1
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Greenberg D, Rosenblum ND, Tonelli M. The multifaceted links between hearing loss and chronic kidney disease. Nat Rev Nephrol 2024; 20:295-312. [PMID: 38287134 DOI: 10.1038/s41581-024-00808-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/04/2024] [Indexed: 01/31/2024]
Abstract
Hearing loss affects nearly 1.6 billion people and is the third-leading cause of disability worldwide. Chronic kidney disease (CKD) is also a common condition that is associated with adverse clinical outcomes and high health-care costs. From a developmental perspective, the structures responsible for hearing have a common morphogenetic origin with the kidney, and genetic abnormalities that cause familial forms of hearing loss can also lead to kidney disease. On a cellular level, normal kidney and cochlea function both depend on cilial activities at the apical surface, and kidney tubular cells and sensory epithelial cells of the inner ear use similar transport mechanisms to modify luminal fluid. The two organs also share the same collagen IV basement membrane network. Thus, strong developmental and physiological links exist between hearing and kidney function. These theoretical considerations are supported by epidemiological data demonstrating that CKD is associated with a graded and independent excess risk of sensorineural hearing loss. In addition to developmental and physiological links between kidney and cochlear function, hearing loss in patients with CKD may be driven by specific medications or treatments, including haemodialysis. The associations between these two common conditions are not commonly appreciated, yet have important implications for research and clinical practice.
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Affiliation(s)
- Dina Greenberg
- Program in Developmental and Stem Cell Biology, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Laboratory Medicine and Pathobiology, Temerty Faculty of Medicine, Toronto, Ontario, Canada
| | - Norman D Rosenblum
- Program in Developmental and Stem Cell Biology, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Laboratory Medicine and Pathobiology, Temerty Faculty of Medicine, Toronto, Ontario, Canada
- Department of Paediatrics, Temerty Faculty of Medicine, Toronto, Ontario, Canada
| | - Marcello Tonelli
- Department of Medicine, University of Calgary, Calgary, Alberta, Canada.
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2
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Jiang J, Li T, Wang E, Zhang Y, Han J, Tan L, Li X, Fan Y, Wu Y, Chen Q, Jin J. Polybrominated diphenyl ethers in dust, hair and urine: Exposure, excretion. CHEMOSPHERE 2024; 352:141380. [PMID: 38368958 DOI: 10.1016/j.chemosphere.2024.141380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Revised: 01/21/2024] [Accepted: 02/02/2024] [Indexed: 02/20/2024]
Abstract
Polybrominated diphenyl ethers (PBDEs) have been detected in various environmental media and human tissues. PBDEs concentrations in dust from college buildings and homes and in paired hair and urine samples from students were determined. This is of great significance to explore the accumulation and excretion patterns of PBDEs in the human body. The median PBDEs concentrations in the dust (College: 84.59 ng/g; Home: 170.32 ng/g) and hair (undergraduate: 6.16 ng/g; Home: 3.25 ng/g) samples were generally lower than were found in the majority of previous studies. The PBDEs concentrations in the hair and urine samples were subjected to principal component analysis, and the results combined with the PBDEs detection rates confirmed that hair is a useful non-invasive sampling medium for assessing PBDEs exposure and the risks posed. Body mass indices (BMIs) were used to divide students who had not been exposed to large amounts of PBDEs into groups. Body fat percentage is an important factor affecting the accumulation of PBDE in the human body. Environmental factors were found to affect the PBDEs concentrations in the hair and urine samples less for normal-weight students (BMI≤24) than overweight students (BMI>24). Short-term environmental changes to more readily affect the PBDEs concentrations in the tissues of the normal-weight than overweight students. PBDEs with seven or more bromine substituents were found not to be readily excreted in urine. Performing molecular docking simulations of the binding of isomers BDE-99 and BDE-100 to megalin. The binding energy was higher for BDE-100 and megalin than for BDE-99 and megalin, meaning BDE-99 would be more readily excreted than BDE-100.
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Affiliation(s)
- Junjie Jiang
- College of Life and Environmental Sciences, Minzu University of China, Beijing 100081, China.
| | - Tianwei Li
- College of Life and Environmental Sciences, Minzu University of China, Beijing 100081, China.
| | - Erde Wang
- College of Life and Environmental Sciences, Minzu University of China, Beijing 100081, China.
| | - Yan Zhang
- College of Life and Environmental Sciences, Minzu University of China, Beijing 100081, China.
| | - Jiali Han
- College of Life and Environmental Sciences, Minzu University of China, Beijing 100081, China.
| | - Linli Tan
- College of Life and Environmental Sciences, Minzu University of China, Beijing 100081, China.
| | - Xiang Li
- College of Life and Environmental Sciences, Minzu University of China, Beijing 100081, China.
| | - Yuhao Fan
- College of Life and Environmental Sciences, Minzu University of China, Beijing 100081, China.
| | - Ye Wu
- College of Life and Environmental Sciences, Minzu University of China, Beijing 100081, China.
| | - Qianhui Chen
- College of Life and Environmental Sciences, Minzu University of China, Beijing 100081, China.
| | - Jun Jin
- College of Life and Environmental Sciences, Minzu University of China, Beijing 100081, China; Engineering Research Center of Food Environment and Public Health, Beijing, 100081, China.
