FTLD Patient–Derived Fibroblasts Show Defective Mitochondrial Function and Accumulation of p62

AbstractFrontotemporal lobar degeneration (FTLD) is a clinically, genetically, and neuropathologically heterogeneous group of neurodegenerative syndromes, leading to progressive cognitive dysfunction and frontal and temporal atrophy. C9orf72 hexanucleotide repeat expansion (C9-HRE) is the most common genetic cause of FTLD, but pathogenic mechanisms underlying FTLD are not fully understood. Here, we compared cellular features and functional properties, especially related to protein degradation pathways and mitochondrial function, of FTLD patient–derived skin fibroblasts from C9-HRE carriers and non-carriers and healthy donors. Fibroblasts from C9-HRE carriers were found to produce RNA foci, but no dipeptide repeat proteins, and they showed unchanged levels of C9orf72 mRNA transcripts. The main protein degradation pathways, the ubiquitin–proteasome system and autophagy, did not show alterations between the fibroblasts from C9-HRE-carrying and non-carrying FTLD patients and compared to healthy controls. An increase in the number and size of p62-positive puncta was evident in fibroblasts from both C9-HRE carriers and non-carriers. In addition, several parameters of mitochondrial function, namely, basal and maximal respiration and respiration linked to ATP production, were significantly reduced in the FTLD patient–derived fibroblasts from both C9-HRE carriers and non-carriers. Our findings suggest that FTLD patient–derived fibroblasts, regardless of whether they carry the C9-HRE expansion, show unchanged proteasomal and autophagic function, but significantly impaired mitochondrial function and increased accumulation of p62 when compared to control fibroblasts. These findings suggest the possibility of utilizing FTLD patient–derived fibroblasts as a platform for biomarker discovery and testing of drugs targeted to specific cellular functions, such as mitochondrial respiration.

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The Interplay between Dysregulated Ion Transport and Mitochondrial Architecture as a Dangerous Liaison in Cancer

International Journal of Molecular Sciences ◽

10.3390/ijms22105209 ◽

2021 ◽

Vol 22 (10) ◽

pp. 5209

Author(s):

Stine F. Pedersen ◽

Mette Flinck ◽

Luis A. Pardo

Keyword(s):

Ion Transport ◽

Cell Fate ◽

Mitochondrial Function ◽

Ion Homeostasis ◽

Reciprocal Relationship ◽

Cancer Development ◽

Cellular Functions ◽

Atp Production ◽

Cell Fate Decisions

Transport of ions and nutrients is a core mitochondrial function, without which there would be no mitochondrial metabolism and ATP production. Both ion homeostasis and mitochondrial phenotype undergo pervasive changes during cancer development, and both play key roles in driving the malignancy. However, the link between these events has been largely ignored. This review comprehensively summarizes and critically discusses the role of the reciprocal relationship between ion transport and mitochondria in crucial cellular functions, including metabolism, signaling, and cell fate decisions. We focus on Ca2+, H+, and K+, which play essential and highly interconnected roles in mitochondrial function and are profoundly dysregulated in cancer. We describe the transport and roles of these ions in normal mitochondria, summarize the changes occurring during cancer development, and discuss how they might impact tumorigenesis.

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Regulation of Mitochondrial Genome Inheritance by Autophagy and Ubiquitin-Proteasome System: Implications for Health, Fitness, and Fertility

BioMed Research International ◽

10.1155/2014/981867 ◽

2014 ◽

Vol 2014 ◽

pp. 1-16 ◽

Cited By ~ 11

Author(s):

Won-Hee Song ◽

John William Oman Ballard ◽

Young-Joo Yi ◽

Peter Sutovsky

Keyword(s):

Detrimental Effect ◽

Ubiquitin Proteasome System ◽

Current Data ◽

Reproductive Age ◽

Cellular Functions ◽

Preimplantation Embryo Development ◽

Atp Production ◽

Ubiquitin Proteasome ◽

Mitochondrial Heteroplasmy

Mitochondria, the energy-generating organelles, play a role in numerous cellular functions including adenosine triphosphate (ATP) production, cellular homeostasis, and apoptosis. Maternal inheritance of mitochondria and mitochondrial DNA (mtDNA) is universally observed in humans and most animals. In general, high levels of mitochondrial heteroplasmy might contribute to a detrimental effect on fitness and disease resistance. Therefore, a disposal of the sperm-derived mitochondria inside fertilized oocytes assures normal preimplantation embryo development. Here we summarize the current research and knowledge concerning the role of autophagic pathway and ubiquitin-proteasome-dependent proteolysis in sperm mitophagy in mammals, including humans. Current data indicate that sperm mitophagy inside the fertilized oocyte could occur along multiple degradation routes converging on autophagic clearance of paternal mitochondria. The influence of assisted reproductive therapies (ART) such as intracytoplasmic sperm injection (ICSI), mitochondrial replacement (MR), and assisted fertilization of oocytes from patients of advanced reproductive age on mitochondrial function, inheritance, and fitness and for the development and health of ART babies will be of particular interest to clinical audiences. Altogether, the study of sperm mitophagy after fertilization has implications in the timing of evolution and developmental and reproductive biology and in human health, fitness, and management of mitochondrial disease.

