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Kruzel-Davila E, Bavli-Kertselli I, Ofir A, Cheatham AM, Shemer R, Zaknoun E, Chornyy S, Tabachnikov O, Davis SE, Khatua AK, Skorecki K, Popik W. Endoplasmic reticulum-translocation is essential for APOL1 cellular toxicity. iScience 2022; 25:103717. [PMID: 35072009 PMCID: PMC8762391 DOI: 10.1016/j.isci.2021.103717] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Revised: 11/17/2021] [Accepted: 12/29/2021] [Indexed: 11/28/2022] Open
Abstract
Two variants at the APOL1 gene, encoding apolipoprotein L1, account for more than 70% of the increased risk for chronic kidney disease in individuals of African ancestry. While the initiating event for APOL1 risk variant cell injury remains to be clarified, we explored the possibility of blocking APOL1 toxicity at a more upstream level. We demonstrate that deletion of the first six amino acids of exon 4 abrogates APOL1 cytotoxicity by impairing APOL1 translocation to the lumen of ER and splicing of the signal peptide. Likewise, in orthologous systems, APOL1 lethality was partially abrogated in yeast strains and flies with reduced dosage of genes encoding ER translocon proteins. An inhibitor of ER to Golgi trafficking reduced lethality as well. We suggest that targeting the MSALFL sequence or exon 4 skipping may serve as potential therapeutic approaches to mitigate the risk of CKD caused by APOL1 renal risk variants.
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Affiliation(s)
- Etty Kruzel-Davila
- Department of Nephrology, Rambam Health Care Campus, Haifa, Israel
- Departments of Genetics and Developmental Biology and Rappaport Faculty of Medicine and Research Institute, Technion—Israel Institute of Technology, Haifa, Israel
| | | | - Ayala Ofir
- Department of Nephrology, Rambam Health Care Campus, Haifa, Israel
| | - Amber M. Cheatham
- Meharry Medical College, Center for AIDS Health Disparities Research, Department of Microbiology and Immunology, 1005 D. B. Todd Boulevard, Nashville, TN 37028, USA
| | - Revital Shemer
- Departments of Genetics and Developmental Biology and Rappaport Faculty of Medicine and Research Institute, Technion—Israel Institute of Technology, Haifa, Israel
| | - Eid Zaknoun
- Departments of Genetics and Developmental Biology and Rappaport Faculty of Medicine and Research Institute, Technion—Israel Institute of Technology, Haifa, Israel
| | - Sergiy Chornyy
- Departments of Genetics and Developmental Biology and Rappaport Faculty of Medicine and Research Institute, Technion—Israel Institute of Technology, Haifa, Israel
| | - Orly Tabachnikov
- Department of Nephrology, Rambam Health Care Campus, Haifa, Israel
| | - Shamara E. Davis
- Meharry Medical College, Center for AIDS Health Disparities Research, Department of Microbiology and Immunology, 1005 D. B. Todd Boulevard, Nashville, TN 37028, USA
| | - Atanu K. Khatua
- Meharry Medical College, Center for AIDS Health Disparities Research, Department of Microbiology and Immunology, 1005 D. B. Todd Boulevard, Nashville, TN 37028, USA
| | - Karl Skorecki
- Department of Nephrology, Rambam Health Care Campus, Haifa, Israel
- Departments of Genetics and Developmental Biology and Rappaport Faculty of Medicine and Research Institute, Technion—Israel Institute of Technology, Haifa, Israel
| | - Waldemar Popik
- Meharry Medical College, Center for AIDS Health Disparities Research, Department of Microbiology and Immunology, 1005 D. B. Todd Boulevard, Nashville, TN 37028, USA
- Department of Internal Medicine, 1005 D. B. Todd Boulevard, Nashville, TN 37028, USA
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Davis SE, Khatua AK, Popik W. Nucleosomal dsDNA Stimulates APOL1 Expression in Human Cultured Podocytes by Activating the cGAS/IFI16-STING Signaling Pathway. Sci Rep 2019; 9:15485. [PMID: 31664093 PMCID: PMC6820523 DOI: 10.1038/s41598-019-51998-w] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Accepted: 10/08/2019] [Indexed: 12/31/2022] Open
Abstract
