1
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Datta S, Antonio BM, Zahler NH, Theile JW, Krafte D, Zhang H, Rosenberg PB, Chaves AB, Muoio DM, Zhang G, Silas D, Li G, Soldano K, Nystrom S, Ferreira D, Miller SE, Bain JR, Muehlbauer MJ, Ilkayeva O, Becker TC, Hohmeier HE, Newgard CB, Olabisi OA. APOL1-mediated monovalent cation transport contributes to APOL1-mediated podocytopathy in kidney disease. J Clin Invest 2024; 134:e172262. [PMID: 38227370 PMCID: PMC10904047 DOI: 10.1172/jci172262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Accepted: 01/09/2024] [Indexed: 01/17/2024] Open
Abstract
Two coding variants of apolipoprotein L1 (APOL1), called G1 and G2, explain much of the excess risk of kidney disease in African Americans. While various cytotoxic phenotypes have been reported in experimental models, the proximal mechanism by which G1 and G2 cause kidney disease is poorly understood. Here, we leveraged 3 experimental models and a recently reported small molecule blocker of APOL1 protein, VX-147, to identify the upstream mechanism of G1-induced cytotoxicity. In HEK293 cells, we demonstrated that G1-mediated Na+ import/K+ efflux triggered activation of GPCR/IP3-mediated calcium release from the ER, impaired mitochondrial ATP production, and impaired translation, which were all reversed by VX-147. In human urine-derived podocyte-like epithelial cells (HUPECs), we demonstrated that G1 caused cytotoxicity that was again reversible by VX-147. Finally, in podocytes isolated from APOL1 G1 transgenic mice, we showed that IFN-γ-mediated induction of G1 caused K+ efflux, activation of GPCR/IP3 signaling, and inhibition of translation, podocyte injury, and proteinuria, all reversed by VX-147. Together, these results establish APOL1-mediated Na+/K+ transport as the proximal driver of APOL1-mediated kidney disease.
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Affiliation(s)
- Somenath Datta
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Duke University School of Medicine, Department of Medicine, Division of Nephrology, Durham, North Carolina, USA
| | | | | | | | | | - Hengtao Zhang
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Medicine, Division of Cardiology, Duke University School of Medicine, Durham, North Carolina, USA
| | - Paul B. Rosenberg
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Medicine, Division of Cardiology, Duke University School of Medicine, Durham, North Carolina, USA
| | - Alec B. Chaves
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
| | - Deborah M. Muoio
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Medicine, Division of Endocrinology, Metabolism, and Nutrition, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina, USA
| | - Guofang Zhang
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Medicine, Division of Endocrinology, Metabolism, and Nutrition, Duke University School of Medicine, Durham, North Carolina, USA
| | - Daniel Silas
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Duke University School of Medicine, Department of Medicine, Division of Nephrology, Durham, North Carolina, USA
| | - Guojie Li
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Duke University School of Medicine, Department of Medicine, Division of Nephrology, Durham, North Carolina, USA
| | - Karen Soldano
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Duke University School of Medicine, Department of Medicine, Division of Nephrology, Durham, North Carolina, USA
| | - Sarah Nystrom
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Duke University School of Medicine, Department of Medicine, Division of Nephrology, Durham, North Carolina, USA
| | - Davis Ferreira
- Department of Pathology, Duke University Medical Center, Durham, North Carolina, USA
| | - Sara E. Miller
- Department of Pathology, Duke University Medical Center, Durham, North Carolina, USA
| | - James R. Bain
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Medicine, Division of Endocrinology, Metabolism, and Nutrition, Duke University School of Medicine, Durham, North Carolina, USA
| | - Michael J. Muehlbauer
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
| | - Olga Ilkayeva
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Medicine, Division of Endocrinology, Metabolism, and Nutrition, Duke University School of Medicine, Durham, North Carolina, USA
| | - Thomas C. Becker
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Medicine, Division of Endocrinology, Metabolism, and Nutrition, Duke University School of Medicine, Durham, North Carolina, USA
| | - Hans-Ewald Hohmeier
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Medicine, Division of Endocrinology, Metabolism, and Nutrition, Duke University School of Medicine, Durham, North Carolina, USA
| | - Christopher B. Newgard
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Medicine, Division of Endocrinology, Metabolism, and Nutrition, Duke University School of Medicine, Durham, North Carolina, USA
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina, USA
| | - Opeyemi A. Olabisi
- Duke Molecular Physiology Institute and Sarah W. Stedman Nutrition and Metabolism Center, Duke University School of Medicine, Durham, North Carolina, USA
- Duke University School of Medicine, Department of Medicine, Division of Nephrology, Durham, North Carolina, USA
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2
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Vandorpe DH, Heneghan JF, Waitzman JS, McCarthy GM, Blasio A, Magraner JM, Donovan OG, Schaller LB, Shah SS, Subramanian B, Riella CV, Friedman DJ, Pollak MR, Alper SL. Apolipoprotein L1 (APOL1) cation current in HEK-293 cells and in human podocytes. Pflugers Arch 2023; 475:323-341. [PMID: 36449077 DOI: 10.1007/s00424-022-02767-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Revised: 10/14/2022] [Accepted: 10/25/2022] [Indexed: 12/05/2022]
Abstract
Two heterozygous missense variants (G1 and G2) of Apolipoprotein L1 (APOL1) found in individuals of recent African ancestry can attenuate the severity of infection by some forms of Trypanosoma brucei. However, these two variants within a broader African haplotype also increase the risk of kidney disease in Americans of African descent. Although overexpression of either variant G1 or G2 causes multiple pathogenic changes in cultured cells and transgenic mouse models, the mechanism(s) promoting kidney disease remain unclear. Human serum APOL1 kills trypanosomes through its cation channel activity, and cation channel activity of recombinant APOL1 has been reconstituted in lipid bilayers and proteoliposomes. Although APOL1 overexpression increases whole cell cation currents in HEK-293 cells, the ion channel activity of APOL1 has not been assessed in glomerular podocytes, the major site of APOL1-associated kidney diseases. We characterize APOL1-associated whole cell and on-cell cation currents in HEK-293 T-Rex cells and demonstrate partial inhibition of currents by anti-APOL antibodies. We detect in primary human podocytes a similar cation current inducible by interferon-γ (IFNγ) and sensitive to inhibition by anti-APOL antibody as well as by a fragment of T. brucei Serum Resistance-Associated protein (SRA). CRISPR knockout of APOL1 in human primary podocytes abrogates the IFNγ-induced, antibody-sensitive current. Our novel characterization in HEK-293 cells of heterologous APOL1-associated cation conductance inhibited by anti-APOL antibody and our documentation in primary human glomerular podocytes of endogenous IFNγ-stimulated, APOL1-mediated, SRA and anti-APOL-sensitive ion channel activity together support APOL1-mediated channel activity as a therapeutic target for treatment of APOL1-associated kidney diseases.
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Affiliation(s)
- David H Vandorpe
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Department of Medicine, Harvard Medical School, Boston, MA, 02115, USA
| | - John F Heneghan
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Department of Pathology, Brigham and Women's Hospital, Boston, MA, 02215, USA
| | - Joshua S Waitzman
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Department of Medicine, Harvard Medical School, Boston, MA, 02115, USA
| | - Gizelle M McCarthy
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Vertex Pharmaceuticals, Boston, MA, 02210, USA
| | - Angelo Blasio
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Vertex Pharmaceuticals, Boston, MA, 02210, USA
| | - Jose M Magraner
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,, San Diego, CA, USA
| | - Olivia G Donovan
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA
| | - Lena B Schaller
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Ludwig-Maximilians-Universitaet, 80336, Munich, Germany
| | - Shrijal S Shah
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Chroma Medicine, Cambridge, MA, 02142, USA
| | - Balajikarthick Subramanian
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Department of Medicine, Harvard Medical School, Boston, MA, 02115, USA
| | - Cristian V Riella
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Department of Medicine, Harvard Medical School, Boston, MA, 02115, USA
| | - David J Friedman
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Department of Medicine, Harvard Medical School, Boston, MA, 02115, USA.,Broad Institute of Harvard and MIT, Cambridge, MA, 02139, USA
| | - Martin R Pollak
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA.,Department of Medicine, Harvard Medical School, Boston, MA, 02115, USA.,Broad Institute of Harvard and MIT, Cambridge, MA, 02139, USA
| | - Seth L Alper
- Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center RN380F, 99 Brookline Ave, Boston, MA, 02215, USA. .,Department of Medicine, Harvard Medical School, Boston, MA, 02115, USA. .,Broad Institute of Harvard and MIT, Cambridge, MA, 02139, USA.
