1
|
de la Riva-Carrasco R, Perez-Pandolfo S, Suárez Freire S, Romero NM, Bhujabal Z, Johansen T, Wappner P, Melani M. The immunophilin Zonda controls regulated exocytosis in endocrine and exocrine tissues. Traffic 2021; 22:111-122. [PMID: 33336828 DOI: 10.1111/tra.12777] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2020] [Revised: 12/15/2020] [Accepted: 12/15/2020] [Indexed: 11/30/2022]
Abstract
Exocytosis is a fundamental process in physiology, that ensures communication between cells, organs and even organisms. Hormones, neuropeptides and antibodies, among other cargoes are packed in exocytic vesicles that need to reach and fuse with the plasma membrane to release their content to the extracellular milieu. Hundreds of proteins participate in this process and several others in its regulation. We report here a novel component of the exocytic machinery, the Drosophila transmembrane immunophilin Zonda (Zda), previously found to participate in autophagy. Zda is highly expressed in secretory tissues, and regulates exocytosis in at least three of them: the ring gland, insulin-producing cells and the salivary gland. Using the salivary gland as a model system, we found that Zda is required at final steps of the exocytic process for fusion of secretory granules to the plasma membrane. In a genetic screen we identified the small GTPase RalA as a crucial regulator of secretory granule exocytosis that is required, similarly to Zda, for fusion between the secretory granule and the plasma membrane.
Collapse
Affiliation(s)
| | - Sebastián Perez-Pandolfo
- Laboratorio de Genética y Fisiología Molecular, Fundación Instituto Leloir, Buenos Aires, Argentina
| | - Sofía Suárez Freire
- Laboratorio de Genética y Fisiología Molecular, Fundación Instituto Leloir, Buenos Aires, Argentina
| | - Nuria M Romero
- Université Côte d'Azur, INRA, CNRS, Institut Sophia Agrobiotech, Sophia Antipolis, France
| | - Zambarlal Bhujabal
- Molecular Cancer Research Group, Department of Medical Biology, University of Tromsø-The Arctic University of Norway, Tromsø, Norway
| | - Terje Johansen
- Molecular Cancer Research Group, Department of Medical Biology, University of Tromsø-The Arctic University of Norway, Tromsø, Norway
| | - Pablo Wappner
- Laboratorio de Genética y Fisiología Molecular, Fundación Instituto Leloir, Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.,Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales-Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Mariana Melani
- Laboratorio de Genética y Fisiología Molecular, Fundación Instituto Leloir, Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| |
Collapse
|
2
|
Xie Y, Liu J, Kang R, Tang D. Mitophagy Receptors in Tumor Biology. Front Cell Dev Biol 2020; 8:594203. [PMID: 33262988 PMCID: PMC7686508 DOI: 10.3389/fcell.2020.594203] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Accepted: 10/21/2020] [Indexed: 12/13/2022] Open
Abstract
Mitochondria are multifunctional organelles that regulate cancer biology by synthesizing macromolecules, producing energy, and regulating cell death. The understanding of mitochondrial morphology, function, biogenesis, fission and fusion kinetics, and degradation is important for the development of new anticancer strategies. Mitophagy is a type of selective autophagy that can degrade damaged mitochondria under various environmental stresses, especially oxidative damage and hypoxia. The key regulator of mitophagy is the autophagy receptor, which recognizes damaged mitochondria and allows them to enter autophagosomes by binding to MAP1LC3 or GABARAP, and then undergo lysosomal-dependent degradation. Many components of mitochondria, including mitochondrial membrane proteins (e.g., PINK1, BNIP3L, BNIP3, FUNDC1, NIPSNAP1, NIPSNAP2, BCL2L13, PHB2, and FKBP8) and lipids (e.g., cardiolipin and ceramides), act as mitophagy receptors in a context-dependent manner. Dysfunctional mitophagy not only inhibits, but also promotes, tumorigenesis. Similarly, mitophagy plays a dual role in chemotherapy, radiotherapy, and immunotherapy. In this review, we summarize the latest advances in the mechanisms of mitophagy and highlight the pathological role of mitophagy receptors in tumorigenesis and treatment.