APOL1 alleles G1 and G2 are associated with faster progression to lupus nephritis (LN)-associated end-stage renal disease (LN-ESRD) in African Americans. Increased levels of type I interferons (IFNs) and nucleosome-associated double-stranded DNA (dsDNA) fragments (nsDNA) are the hallmark of this disease. Here, we identify cyclic GMP-AMP synthase (cGAS) and interferon-inducible protein 16 (IFI16) as the major DNA sensors in human immortalized podocytes. We also show that nsDNA triggers the expression of APOL1 and IFNβ via IRF3 activation through the cGAS/IFI16-STING pathway. We demonstrate that maximal APOL1 expression also requires the activation of type I IFN receptor (IFNAR) and STAT1 signaling triggered by IFNβ produced in response to nsDNA, or by exogenous IFNβ. Finally, we show that STAT1 activation is sufficient to upregulate IFI16, subsequently boosting APOL1 expression through a positive feedback mechanism. Collectively, we find that nsDNA-induced APOL1 expression is mediated by both IFNβ-independent and dependent signaling pathways triggered by activation of the cGAS/IFI16-STING pathway. We propose that simultaneous inhibition of STING and the IFNAR-STAT1 pathway may attenuate IFI16 expression, reduce IFI16-cGAS cross-talk, and prevent excessive APOL1 expression in human podocytes in response to nsDNA.
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Affiliation(s)
- Shamara E Davis
- Meharry Medical College, Center for AIDS Health Disparities Research, Department of Microbiology and Immunology, Nashville, TN, 37208, USA
| | - Atanu K Khatua
- Meharry Medical College, Center for AIDS Health Disparities Research, Department of Microbiology and Immunology, Nashville, TN, 37208, USA
| | - Waldemar Popik
- Meharry Medical College, Center for AIDS Health Disparities Research, Department of Microbiology and Immunology, Nashville, TN, 37208, USA.
- Department of Internal Medicine, 1005 D. B. Todd Blvd, Nashville, TN, 37208, USA.
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Popik W, Khatua AK, Fabre NF, Hildreth JEK, Alcendor DJ. BK Virus Replication in the Glomerular Vascular Unit: Implications for BK Virus Associated Nephropathy. Viruses 2019; 11:E583. [PMID: 31252545 PMCID: PMC6669441 DOI: 10.3390/v11070583] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Revised: 06/10/2019] [Accepted: 06/25/2019] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND BK polyomavirus (BKV) reactivates from latency after immunosuppression in renal transplant patients, resulting in BKV-associated nephropathy (BKVAN). BKVAN has emerged as an important cause of graft dysfunction and graft loss among transplant patients. BKV infection in kidney transplant patients has increased over recent decades which correlates with the use of more potent immunosuppressive therapies. BKV infection of the Glomerular Vascular Unit (GVU) consisting of podocytes, mesangial cells, and glomerular endothelial cells could lead to glomerular inflammation and contribute to renal fibrosis. The effects of BKV on GVU infectivity have not been reported. METHODS We infected GVU cells with the Dunlop strain of BKV. Viral infectivity was analyzed by microscopy, immunofluorescence, Western blot analysis, and quantitative RT-PCR (qRT-PCR). The expression of specific proinflammatory cytokines induced by BKV was analyzed by qRT-PCR. RESULTS BKV infection of podocytes, mesangial cells, and glomerular endothelial cells was confirmed by qRT-PCR and positive staining with antibodies to the BKV VP1 major capsid protein, or the SV40 Large T-Antigen. The increased transcriptional expression of interferon gamma-induced protein 10 (CXCL10/IP-10) and interferon beta (IFNβ) was detected in podocytes and mesangial cells at 96 h post-infection. CONCLUSIONS All cellular components of the GVU are permissive for BKV replication. Cytopathic effects induced by BKV in podocytes and glomerular endothelial cells and the expression of CXCL10 and IFNβ genes by podocytes and mesangial cells may together contribute to glomerular inflammation and cytopathology in BKVAN.
