scholarly journals Gp78 E3 ubiquitin ligase mediates both basal and damage-induced mitophagy

2018 ◽  
Author(s):  
Bharat Joshi ◽  
Yayha Mohammadzadeh ◽  
Guang Gao ◽  
Ivan R. Nabi
Keyword(s):  
Endoplasmic Reticulum ◽  
Ubiquitin Ligase ◽  
Mitochondrial Fission ◽  
E3 Ubiquitin Ligase ◽  
Endoplasmic Reticulum Membrane ◽  
Wild Type ◽  
Dual Roles ◽  
Mitochondrial Homeostasis ◽  
Fibrosarcoma Cells ◽  
Mitochondrial Volume

AbstractMitophagy, the elimination of mitochondria by the autophagy machinery, evolved to monitor mitochondrial health and maintain mitochondrial integrity. PINK1 is a sensor of mitochondrial health that recruits Parkin and other mitophagy-inducing ubiquitin ligases to depolarized mitochondria. However, mechanisms underlying mitophagic control of mitochondrial homeostasis, basal mitophagy, remain poorly understood. The Gp78 E3 ubiquitin ligase, an endoplasmic reticulum membrane protein, induces mitochondrial fission, endoplasmic reticulum-mitochondria contacts and mitophagy of depolarized mitochondria. CRISPR/Cas9 knockout of Gp78 in HT-1080 fibrosarcoma cells results in reduced ER-mitochondria contacts, increased mitochondrial volume and resistance to CCCP-induced mitophagy. Knockdown (KD) of the essential autophagy protein ATG5 increased mitochondrial volume of wild-type cells but did not impact mitochondrial volume of Gp78 knockout cells. This suggests that endogenous Gp78 actively eliminates mitochondria by autophagy in wild-type HT-1080 cells. Damage-induced mitophagy of depolarized mitochondria, in the presence of CCCP, but not basal mitophagy was prevented by knockdown of PINK1. This suggests that endogenous Gp78 plays dual roles in mitophagy induction: 1) control of mitochondrial homeostasis through mitophagy of undamaged mitochondria; and 2) elimination of damaged mitochondria through PINK1.

scholarly journals The mitochondrial E3 ubiquitin ligase MARCH5 is required for Drp1 dependent mitochondrial division

2007 ◽  
Vol 178 (1) ◽  
pp. 71-84 ◽  
Author(s):  
Mariusz Karbowski ◽  
Albert Neutzner ◽  
Richard J. Youle
Keyword(s):  
Rna Interference ◽  
Ubiquitin Ligase ◽  
Molecular Interactions ◽  
Mitochondrial Fission ◽  
Ectopic Expression ◽  
E3 Ubiquitin Ligase ◽  
Dependent Manner ◽  
Wild Type ◽  
Subcellular Trafficking ◽  
Mitochondrial Division

We identify a mitochondrial E3 ubiquitin ligase, MARCH5, as a critical regulator of mitochondrial fission. MARCH5 RING mutants and MARCH5 RNA interference induce an abnormal elongation and interconnection of mitochondria indicative of an inhibition of mitochondrial division. The aberrant mitochondrial phenotypes in MARCH5 RING mutant–expressing cells are reversed by ectopic expression of Drp1, but not another mitochondrial fission protein Fis1. Moreover, as indicated by abnormal clustering and mitochondrial accumulation of Drp1, as well as decreased cellular mobility of YFP-Drp1 in cells expressing MARCH5 RING mutants, MARCH5 activity regulates the subcellular trafficking of Drp1, likely by impacting the correct assembly at scission sites or the disassembly step of fission complexes. Loss of this activity may account for the observed mitochondrial division defects. Finally, MARCH5 RING mutants and endogenous Drp1, but not wild-type MARCH5 or Fis1, co-assemble into abnormally enlarged clusters in a Drp1 GTPase-dependent manner, suggesting molecular interactions among these proteins. Collectively, our data suggest a model in which mitochondrial division is regulated by a MARCH5 ubiquitin-dependent switch.

