservative K149R mutation enhances Fis1 mitochondrial localization. Critically, expressing a Fis1 K149R mutant restores DFP-induced mitophagy in SENP3-depleted cells. Thus, we propose a model in which SENP3-mediated deSUMOylation facilitates Fis1 mitochondrial localization to underpin stress-induced mitophagy.

Keywords:  Fis1; SENP3; SUMO; mitophagy; organellar stress

DOI:  https://doi.org/10.15252/embr.201948754
Mol Biol Cell. 2022 Jan 05. mbcE21120610T

Hierarchical integration of mitochondrial and nuclear positioning pathways by the Num1 EF hand.

Heidi L Anderson, Jason C Casler, Laura L Lackner.

Positioning organelles at the right place and time is critical for their function and inheritance. In budding yeast, mitochondrial and nuclear positioning require the anchoring of mitochondria and dynein to the cell cortex by clusters of Num1. We have previously shown that mitochondria drive the assembly of cortical Num1 clusters, which then serve as anchoring sites for mitochondria and dynein. When mitochondrial inheritance is inhibited, mitochondrial-driven assembly of Num1 in buds is disrupted and defects in dynein-mediated spindle positioning are observed. Using a structure-function approach to dissect the mechanism of mitochondria-dependent dynein anchoring, we found the EF hand-like motif (EFLM) of Num1 and its ability to bind calcium are required to bias dynein anchoring on mitochondria-associated Num1 clusters. Consistently, when the EFLM is disrupted, we no longer observe defects in dynein activity following inhibition of mitochondrial inheritance. Thus, the Num1 EFLM functions to bias dynein anchoring and activity in nuclear inheritance subsequent to mitochondrial inheritance. We hypothesize that this hierarchical integration of organelle positioning pathways by the Num1 EFLM contributes to the regulated order of organelle inheritance during the cell cycle.

DOI: https://doi.org/10.1091/mbc.E21-12-0610-T
FEBS J. 2022 Jan 05.

Nek4 regulates mitochondrial respiration and morphology.

Fernanda Luisa Basei, Camila de Castro Ferezin, Ana Luisa Rodrigues de Oliveira, Juan Pablo Muñoz, Antonio Zorzano, Jörg Kobarg.

  Nek4 is a serine/threonine kinase which has been implicated in primary cilia stabilization, DNA damage response, autophagy and epithelial-to-mesenchymal transition. The role of Nek4 in cancer cell survival and chemotherapy resistance has also been shown. However, the precise mechanisms by which Nek4 operates remain to be elucidated. Here, we show that Nek4 overexpression activates mitochondrial respiration coupled to ATP production, which is paralleled by increased mitochondrial membrane potential, and resistance to mitochondrial DNA damage. Congruently, Nek4 depletion reduced mitochondrial respiration and mtDNA integrity. Nek4 deficiency caused mitochondrial elongation, probably via reduced activity of the fission protein DRP1. In Nek4 overexpressing cells the increase in mitochondrial fission was concomitant to enhanced phosphorylation of DRP1 and Erk1/2 proteins, and the effects on mitochondrial respiration were abolished in the presence of a DRP1 inhibitor. This study shows Nek4 as a novel regulator of mitochondrial function that may explain the joint appearance of high mitochondrial respiration and mitochondrial fragmentation.

Keywords:  DRP1; Nek4; fission; mitochondrial function

DOI:  https://doi.org/10.1111/febs.16343
Cell Metab. 2022 Jan 04. pii: S1550-4131(21)00626-4. [Epub ahead of print]34(1): 125-139.e8

STING orchestrates the crosstalk between polyunsaturated fatty acid metabolism and inflammatory responses.

Isabelle K Vila, Hanane Chamma, Alizée Steer, Mathilde Saccas, Clara Taffoni, Evgenia Turtoi, Line S Reinert, Saqib Hussain, Johanna Marines, Lei Jin, Xavier Bonnefont, Mathieu Hubert, Olivier Schwartz, Soren R Paludan, Gaetan Van Simaeys, Gilles Doumont, Bijan Sobhian, Dimitrios Vlachakis, Andrei Turtoi, Nadine Laguette.