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Affiliation(s)
- Waldemar Popik
- Department of Internal Medicine, Meharry Medical College, Nashville, TN 37208-3599, USA
| | - Atanu K Khatua
- Department of Microbiology, Immunology and Physiology, Center for AIDS Health Disparities Research, 1005 Dr. D.B. Todd Jr. Blvd., Nashville, TN 37208-3599, USA
| | - Noyna F Fabre
- Department of Microbiology, Immunology and Physiology, Center for AIDS Health Disparities Research, 1005 Dr. D.B. Todd Jr. Blvd., Nashville, TN 37208-3599, USA
| | - James E K Hildreth
- Department of Internal Medicine, Meharry Medical College, Nashville, TN 37208-3599, USA
| | - Donald J Alcendor
- Department of Microbiology, Immunology and Physiology, Center for AIDS Health Disparities Research, 1005 Dr. D.B. Todd Jr. Blvd., Nashville, TN 37208-3599, USA.
- Department of Obstetrics and Gynecology, Meharry Medical College, School of Medicine, 1005 Dr. D.B. Todd Jr. Blvd., Nashville, TN 37208-3599, USA.
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Cheatham AM, Davis SE, Khatua AK, Popik W. Blocking the 5' splice site of exon 4 by a morpholino oligomer triggers APOL1 protein isoform switch. Sci Rep 2018; 8:8739. [PMID: 29880816 PMCID: PMC5992166 DOI: 10.1038/s41598-018-27104-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Accepted: 05/21/2018] [Indexed: 12/16/2022] Open
Abstract
APOL1 risk alleles G1 or G2 are associated with a kidney disease phenotype exclusively in people of recent African ancestry. Here we show that exon 4 encoding a part of the APOL1 signal peptide is constitutively spliced in major APOL1 transcripts expressed in kidney glomerular and tubular cells. We demonstrate that constitutive splicing of exon 4 results from a suboptimal hnRNP A1 binding motif found in exon 4. Accordingly, a robust binding of hnRNP A1 protein to a consensus hnRNP A1 cis-acting element in exon 4 results in almost complete exclusion of exon 4 from the APOL1 minigene transcripts. Blocking the 5' splice site at the exon 4/intron boundary with a specific antisense morpholino oligonucleotide excludes exon 4 from the splicing pattern of endogenous APOL1 transcripts. These transcripts are fully functional and produce APOL1 protein isoform that is not normally detectable in podocytes. Together with our previous data showing no cytotoxicity of overexpressed APOL1 isoform lacking exon 4, we propose that morpholino-induced APOL1 isoform switch may provide a new tool to identify in vivo molecular mechanism(s) by which risk alleles promote or mediate the kidney disease phenotype.
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Affiliation(s)
- Amber M Cheatham
- Meharry Medical College, Center for AIDS Health Disparities Research, Department of Microbiology and Immunology, 1005 D. B. Todd Blvd, Nashville, TN, 37028, USA
| | - Shamara E Davis
- Meharry Medical College, Center for AIDS Health Disparities Research, Department of Microbiology and Immunology, 1005 D. B. Todd Blvd, Nashville, TN, 37028, USA
| | - Atanu K Khatua
- Meharry Medical College, Center for AIDS Health Disparities Research, Department of Microbiology and Immunology, 1005 D. B. Todd Blvd, Nashville, TN, 37028, USA
| | - Waldemar Popik
- Meharry Medical College, Center for AIDS Health Disparities Research, Department of Microbiology and Immunology, 1005 D. B. Todd Blvd, Nashville, TN, 37028, USA.