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3
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Satarug S, Vesey DA, Gobe GC, Phelps KR. The pathogenesis of albuminuria in cadmium nephropathy. Curr Res Toxicol 2023; 6:100140. [PMID: 38116328 PMCID: PMC10726218 DOI: 10.1016/j.crtox.2023.100140] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 11/16/2023] [Accepted: 11/30/2023] [Indexed: 12/21/2023] Open
Abstract
Background Urinary cadmium excretion (ECd) rises with renal tissue content of the metal. Whereas glomerulopathies are sometimes associated with massive albuminuria, tubular accumulation of Cd typically causes modest albuminuria. Since β2-microglobulinuria (Eβ2M) is an established marker of proximal tubular dysfunction, we hypothesized that a comparison of albuminuria (Ealb) to Eβ2M in Cd-exposed subjects would provide evidence of similar mishandling of both proteins. Methods To depict excretion rates per functional nephron, ECd, Ealb, and Eβ2M were normalized to creatinine clearance (Ccr), a surrogate for the glomerular filtration rate (GFR). Estimation of GFR itself (eGFR) was accomplished with CKD-EPI formulas (2009). Linear and logistic regression analyses were performed to relate Ealb/Ccr, Eβ2M/Ccr, and eGFR to several independent variables. Simple linear regressions of eGFR, Ealb/Ccr, and Eβ2M/Ccr on ECd/Ccr were examined before and after adjustment of dependent variables for age. All regressions were performed after log-transformation of ratios and standardization of all variables. Increments in Ealb/Ccr and Eβ2M/Ccr and decrements in eGFR were quantified through four quartiles of ECd/Ccr. Results As age or ECd/Ccr rose, Ealb/Ccr and Eβ2M/Ccr also rose, and eGFR fell. In linear regressions, slopes relating Ealb/Ccr and Eβ2M/Ccr to ECd/Ccr were similar. After adjustment of dependent variables for age, coefficients of determination (R2) for all regressions rose by a multiple, and slopes approached unity. Ealb/Ccr and Eβ2M/Ccr were similarly associated with each other. Mean Ealb/Ccr and Eβ2M/Ccr rose and mean eGFR fell in stepwise fashion through quartiles of ECd/Ccr. Whereas Eβ2M/Ccr did not vary with blood pressure, Ealb/Ccr rose in association with hypertension in two of the four quartiles. Conclusions Our data indicate that Cd in renal tissue affected tubular reabsorption of albumin and β2M similarly in a large cohort of exposed subjects. The results suggest that Cd reduced receptor-mediated endocytosis and subsequent lysosomal degradation of each protein by a shared mechanism.
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Affiliation(s)
- Soisungwan Satarug
- Centre for Kidney Disease Research, Translational Research Institute, Brisbane, Australia
| | - David A. Vesey
- Centre for Kidney Disease Research, Translational Research Institute, Brisbane, Australia
- Department of Kidney and Transplant Services, Princess Alexandra Hospital, Brisbane, Australia
| | - Glenda C. Gobe
- Centre for Kidney Disease Research, Translational Research Institute, Brisbane, Australia
- School of Biomedical Sciences, The University of Queensland, Brisbane, Australia
- NHMRC Centre of Research Excellence for CKD QLD, UQ Health Sciences, Royal Brisbane and Women’s Hospital, Brisbane, Australia
| | - Kenneth R. Phelps
- Stratton Veterans Affairs Medical Center and Albany Medical College, Albany, NY, USA
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4
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Birn H, Nielsen R, Weyer K. Tubular albumin uptake: is there evidence for a quantitatively important, receptor-independent mechanism? Kidney Int 2023; 104:1069-1073. [PMID: 37981430 DOI: 10.1016/j.kint.2023.07.030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 07/06/2023] [Accepted: 07/11/2023] [Indexed: 11/21/2023]
Affiliation(s)
- Henrik Birn
- Department of Biomedicine, Aarhus University, Aarhus, Denmark; Department of Clinical Medicine, Aarhus University, Aarhus, Denmark; Department of Renal Medicine, Aarhus University Hospital, Aarhus, Denmark.
| | - Rikke Nielsen
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Kathrin Weyer
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
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5
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Kho I, Demina EP, Pan X, Londono I, Cairo CW, Sturiale L, Palmigiano A, Messina A, Garozzo D, Ung RV, Mac-Way F, Bonneil É, Thibault P, Lemaire M, Morales CR, Pshezhetsky AV. Severe kidney dysfunction in sialidosis mice reveals an essential role for neuraminidase 1 in reabsorption. JCI Insight 2023; 8:e166470. [PMID: 37698928 PMCID: PMC10619504 DOI: 10.1172/jci.insight.166470] [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: 10/24/2022] [Accepted: 09/06/2023] [Indexed: 09/14/2023] Open
Abstract
Sialidosis is an ultra-rare multisystemic lysosomal disease caused by mutations in the neuraminidase 1 (NEU1) gene. The severe type II form of the disease manifests with a prenatal/infantile or juvenile onset, bone abnormalities, severe neuropathology, and visceromegaly. A subset of these patients present with nephrosialidosis, characterized by abrupt onset of fulminant glomerular nephropathy. We studied the pathophysiological mechanism of the disease in 2 NEU1-deficient mouse models, a constitutive Neu1-knockout, Neu1ΔEx3, and a conditional phagocyte-specific knockout, Neu1Cx3cr1ΔEx3. Mice of both strains exhibited terminal urinary retention and severe kidney damage with elevated urinary albumin levels, loss of nephrons, renal fibrosis, presence of storage vacuoles, and dysmorphic mitochondria in the intraglomerular and tubular cells. Glycoprotein sialylation in glomeruli, proximal distal tubules, and distal tubules was drastically increased, including that of an endocytic reabsorption receptor megalin. The pool of megalin bearing O-linked glycans with terminal galactose residues, essential for protein targeting and activity, was reduced to below detection levels. Megalin levels were severely reduced, and the protein was directed to lysosomes instead of the apical membrane. Together, our results demonstrated that desialylation by NEU1 plays a crucial role in processing and cellular trafficking of megalin and that NEU1 deficiency in sialidosis impairs megalin-mediated protein reabsorption.
