scholarly journals Inhibition of calpain-1 stabilizes TCF11/Nrf1 but does not affect its activation in response to proteasome inhibition

2018 ◽  
Vol 38 (5) ◽  
Author(s):  
Karolin Nowak ◽  
Ramona M. Taubert ◽  
Stefanie Haberecht ◽  
Simone Venz ◽  
Elke Krüger
Keyword(s):  
Transcription Factor ◽  
Nuclear Translocation ◽  
Cultured Cells ◽  
Redox Homeostasis ◽  
Proteasome Inhibition ◽  
Calcium Dependent ◽  
Proteotoxic Stress ◽  
Chemical Inhibitors ◽  
Membrane Bound

Protein degradation is essential to compensate for the damaging effects of proteotoxic stress. To ensure protein and redox homeostasis in response to proteasome inhibition, the cleavage and nuclear translocation of the endoplasmic reticulum (ER)-bound transcription factor TCF11/Nrf1 (NFE2L1) is crucial for the activation of rescue factors including the synthesis of new proteasomal subunits. Even though TCF11/Nrf1 is an essential transcription factor, the exact mechanisms by which it is activated and stabilized are not fully understood. It was previously shown that the calcium-dependent protease calpain-1 interacts with TCF11/Nrf1 and the TCF11/Nrf1 cleavage site is a potential calpain target. Here, we tested the hypothesis that calpain-1 or -2 cleave TCF11/Nrf1. However, we did not find a role for calpain-1 or -2 in the activation of TCF11/Nrf1 after proteasome inhibition neither by using chemical inhibitors nor siRNA-mediated knockdown or overexpression of calpain subunits. Instead, we found that TCF11/Nrf1 is digested by calpain-1 in vitro and that calpain-1 inhibition slows down the degradation of membrane-bound TCF11/Nrf1 by the proteasome in cultured cells. Thus, we provide evidence that calpain-1 is involved in the degradation of TCF11/Nrf1. Furthermore, we confirmed DDI2 as an essential factor for TCF11/Nrf1 activation and demonstrate an undefined role of DDI2 and calpain-1 in TCF11/Nrf1 stability.

scholarly journals RIP3 impedes transcription factor EB to suppress autophagic degradation in septic acute kidney injury

2021 ◽  
Vol 12 (6) ◽  
Author(s):  
Ruizhao Li ◽  
Xingchen Zhao ◽  
Shu Zhang ◽  
Wei Dong ◽  
Li Zhang ◽  
...  
Keyword(s):  
Acute Kidney Injury ◽  
Transcription Factor ◽  
Nuclear Translocation ◽  
Kidney Injury ◽  
Septic Acute Kidney Injury ◽  
Transcription Factor Eb ◽  
Autophagic Degradation ◽  
Lps Treatment

AbstractAutophagy is an important renal-protective mechanism in septic acute kidney injury (AKI). Receptor interacting protein kinase 3 (RIP3) has been implicated in the renal tubular injury and renal dysfunction during septic AKI. Here we investigated the role and mechanism of RIP3 on autophagy in septic AKI. We showed an activation of RIP3, accompanied by an accumulation of the autophagosome marker LC3II and the autophagic substrate p62, in the kidneys of lipopolysaccharide (LPS)-induced septic AKI mice and LPS-treated cultured renal proximal tubular epithelial cells (PTECs). The lysosome inhibitor did not further increase the levels of LCII or p62 in LPS-treated PTECs. Moreover, inhibition of RIP3 attenuated the aberrant accumulation of LC3II and p62 under LPS treatment in vivo and in vitro. By utilizing mCherry-GFP-LC3 autophagy reporter mice in vivo and PTECs overexpression mRFP-GFP-LC3 in vitro, we observed that inhibition of RIP3 restored the formation of autolysosomes and eliminated the accumulated autophagosomes under LPS treatment. These results indicated that RIP3 impaired autophagic degradation, contributing to the accumulation of autophagosomes. Mechanistically, the nuclear translocation of transcription factor EB (TFEB), a master regulator of the lysosome and autophagy pathway, was inhibited in LPS-induced mice and LPS-treated PTECs. Inhibition of RIP3 restored the nuclear translocation of TFEB in vivo and in vitro. Co-immunoprecipitation further showed an interaction of RIP3 and TFEB in LPS-treated PTECs. Also, the expression of LAMP1 and cathepsin B, two potential target genes of TFEB involved in lysosome function, were decreased under LPS treatment in vivo and in vitro, and this decrease was rescued by inhibiting RIP3. Finally, overexpression of TFEB restored the autophagic degradation in LPS-treated PTECs. Together, the present study has identified a pivotal role of RIP3 in suppressing autophagic degradation through impeding the TFEB-lysosome pathway in septic AKI, providing potential therapeutic targets for the prevention and treatment of septic AKI.

