1
|
Chatterjee S, Chakrabarty Y, Banerjee S, Ghosh S, Bhattacharyya SN. Mitochondria control mTORC1 activity-linked compartmentalization of eIF4E to regulate extracellular export of microRNAs. J Cell Sci 2020; 133:jcs250241. [PMID: 33262313 DOI: 10.1242/jcs.250241] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 11/17/2020] [Indexed: 01/08/2023] Open
Abstract
Defective intracellular trafficking and export of microRNAs (miRNAs) have been observed in growth-retarded mammalian cells having impaired mitochondrial potential and dynamics. Here, we found that uncoupling protein 2 (Ucp2)-mediated depolarization of mitochondrial membrane also results in progressive sequestration of miRNAs within polysomes and lowers their release via extracellular vesicles. Interestingly, the impaired miRNA-trafficking process in growth-retarded human cells could be reversed in the presence of Genipin, an inhibitor of Ucp2. Mitochondrial detethering of endoplasmic reticulum (ER), observed in cells with depolarized mitochondria, was found to be responsible for defective compartmentalization of translation initiation factor eIF4E to polysomes attached to ER. This caused a retarded translation process accompanied by enhanced retention of miRNAs and target mRNAs within ER-attached polysomes to restrict extracellular export of miRNAs. Reduced compartment-specific activity of the mammalian target of rapamycin complex 1 (mTORC1), the master regulator of protein synthesis, in cells with defective mitochondria or detethered ER, caused reduced phosphorylation of eIF4E-BP1 and prevented eIF4E targeting to ER-attached polysomes and miRNA export. These data suggest how mitochondrial membrane potential and dynamics, by affecting mTORC1 activity and compartmentalization, determine the subcellular localization and export of miRNAs.
Collapse
Affiliation(s)
- Susanta Chatterjee
- RNA Biology Research Laboratory, Molecular Genetics Division, CSIR-Indian Institute of Chemical Biology, Kolkata 700032, India
| | - Yogaditya Chakrabarty
- RNA Biology Research Laboratory, Molecular Genetics Division, CSIR-Indian Institute of Chemical Biology, Kolkata 700032, India
| | - Saikat Banerjee
- RNA Biology Research Laboratory, Molecular Genetics Division, CSIR-Indian Institute of Chemical Biology, Kolkata 700032, India
| | - Souvik Ghosh
- RNA Biology Research Laboratory, Molecular Genetics Division, CSIR-Indian Institute of Chemical Biology, Kolkata 700032, India
| | - Suvendra N Bhattacharyya
- RNA Biology Research Laboratory, Molecular Genetics Division, CSIR-Indian Institute of Chemical Biology, Kolkata 700032, India
| |
Collapse
|
2
|
Haugse R, Langer A, Murvold ET, Costea DE, Gjertsen BT, Gilja OH, Kotopoulis S, Ruiz de Garibay G, McCormack E. Low-Intensity Sonoporation-Induced Intracellular Signalling of Pancreatic Cancer Cells, Fibroblasts and Endothelial Cells. Pharmaceutics 2020; 12:pharmaceutics12111058. [PMID: 33171947 PMCID: PMC7694645 DOI: 10.3390/pharmaceutics12111058] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 11/01/2020] [Accepted: 11/03/2020] [Indexed: 12/13/2022] Open
Abstract
The use of ultrasound (US) and microbubbles (MB), usually referred to as sonoporation, has great potential to increase the efficacy of chemotherapy. However, the molecular mechanisms that mediate sonoporation response are not well-known, and recent research suggests that cell stress induced by US + MBs may contribute to the treatment benefit. Furthermore, there is a growing understanding that the effects of US + MBs are beyond only the cancer cells and involves the tumour vasculature and microenvironment. We treated pancreatic cancer cells (MIA PaCa-2) and stromal cells, fibroblasts (BJ) and human umbilical vein endothelial cells (HUVECs), with US ± MB, and investigated the extent of uptake of cell impermeable dye (calcein, by flow cytometry), viability (cell count, Annexin/PI and WST-1 assays) and activation of a number of key proteins in important intracellular signalling pathways immediately and 2 h after sonoporation (phospho flow cytometry). Different cell types responded differently to US ± MBs in all these aspects. In general, sonoporation induces immediate, transient activation of MAP-kinases (p38, ERK1/2), and an increase in phosphorylation of ribosomal protein S6 together with dephosphorylation of 4E-BP1. The sonoporation stress-response resembles cellular responses to electroporation and pore-forming toxins in membrane repair and restoring cellular homeostasis, and may be exploited therapeutically. The stromal cells were more sensitive to sonoporation than tumoural cells, and further efforts in optimising sonoporation-enhanced therapy should be targeted at the microenvironment.