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Affiliation(s)
- Ikhui Kho
- CHU Sainte-Justine Research Center, University of Montreal, Montreal, Québec, Canada
- Department of Anatomy and Cell Biology, McGill University, Montreal, Québec, Canada
| | - Ekaterina P. Demina
- CHU Sainte-Justine Research Center, University of Montreal, Montreal, Québec, Canada
| | - Xuefang Pan
- CHU Sainte-Justine Research Center, University of Montreal, Montreal, Québec, Canada
| | - Irene Londono
- CHU Sainte-Justine Research Center, University of Montreal, Montreal, Québec, Canada
| | | | - Luisa Sturiale
- CNR, Institute for Polymers, Composites and Biomaterials, Catania, Italy
| | - Angelo Palmigiano
- CNR, Institute for Polymers, Composites and Biomaterials, Catania, Italy
| | - Angela Messina
- CNR, Institute for Polymers, Composites and Biomaterials, Catania, Italy
| | - Domenico Garozzo
- CNR, Institute for Polymers, Composites and Biomaterials, Catania, Italy
| | - Roth-Visal Ung
- CHU de Québec Research Center, L’Hôtel-Dieu de Québec Hospital, Faculty and Department of Medicine, University Laval, Québec City, Québec, Canada
| | - Fabrice Mac-Way
- CHU de Québec Research Center, L’Hôtel-Dieu de Québec Hospital, Faculty and Department of Medicine, University Laval, Québec City, Québec, Canada
| | - Éric Bonneil
- Institute for Research in Immunology and Cancer, University of Montreal, Montreal, Québec, Canada
| | - Pierre Thibault
- Institute for Research in Immunology and Cancer, University of Montreal, Montreal, Québec, Canada
| | - Mathieu Lemaire
- Division of Nephrology, The Hospital for Sick Kids, Faculty of Medicine, University of Toronto, Ontario, Canada
- Cell Biology Program, SickKids Research Institute, Toronto, Ontario, Canada
| | - Carlos R. Morales
- Department of Anatomy and Cell Biology, McGill University, Montreal, Québec, Canada
| | - Alexey V. Pshezhetsky
- CHU Sainte-Justine Research Center, University of Montreal, Montreal, Québec, Canada
- Department of Anatomy and Cell Biology, McGill University, Montreal, Québec, Canada
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6
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Li Q, Yang Z, Wang C, Yu L, Sun S. Low molecular weight proteinuria, congenital myopia and hearing loss in a 10-year-old boy: Answers. Pediatr Nephrol 2023; 38:2587-2590. [PMID: 36688942 DOI: 10.1007/s00467-023-05883-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 12/22/2022] [Accepted: 01/02/2023] [Indexed: 01/24/2023]
Affiliation(s)
- Qian Li
- Department of Pediatric Nephrology and Rheumatism and Immunology, Shandong Provincial Hospital, Cheeloo College of Medicine, Shandong University, Jinan, 250021, People's Republic of China
- Department of Pediatric Nephrology and Rheumatism and Immunology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, No. 324 Jingwu Road, Jinan, 250021, People's Republic of China
| | - Zhenle Yang
- Department of Pediatric Nephrology and Rheumatism and Immunology, Shandong Provincial Hospital, Cheeloo College of Medicine, Shandong University, Jinan, 250021, People's Republic of China
- Department of Pediatric Nephrology and Rheumatism and Immunology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, No. 324 Jingwu Road, Jinan, 250021, People's Republic of China
| | - Cong Wang
- Department of Pediatric Nephrology and Rheumatism and Immunology, Shandong Provincial Hospital, Cheeloo College of Medicine, Shandong University, Jinan, 250021, People's Republic of China
- Department of Pediatric Nephrology and Rheumatism and Immunology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, No. 324 Jingwu Road, Jinan, 250021, People's Republic of China
| | - Lichun Yu
- Department of Pediatric Nephrology and Rheumatism and Immunology, Shandong Provincial Hospital, Cheeloo College of Medicine, Shandong University, Jinan, 250021, People's Republic of China
- Department of Pediatric Nephrology and Rheumatism and Immunology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, No. 324 Jingwu Road, Jinan, 250021, People's Republic of China
| | - Shuzhen Sun
- Department of Pediatric Nephrology and Rheumatism and Immunology, Shandong Provincial Hospital, Cheeloo College of Medicine, Shandong University, Jinan, 250021, People's Republic of China.
- Department of Pediatric Nephrology and Rheumatism and Immunology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, No. 324 Jingwu Road, Jinan, 250021, People's Republic of China.
