ER-misfolded proteins become sequestered with mitochondria and impair mitochondrial function

AbstractProteostasis is a challenge for cellular organisms, as all known protein synthesis machineries are error-prone. Here we show by cell fractionation and microscopy studies that misfolded proteins formed in the endoplasmic reticulum can become associated with and partly transported into mitochondria, resulting in impaired mitochondrial function. Blocking the endoplasmic reticulum-mitochondria encounter structure (ERMES), but not the mitochondrial sorting and assembly machinery (SAM) or the mitochondrial surveillance pathway components Msp1 and Vms1, abrogated mitochondrial sequestration of ER-misfolded proteins. We term this mitochondria-associated proteostatic mechanism for ER-misfolded proteins ERAMS (ER-associated mitochondrial sequestration). We testify to the relevance of this pathway by using mutant α-1-antitrypsin as an example of a human disease-related misfolded ER protein, and we hypothesize that ERAMS plays a role in pathological features such as mitochondrial dysfunction.

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CReP mediates selective translation initiation at the endoplasmic reticulum

Science Advances ◽

10.1126/sciadv.aba0745 ◽

2020 ◽

Vol 6 (23) ◽

pp. eaba0745 ◽

Cited By ~ 2

Author(s):

Jonathan P. Kastan ◽

Elena Y. Dobrikova ◽

Jeffrey D. Bryant ◽

Matthias Gromeier

Keyword(s):

Endoplasmic Reticulum ◽

Protein Synthesis ◽

Translation Initiation ◽

Stress Responses ◽

Spatial Organization ◽

Acute Stress ◽

Cell Fractionation ◽

Local Protein Synthesis ◽

Eif2α Phosphorylation ◽

Selective Translation

Eukaryotic protein synthesis control at multiple levels allows for dynamic, selective responses to diverse conditions, but spatial organization of translation initiation machinery as a regulatory principle has remained largely unexplored. Here we report on a role of constitutive repressor of eIF2α phosphorylation (CReP) in translation of poliovirus and the endoplasmic reticulum (ER)–resident chaperone binding immunoglobulin protein (BiP) at the ER. Functional, proximity-dependent labeling and cell fractionation studies revealed that CReP, through binding eIF2α, anchors translation initiation machinery at the ER and enables local protein synthesis in this compartment. This ER site was protected from the suppression of cytoplasmic protein synthesis by acute stress responses, e.g., phosphorylation of eIF2α(S51) or mTOR blockade. We propose that partitioning of translation initiation machinery at the ER enables cells to maintain active translation during stress conditions associated with global protein synthesis suppression.

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AMP-Activated Protein Kinase Protects Cardiomyocytes against Hypoxic Injury through Attenuation of Endoplasmic Reticulum Stress

Molecular and Cellular Biology ◽

10.1128/mcb.25.21.9554-9575.2005 ◽

2005 ◽

Vol 25 (21) ◽

pp. 9554-9575 ◽

Cited By ~ 261

Author(s):

Kazuo Terai ◽

Yoshimune Hiramoto ◽

Mitsuru Masaki ◽

Shoko Sugiyama ◽

Tadashi Kuroda ◽

...

Keyword(s):

Endoplasmic Reticulum ◽

Protein Synthesis ◽

Protein Kinase ◽

Er Stress ◽

Misfolded Proteins ◽

Hypoxic Injury ◽

Caspase 12 ◽

Inhibition Of Protein Synthesis ◽

Cardioprotective Effects ◽

Amp Activated Protein Kinase

ABSTRACT Oxygen deprivation leads to the accumulation of misfolded proteins in the endoplasmic reticulum (ER), causing ER stress. Under conditions of ER stress, inhibition of protein synthesis and up-regulation of ER chaperone expression reduce the misfolded proteins in the ER. AMP-activated protein kinase (AMPK) is a key regulatory enzyme involved in energy homeostasis during hypoxia. It has been shown that AMPK activation is associated with inhibition of protein synthesis via phosphorylation of elongation factor 2 (eEF2) in cardiomyocytes. We therefore examined whether AMPK attenuates hypoxia-induced ER stress in neonatal rat cardiomyocytes. We found that hypoxia induced ER stress, as assessed by the expression of CHOP and BiP and cleavage of caspase 12. Knockdown of CHOP or caspase 12 through small interfering RNA (siRNA) resulted in decreased expression of cleaved poly(ADP-ribose) polymerase following exposure to hypoxia. We also found that hypoxia-induced CHOP expression and cleavage of caspase 12 were significantly inhibited by pretreatment with 5-aminoimidazole-4-carboxyamide-1-β-d-ribofuranoside (AICAR), a pharmacological activator of AMPK. In parallel, adenovirus expressing dominant-negative AMPK significantly attenuated the cardioprotective effects of AICAR. Knockdown of eEF2 phosphorylation using eEF2 kinase siRNA abolished these cardioprotective effects of AICAR. Taken together, these findings demonstrate that activation of AMPK contributes to protection of the heart against hypoxic injury through attenuation of ER stress and that attenuation of protein synthesis via eEF2 inactivation may be the mechanism of cardioprotection by AMPK.

