bims-mitlys 2021-05-02 papers

bims-mitlys

Biomed News

on Mitochondria and Lysosomes

Issue of 2021‒05‒02
eleven papers selected by
Nicoletta Plotegher
University of Padua

Quantitative imaging of membrane contact sites for sterol transfer between endo-lysosomes and mitochondria in living cells.
PDZD8-mediated lipid transfer at contacts between the ER and late endosomes/lysosomes is required for neurite outgrowth.
Autophagic Organelles in DNA Damage Response.
Mitochondria Turnover and Lysosomal Function in Hematopoietic Stem Cell Metabolism.
Mitochondrial Dynamics: A Key Role in Neurodegeneration and a Potential Target for Neurodegenerative Disease.
Intersection between Redox Homeostasis and Autophagy: Valuable Insights into Neurodegeneration.
The Role of Mitophagy in Pulmonary Sepsis.
PINK1: A Bridge between Mitochondria and Parkinson's Disease.
Quinacrine-Induced Autophagy in Ovarian Cancer Triggers Cathepsin-L Mediated Lysosomal/Mitochondrial Membrane Permeabilization and Cell Death.
Editorial: Organelles Relationships and Interactions: A Cancer Perspective.
The mTOR Deficiency in Monocytic Myeloid-Derived Suppressor Cells Protects Mouse Cardiac Allografts by Inducing Allograft Tolerance.

Sci Rep. 2021 Apr 26. 11(1): 8927

Quantitative imaging of membrane contact sites for sterol transfer between endo-lysosomes and mitochondria in living cells.

Alice Dupont Juhl, Christian W Heegaard, Stephan Werner, Gerd Schneider, Kathiresan Krishnan, Douglas F Covey, Daniel Wüstner.

Mitochondria receive cholesterol from late endosomes and lysosomes (LE/LYSs) or from the plasma membrane for production of oxysterols and steroid hormones. This process depends on the endo-lysosomal sterol transfer protein Niemann Pick C2 (NPC2). Using the intrinsically fluorescent cholesterol analog, cholestatrienol, we directly observe sterol transport to mitochondria in fibroblasts upon treating NPC2 deficient human fibroblasts with NPC2 protein. Soft X-ray tomography reveals the ultrastructure of mitochondria and discloses close contact to endosome-like organelles. Using fluorescence microscopy, we localize endo-lysosomes containing NPC2 relative to mitochondria based on the Euclidian distance transform and use statistical inference to show that about 30% of such LE/LYSs are in contact to mitochondria in human fibroblasts. Using Markov Chain Monte Carlo image simulations, we show that interaction between both organelle types, a defining feature of membrane contact sites (MCSs) can give rise to the observed spatial organelle distribution. We devise a protocol to determine the surface fraction of endo-lysosomes in contact with mitochondria and show that this fraction does not depend on functional NPC1 or NPC2 proteins. Finally, we localize MCSs between LE/LYSs containing NPC2 and mitochondria in time-lapse image sequences and show that they either form transiently or remain stable for tens of seconds. Lasting MCSs between endo-lysosomes containing NPC2 and mitochondria move by slow anomalous sub-diffusion, providing location and time for sterol transport between both organelles. Our quantitative imaging strategy will be of high value for characterizing the dynamics and function of MCSs between various organelles in living cells.

DOI: https://doi.org/10.1038/s41598-021-87876-7
J Cell Sci. 2022 Mar 01. pii: jcs255026. [Epub ahead of print]135(5):

PDZD8-mediated lipid transfer at contacts between the ER and late endosomes/lysosomes is required for neurite outgrowth.

Yuan Gao, Juan Xiong, Qing-Zhu Chu, Wei-Ke Ji.

  Membrane contact sites (MCSs) between the endoplasmic reticulum (ER) and late endosomes/lysosomes (LE/lys) are emerging as critical hubs for diverse cellular events, and changes in their extents are linked to severe neurological diseases. While recent studies show that the synaptotagmin-like mitochondrial-lipid-binding (SMP) domain-containing protein PDZD8 may mediate the formation of ER-LE/lys MCSs, the cellular functions of PDZD8 remain largely elusive. Here, we attempt to investigate the lipid transfer activities of PDZD8 and the extent to which its cellular functions depend on its lipid transfer activities. In accordance with recent studies, we demonstrate that PDZD8 is a protrudin (ZFYVE27)-interacting protein and that PDZD8 acts as a tether at ER-LE/lys MCSs. Furthermore, we discover that the SMP domain of PDZD8 binds glycerophospholipids and ceramides both in vivo and in vitro, and that the SMP domain can transport lipids between membranes in vitro. Functionally, PDZD8 is required for LE/lys positioning and neurite outgrowth, which is dependent on the lipid transfer activity of the SMP domain.