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3
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Blazer A, Qian Y, Schlegel MP, Algasas H, Buyon JP, Cadwell K, Cammer M, Heffron SP, Liang FX, Mehta-Lee S, Niewold T, Rasmussen SE, Clancy RM. APOL1 variant-expressing endothelial cells exhibit autophagic dysfunction and mitochondrial stress. Front Genet 2022; 13:769936. [PMID: 36238153 PMCID: PMC9551299 DOI: 10.3389/fgene.2022.769936] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Accepted: 08/16/2022] [Indexed: 12/09/2022] Open
Abstract
Polymorphisms in the Apolipoprotein L1 (APOL1) gene are common in ancestrally African populations, and associate with kidney injury and cardiovascular disease. These risk variants (RV) provide an advantage in resisting Trypanosoma brucei, the causal agent of African trypanosomiasis, and are largely absent from non-African genomes. Clinical associations between the APOL1 high risk genotype (HRG) and disease are stronger in those with comorbid infectious or immune disease. To understand the interaction between cytokine exposure and APOL1 cytotoxicity, we established human umbilical vein endothelial cell (HUVEC) cultures representing each APOL1 genotype. Untreated HUVECs were compared to IFNɣ-exposed; and APOL1 expression, mitochondrial function, lysosome integrity, and autophagic flux were measured. IFNɣ increased median APOL1 expression across all genotypes 22.1 (8.3 to 29.8) fold (p=0.02). Compared to zero risk variant-carrying HUVECs (0RV), HUVECs carrying 2 risk variant copies (2RV) showed both depressed baseline and maximum mitochondrial oxygen consumption (p<0.01), and impaired mitochondrial networking on MitoTracker assays. These cells also demonstrated a contracted lysosomal compartment, and an accumulation of autophagosomes suggesting a defect in autophagic flux. Upon blocking autophagy with non-selective lysosome inhibitor, hydroxychloroquine, autophagosome accumulation between 0RV HUVECs and untreated 2RV HUVECs was similar, implicating lysosomal dysfunction in the HRG-associated autophagy defect. Compared to 0RV and 2RV HUVECs, HUVECs carrying 1 risk variant copy (1RV) demonstrated intermediate mitochondrial respiration and autophagic flux phenotypes, which were exacerbated with IFNɣ exposure. Taken together, our data reveal that IFNɣ induces APOL1 expression, and that each additional RV associates with mitochondrial dysfunction and autophagy inhibition. IFNɣ amplifies this phenotype even in 1RV HUVECs, representing the first description of APOL1 pathobiology in variant heterozygous cell cultures.
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Affiliation(s)
- Ashira Blazer
- Division of Rheumatology, Department of Medicine, Hospital for Special Surgery, New York, NY, United States
| | - Yingzhi Qian
- Division of Biostatistics, Department of Population Health, New York University School of Medicine, New York, NY, United States
| | - Martin Paul Schlegel
- Division of Cardiology, Department of Medicine, New York University School of Medicine, New York, NY, United States
| | - Huda Algasas
- Division of Rheumatology, Department of Medicine, Hospital for Special Surgery, New York, NY, United States
| | - Jill P. Buyon
- Division of Rheumatology, Department of Medicine, New York University Grossman School of Medicine, New York, NY, United States
| | - Ken Cadwell
- Department of Microbiology, New York University Grossman School of Medicine, New York, NY, United States
| | - Michael Cammer
- DART Microscopy Laboratory, New York University Grossman School of Medicine, New York University School of Medicine, New York, NY, United States
| | - Sean P. Heffron
- Division of Cardiology, Department of Medicine, New York University School of Medicine, New York, NY, United States
| | - Feng-Xia Liang
- DART Microscopy Laboratory, New York University Grossman School of Medicine, New York University School of Medicine, New York, NY, United States
| | - Shilpi Mehta-Lee
- Department of Obstetrics and Gynecology, New York University Grossman School of Medicine, New York, NY, United States
| | - Timothy Niewold
- Division of Rheumatology, Department of Medicine, Hospital for Special Surgery, New York, NY, United States
| | - Sara E. Rasmussen
- Division of Rheumatology, Department of Medicine, Hospital for Special Surgery, New York, NY, United States
| | - Robert M. Clancy
- Division of Rheumatology, Department of Medicine, New York University Grossman School of Medicine, New York, NY, United States
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4
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Daneshpajouhnejad P, Kopp JB, Winkler CA, Rosenberg AZ. The evolving story of apolipoprotein L1 nephropathy: the end of the beginning. Nat Rev Nephrol 2022; 18:307-320. [PMID: 35217848 PMCID: PMC8877744 DOI: 10.1038/s41581-022-00538-3] [Citation(s) in RCA: 34] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/14/2022] [Indexed: 01/13/2023]
Abstract
Genetic coding variants in APOL1, which encodes apolipoprotein L1 (APOL1), were identified in 2010 and are relatively common among individuals of sub-Saharan African ancestry. Approximately 13% of African Americans carry two APOL1 risk alleles. These variants, termed G1 and G2, are a frequent cause of kidney disease — termed APOL1 nephropathy — that typically manifests as focal segmental glomerulosclerosis and the clinical syndrome of hypertension and arterionephrosclerosis. Cell culture studies suggest that APOL1 variants cause cell dysfunction through several processes, including alterations in cation channel activity, inflammasome activation, increased endoplasmic reticulum stress, activation of protein kinase R, mitochondrial dysfunction and disruption of APOL1 ubiquitinylation. Risk of APOL1 nephropathy is mostly confined to individuals with two APOL1 risk variants. However, only a minority of individuals with two APOL1 risk alleles develop kidney disease, suggesting the need for a ‘second hit’. The best recognized factor responsible for this ‘second hit’ is a chronic viral infection, particularly HIV-1, resulting in interferon-mediated activation of the APOL1 promoter, although most individuals with APOL1 nephropathy do not have an obvious cofactor. Current therapies for APOL1 nephropathies are not adequate to halt progression of chronic kidney disease, and new targeted molecular therapies are in clinical trials. This Review summarizes current understanding of the role of APOL1 variants in kidney disease. The authors discuss the genetics, protein structure and biological functions of APOL1 variants and provide an overview of promising therapeutic strategies. In contrast to other APOL family members, which are primarily intracellular, APOL1 contains a unique secretory signal peptide, resulting in its secretion into plasma. APOL1 renal risk alleles provide protection from African human trypanosomiasis but are a risk factor for progressive kidney disease in those carrying two risk alleles. APOL1 risk allele frequency is ~35% in the African American population in the United States, with ~13% of individuals having two risk alleles; the highest allele frequencies are found in West African populations and their descendants. Cell and mouse models implicate endolysosomal and mitochondrial dysfunction, altered ion channel activity, altered autophagy, and activation of protein kinase R in the pathogenesis of APOL1-associated kidney disease; however, the relevance of these injury pathways to human disease has not been resolved. APOL1 kidney disease tends to be progressive, and current standard therapies are generally ineffective; targeted therapeutic strategies hold the most promise.
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Affiliation(s)
- Parnaz Daneshpajouhnejad
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.,Department of Pathology, University of Pennsylvania Hospital, Philadelphia, PA, USA
| | | | - Cheryl A Winkler
- Basic Research Program, Frederick National Laboratory for Cancer Research, Frederick, MD, USA
| | - Avi Z Rosenberg
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
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5
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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: 4] [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: 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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6
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Müller D, Schmitz J, Fischer K, Granado D, Groh AC, Krausel V, Lüttgenau SM, Amelung TM, Pavenstädt H, Weide T. Evolution of renal-disease factor APOL1 results in cis and trans orientations at the endoplasmic reticulum that both show cytotoxic effects. Mol Biol Evol 2021; 38:4962-4976. [PMID: 34323996 PMCID: PMC8557400 DOI: 10.1093/molbev/msab220] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The recent and exclusively in humans and a few other higher primates expressed APOL1 (apolipoprotein L1) gene is linked to African human trypanosomiasis (also known as African sleeping sickness) as well as to different forms of kidney diseases. Whereas APOL1’s role as a trypanolytic factor is well established, pathobiological mechanisms explaining its cytotoxicity in renal cells remain unclear. In this study, we compared the APOL family members using a combination of evolutionary studies and cell biological experiments to detect unique features causal for APOL1 nephrotoxic effects. We investigated available primate and mouse genome and transcriptome data to apply comparative phylogenetic and maximum likelihood selection analyses. We suggest that the APOL gene family evolved early in vertebrates and initial splitting occurred in ancestral mammals. Diversification and differentiation of functional domains continued in primates, including developing the two members APOL1 and APOL2. Their close relationship could be diagnosed by sequence similarity and a shared ancestral insertion of an AluY transposable element. Live-cell imaging analyses showed that both expressed proteins show a strong preference to localize at the endoplasmic reticulum (ER). However, glycosylation and secretion assays revealed that—unlike APOL2—APOL1 membrane insertion or association occurs in different orientations at the ER, with the disease-associated mutants facing either the luminal (cis) or cytoplasmic (trans) side of the ER. The various pools of APOL1 at the ER offer a novel perspective in explaining the broad spectrum of its observed toxic effects.