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Yeast Vps13 promotes mitochondrial function and is localized at membrane contact sites

Molecular Biology of the Cell ◽

10.1091/mbc.e16-02-0112 ◽

2016 ◽

Vol 27 (15) ◽

pp. 2435-2449 ◽

Cited By ~ 70

Author(s):

Jae-Sook Park ◽

Mary K. Thorsness ◽

Robert Policastro ◽

Luke L. McGoldrick ◽

Nancy M. Hollingsworth ◽

...

Keyword(s):

Endoplasmic Reticulum ◽

Mitochondrial Dysfunction ◽

Mitochondrial Function ◽

Protein Sorting ◽

Growth Conditions ◽

Eukaryotic Cells ◽

Cellular Functions ◽

Membrane Contact Sites ◽

Contact Sites ◽

Membrane Contact

The Vps13 protein family is highly conserved in eukaryotic cells. Mutations in human VPS13 genes result in a variety of diseases, such as chorea acanthocytosis (ChAc), but the cellular functions of Vps13 proteins are not well defined. In yeast, there is a single VPS13 orthologue, which is required for at least two different processes: protein sorting to the vacuole and sporulation. This study demonstrates that VPS13 is also important for mitochondrial integrity. In addition to preventing transfer of DNA from the mitochondrion to the nucleus, VPS13 suppresses mitophagy and functions in parallel with the endoplasmic reticulum–mitochondrion encounter structure (ERMES). In different growth conditions, Vps13 localizes to endosome–mitochondrion contacts and to the nuclear–vacuole junctions, indicating that Vps13 may function at membrane contact sites. The ability of VPS13 to compensate for the absence of ERMES correlates with its intracellular distribution. We propose that Vps13 is present at multiple membrane contact sites and that separation-of-function mutants are due to loss of Vps13 at specific junctions. Introduction of VPS13A mutations identified in ChAc patients at cognate sites in yeast VPS13 are specifically defective in compensating for the lack of ERMES, suggesting that mitochondrial dysfunction might be the basis for ChAc.

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IP3Receptors, Mitochondria, and Ca2+Signaling: Implications for Aging

Journal of Aging Research ◽

10.4061/2011/920178 ◽

2011 ◽

Vol 2011 ◽

pp. 1-20 ◽

Cited By ~ 51

Author(s):

Jean-Paul Decuypere ◽

Giovanni Monaco ◽

Ludwig Missiaen ◽

Humbert De Smedt ◽

Jan B. Parys ◽

...

Keyword(s):

Oxidative Stress ◽

Reactive Oxygen Species ◽

Endoplasmic Reticulum ◽

Mitochondrial Dysfunction ◽

Mitochondrial Function ◽

Aging Process ◽

Reactive Oxygen ◽

Oxygen Species ◽

Intracellular Ca ◽

Uptake Mechanisms

The tight interplay between endoplasmic-reticulum-(ER-) and mitochondria-mediated Ca2+signaling is a key determinant of cellular health and cellular fate through the control of apoptosis and autophagy. Proteins that prevent or promote apoptosis and autophagy can affect intracellular Ca2+dynamics and homeostasis through binding and modulation of the intracellular Ca2+-release and Ca2+-uptake mechanisms. During aging, oxidative stress becomes an additional factor that affects ER and mitochondrial function and thus their role in Ca2+signaling. Importantly, mitochondrial dysfunction and sustained mitochondrial damage are likely to underlie part of the aging process. In this paper, we will discuss the different mechanisms that control intracellular Ca2+signaling with respect to apoptosis and autophagy and review how these processes are affected during aging through accumulation of reactive oxygen species.

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Phytochemical Nrf2 activator attenuates skeletal muscle mitochondrial dysfunction and impaired proteostasis in a preclinical model of musculoskeletal aging

10.1101/2021.06.11.448143 ◽

2021 ◽

Author(s):

Robert V Musci ◽

Kendra M Andrie ◽

Maureen A Walsh ◽

Zackary J Valenti ◽

Maryam F Afzali ◽

...

