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Park YS, Kim HL, Lee SH, Zhang Y, Kim IB. Expression of the Endoplasmic Reticulum Stress Marker GRP78 in the Normal Retina and Retinal Degeneration Induced by Blue LED Stimuli in Mice. Cells 2021; 10:cells10050995. [PMID: 33922686 PMCID: PMC8145904 DOI: 10.3390/cells10050995] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 04/19/2021] [Accepted: 04/22/2021] [Indexed: 01/12/2023] Open
Abstract
Retinal degeneration is a leading cause of blindness. The unfolded protein response (UPR) is an endoplasmic reticulum (ER) stress response that affects cell survival and death and GRP78 forms a representative protective response. We aimed to determine the exact localization of GRP78 in an animal model of light-induced retinal degeneration. Dark-adapted mice were exposed to blue light-emitting diodes and retinas were obtained at 24 h and 72 h after exposure. In the normal retina, we found that GRP78 was rarely detected in the photoreceptor cells while it was expressed in the perinuclear space of the cell bodies in the inner nuclear and ganglion cell layers. After injury, the expression of GRP78 in the outer nuclear and inner plexiform layers increased in a time-dependent manner. However, an increased GRP78 expression was not observed in damaged photoreceptor cells in the outer nuclear layer. GRP78 was located in the perinuclear space and ER lumen of glial cells and the ER developed in glial cells during retinal degeneration. These findings suggest that GRP78 and the ER response are important for glial cell activation in the retina during photoreceptor degeneration.
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Affiliation(s)
- Yong Soo Park
- Department of Anatomy, College of Medicine, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul 06591, Korea; (Y.S.P.); (S.H.L.); (Y.Z.)
- Catholic Neuroscience Institute, College of Medicine, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul 06591, Korea
| | - Hong-Lim Kim
- Integrative Research Support Center, College of Medicine, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul 06591, Korea;
| | - Seung Hee Lee
- Department of Anatomy, College of Medicine, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul 06591, Korea; (Y.S.P.); (S.H.L.); (Y.Z.)
- Catholic Neuroscience Institute, College of Medicine, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul 06591, Korea
| | - Yan Zhang
- Department of Anatomy, College of Medicine, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul 06591, Korea; (Y.S.P.); (S.H.L.); (Y.Z.)
- Department of Biomedicine and Health Sciences, Graduate School, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul 06591, Korea
| | - In-Beom Kim
- Department of Anatomy, College of Medicine, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul 06591, Korea; (Y.S.P.); (S.H.L.); (Y.Z.)
- Catholic Neuroscience Institute, College of Medicine, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul 06591, Korea
- Integrative Research Support Center, College of Medicine, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul 06591, Korea;
- Department of Biomedicine and Health Sciences, Graduate School, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul 06591, Korea
- Catholic Institute for Applied Anatomy, College of Medicine, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul 06591, Korea
- Correspondence: ; Tel.: +82-2-2258-7263
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Park HR, Oh R, Wagner P, Panganiban R, Lu Q. New Insights Into Cellular Stress Responses to Environmental Metal Toxicants. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2016; 331:55-82. [PMID: 28325215 DOI: 10.1016/bs.ircmb.2016.10.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Exposures to metal toxicants in the environment disrupt normal physiological functions and have been linked to the development of a myriad of human diseases. While the molecular and cellular mechanisms underlying metal toxicities remain to be fully understood, it is well appreciated that metal toxicants induce cellular stresses and that how cells respond to the stresses plays an important role in metal toxicity. In this review, we focus on how metal exposures induce stresses in the endoplasmic reticulum (ER) to elicit the unfolded protein response (UPR). We document the emerging evidence that induction of ER stress and UPR in the development of human diseases is associated with metal exposures. We also discuss the role of the interplay between ER stress and oxidative stress in metal toxicity. Finally, we review recent advances in functional genomics approaches and discuss how applications of these new tools could help elucidate the molecular mechanisms underlying cellular stresses induced by environmental metal toxicants.