scholarly journals ELAPOR1 is a secretory granule maturation-promoting factor that is lost during paligenosis

2021 ◽  
Author(s):  
Charles J. Cho ◽  
Dongkook Park ◽  
Jason C. Mills
Keyword(s):  
Transcription Factor ◽  
Secretory Granule ◽  
Cultured Cells ◽  
Tissue Injury ◽  
Pancreatic Acinar Cells ◽  
Secretory Cells ◽  
Spectrometric Analysis ◽  
Granule Maturation

A single transcription factor, MIST1 (BHLHA15), maximizes secretory function in diverse secretory cells (like pancreatic acinar cells) by transcriptionally upregulating genes that elaborate secretory architecture. Here, we show that the scantly-studied MIST1 target, ELAPOR1, is an evolutionarily conserved, novel Mannose-6-phosphate receptor (M6PR) domain-containing protein. ELAPOR1 expression was specific to zymogenic cells (ZCs, the MIST1-expressing population in the stomach). ELAPOR1 expression was lost as tissue injury caused ZCs to undergo paligenosis (ie, to become metaplastic and reenter the cell cycle). In cultured cells, ELAPOR1 trafficked with cis-Golgi resident proteins and with the trans-Golgi and late endosome protein: cation-independent M6PR. Secretory vesicle trafficking was disrupted by expression of ELAPOR1 truncation mutants. Mass spectrometric analysis of co-immunoprecipitated proteins showed ELAPOR1 and CI-M6PR shared many binding partners. However, CI-M6PR and ELAPOR1 must function differently, as CI-M6PR co-immunoprecipitated more lysosomal proteins and was not decreased during paligenosis in vivo. We generated Elapor1−/− mice to determine ELAPOR1 function in vivo. Consistent with in vitro findings, secretory granule maturation was defective in Elapor1−/− ZCs. Our results identify a role for ELAPOR1 in secretory granule maturation and help clarify how a single transcription factor maintains mature exocrine cell architecture in homeostasis and helps dismantles it during paligenosis.

scholarly journals The Nrf2/HO-1 Axis in Cancer Cell Growth and Chemoresistance

2016 ◽  
Vol 2016 ◽  
pp. 1-14 ◽  
Author(s):  
A. L. Furfaro ◽  
N. Traverso ◽  
C. Domenicotti ◽  
S. Piras ◽  
L. Moretta ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Nuclear Translocation ◽  
Tumour Progression ◽  
Redox Homeostasis ◽  
Heme Oxygenase 1 ◽  
Related Factor ◽  
Inhibitory Protein ◽  
Cancer Cell Growth ◽  
Promising Target ◽  
Anticancer Treatment

The transcription factor, nuclear factor erythroid 2 p45-related factor 2 (Nrf2), acts as a sensor of oxidative or electrophilic stresses and plays a pivotal role in redox homeostasis. Oxidative or electrophilic agents cause a conformational change in the Nrf2 inhibitory protein Keap1 inducing the nuclear translocation of the transcription factor which, through its binding to the antioxidant/electrophilic response element (ARE/EpRE), regulates the expression of antioxidant and detoxifying genes such as heme oxygenase 1 (HO-1). Nrf2 and HO-1 are frequently upregulated in different types of tumours and correlate with tumour progression, aggressiveness, resistance to therapy, and poor prognosis. This review focuses on the Nrf2/HO-1 stress response mechanism as a promising target for anticancer treatment which is able to overcome resistance to therapies.