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Tying up loose ends: the N-degron and C-degron pathways of protein degradation

Biochemical Society Transactions ◽

10.1042/bst20191094 ◽

2020 ◽

Vol 48 (4) ◽

pp. 1557-1567 ◽

Cited By ~ 1

Author(s):

Richard T. Timms ◽

Itay Koren

Keyword(s):

Protein Degradation ◽

Protein Interactions ◽

Ubiquitin Proteasome System ◽

Protein Protein Interactions ◽

Cellular Functions ◽

Functional Roles ◽

C Terminus ◽

Ubiquitin Proteasome ◽

Cellular Machinery ◽

Substrate Proteins

Selective protein degradation by the ubiquitin-proteasome system (UPS) is thought to be governed primarily by the recognition of specific motifs — degrons — present in substrate proteins. The ends of proteins — the N- and C-termini – have unique properties, and an important subset of protein–protein interactions involve the recognition of free termini. The first degrons to be discovered were located at the extreme N-terminus of proteins, a finding which initiated the study of the N-degron (formerly N-end rule) pathways, but only in the last few years has it emerged that a diverse set of C-degron pathways target analogous degron motifs located at the extreme C-terminus of proteins. In this minireview we summarise the N-degron and C-degron pathways currently known to operate in human cells, focussing primarily on those that have been discovered in recent years. In each case we describe the cellular machinery responsible for terminal degron recognition, and then consider some of the functional roles of terminal degron pathways. Altogether, a broad spectrum of E3 ubiquitin ligases mediate the recognition of a diverse array of terminal degron motifs; these degradative pathways have the potential to influence a wide variety of cellular functions.

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DDRE-09. DEVELOPING IDO-PROTACS TO IMPROVE IMMUNOTHERAPEUTIC EFFICACY IN PATIENTS WITH GLIOBLASTOMA

Neuro-Oncology ◽

10.1093/neuonc/noaa215.254 ◽

2020 ◽

Vol 22 (Supplement_2) ◽

pp. ii63-ii63

Author(s):

Lakshmi Bollu ◽

Derek Wainwright ◽

Lijie Zhai ◽

Erik Ladomersky ◽

Kristen Lauing ◽

...

Keyword(s):

Protein Degradation ◽

Time Course ◽

Immune Cell ◽

Enzyme Inhibitors ◽

Tumor Development ◽

Ubiquitin Proteasome System ◽

Degradation Pathway ◽

Specific Protein ◽

Cell Functions

Abstract INTRODUCTION Indoleamine 2,3-dioxygenase 1 (IDO; IDO1) is a rate-limiting enzyme that metabolizes the essential amino acid tryptophan into kynurenine. Recent work by our group has revealed that IDO promotes tumor development and suppresses immune cell functions independent of its enzyme activity. Moreover, pharmacologic IDO enzyme inhibitors that currently serve as the only class of drugs available for targeting immunosuppressive IDO activity, fail to improve the survival of patients with GBM. Here, we developed IDO-Proteolysis Targeting Chimeras (IDO-PROTACs). PROTACs bind to a specific protein and recruit an E3 ubiquitin ligase that enhance proteasome-mediated degradation of the target protein. METHODS A library of ≥100 IDO-PROTACs were developed by joining BMS986205 (IDO binder) with a linker group to various E3-ligase ligands. Western blot analysis of PROTAC-induced IDO degradation was tested in vitro among multiple human and mouse GBM cell lines including U87, GBM6, GBM43 and GL261 along a time course ranging between 1–96 hours of treatment and at varying concentrations. The mechanism of IDO protein degradation was investigated using pharmacologic ligands that inhibit or compete with the proteasome-mediated protein degradation pathway. RESULTS Primary screening identified several IDO-PROTACs with IDO protein degradation potential. Secondary screening showed that our lead compound has a DC50 value of ~0.5µM with an ability to degrade IDO in all GBM cells analyzed, and an initial activity within 12 hours of treatment that extended for up to 96 hours. Mutating the CRBN-binding ligand, pretreatment with the ubiquitin proteasome system inhibitors MG132 or MLN4924 or using unmodified parental compound all inhibited IDO protein degradation. CONCLUSIONS This study developed an initial IDO-PROTAC technology that upon further optimization, can neutralize both IDO enzyme and non-enzyme immunosuppressive effects. When combined with other forms of immunotherapy, IDO-PROTACs have the potential to substantially enhance immunotherapeutic efficacy in patients with GBM.