Collapse
Affiliation(s)
- Ragnhild Haugse
- Centre for Pharmacy, Department of Clinical Science, The University of Bergen, Jonas Lies vei 65, 5021 Bergen, Norway;
- Department of Quality and Development, Hospital Pharmacies Enterprise in Western Norway, Møllendalsbakken 9, 5021 Bergen, Norway
- Centre for Cancer Biomarkers CCBIO, Department of Clinical Science, The University of Bergen, Jonas Lies vei 65, 5021 Bergen, Norway; (A.L.); (D.E.C.); (B.T.G.); (G.R.d.G.)
| | - Anika Langer
- Centre for Cancer Biomarkers CCBIO, Department of Clinical Science, The University of Bergen, Jonas Lies vei 65, 5021 Bergen, Norway; (A.L.); (D.E.C.); (B.T.G.); (G.R.d.G.)
| | - Elisa Thodesen Murvold
- KinN Therapeutics AS, Jonas Lies vei 91B, 5021 Bergen, Norway;
- Department of Clinical Medicine, The University of Bergen, Jonas Lies vei 65, 5021 Bergen, Norway; (O.H.G.); (S.K.)
| | - Daniela Elena Costea
- Centre for Cancer Biomarkers CCBIO, Department of Clinical Science, The University of Bergen, Jonas Lies vei 65, 5021 Bergen, Norway; (A.L.); (D.E.C.); (B.T.G.); (G.R.d.G.)
- Department of Clinical Medicine, The University of Bergen, Jonas Lies vei 65, 5021 Bergen, Norway; (O.H.G.); (S.K.)
| | - Bjørn Tore Gjertsen
- Centre for Cancer Biomarkers CCBIO, Department of Clinical Science, The University of Bergen, Jonas Lies vei 65, 5021 Bergen, Norway; (A.L.); (D.E.C.); (B.T.G.); (G.R.d.G.)
- Department of Internal Medicine, Hematology Section, Haukeland University Hospital, Jonas Lies vei 65, 5021 Bergen, Norway
| | - Odd Helge Gilja
- Department of Clinical Medicine, The University of Bergen, Jonas Lies vei 65, 5021 Bergen, Norway; (O.H.G.); (S.K.)
- National Centre for Ultrasound in Gastroenterology, Haukeland University Hospital, Jonas Lies vei 65, 5021 Bergen, Norway
| | - Spiros Kotopoulis
- Department of Clinical Medicine, The University of Bergen, Jonas Lies vei 65, 5021 Bergen, Norway; (O.H.G.); (S.K.)
- National Centre for Ultrasound in Gastroenterology, Haukeland University Hospital, Jonas Lies vei 65, 5021 Bergen, Norway
- EXACT Therapeutics AS, Ullernchausseen 64, 0379 Oslo, Norway
| | - Gorka Ruiz de Garibay
- Centre for Cancer Biomarkers CCBIO, Department of Clinical Science, The University of Bergen, Jonas Lies vei 65, 5021 Bergen, Norway; (A.L.); (D.E.C.); (B.T.G.); (G.R.d.G.)
| | - Emmet McCormack
- Centre for Pharmacy, Department of Clinical Science, The University of Bergen, Jonas Lies vei 65, 5021 Bergen, Norway;
- Department of Quality and Development, Hospital Pharmacies Enterprise in Western Norway, Møllendalsbakken 9, 5021 Bergen, Norway
- Centre for Cancer Biomarkers CCBIO, Department of Clinical Science, The University of Bergen, Jonas Lies vei 65, 5021 Bergen, Norway; (A.L.); (D.E.C.); (B.T.G.); (G.R.d.G.)
- KinN Therapeutics AS, Jonas Lies vei 91B, 5021 Bergen, Norway;
- Department of Clinical Science, The University of Bergen, Jonas Lies vei 65, 5021 Bergen, Norway
- Correspondence:
| |
Collapse
|
3
|
Klann K, Tascher G, Münch C. Functional Translatome Proteomics Reveal Converging and Dose-Dependent Regulation by mTORC1 and eIF2α. Mol Cell 2020; 77:913-925.e4. [PMID: 31812349 PMCID: PMC7033560 DOI: 10.1016/j.molcel.2019.11.010] [Citation(s) in RCA: 67] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 09/24/2019] [Accepted: 11/07/2019] [Indexed: 12/15/2022]
Abstract
Regulation of translation is essential during stress. However, the precise sets of proteins regulated by the key translational stress responses-the integrated stress response (ISR) and mTORC1-remain elusive. We developed multiplexed enhanced protein dynamics (mePROD) proteomics, adding signal amplification to dynamic-SILAC and multiplexing, to enable measuring acute changes in protein synthesis. Treating cells with ISR/mTORC1-modulating stressors, we showed extensive translatome modulation with ∼20% of proteins synthesized at highly reduced rates. Comparing translation-deficient sub-proteomes revealed an extensive overlap demonstrating that target specificity is achieved on protein level and not by pathway activation. Titrating cap-dependent translation inhibition confirmed that synthesis of individual proteins is controlled by intrinsic properties responding to global translation attenuation. This study reports a highly sensitive method to measure relative translation at the nascent chain level and provides insight into how the ISR and mTORC1, two key cellular pathways, regulate the translatome to guide cellular survival upon stress.