scholarly journals LOX-1 scavenger receptor mediates calcium-dependent recognition of phosphatidylserine and apoptotic cells

2005 ◽  
Vol 393 (1) ◽  
pp. 107-115 ◽  
Author(s):  
Jane E. Murphy ◽  
Daryl Tacon ◽  
Philip R. Tedbury ◽  
Jonathan M. Hadden ◽  
Stuart Knowling ◽  
...  
Keyword(s):  
Cultured Cells ◽  
Low Density Lipoprotein ◽  
Scavenger Receptor ◽  
Density Lipoprotein ◽  
Low Density ◽  
Dependent Manner ◽  
Oxidized Low Density Lipoprotein ◽  
Bivalent Cation ◽  
Calcium Dependent

The LOX-1 (lectin-like oxidized low-density lipoprotein receptor-1) scavenger receptor regulates vascular responses to oxidized-low-density-lipoprotein particles implicated in atherosclerotic plaque formation. LOX-1 is closely related to C-type lectins, but the mechanism of ligand recognition is not known. Here we show that human LOX-1 recognizes a key cellular phospholipid, PS (phosphatidylserine), in a Ca2+-dependent manner, both in vitro and in cultured cells. A recombinant, folded and glycosylated LOX-1 molecule binds PS, but not other phospholipids. LOX-1 recognition of PS was maximal in the presence of millimolar Ca2+ levels. Mg2+ was unable to substitute for Ca2+ in LOX-1 binding to PS, indicating a Ca2+-specific requirement for bivalent cations. LOX-1-mediated recognition of PS-containing apoptotic bodies was dependent on Ca2+ and was decreased to background levels by bivalent-cation chelation, LOX-1-blocking antibodies or PS-containing liposomes. The LOX-1 membrane protein is thus a Ca2+-dependent phospholipid receptor, revealing novel recognition of phospholipids by mammalian lectins.

scholarly journals Three cytosolic NAD-malate dehydrogenase isoforms of Arabidopsis thaliana: on the crossroad between energy fluxes and redox signaling

2020 ◽  
Vol 477 (19) ◽  
pp. 3673-3693
Author(s):  
Aleksandra Liszka ◽  
Regina Schimpf ◽  
Krupskaya Ivannova Cartuche Zaruma ◽  
Annika Buhr ◽  
Thorsten Seidel ◽  
...  
Keyword(s):  
Malate Dehydrogenase ◽  
Nuclear Translocation ◽  
Specific Activity ◽  
Redox Homeostasis ◽  
Disulfide Bridge ◽  
Glycolytic Enzyme ◽  
Cysteine Residue ◽  
Oxidative Modification ◽  
Animal Cells

In yeast and animal cells, mitochondrial disturbances resulting from imbalances in the respiratory chain require malate dehydrogenase (MDH) activities for re-directing fluxes of reducing equivalents. In plants, in addition to mitochondria, plastids use malate valves to counterbalance and maintain redox-homeostasis. Arabidopsis expresses three cytosolic MDH isoforms, namely cyMDH1, cyMDH2, and cyMDH3, the latter possessing an N-terminal extension carrying a unique cysteine residue C2. In this study, redox-effects on activity and structure of all three cyMDH isoforms were analyzed in vitro. cyMDH1 and cyMDH2 were reversibly inactivated by diamide treatment, accompanied by dimerization via disulfide-bridge formation. In contrast, cyMDH3 forms dimers and higher oligomers upon oxidation, but its low specific activity is redox-independent. In the presence of glutathione, cyMDH1 and cyMDH2 are protected from dimerization and inactivation. In contrast, cyMDH3 still dimerizes but does not form oligomers any longer. From analyses of single and double cysteine mutants and structural modeling of cyMDH3, we conclude that the presence of C2 and C336 allows for multiple cross-links in the higher molecular mass complexes comprising disulfides within the dimer as well as between monomers of two different dimers. Furthermore, nuclear localization of cyMDH isoforms was significantly increased under oxidizing conditions in isolated Arabidopsis protoplasts, in particular of isoform cyMDH3. The unique cyMDH3 C2–C2-linked dimer is, therefore, a good candidate as a redox-sensor taking over moonlighting functions upon disturbances of energy metabolism, as shown previously for the glycolytic enzyme glyceraldehyde 3-phosphate dehydrogenase (GAPDH) where oxidative modification of the sensitive catalytic cysteine residues induces nuclear translocation.