  Concerted alteration of immune and metabolic homeostasis underlies several inflammation-related pathologies, ranging from metabolic syndrome to infectious diseases. Here, we explored the coordination of nucleic acid-dependent inflammatory responses and metabolic homeostasis. We reveal that the STING (stimulator of interferon genes) protein regulates metabolic homeostasis through inhibition of the fatty acid desaturase 2 (FADS2) rate-limiting enzyme in polyunsaturated fatty acid (PUFA) desaturation. STING ablation and agonist-mediated degradation increased FADS2-associated desaturase activity and led to accumulation of PUFA derivatives that drive thermogenesis. STING agonists directly activated FADS2-dependent desaturation, promoting metabolic alterations. PUFAs in turn inhibited STING, thereby regulating antiviral responses and contributing to resolving STING-associated inflammation. Thus, we have unveiled a negative regulatory feedback loop between STING and FADS2 that fine-tunes inflammatory responses. Our results highlight the role of metabolic alterations in human pathologies associated with aberrant STING activation and STING-targeting therapies.

Keywords:  FADS2; STING; cGAS; cytosolic DNA; delta-6 Desaturase; inflammation; interferon responses; metabolism; nucleic acid immunity; polyunsaturated fatty acids

DOI:  https://doi.org/10.1016/j.cmet.2021.12.007
Front Cell Dev Biol. 2021 ;9 795838

Regulation of Mitochondrial Function by the Actin Cytoskeleton.

María Illescas, Ana Peñas, Joaquín Arenas, Miguel A Martín, Cristina Ugalde.

  The regulatory role of actin cytoskeleton on mitochondrial function is a growing research field, but the underlying molecular mechanisms remain poorly understood. Specific actin-binding proteins (ABPs), such as Gelsolin, have also been shown to participate in the pathophysiology of mitochondrial OXPHOS disorders through yet to be defined mechanisms. In this mini-review, we will summarize the experimental evidence supporting the fundamental roles of actin cytoskeleton and ABPs on mitochondrial trafficking, dynamics, biogenesis, metabolism and apoptosis, with a particular focus on Gelsolin involvement in mitochondrial disorders. The functional interplay between the actin cytoskeleton, ABPs and mitochondrial membranes for the regulation of cellular homeostasis thus emerges as a new exciting field for future research and therapeutic approaches.

Keywords:  OXPHOS system; actin cytoskeleton; gelsolin; mitochondria; mitochondrial disease

DOI:  https://doi.org/10.3389/fcell.2021.795838
FASEB J. 2022 Feb;36(2): e22145

C10orf10/DEPP activates mitochondrial autophagy and maintains chondrocyte viability in the pathogenesis of osteoarthritis.

Masanari Kuwahara, Yukio Akasaki, Ichiro Kurakazu, Takuya Sueishi, Masakazu Toya, Taisuke Uchida, Tomoaki Tsutsui, Ryota Hirose, Hidetoshi Tsushima, Takeshi Teramura, Yasuharu Nakashima.

  Osteoarthritis (OA), the most prevalent joint disease, is characterized by the progressive loss of articular cartilage. Autophagy, a lysosomal degradation pathway, maintains cellular homeostasis, and autophagic dysfunction in chondrocytes is a hallmark of OA pathogenesis. However, the cause of autophagic dysfunction in OA chondrocytes remains incompletely understood. Recent studies have reported that decidual protein induced by progesterone (C10orf10/DEPP) positively regulates autophagic functions. In this study, we found that DEPP was involved in mitochondrial autophagic functions of chondrocytes, as well as in OA pathogenesis. DEPP expression decreased in human OA chondrocytes in the absence or presence of pro-inflammatory cytokines, and was induced by starvation, hydrogen peroxide (H2 O2 ), and hypoxia (cobalt chloride). For functional studies, DEPP knockdown decreased autophagic flux induced by H2 O2 , whereas DEPP overexpression increased autophagic flux and maintained cell viability following H2 O2 treatment. DEPP was downregulated by knockdown of forkhead box class O (FOXO) transcription factors and modulated the autophagic function regulated by FOXO3. In an OA mouse model by destabilization of the medial meniscus, DEPP-knockout mice exacerbated the progression of cartilage degradation with TUNEL-positive cells, and chondrocytes isolated from knockout mice were decreased autophagic flux and increased cell death following H2 O2 treatment. Subcellular fractionation analysis revealed that mitochondria-located DEPP activated mitochondrial autophagy via BCL2 interacting protein 3. Taken together, our data demonstrate that DEPP is a major stress-inducible gene involved in the activation of mitochondrial autophagy in chondrocytes, and maintains chondrocyte viability during OA pathogenesis. DEPP represents a potential therapeutic target for enhancing autophagy in patients with OA.