Collapse
Affiliation(s)
- Kevin Klann
- Institute of Biochemistry II, Faculty of Medicine, Goethe University, Frankfurt am Main, Germany
| | - Georg Tascher
- Institute of Biochemistry II, Faculty of Medicine, Goethe University, Frankfurt am Main, Germany
| | - Christian Münch
- Institute of Biochemistry II, Faculty of Medicine, Goethe University, Frankfurt am Main, Germany; Frankfurt Cancer Institute, Frankfurt am Main, Germany; Cardio-Pulmonary Institute, Frankfurt am Main, Germany.
| |
Collapse
|
4
|
Targeting KPNB1 overcomes TRAIL resistance by regulating DR5, Mcl-1 and FLIP in glioblastoma cells. Cell Death Dis 2019; 10:118. [PMID: 30742128 PMCID: PMC6370806 DOI: 10.1038/s41419-019-1383-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 12/16/2018] [Accepted: 01/09/2019] [Indexed: 01/08/2023]
Abstract
Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a cytokine with potential anticancer effect, but innate and adaptive TRAIL resistance in majority of cancers limit its clinical application. Karyopherin β1 (KPNB1) inhibition in cancer cells has been reported to abrogate the nuclear import of TRAIL receptor DR5 and facilitate its localization on the cell surface ready for TRAIL stimulation. However, our study reveals a more complicated mechanism. Genetic or pharmacological inhibition of KPNB1 potentiated TRAIL-induced apoptosis selectively in glioblastoma cells mainly by unfolded protein response (UPR). First, it augmented ATF4-mediated DR5 expression and promoted the assembly of death-inducing signaling complex (DISC). Second, it freed Bax and Bak from Mcl-1. Third, it downregulated FLIPL and FLIPS, inhibitors of caspase-8 cleavage, partly through upregulating ATF4–induced 4E-BP1 expression and disrupting the cap-dependent translation initiation. Meanwhile, KPNB1 inhibition-induced undesirable autophagy and accelerated cleaved caspase-8 clearance. Inhibition of autophagic flux maintained cleaved caspase-8 and aggravated apoptosis induced by KPNB1 inhibitor plus TRAIL, which were abolished by caspase-8 inhibitor. These results unveil new molecular mechanism for optimizing TRAIL-directed therapeutic efficacy against cancer.
Collapse
|
5
|
Wei Y, Meng M, Tian Z, Xie F, Yin Q, Dai C, Wang J, Zhang Q, Liu Y, Liu C, Yan F, Jiang F, Guo X. Pharmacological preconditioning with the cellular stress inducer thapsigargin protects against experimental sepsis. Pharmacol Res 2018; 141:114-122. [PMID: 30579975 DOI: 10.1016/j.phrs.2018.12.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Revised: 12/12/2018] [Accepted: 12/19/2018] [Indexed: 02/08/2023]
Abstract
Previous studies have shown that pretreatment with thapsigargin (TG), a cellular stress inducer, produced potent protective actions against various pathologic injuries. So far there is no information on the effects of TG on the development of bacterial sepsis. Using lipopolysaccharides- and cecal ligation/puncture-induced sepsis models in mice, we demonstrated that preconditioning with a single bolus administration of TG conferred significant improvements in survival. The beneficial effects of TG were not mediated by ER stress induction or changes in Toll-like receptor 4 signaling. In vivo and in cultured macrophages, we identified that TG reduced the protein production of pro-inflammatory cytokines, but exhibited no significant effects on steady state levels of their transcriptions. Direct measurement on the fraction of polysome-bound mRNAs revealed that TG reduced the translational efficiency of pro-inflammatory cytokines in macrophages. Moreover, we provided evidence suggesting that repression of the mTOR (the mammalian target of rapamycin) signaling pathway, but not activation of the PERK (protein kinase R-like endoplasmic reticulum kinase)-eIF2α (eukaryotic initiation factor 2α) pathway, might be involved in mediating the TG effects on cytokine production. In summary, our results support that pharmacological preconditioning with TG may represent a novel strategy to prevent sepsis-induced mortality and organ injuries.