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Affiliation(s)
- H-R Park
- Program in Molecular and Integrative Physiological Sciences, Harvard T.H. Chan School of Public Health, Boston, MA, United States
| | - R Oh
- Program in Molecular and Integrative Physiological Sciences, Harvard T.H. Chan School of Public Health, Boston, MA, United States
| | - P Wagner
- Program in Molecular and Integrative Physiological Sciences, Harvard T.H. Chan School of Public Health, Boston, MA, United States
| | - R Panganiban
- Program in Molecular and Integrative Physiological Sciences, Harvard T.H. Chan School of Public Health, Boston, MA, United States
| | - Q Lu
- Program in Molecular and Integrative Physiological Sciences, Harvard T.H. Chan School of Public Health, Boston, MA, United States.
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Bauer J, Bussen M, Wise P, Wehland M, Schneider S, Grimm D. Searching the literature for proteins facilitates the identification of biological processes, if advanced methods of analysis are linked: a case study on microgravity-caused changes in cells. Expert Rev Proteomics 2016; 13:697-705. [DOI: 10.1080/14789450.2016.1197775] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Johann Bauer
- Informationsvermittlung, Max-Planck Institute for Biochemistry, Martinsried, Germany
| | - Markus Bussen
- Lifescience, Elsevier Information System GmbH, Frankfurt am Main, Germany
| | - Petra Wise
- Hematology/Oncology, Children’s Hospital Los Angeles, University of Southern California, Los Angeles, CA, USA
| | - Markus Wehland
- Clinic for Plastic, Aesthetic and Hand Surgery, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany
| | - Sabine Schneider
- Informationsvermittlung, Max-Planck Institute for Biochemistry, Martinsried, Germany
| | - Daniela Grimm
- Clinic for Plastic, Aesthetic and Hand Surgery, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany
- Institute of Biomedicine, Pharmacology, Aarhus University, Aarhus, Denmark
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The Chaperone Grp78 in Protein Folding Disorders of the Nervous System. Neurochem Res 2014; 40:329-35. [DOI: 10.1007/s11064-014-1405-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Revised: 07/25/2014] [Accepted: 07/29/2014] [Indexed: 01/09/2023]
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Liu Y, Yang L, Chen KL, Zhou B, Yan H, Zhou ZG, Li Y. Knockdown of GRP78 promotes apoptosis in pancreatic acinar cells and attenuates the severity of cerulein and LPS induced pancreatic inflammation. PLoS One 2014; 9:e92389. [PMID: 24643222 PMCID: PMC3958537 DOI: 10.1371/journal.pone.0092389] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 02/22/2014] [Indexed: 02/05/2023] Open
Abstract
Acute pancreatitis (AP) is a potentially lethal disease characterized by inflammation and parenchymal cell death; also, the severity of AP correlates directly with necrosis and inversely with apoptosis. However, mechanisms of regulating cell death in AP remain unclear. The endoplasmic reticulum (ER) chaperone protein GRP78 has anti-apoptotic properties, in addition to modulating ER stress responses. This study used RNA interference (RNAi) approach to investigate the potential role of GRP78 in regulating apoptosis during AP. In vitro models of AP were successfully developed by treating AR42J cells with cerulein or cerulein plus lipoplysaccharide (LPS). There was more pancreatic inflammation and less apoptosis with the cerulein plus LPS treatment. Furthermore, knockdown of GRP78 expression markedly promoted apoptosis and reduced necrosis in pancreatic acinar cells. This was accomplished by enhancing the activation of caspases and inhibiting the activity of X-linked inhibitor of apoptosis protein (XIAP), as well as a receptor interacting protein kinase-1(RIPK1), which is a key mediator of necrosis. This attenuated the severity of pancreatic inflammation, especially after cerulein plus LPS treatment. In conclusion, these findings indicate that GRP78 plays an anti-apoptotic role in regulating the cell death response during AP. Therefore, GRP78 is a potential therapeutic target for AP.