Collapse
Affiliation(s)
- Yangchun Xie
- Department of Oncology, The Second Xiangya Hospital, Central South University, Changsha, China
| | - Jiao Liu
- The Third Affiliated Hospital, Guangzhou Medical University, Guangzhou, China
| | - Rui Kang
- Department of Surgery, University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Daolin Tang
- Department of Surgery, University of Texas Southwestern Medical Center, Dallas, TX, United States
| |
Collapse
|
3
|
Zhuang Y, Ly RC, Frazier CV, Yu J, Qin S, Fan XY, Goetz MP, Boughey JC, Weinshilboum R, Wang L. The novel function of tumor protein D54 in regulating pyruvate dehydrogenase and metformin cytotoxicity in breast cancer. Cancer Metab 2019; 7:1. [PMID: 30697423 PMCID: PMC6345044 DOI: 10.1186/s40170-018-0193-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Accepted: 11/30/2018] [Indexed: 02/08/2023] Open
Abstract
Background The role of tumor protein D54 in breast cancer has not been studied and its function in breast cancer remains unclear. In our previous pharmacogenomic studies using lymphoblastoid cell line (LCL), this protein has been identified to affect metformin response. Although metformin has been widely studied as a prophylactic and chemotherapeutic drug, there is still a lack of biomarkers predicting the response to metformin in breast cancer. In this study, we revealed the novel function of TPD54 in breast cancer through understanding how TPD54 altered the cancer cell sensitivity to metformin. Methods The role of TPD54 in altering cellular sensitivity to metformin treatment was carried out by either knockdown or overexpression of TPD54, followed by measuring cell viability and reactive oxygen species (ROS) production in MCF7 breast cancer cell line and breast cancer patient-derived xenografts. Functional analysis of TPD54 in breast cancer cells was demonstrated by studying TPD54 protein localization and identification of potential binding partners of TPD54 through immunoprecipitation followed by mass spectrometry. The effect of TPD54 on pyruvate dehydrogenase (PDH) protein regulation was demonstrated by western blot, immunoprecipitation, and site-directed mutagenesis. Results TPD54 inhibited colony formation and enhanced cellular sensitivity to metformin treatment in MCF7 cells and breast cancer patient-derived xenografts. Mechanistic study indicated that TPD54 had mitochondrial localization, bound to and stabilized pyruvate dehydrogenase E1α by blocking pyruvate dehydrogenase kinase 1 (PDK1)-mediated serine 232 phosphorylation. TPD54 knockdown increased PDH E1α protein degradation and led to decreased PDH enzyme activity, which reduced mitochondrial oxygen consumption and reactive oxygen species (ROS) production, thus contributing to the resistance of breast cancer cells to metformin treatment. Conclusion We have discovered a novel mechanism by which TPD54 regulates pyruvate dehydrogenase and affects the sensitivity of breast cancer to metformin treatment. Our findings highlight the important post-translational regulation of PDK1 on PDH E1α and the potential application of TPD54 as a biomarker for selecting tumors that may be sensitive to metformin therapy. These provide new insights into understanding the regulation of PDH complexes and the resistance mechanisms of cancer cells to metformin treatment. Electronic supplementary material The online version of this article (10.1186/s40170-018-0193-4) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Yongxian Zhuang
- 1Division of Clinical Pharmacology, Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, 200 First Street SW, Rochester, MN 55905 USA
| | - Reynold C Ly
- 2Division of Clinical Pharmacology, Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic Graduate School of the Biomedical Sciences, Rochester, MN 55905 USA
| | | | - Jia Yu
- 1Division of Clinical Pharmacology, Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, 200 First Street SW, Rochester, MN 55905 USA
| | - Sisi Qin
- 1Division of Clinical Pharmacology, Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, 200 First Street SW, Rochester, MN 55905 USA
| | - Xiao-Yang Fan
- 1Division of Clinical Pharmacology, Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, 200 First Street SW, Rochester, MN 55905 USA
| | - Matthew P Goetz
- 1Division of Clinical Pharmacology, Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, 200 First Street SW, Rochester, MN 55905 USA.,4Department of Oncology, Mayo Clinic, Rochester, MN 55905 USA
| | - Judy C Boughey
- 5Department of Surgery, Mayo Clinic, Rochester, MN 55905 USA
| | - Richard Weinshilboum
- 1Division of Clinical Pharmacology, Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, 200 First Street SW, Rochester, MN 55905 USA
| | - Liewei Wang
- 1Division of Clinical Pharmacology, Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, 200 First Street SW, Rochester, MN 55905 USA
| |
Collapse
|
4
|
Yu B, Egbejimi A, Dharmat R, Xu P, Zhao Z, Long B, Miao H, Chen R, Wensel TG, Cai J, Chen Y. Phagocytosed photoreceptor outer segments activate mTORC1 in the retinal pigment epithelium. Sci Signal 2018; 11:11/532/eaag3315. [PMID: 29844054 DOI: 10.1126/scisignal.aag3315] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The retinal pigment epithelium (RPE) transports nutrients and metabolites between the microvascular bed that maintains the outer retina and photoreceptor neurons. The RPE removes photoreceptor outer segments (POS) by receptor-mediated phagocytosis, a process that peaks in the morning. Uptake and degradation of POS initiates signaling cascades in the RPE. Upstream stimuli from various metabolic activities converge on mechanistic target of rapamycin complex 1 (mTORC1), and aberrant mTORC1 signaling is implicated in aging and age-related degeneration of the RPE. We measured mTORC1-mediated responses to RPE phagocytosis in vivo and in vitro. During the morning burst of POS shedding, there was transient activation of mTORC1-mediated signaling in the RPE. POS activated mTORC1 through lysosome-independent mechanisms, and engulfed POS served as a docking platform for mTORC1 assembly. The identification of POS as endogenous stimuli of mTORC1 in the RPE provides a mechanistic link underlying the photoreceptor-RPE interaction in the outer retina.