Collapse
Affiliation(s)
- Yaping Wei
- Department of Physiology and Pathophysiology, School of Basic Medicine, Shandong University, Jinan, Shandong Province, China
| | - Mei Meng
- Department of Critical Care Medicine, Shandong Provincial Hospital Affiliated, Shandong University, Jinan, Shandong Province, China
| | - Zhenyu Tian
- The Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education, Chinese National Health Commission and Chinese Academy of Medical Sciences, The State and Shandong Province Joint Key Laboratory of Translational Cardiovascular Medicine, Department of Cardiology, Qilu Hospital of Shandong University, Jinan, China
| | - Fubo Xie
- Department of Radiology, Qilu Hospital of Shandong University, Jinan, Shandong Province, China
| | - Qihui Yin
- Department of Physiology and Pathophysiology, School of Basic Medicine, Shandong University, Jinan, Shandong Province, China
| | - Chaochao Dai
- Department of Physiology and Pathophysiology, School of Basic Medicine, Shandong University, Jinan, Shandong Province, China
| | - Jingjing Wang
- Department of Physiology and Pathophysiology, School of Basic Medicine, Shandong University, Jinan, Shandong Province, China
| | - Qunye Zhang
- The Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education, Chinese National Health Commission and Chinese Academy of Medical Sciences, The State and Shandong Province Joint Key Laboratory of Translational Cardiovascular Medicine, Department of Cardiology, Qilu Hospital of Shandong University, Jinan, China
| | - Yu Liu
- Department of Physiology and Pathophysiology, School of Basic Medicine, Shandong University, Jinan, Shandong Province, China
| | - Chang Liu
- Department of Physiology and Pathophysiology, School of Basic Medicine, Shandong University, Jinan, Shandong Province, China
| | - Feng Yan
- Department of Emergency, Qilu Hospital of Shandong University, Jinan, Shandong Province, China
| | - Fan Jiang
- Department of Physiology and Pathophysiology, School of Basic Medicine, Shandong University, Jinan, Shandong Province, China; The Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education, Chinese National Health Commission and Chinese Academy of Medical Sciences, The State and Shandong Province Joint Key Laboratory of Translational Cardiovascular Medicine, Department of Cardiology, Qilu Hospital of Shandong University, Jinan, China.
| | - Xiaosun Guo
- Department of Physiology and Pathophysiology, School of Basic Medicine, Shandong University, Jinan, Shandong Province, China.
| |
Collapse
|
6
|
AXER is an ATP/ADP exchanger in the membrane of the endoplasmic reticulum. Nat Commun 2018; 9:3489. [PMID: 30154480 PMCID: PMC6113206 DOI: 10.1038/s41467-018-06003-9] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Accepted: 08/06/2018] [Indexed: 12/11/2022] Open
Abstract
To fulfill its role in protein biogenesis, the endoplasmic reticulum (ER) depends on the Hsp70-type molecular chaperone BiP, which requires a constant ATP supply. However, the carrier that catalyzes ATP uptake into the ER was unknown. Here, we report that our screen of gene expression datasets for member(s) of the family of solute carriers that are co-expressed with BiP and are ER membrane proteins identifies SLC35B1 as a potential candidate. Heterologous expression of SLC35B1 in E. coli reveals that SLC35B1 is highly specific for ATP and ADP and acts in antiport mode. Moreover, depletion of SLC35B1 from HeLa cells reduces ER ATP levels and, as a consequence, BiP activity. Thus, human SLC35B1 may provide ATP to the ER and was named AXER (ATP/ADP exchanger in the ER membrane). Furthermore, we propose an ER to cytosol low energy response regulatory axis (termed lowER) that appears as central for maintaining ER ATP supply.