Keyword(s):

Skeletal Muscle ◽

Protein Synthesis ◽

Mitochondrial Dysfunction ◽

Mitochondrial Function ◽

Guinea Pigs ◽

Muscle Protein ◽

System Capacity ◽

Related Factor ◽

Age Related ◽

Nrf2 Activator

Musculoskeletal dysfunction is an age-related syndrome associated with impaired mitochondrial function and proteostasis. However, few interventions have tested targeting two drivers of musculoskeletal decline. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that stimulates transcription of cytoprotective genes and improves mitochondrial function. We hypothesized daily treatment with a Nrf2 activator in Hartley guinea pigs, a model of age-related musculoskeletal dysfunction, attenuates the progression of skeletal muscle mitochondrial dysfunction and impaired proteostasis, preserving musculoskeletal function. We treated 2-month- and 5-month-old male and female Hartley guinea pigs for 3 and 10 months, respectively, with the phytochemical Nrf2 activator PB125 (Nrf2a). Longitudinal assessments of voluntary mobility were measured using Any-Maze™ open-field enclosure monitoring. Cumulative skeletal muscle protein synthesis rates were measured using deuterium oxide over the final 30 days of treatment. Mitochondrial oxygen consumption in permeabilized soleus muscles was measured using ex vivo high resolution respirometry. In both sexes, Nrf2a 1) increased electron transfer system capacity; 2) attenuated the disease/age-related decline in coupled and uncoupled mitochondrial respiration; and 3) attenuated declines in protein synthesis in the myofibrillar, mitochondrial, and cytosolic subfractions of the soleus. These improvements were not associated with statistically significant prolonged maintenance of voluntary mobility in guinea pigs. Collectively, these results demonstrate that treatment with an oral Nrf2 activator contributes to maintenance of skeletal muscle mitochondrial function and proteostasis in a pre-clinical model of musculoskeletal decline. Further investigation is necessary to determine if these improvements are also accompanied by slowed progression of other aspects of musculoskeletal decline.

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DIMT1, a regulator of ribosomal biogenesis, controls β-cell protein synthesis, mitochondrial function and insulin secretion

10.1101/2020.09.27.313262 ◽

2020 ◽

Author(s):

Gaurav Verma ◽

Alexander Bowen ◽

Alexander Hamilton ◽

Jonathan Esguerra ◽

Alexandros Karagiannopoulos ◽

...

Keyword(s):

Protein Synthesis ◽

Insulin Secretion ◽

Mitochondrial Dysfunction ◽

Mitochondrial Function ◽

Cell Protein ◽

Ribosomal Biogenesis ◽

Β Cells ◽

Β Cell ◽

Ribosomal Subunits ◽

Atp Production

AbstractWe previously reported that transcription factor B1 mitochondrial (TFB1M) is involved in the pathogenesis of type 2 diabetes (T2D) owing to mitochondrial dysfunction. Here, we describe that dimethyladenosine transferase 1 homolog (DIMT1), a homologue of TFB1M, is expressed and active in pancreatic β-cells. Like TFB1M, it has been implicated in control of ribosomal RNA (rRNA) but its role in β-cells or T2D remains to be identified. Silencing of DIMT1 impacted mitochondrial function, leading to reduced expression of mitochondrial OXPHOS proteins, reduced oxygen consumption rate (OCR), dissipated mitochondrial membrane potential (ΔΨm) and caused a lower rate of ATP production (mATP). In addition, DIMT1 knockdown slowed the rate of protein synthesis. In accordance with these findings, DIMT1-deficiency perturbed insulin secretion in rodent and human β-cell lines. These effects are likely a result of destabilization of ribosomal assembly, involving NIN1 (RPN12) binding protein 1 homolog (NOB-1) and Pescadillo ribosomal biogenesis factor 1 (PES-1). These are two critical ribosomal subunits proteins, whose interactions were perturbed upon DIMT1-deficiency, thereby disturbing protein synthesis in β-cells. Thus, we have here highlighted a role of DIMT1 in ribosomal biogenesis that perturbs protein synthesis, resulting in mitochondrial dysfunction and disrupted insulin secretion, both being potential pathogenetic factors in T2D.

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The Role of the Effects of Endoplasmic Reticulum Stress on NLRP3 Inflammasome in Diabetes

Frontiers in Cell and Developmental Biology ◽

10.3389/fcell.2021.663528 ◽

2021 ◽

Vol 9 ◽

Author(s):

Shuangyu Lv ◽

Xiaotian Li ◽

Honggang Wang

Keyword(s):

Endoplasmic Reticulum ◽

Protein Synthesis ◽

Endoplasmic Reticulum Stress ◽

Nlrp3 Inflammasome ◽

Basic Research ◽

Misfolded Proteins ◽

Pyrin Domain ◽

Receptor Family ◽

Oligomerization Domain

Endoplasmic reticulum (ER) is an important organelle for the protein synthesis, modification, folding, assembly, and the transport of new peptide chains. When the folding ability of ER proteins is impaired, the accumulation of unfolded or misfolded proteins in ER leads to endoplasmic reticulum stress (ERS). The nucleotide-binding oligomerization domain-like receptor family, pyrin domain-containing 3 (NLRP3) inflammasome, can induce the maturation and secretion of interleukin-1beta (IL-1β) and IL-18 through activating caspase-1. It is associated with many diseases. Studies have shown that ERS can regulate NLRP3 inflammasome in many diseases including diabetes. However, the mechanism of the effects of ERS on NLRP3 inflammasome in diabetes has not been fully understood. This review summarizes the recent researches about the effects of ERS on NLRP3 inflammasome and the related mechanism in diabetes to provide ideas for the relevant basic research in the future.