scholarly journals Syntaxin-17-Dependent Mitochondrial Dynamics is Essential for Protection Against Oxidative-Stress-Induced Apoptosis

Antioxidants ◽  
2019 ◽  
Vol 8 (11) ◽  
pp. 522 ◽  
Author(s):  
Wang ◽  
Xiao ◽  
Huang ◽  
Liu
Keyword(s):  
Oxidative Stress ◽  
Mitochondrial Dynamics ◽  
Mitochondrial Fission ◽  
Autophagic Flux ◽  
Wild Type ◽  
Dual Roles ◽  
Defective Mutant ◽  
U2os Cells ◽  
Induced Apoptosis

In this study, cell death induced by the oxidant tert-butylhydroperoxide (tBH) was observed in U2OS cells; this phenotype was rescued by Syntaxin 17 (STX17) knockout (KO) but the mechanism is unknown. STX17 plays dual roles in autophagosome–lysosome fusion and mitochondrial fission. However, the contribution of the two functions of STX17 to apoptosis has not been extensively studied. Here, we sought to dissect the dual roles of STX17 in oxidative-stress-induced apoptosis by taking advantage of STX17 knockout cells and an autophagosome–lysosome fusion defective mutant of STX17. We generated STX17 knockout U2OS cells using the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) system and the STX17 knockout cells were reconstituted with wild-type STX17 and its autophagosome–lysosome fusion defective mutant. Autophagy was assessed by autophagic flux assay, Monomer red fluorescent protein (mRFP)–GFP–LC3 assay and protease protection assay. Golgi, endoplasmic reticulum (ER)/ER–Golgi intermediate compartment (ERGIC) and mitochondrial dynamics were examined by staining the different indicator proteins. Apoptosis was evaluated by caspase cleavage assay. The general reactive oxygen species (ROS) were detected by flow cytometry. In STX17 complete knockout cells, sealed autophagosomes were efficiently formed but their fusion with lysosomes was less defective. The fusion defect was rescued by wild-type STX17 but not the autophagosome–lysosome fusion defective mutant. No obvious defects in Golgi, ERGIC or ER dynamics were observed. Mitochondria were significantly elongated, supporting a role of STX17 in mitochondria fission and the elongation caused by STX17 KO was reversed by the autophagosome–lysosome fusion defective mutant. The clearance of protein aggregation was compromised, correlating with the autophagy defect but not with mitochondrial dynamics. This study revealed a mixed role of STX17 in autophagy, mitochondrial dynamics and oxidative stress response. STX17 knockout cells were highly resistant to oxidative stress, largely due to the function of STX17 in mitochondrial fission rather than autophagy.

scholarly journals Deletions into an NH2-terminal hydrophobic domain result in secretion of rotavirus VP7, a resident endoplasmic reticulum membrane glycoprotein.

1985 ◽  
Vol 101 (6) ◽  
pp. 2199-2209 ◽  
Author(s):  
M S Poruchynsky ◽  
C Tyndall ◽  
G W Both ◽  
F Sato ◽  
A R Bellamy ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Integral Membrane Protein ◽  
Endoplasmic Reticulum Membrane ◽  
Wild Type ◽  
Positive Signal ◽  
Complex Type ◽  
Immunofluorescent Localization ◽  
Hydrophobic Domain ◽  
Rotavirus A ◽  
Altered Protein