Keywords:  C10orf10/DEPP; autophagy; chondrocyte; mitochondria; osteoarthritis

DOI:  https://doi.org/10.1096/fj.202100896R
J Proteome Res. 2022 Jan 05.

Proteomic Identification of the SLC25A46 Interactome in Transgenic Mice Expressing SLC25A46-FLAG.

Vasiliki-Iris Perivolidi, Foteini Violitzi, Elisavet Ioannidou, Vagelis Rinotas, George Stamatakis, Martina Samiotaki, George Panayotou, Eleni Douni.

  The outer mitochondrial membrane protein SLC25A46 has been recently identified as a novel genetic cause of a wide spectrum of neurological diseases. The aim of the present work was to elucidate the physiological role of SLC25A46 through the identification of its interactome with immunoprecipitation and proteomic analysis in whole cell extracts from the cerebellum, cerebrum, heart, and thymus of transgenic mice expressing ubiquitously SLC25A46-FLAG. Our analysis identified 371 novel putative interactors of SLC25A46 and confirmed 17 known ones. A total of 79 co-immunoprecipitated proteins were common in two or more tissues, mainly participating in mitochondrial activities such as oxidative phosphorylation (OXPHOS) and ATP production, active transport of ions or molecules, and the metabolism. Tissue-specific co-immunoprecipitated proteins were enriched for synapse annotated proteins in the cerebellum and cerebrum for metabolic processes in the heart and for nuclear processes and proteasome in the thymus. Our proteomic approach confirmed known mitochondrial interactors of SLC25A46 including MICOS complex subunits and also OPA1 and VDACs, while we identified novel interactors including the ADP/ATP translocases SLC25A4 and SLC25A5, subunits of the OXPHOS complexes and F1Fo-ATP synthase, and components of the mitochondria-ER contact sites. Our results show that SLC25A46 interacts with a large number of proteins and protein complexes involved in the mitochondria architecture, energy production, and flux and also in inter-organellar contacts.

Keywords:  LC−MS/MS; SLC25A46; interactome; mitochondria; neurological diseases; quantitative proteomics; transgenic mice

DOI:  https://doi.org/10.1021/acs.jproteome.1c00728
Theranostics. 2022 ;12(2): 976-998

Mitochondrial STAT3 exacerbates LPS-induced sepsis by driving CPT1a-mediated fatty acid oxidation.

Rongqing Li, Xueqin Li, Jie Zhao, Fandong Meng, Chen Yao, Ensi Bao, Na Sun, Xin Chen, Wanpeng Cheng, Hui Hua, Xiangyang Li, Bo Wang, Hui Wang, Xiucheng Pan, Hongjuan You, Jing Yang, Takayuki Ikezoe.

  Rationale: We found that a subset of signal transducer and activator of transcription 3 (STAT3) translocated into mitochondria in phagocytes, including macrophages isolated from individuals with sepsis. However, the role of mitochondrial STAT3 in macrophages remains unclear. Method: To investigate the function of mitochondrial STAT3 in vivo, we generated inducible mitochondrial STAT3 knock-in mice. A cytokine array analysis, a CBA analysis, flow cytometry, immunofluorescence staining and quantification and metabolic analyses in vivo were subsequently performed in an LPS-induced sepsis model. Single-cell RNA sequencing, a microarray analysis, metabolic assays, mass spectrometry and ChIP assays were utilized to gain insight into the mechanisms of mitochondrial STAT3 in metabolic reprogramming in LPS-induced sepsis. Results: We found that mitochondrial STAT3 induced NF-κB nuclear localization and exacerbated LPS-induced sepsis in parallel with a metabolic switch from mainly using glucose to an increased reliance on fatty acid oxidation (FAO). Moreover, mitochondrial STAT3 abrogated carnitine palmitoyl transferase 1a (CPT1a) ubiquitination and degradation in LPS-treated macrophages. Meanwhile, an interaction between CPT1a and ubiquitin-specific peptidase 50 (USP50) was observed. In contrast, knocking down USP50 decreased CPT1a expression and FAO mediated by mitochondrial STAT3. The ChIP assays revealed that NF-κB bound the USP50 promoter. Curcumin alleviated LPS-mediated sepsis by suppressing the activities of mitochondrial STAT3 and NF-κB. Conclusion: Our findings reveal that mitochondrial STAT3 could trigger FAO by inducing CPT1a stabilization mediated by USP50 in macrophages, at least partially.