scholarly journals ZnO NPs delay the recovery of psoriasis-like skin lesions through promoting inflammation and keratinocyte apoptosis via nuclear translocation of phosphorylated NF-κB p65 and cysteine deficiency

2020 ◽  
Author(s):  
Xuan Lai ◽  
Menglei Wang ◽  
Yixia Zhu ◽  
Xiaoli Feng ◽  
Huimin Liang ◽  
...  
Keyword(s):  
Skin Diseases ◽  
Nuclear Translocation ◽  
Normal Skin ◽  
Redox Homeostasis ◽  
Skin Lesions ◽  
Zno Nps ◽  
Inflammatory Skin Diseases ◽  
Tnf Α ◽  
Jnk Inhibitors

Abstract Background This study aimed to confirm the safety and risk of applying zinc oxide nanoparticles (ZnO NPs) to pathological skin, such as psoriasis-like skin. The majority of previous studies confirmed the safety of applying ZnO NPs to normal skin. However, we know very little about the risks of using sunscreen, cosmetics and topical drugs containing ZnO NPs for individuals with skin diseases. In addition, some studies claimed that ZnO NPs can penetrate normal or pathological skin, and ZnO NPs have frequently been reported to have proinflammatory and lethal effects in vitro. Therefore, it is necessary to evaluate the safety of applying ZnO NPs to pathological skin. Results ZnO NPs passed through gaps between keratinocytes and entered stratum basale of epidermis and dermis in imiquimod (IMQ)-induced psoriasis-like skin lesions. Application of a ZnO NP-containing suspension for 3 connective days delayed the healing of the epidermal barrier; increased the expression levels of inflammatory cytokines; promoted keratinocyte apoptosis and disturbed redox homeostasis. In vitro, ZnO NPs promoted TNF-α, IL-1β and IL-6 secretion and apoptosis of recombinant-human-TNF-α-stimulated HaCaT cells. NF-κB, ERK, p38 and JNK inhibitors blocked ZnO NP-induced inflammation. JSH-23, an inhibitor of the nuclear translocation of p-NF-κB p65, and NAC, an acetylated precursor of L-cysteine, not only inhibited the ZnO NP-induced inflammation but also inhibited apoptosis and cysteine deficiency. Neither erastin nor RSL3 induced p-NF-κB p65 nuclear translocation, but they did reduce cysteine biosynthesis. Additionally, ferropstatin-1, an inhibitor of lipid peroxidation, partially rescued ZnO NP-induced decreases in cell viability and cysteine content. Conclusions ZnO NPs delay the recovery of psoriasis-like skin lesions through promoting inflammation and keratinocyte apoptosis via the nuclear translocation of phosphorylated NF-κB p65 and cysteine deficiency. This work reminds the public that ZnO NPs are not safe for pathological skin, especially in inflammatory skin diseases such as psoriasis, and has revealed a partial mechanism by which ZnO NPs delay the recovery of pathological skin, promoting the appropriate use of ZnO NPs.

scholarly journals Disabling the Protease DDI2 Attenuates the Transcriptional Activity of NRF1 and Potentiates Proteasome Inhibitor Cytotoxicity