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7
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Rasmussen MQ, Tindbæk G, Nielsen MM, Merrild C, Steiniche T, Pedersen JS, Moestrup SK, Degn SE, Madsen M. Epigenetic Silencing of LRP2 Is Associated with Dedifferentiation and Poor Survival in Multiple Solid Tumor Types. Cancers (Basel) 2023; 15:cancers15061830. [PMID: 36980716 PMCID: PMC10046670 DOI: 10.3390/cancers15061830] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 03/07/2023] [Accepted: 03/09/2023] [Indexed: 03/30/2023] Open
Abstract
More than 80% of human cancers originate in epithelial tissues. Loss of epithelial cell characteristics are hallmarks of tumor development. Receptor-mediated endocytosis is a key function of absorptive epithelial cells with importance for cellular and organismal homeostasis. LRP2 (megalin) is the largest known endocytic membrane receptor and is essential for endocytosis of various ligands in specialized epithelia, including the proximal tubules of the kidney, the thyroid gland, and breast glandular epithelium. However, the role and regulation of LRP2 in cancers that arise from these tissues has not been delineated. Here, we examined the expression of LRP2 across 33 cancer types in The Cancer Genome Atlas. As expected, the highest levels of LRP2 were found in cancer types that arise from LRP2-expressing absorptive epithelial cells. However, in a subset of tumors from these cancer types, we observed epigenetic silencing of LRP2. LRP2 expression showed a strong inverse correlation to methylation of a specific CpG site (cg02361027) in the first intron of the LRP2 gene. Interestingly, low expression of LRP2 was associated with poor patient outcome in clear cell renal cell carcinoma, papillary renal cell carcinoma, mesothelioma, papillary thyroid carcinoma, and invasive breast carcinoma. Furthermore, loss of LRP2 expression was associated with dedifferentiated histological and molecular subtypes of these cancers. These observations now motivate further studies on the functional role of LRP2 in tumors of epithelial origin and the potential use of LRP2 as a cancer biomarker.
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Affiliation(s)
| | - Gitte Tindbæk
- Department of Biomedicine, Aarhus University, 8000 Aarhus, Denmark
- Department of Clinical Biochemistry, Horsens Regional Hospital, 8700 Horsens, Denmark
| | - Morten Muhlig Nielsen
- Department of Molecular Medicine (MOMA), Aarhus University Hospital, 8200 Aarhus, Denmark
- Department of Clinical Medicine, Aarhus University, 8200 Aarhus, Denmark
| | - Camilla Merrild
- Department of Biomedicine, Aarhus University, 8000 Aarhus, Denmark
| | - Torben Steiniche
- Department of Pathology, Aarhus University Hospital, 8200 Aarhus, Denmark
| | - Jakob Skou Pedersen
- Department of Molecular Medicine (MOMA), Aarhus University Hospital, 8200 Aarhus, Denmark
- Department of Clinical Medicine, Aarhus University, 8200 Aarhus, Denmark
- Bioinformatics Research Center (BiRC), Aarhus University, 8000 Aarhus, Denmark
| | - Søren K Moestrup
- Department of Biomedicine, Aarhus University, 8000 Aarhus, Denmark
- Department of Cancer and Inflammation Research, University of Southern Denmark, 5230 Odense, Denmark
| | - Søren E Degn
- Department of Biomedicine, Aarhus University, 8000 Aarhus, Denmark
| | - Mette Madsen
- Department of Biomedicine, Aarhus University, 8000 Aarhus, Denmark
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8
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Yuan S, Huang X, Zhang S, Yang S, Rui X, Qi X, Wang X, Zheng Y, Rong W, Sheng X. Two novel variations in LRP2 cause Donnai-Barrow syndrome in a Chinese family with severe early-onset high myopia. Front Genet 2023; 14:1107347. [PMID: 36777721 PMCID: PMC9911814 DOI: 10.3389/fgene.2023.1107347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Accepted: 01/17/2023] [Indexed: 02/14/2023] Open
Abstract
Donnai-Barrow syndrome (DBS) is a rare autosomal recessive disorder caused by mutation in the low density lipoprotein receptor-related protein 2 gene (LRP2). Defects in this protein may lead to clinical multiple organ malformations by affecting the development of organs such as the nervous system, eyes, ears, and kidneys. Although some variations on LRP2 have been found to be associated with DBS, early diagnosis and prevention of patients with atypical DBS remains a challenge for many physicians because of their clinical heterogeneity. The objective of this study is to explore the association between the clinical presentation and the genotype of a DBS patient who was initially diagnosed with early-onset high myopia (eoHM) from a healthy Chinese family. To this end, we tested the patient of this family via whole exome sequencing and further verified the results among other family members by Sanger sequencing. Comprehensive ophthalmic tests as well as other systemic examinations were also performed on participants with various genotypes. Genetic assessment revealed that two novel variations in LRP2, a de novo missense variation (c.9032G>A; p.Arg3011Lys) and a novel splicing variation (c.2909-2A>T) inherited from the father, were both carried by the proband in this family, and they are strongly associated with the typical clinical features of DBS patients. Therefore, in this paper we are the first to report two novel compound heterozygous variations in LPR2 causing DBS. Our study extends the genotypic spectrums for LPR2-DBS and better assists physicians in predicting, diagnosing, and conducting gene therapy for DBS.