- Department of Internal Medicine, 1005 D. B. Todd Blvd, Nashville, TN, 37028, USA.
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Taylor HE, Simmons GE, Mathews TP, Khatua AK, Popik W, Lindsley CW, D’Aquila RT, Brown HA. Phospholipase D1 Couples CD4+ T Cell Activation to c-Myc-Dependent Deoxyribonucleotide Pool Expansion and HIV-1 Replication. PLoS Pathog 2015; 11:e1004864. [PMID: 26020637 PMCID: PMC4447393 DOI: 10.1371/journal.ppat.1004864] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 04/07/2015] [Indexed: 12/25/2022] Open
Abstract
Quiescent CD4+ T cells restrict human immunodeficiency virus type 1 (HIV-1) infection at early steps of virus replication. Low levels of both deoxyribonucleotide triphosphates (dNTPs) and the biosynthetic enzymes required for their de novo synthesis provide one barrier to infection. CD4+ T cell activation induces metabolic reprogramming that reverses this block and facilitates HIV-1 replication. Here, we show that phospholipase D1 (PLD1) links T cell activation signals to increased HIV-1 permissivity by triggering a c-Myc-dependent transcriptional program that coordinates glucose uptake and nucleotide biosynthesis. Decreasing PLD1 activity pharmacologically or by RNA interference diminished c-Myc-dependent expression during T cell activation at the RNA and protein levels. PLD1 inhibition of HIV-1 infection was partially rescued by adding exogenous deoxyribonucleosides that bypass the need for de novo dNTP synthesis. Moreover, the data indicate that low dNTP levels that impact HIV-1 restriction involve decreased synthesis, and not only increased catabolism of these nucleotides. These findings uncover a unique mechanism of action for PLD1 inhibitors and support their further development as part of a therapeutic combination for HIV-1 and other viral infections dependent on host nucleotide biosynthesis.
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Affiliation(s)
- Harry E. Taylor
- Northwestern HIV Translational Research Center, Division of Infectious Diseases, Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America
- * E-mail: (HET); (HAB)
| | - Glenn E. Simmons
- Department of Molecular Genetics, University of Texas, Southwestern Medical Center, Dallas, Texas, United States of America
| | - Thomas P. Mathews
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Atanu K. Khatua
- Meharry Medical College, Center for AIDS Health Disparities Research, Nashville, Tennessee, United States of America
| | - Waldemar Popik
- Meharry Medical College, Center for AIDS Health Disparities Research, Nashville, Tennessee, United States of America
| | - Craig W. Lindsley
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University, Nashville, Tennessee, United States of America
- Department of Chemistry, Vanderbilt University, Nashville, Tennesee, United States of America
- Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Richard T. D’Aquila
- Northwestern HIV Translational Research Center, Division of Infectious Diseases, Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America
| | - H. Alex Brown
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee, United States of America
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
- * E-mail: (HET); (HAB)
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Khatua AK, Cheatham AM, Kruzel ED, Singhal PC, Skorecki K, Popik W. Exon 4-encoded sequence is a major determinant of cytotoxicity of apolipoprotein L1. Am J Physiol Cell Physiol 2015; 309:C22-37. [PMID: 25924622 DOI: 10.1152/ajpcell.00384.2014] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 04/24/2015] [Indexed: 12/17/2022]
Abstract
The apolipoprotein L1 (APOL1) gene (APOL1) product is toxic to kidney cells, and its G1 and G2 alleles are strongly associated with increased risk for kidney disease progression in African Americans. Variable penetrance of the G1 and G2 risk alleles highlights the significance of additional factors that trigger or modify the progression of disease. In this regard, the effect of alternative splicing in the absence or presence of G1 or G2 alleles is unknown. In this study we investigated whether alternative splicing of non-G1, non-G2 APOL1 (APOL1 G0) affects its biological activity. Among seven APOL1 exons, exons 2 and 4 are differentially expressed in major transcripts. We found that, in contrast to APOL1 splice variants B3 or C, variants A and B1 demonstrate strong toxicity in human embryonic kidney (HEK293T) cells. Subsequently, we established that exon 4 is a major determinant of toxicity of variants A and B1 and that extracellular release of these variants is dispensable for their cytotoxicity. Although only variants A and B1 induced nuclear translocation of transcription factor EB (TFEB), a master regulator of lysosomal biogenesis and autophagy, exon 4-positive and -negative APOL1 variants stimulated perinuclear accumulation of unprocessed autophagosomes. Knockdown of endogenous TFEB did not attenuate APOL1 cytotoxicity, indicating that nuclear translocation of TFEB is dispensable for APOL1 toxicity. Our findings that a human podocyte cell line expresses exon 4-positive and -negative APOL1 transcripts suggest that these variants may play a differential role in podocyte pathology. In summary, we have identified exon 4 as a major determinant of APOL1 G0 cytotoxicity.