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Affiliation(s)
- Daria Müller
- University Hospital of Münster (UKM), Internal Medicine D (MedD), Molecular Nephrology, Albert-Schweitzer-Campus 1 Building A14, Münster, 48149, Germany
| | - Jürgen Schmitz
- Institute of Experimental Pathology, ZMBE, University of Münster, Von-Esmarch-Str. 56, Münster, D-48149, Germany
| | - Katharina Fischer
- University Hospital of Münster (UKM), Internal Medicine D (MedD), Molecular Nephrology, Albert-Schweitzer-Campus 1 Building A14, Münster, 48149, Germany
| | - Daniel Granado
- University Hospital of Münster (UKM), Internal Medicine D (MedD), Molecular Nephrology, Albert-Schweitzer-Campus 1 Building A14, Münster, 48149, Germany
| | - Ann-Christin Groh
- University Hospital of Münster (UKM), Internal Medicine D (MedD), Molecular Nephrology, Albert-Schweitzer-Campus 1 Building A14, Münster, 48149, Germany
| | - Vanessa Krausel
- University Hospital of Münster (UKM), Internal Medicine D (MedD), Molecular Nephrology, Albert-Schweitzer-Campus 1 Building A14, Münster, 48149, Germany
| | - Simona Mareike Lüttgenau
- University Hospital of Münster (UKM), Internal Medicine D (MedD), Molecular Nephrology, Albert-Schweitzer-Campus 1 Building A14, Münster, 48149, Germany
| | - Till Maximilian Amelung
- University Hospital of Münster (UKM), Internal Medicine D (MedD), Molecular Nephrology, Albert-Schweitzer-Campus 1 Building A14, Münster, 48149, Germany
| | - Hermann Pavenstädt
- University Hospital of Münster (UKM), Internal Medicine D (MedD), Molecular Nephrology, Albert-Schweitzer-Campus 1 Building A14, Münster, 48149, Germany
| | - Thomas Weide
- University Hospital of Münster (UKM), Internal Medicine D (MedD), Molecular Nephrology, Albert-Schweitzer-Campus 1 Building A14, Münster, 48149, Germany
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7
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Ekulu PM, Adebayo OC, Decuypere JP, Bellucci L, Elmonem MA, Nkoy AB, Mekahli D, Bussolati B, van den Heuvel LP, Arcolino FO, Levtchenko EN. Novel Human Podocyte Cell Model Carrying G2/G2 APOL1 High-Risk Genotype. Cells 2021; 10:cells10081914. [PMID: 34440683 PMCID: PMC8391400 DOI: 10.3390/cells10081914] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 07/20/2021] [Accepted: 07/23/2021] [Indexed: 02/01/2023] Open
Abstract
Apolipoprotein L1 (APOL1) high-risk genotypes (HRG), G1 and G2, increase the risk of various non-diabetic kidney diseases in the African population. To date, the precise mechanisms by which APOL1 risk variants induce injury on podocytes and other kidney cells remain unclear. Trying to unravel these mechanisms, most studies have used animal or cell models created by gene editing. We developed and characterised conditionally immortalised human podocyte cell lines derived from urine of a donor carrying APOL1 HRG G2/G2. Following induction of APOL1 expression by polyinosinic-polycytidylic acid (poly(I:C)), we assessed functional features of APOL1-induced podocyte dysfunction. As control, APOL1 wild type (G0/G0) podocyte cell line previously generated from a Caucasian donor was used. Upon exposure to poly(I:C), G2/G2 and G0/G0 podocytes upregulated APOL1 expression resulting in podocytes detachment, decreased cells viability and increased apoptosis rate in a genotype-independent manner. Nevertheless, G2/G2 podocyte cell lines exhibited altered features, including upregulation of CD2AP, alteration of cytoskeleton, reduction of autophagic flux and increased permeability in an in vitro model under continuous perfusion. The human APOL1 G2/G2 podocyte cell model is a useful tool for unravelling the mechanisms of APOL1-induced podocyte injury and the cellular functions of APOL1.
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Affiliation(s)
- Pepe M. Ekulu
- Department of Development and Regeneration, Katholieke Universiteit Leuven, 3000 Leuven, Belgium; (P.M.E.); (O.C.A.); (J.-P.D.); (A.B.N.); (D.M.); (L.P.v.d.H.); (E.N.L.)
- Department of Paediatrics, Division of Nephrology, Faculty of Medicine, University Hospital of Kinshasa, University of Kinshasa, Kinshasa, Democratic Republic of the Congo
| | - Oyindamola C. Adebayo
- Department of Development and Regeneration, Katholieke Universiteit Leuven, 3000 Leuven, Belgium; (P.M.E.); (O.C.A.); (J.-P.D.); (A.B.N.); (D.M.); (L.P.v.d.H.); (E.N.L.)
- Centre for Molecular and Vascular Biology, Department of Cardiovascular Sciences, Katholieke Universiteit Leuven, 3000 Leuven, Belgium
| | - Jean-Paul Decuypere
- Department of Development and Regeneration, Katholieke Universiteit Leuven, 3000 Leuven, Belgium; (P.M.E.); (O.C.A.); (J.-P.D.); (A.B.N.); (D.M.); (L.P.v.d.H.); (E.N.L.)
| | - Linda Bellucci
- Department of Molecular Biotechnology and Health Sciences, University of Turin, 10124 Turin, Italy; (L.B.); (B.B.)
| | - Mohamed A. Elmonem
- Department of Clinical and Chemical Pathology, Faculty of Medicine, Cairo University, Cairo 11628, Egypt;
| | - Agathe B. Nkoy
- Department of Development and Regeneration, Katholieke Universiteit Leuven, 3000 Leuven, Belgium; (P.M.E.); (O.C.A.); (J.-P.D.); (A.B.N.); (D.M.); (L.P.v.d.H.); (E.N.L.)
- Department of Paediatrics, Division of Nephrology, Faculty of Medicine, University Hospital of Kinshasa, University of Kinshasa, Kinshasa, Democratic Republic of the Congo
| | - Djalila Mekahli
- Department of Development and Regeneration, Katholieke Universiteit Leuven, 3000 Leuven, Belgium; (P.M.E.); (O.C.A.); (J.-P.D.); (A.B.N.); (D.M.); (L.P.v.d.H.); (E.N.L.)
- Department of Paediatrics, Division of Nephrology, University Hospitals Leuven, 3000 Leuven, Belgium
| | - Benedetta Bussolati
- Department of Molecular Biotechnology and Health Sciences, University of Turin, 10124 Turin, Italy; (L.B.); (B.B.)
| | - Lambertus P. van den Heuvel
- Department of Development and Regeneration, Katholieke Universiteit Leuven, 3000 Leuven, Belgium; (P.M.E.); (O.C.A.); (J.-P.D.); (A.B.N.); (D.M.); (L.P.v.d.H.); (E.N.L.)
- Department of Paediatric Nephrology, Radboud University Medical Centre, 6500 Nijmegen, The Netherlands
| | - Fanny O. Arcolino
- Department of Development and Regeneration, Katholieke Universiteit Leuven, 3000 Leuven, Belgium; (P.M.E.); (O.C.A.); (J.-P.D.); (A.B.N.); (D.M.); (L.P.v.d.H.); (E.N.L.)
- Correspondence: ; Tel.: +32-16372647
| | - Elena N. Levtchenko
- Department of Development and Regeneration, Katholieke Universiteit Leuven, 3000 Leuven, Belgium; (P.M.E.); (O.C.A.); (J.-P.D.); (A.B.N.); (D.M.); (L.P.v.d.H.); (E.N.L.)
- Department of Paediatrics, Division of Nephrology, University Hospitals Leuven, 3000 Leuven, Belgium
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8
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Ultsch M, Holliday MJ, Gerhardy S, Moran P, Scales SJ, Gupta N, Oltrabella F, Chiu C, Fairbrother W, Eigenbrot C, Kirchhofer D. Structures of the ApoL1 and ApoL2 N-terminal domains reveal a non-classical four-helix bundle motif. Commun Biol 2021; 4:916. [PMID: 34316015 PMCID: PMC8316464 DOI: 10.1038/s42003-021-02387-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 06/23/2021] [Indexed: 02/07/2023] Open
Abstract
Apolipoprotein L1 (ApoL1) is a circulating innate immunity protein protecting against trypanosome infection. However, two ApoL1 coding variants are associated with a highly increased risk of chronic kidney disease. Here we present X-ray and NMR structures of the N-terminal domain (NTD) of ApoL1 and of its closest relative ApoL2. In both proteins, four of the five NTD helices form a four-helix core structure which is different from the classical four-helix bundle and from the pore-forming domain of colicin A. The reactivity with a conformation-specific antibody and structural models predict that this four-helix motif is also present in the NTDs of ApoL3 and ApoL4, suggesting related functions within the small ApoL family. The long helix 5 of ApoL1 is conformationally flexible and contains the BH3-like region. This BH3-like α-helix resembles true BH3 domains only in sequence and structure but not in function, since it does not bind to the pro-survival members of the Bcl-2 family, suggesting a Bcl-2-independent role in cytotoxicity. These findings should expedite a more comprehensive structural and functional understanding of the ApoL immune protein family.
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Affiliation(s)
- Mark Ultsch
- Department of Structural Biology, Genentech Inc., South San Francisco, CA, USA
| | - Michael J Holliday
- Department of Early Discovery Biochemistry, Genentech Inc., South San Francisco, CA, USA
| | - Stefan Gerhardy
- Department of Early Discovery Biochemistry, Genentech Inc., South San Francisco, CA, USA
| | - Paul Moran
- Department of Early Discovery Biochemistry, Genentech Inc., South San Francisco, CA, USA
| | - Suzie J Scales
- Department of Immunology, Genentech Inc., South San Francisco, CA, USA
| | - Nidhi Gupta
- Department of Immunology, Genentech Inc., South San Francisco, CA, USA
| | | | - Cecilia Chiu
- Department of Antibody Engineering, Genentech Inc., South San Francisco, CA, USA
| | - Wayne Fairbrother
- Department of Early Discovery Biochemistry, Genentech Inc., South San Francisco, CA, USA
| | - Charles Eigenbrot
- Department of Structural Biology, Genentech Inc., South San Francisco, CA, USA
| | - Daniel Kirchhofer
- Department of Early Discovery Biochemistry, Genentech Inc., South San Francisco, CA, USA.
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9
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Abstract
Rates of many types of severe kidney disease are much higher in Black individuals than most other ethnic groups. Much of this disparity can now be attributed to genetic variants in the apoL1 (APOL1) gene found only in individuals with recent African ancestry. These variants greatly increase rates of hypertension-associated ESKD, FSGS, HIV-associated nephropathy, and other forms of nondiabetic kidney disease. We discuss the population genetics of APOL1 risk variants and the clinical spectrum of APOL1 nephropathy. We then consider clinical issues that arise for the practicing nephrologist caring for the patient who may have APOL1 kidney disease.