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Affiliation(s)
- Shiqin Yuan
- Ningxia Eye Hospital, People’s Hospital of Ningxia Hui Autonomous Region, Third Clinical Medical College of Ningxia Medical University, Yinchuan, China
| | - Xiaoyu Huang
- Ningxia Eye Hospital, People’s Hospital of Ningxia Hui Autonomous Region, Third Clinical Medical College of Ningxia Medical University, Yinchuan, China,Clinical Medical College, Ningxia Medical University, Yinchuan, China
| | - Shuang Zhang
- Ningxia Eye Hospital, People’s Hospital of Ningxia Hui Autonomous Region, Third Clinical Medical College of Ningxia Medical University, Yinchuan, China
| | - Shangying Yang
- Ningxia Eye Hospital, People’s Hospital of Ningxia Hui Autonomous Region, Third Clinical Medical College of Ningxia Medical University, Yinchuan, China,Clinical Medical College, Ningxia Medical University, Yinchuan, China
| | - Xue Rui
- Gansu Aier Ophthalmology and Optometry Hospital, Lanzhou, China
| | - Xiaolong Qi
- Ningxia Eye Hospital, People’s Hospital of Ningxia Hui Autonomous Region, Third Clinical Medical College of Ningxia Medical University, Yinchuan, China
| | - Xuhui Wang
- Ningxia Eye Hospital, People’s Hospital of Ningxia Hui Autonomous Region, Third Clinical Medical College of Ningxia Medical University, Yinchuan, China
| | - Yali Zheng
- Department of Kidney Internal Medicine, People’s Hospital of Ningxia Hui Autonomous Region, Third Clinical Medical College of Ningxia Medical University, Yinchuan, China
| | - Weining Rong
- Ningxia Eye Hospital, People’s Hospital of Ningxia Hui Autonomous Region, Third Clinical Medical College of Ningxia Medical University, Yinchuan, China,*Correspondence: Xunlun Sheng, ; Weining Rong,
| | - Xunlun Sheng
- Gansu Aier Ophthalmology and Optometry Hospital, Lanzhou, China,*Correspondence: Xunlun Sheng, ; Weining Rong,
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9
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Megalin and Vitamin D Metabolism—Implications in Non-Renal Tissues and Kidney Disease. Nutrients 2022; 14:nu14183690. [PMID: 36145066 PMCID: PMC9506339 DOI: 10.3390/nu14183690] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Revised: 09/02/2022] [Accepted: 09/06/2022] [Indexed: 11/17/2022] Open
Abstract
Megalin is an endocytic receptor abundantly expressed in proximal tubular epithelial cells and other calciotropic extrarenal cells expressing vitamin D metabolizing enzymes, such as bone and parathyroid cells. The receptor functions in the uptake of the vitamin D-binding protein (DBP) complexed to 25 hydroxyvitamin D3 (25(OH)D3), facilitating the intracellular conversion of precursor 25(OH)D3 to the active 1,25 dihydroxyvitamin D3 (1,25(OH)2D3). The significance of renal megalin-mediated reabsorption of 25(OH)D3 and 1,25(OH)2D3 has been well established experimentally, and other studies have demonstrated relevant roles of extrarenal megalin in regulating vitamin D homeostasis in mammary cells, fat, muscle, bone, and mesenchymal stem cells. Parathyroid gland megalin may regulate calcium signaling, suggesting intriguing possibilities for megalin-mediated cross-talk between calcium and vitamin D regulation in the parathyroid; however, parathyroid megalin functionality has not been assessed in the context of vitamin D. Within various models of chronic kidney disease (CKD), megalin expression appears to be downregulated; however, contradictory results have been observed between human and rodent models. This review aims to provide an overview of the current knowledge of megalin function in the context of vitamin D metabolism, with an emphasis on extrarenal megalin, an area that clearly requires further investigation.
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10
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Elsakka EGE, Mokhtar MM, Hegazy M, Ismail A, Doghish AS. Megalin, a multi-ligand endocytic receptor, and its participation in renal function and diseases: A review. Life Sci 2022; 308:120923. [PMID: 36049529 DOI: 10.1016/j.lfs.2022.120923] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Revised: 08/13/2022] [Accepted: 08/26/2022] [Indexed: 11/16/2022]
Abstract
The endocytosis mechanism is a complicated system that is essential for cell signaling and survival. Megalin, a membrane-associated endocytic receptor, and its related proteins such as cubilin, the neonatal Fc receptor for IgG, and NaPi-IIa are important in receptors-mediated endocytosis. Physiologically, megalin uptakes plasma vitamins and proteins from primary urine, preventing their loss. It also facilitates tubular retrieval of solutes and endogenous components that may be involved in modulation and recovery from kidney injuries. Moreover, megalin is responsible for endocytosis of xenobiotics and drugs in renal tubules, increasing their half-life and/or their toxicity. Fluctuations in megalin expression and/or functionality due to changes in its regulatory mechanisms are associated with some sort of kidney injury. Also, it's an important component of several pathological conditions, including diabetic nephropathy and Dent disease. Thus, exploring the fundamental role of megalin in the kidney might help in the protection and/or treatment of multiple kidney-related diseases. Hence, this review aimed to explore the physiological roles of megalin in the kidney and their implications for kidney-related injuries.
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Affiliation(s)
- Elsayed G E Elsakka
- Biochemistry and Molecular Biology Department, Faculty of Pharmacy (Boys), Al-Azhar University, Nasr City 11231, Cairo, Egypt.
| | - Mahmoud Mohamed Mokhtar
- Biochemistry and Molecular Biology Department, Faculty of Pharmacy (Boys), Al-Azhar University, Nasr City 11231, Cairo, Egypt
| | - Maghawry Hegazy
- Biochemistry and Molecular Biology Department, Faculty of Pharmacy (Boys), Al-Azhar University, Nasr City 11231, Cairo, Egypt
| | - Ahmed Ismail
- Biochemistry and Molecular Biology Department, Faculty of Pharmacy (Boys), Al-Azhar University, Nasr City 11231, Cairo, Egypt
| | - Ahmed S Doghish
- Department of Biochemistry, Faculty of Pharmacy, Badr University in Cairo (BUC), Badr City, Cairo 11829, Egypt.