Collapse
|
7
|
Porcine Reproductive and Respiratory Syndrome Virus Infection Induces both eIF2α Phosphorylation-Dependent and -Independent Host Translation Shutoff. J Virol 2018; 92:JVI.00600-18. [PMID: 29899101 DOI: 10.1128/jvi.00600-18] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Accepted: 05/25/2018] [Indexed: 12/14/2022] Open
Abstract
Porcine reproductive and respiratory syndrome virus (PRRSV) is an Arterivirus that has caused tremendous economic losses in the global swine industry since it was discovered in the late 1980s. Inducing host translation shutoff is a strategy used by many viruses to optimize their replication and spread. Here, we demonstrate that PRRSV infection causes host translation suppression, which is strongly dependent on viral replication. By screening PRRSV-encoded nonstructural proteins (nsps), we found that nsp2 participates in the induction of host translation shutoff and that its transmembrane (TM) domain is required for this process. nsp2-induced translation suppression is independent of protein degradation pathways and the phosphorylation of eukaryotic initiation factor 2α (eIF2α). However, the overexpression of nsp2 or its TM domain significantly attenuated the mammalian target of rapamycin (mTOR) signaling pathway, an alternative pathway for modulating host gene expression. PRRSV infection also attenuated the mTOR signaling pathway, and PRRSV-induced host translation shutoff could be partly reversed when the attenuated mTOR phosphorylation was reactivated by an activator of the mTOR pathway. PRRSV infection still negatively regulated the host translation when the effects of eIF2α phosphorylation were completely reversed. Taken together, our results demonstrate that PRRSV infection induces host translation shutoff and that nsp2 is associated with this process. Both eIF2α phosphorylation and the attenuation of the mTOR signaling pathway contribute to PRRSV-induced host translation arrest.IMPORTANCE Viruses are obligate parasites, and the production of progeny viruses relies strictly on the host translation machinery. Therefore, the efficient modulation of host mRNA translation benefits viral replication, spread, and evolution. In this study, we provide evidence that porcine reproductive and respiratory syndrome virus (PRRSV) infection induces host translation shutoff and that the viral nonstructural protein nsp2 is associated with this process. Many viruses induce host translation shutoff by phosphorylating eukaryotic initiation factor 2α (eIF2α). However, PRRSV nsp2 does not induce eIF2α phosphorylation but attenuates the mTOR signaling pathway, another pathway regulating the host cell translational machinery. We also found that PRRSV-induced host translation shutoff was partly reversed by eliminating the effects of eIF2α phosphorylation or reactivating the mTOR pathway, indicating that PRRSV infection induces both eIF2α phosphorylation-dependent and -independent host translation shutoff.
Collapse
|
8
|
Ryoo HD, Vasudevan D. Two distinct nodes of translational inhibition in the Integrated Stress Response. BMB Rep 2018; 50:539-545. [PMID: 28803610 PMCID: PMC5720466 DOI: 10.5483/bmbrep.2017.50.11.157] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2017] [Indexed: 12/21/2022] Open
Abstract
The Integrated Stress Response (ISR) refers to a signaling pathway initiated by stress-activated eIF2α kinases. Once activated, the pathway causes attenuation of global mRNA translation while also paradoxically inducing stress response gene expression. A detailed analysis of this pathway has helped us better understand how stressed cells coordinate gene expression at translational and transcriptional levels. The translational attenuation associated with this pathway has been largely attributed to the phosphorylation of the translational initiation factor eIF2α. However, independent studies are now pointing to a second translational regulation step involving a downstream ISR target, 4E-BP, in the inhibition of eIF4E and specifically cap-dependent translation. The activation of 4E-BP is consistent with previous reports implicating the roles of 4E-BP resistant, Internal Ribosome Entry Site (IRES) dependent translation in ISR active cells. In this review, we provide an overview of the translation inhibition mechanisms engaged by the ISR and how they impact the translation of stress response genes.
Collapse
Affiliation(s)
- Hyung Don Ryoo
- Department of Cell Biology, New York University School of Medicine, New York, NY 10016, USA
| | - Deepika Vasudevan
- Department of Cell Biology, New York University School of Medicine, New York, NY 10016, USA
| |
Collapse
|
9
|
Starr CR, Pitale PM, Gorbatyuk M. Translational attenuation and retinal degeneration in mice with an active integrated stress response. Cell Death Dis 2018; 9:484. [PMID: 29706649 PMCID: PMC5924758 DOI: 10.1038/s41419-018-0513-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2017] [Revised: 03/19/2018] [Accepted: 03/22/2018] [Indexed: 12/12/2022]
Abstract
An integrated stress response (ISR), identified in several different animal models of inherited retinal degeneration (IRD), is activated following various cellular stresses. The ISR results in the phosphorylation of eIF2α (p-eIF2α) and a consequent halt in protein synthesis. Although generally protective, persistent elevations in p-eIF2α could lead to cell demise. Therefore, we aimed to determine whether ISR activation is associated with diminished translation rates in mice with IRD. Retinal protein extracts from rd16 mice at different time points were analyzed and the retinal levels of protein synthesis were assessed using the SUnSET method. We found that rd16 mice experience persistent ISR activation: p-eIF2α, ATF4, and CHOP were significantly upregulated at P15 and P20. In agreement with ISR activation, we found that rd16 mice experience translational attenuation at P15. Similar to rd16, other IRD models, T17M RHO, and rd10 also demonstrated a decline in protein synthesis, correlating with p-eIF2α elevation. We then assessed the role of PERK and eIF2α in translational attenuation in rd16 using a PERK inhibitor, GSK2606414. We found that while the treatment significantly reduced p-eIF2α, it did not cause a complete recovery in translation. This suggests that eIF2α is not the only or even the primary point of translational control in IRD, and a second node of translational regulation comprising AKT and mTOR should be evaluated. Surprisingly, we found that AKT-mTOR signaling was diminished in rd16 and rd10 retinas, suggesting a potential link between AKT-mTOR and translational inhibition. Therefore, for the first time, this study shows translation attenuation in IRD models, and highlights the potential roles of eIF2α kinases and AKT-mTOR signaling that could grant valuable insight into the potential treatments for IRD.