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Affiliation(s)
- David J Friedman
- Division of Nephrology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
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10
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Giovinazzo JA, Thomson RP, Khalizova N, Zager PJ, Malani N, Rodriguez-Boulan E, Raper J, Schreiner R. Apolipoprotein L-1 renal risk variants form active channels at the plasma membrane driving cytotoxicity. eLife 2020; 9:51185. [PMID: 32427098 PMCID: PMC7292663 DOI: 10.7554/elife.51185] [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: 08/19/2019] [Accepted: 05/14/2020] [Indexed: 12/25/2022] Open
Abstract
Recently evolved alleles of Apolipoprotein L-1 (APOL1) provide increased protection against African trypanosome parasites while also significantly increasing the risk of developing kidney disease in humans. APOL1 protects against trypanosome infections by forming ion channels within the parasite, causing lysis. While the correlation to kidney disease is robust, there is little consensus concerning the underlying disease mechanism. We show in human cells that the APOL1 renal risk variants have a population of active channels at the plasma membrane, which results in an influx of both Na+ and Ca2+. We propose a model wherein APOL1 channel activity is the upstream event causing cell death, and that the activate-state, plasma membrane-localized channel represents the ideal drug target to combat APOL1-mediated kidney disease.
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Affiliation(s)
- Joseph A Giovinazzo
- Department of Biological Sciences, Hunter College at City University of New York, New York, United States
| | - Russell P Thomson
- Department of Biological Sciences, Hunter College at City University of New York, New York, United States
| | - Nailya Khalizova
- Department of Biological Sciences, Hunter College at City University of New York, New York, United States
| | - Patrick J Zager
- Department of Ophthalmology, Margaret Dyson Vision Research Institute, Weill Cornell Medicine, New York, United States
| | | | - Enrique Rodriguez-Boulan
- Department of Ophthalmology, Margaret Dyson Vision Research Institute, Weill Cornell Medicine, New York, United States
| | - Jayne Raper
- Department of Biological Sciences, Hunter College at City University of New York, New York, United States
| | - Ryan Schreiner
- Department of Ophthalmology, Margaret Dyson Vision Research Institute, Weill Cornell Medicine, New York, United States
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11
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Fang J, Yao X, Hou M, Duan M, Xing L, Huang J, Wang Y, Zhu B, Chen Q, Wang H. ApoL1 induces kidney inflammation through RIG-I/NF-κB activation. Biochem Biophys Res Commun 2020; 527:466-473. [PMID: 32336543 DOI: 10.1016/j.bbrc.2020.04.054] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Accepted: 04/11/2020] [Indexed: 02/07/2023]
Abstract
The genetic variations of the apolipoprotein L1 (APOL1) gene are associated with non-diabetic kidney diseases. However, very little is known about the role of ApoL1 in glomerular damage. Here, we aimed to identify the function and mechanism of ApoL1 in glomerular damage. The mice were randomly divided into two groups: one group was intraperitoneally injected with phosphate buffer saline (PBS), while the other group was intraperitoneally injected with recombinant ApoL1 every other day for 3 months. Hematoxylin and eosin (HE) and periodic acid Schiff (PAS) staining were used to demonstrate the effects of ApoL1 on kidney inflammation and injury. Furthermore, quantitative real-time polymerase chain reaction (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA) analyses revealed that ApoL1-treated mice exhibited enhanced expression of various inflammation markers in the kidney and serum compared to the PBS-treated mice. Immunofluorescence staining revealed that ApoL1 accumulated in kidney podocytes. Treatment with ApoL1 dose-dependently increased the expression of inflammation markers and apoptotic markers. The abnormal gene expression associated with ApoL1-mediated podocyte inflammation was evaluated using microarray analysis. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed that the upregulated genes were enriched in the inflammation-related processes, such as the RIG-I/NF-κB signaling pathway. Consistently, the knockdown of RIG-I significantly mitigated the ApoL1-induced upregulation of inflammatory and apoptotic markers in the human podocytes. Additionally, the ApoL1-induced glomerular damage was attenuated in AAV-shRIG-I mice. Therefore, the effects of ApoL1 on glomerular damage may be, at least partially, through inducing abnormal expression of inflammatory molecules, which may have important implications for treatment of kidney diseases.
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Affiliation(s)
- Ji Fang
- Department of Nephrology, Laboratory of Renal Disease, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, 200062, People's Republic of China
| | - Xingmei Yao
- Department of Nephrology, Laboratory of Renal Disease, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, 200062, People's Republic of China
| | - Mingqiang Hou
- Department of Urology, Xishui County People's Hospital, Guizhou Province, Guizhou, 564699, People's Republic of China
| | - Miao Duan
- Department of Urology, Xishui County People's Hospital, Guizhou Province, Guizhou, 564699, People's Republic of China
| | - Lina Xing
- Department of Nephrology, Laboratory of Renal Disease, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, 200062, People's Republic of China
| | - Jiebo Huang
- Department of Nephrology, Laboratory of Renal Disease, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, 200062, People's Republic of China
| | - Yunman Wang
- Department of Nephrology, Laboratory of Renal Disease, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, 200062, People's Republic of China
| | - Bingbing Zhu
- Department of Nephrology, Laboratory of Renal Disease, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, 200062, People's Republic of China
| | - Qiujing Chen
- Institute of Cardiovascular Diseases, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, 200025, People's Republic of China.
| | - Hao Wang
- Department of Nephrology, Laboratory of Renal Disease, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, 200062, People's Republic of China.
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12
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Abstract
Genetic variants in the APOL1 gene, found only in individuals of recent African ancestry, greatly increase risk of multiple types of kidney disease. These APOL1 kidney risk alleles are a rare example of genetic variants that are common but also have a powerful effect on disease susceptibility. These alleles rose to high frequency in sub-Saharan Africa because they conferred protection against pathogenic trypanosomes that cause African sleeping sickness. We consider the genetic evidence supporting the association between APOL1 and kidney disease across the range of clinical phenotypes in the APOL1 nephropathy spectrum. We then explore the origins of the APOL1 risk variants and evolutionary struggle between humans and trypanosomes at both the molecular and population genetic level. Finally, we survey the rapidly growing literature investigating APOL1 biology as elucidated from experiments in cell-based systems, cell-free systems, mouse and lower organism models of disease, and through illuminating natural experiments in humans.
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Affiliation(s)
- David J Friedman
- Division of Nephrology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA; ,
| | - Martin R Pollak
- Division of Nephrology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA; ,
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13
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Abstract
PURPOSE OF REVIEW The purpose of this mini-review is to highlight some unresolved questions and controversies in the evolving story of apolipoprotein L1 (APOL1) nephropathy. RECENT FINDINGS We highlight studies that introduce complexity in unraveling the mechanisms whereby APOL1 risk variant alleles cause disease. These include studies which support a possible protective role for the APOL1 GO nonrisk ancestral allele, and studies which explore the initiating events that may trigger other downstream pathways mediating APOL1 cellular injury. We also review studies that reconcile the perplexing findings regarding APOL1 anionic or cationic conductance, and pH dependency, and also studies that attempt to characterize the 3-dimensional structure of APOL1 C-terminal in APOL1 variants, as well as that of the serum resistance-associated protein. We also attempt to convey new insights from in-vivo and in-vitro models, including studies that do not support the differential toxicity of APOL1 renal risk variants and recapitulate the clinical variability of individuals at genotypic risk. SUMMARY Along with major progress that had been achieved in the field of APOL1 nephropathy, controversies and enigmatic issues persist. It remains to be determined which of the pathways which have been demonstrated to mediate cell injury by ectopically expressed APOL1 risk variants in cellular and organismal models are relevant to human disease and can pave the way to potential therapy.
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14
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Abstract
The apolipoprotein L1 (APOL1) gene is unique to humans and gorillas and appeared ~33 million years ago. Since the majority of the mammals do not carry APOL1, it seems to be dispensable for kidney function. APOL1 renal risk variants (RRVs; G1 and G2) are associated with the development as well as progression of chronic kidney diseases (CKDs) at higher rates in populations with African ancestry. Cellular expression of two APOL1 RRVs has been demonstrated to induce cytotoxicity, including necrosis, apoptosis, and pyroptosis, in several cell types including podocytes; mechanistically, these toxicities were attributed to lysosomal swelling, K+ depletion, mitochondrial dysfunction, autophagy blockade, protein kinase receptor activation, ubiquitin D degradation, and endoplasmic reticulum stress; notably, these effects were found to be dose dependent and occurred only in overtly APOL1 RRV-expressing cells. However, cellular protein expressions as well as circulating blood levels of APOL1 RRVs were not elevated in patients suffering from APOL1 RRV-associated CKDs. Therefore, the question arises as to whether it is gain or loss of function on the part of APOL1 RRVs contributing to kidney cell injury. The question seems to be more pertinent after the recognition of the role of APOL1 nonrisk (G0) in the transition of parietal epithelial cells and preservation of the podocyte molecular phenotype through modulation of the APOL1-miR-193a axis. With this background, the present review analyzed the available literature in terms of the known function of APOL1 nonrisk and how the loss of these functions could have contributed to two APOL1 RRV-associated CKDs.
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Affiliation(s)
- Vinod Kumar
- Institute of Molecular Medicine, Feinstein Institute for Medical Research and Department of Medicine, Zucker School of Medicine at Hofstra-Northwell, Hempstead, New York
| | - Pravin C Singhal
- Institute of Molecular Medicine, Feinstein Institute for Medical Research and Department of Medicine, Zucker School of Medicine at Hofstra-Northwell, Hempstead, New York
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15
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Abstract
Apolipoprotein L1 (APOL1) protein is the human serum factor that protect human beings against Trypanosoma brucei brucei, the cause of trypanosomiasis. Subspecies of T b brucei that cause human sleeping sickness-T b gambiense and T b rhodesiense evolved molecular mechanisms that enabled them to evade killing by APOL1. Sequence changes (termed G1 and G2) in the APOL1 gene that restored its ability to kill T b rhodesiense also increase the risk of developing glomerular diseases and accelerate progression to end-stage kidney disease. To lyse trypanosome parasites, APOL1 forms pores in the trypanosome endolysosomal and mitochondrial membranes, resulting in rapid membrane depolarization. However, the molecular mechanism underlying APOL1 nephropathy is unknown. Recent experimental evidence has shown that aberrant efflux of intracellular potassium is an early event in APOL1-induced death of human embryonic kidney cells. Here, we discuss the possibility that abnormal efflux of cellular potassium or other cations may be relevant to the pathogenesis of APOL1 nephropathy.