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11
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Alhasan K, D'Alessandri-Silva C, Mongia A, Topaloglu R, Tasic V, Filler G. Young Adults With Hereditary Tubular Diseases: Practical Aspects for Adult-Focused Colleagues. Adv Chronic Kidney Dis 2022; 29:292-307. [PMID: 36084976 DOI: 10.1053/j.ackd.2021.11.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Revised: 11/07/2021] [Accepted: 11/15/2021] [Indexed: 11/11/2022]
Abstract
Recent advances in the management of kidney tubular diseases have resulted in a significant cohort of adolescents and young adults transitioning from pediatric- to adult-focused care. Most of the patients under adult-focused care have glomerular diseases, whereas rarer tubular diseases form a considerable proportion of pediatric patients. The purpose of this review is to highlight the clinical signs and symptoms of tubular disorders, as well as their diagnostic workup, including laboratory findings and imaging, during young adulthood. We will then discuss more common disorders such as cystinosis, cystinuria, distal kidney tubular acidosis, congenital nephrogenic diabetes insipidus, Dent disease, rickets, hypercalciuria, and syndromes such as Bartter, Fanconi, Gitelman, Liddle, and Lowe. This review is a practical guide on the diagnostic and therapeutic approach of tubular conditions affecting young adults who are transitioning to adult-focused care.
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Affiliation(s)
- Khalid Alhasan
- Department of Pediatrics, College of Medicine, King Saud University, Riyadh, Saudi Arabia
| | - Cynthia D'Alessandri-Silva
- Department of Pediatrics, University of Connecticut School of Medicine, Farmington, and Nephrology, Connecticut Children's Medical Center, Hartford, CT
| | - Anil Mongia
- Department of Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY
| | - Rezan Topaloglu
- Department of Paediatrics, Division of Pediatric Nephrology, Hacettepe University School of Medicine, Ankara, Turkey
| | - Velibor Tasic
- University Children's Hospital, Medical School, Skopje, North Macedonia
| | - Guido Filler
- Department of Paediatrics, Division of Pediatric Nephrology, Western University, London, ON, Canada; Department of Medicine, Western University, London, ON, Canada; Department of Pathology and Laboratory Medicine, Western University, London, ON, Canada.
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12
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Molitoris BA, Sandoval RM, Yadav SPS, Wagner MC. Albumin Uptake and Processing by the Proximal Tubule: Physiologic, Pathologic and Therapeutic Implications. Physiol Rev 2022; 102:1625-1667. [PMID: 35378997 PMCID: PMC9255719 DOI: 10.1152/physrev.00014.2021] [Citation(s) in RCA: 41] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
For nearly 50 years the proximal tubule (PT) has been known to reabsorb, process, and either catabolize or transcytose albumin from the glomerular filtrate. Innovative techniques and approaches have provided insights into these processes. Several genetic diseases, nonselective PT cell defects, chronic kidney disease (CKD), and acute PT injury lead to significant albuminuria, reaching nephrotic range. Albumin is also known to stimulate PT injury cascades. Thus, the mechanisms of albumin reabsorption, catabolism, and transcytosis are being reexamined with the use of techniques that allow for novel molecular and cellular discoveries. Megalin, a scavenger receptor, cubilin, amnionless, and Dab2 form a nonselective multireceptor complex that mediates albumin binding and uptake and directs proteins for lysosomal degradation after endocytosis. Albumin transcytosis is mediated by a pH-dependent binding affinity to the neonatal Fc receptor (FcRn) in the endosomal compartments. This reclamation pathway rescues albumin from urinary losses and cellular catabolism, extending its serum half-life. Albumin that has been altered by oxidation, glycation, or carbamylation or because of other bound ligands that do not bind to FcRn traffics to the lysosome. This molecular sorting mechanism reclaims physiological albumin and eliminates potentially toxic albumin. The clinical importance of PT albumin metabolism has also increased as albumin is now being used to bind therapeutic agents to extend their half-life and minimize filtration and kidney injury. The purpose of this review is to update and integrate evolving information regarding the reabsorption and processing of albumin by proximal tubule cells including discussion of genetic disorders and therapeutic considerations.
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Affiliation(s)
- Bruce A. Molitoris
- Division of Nephrology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, United States
- Dept.of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana, United States
| | - Ruben M. Sandoval
- Division of Nephrology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, United States
| | - Shiv Pratap S. Yadav
- Division of Nephrology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, United States
| | - Mark C. Wagner
- Division of Nephrology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, United States
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13
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Park JS, Kim Y, Kang J. Genome-wide meta-analysis revealed several genetic loci associated with serum uric acid levels in Korean population: an analysis of Korea Biobank data. J Hum Genet 2022; 67:231-237. [PMID: 34719683 DOI: 10.1038/s10038-021-00991-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Revised: 10/19/2021] [Accepted: 10/20/2021] [Indexed: 11/09/2022]
Abstract
The serum uric acid (SUA) level is an important determinant of gout, hypertension, metabolic syndrome, and cardiovascular disease. Although previous genome-wide studies have identified multiple genetic variants associated with SUA, most genetic analyses have focused on individuals with European ancestry; thus, understanding of the genetic architecture of SUA is currently limited for Asian populations. We conducted a genome-wide meta-analysis based on Korea Biobank data consistent with three cohorts; namely, the Korean Genome and Epidemiology Study (KoGES) Ansan and Ansung, KoGES Health Examinee, and KoGES Cardiovascular Disease Association studies. In total, 60,585 participants aged ≥40 years were included in the analysis of the three cohorts. We used logistic regression analyses to perform genome-wide association study (GWAS) adjustments for confounding variables. Subsequently, a meta-analysis was conducted by combining the analyses of the three GWASs. We identified 8,105 variants at 22 genetic loci with a P value < 5 × 10-8. Among these, six novel genetic loci associated with SUA in the Korean population were identified (rs4715517 in HCRTR2, rs145099458 in 3.2 kb 3' of MLXIPL, rs1137642 in B4GALT1, rs659107 in LOC105378410, rs7919329 in LOC107984274, and rs2240751 in MFSD12). Our meta-analysis provides insights into the genetic architecture of SUA in the Korean population. Further studies are warranted to replicate the study results and elucidate the specific role of these variants in SUA homeostasis.