2020 ◽  
Vol 21 (1) ◽  
pp. 327 ◽  
Author(s):  
Amy Northrop ◽  
Janakiram R. Vangala ◽  
Alex Feygin ◽  
Senthil K. Radhakrishnan
Keyword(s):  
Transcription Factor ◽  
Proteasome Inhibitor ◽  
Mammalian Cells ◽  
Active Form ◽  
Cancer Cell Line ◽  
Proteasome Inhibition ◽  
Proteolytic Processing ◽  
Related Factor ◽  
Compensatory Mechanism ◽  
Proteotoxic Stress

Proteasome inhibition is used therapeutically to induce proteotoxic stress and trigger apoptosis in cancer cells that are highly dependent on the proteasome. As a mechanism of resistance, inhibition of the cellular proteasome induces the synthesis of new, uninhibited proteasomes to restore proteasome activity and relieve proteotoxic stress in the cell, thus evading apoptosis. This evolutionarily conserved compensatory mechanism is referred to as the proteasome-bounce back response and is orchestrated in mammalian cells by nuclear factor erythroid derived 2-related factor 1 (NRF1), a transcription factor and master regulator of proteasome subunit genes. Upon synthesis, NRF1 is cotranslationally inserted into the endoplasmic reticulum (ER), then is rapidly retrotranslocated into the cytosol and degraded by the proteasome. In contrast, during conditions of proteasome inhibition or insufficiency, NRF1 escapes degradation, is proteolytically cleaved by the aspartyl protease DNA damage inducible 1 homolog 2 (DDI2) to its active form, and enters the nucleus as an active transcription factor. Despite these insights, the cellular compartment where the proteolytic processing step occurs remains unclear. Here we further probed this pathway and found that NRF1 can be completely retrotranslocated into the cytosol where it is then cleaved and activated by DDI2. Furthermore, using a triple-negative breast cancer cell line MDA-MB-231, we investigated the therapeutic utility of attenuating DDI2 function. We found that DDI2 depletion attenuated NRF1 activation and potentiated the cytotoxic effects of the proteasome inhibitor carfilzomib. More importantly, expression of a point-mutant of DDI2 that is protease-dead recapitulated these effects. Taken together, our results provide a strong rationale for a combinational therapy that utilizes inhibition of the proteasome and the protease function of DDI2. This approach could expand the repertoire of cancer types that can be successfully treated with proteasome inhibitors in the clinic.

scholarly journals Activation of the STAT6 transcription factor in Jurkat T-cells by the herpesvirus saimiri Tip protein

2012 ◽  
Vol 93 (2) ◽  
pp. 330-340 ◽  
Author(s):  
Yuri Kim ◽  
Eun-Kyung Kwon ◽  
Ju-Hong Jeon ◽  
Insuk So ◽  
In-Gyu Kim ◽  
...  
Keyword(s):  
T Cells ◽  
Transcription Factor ◽  
T Cell ◽  
Transcriptional Activation ◽  
Nuclear Translocation ◽  
Cell Transformation ◽  
Herpesvirus Saimiri ◽  
Viral Gene ◽  
Jurkat T Cells

Herpesvirus saimiri (HVS), a T-lymphotropic monkey herpesvirus, induces fulminant T-cell lymphoma in non-natural primate hosts. In addition, it can immortalize human T-cells in vitro. HVS tyrosine kinase-interacting protein (Tip) is an essential viral gene required for T-cell transformation both in vitro and in vivo. In this study, we found that Tip interacts with the STAT6 transcription factor and induces phosphorylation of STAT6 in T-cells. The interaction with STAT6 requires the Tyr127 residue and Lck-binding domain of Tip, which are indispensable for interleukin (IL)-2-independent T-cell transformation by HVS. It was also demonstrated that Tip induces nuclear translocation of STAT6, as well as activation of STAT6-dependent transcription in Jurkat T-cells. Interestingly, the phosphorylated STAT6 mainly colocalized with vesicles containing Tip within T-cells, but was barely detectable in the nucleus. However, nuclear translocation of phospho-STAT6 and transcriptional activation of STAT6 by IL-4 stimulation were not affected significantly in T-cells expressing Tip. Collectively, these findings suggest that the constitutive activation of STAT6 by Tip in T-cells may contribute to IL-2-independent T-cell transformation by HVS.