Rotavirus, a non-enveloped reovirus, buds into the rough endoplasmic reticulum and transiently acquires a membrane. The structural glycoprotein, VP7, a 38-kD integral membrane protein of the endoplasmic reticulum (ER), presumably transfers to virus in this process. The gene for VP7 potentially encodes a protein of 326 amino acids which has two tandem hydrophobic domains at the NH2-terminal, each preceded by an in-frame ATG codon. A series of deletion mutants constructed from a full-length cDNA clone of the Simian 11 rotavirus VP7 gene were expressed in COS 7 cells. Products from wild-type, and mutants which did not affect the second hydrophobic domain of VP7, were localized by immunofluorescence to elements of the ER only. However, deletions affecting the second hydrophobic domain (mutants 42-61, 43-61, 47-61) showed immunofluorescent localization of VP7 which coincided with that of wheat germ agglutinin, indicating transport to the Golgi apparatus. Immunoprecipitable wild-type protein, or an altered protein lacking the first hydrophobic sequence, remained intracellular and endo-beta-N-acetylglucosaminidase H sensitive. In contrast, products of mutants 42-61, 43-61, and 47-61 were transported from the ER, and secreted. Glycosylation of the secreted molecules was inhibited by tunicamycin, resistant to endo-beta-N-acetylglucosaminidase H digestion and therefore of the N-linked complex type. An unglycosylated version of VP7 was also secreted. We suggest that the second hydrophobic domain contributes to a positive signal for ER location and a membrane anchor function. Secretion of the mutant glycoprotein implies that transport can be constitutive with the destination being dictated by an overriding compartmentalization signal.

scholarly journals N-terminal acetylation of the yeast Derlin Der1 is essential for Hrd1 ubiquitin-ligase activity toward luminal ER substrates

2013 ◽  
Vol 24 (7) ◽  
pp. 890-900 ◽  
Author(s):  
Dimitrios Zattas ◽  
David J. Adle ◽  
Eric M. Rubenstein ◽  
Mark Hochstrasser
Keyword(s):  
Endoplasmic Reticulum ◽  
Transcription Factor ◽  
Fusion Protein ◽  
Protein Degradation ◽  
Ubiquitin Ligase ◽  
Ubiquitin Ligases ◽  
Recent Analysis ◽  
Specific Class ◽  
Wild Type ◽  
Ubiquitin Ligase Activity

Two conserved ubiquitin ligases, Hrd1 and Doa10, mediate most endoplasmic reticulum–associated protein degradation (ERAD) in yeast. Degradation signals (degrons) recognized by these ubiquitin ligases remain poorly characterized. Doa10 recognizes the Deg1 degron from the MATα2 transcription factor. We previously found that deletion of the gene (NAT3) encoding the catalytic subunit of the NatB N-terminal acetyltransferase weakly stabilized a Deg1-fusion protein. By contrast, a recent analysis of several MATα2 derivatives suggested that N-terminal acetylation of these proteins by NatB was crucial for recognition by Doa10. We now analyze endogenous MATα2 degradation in cells lacking NatB and observe minimal perturbation relative to wild-type cells. However, NatB mutation strongly impairs degradation of ER-luminal Hrd1 substrates. This unexpected defect derives from a failure of Der1, a Hrd1 complex subunit, to be N-terminally acetylated in NatB mutant yeast. We retargeted Der1 to another acetyltransferase to show that it is the only ERAD factor requiring N-terminal acetylation. Preventing Der1 acetylation stimulates its proteolysis via the Hrd1 pathway, at least partially accounting for the ERAD defect observed in the absence of NatB. These results reveal an important role for N-terminal acetylation in controlling Hrd1 ligase activity toward a specific class of ERAD substrates.

scholarly journals An E3 Ubiquitin Ligase, Synoviolin, Is Involved in the Degradation of Homocysteine-Inducible Endoplasmic Reticulum Protein

2018 ◽  
Vol 41 (6) ◽  
pp. 915-919 ◽  
Author(s):  
Tomoji Maeda ◽  
Yu Fujita ◽  
Chiaki Tanabe-Fujimura ◽  
Kun Zou ◽  
Junjun Liu ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Ubiquitin Ligase ◽  
E3 Ubiquitin Ligase ◽  
Endoplasmic Reticulum Protein

The Cbl E3 Ubiquitin Ligase Negatively Regulates Erythropoiesis through Expression of the Foxo3a Transcription Factor.