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Affiliation(s)
- Yong Liu
- Department of Gastroenterological Surgery, West China Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Lie Yang
- Department of Gastroenterological Surgery, West China Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Ke-Ling Chen
- Institute of Digestive Surgery and State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Bin Zhou
- Institute of Digestive Surgery and State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Hui Yan
- Department of Gastroenterological Surgery, West China Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Zong-Guang Zhou
- Department of Gastroenterological Surgery, West China Hospital, Sichuan University, Chengdu, Sichuan, China
- Institute of Digestive Surgery and State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, Sichuan, China
| | - Yuan Li
- Institute of Digestive Surgery and State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, Sichuan, China
- * E-mail:
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HSPA5 forms specific complexes with copper. Neurochem Res 2012; 38:321-9. [PMID: 23161089 DOI: 10.1007/s11064-012-0923-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Revised: 11/01/2012] [Accepted: 11/08/2012] [Indexed: 01/19/2023]
Abstract
Our previous study indicated that Hspa5 directly interacts with copper (Cu) to maintain Cu homeostasis in astrocytes. In this study, we explored the possibility that Cu forms a specific complex with Hspa5 by assaying stoichiometric binding of Cu and other metals to recombinant human HSPA5 (rh-HSPA5) in silico. Spectrophotometric analysis showed that incubation of rh-HSPA5 with Cu but not with Fe, Mn, Zn, or Pb in the presence of ascorbic acid produced an absorbance peak at 470 nm. Furthermore, the absorbance peak was absent when bovine serum albumin was incubated with Cu and when another recombinant protein YWHAZ-14-3-3-Zeta carrying a 6× histidine tag identical to the tag in the rh-HSPA5 was incubated with Cu. The absorbance peak produced by Cu and rh-HSPA5 was abolished by EDTA treatment and was stabilized at pH levels above 6.5. Assay of the stoichiometry of metal binding to the purified rh-HSPA5 showed that one molecule of the rh-HSPA5 could chelate 1 or 2 Cu, 13 iron (Fe), 5 zinc (Zn) and 10 lead (Pb) ions but not manganese (Mn). These data further support our previous finding that HSPA5 specifically forms a complex with Cu to help maintain Cu homeostasis.
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Wey S, Luo B, Lee AS. Acute inducible ablation of GRP78 reveals its role in hematopoietic stem cell survival, lymphogenesis and regulation of stress signaling. PLoS One 2012; 7:e39047. [PMID: 22723926 PMCID: PMC3377598 DOI: 10.1371/journal.pone.0039047] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2012] [Accepted: 05/17/2012] [Indexed: 11/19/2022] Open
Abstract
GRP78, a master regulator of the unfolded protein response (UPR) and cell signaling, is required for inner cell mass survival during early embryonic development. However, little is known about its role in adult hematopoietic stem cells (HSCs) and hematopoiesis. Here we generated a conditional knockout mouse model that acutely deletes Grp78 in the adult hematopoietic system. Acute GRP78 ablation resulted in a significant reduction of HSCs, common lymphoid and myeloid progenitors, and lymphoid cell populations in the mutant mice. The GRP78-null induced reduction of the HSC pool could be attributed to increased apoptosis. Chimeric mice with Grp78 deletion only in the hematopoietic cells also showed a loss of HSCs and lymphopenia, suggesting a cell intrinsic effect. Analysis of GRP78 deficient bone marrow (BM) cells showed constitutive activation of all the major UPR signaling pathways, including activation of eIF2α, ATF6, xbp-1 splicing, as well as caspase activation. A multiplex cytokine assay further revealed alteration in select cytokine and chemokine serum levels in the mutant mice. Collectively, these studies demonstrate that GRP78 plays a pleiotropic role in BM cells and contributes to HSC survival and the maintenance of the lymphoid lineage.