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Affiliation(s)
- Atanu K Khatua
- Meharry Medical College, Center for AIDS Health Disparities Research, Nashville, Tennessee
| | - Amber M Cheatham
- Meharry Medical College, Center for AIDS Health Disparities Research, Nashville, Tennessee
| | - Etty D Kruzel
- Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Rambam Medical Center, Haifa, Israel; and
| | | | - Karl Skorecki
- Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Rambam Medical Center, Haifa, Israel; and
| | - Waldemar Popik
- Meharry Medical College, Center for AIDS Health Disparities Research, Nashville, Tennessee;
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Paria BC, Khatua AK, Reese J. Complement Component 1, q Subcomponent Binding Protein (C1QBP) Gene in the Hamster Uterus: Identification, Hormonal Regulation, and Expression in the Periimplantation Uterus. Biol Reprod 2011. [DOI: 10.1093/biolreprod/85.s1.469] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Khatua AK, Taylor HE, Hildreth JEK, Popik W. Non-productive HIV-1 infection of human glomerular and urinary podocytes. Virology 2010; 408:119-27. [PMID: 20937511 DOI: 10.1016/j.virol.2010.09.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2010] [Revised: 07/28/2010] [Accepted: 09/04/2010] [Indexed: 01/02/2023]
Abstract
Podocyte damage induced by HIV-1 is critical to the pathogenesis of HIV-1 associated nephropathy (HIVAN) and is believed to result from productive replication of the virus. Here we demonstrate that HIV-1 readily enters human podocytes by a dynamin-mediated endocytosis but does not establish productive infection. We provide evidence suggesting that viral nucleic acids and proteins detected in podocytes are delivered by viral particles internalized by the cells. Endocytosed HIV-1 is only transiently harbored by podocytes and is subsequently released to the extracellular milieu as fully infectious virus. Similarly, primary podocytes established from normal human urine do not support productive infection by HIV-1 but sustain replication of VSV-G pseudotyped virus that bypasses HIV-1 entry receptors. Moreover, transfected podocytes expressing CD4 and CXCR4 receptors support productive replication of HIV-1. This further confirms that lack of HIV-1 entry receptors is the major barrier preventing productive infection of podocytes in vitro.