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 1374-1374
Author(s):  
Terri D Richmond ◽  
Monica L Bailey ◽  
Wallace Y Langdon ◽  
Dwayne Barber
Keyword(s):  
Signal Transduction ◽  
Cell Signaling ◽  
Ubiquitin Ligase ◽  
Knockout Mice ◽  
E3 Ubiquitin Ligase ◽  
Parp Cleavage ◽  
Signal Transduction Pathways ◽  
Wild Type ◽  
Erythroid Progenitors ◽  
Deficient Mice

Abstract Erythropoietin (EPO) is the primary cytokine regulator of red blood cell (RBC) progenitor growth, survival and differentiation. EPO stimulation is regulated by EPO binding to its cognate ligand, the EPO receptor (EPO-R), and activating the primary associated tyrosine kinase, JAK2. The critical importance of EPO, EPO-R and JAK2 to erythropoiesis is demonstrated by the fatal embryonic anemia that develops upon EPO, EPO-R or JAK2 deletion. Intracellular signal transduction pathways regulating growth, survival and differentiation downstream of the EPO-R and JAK2 are well documented. However, relatively little is known about down-regulation of EPO-R signal transduction pathways at this time. Our laboratory has previously demonstrated that EPO stimulation leads to Cbltyrosine phosphorylation and subsequent recruitment of Crk-C3G, leading to Rap1activation. In addition, Cbl serves as an adaptor protein linking to PI 3 kinase and Rasand targets receptor tyrosine kinases for ubiquitination and proteasomal degradation. Cbl knockout mice have been generated and have defects in stem and T cell signaling pathways. Elevated platelet numbers and splenomegaly was observed, suggesting that Cbl −/− mice may have defects in megakaryocyte/erythroid progenitors or more committed cells in each lineage. The objective of this studyis to determine whether Cbl affects erythropoiesis and EPO-dependent signaling. Resting Cbl −/− mice (in the C57Bl/6 background) have increased numbers of Burst Forming Unit-Erythroid and Colony Forming Unit-Erythroid (CFU-E) cells. Furthermore, there is a 3-fold elevation of splenic CFU-E numbers. Erythroid differentiation was monitored via expression of the Transferrin Receptor (CD71) and Ter119. Cbl-deficient mice have delayed differentiation in the bone marrow with diminished CD71-Ter119+ cells. Increased apoptosis is observed in Ter119+ erythroid cells isolated from Cbl −/− mice as determined by Annexin V staining and confirmed by increased PARP cleavage. Interestingly, reactive oxygen species in wild type and Cbl-deficient mice remain unchanged. Despite normal resting hematologic parameters, serum EPO concentrations are elevated in Cbl knockout mice. Serum VEGF levels are comparable between wild type and Cbl −/− mice, suggesting that the EPO effect is specific to the erythroid lineage and not an effect of hypoxia. Notable differences in wild type and Cbl −/− mice were observed when stress erythropoiesiswas induced by phenylhydrazine-mediated anemia. Cbl-deficient mice respond with enhanced hematocrit recovery and increased reticulocyte production. EPO-dependent Aktphosphorylation is hypersensitive in Cbl −/− splenic erythroblasts. Interestingly, expression ofFoxo3a was stabilized in Cbl −/− splenic erythroblasts, suggesting that Cbl degrades Foxo3a in a direct or indirect manner. Given the importance of Foxo3a in regulating erythropoiesis, we are currently determining whether Cbl targets Foxo3a for ubiquitin-mediated degradation. These data demonstrate the remarkable homeostatic ability of the mouse to retain normal RBC concentrations in the peripheral blood despite elevated erythroid progenitors and cell signaling. Importantly, these studies are the first to phenotypically explore the effects of genetic ablation of an EPO-responsive E3 ubiquitin ligase in erythropoiesis.