Keywords:  Endoplasmic reticulum; Late endosomes; Lipid transfer; Lysosomes; Membrane contact sites; PDZD8

DOI:  https://doi.org/10.1242/jcs.255026
Front Cell Dev Biol. 2021 ;9 668735

Autophagic Organelles in DNA Damage Response.

Jeongha Kim, Sungmin Lee, Hyunwoo Kim, Haksoo Lee, Ki Moon Seong, HyeSook Youn, BuHyun Youn.

  Autophagy is an important subcellular event engaged in the maintenance of cellular homeostasis via the degradation of cargo proteins and malfunctioning organelles. In response to cellular stresses, like nutrient deprivation, infection, and DNA damaging agents, autophagy is activated to reduce the damage and restore cellular homeostasis. One of the responses to cellular stresses is the DNA damage response (DDR), the intracellular pathway that senses and repairs damaged DNA. Proper regulation of these pathways is crucial for preventing diseases. The involvement of autophagy in the repair and elimination of DNA aberrations is essential for cell survival and recovery to normal conditions, highlighting the importance of autophagy in the resolution of cell fate. In this review, we summarized the latest information about autophagic recycling of mitochondria, endoplasmic reticulum (ER), and ribosomes (called mitophagy, ER-phagy, and ribophagy, respectively) in response to DNA damage. In addition, we have described the key events necessary for a comprehensive understanding of autophagy signaling networks. Finally, we have highlighted the importance of the autophagy activated by DDR and appropriate regulation of autophagic organelles, suggesting insights for future studies. Especially, DDR from DNA damaging agents including ionizing radiation (IR) or anti-cancer drugs, induces damage to subcellular organelles and autophagy is the key mechanism for removing impaired organelles.

Keywords:  DNA damage response; ER-phagy; mitophagy; ribophagy; therapeutic approach

DOI:  https://doi.org/10.3389/fcell.2021.668735
Int J Mol Sci. 2021 Apr 28. pii: 4627. [Epub ahead of print]22(9):

Mitochondria Turnover and Lysosomal Function in Hematopoietic Stem Cell Metabolism.

Makiko Mochizuki-Kashio, Hiroko Shiozaki, Toshio Suda, Ayako Nakamura-Ishizu.

  Hematopoietic stem cells (HSCs) reside in a hypoxic microenvironment that enables glycolysis-fueled metabolism and reduces oxidative stress. Nonetheless, metabolic regulation in organelles such as the mitochondria and lysosomes as well as autophagic processes have been implicated as essential for the determination of HSC cell fate. This review encompasses the current understanding of anaerobic metabolism in HSCs as well as the emerging roles of mitochondrial metabolism and lysosomal regulation for hematopoietic homeostasis.

Keywords:  ROS; autophagy; folliculin; hematopoietic stem cells; lysosome; mitochondria

DOI:  https://doi.org/10.3390/ijms22094627
Front Neurosci. 2021 ;15 654785

Mitochondrial Dynamics: A Key Role in Neurodegeneration and a Potential Target for Neurodegenerative Disease.

Danying Yang, Jun Ying, Xifeng Wang, Tiancheng Zhao, Sungtae Yoon, Yang Fang, Qingcui Zheng, Xing Liu, Wen Yu, Fuzhou Hua.

  In neurodegenerative diseases, neurodegeneration has been related to several mitochondrial dynamics imbalances such as excessive fragmentation of mitochondria, impaired mitophagy, and blocked mitochondria mitochondrial transport in axons. Mitochondria are dynamic organelles, and essential for energy conversion, neuron survival, and cell death. As mitochondrial dynamics have a significant influence on homeostasis, in this review, we mainly discuss the role of mitochondrial dynamics in several neurodegenerative diseases. There is evidence that several mitochondrial dynamics-associated proteins, as well as related pathways, have roles in the pathological process of neurodegenerative diseases with an impact on mitochondrial functions and metabolism. However, specific pathological mechanisms need to be better understood in order to propose new therapeutic strategies targeting mitochondrial dynamics that have shown promise in recent studies.

Keywords:  mitochondrial dynamics; mitochondrial fusion and fission; mitochondrial transport; mitophagy; neurodegeneration

DOI:  https://doi.org/10.3389/fnins.2021.654785
Antioxidants (Basel). 2021 Apr 28. pii: 694. [Epub ahead of print]10(5):

Intersection between Redox Homeostasis and Autophagy: Valuable Insights into Neurodegeneration.

Hyungsun Park, Jongyoon Kim, Chihoon Shin, Seongju Lee.