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The Autophagy Pathway: A Critical Route in the Disposal of Alpha 1-Antitrypsin Aggregates That Holds Many Mysteries

International Journal of Molecular Sciences ◽

10.3390/ijms22041875 ◽

2021 ◽

Vol 22 (4) ◽

pp. 1875

Author(s):

Celine Leon ◽

Marion Bouchecareilh

Keyword(s):

Liver Transplantation ◽

Liver Disease ◽

Therapeutic Option ◽

Ubiquitin Proteasome System ◽

Therapeutic Benefit ◽

Cellular Functions ◽

Precise Control ◽

New Therapeutic Approaches ◽

Alpha 1 Antitrypsin Deficiency ◽

Alpha 1 Antitrypsin

The maintenance of proteome homeostasis, or proteostasis, is crucial for preserving cellular functions and for cellular adaptation to environmental challenges and changes in physiological conditions. The capacity of cells to maintain proteostasis requires precise control and coordination of protein synthesis, folding, conformational maintenance, and clearance. Thus, protein degradation by the ubiquitin–proteasome system (UPS) or the autophagy–lysosomal system plays an essential role in cellular functions. However, failure of the UPS or the autophagic process can lead to the development of various diseases (aging-associated diseases, cancer), thus both these pathways have become attractive targets in the treatment of protein conformational diseases, such as alpha 1-antitrypsin deficiency (AATD). The Z alpha 1-antitrypsin (Z-AAT) misfolded variant of the serine protease alpha 1-antitrypsin (AAT) is caused by a structural change that predisposes it to protein aggregation and dramatic accumulation in the form of inclusion bodies within liver hepatocytes. This can lead to clinically significant liver disease requiring liver transplantation in childhood or adulthood. Treatment of mice with autophagy enhancers was found to reduce hepatic Z-AAT aggregate levels and protect them from AATD hepatotoxicity. To date, liver transplantation is the only curative therapeutic option for patients with AATD-mediated liver disease. Therefore, the development and discovery of new therapeutic approaches to delay or overcome disease progression is a top priority. Herein, we review AATD-mediated liver disease and the overall process of autophagy. We highlight the role of this system in the regulation of Z-variant degradation and its implication in AATD-medicated liver disease, including some open questions that remain challenges in the field and require further elucidation. Finally, we discuss how manipulation of autophagy could provide multiple routes of therapeutic benefit in AATD-mediated liver disease.

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ATP depletion and mitochondrial functional loss during ischemia in slow and fast heart-rate hearts

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1990.259.6.h1759 ◽

1990 ◽

Vol 259 (6) ◽

pp. H1759-H1766 ◽

Cited By ~ 5

Author(s):

W. Rouslin ◽

C. W. Broge ◽

I. L. Grupp

Keyword(s):

Mitochondrial Function ◽

Atp Depletion ◽

Mitochondrial Atpase ◽

Small Contribution ◽

Bicarbonate Buffer ◽

Tissue Ph ◽

Atp Production ◽

Dog Heart ◽

Rat Hearts

In the present study, isolated dog and rat hearts were perfused in the Langendorff mode with Krebs bicarbonate buffer in the absence and presence of 10(-5) M oligomycin. The perfusion protocols employed allowed tissue pH to drop during subsequent ischemic incubations essentially as it would in blood-perfused hearts. Tissue pH, ATP, lactate, and mitochondrial respiratory function were measured during the course of subsequent zero-flow ischemic incubations. The adenosinetriphosphatase (ATPase) activities attributable to both mitochondrial and nonmitochondrial ATPases in sonicated heart homogenates and the actomyosin ATPase in isolated cardiac myofibrils were measured in both species. Consistent with earlier results with a different model in which tissue pH was buffered during the ischemic incubations [W. Rouslin, J. L. Erickson, and R. J. Solaro. Am. J. Physiol. 250 (Heart Circ. Physiol. 19): H503-H508, 1986], the inhibition of the mitochondrial ATPase in situ by oligomycin markedly slowed both tissue ATP depletion and the loss of mitochondrial function during ischemia in the dog. However, oligomycin had only a very small and transient effect on ATP depletion and mitochondrial function in the rat. This was apparently so because of the fivefold higher rate of glycolytic ATP production as well as the nearly threefold higher total nonmitochondrial ATPase activity of ischemic rat compared with ischemic dog heart. These results suggest that although the inhibition of the mitochondrial ATPase makes a major contribution to ATP conservation in ischemic dog heart, it makes only a very small contribution in rat.