Unique Gain-of-Function of Mutated c-CBL Tumor Suppresor in Myeloid Neoplasms.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 2970-2970
Author(s):  
Masashi Sanada ◽  
Takahiro Suzuki ◽  
Lee-Yung Shih ◽  
Makoto Otsu ◽  
Motohiro Kato ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Tyrosine Kinases ◽  
E3 Ubiquitin Ligase ◽  
Tumour Suppressor ◽  
Wild Type ◽  
Gain Of Function ◽  
Hematopoietic Stem ◽  
Myeloid Neoplasms ◽  
Ubiquitin Ligase Activity ◽  
Type C

Abstract Abstract 2970 Poster Board II-946 Acquired uniparental disomy (aUPD) is a common feature of myeloid neoplasms, especially myelodysplastic syndromes (MDS) / myeloploriferative neoplasms (MPN). aUPDs preferentially affected several chromosomal arms in distinct subsets of patients, and frequently associated with mutated oncogenes and tumour suppressor genes. Among these, the most common aUPDs are those involving 11q, which defined a unique subset of myeloid neoplasms that were clinically characterized by frequent diagnosis of chronic myelomonocytic leukaemia (CMML) with normal karyotypes. Recently, we and other groups reported that 11qUPD are genetically defined by the presence of homozygous mutations of C-CBL. C-CBL proto-oncogene is the cellular homolog of the v-Cbl transforming gene of the Cas NS-1 murine leukemia virus. C-CBL is thought to be involved in the negative modulation of tyrosine kinase signalling, primarily through their E3 ubiquitin ligase activity that is responsible for the down-regulation of activated tyrosine kinases. As expected from the latter function, we demonstrated that wild-type C-CBL has tumour suppressor functions; c-Cbl null mice showed expanded hematopoietic progenitor pools, promoted blastic crisis induced by a bcr/abl transgene, and spontaneous development of late-onset invasive cancers in complete penetrance. On the other hand, mutated C-CBL showed clear oncogenic potential; all tested mutants strongly transformed NIH3T3 fibroblasts, and prolonged replating capacity of hematopoietic progenitors. All reported C-CBL mutations involved the linker-RING finger domains that are central to the E3 ubiquitin ligase activity. We demonstrated that mutated C-CBL not only lost their E3 ubiquitin ligase activity, but also inhibited that of wild-type C-CBL, leading to prolonged activation of a broad spectrum of tyrosine kinases after ligand stimulations in fibroblasts and hematopoietic cells. In accordance with this, c-Cbl−/− hematopoietic stem/progenitor cells (HSPCs) showed enhanced sensitivity to a variety of cytokines, but unexpectedly, transduction of C-CBL mutants into c-Cbl−/− HSPCs further augmented the sensitivity to a broader spectrum of cytokines, indicating the presence of gain-of-function in mutated C-CBL that is not simply mediated by inhibition of wild-type C-CBL functions. The gain-of-function effects of C-CBL mutants on cytokine sensitivity of HSPCs largely disappeared in the c-Cbl+/+ background or by co-transduction of wild-type C-CBL, which may suggest the pathogenic importance of loss of wild-type c-Cbl alleles found in most cases of C-CBL-mutated myeloid neoplasms. Our findings provide a novel insight into a role of gain-of-function mutations of a tumour suppressor associated with aUPD in the pathogenesis of some of myeloid cancer subsets. Currently, further functional studies regarding the molecular mechanism of the gain-of-function are ongoing. Disclosures: Omine: Alexion: Consultancy, Research Funding.

scholarly journals RING finger palmitoylation of the endoplasmic reticulum Gp78 E3 ubiquitin ligase

FEBS Letters ◽  
2012 ◽  
Vol 586 (16) ◽  
pp. 2488-2493 ◽  
Author(s):  
Maria Fairbank ◽  
Kun Huang ◽  
Alaa El-Husseini ◽  
Ivan R. Nabi
Keyword(s):  
Endoplasmic Reticulum ◽  
Ubiquitin Ligase ◽  
E3 Ubiquitin Ligase ◽  
Ring Finger

scholarly journals The Calcineurin-FoxO-MuRF1 signaling pathway regulates myofibril integrity in cardiomyocytes