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Affiliation(s)
- Shiuan Wey
- Department of Biochemistry and Molecular Biology, University of Southern California Keck School of Medicine, University of Southern California Norris Comprehensive Cancer Center, Los Angeles, California, United States of America
| | - Biquan Luo
- Department of Biochemistry and Molecular Biology, University of Southern California Keck School of Medicine, University of Southern California Norris Comprehensive Cancer Center, Los Angeles, California, United States of America
| | - Amy S. Lee
- Department of Biochemistry and Molecular Biology, University of Southern California Keck School of Medicine, University of Southern California Norris Comprehensive Cancer Center, Los Angeles, California, United States of America
- * E-mail:
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Tiffany-Castiglioni E, Qian Y. ER chaperone–metal interactions: Links to protein folding disorders. Neurotoxicology 2012; 33:545-57. [DOI: 10.1016/j.neuro.2012.02.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2011] [Revised: 02/07/2012] [Accepted: 02/07/2012] [Indexed: 01/09/2023]
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Qian Y, Zheng Y, Taylor R, Tiffany-Castiglioni E. Involvement of the molecular chaperone Hspa5 in copper homeostasis in astrocytes. Brain Res 2012; 1447:9-19. [PMID: 22342161 DOI: 10.1016/j.brainres.2012.01.065] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2011] [Revised: 01/17/2012] [Accepted: 01/27/2012] [Indexed: 12/24/2022]
Abstract
Copper (Cu) ion availability in tissues and cells must be closely regulated within safe limits by Cu transporters and chaperones. Astrocytes play key roles in metal homeostasis and distribution in the brain that are only partially understood. The purpose of this study was to define the role that the protein chaperone Hspa5, also known as Grp78, plays in Cu homeostasis in astrocytes. First passage cultures of primary astrocytes from neonatal rats and cultures of the C6 rat glioma cells were used as models. We found that the level of Cu accumulation in astrocyte cultures increased with Cu concentrations in the medium, and Cu treatment significantly reduced cellular levels of iron (Fe), manganese (Mn) and zinc (Zn). Cu accumulation specifically induced protein expression of Hspa5 but not metallothioneins (MTs) in astrocytes. In C6 cells, Hspa5 was identified as one component of a Cu-binding complex and shown to directly bind Cu. However, the level of Hspa5 expression was not proportional to Cu accumulation in astrocytes and C6 cells: astrocytes expressed low protein levels of Hspa5 compared to C6 cells but accumulated significantly more Cu than did C6 cells. Consistent with this finding, astrocytes expressed a lower level of the Cu-extruding protein Atp7a than did C6 cells, and depletion of Hspa5 by RNA interference resulted in significantly increased Cu accumulation and induction of MT1/2 expression. These data demonstrate that Hspa5 is involved in Cu homeostasis in astrocytes but not as a Cu storage protein.
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Affiliation(s)
- Yongchang Qian
- Department of Integrative Biosciences, Texas A&M University, College Station, TX 77843, USA.