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Affiliation(s)
- Atanu K Khatua
- Center for AIDS Health Disparities Research, Meharry Medical College, 1005 D. B. Todd Blvd., Nashville, TN 37208, USA
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Khatua AK, Taylor HE, Hildreth JEK, Popik W. Inhibition of LINE-1 and Alu retrotransposition by exosomes encapsidating APOBEC3G and APOBEC3F. Virology 2010; 400:68-75. [PMID: 20153011 DOI: 10.1016/j.virol.2010.01.021] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2009] [Revised: 11/18/2009] [Accepted: 01/15/2010] [Indexed: 10/19/2022]
Abstract
Human cytidine deaminases, including APOBEC3G (A3G) and A3F, are part of a cellular defense system against retroviruses and retroelements including non-LTR retrotransposons LINE-1 (L1) and Alu. Expression of cellular A3 proteins is sufficient for inhibition of L1 and Alu retrotransposition, but the effect of A3 proteins transferred in exosomes on retroelement mobilization is unknown. Here, we demonstrate for the first time that exosomes secreted by CD4(+)H9 T cells and mature monocyte-derived dendritic cells encapsidate A3G and A3F and inhibit L1 and Alu retrotransposition. A3G is the major contributor to the inhibitory activity of exosomes, however, the contribution of A3F in H9 exosomes cannot be excluded. Additionally, we show that exosomes encapsidate mRNAs coding for A3 proteins. A3G mRNA, and less so A3F, was enriched in exosomes secreted by H9 cells. Exosomal A3G mRNA was functional in vitro. Whether exosomes inhibit retrotransposons in vivo requires further investigation.
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Affiliation(s)
- Atanu K Khatua
- Center for AIDS Health Disparities Research, Meharry Medical College, 1005 D. B. Todd Blvd., Nashville, TN 37208, USA
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Ochieng J, Pratap S, Khatua AK, Sakwe AM. Anchorage-independent growth of breast carcinoma cells is mediated by serum exosomes. Exp Cell Res 2009; 315:1875-88. [PMID: 19327352 DOI: 10.1016/j.yexcr.2009.03.010] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2008] [Revised: 03/13/2009] [Accepted: 03/13/2009] [Indexed: 12/13/2022]
Abstract
We hereby report studies that suggest a role for serum exosomes in the anchorage-independent growth (AIG) of tumor cells. In AIG assays, fetal bovine serum is one of the critical ingredients. We therefore purified exosomes from fetal bovine serum and examined their potential to promote growth of breast carcinoma cells in soft agar and Matrigel after reconstituting them into growth medium (EEM). In all the assays, viable colonies were formed only in the presence of exosomes. Some of the exosomal proteins we identified, have been documented by others and could be considered exosomal markers. Labeled purified exosomes were up-taken by the tumor cells, a process that could be competed out with excess unlabeled vesicles. Our data also suggested that once endocytosed by a cell, the exosomes could be recycled back to the conditioned medium from where they can be up-taken by other cells. We also demonstrated that low concentrations of exosomes activate MAP kinases, suggesting a mechanism by which they maintain the growth of the tumor cells in soft agar. Taken together, our data demonstrate that serum exosomes form a growth promoting platform for AIG of tumor cells and may open a new vista into cancer cell growth in vivo.
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Affiliation(s)
- Josiah Ochieng
- Department of Cancer Biology, Meharry Medical College, Nashville, TN 37208, USA.
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Khatua AK, Bhattacharyya M. NADPH-induced oxidative damage of rat liver microsomes: protective role of chlorpromazine and trifluoperazine. Pol J Pharmacol 2001; 53:629-34. [PMID: 11985337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
Abstract
Two widely used antipsychotic drugs, chlorpromazine (CPZ) and trifluoperazine (TFZ) inhibit NADPH-induced microsomal lipid peroxidation (LPO). Study of microsomal membrane fluidity revealed considerable disorganization in its architecture in the presence of NADPH, which can be restored back in the presence of CPZ and TFZ. NADPH-dependent microsomal LPO is catalyzed by NADPH: cytochrome P450 reductase. These drugs also inhibit the activity of this enzyme. TFZ always shows stronger inhibitory effect than CPZ. TFZ contains a trifluromethyl group (CF3) in its second position that gives rise to stronger electron abstraction tendency by which LPO and NADPH: cytochrome P450 reductase activity is inhibited more potently than by CPZ which contains a chlorine ligand in the same position. Due to the stronger antioxidant property of TFZ, it can be prescribed as a better therapeutic agent, which plays a protective role for the cellular system.
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Affiliation(s)
- A K Khatua
- Department of Biochemistry, University College of Science and Technology, Calcutta, India.
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