Ataxia telangiectasia-mutated, a DNA damage-inducible kinase, contributes to high NaCl-induced nuclear localization of transcription factor TonEBP/OREBP

2005 ◽  
Vol 289 (3) ◽  
pp. F506-F511 ◽  
Author(s):  
Zheng Zhang ◽  
Joan D. Ferraris ◽  
Carlos E. Irarrazabal ◽  
Natalia I. Dmitrieva ◽  
Jong-Hwan Park ◽  
...  
Keyword(s):  
Dna Damage ◽  
Transcription Factor ◽  
Nuclear Localization ◽  
Ataxia Telangiectasia ◽  
Nuclear Translocation ◽  
Cultured Cells ◽  
Organic Osmolytes ◽  
Ataxia Telangiectasia Mutated ◽  
Atm Kinase ◽  
Element Binding Protein

High NaCl activates the transcription factor tonicity-responsive enhancer/osmotic response element binding protein (TonEBP/OREBP) by increasing its abundance and transactivation, the latter signaled by a variety of protein kinases. In addition, high NaCl causes TonEBP/OREBP to translocate into the nucleus, but little is known about the signals directing this translocation. The result is increased transcription of protective genes, including those involved in accumulation of organic osmolytes. High NaCl also damages DNA, and DNA damage activates ataxia telangiectasia-mutated (ATM) kinase through autophosphorylation on serine 1981. We previously found that ATM is involved in the high NaCl-induced increase in TonEBP/OREBP transactivation. The purpose of the present studies was to test whether ATM is also involved in high NaCl-induced TonEBP/OREBP nuclear translocation. We quantified TonEBP/OREBP in nuclear and cytoplasmic extracts from cultured cells by Western blot analysis. In COS-7 cells, wortmannin, an inhibitor of ATM, reduces high NaCl-induced nuclear translocation of TonEBP/OREBP. We used AT cells (in which ATM is inactive) to test the specificity of this effect. Nuclear translocation of native TonEBP/OREBP and of its recombinant NH2-terminal rel homology domain, which contains the nuclear localization signal, is reduced in AT cells and is restored when the cells are reconstituted with functional ATM. In conclusion, activation of ATM contributes to high NaCl-induced nuclear translocation of TonEBP/OREBP.

scholarly journals NFATC3 promotes IRF7 transcriptional activity in plasmacy­­toid dendritic cells

2016 ◽  
Vol 213 (11) ◽  
pp. 2383-2398 ◽  
Author(s):  
Musheng Bao ◽  
York Wang ◽  
Ying Liu ◽  
Peiqing Shi ◽  
Hongbo Lu ◽  
...  
Keyword(s):  
Dendritic Cells ◽  
Transcription Factor ◽  
Nuclear Translocation ◽  
Constitutive Expression ◽  
Toll Like Receptor ◽  
Cpg Dna ◽  
Specialized Function

Plasmacytoid dendritic cells (pDCs) rapidly produce large amounts of type 1 interferon (IFN) after Toll-like receptor 7 and 9 engagements. This specialized function of type 1 IFN production is directly linked to the constitutive expression of IRF7, the master transcription factor for type 1 IFN production. However, the IRF7 regulatory network in pDCs remains largely unknown. In this study, we identify that the transcription factor NFATC3 specifically binds to IRF7 and enhances IRF7-mediated IFN production. Furthermore, knockout of NFATC3 greatly reduced the CpG DNA–induced nuclear translocation of IRF7, which resulted in impaired type 1 IFN production in vitro and in vivo. In addition, we found that NFATC3 and IRF7 both bound to type 1 IFN promoters and that the NFAT binding site in IFN promoters was required for IRF7-mediated IFN expression. Collectively, our study shows that the transcription factor NFATC3 binds to IRF7 and functions synergistically to enhance IRF7-mediated IFN expression in pDCs.

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