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Affiliation(s)
- Opeyemi A Olabisi
- Division of Nephrology, Department of Medicine, Massachusetts General Hospital, Boston, MA; Harvard Medical School, Boston, MA.
| | - John F Heneghan
- Harvard Medical School, Boston, MA; Division of Nephrology, Vascular Biology Research Center, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA; Surgical Immunotherapy at Roger Williams Medical Center, Providence, RI
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16
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Abstract
The association of variants in the APOL1 gene, which encodes apolipoprotein L1 (APOL1), with progressive nondiabetic kidney diseases in African Americans has prompted intense investigation into the function(s) of APOL1. APOL1 is an innate immune effector that protects human beings from infection by some trypanosomal parasites. We review the data characterizing APOL1 trypanolytic function, which has been a basis for studies of APOL1 function in mammalian cells. Subsequently, we discuss the studies that use animal models, mammalian cell culture models, and kidney biopsy tissue to discover the mechanisms of variant APOL1-associated kidney diseases.
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17
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APOL1: The Balance Imposed by Infection, Selection, and Kidney Disease. Trends Mol Med 2018; 24:682-695. [PMID: 29886044 DOI: 10.1016/j.molmed.2018.05.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Revised: 05/07/2018] [Accepted: 05/14/2018] [Indexed: 02/07/2023]
Abstract
Chronic kidney disease (CKD) affects millions of people and constitutes a major health and financial burden worldwide. People of African descent are at an increased risk of developing kidney disease, which is mostly explained by two variants in the Apolipoprotein L1 (APOL1) gene that are found only in people of west African origin. It is hypothesized that these variants were genetically selected due to the protection they afford against African sleeping sickness, caused by the parasite Trypanosoma brucei. Targeting mutant APOL1 could have substantial therapeutic potential for treating kidney disease. In this review, we will describe the intriguing interplay between microbiology, genetics, and kidney disease as revealed in APOL1-associated kidney disease, discuss APOL1-induced cytotoxicity and its therapeutic implications.
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18
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O'Toole JF, Schilling W, Kunze D, Madhavan SM, Konieczkowski M, Gu Y, Luo L, Wu Z, Bruggeman LA, Sedor JR. ApoL1 Overexpression Drives Variant-Independent Cytotoxicity. J Am Soc Nephrol 2017; 29:869-879. [PMID: 29180397 DOI: 10.1681/asn.2016121322] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Accepted: 10/31/2017] [Indexed: 12/16/2022] Open
Abstract
Coding variants in the APOL1 gene are associated with kidney diseases in African ancestral populations; yet, the underlying biologic mechanisms remain uncertain. Variant-dependent autophagic and cytotoxic cell death have been proposed as pathogenic pathways mediating kidney injury. To examine this possibility, we conditionally expressed APOL1-G0 (reference), -G1, and -G2 (variants) using a tetracycline-regulated system in HEK293 cells. Autophagy was monitored biochemically and cell death was measured using multiple assays. We measured intracellular Na+ and K+ content with atomic absorption spectroscopy and APOL1-dependent currents with whole-cell patch clamping. Neither reference nor variant APOL1s induced autophagy. At high expression levels, APOL1-G0, -G1, and -G2 inserted into the plasma membrane and formed pH-sensitive cation channels, causing collapse of cellular Na+ and K+ gradients, phosphorylation of p38 mitogen-activated protein kinase, and cell death, without variant-dependent differences. APOL1-G0 and -G2 exhibited similar channel properties in whole-cell patch clamp experiments. At low expression levels, neither reference nor variant APOL1s localized on the plasma membrane, Na+ and K+ gradients were maintained, and cells remained viable. Our results indicate that APOL1-mediated pore formation is critical for the trypanolytic activity of APOL1 and drives APOL1-mediated cytotoxicity in overexpression systems. The absence of cytotoxicity at physiologic expression levels suggests variant-dependent intracellular K+ loss and cytotoxicity does not drive kidney disease progression.
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Affiliation(s)
- John F O'Toole
- Department of Nephrology and Hypertension, Glickman Urological and Kidney Institute, Cleveland Clinic, Cleveland, Ohio.,Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio.,Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, Ohio; and
| | - William Schilling
- Rammelkamp Center, MetroHealth System.,Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio
| | | | | | | | - Yaping Gu
- Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio
| | - Liping Luo
- Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio
| | - Zhenzhen Wu
- Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio
| | - Leslie A Bruggeman
- Department of Nephrology and Hypertension, Glickman Urological and Kidney Institute, Cleveland Clinic, Cleveland, Ohio.,Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio.,Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, Ohio; and
| | - John R Sedor
- Department of Nephrology and Hypertension, Glickman Urological and Kidney Institute, Cleveland Clinic, Cleveland, Ohio.,Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio.,Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, Ohio; and.,Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio
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19
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Kruzel-Davila E, Wasser WG, Skorecki K. APOL1 Nephropathy: A Population Genetics and Evolutionary Medicine Detective Story. Semin Nephrol 2017; 37:490-507. [PMID: 29110756 DOI: 10.1016/j.semnephrol.2017.07.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Common DNA sequence variants rarely have a high-risk association with a common disease. When such associations do occur, evolutionary forces must be sought, such as in the association of apolipoprotein L1 (APOL1) gene risk variants with nondiabetic kidney diseases in populations of African ancestry. The variants originated in West Africa and provided pathogenic resistance in the heterozygous state that led to high allele frequencies owing to an adaptive evolutionary selective sweep. However, the homozygous state is disadvantageous and is associated with a markedly increased risk of a spectrum of kidney diseases encompassing hypertension-attributed kidney disease, focal segmental glomerulosclerosis, human immunodeficiency virus nephropathy, sickle cell nephropathy, and progressive lupus nephritis. This scientific success story emerged with the help of the tools developed over the past 2 decades in human genome sequencing and population genomic databases. In this introductory article to a timely issue dedicated to illuminating progress in this area, we describe this unique population genetics and evolutionary medicine detective story. We emphasize the paradox of the inheritance mode, the missing heritability, and unresolved associations, including cardiovascular risk and diabetic nephropathy. We also highlight how genetic epidemiology elucidates mechanisms and how the principles of evolution can be used to unravel conserved pathways affected by APOL1 that may lead to novel therapies. The APOL1 gene provides a compelling example of a common variant association with common forms of nondiabetic kidney disease occurring in a continental population isolate with subsequent global admixture. Scientific collaboration using multiple experimental model systems and approaches should further clarify pathomechanisms further, leading to novel therapies.
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Affiliation(s)
| | - Walter G Wasser
- Department of Nephrology, Rambam Health Care Campus, Haifa, Israel; Department of Nephrology, Mayanei HaYeshua Medical Center, Bnei Brak, Israel
| | - Karl Skorecki
- Department of Nephrology, Rambam Health Care Campus, Haifa, Israel; Department of Genetics and Developmental Biology, Rappaport Faculty of Medicine and Research Institute Technion-Israel Institute of Technology, Rambam Health Care Campus, Haifa, Israel.
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20
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O’Toole JF, Bruggeman LA, Sedor JR. A New Mouse Model of APOL1 -Associated Kidney Diseases: When Traffic Gets Snarled, the Podocyte Suffers. Am J Kidney Dis 2017; 70:460-463. [DOI: 10.1053/j.ajkd.2017.07.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Accepted: 07/12/2017] [Indexed: 01/05/2023]
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21
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Peng T, Wang L, Li G. The analysis of APOL1 genetic variation and haplotype diversity provided by 1000 Genomes project. BMC Nephrol 2017; 18:267. [PMID: 28800731 PMCID: PMC5553676 DOI: 10.1186/s12882-017-0675-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Accepted: 07/19/2017] [Indexed: 11/20/2022] Open
Abstract
Background The APOL1 gene variants has been shown to be associated with an increased risk of multiple kinds of diseases, particularly in African Americans, but not in Caucasians and Asians. In this study, we explored the single nucleotide polymorphism (SNP) and haplotype diversity of APOL1 gene in different races provided by 1000 Genomes project. Methods Variants of APOL1 gene in 1000 Genome Project were obtained and SNPs located in the regulatory region or coding region were selected for genetic variation analysis. Total 2504 individuals from 26 populations were classified as four groups that included Africa, Europe, Asia and Admixed populations. Tag SNPs were selected to evaluate the haplotype diversities in the four populations by HaploStats software. Results APOL1 gene was surrounded by some of the most polymorphic genes in the human genome, variation of APOL1 gene was common, with up to 613 SNP (1000 Genome Project reported) and 99 of them (16.2%) with MAF ≥ 1%. There were 79 SNPs in the URR and 92 SNPs in 3’UTR. Total 12 SNPs in URR and 24 SNPs in 3’UTR were considered as common variants with MAF ≥ 1%. It is worth noting that URR-1 was presents lower frequencies in European populations, while other three haplotypes taken an opposite pattern; 3’UTR presents several high-frequency variation sites in a short segment, and the differences of its haplotypes among different population were significant (P < 0.01), UTR-1 and UTR-5 presented much higher frequency in African population, while UTR-2, UTR-3 and UTR-4 were much lower. APOL1 coding region showed that two SNP of G1 with higher frequency are actually pull down the haplotype H-1 frequency when considering all populations pooled together, and the diversity among the four populations be widen by the G1 two mutation (P1 = 3.33E-4 vs P2 = 3.61E-30). Conclusions The distributions of APOL1 gene variants and haplotypes were significantly different among the different populations, in either regulatory or coding regions. It could provide clues for the future genetic study of APOL1 related diseases. Electronic supplementary material The online version of this article (doi:10.1186/s12882-017-0675-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Ting Peng
- Renal Division and Institute of Nephrology, Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, No. 32, West 2nd Duan, 1st Circle Road, Qingyang District, Chengdu, Sichuan, People's Republic of China, 610072
| | - Li Wang
- Renal Division and Institute of Nephrology, Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, No. 32, West 2nd Duan, 1st Circle Road, Qingyang District, Chengdu, Sichuan, People's Republic of China, 610072
| | - Guisen Li
- Renal Division and Institute of Nephrology, Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, No. 32, West 2nd Duan, 1st Circle Road, Qingyang District, Chengdu, Sichuan, People's Republic of China, 610072.