Collapse
Affiliation(s)
- Christopher R Starr
- Department of Optometry and Vision Science, School of Optometry, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Priyamvada M Pitale
- Department of Optometry and Vision Science, School of Optometry, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Marina Gorbatyuk
- Department of Optometry and Vision Science, School of Optometry, University of Alabama at Birmingham, Birmingham, AL, USA.
| |
Collapse
|
10
|
Regulated IRE1-dependent mRNA decay sets the threshold for dendritic cell survival. Nat Cell Biol 2017; 19:698-710. [PMID: 28459443 DOI: 10.1038/ncb3518] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Accepted: 03/21/2017] [Indexed: 12/23/2022]
Abstract
The IRE1-XBP1 signalling pathway is part of a cellular programme that protects against endoplasmic reticulum (ER) stress, but also controls development and survival of immune cells. Loss of XBP1 in splenic type 1 conventional dendritic cells (cDC1s) results in functional alterations without affecting cell survival. However, in mucosal cDC1s, loss of XBP1 impaired survival in a tissue-specific manner-while lung cDC1s die, intestinal cDC1s survive. This was not caused by differential activation of ER stress cell-death regulators CHOP or JNK. Rather, survival of intestinal cDC1s was associated with their ability to shut down protein synthesis through a protective integrated stress response and their marked increase in regulated IRE1-dependent messenger RNA decay. Furthermore, loss of IRE1 endonuclease on top of XBP1 led to cDC1 loss in the intestine. Thus, mucosal DCs differentially mount ATF4- and IRE1-dependent adaptive mechanisms to survive in the face of ER stress.
Collapse
|
11
|
Galluzzi L, Diotallevi A, De Santi M, Ceccarelli M, Vitale F, Brandi G, Magnani M. Leishmania infantum Induces Mild Unfolded Protein Response in Infected Macrophages. PLoS One 2016; 11:e0168339. [PMID: 27978534 PMCID: PMC5158320 DOI: 10.1371/journal.pone.0168339] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Accepted: 11/09/2016] [Indexed: 11/19/2022] Open
Abstract
The Leishmaniases are a group of parasitic diseases caused by protozoa of the Leishmania genus affecting both humans and other vertebrates. Leishmania is an intracellular pathogen able to confer resistance to apoptosis in the early phase of macrophages infection by activation of host PI3K/Akt pathway and inhibition of caspase-3 activation. Intracellular pathogens hijack organelles such as ER to facilitate survival and replication, thus eliciting ER stress and activating/modulating the unfolded protein response (UPR) in the host cell. The UPR is aimed to mitigate ER stress, thereby promoting cell survival. However, prolonged ER stress will activate the apoptotic pathway. The aim of this study was to investigate the ER stress response in Leishmania-infected macrophages to gain insights about the mechanisms underlying the apoptosis resistance in parasitized cells. Macrophages differentiated from human monocytic cell lines (U937 and THP-1) and murine primary macrophages were infected with Leishmania infantum MHOM/TN/80/IPT1 (WHO international reference strain). Several ER stress/autophagy expression markers, as well as cell survival/apoptosis markers (phospho-Akt and cleaved caspase-3) were evaluated by qPCR and/or by western blotting. As ER stress positive control, cells were treated with tunicamycin or dithiothreitol (DTT). The gene expression analyses showed a mild but significant induction of the ER stress/autophagy markers. The western blot analyses revealed that the Leishmania infection induced Akt phosphorylation and significantly inhibited the induction of caspase-3 cleavage, eIF2α phosphorylation and DDIT3/CHOP expression in tunicamycin and DTT treated cells. The mild but significant increase in ER stress expression markers and the delay/attenuation of the effects of ER stress inducers in infected cells support the hypothesis that L. infantum could promote survival of host cells by inducing a mild ER stress response. The host ER stress response could be not only a common pathogenic mechanism among Leishmania species but also a target for development of new drugs.