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Hirohito Shimizu ◽  
Adam D Langenbacher ◽  
Jie Huang ◽  
Kevin Wang ◽  
Georg Otto ◽  
...  
Keyword(s):  
Signaling Pathway ◽  
Ubiquitin Ligase ◽  
Degradation Mechanism ◽  
E3 Ubiquitin Ligase ◽  
Proteasome Activity ◽  
Wild Type ◽  
Structural Remodeling ◽  
Proteasome Degradation ◽  
Calcineurin Activity ◽  
Functional Deterioration

Altered Ca2+ handling is often present in diseased hearts undergoing structural remodeling and functional deterioration. However, whether Ca2+ directly regulates sarcomere structure has remained elusive. Using a zebrafish ncx1 mutant, we explored the impacts of impaired Ca2+ homeostasis on myofibril integrity. We found that the E3 ubiquitin ligase murf1 is upregulated in ncx1-deficient hearts. Intriguingly, knocking down murf1 activity or inhibiting proteasome activity preserved myofibril integrity, revealing a MuRF1-mediated proteasome degradation mechanism that is activated in response to abnormal Ca2+ homeostasis. Furthermore, we detected an accumulation of the murf1 regulator FoxO in the nuclei of ncx1-deficient cardiomyocytes. Overexpression of FoxO in wild type cardiomyocytes induced murf1 expression and caused myofibril disarray, whereas inhibiting Calcineurin activity attenuated FoxO-mediated murf1 expression and protected sarcomeres from degradation in ncx1-deficient hearts. Together, our findings reveal a novel mechanism by which Ca2+ overload disrupts myofibril integrity by activating a Calcineurin-FoxO-MuRF1-proteosome signaling pathway.

scholarly journals Novel regulatory roles of Mff and Drp1 in E3 ubiquitin ligase MARCH5–dependent degradation of MiD49 and Mcl1 and control of mitochondrial dynamics

2017 ◽  
Vol 28 (3) ◽  
pp. 396-410 ◽  
Author(s):  
Edward Cherok ◽  
Shan Xu ◽  
Sunan Li ◽  
Shweta Das ◽  
W. Alex Meltzer ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Mitochondrial Dynamics ◽  
Mitochondrial Fission ◽  
Critical Role ◽  
E3 Ubiquitin Ligase ◽  
Mitochondrial Morphology ◽  
Ubiquitinated Proteins ◽  
Terminal Domain ◽  
Degradation Rates ◽  
And Control

MARCH5, an OMM-associated E3 ubiquitin ligase, controls mitochondrial function. Despite its importance, the mechanism and factors controlling MARCH5 activity are largely unknown. Here we report that the MARCH5 C-terminal domain plays a critical role in degradation of MARCH5 substrates, likely by facilitating release of ubiquitinated proteins from the OMM. We also found that the mitochondrial fission proteins Drp1 and Mff negatively regulate MARCH5’s activity toward MiD49 and Mcl1. Knockouts of either Drp1 or Mff led to reduced expression, shorter half-lives, and increased ubiquitination of MiD49 and Mcl1. Effects of Mff and Drp1 depletion on degradation rates and ubiquitination of Mcl1 and MiD49 were eliminated in Drp1−/−/MARCH5−/− and Mff−/−/MARCH5−/− cells. Our data show that it is not mitochondrial morphology per se but rather Mff and Drp1 that directly control MARCH5. Consistently, we find that Mff is an integral component of the MARCH5/p97/Npl4 complex, which is also controlled by MARCH5’s C-terminal domain. Furthermore, not only mitochondrial fission but also fusion is regulated through Mff and Drp1 protein activities. Thus, in addition to their canonical roles in mitochondrial fission, Mff and Drp1 also act as regulatory factors that control mitochondrial fission and fusion.

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