  Autophagy, a main degradation pathway for maintaining cellular homeostasis, and redox homeostasis have recently been considered to play protective roles in neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. Increased levels of reactive oxygen species (ROS) in neurons can induce mitochondrial damage and protein aggregation, thereby resulting in neurodegeneration. Oxidative stress is one of the major activation signals for the induction of autophagy. Upon activation, autophagy can remove ROS, damaged mitochondria, and aggregated proteins from the cells. Thus, autophagy can be an effective strategy to maintain redox homeostasis in the brain. However, the interaction between redox homeostasis and autophagy is not clearly elucidated. In this review, we discuss recent studies on the relationship between redox homeostasis and autophagy associated with neurodegenerative diseases and propose that autophagy induction through pharmacological intervention or genetic activation might be a promising strategy to treat these disorders.

Keywords:  ROS; autophagy; neurodegenerative diseases; redox homeostasis

DOI:  https://doi.org/10.3390/antiox10050694
Mitochondrion. 2021 Apr 21. pii: S1567-7249(21)00055-6. [Epub ahead of print]

The Role of Mitophagy in Pulmonary Sepsis.

Mohd Mohsin, Gulnaz Tabassum, Shaniya Ahmad, Shakir Ali, Mansoor Ali Syed.

  Sepsis is a systemic inflammatory disease with an unacceptably high mortality rate caused by an infection or trauma that involves both innate and adaptive immune systems. Inflammatory events activate different downstream pathways leading to tissue damage and ultimately multi-organ failure. Mitochondria are responsible for cellular energy, thermoregulation, metabolite biosynthesis, intracellular calcium regulation, and cell death. Damaged mitochondria induce the high Ca2+ influx through mitochondrial calcium uniporter (MCU). It also generates excessive Reactive oxygen species (ROS) and releases mtDNA into the cytoplasm, which causes induction of NLRP3 inflammasome and apoptosis. Mitophagy (Autophagy of damaged mitochondria) controls mitochondrial dynamics and function. It also maintains cellular homeostasis. This review is about how pulmonary sepsis affects the body. What is the aftermath of sepsis, and how mitophagy affects Acute Lung Injury and macrophage polarisation to overcome the damages.

Keywords:  ALI; Intracellular calcium; Macrophage polarisation; Mitophagy; Oxidative stress; Pulmonary sepsis; Sepsis

DOI:  https://doi.org/10.1016/j.mito.2021.04.009
Life (Basel). 2021 Apr 21. pii: 371. [Epub ahead of print]11(5):

PINK1: A Bridge between Mitochondria and Parkinson's Disease.

Filipa Barroso Gonçalves, Vanessa Alexandra Morais.

  Mitochondria are known as highly dynamic organelles essential for energy production. Intriguingly, in the recent years, mitochondria have revealed the ability to maintain cell homeostasis and ultimately regulate cell fate. This regulation is achieved by evoking mitochondrial quality control pathways that are capable of sensing the overall status of the cellular environment. In a first instance, actions to maintain a robust pool of mitochondria take place; however, if unsuccessful, measures that lead to overall cell death occur. One of the central key players of these mitochondrial quality control pathways is PINK1 (PTEN-induce putative kinase), a mitochondrial targeted kinase. PINK1 is known to interact with several substrates to regulate mitochondrial functions, and not only is responsible for triggering mitochondrial clearance via mitophagy, but also participates in maintenance of mitochondrial functions and homeostasis, under healthy conditions. Moreover, PINK1 has been associated with the familial form of Parkinson's disease (PD). Growing evidence has strongly linked mitochondrial homeostasis to the central nervous system (CNS), a system that is replenished with high energy demanding long-lasting neuronal cells. Moreover, sporadic cases of PD have also revealed mitochondrial impairments. Thus, one could speculate that mitochondrial homeostasis is the common denominator in these two forms of the disease, and PINK1 may play a central role in maintaining mitochondrial homeostasis. In this review, we will discuss the role of PINK1 in the mitochondrial physiology and scrutinize its role in the cascade of PD pathology.

Keywords:  PINK1; Parkinson’s disease; mitochondria homeostasis

DOI:  https://doi.org/10.3390/life11050371
Cancers (Basel). 2021 Apr 21. pii: 2004. [Epub ahead of print]13(9):

Quinacrine-Induced Autophagy in Ovarian Cancer Triggers Cathepsin-L Mediated Lysosomal/Mitochondrial Membrane Permeabilization and Cell Death.

Prabhu Thirusangu, Christopher L Pathoulas, Upasana Ray, Yinan Xiao, Julie Staub, Ling Jin, Ashwani Khurana, Viji Shridhar.