Collapse
Affiliation(s)
- Luca Galluzzi
- Department of Biomolecular Sciences, University of Urbino Carlo Bo, Urbino, Italy
- * E-mail:
| | - Aurora Diotallevi
- Department of Biomolecular Sciences, University of Urbino Carlo Bo, Urbino, Italy
| | - Mauro De Santi
- Department of Biomolecular Sciences, University of Urbino Carlo Bo, Urbino, Italy
| | - Marcello Ceccarelli
- Department of Biomolecular Sciences, University of Urbino Carlo Bo, Urbino, Italy
| | - Fabrizio Vitale
- Istituto Zooprofilattico Sperimentale of Sicily A Mirri, Palermo, Italy
| | - Giorgio Brandi
- Department of Biomolecular Sciences, University of Urbino Carlo Bo, Urbino, Italy
| | - Mauro Magnani
- Department of Biomolecular Sciences, University of Urbino Carlo Bo, Urbino, Italy
| |
Collapse
|
12
|
Kang MJ, Vasudevan D, Kang K, Kim K, Park JE, Zhang N, Zeng X, Neubert TA, Marr MT, Ryoo HD. 4E-BP is a target of the GCN2-ATF4 pathway during Drosophila development and aging. J Cell Biol 2016; 216:115-129. [PMID: 27979906 PMCID: PMC5223598 DOI: 10.1083/jcb.201511073] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2015] [Revised: 04/19/2016] [Accepted: 11/17/2016] [Indexed: 12/31/2022] Open
Abstract
Kang et al. show that the GCN2–ATF4 pathway induces 4E-BP transcription in response to amino acid deprivation and also during the development of certain Drosophila tissues. 4E-BP has selective effects on translation; therefore, this pathway helps to shift the mRNA expression profiles of cells. Reduced amino acid availability attenuates mRNA translation in cells and helps to extend lifespan in model organisms. The amino acid deprivation–activated kinase GCN2 mediates this response in part by phosphorylating eIF2α. In addition, the cap-dependent translational inhibitor 4E-BP is transcriptionally induced to extend lifespan in Drosophila melanogaster, but through an unclear mechanism. Here, we show that GCN2 and its downstream transcription factor, ATF4, mediate 4E-BP induction, and GCN2 is required for lifespan extension in response to dietary restriction of amino acids. The 4E-BP intron contains ATF4-binding sites that not only respond to stress but also show inherent ATF4 activity during normal development. Analysis of the newly synthesized proteome through metabolic labeling combined with click chemistry shows that certain stress-responsive proteins are resistant to inhibition by 4E-BP, and gcn2 mutant flies have reduced levels of stress-responsive protein synthesis. These results indicate that GCN2 and ATF4 are important regulators of 4E-BP transcription during normal development and aging.
Collapse
Affiliation(s)
- Min-Ji Kang
- Department of Cell Biology, New York University School of Medicine, New York, NY 10016 .,Department of Biomedical Science, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Korea
| | - Deepika Vasudevan
- Department of Cell Biology, New York University School of Medicine, New York, NY 10016
| | - Kwonyoon Kang
- Department of Biomedical Science, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Korea
| | - Kyunggon Kim
- Proteomics Core Laboratory, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Korea
| | - Jung-Eun Park
- Department of Biomedical Science, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Korea
| | - Nan Zhang
- Department of Cell Biology, New York University School of Medicine, New York, NY 10016
| | - Xiaomei Zeng
- Department of Cell Biology, New York University School of Medicine, New York, NY 10016
| | - Thomas A Neubert
- Department of Biochemistry and Molecular Pharmacology, Kimmel Center for Biology and Medicine of the Skirball Institute, New York University School of Medicine, New York, NY 10016
| | - Michael T Marr
- Department of Biology, Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02453
| | - Hyung Don Ryoo
- Department of Cell Biology, New York University School of Medicine, New York, NY 10016
| |
Collapse
|
13
|
Young SK, Shao Y, Bidwell JP, Wek RC. Nuclear Matrix Protein 4 Is a Novel Regulator of Ribosome Biogenesis and Controls the Unfolded Protein Response via Repression of Gadd34 Expression. J Biol Chem 2016; 291:13780-8. [PMID: 27129771 DOI: 10.1074/jbc.m116.729830] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2016] [Indexed: 12/24/2022] Open
Abstract
The unfolded protein response (UPR) maintains protein homeostasis by governing the processing capacity of the endoplasmic reticulum (ER) to manage ER client loads; however, key regulators within the UPR remain to be identified. Activation of the UPR sensor PERK (EIFAK3/PEK) results in the phosphorylation of the α subunit of eIF2 (eIF2α-P), which represses translation initiation and reduces influx of newly synthesized proteins into the overloaded ER. As part of this adaptive response, eIF2α-P also induces a feedback mechanism through enhanced transcriptional and translational expression of Gadd34 (Ppp1r15A),which targets type 1 protein phosphatase for dephosphorylation of eIF2α-P to restore protein synthesis. Here we describe a novel mechanism by which Gadd34 expression is regulated through the activity of the zinc finger transcription factor NMP4 (ZNF384, CIZ). NMP4 functions to suppress bone anabolism, and we suggest that this occurs due to decreased protein synthesis of factors involved in bone formation through NMP4-mediated dampening of Gadd34 and c-Myc expression. Loss of Nmp4 resulted in an increase in c-Myc and Gadd34 expression that facilitated enhanced ribosome biogenesis and global protein synthesis. Importantly, protein synthesis was sustained during pharmacological induction of the UPR through a mechanism suggested to involve GADD34-mediated dephosphorylation of eIF2α-P. Sustained protein synthesis sensitized cells to pharmacological induction of the UPR, and the observed decrease in cell viability was restored upon inhibition of GADD34 activity. We conclude that NMP4 is a key regulator of ribosome biogenesis and the UPR, which together play a central role in determining cell viability during endoplasmic reticulum stress.