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22
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Abstract
PURPOSE OF REVIEW Systemic lupus erythematosus (SLE) confers up to a 50-fold increased risk of cardiovascular disease (CVD), and African Americans with SLE experience accelerated damage accrual and doubled cardiovascular risk when compared to their European American counterparts. RECENT FINDINGS Genome-wide association studies have identified a substantial signal at 22q13, now assigned to variation at apolipoprotein L1 (APOL1), which has associated with progressive nondiabetic nephropathy, cardiovascular disease, and many immune-associated renal diseases, including lupus nephritis. We contend that alterations in crucial APOL1 intracellular pathways may underpin associated disease states based on structure-functional differences between variant and ancestral forms. While ancestral APOL1 may be a key driver of autophagy, nonconserved primary structure changes result in a toxic gain of function with attenuation of autophagy and an unsupervised pore-forming feature. Thus, the divergent intracellular biological pathways of ancestral and variant APOL1 may explain a worsened prognosis as demonstrated in SLE.
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23
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Beckerman P, Bi-Karchin J, Park ASD, Qiu C, Dummer PD, Soomro I, Boustany-Kari CM, Pullen SS, Miner JH, Hu CAA, Rohacs T, Inoue K, Ishibe S, Saleem MA, Palmer MB, Cuervo AM, Kopp JB, Susztak K. Transgenic expression of human APOL1 risk variants in podocytes induces kidney disease in mice. Nat Med 2017; 23:429-438. [PMID: 28218918 DOI: 10.1038/nm.4287] [Citation(s) in RCA: 250] [Impact Index Per Article: 35.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 01/20/2017] [Indexed: 02/07/2023]
Abstract
African Americans have a heightened risk of developing chronic and end-stage kidney disease, an association that is largely attributed to two common genetic variants, termed G1 and G2, in the APOL1 gene. Direct evidence demonstrating that these APOL1 risk alleles are pathogenic is still lacking because the APOL1 gene is present in only some primates and humans; thus it has been challenging to demonstrate experimental proof of causality of these risk alleles for renal disease. Here we generated mice with podocyte-specific inducible expression of the APOL1 reference allele (termed G0) or each of the risk-conferring alleles (G1 or G2). We show that mice with podocyte-specific expression of either APOL1 risk allele, but not of the G0 allele, develop functional (albuminuria and azotemia), structural (foot-process effacement and glomerulosclerosis) and molecular (gene-expression) changes that closely resemble human kidney disease. Disease development was cell-type specific and likely reversible, and the severity correlated with the level of expression of the risk allele. We further found that expression of the risk-variant APOL1 alleles interferes with endosomal trafficking and blocks autophagic flux, which ultimately leads to inflammatory-mediated podocyte death and glomerular scarring. In summary, this is the first demonstration that the expression of APOL1 risk alleles is causal for altered podocyte function and glomerular disease in vivo.
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Affiliation(s)
- Pazit Beckerman
- Renal Electrolyte and Hypertension Division, Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Jing Bi-Karchin
- Renal Electrolyte and Hypertension Division, Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Ae Seo Deok Park
- Renal Electrolyte and Hypertension Division, Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Chengxiang Qiu
- Renal Electrolyte and Hypertension Division, Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Patrick D Dummer
- Kidney Disease Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Irfana Soomro
- Division of Nephrology, New York University, New York, New York, USA
| | - Carine M Boustany-Kari
- Department of Cardiometabolic Diseases Research, Boehringer Ingelheim Pharmaceuticals, Ridgefield, Connecticut, USA
| | - Steven S Pullen
- Department of Cardiometabolic Diseases Research, Boehringer Ingelheim Pharmaceuticals, Ridgefield, Connecticut, USA
| | - Jeffrey H Miner
- Division of Nephrology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Chien-An A Hu
- Department of Biochemistry and Molecular Biology, University of New Mexico School of Medicine and Health Sciences Center, Albuquerque, New Mexico, USA
| | - Tibor Rohacs
- Department of Pharmacology, Physiology &Neuroscience, Rutgers-New Jersey Medical School, Newark, New Jersey, USA
| | - Kazunori Inoue
- Division of Nephrology, Yale University, School of Medicine, New Haven, Connecticut, USA
| | - Shuta Ishibe
- Division of Nephrology, Yale University, School of Medicine, New Haven, Connecticut, USA
| | - Moin A Saleem
- Bristol Renal and Children's Renal Unit, School of Clinical Sciences, University of Bristol, Bristol, UK
| | - Matthew B Palmer
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Ana Maria Cuervo
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, New York, New York, USA
| | - Jeffrey B Kopp
- Kidney Disease Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Katalin Susztak
- Renal Electrolyte and Hypertension Division, Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.,Department of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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24
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Shukha K, Mueller JL, Chung RT, Curry MP, Friedman DJ, Pollak MR, Berg AH. Most ApoL1 Is Secreted by the Liver. J Am Soc Nephrol 2016; 28:1079-1083. [PMID: 27932478 DOI: 10.1681/asn.2016040441] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2016] [Accepted: 09/18/2016] [Indexed: 01/09/2023] Open
Abstract
Two coding sequence variants in the APOL1 gene (G1 and G2) explain much of the increased risk for FSGS, HIV-associated nephropathy, and hypertension-attributed ESRD among people of recent African ancestry. The ApoL1 protein is expressed in a wide variety of cell tissues. It has been assumed that the majority of circulating ApoL1 is produced by the liver, but this has not been shown. Using mass spectrometry, we genotyped and quantified the circulating ApoL1 in two liver transplant recipients whose native APOL1 genotype differed from the genotype of the deceased donors, allowing us to differentiate liver- from nonliver-produced ApoL1. Our findings confirm that the liver is indeed the main source of circulating ApoL1. However, the liver is not the sole source of circulating ApoL1, because we found that residual amounts of native ApoL1 continued to circulate in the blood, even after the liver transplant.
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Affiliation(s)
- Khuloud Shukha
- Division of Nephrology, Department of Medicine and.,Harvard Medical School, Boston, Massachusetts
| | - Jessica L Mueller
- Harvard Medical School, Boston, Massachusetts.,Division of Gastroenterology, Department of Medicine, Massachusetts General Hospital, Boston, Massachusetts; and
| | - Raymond T Chung
- Harvard Medical School, Boston, Massachusetts.,Division of Gastroenterology, Department of Medicine, Massachusetts General Hospital, Boston, Massachusetts; and
| | - Michael P Curry
- Harvard Medical School, Boston, Massachusetts.,Division of Gastroenterology, Department of Medicine, Beth Israel Deaconess Medical Center
| | - David J Friedman
- Division of Nephrology, Department of Medicine and.,Harvard Medical School, Boston, Massachusetts
| | - Martin R Pollak
- Division of Nephrology, Department of Medicine and .,Harvard Medical School, Boston, Massachusetts
| | - Anders H Berg
- Harvard Medical School, Boston, Massachusetts.,Department of Pathology, Beth Israel Deaconess Medical Center, Boston, Massachusetts
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25
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Kruzel-Davila E, Shemer R, Ofir A, Bavli-Kertselli I, Darlyuk-Saadon I, Oren-Giladi P, Wasser WG, Magen D, Zaknoun E, Schuldiner M, Salzberg A, Kornitzer D, Marelja Z, Simons M, Skorecki K. APOL1-Mediated Cell Injury Involves Disruption of Conserved Trafficking Processes. J Am Soc Nephrol 2016; 28:1117-1130. [PMID: 27864431 DOI: 10.1681/asn.2016050546] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 10/05/2016] [Indexed: 01/08/2023] Open
Abstract
APOL1 harbors C-terminal sequence variants (G1 and G2), which account for much of the increased risk for kidney disease in sub-Saharan African ancestry populations. Expression of the risk variants has also been shown to cause injury to podocytes and other cell types, but the underlying mechanisms are not understood. We used Drosophila melanogaster and Saccharomyces cerevisiae to help clarify these mechanisms. Ubiquitous expression of the human APOL1 G1 and G2 disease risk alleles caused near-complete lethality in D. melanogaster, with no effect of the G0 nonrisk APOL1 allele, corresponding to the pattern of human disease risk. We also observed a congruent pattern of cellular damage with tissue-specific expression of APOL1. In particular, expression of APOL1 risk variants in D. melanogaster nephrocytes caused cell-autonomous accumulation of the endocytic tracer atrial natriuretic factor-red fluorescent protein at early stages and nephrocyte loss at later stages. We also observed differential toxicity of the APOL1 risk variants compared with the APOL1 nonrisk variants in S. cerevisiae, including impairment of vacuole acidification. Yeast strains defective in endosomal trafficking or organelle acidification but not those defective in autophagy displayed augmented APOL1 toxicity with all isoforms. This pattern of differential injury by the APOL1 risk alleles compared with the nonrisk alleles across evolutionarily divergent species is consistent with an impairment of conserved core intracellular endosomal trafficking processes. This finding should facilitate the identification of cell injury pathways and corresponding therapeutic targets of interest in these amenable experimental platforms.