Keywords:  CPT1a stabilization; FAO; USP50; mitochondrial STAT3

DOI:  https://doi.org/10.7150/thno.63751
Mol Cell Proteomics. 2021 Dec 31. pii: S1535-9476(21)00164-X. [Epub ahead of print] 100192

Multidimensional dynamics of the proteome in the neurodegenerative and aging mammalian brain.

Byron Andrews, Alan E Murphy, Michele Stofella, Sarah Maslen, Leonardo Almeida-Souza, J Mark Skehel, Nathan G Skene, Frank Sobott, René A W Frank.

  The amount of any given protein in the brain is determined by the rates of its synthesis and destruction, which are regulated by different cellular mechanisms. Here, we combine metabolic labelling in live mice with global proteomic profiling to simultaneously quantify both the flux and amount of proteins in mouse models of neurodegeneration. In multiple models, protein turnover increases were associated with increasing pathology. This method distinguishes changes in protein expression mediated by synthesis from those mediated by degradation. In the AppNL-F knockin mouse model of Alzheimer's disease increased turnover resulted from imbalances in both synthesis and degradation, converging on proteins associated with synaptic vesicle recycling (Dnm1, Cltc, Rims1) and mitochondria (Fis1, Ndufv1). In contrast to disease models, aging in wildtype mice caused a widespread decrease in protein recycling associated with a decrease in autophagic flux. Overall, this simple multidimensional approach enables the comprehensive mapping of proteome dynamics and identifies affected proteins in mouse models of disease and other live animal test settings.

Keywords:  Alzheimer's disease; Protein turnover; Proteomics; SILAM; neurodegeneration

DOI:  https://doi.org/10.1016/j.mcpro.2021.100192
Autophagy. 2022 Jan 05. 1-16

Restoration of mitophagy ameliorates cardiomyopathy in Barth syndrome.

Jun Zhang, Xueling Liu, Jia Nie, Yuguang Shi.

  Barth syndrome (BTHS) is an X-linked genetic disorder caused by mutations in the TAFAZZIN/Taz gene which encodes a transacylase required for cardiolipin remodeling. Cardiolipin is a mitochondrial signature phospholipid that plays a pivotal role in maintaining mitochondrial membrane structure, respiration, mtDNA biogenesis, and mitophagy. Mutations in the TAFAZZIN gene deplete mature cardiolipin, leading to mitochondrial dysfunction, dilated cardiomyopathy, and premature death in BTHS patients. Currently, there is no effective treatment for this debilitating condition. In this study, we showed that TAFAZZIN deficiency caused hyperactivation of MTORC1 signaling and defective mitophagy, leading to accumulation of autophagic vacuoles and dysfunctional mitochondria in the heart of Tafazzin knockdown mice, a rodent model of BTHS. Consequently, treatment of TAFAZZIN knockdown mice with rapamycin, a potent inhibitor of MTORC1, not only restored mitophagy, but also mitigated mitochondrial dysfunction and dilated cardiomyopathy. Taken together, these findings identify MTORC1 as a novel therapeutic target for BTHS, suggesting that pharmacological restoration of mitophagy may provide a novel treatment for BTHS.Abbreviations: BTHS: Barth syndrome; CCCP: carbonyl cyanide 3-chlorophenylhydrazone; CL: cardiolipin; EIF4EBP1/4E-BP1: eukaryotic translation initiation factor 4E binding protein 1; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; KD: knockdown; KO: knockout; LAMP1: lysosomal-associated membrane protein 1; LV: left ventricle; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MEFs: mouse embryonic fibroblasts; MTORC1: mechanistic target of rapamycin kinase complex 1; OCR: oxygen consumption rate; PE: phosphatidylethanolamine; PIK3C3/VPS34: phosphatidylinositol 3-kinase catalytic subunit type 3; PINK1: PTEN induced putative kinase 1; PRKN/Parkin: parkin RBR E3 ubiquitin protein ligase; qRT-PCR: quantitative real-time polymerase chain reaction; RPS6KB/S6K: ribosomal protein S6 kinase beta; SQSTM1/p62: sequestosome 1; TLCL: tetralinoleoyl cardiolipin; WT: wild-type.

Keywords:  BTHS; MTORC1; TAFAZZIN; cardiolipin; mitophagy; rapamycin

DOI:  https://doi.org/10.1080/15548627.2021.2020979