Collapse
Affiliation(s)
- Bo Yu
- Department of Ophthalmology and Visual Science, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Anuoluwapo Egbejimi
- Department of Ophthalmology and Visual Science, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Rachayata Dharmat
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Pei Xu
- Department of Ophthalmology and Visual Science, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Zhenyang Zhao
- Department of Ophthalmology and Visual Science, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Bo Long
- Department of Ophthalmology and Visual Science, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Hongyu Miao
- Department of Biostatistics and Data Science, School of Public Health, University of Texas Health Science Center, Houston, TX 77030, USA
| | - Rui Chen
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA.,Department of Biochemistry, Baylor College of Medicine, Houston, TX 77030, USA
| | - Theodore G Wensel
- Department of Biochemistry, Baylor College of Medicine, Houston, TX 77030, USA
| | - Jiyang Cai
- Department of Ophthalmology and Visual Science, University of Texas Medical Branch, Galveston, TX 77555, USA.,Department of Neuroscience, Cell Biology and Anatomy, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Yan Chen
- Department of Ophthalmology and Visual Science, University of Texas Medical Branch, Galveston, TX 77555, USA. .,Department of Neuroscience, Cell Biology and Anatomy, University of Texas Medical Branch, Galveston, TX 77555, USA
| |
Collapse
|
5
|
Yu B, Xu P, Zhao Z, Cai J, Sternberg P, Chen Y. Subcellular distribution and activity of mechanistic target of rapamycin in aged retinal pigment epithelium. Invest Ophthalmol Vis Sci 2014; 55:8638-50. [PMID: 25491300 DOI: 10.1167/iovs.14-14758] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Inhibiting mechanistic target of rapamycin (mTOR) by pharmacological or genetic approaches can extend lifespan in mammals. The kinase activity of mTOR is controlled by upstream regulatory proteins and its subcellular localization. The purpose of this study was to characterize age-related alterations and functional consequences of mTOR signaling in the postmitotic RPE cells. METHODS Activity of mTOR complex 1 (mTORC1) was monitored by measuring phosphorylation status of its downstream effector protein S6, in either cultured human RPE cells or RPE explants prepared from mice at different ages. Subcellular distribution of mTOR was investigated by immunofluorescent staining of RPE culture or flatmount. The signaling of mTORC1 was modulated by either overexpression of a small guanosine triphosphatase, Ras homolog enriched in brain (Rheb), or disruption of the Ragulator complex with small interference RNA targeting p18. The effects of mTOR pathway on degradation of phagocytosed photoreceptor outer segments (POS) were determined by measuring the turnover rate of rhodopsin. RESULTS Aged RPE cells had more lysosome-associated mTOR and had increased response to amino acid stimulation. The lysosome distribution was essential for mTORC1 function, as disruption of the Ragulator complex abolished mTORC1 activation by amino acids. Increased mTORC1 activity caused decreased rate of degradation of internalized POS in the RPE. CONCLUSIONS Aging changes the subcellular localization and function of mTOR in the RPE. Increased mTORC1 inhibits POS degradation and may further exacerbate lysosome dysfunction of aged RPE.