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Affiliation(s)
- Etty Kruzel-Davila
- Department of Nephrology, Rambam Health Care Campus, Haifa, Israel; Departments of
| | | | - Ayala Ofir
- Department of Nephrology, Rambam Health Care Campus, Haifa, Israel; Departments of
| | - Ira Bavli-Kertselli
- Department of Nephrology, Rambam Health Care Campus, Haifa, Israel; Departments of
| | | | - Pazit Oren-Giladi
- Department of Nephrology, Rambam Health Care Campus, Haifa, Israel; Departments of
| | - Walter G Wasser
- Department of Nephrology, Rambam Health Care Campus, Haifa, Israel; Departments of.,Department of Nephrology, Mayanei HaYeshua Medical Center, Bnei Brak, Israel
| | - Daniella Magen
- Department of Nephrology, Rambam Health Care Campus, Haifa, Israel; Departments of.,Genetics and Developmental Biology and
| | | | - Maya Schuldiner
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel; and
| | | | - Daniel Kornitzer
- Microbiology and Inflammation, Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa, Israel
| | - Zvonimir Marelja
- Imagine Institute, Paris Descartes University-Sorbonne Paris Cité, Paris, France
| | - Matias Simons
- Imagine Institute, Paris Descartes University-Sorbonne Paris Cité, Paris, France
| | - Karl Skorecki
- Department of Nephrology, Rambam Health Care Campus, Haifa, Israel; Departments of .,Genetics and Developmental Biology and
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26
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Dummer PD, Limou S, Rosenberg AZ, Heymann J, Nelson G, Winkler CA, Kopp JB. APOL1 Kidney Disease Risk Variants: An Evolving Landscape. Semin Nephrol 2016. [PMID: 26215860 DOI: 10.1016/j.semnephrol.2015.04.008] [Citation(s) in RCA: 107] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Apolipoprotein L1 (APOL1) genetic variants account for much of the excess risk of chronic and end-stage kidney disease, which results in a significant global health disparity for persons of African ancestry. We estimate the lifetime risk of kidney disease in APOL1 dual-risk allele individuals to be at least 15%. Experimental evidence suggests a direct role of APOL1 in pore formation, cellular injury, and programmed cell death in renal injury. The APOL1 BH3 motif, often associated with cell death, is unlikely to play a role in APOL1-induced cytotoxicity because it is not conserved within the APOL family and is dispensable for cell death in vitro. We discuss two models for APOL1 trypanolytic activity: one involving lysosome permeabilization and another involving colloid-osmotic swelling of the cell body, as well as their relevance to human pathophysiology. Experimental evidence from human cell culture models suggests that both mechanisms may be operative. A systems biology approach whereby APOL1-associated perturbations in gene and protein expression in affected individuals are correlated with molecular pathways may be productive to elucidate APOL1 function in vivo.
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Affiliation(s)
- Patrick D Dummer
- Kidney Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD
| | - Sophie Limou
- Molecular Epidemiology Genetics Section, Center for Cancer Research, National Cancer Institute, Frederick MD
| | - Avi Z Rosenberg
- Kidney Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD; Department of Pathology Johns Hopkins University, Baltimore, MD
| | - Jurgen Heymann
- Kidney Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD
| | - George Nelson
- Molecular Epidemiology Genetics Section, Center for Cancer Research, National Cancer Institute, Frederick MD
| | - Cheryl A Winkler
- Molecular Epidemiology Genetics Section, Center for Cancer Research, National Cancer Institute, Frederick MD
| | - Jeffrey B Kopp
- Kidney Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD.
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27
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Friedman DJ, Pollak MR. Apolipoprotein L1 and Kidney Disease in African Americans. Trends Endocrinol Metab 2016; 27:204-215. [PMID: 26947522 PMCID: PMC4811340 DOI: 10.1016/j.tem.2016.02.002] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Revised: 02/05/2016] [Accepted: 02/08/2016] [Indexed: 02/06/2023]
Abstract
Genetic variants in the Apolipoprotein L1 (APOL1) gene cause high rates of kidney disease in African Americans. These variants, found only in individuals with recent African ancestry, confer enhanced innate immunity against African trypanosomes. Although they are among the most powerful disease-causing common variants discovered to date, we are just beginning to understand how they promote kidney injury. Since APOL1 is present in only a few primate species, much of our current knowledge has come from natural experiments in humans and in vitro studies while awaiting the development of transgenic animal models. Understanding more about the function of ApoL1 and how the high-risk variants behave differently from other ApoL1 molecules is a high priority in kidney disease research.
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Affiliation(s)
- David J. Friedman
- Beth Israel Deaconess Medical Center, Harvard Medical School, 99 Brookline Avenue, RN301, Boston, MA. 02215, 617 667 0253
| | - Martin R. Pollak
- Beth Israel Deaconess Medical Center, Harvard Medical School, 99 Brookline Avenue, RN325E, Boston, MA. 02215, 617 667 0461
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28
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Sharma AK, Friedman DJ, Pollak MR, Alper SL. Structural characterization of the C-terminal coiled-coil domains of wild-type and kidney disease-associated mutants of apolipoprotein L1. FEBS J 2016; 283:1846-62. [PMID: 26945671 DOI: 10.1111/febs.13706] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2015] [Revised: 01/25/2016] [Accepted: 03/02/2016] [Indexed: 01/08/2023]
Abstract
Trypanosomes that cause sleeping sickness endocytose apolipoprotein L1 (APOL1)-containing trypanolytic factors from human serum, leading to trypanolytic death through generation of APOL1-associated lytic pores in trypanosomal membranes. The trypanosome Trypanosoma brucei rhodesiense counteracts trypanolysis by expressing the surface protein serum response-associated (SRA), which can bind APOL1 common variant G0 to block its trypanolytic activity. However, two missense variants in the C terminal predicted coiled-coil (CC) domains of human APOL1 G1 (S342G/I384M) and G2 (ΔN388Y389) decrease or abrogate APOL1 binding to T. brucei rhodesiense SRA, thus preserving APOL1 trypanolytic activity. These evolutionarily selected APOL1 missense variants, found at a high frequency in some populations of African descent, also confer elevated risk of kidney disease. Understanding the SRA-APOL1 interaction and the role of APOL1 G1 and G2 variants in kidney disease demands structural characterization of the APOL1 CC domain. Using CD, heteronuclear NMR, and molecular dynamics (MD) simulation on structural homology models, we report here unique and dynamic solution conformations of nephropathy variants G1 and G2 as compared with the common variant G0. Conformational plasticity in G1 and G2 CC domains led to interhelical α1-α2 approximation coupled with secondary structural changes and delimited motional properties absent in the G0 CC domain. The G1 substitutions conferred local structural changes principally along helix α1, whereas the G2 deletion altered the structure of both helix α2 and helix α1. These dynamic features of APOL1 CC variants likely reflect their intrinsic structural properties, and should help interpret future APOL1 structural studies and define the contribution of APOL1 risk variants to kidney disease.
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Affiliation(s)
- Alok K Sharma
- Nephrology Division, Harvard Medical School, Boston, MA, USA.,Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.,Department of Medicine, Harvard Medical School, Boston, MA, USA
| | - David J Friedman
- Nephrology Division, Harvard Medical School, Boston, MA, USA.,Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.,Department of Medicine, Harvard Medical School, Boston, MA, USA
| | - Martin R Pollak
- Nephrology Division, Harvard Medical School, Boston, MA, USA.,Department of Medicine, Harvard Medical School, Boston, MA, USA
| | - Seth L Alper
- Nephrology Division, Harvard Medical School, Boston, MA, USA.,Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.,Department of Medicine, Harvard Medical School, Boston, MA, USA
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29
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Bruggeman LA, Wu Z, Luo L, Madhavan SM, Konieczkowski M, Drawz PE, Thomas DB, Barisoni L, Sedor JR, O'Toole JF. APOL1-G0 or APOL1-G2 Transgenic Models Develop Preeclampsia but Not Kidney Disease. J Am Soc Nephrol 2016; 27:3600-3610. [PMID: 27026370 DOI: 10.1681/asn.2015111220] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Accepted: 02/15/2016] [Indexed: 11/03/2022] Open
Abstract
APOL1 risk variants are associated with kidney disease in blacks, but the mechanisms of renal injury associated with APOL1 risk variants are unknown. Because APOL1 is unique to humans and some primates, we created transgenic (Tg) mice using the promoter of nephrin-encoding Nphs1 to express the APOL1 reference sequence (G0) or the G2 risk variant in podocytes, establishing Tg lines with a spectrum of APOL1 expression levels. Podocytes from Tg-G0 and Tg-G2 mice did not undergo necrosis, apoptosis, or autophagic cell death in vivo, even in lines with highly expressed transgenes. Further, Tg-G0 and Tg-G2 mice did not develop kidney pathology, proteinuria, or azotemia as of 300 days of age. However, by 200 days of age, Tg-G2 mice had significantly lower podocyte density than age-matched WT and Tg-G0 mice had, a difference that was not evident at weaning. Notably, a pregnancy-associated phenotype that encompassed eclampsia, preeclampsia, fetal/neonatal deaths, and small litter sizes occurred in some Tg-G0 mice and more severely in Tg-G2 mice. Similar to human placenta, placentas of Tg mice expressed APOL1. Overall, these results suggest podocyte depletion could predispose individuals with APOL1 risk genotypes to kidney disease in response to a second stressor, and add to other published evidence associating APOL1 expression with preeclampsia.