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Phytochemicals from the Cocoa Shell Modulate Mitochondrial Function, Lipid and Glucose Metabolism in Hepatocytes via Activation of FGF21/ERK, AKT, and mTOR Pathways

Antioxidants ◽

10.3390/antiox11010136 ◽

2022 ◽

Vol 11 (1) ◽

pp. 136

Author(s):

Miguel Rebollo-Hernanz ◽

Yolanda Aguilera ◽

Maria A. Martin-Cabrejas ◽

Elvira Gonzalez de Gonzalez de Mejia

Keyword(s):

Oxidative Stress ◽

Mitochondrial Function ◽

Phosphoenolpyruvate Carboxykinase ◽

Fatty Acid Synthase ◽

Cell Model ◽

Fibroblast Growth Factor 21 ◽

Alcoholic Fatty Liver ◽

Atp Production ◽

Cocoa Shell

The cocoa shell is a by-product that may be revalorized as a source of bioactive compounds to prevent chronic cardiometabolic diseases. This study aimed to investigate the phytochemicals from the cocoa shell as targeted compounds for activating fibroblast growth factor 21 (FGF21) signaling and regulating non-alcoholic fatty liver disease (NAFLD)-related biomarkers linked to oxidative stress, mitochondrial function, and metabolism in hepatocytes. HepG2 cells treated with palmitic acid (PA, 500 µmol L−1) were used in an NAFLD cell model. Phytochemicals from the cocoa shell (50 µmol L−1) and an aqueous extract (CAE, 100 µg mL−1) enhanced ERK1/2 phosphorylation (1.7- to 3.3-fold) and FGF21 release (1.4- to 3.4-fold) via PPARα activation. Oxidative stress markers were reduced though Nrf-2 regulation. Mitochondrial function (mitochondrial respiration and ATP production) was protected by the PGC-1α pathway modulation. Cocoa shell phytochemicals reduced lipid accumulation (53–115%) and fatty acid synthase activity (59–93%) and prompted CPT-1 activity. Glucose uptake and glucokinase activity were enhanced, whereas glucose production and phosphoenolpyruvate carboxykinase activity were diminished. The increase in the phosphorylation of the insulin receptor, AKT, AMPKα, mTOR, and ERK1/2 conduced to the regulation of hepatic mitochondrial function and energy metabolism. For the first time, the cocoa shell phytochemicals are proved to modulate FGF21 signaling. Results demonstrate the in vitro preventive effect of the phytochemicals from the cocoa shell on NAFLD.

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Molecular assemblies of protein degradation pathways in prokaryotes and eukaryotes

Acta Crystallographica Section A Foundations of Crystallography ◽

10.1107/s010876730709558x ◽

2007 ◽

Vol 63 (a1) ◽

pp. s196-s196

Author(s):

L. Borissenko ◽

M. Groll

Keyword(s):

Protein Degradation ◽

Degradation Pathways ◽

Molecular Assemblies

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Ccr4 is a novel shuttle factor required for ubiquitin-dependent proteolysis by the 26S proteasome

10.1101/2020.03.30.015370 ◽

2020 ◽

Author(s):

Ganapathi Kandasamy ◽

Ashis Kumar Pradhan ◽

R Palanimurugan

Keyword(s):

Saccharomyces Cerevisiae ◽

Protein Degradation ◽

Ubiquitin Proteasome System ◽

Proteasomal Degradation ◽

Rna Degradation ◽

26S Proteasome ◽

Cellular Proteins ◽

Cellular Homeostasis ◽

Substrate Degradation ◽

Ubiquitin Proteasome

AbstractDegradation of short-lived and abnormal proteins are essential for normal cellular homeostasis. In eukaryotes, such unstable cellular proteins are selectively degraded by the ubiquitin proteasome system (UPS). Furthermore, abnormalities in protein degradation by the UPS have been linked to several human diseases. Ccr4 protein is a known component of the Ccr4-Not complex, which has established roles in transcription, mRNA de-adenylation and RNA degradation etc. Excitingly in this study, we show that Ccr4 protein has a novel function as a shuttle factor that promotes ubiquitin-dependent degradation of short-lived proteins by the 26S proteasome. Using a substrate of the well-studied ubiquitin fusion degradation (UFD) pathway, we found that its UPS-mediated degradation was severely impaired upon deletion of CCR4 in Saccharomyces cerevisiae. Additionally, we show that Ccr4 binds to cellular ubiquitin conjugates and the proteasome. In contrast to Ccr4, most other subunits of the Ccr4-Not complex proteins are dispensable for UFD substrate degradation. From our findings we conclude that Ccr4 functions in the UPS as a shuttle factor targeting ubiquitylated substrates for proteasomal degradation.

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