Collapse
Affiliation(s)
- Sara K Young
- From the Department of Biochemistry and Molecular Biology
| | - Yu Shao
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, Indiana 46202-5126
| | | | - Ronald C Wek
- From the Department of Biochemistry and Molecular Biology,
| |
Collapse
|
14
|
Expression and vitamin D-mediated regulation of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in healthy skin and in diabetic foot ulcers. Arch Dermatol Res 2014; 306:809-21. [DOI: 10.1007/s00403-014-1494-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Revised: 06/12/2014] [Accepted: 08/20/2014] [Indexed: 01/13/2023]
|
15
|
Abstract
Fetal hemoglobin (HbF) induction can ameliorate the clinical severity of sickle cell disease and β-thalassemia. We previously reported that activation of the eukaryotic initiation factor 2α (eIF2α) stress pathway increased HbF through a posttranscriptional mechanism. In this study, we explored the underlying means by which salubrinal, an activator of eIF2α signaling, enhances HbF production in primary human erythroid cells. Initial experiments eliminated changes in globin messenger RNA (mRNA) stability or cellular location and reduction of adult hemoglobin as possible salubrinal mechanisms. We then determined that salubrinal selectively increased the number of actively translating ribosomes on γ-globin mRNA. This enhanced translation efficiency occurred in the recovery phase of the stress response as phosphorylation of eIF2α and global protein synthesis returned toward baseline. These findings highlight γ-globin mRNA translation as a novel mechanism for regulating HbF production and as a pharmacologic target for induction of HbF.
Collapse
|
16
|
Guan BJ, Krokowski D, Majumder M, Schmotzer CL, Kimball SR, Merrick WC, Koromilas AE, Hatzoglou M. Translational control during endoplasmic reticulum stress beyond phosphorylation of the translation initiation factor eIF2α. J Biol Chem 2014; 289:12593-611. [PMID: 24648524 DOI: 10.1074/jbc.m113.543215] [Citation(s) in RCA: 98] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The accumulation of unfolded/misfolded proteins in the endoplasmic reticulum (ER) causes stress to which an unfolded protein response is activated to render cell survival or apoptosis (chronic stress). Transcriptional and translational reprogramming is tightly regulated during the unfolded protein response to ensure specific gene expression. The master regulator of this response is the PERK/eIF2α/ATF4 signaling where eIF2α is phosphorylated (eIF2α-P) by the kinase PERK. This signal leads to global translational shutdown, but it also enables translation of the transcription factor ATF4 mRNA. We showed recently that ATF4 induces an anabolic program through the up-regulation of selected amino acid transporters and aminoacyl-tRNA synthetases. Paradoxically, this anabolic program led cells to apoptosis during chronic ER stress in a manner that involved recovery from stress-induced protein synthesis inhibition. By using eIF2α-P-deficient cells as an experimental system, we identified a communicating network of signaling pathways that contribute to the inhibition of protein synthesis during chronic ER stress. This eIF2α-P-independent network includes (i) inhibition of mammalian target of rapamycin kinase protein complex 1 (mTORC1)-targeted protein phosphorylation, (ii) inhibited translation of a selective group of 5'-terminal oligopyrimidine mRNAs (encoding proteins involved in the translation machinery and translationally controlled by mTORC1 signaling), and (iii) inhibited translation of non-5'-terminal oligopyrimidine ribosomal protein mRNAs and ribosomal RNA biogenesis. We propose that the PERK/eIF2α-P/ATF4 signaling acts as a brake in the decline of protein synthesis during chronic ER stress by positively regulating signaling downstream of the mTORC1 activity. These studies advance our knowledge on the complexity of the communicating signaling pathways in controlling protein synthesis rates during chronic stress.
Collapse
|