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Affiliation(s)
- Leslie A Bruggeman
- Division of Nephrology, Department of Medicine, MetroHealth Medical Center and
| | - Zhenzhen Wu
- Division of Nephrology, Department of Medicine, MetroHealth Medical Center and
| | - Liping Luo
- Division of Nephrology, Department of Medicine, MetroHealth Medical Center and
| | - Sethu M Madhavan
- Division of Nephrology, Department of Medicine, MetroHealth Medical Center and
| | | | - Paul E Drawz
- Department of Medicine, University of Minnesota, Minneapolis, Minnesota; and
| | - David B Thomas
- Department of Pathology, University of Miami, Miami, Florida
| | - Laura Barisoni
- Department of Pathology, University of Miami, Miami, Florida
| | - John R Sedor
- Division of Nephrology, Department of Medicine, MetroHealth Medical Center and.,Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - John F O'Toole
- Division of Nephrology, Department of Medicine, MetroHealth Medical Center and
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30
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Wahl P, Ducasa GM, Fornoni A. Systemic and renal lipids in kidney disease development and progression. Am J Physiol Renal Physiol 2016; 310:F433-45. [PMID: 26697982 PMCID: PMC4971889 DOI: 10.1152/ajprenal.00375.2015] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Accepted: 12/22/2015] [Indexed: 12/14/2022] Open
Abstract
Altered lipid metabolism characterizes proteinuria and chronic kidney diseases. While it is thought that dyslipidemia is a consequence of kidney disease, a large body of clinical and experimental studies support that altered lipid metabolism may contribute to the pathogenesis and progression of kidney disease. In fact, accumulation of renal lipids has been observed in several conditions of genetic and nongenetic origins, linking local fat to the pathogenesis of kidney disease. Statins, which target cholesterol synthesis, have not been proven beneficial to slow the progression of chronic kidney disease. Therefore, other therapeutic strategies to reduce cholesterol accumulation in peripheral organs, such as the kidney, warrant further investigation. Recent advances in the understanding of the biology of high-density lipoprotein (HDL) have revealed that functional HDL, rather than total HDL per se, may protect from both cardiovascular and kidney diseases, strongly supporting a role for altered cholesterol efflux in the pathogenesis of kidney disease. Although the underlying pathophysiological mechanisms responsible for lipid-induced renal damage have yet to be uncovered, several studies suggest novel mechanisms by which cholesterol, free fatty acids, and sphingolipids may affect glomerular and tubular cell function. This review will focus on the clinical and experimental evidence supporting a causative role of lipids in the pathogenesis of proteinuria and kidney disease, with a primary focus on podocytes.
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Affiliation(s)
- Patricia Wahl
- Peggy and Harold Katz Family Drug Discovery Center and Division of Nephrology and Hypertension, University of Miami Miller School of Medicine, Miami, Florida
| | - Gloria Michelle Ducasa
- Peggy and Harold Katz Family Drug Discovery Center and Division of Nephrology and Hypertension, University of Miami Miller School of Medicine, Miami, Florida
| | - Alessia Fornoni
- Peggy and Harold Katz Family Drug Discovery Center and Division of Nephrology and Hypertension, University of Miami Miller School of Medicine, Miami, Florida
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31
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Olabisi OA, Zhang JY, VerPlank L, Zahler N, DiBartolo S, Heneghan JF, Schlöndorff JS, Suh JH, Yan P, Alper SL, Friedman DJ, Pollak MR. APOL1 kidney disease risk variants cause cytotoxicity by depleting cellular potassium and inducing stress-activated protein kinases. Proc Natl Acad Sci U S A 2016; 113:830-7. [PMID: 26699492 PMCID: PMC4743809 DOI: 10.1073/pnas.1522913113] [Citation(s) in RCA: 150] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Two specific genetic variants of the apolipoprotein L1 (APOL1) gene are responsible for the high rate of kidney disease in people of recent African ancestry. Expression in cultured cells of these APOL1 risk variants, commonly referred to as G1 and G2, results in significant cytotoxicity. The underlying mechanism of this cytotoxicity is poorly understood. We hypothesized that this cytotoxicity is mediated by APOL1 risk variant-induced dysregulation of intracellular signaling relevant for cell survival. To test this hypothesis, we conditionally expressed WT human APOL1 (G0), the APOL1 G1 variant, or the APOL1 G2 variant in human embryonic kidney cells (T-REx-293) using a tetracycline-mediated (Tet-On) system. We found that expression of either G1 or G2 APOL1 variants increased apparent cell swelling and cell death compared with G0-expressing cells. These manifestations of cytotoxicity were preceded by G1 or G2 APOL1-induced net efflux of intracellular potassium as measured by X-ray fluorescence, resulting in the activation of stress-activated protein kinases (SAPKs), p38 MAPK, and JNK. Prevention of net K(+) efflux inhibited activation of these SAPKs by APOL1 G1 or G2. Furthermore, inhibition of SAPK signaling and inhibition of net K(+) efflux abrogated cytotoxicity associated with expression of APOL1 risk variants. These findings in cell culture raise the possibility that nephrotoxicity of APOL1 risk variants may be mediated by APOL1 risk variant-induced net loss of intracellular K(+) and subsequent induction of stress-activated protein kinase pathways.
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Affiliation(s)
- Opeyemi A Olabisi
- Division of Nephrology, Department of Medicine, Massachusetts General Hospital, Boston, MA 02114; Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215; Harvard Medical School, Boston, MA 02215
| | - Jia-Yue Zhang
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215; Harvard Medical School, Boston, MA 02215
| | | | | | - Salvatore DiBartolo
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215
| | - John F Heneghan
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215; Harvard Medical School, Boston, MA 02215; Vascular Biology Research Center, Beth Israel Deaconess Medical Center, Boston, MA 02215
| | - Johannes S Schlöndorff
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215; Harvard Medical School, Boston, MA 02215
| | - Jung Hee Suh
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215; Harvard Medical School, Boston, MA 02215
| | - Paul Yan
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215; Harvard Medical School, Boston, MA 02215
| | - Seth L Alper
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215; Harvard Medical School, Boston, MA 02215; Vascular Biology Research Center, Beth Israel Deaconess Medical Center, Boston, MA 02215
| | - David J Friedman
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215; Harvard Medical School, Boston, MA 02215; Vascular Biology Research Center, Beth Israel Deaconess Medical Center, Boston, MA 02215
| | - Martin R Pollak
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215; Harvard Medical School, Boston, MA 02215;
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32
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33
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Lan X, Wen H, Lederman R, Malhotra A, Mikulak J, Popik W, Skorecki K, Singhal PC. Protein domains of APOL1 and its risk variants. Exp Mol Pathol 2015; 99:139-44. [PMID: 26091559 PMCID: PMC4509982 DOI: 10.1016/j.yexmp.2015.06.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Accepted: 06/09/2015] [Indexed: 11/24/2022]
Abstract
Increasing lines of evidence have demonstrated that the development of higher rates of non-diabetic glomerulosclerosis (GS) in African Americans can be attributed to two coding sequence variants (G1 and G2) in the Apolipoprotein L1 (APOL) gene. Recent studies indicate that the gene products of these APOL1 risk variants have augmented toxicity to kidney cells. However, the biological characteristics of APOL1 and its risk variants are not well elucidated. The APOL1 protein can be divided into several functional domains, including signal peptide (SP), pore forming domain (PFD), membrane address domain (MAD), and SRA-interacting domain. To investigate the relative contribution of each domain to cell injury, we constructed a serial expression vectors to delete or express each domain. These vectors were transfected into the human embryonic kidney cell line 293T, and then compared the cytotoxicity. In addition, we conducted studies in which APOL1 wild type (G0) was co-transfected in combination with G1 or G2 to see whether G0 could counteract the toxicity of the risk variants. The results showed that deleting the SP did not abolish the toxicity of APOL1, though deletion of 26 amino acid residues of the mature peptide at the N-terminal partially decreased the toxicity. Deleting PFD or MAD or SRA-interacting domain abolished toxicity, while, overexpressing each domain alone could not cause toxicity to the host cells. Deletion of the G2 sites while retaining G1 sites in the risk state resulted in persistent toxicity. Either deletion or exchanging the BH3 domain in the PFD led to complete loss of the toxicity in this experimental platform. Adding G0 to either G1 or G2 did not attenuate the toxicity of the either moiety. These results indicate that the integrity of the mature APOL1 protein is indispensable for its toxicity. Our study not only reveals the contribution of each domain of the APOL1 protein to cell injury, but also highlights some potential suggested targets for drug design to prevent or treat APOL1-associated nephropathy.
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Affiliation(s)
- Xiqian Lan
- Renal Molecular Research Laboratory, Feinstein Institute for Medical Research, Hofstra North Shore LIJ Medical School, NY, United States.
| | - Hongxiu Wen
- Renal Molecular Research Laboratory, Feinstein Institute for Medical Research, Hofstra North Shore LIJ Medical School, NY, United States
| | - Rivka Lederman
- Renal Molecular Research Laboratory, Feinstein Institute for Medical Research, Hofstra North Shore LIJ Medical School, NY, United States
| | - Ashwani Malhotra
- Renal Molecular Research Laboratory, Feinstein Institute for Medical Research, Hofstra North Shore LIJ Medical School, NY, United States
| | | | | | - Karl Skorecki
- Nephrology and Molecular Medicine, Technion Institute of Technology and Rambam Medical Center, Haifa, Israel
| | - Pravin C Singhal
- Renal Molecular Research Laboratory, Feinstein Institute for Medical Research, Hofstra North Shore LIJ Medical School, NY, United States.
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