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Oh-Hashi K, Tanaka K, Koga H, Hirata Y, Kiuchi K. Intracellular trafficking and secretion of mouse mesencephalic astrocyte-derived neurotrophic factor. Mol Cell Biochem 2011; 363:35-41. [PMID: 22120531 DOI: 10.1007/s11010-011-1155-0] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2011] [Accepted: 11/11/2011] [Indexed: 01/23/2023]
Abstract
Recently, mesencephalic astrocyte-derived neurotrophic factor (MANF) has been reported to prevent cell death under some pathophysiological conditions. MANF, also referred to as arginine rich, mutated in early stage of tumors (Armet), was identified as an endoplasmic reticulum (ER) stress-inducible factor. Using RT-PCR, we found two variants of MANF mRNA: wild type, which contains exon 1 (wt-MANF), and one lacking exon 1, which is presumably not secreted (ΔΝ-MANF) in Neuro2a cells. The latter has a putative translational start site upstream of the second exon in the mouse MANF gene. Comparing the expression of wt-MANF with that of ΔΝ-MANF, we found that the amount of intracellular ΔΝ-MANF was much lower than that of wt-MANF. Furthermore, ΔΝ-MANF was not detected in the culture medium after its transient transfection into Neuro2a cells. Deletion of several α-helices of mouse MANF decreased its intracellular stability and secretion. Secretion of wt-MANF was almost completely inhibited by either treatment with brefeldin A (BFA), which disrupts the Golgi apparatus structure, or overexpression of a dominant negative Sar1 (Sar1[H79G]), which is reported to impair COPII-mediated transport from the ER to the Golgi apparatus. In addition, the enforced expression of glucose-regulated protein 78 kDa (GRP78) attenuated the secretion of wt-MANF and led to its intracellular accumulation. MANF lacking the four C-terminal amino acids (ΔC-MANF) accumulated at low levels in the cells, but its intracellular level was increased by GRP78 overexpression. The amount of ΔC-MANF in the culture medium was partially down-regulated after co-transfection of GRP78. Substitution of the amino acids RTDL at the C-terminus of mouse MANF with KDEL, the canonical ER localization signal in GRP78, markedly decreased MANF secretion and its secretion was further attenuated by GRP78 overexpression. Taken together, our data show that the secretion of MANF is regulated via COPII-mediated transport and that its C-terminus could be responsible for its retention in the ER through GRP78. The alternate isotype, ΔΝ-MANF, may be less stable in cells than wt-MANF and may not be secreted extracellularly.
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Affiliation(s)
- Kentaro Oh-Hashi
- Department of Biomolecular Science, Faculty of Engineering, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan.
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Determination of metal interactions with the chaperone Hspa5 in human astrocytoma cells and rat astrocyte primary cultures. Methods Mol Biol 2011. [PMID: 21815057 DOI: 10.1007/978-1-61779-170-3_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Molecular chaperones assist the folding of nascent proteins during translation into their correct conformations. Neurotoxic metals such as copper (Cu) and lead (Pb) may produce a deficiency in chaperone function that compromises protein secretion and exacerbates protein aggregation, potentially promoting neurodegenerative diseases that exhibit protein aggregation. Because astrocytes function as depots in the brain for certain metals, including Cu and Pb, the interaction of metals with chaperones in these cells is of interest. Furthermore, Pb and Cu bind strongly to the molecular chaperone heat shock 70 kDa protein Hspa5, also known as glucose-regulated protein 78 (Grp78) or immunoglobulin-binding protein (BiP). This chapter describes methods for expressing fluorescent chimeric proteins in astrocytes and astrocytoma cells in order to examine the metal-induced cytosolic redistribution of Hspa5, as well as associated effects on the secretion of interleukin-6 (IL-6).
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Oh-hashi K, Kunieda R, Hirata Y, Kiuchi K. Biosynthesis and secretion of mouse cysteine-rich with EGF-like domains 2. FEBS Lett 2011; 585:2481-7. [PMID: 21729698 DOI: 10.1016/j.febslet.2011.06.029] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2011] [Revised: 06/02/2011] [Accepted: 06/23/2011] [Indexed: 01/26/2023]
Abstract
In this study, we found that Cysteine-rich with EGF-like domains 2 (CRELD2), a novel endoplasmic reticulum stress-inducible protein, is not only localized in the ER-Golgi apparatus but also spontaneously secreted. Deletion of four C-terminal amino acids from mouse CRELD2 or addition of tag-peptides to its C-terminus dramatically enhanced CRELD2 secretion. Intra- and extra-cellular CRELD2 is differentially glycosylated and its spontaneous secretion was significantly prevented by overexpression of a dominant negative mutant Sar1 and treatment with brefeldin A. Overexpression of wild-type GRP78 remarkably enhanced the secretion of wild-type but not mutant CRELD2. Our results demonstrate both that CRELD2 is a novel secretory glycoprotein regulated by Sar1 and GRP78 and that the C-terminal of CRELD2 plays a crucial role in its secretion.
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Affiliation(s)
- Kentaro Oh-hashi
- Department of Biomolecular Science, Faculty of Engineering, Gifu University, Gifu, Japan.