Collapse
Affiliation(s)
- Bo Yu
- Department of Ophthalmology and Visual Sciences, University of Texas Medical Branch, Galveston, Texas, United States
| | - Pei Xu
- Department of Ophthalmology and Visual Sciences, University of Texas Medical Branch, Galveston, Texas, United States
| | - Zhenyang Zhao
- Department of Ophthalmology and Visual Sciences, University of Texas Medical Branch, Galveston, Texas, United States
| | - Jiyang Cai
- Department of Ophthalmology and Visual Sciences, University of Texas Medical Branch, Galveston, Texas, United States
| | - Paul Sternberg
- Vanderbilt Eye Institute, Vanderbilt University, Nashville, Tennessee, United States
| | - Yan Chen
- Department of Ophthalmology and Visual Sciences, University of Texas Medical Branch, Galveston, Texas, United States
| |
Collapse
|
6
|
Zheng X, Hao XY, Chen YH, Zhang X, Yang JF, Wang ZG, Liu DJ. Molecular Characterization and Tissue-specific Expression of a Novel FKBP38 Gene in the Cashmere Goat (Capra hircus). ASIAN-AUSTRALASIAN JOURNAL OF ANIMAL SCIENCES 2014; 25:758-63. [PMID: 25049623 PMCID: PMC4093086 DOI: 10.5713/ajas.2011.11398] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Revised: 01/24/2012] [Accepted: 12/29/2011] [Indexed: 12/01/2022]
Abstract
As a member of a subclass of immunophilins, it is controversial that FKBP38 acts an upstream regulator of mTOR signaling pathway, which control the process of cell-growth, proliferation and differentiation. In order to explore the relationship between FKBP38 and mTOR in the Cashmere goat (Capra hircus) cells, a full-length cDNA was cloned (GenBank accession number JF714970) and expression pattern was analyzed. The cloned FKBP38 gene is 1,248 bp in length, containing an open reading frame (ORF) from nucleotide 13 to 1,248 which encodes 411 amino acids, and 12 nucleotides in front of the initiation codon. The full cDNA sequence shares 98% identity with cattle, 94% with horse and 90% with human. The putative amino acid sequence shows the higher homology which is 98%, 97% and 94%, correspondingly. The bioinformatics analysis showed that FKBP38 contained a FKBP_C domain, two TPR domains and a TM domain. Psite analysis suggested that the ORF encoding protein contained a leucine-zipper pattern and a Prenyl group binding site (CAAX box). Tissue-specific expression analysis was performed by semi-quantitative RT-PCR and showed that the FKBP38 expression was detected in all the tested tissues and the highest level of mRNA accumulation was detected in testis, suggesting that FKBP38 plays an important role in goat cells.
Collapse
Affiliation(s)
- X Zheng
- College of Life Science, Inner Mongolia University, The Key Laboratory of Mammal Reproductive Biology and Biotechnology, Ministry of Education, Hohhot 010021, China
| | - X Y Hao
- College of Life Science, Inner Mongolia University, The Key Laboratory of Mammal Reproductive Biology and Biotechnology, Ministry of Education, Hohhot 010021, China ; TEDA School of Biological Sciences and Biotechnology, Nankai University, 23HongDa Street, Tianjin 300457, China
| | - Y H Chen
- College of Life Science, Inner Mongolia University, The Key Laboratory of Mammal Reproductive Biology and Biotechnology, Ministry of Education, Hohhot 010021, China
| | - X Zhang
- College of Life Science, Inner Mongolia University, The Key Laboratory of Mammal Reproductive Biology and Biotechnology, Ministry of Education, Hohhot 010021, China
| | - J F Yang
- College of Life Science, Inner Mongolia University, The Key Laboratory of Mammal Reproductive Biology and Biotechnology, Ministry of Education, Hohhot 010021, China
| | - Z G Wang
- College of Life Science, Inner Mongolia University, The Key Laboratory of Mammal Reproductive Biology and Biotechnology, Ministry of Education, Hohhot 010021, China
| | - D J Liu
- College of Life Science, Inner Mongolia University, The Key Laboratory of Mammal Reproductive Biology and Biotechnology, Ministry of Education, Hohhot 010021, China
| |
Collapse
|
7
|
Azuaje FJ, Wang H, Zheng H, Léonard F, Rolland-Turner M, Zhang L, Devaux Y, Wagner DR. Predictive integration of gene functional similarity and co-expression defines treatment response of endothelial progenitor cells. BMC SYSTEMS BIOLOGY 2011; 5:46. [PMID: 21447198 PMCID: PMC3080295 DOI: 10.1186/1752-0509-5-46] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/17/2010] [Accepted: 03/30/2011] [Indexed: 01/04/2023]
Abstract
Background Endothelial progenitor cells (EPCs) have been implicated in different processes crucial to vasculature repair, which may offer the basis for new therapeutic strategies in cardiovascular disease. Despite advances facilitated by functional genomics, there is a lack of systems-level understanding of treatment response mechanisms of EPCs. In this research we aimed to characterize the EPCs response to adenosine (Ado), a cardioprotective factor, based on the systems-level integration of gene expression data and prior functional knowledge. Specifically, we set out to identify novel biosignatures of Ado-treatment response in EPCs. Results The predictive integration of gene expression data and standardized functional similarity information enabled us to identify new treatment response biosignatures. Gene expression data originated from Ado-treated and -untreated EPCs samples, and functional similarity was estimated with Gene Ontology (GO)-based similarity information. These information sources enabled us to implement and evaluate an integrated prediction approach based on the concept of k-nearest neighbours learning (kNN). The method can be executed by expert- and data-driven input queries to guide the search for biologically meaningful biosignatures. The resulting integrated kNN system identified new candidate EPC biosignatures that can offer high classification performance (areas under the operating characteristic curve > 0.8). We also showed that the proposed models can outperform those discovered by standard gene expression analysis. Furthermore, we report an initial independent in vitro experimental follow-up, which provides additional evidence of the potential validity of the top biosignature. Conclusion Response to Ado treatment in EPCs can be accurately characterized with a new method based on the combination of gene co-expression data and GO-based similarity information. It also exploits the incorporation of human expert-driven queries as a strategy to guide the automated search for candidate biosignatures. The proposed biosignature improves the systems-level characterization of EPCs. The new integrative predictive modeling approach can also be applied to other phenotype characterization or biomarker discovery problems.