  We previously reported that the antimalarial compound quinacrine (QC) induces autophagy in ovarian cancer cells. In the current study, we uncovered that QC significantly upregulates cathepsin L (CTSL) but not cathepsin B and D levels, implicating the specific role of CTSL in promoting QC-induced autophagic flux and apoptotic cell death in OC cells. Using a Magic Red® cathepsin L activity assay and LysoTracker red, we discerned that QC-induced CTSL activation promotes lysosomal membrane permeability (LMP) resulting in the release of active CTSL into the cytosol to promote apoptotic cell death. We found that QC-induced LMP and CTSL activation promotes Bid cleavage, mitochondrial outer membrane permeabilization (MOMP), and mitochondrial cytochrome-c release. Genetic (shRNA) and pharmacological (Z-FY(tBU)-DMK) inhibition of CTSL markedly reduces QC-induced autophagy, LMP, MOMP, apoptosis, and cell death; whereas induced overexpression of CTSL in ovarian cancer cell lines has an opposite effect. Using recombinant CTSL, we identified p62/SQSTM1 as a novel substrate of CTSL, suggesting that CTSL promotes QC-induced autophagic flux. CTSL activation is specific to QC-induced autophagy since no CTSL activation is seen in ATG5 knockout cells or with the anti-malarial autophagy-inhibiting drug chloroquine. Importantly, we showed that upregulation of CTSL in QC-treated HeyA8MDR xenografts corresponds with attenuation of p62, upregulation of LC3BII, cytochrome-c, tBid, cleaved PARP, and caspase3. Taken together, the data suggest that QC-induced autophagy and CTSL upregulation promote a positive feedback loop leading to excessive autophagic flux, LMP, and MOMP to promote QC-induced cell death in ovarian cancer cells.

Keywords:  CTSL; LMP; MOMP; autophagy; ovarian cancer; quinacrine

DOI:  https://doi.org/10.3390/cancers13092004
Front Cell Dev Biol. 2021 ;9 678307

Editorial: Organelles Relationships and Interactions: A Cancer Perspective.

Simone Patergnani, Saverio Marchi, Benjamin Delprat, Mariusz R Wieckowski.



Keywords:  cancer; endoplasmic reticulum; lysosomes; mitochondria; organelles; therapy

DOI:  https://doi.org/10.3389/fcell.2021.678307
Front Immunol. 2021 ;12 661338

The mTOR Deficiency in Monocytic Myeloid-Derived Suppressor Cells Protects Mouse Cardiac Allografts by Inducing Allograft Tolerance.

Jiawei Li, Juntao Chen, Mingnan Zhang, Chao Zhang, Renyan Wu, Tianying Yang, Yue Qiu, Jingjing Liu, Tongyu Zhu, Yi Zhang, Ruiming Rong.

  Background: Myeloid-derived suppressor cells (MDSCs) can prevent allograft rejection and induce immune tolerance in transplantation models. Previous studies have demonstrated that inhibition of mTOR signaling can enhance the MDSC protective effect in heart transplantation (HTx) by promoting MDSC expansion. In addition, mTOR inhibition is related to autophagy. The present study investigated the protective mechanism of mTOR-deficient monocytic MDSCs (M-MDSCs) in mouse HTx.Methods: Myeloid-specific mTOR conditional knockout mice were generated to obtain mTOR-/- M-MDSCs. The proliferation and immunosuppressive function of mTOR-/- M-MDSCs were determined by flow cytometry and T cell proliferation assays. The mTOR-/- M-MDSC intracellular autophagy levels were determined using western blotting and electron microscopy. RNAseq analysis was performed for wild-type (WT) and mTOR-/- M-MDSCs. Allogeneic HTx mouse model was established and treated with WT or mTOR-/- M-MDSCs. Enzyme-linked immunosorbent assay, flow cytometry, and immunohistochemistry assays were performed to determine WT and mTOR-/- M-MDSC-induced immune tolerance.
Results: The mTOR deficiency promoted M-MDSC differentiation and enhanced intracellular autophagy levels in vivo and in vitro. mTOR deficiency also enhanced the immunosuppressive function of M-MDSCs. In addition, infusing with WT and mTOR-/- M-MDSCs prolonged cardiac allograft survival and established immune tolerance in recipient mice by inhibiting T cell activation and inducing regulatory T cells.
Conclusion: mTOR deficiency enhances the immunosuppressive function of M-MDSCs and prolongs mouse cardiac allograft survival.

Keywords:  MDSC (myeloid-derived suppressor cell); autophagy; cardiac transplantation; immune tolerance; mTOR

DOI:  https://doi.org/10.3389/fimmu.2021.661338