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Shinkai Y, Yamamoto C, Kaji T. Lead induces the expression of endoplasmic reticulum chaperones GRP78 and GRP94 in vascular endothelial cells via the JNK-AP-1 pathway. Toxicol Sci 2010; 114:378-86. [PMID: 20071421 DOI: 10.1093/toxsci/kfq008] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Lead, a ubiquitous heavy metal, is an important industrial and environmental pollutant that can target the vascular endothelium. To clarify the effects of lead on the unfolded protein response (UPR) and their significance in cytotoxicity, we examined the expression and function of endoplasmic reticulum (ER) chaperones glucose-regulated protein 78 (GRP78) and glucose-regulated protein 94 (GRP94) in vascular endothelial cells. We used bovine aortic endothelial cells as an in vitro model of the vascular endothelium. Exposure of vascular endothelial cells to lead nitrate resulted in a marked induction of GRP78 and GRP94 messenger RNA levels. In response to lead, the expression of GRP78 and GRP94 proteins also significantly increased in a dose- and time-dependent manner. In addition, small interfering RNA (siRNA)-mediated knockdown of GRP78 significantly enhanced lead-induced cytotoxicity. Compared with other metal(loid)s, including cadmium chloride, zinc sulfate, copper sulfate, and sodium arsenite, lead nitrate was found to be the most potent metal to induce these chaperones in endothelial cells. In the examined UPR pathways, lead increased the phosphorylation of inositol-requiring enzyme 1 (IRE1) and c-jun N-terminal kinase (JNK). Interestingly, the lead-induced upregulation of GRP78 and GRP94 was almost completely blocked by the JNK inhibitor SP600125 or activator protein-1 (AP-1) inhibitor curcumin. Taken together, these results suggest that lead induces ER stress, but the induction of GRP78 and GRP94 expression via the JNK-AP-1 pathway functions as a defense mechanism against lead-induced cytotoxicity in vascular endothelial cells.
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Affiliation(s)
- Yasuhiro Shinkai
- Organization for Frontier Research in Preventive Pharmaceutical Sciences, Hokuriku University, Kanazawa, Ishikawa 920-1181, Japan
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Ben J, Gao S, Zhu X, Zheng Y, Zhuang Y, Bai H, Xu Y, Ji Y, Sha J, He Z, Chen Q. Glucose-regulated protein 78 inhibits scavenger receptor A-mediated internalization of acetylated low density lipoprotein. J Mol Cell Cardiol 2009; 47:646-55. [PMID: 19699207 DOI: 10.1016/j.yjmcc.2009.08.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2009] [Revised: 07/24/2009] [Accepted: 08/11/2009] [Indexed: 11/29/2022]
Abstract
Class A scavenger receptor (SR-A) plays an important role in foam cell formation. However, the mechanism underlying the internalization of the receptor-ligand complexes remains unclear. The aim of the present study was to investigate the molecular mechanism to regulate SR-A-mediated intracellular lipid accumulation in macrophages. A pull-down assay was performed and glucose-regulated protein 78 (GRP78) was identified to bind with the cytoplasmic domain of SR-A (CSR-A). Immunoprecipitation and artificially expressed protein binding assay demonstrated the direct specific binding of GRP78 with SR-A in cells. Indirect immunofluorescence assay and western blot analysis showed their co-localization in membrane and cytoplasm. Over-expression of GRP78 specifically inhibited SR-A-mediated uptake of fluorescent acetylated low-density lipoprotein, a specific ligand for SR-A, without altering cellular SR-A expression and binding ability, and significantly inhibited cholesterol ester accumulation in cells, which can be partly attributed to the suppression of c-Jun-NH2-terminal kinase signaling pathway. These results suggest that GRP78 may act as an inhibitor of SR-A-mediated internalization of modified low-density lipoprotein into macrophages.
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Affiliation(s)
- Jingjing Ben
- Institute of Reproductive Medicine, Nanjing Medical University, Nanjing, PR China
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