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Affiliation(s)
- Jin Sung Park
- Department of Medicine, Kosin University Gospel Hospital, Kosin University College of Medicine, Busan, Republic of Korea
| | - Yunkyung Kim
- Division of Rheumatology, Department of Internal Medicine, Kosin University Gospel Hospital, Kosin University College of Medicine, Busan, Republic of Korea
| | - Jihun Kang
- Department of Family Medicine, Kosin University Gospel Hospital, Kosin University College of Medicine, Busan, Republic of Korea.
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14
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Alyousef MY, Abuhaimed AA, Alkelabi DM, AlKahtani M, Yousef EM, Yousef MF. Performance of Children With Donnai-Barrow Syndrome After Cochlear Implantation: A Case Report. Cureus 2022; 14:e21063. [PMID: 35165538 PMCID: PMC8826483 DOI: 10.7759/cureus.21063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/09/2022] [Indexed: 11/12/2022] Open
Abstract
Donnai-Barrow syndrome (DBS) is a rare autosomal recessive hereditary disorder that affects a variety of body systems. One of the most common symptoms in DBS patients is severe bilateral sensorineural hearing loss. The objective of this report is to highlight the performance of such patients after receiving cochlear implants as a management of their hearing loss. We reviewed the medical records of two cousins diagnosed with DBS before and after cochlear implantation, with a particular focus on their auditory and language performance. After receiving the cochlear implant, both patients showed substantial progress in auditory and speech perception, as well as their intelligence quotients, allowing them to join mainstream schools. In conclusion, our findings showed that cochlear implantation can be considered an ideal approach for the management of DBS patients who suffer from bilateral sensorineural hearing loss.
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15
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Agarwal S, Sudhini YR, Polat OK, Reiser J, Altintas MM. Renal cell markers: lighthouses for managing renal diseases. Am J Physiol Renal Physiol 2021; 321:F715-F739. [PMID: 34632812 DOI: 10.1152/ajprenal.00182.2021] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Kidneys, one of the vital organs in our body, are responsible for maintaining whole body homeostasis. The complexity of renal function (e.g., filtration, reabsorption, fluid and electrolyte regulation, and urine production) demands diversity not only at the level of cell types but also in their overall distribution and structural framework within the kidney. To gain an in depth molecular-level understanding of the renal system, it is imperative to discern the components of kidney and the types of cells residing in each of the subregions. Recent developments in labeling, tracing, and imaging techniques have enabled us to mark, monitor, and identify these cells in vivo with high efficiency in a minimally invasive manner. In this review, we summarize different cell types, specific markers that are uniquely associated with those cell types, and their distribution in the kidney, which altogether make kidneys so special and different. Cellular sorting based on the presence of certain proteins on the cell surface allowed for the assignment of multiple markers for each cell type. However, different studies using different techniques have found contradictions in cell type-specific markers. Thus, the term "cell marker" might be imprecise and suboptimal, leading to uncertainty when interpreting the data. Therefore, we strongly believe that there is an unmet need to define the best cell markers for a cell type. Although the compendium of renal-selective marker proteins presented in this review is a resource that may be useful to researchers, we acknowledge that the list may not be necessarily exhaustive.
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Affiliation(s)
- Shivangi Agarwal
- Department of Internal Medicine, Rush University, Chicago, Illinois
| | | | - Onur K Polat
- Department of Internal Medicine, Rush University, Chicago, Illinois
| | - Jochen Reiser
- Department of Internal Medicine, Rush University, Chicago, Illinois
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16
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Weisz OA. Endocytic adaptation to functional demand by the kidney proximal tubule. J Physiol 2021; 599:3437-3446. [PMID: 34036593 DOI: 10.1113/jp281599] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Accepted: 05/06/2021] [Indexed: 12/28/2022] Open
Abstract
The kidney proximal tubule (PT) efficiently recovers the low level of albumin and other proteins that normally escape the glomerular filtration barrier. Two large receptors, megalin and cubilin/amnionless (CUBAM), bind to and efficiently retrieve these predominantly low molecular-weight proteins via clathrin-mediated endocytosis. Studies in cell culture models suggest that PT cells may sense changes in shear stress to modulate recovery of filtered proteins in response to normal variations in filtration rate. Impairments in PT endocytic function lead to the excretion of filtered proteins into the urine (tubular proteinuria). Remarkably, when the glomerular filtration barrier is breached, the PT is able to recover excess albumin with a capacity that is orders of magnitude higher than normal. What mediates this excess capacity for albumin uptake under nephrotic conditions, and why doesn't it compensate to prevent tubular proteinuria? Here we propose an integrated new working model to describe the PT recovery of filtered proteins under normal and nephrotic states. We hypothesize that uptake via the fluid phase provides excess capacity to recover high concentrations of filtered proteins under nephrotic conditions. Further, concentration of tubular fluid along the tubule axis will enhance the efficiency of uptake in more distal regions of the PT. By contrast to cells where fluid phase and receptor-mediated uptake are independent pathways, expression of megalin is required to maintain apical endocytic pathway integrity and is essential for both uptake mechanisms. This model accounts for both the high-affinity and the high-capacity responses to filtration load in physiological and pathological states.