Collapse
Affiliation(s)
- Francisco J Azuaje
- Laboratory of Cardiovascular Research, Centre de Recherche Public-Santé, L-1150, Luxembourg.
| | | | | | | | | | | | | | | |
Collapse
|
8
|
Uhlenbrock K, Weiwad M, Wetzker R, Fischer G, Wittinghofer A, Rubio I. Reassessment of the role of FKBP38 in the Rheb/mTORC1 pathway. FEBS Lett 2009; 583:965-70. [PMID: 19222999 DOI: 10.1016/j.febslet.2009.02.015] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2009] [Accepted: 02/06/2009] [Indexed: 10/21/2022]
Abstract
The small G-protein Rheb regulates cell growth via the mTORC1 complex by incompletely understood mechanisms. Recent studies document that Rheb activates mTORC1 via direct, GTP-dependent interaction with the peptidyl-prolyl-cis/trans-isomerase FKBP38, which is proposed to act as an inhibitor of mTORC1. We have conducted a comprehensive biochemical characterization of the Rheb/FKBP38 interaction. Using three different in vitro assays we did not detect an interaction between Rheb and FKBP38. Cell biological experiments illustrate that FKBP38 plays only a very minor, if any, role in mTORC1 activation. Our data document that FKBP38 is not the long-sought Rheb effector linking Rheb to mTORC1 activation.
Collapse
Affiliation(s)
- Katharina Uhlenbrock
- Department of Structural Biology, Max Planck Institute for Molecular Physiology, Dortmund, Germany
| | | | | | | | | | | |
Collapse
|
9
|
Chen J, Wang L, Chen Y, Sternberg P, Cai J. Phosphatidylinositol 3 kinase pathway and 4-hydroxy-2-nonenal-induced oxidative injury in the RPE. Invest Ophthalmol Vis Sci 2008; 50:936-42. [PMID: 18806289 DOI: 10.1167/iovs.08-2439] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
PURPOSE 4-Hydroxy-2-nonenal (4-HNE) is a major lipid peroxidation product in the retina and the retinal pigment epithelium. The purpose of the present study was to investigate how NF-E2-related factor-2 (Nrf2) and phosphatidylinositol 3 (PI3K) pathways affect the responses of cultured human retinal pigment epithelial (RPE) cells to 4-HNE. METHODS Cultured ARPE-19 cells were treated with different concentrations of 4-HNE and a PI3K inhibitor, LY294002. Intracellular glutathione (GSH) was measured by high-performance liquid chromatography (HPLC). The transcriptional activity of Nrf2 was measured by dual luciferase assay after transient transfection with reporter plasmids. The mRNA level of glutamate cysteine ligase (GCL) was quantified by real-time RT-PCR. Formation of HNE adduct on heat shock cognate protein 70 (Hsc70) was measured by immunoprecipitation and Western blot analyses. RESULTS Treatment with 4-HNE increased Nrf2 activity and GSH synthesis in a dose-dependent manner in cultured RPE cells. The modulatory subunit of GCL was upregulated by 4-HNE. Antioxidant responses were largely abolished by pretreatment with LY294002. The modification of Hsc70 by 4-HNE was increased when PI3K was inhibited. CONCLUSIONS The Nrf2-dependent antioxidant response protects against 4-HNE toxicity, and this protective mechanism is dependent on the functions of the PI3K pathway.
Collapse
Affiliation(s)
- Jianbin Chen
- Vanderbilt Eye Institute, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
| | | | | | | | | |
Collapse
|