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Neurons Putting Out the Trash: A Novel Facet of Proteostasis and Mitochondrial Quality Control

Innovation in Aging ◽

10.1093/geroni/igaa057.2633 ◽

2020 ◽

Vol 4 (Supplement_1) ◽

pp. 738-738

Author(s):

Monica Driscoll

Keyword(s):

Quality Control ◽

Mitochondrial Dysfunction ◽

Neurodegenerative Disease ◽

Human Disease ◽

Current Understanding ◽

Misfolded Proteins ◽

Mitochondrial Quality Control ◽

Considerable Evidence ◽

C Elegans ◽

Human Neurodegenerative Disease

Abstract Toxicity of misfolded proteins and mitochondrial dysfunction are pivotal factors that promote age-associated functional neuronal decline and neurodegenerative disease across species. Although these neurotoxic challenges have long been considered to be cell-intrinsic, considerable evidence now supports that misfolded human disease proteins originating in one neuron can appear in neighboring cells, a phenomenon proposed to promote pathology spread in human neurodegenerative disease. We have found that C. elegans adult neurons that express aggregating proteins can extrude large (~5µM) membrane-surrounded vesicles that can include the aggregated proteins and damaged mitochondria. We speculate that throwing out the trash may correspond to a conserved mechanism that constitutes a fundamental, but formerly unrecognized, branch of neuronal proteostasis and mitochondrial quality control. I will discuss our current understanding of the mechanisms of neuronal trash elimination.

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Platelet mitochondrial function: from regulation of thrombosis to biomarker of disease

Biochemical Society Transactions ◽

10.1042/bst20120327 ◽

2013 ◽

Vol 41 (1) ◽

pp. 118-123 ◽

Cited By ~ 93

Author(s):

Sergey Zharikov ◽

Sruti Shiva

Keyword(s):

Mitochondrial Dysfunction ◽

Present Article ◽

Mitochondrial Function ◽

Human Disease ◽

Blood Platelets ◽

Energy Generation ◽

Redox Signalling

Circulating blood platelets contain small numbers of fully functional mitochondria. Accumulating evidence demonstrates that these mitochondria regulate the pro-thrombotic function of platelets through not only energy generation, but also redox signalling and the initiation of apoptosis. Beyond its regulation of haemostasis, platelet mitochondrial function has also traditionally been used to identify and study mitochondrial dysfunction in human disease, owing to the easy accessibility of platelets compared with other metabolically active tissues. In the present article, we provide a brief overview of what is currently known about the function of mitochondria in platelets and review how platelet mitochondria have been used to study mitochondrial function in human disease.

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Spatial localization of unknown proteins in the endoplasmic reticulum predicts functions

Clinical & Investigative Medicine ◽

10.25011/cim.v30i4.2858 ◽

2007 ◽

Vol 30 (4) ◽

pp. 84

Author(s):

Michael D. Jain ◽

Hisao Nagaya ◽

Annalyn Gilchrist ◽

Miroslaw Cygler ◽

John J.M. Bergeron

Keyword(s):

Endoplasmic Reticulum ◽

Protein Folding ◽

Protein Synthesis ◽

Protein Function ◽

Protein Translocation ◽

Spatial Localization ◽

Predict Protein Function ◽

Insight Into ◽

Soluble Fractions ◽

Er Membrane

Protein synthesis, folding and degradation functions are spatially segregated in the endoplasmic reticulum (ER) with respect to the membrane and the ribosome (rough and smooth ER). Interrogation of a proteomics resource characterizing rough and smooth ER membranes subfractionated into cytosolic, membrane, and soluble fractions gives a spatial map of known proteins involved in ER function. The spatial localization of 224 identified unknown proteins in the ER is predicted to give insight into their function. Here we provide evidence that the proteomics resource accurately predicts the function of new proteins involved in protein synthesis (nudilin), protein translocation across the ER membrane (nicalin), co-translational protein folding (stexin), and distal protein folding in the lumen of the ER (erlin-1, TMX2). Proteomics provides the spatial localization of proteins and can be used to accurately predict protein function.

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