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Affiliation(s)
- Ora A Weisz
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
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17
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Aksenova M, Zaikova N, Lepaeva T. Spectrum of tubular dysfunction in Donnai-Barrow syndrome. Lessons for the clinical nephrologist. J Nephrol 2021; 34:921-924. [PMID: 33471318 DOI: 10.1007/s40620-020-00890-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Accepted: 10/13/2020] [Indexed: 11/28/2022]
Affiliation(s)
- Marina Aksenova
- Nephrology Department of Y.Veltischev Research and Clinical Institute for Pediatrics at N.Pirogov, Russian National Research Medical University, Taldomskaya str.2, 125412, Moscow, Russia.
| | - Natalia Zaikova
- Nephrology Department of Y.Veltischev Research and Clinical Institute for Pediatrics at N.Pirogov, Russian National Research Medical University, Taldomskaya str.2, 125412, Moscow, Russia
| | - Tatiana Lepaeva
- Nephrology Department of Y.Veltischev Research and Clinical Institute for Pediatrics at N.Pirogov, Russian National Research Medical University, Taldomskaya str.2, 125412, Moscow, Russia
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18
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Christensen EI, Kristoffersen IB, Grann B, Thomsen JS, Andreasen A, Nielsen R. A well-developed endolysosomal system reflects protein reabsorption in segment 1 and 2 of rat proximal tubules. Kidney Int 2020; 99:841-853. [PMID: 33340516 DOI: 10.1016/j.kint.2020.11.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 11/01/2020] [Accepted: 11/05/2020] [Indexed: 12/26/2022]
Abstract
Proteinuria is a well-established marker and predictor of kidney disease. The receptors megalin and cubilin reabsorb filtered proteins and thereby proteinuria is avoided. It is unknown if all segments of the proximal tubule are involved in clearing the filtrate or if there exists a reserve capacity in case of increased glomerular protein filtration. To determine this, we performed serial sectioning of rat kidney and used stereology to quantify the endolysosomal system of the three segments of cortical and juxtamedullary nephrons by electron microscopy. Immunohistochemistry was applied to analyze the adaptor protein Dab2, which assists in megalin mediated endocytosis, megalin, and endocytic uptake of two endogenous megalin ligands; retinol binding protein and β2-microglobulin at exact tubular positions. Proteinuric rats (puromycin-treated) and mice (podocin knock-out) were analyzed to clarify the response of the tubule to increased protein filtration. We found that the endolysosomal system was most prominent in segment 1 and 2, whereas segment 3 was less developed. The depth of ligand uptake varied among nephrons, but it descended into segment 2 although uptake was lower than in segment 1 and it was never observed in segment 3. This was supported by prominent expression of Dab2 in segment 1 and 2. When protein filtration increased, segment 3 was included in the reabsorption process in proteinuric animals. Thus, segment 1 and 2 are responsible for clearing the filtrate for protein during normal physiological conditions, but the tubule exhibits plasticity and is able to include segment 3 under proteinuric stress.
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Affiliation(s)
| | | | - Birgitte Grann
- Department of Biomedicine, Anatomy, Aarhus University, Aarhus, Denmark
| | - Jesper S Thomsen
- Department of Biomedicine, Anatomy, Aarhus University, Aarhus, Denmark
| | - Arne Andreasen
- Department of Biomedicine, Anatomy, Aarhus University, Aarhus, Denmark
| | - Rikke Nielsen
- Department of Biomedicine, Anatomy, Aarhus University, Aarhus, Denmark.
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19
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Matsuura R, Hiraishi A, Holzman LB, Hanayama H, Harano K, Nakamura E, Hamasaki Y, Doi K, Nangaku M, Noiri E. SHROOM3, the gene associated with chronic kidney disease, affects the podocyte structure. Sci Rep 2020; 10:21103. [PMID: 33273487 PMCID: PMC7713385 DOI: 10.1038/s41598-020-77952-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Accepted: 11/15/2020] [Indexed: 01/11/2023] Open
Abstract
Chronic kidney disease is a public health burden and it remains unknown which genetic loci are associated with kidney function in the Japanese population, our genome-wide association study using the Biobank Japan dataset (excluding secondary kidney diseases, such as diabetes mellitus) clearly revealed that almost half of the top 50 single nucleotide polymorphisms associated with estimated glomerular filtration rate are located in the SHROOM3 gene, suggesting that SHROOM3 will be responsible for kidney function. Thus, to confirm this finding, supportive functional analyses were performed on Shroom3 in mice using fullerene-based siRNA delivery, which demonstrated that Shroom3 knockdown led to albuminuria and podocyte foot process effacement. The in vitro experiment shows that knockdown of Shroom3 caused defective formation of lamellipodia in podocyte, which would lead to the disruption of slit diaphragm. These results from the GWAS, in vivo and in vitro experiment were consistent with recent studies reporting that albuminuria leads to impairment of kidney function.
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Affiliation(s)
- Ryo Matsuura
- Department of Nephrology and Endocrinology, The University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan
| | - Atsuko Hiraishi
- Department of Nephrology and Endocrinology, The University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan
- Division of Genomic Medicine and Disease Prevention, Institute of Medical Science, The University of Tokyo, Shirokanedai, 4-6-1 Minato-ku, Tokyo, 108-8639, Japan
| | - Lawrence B Holzman
- Renal Electrolyte and Hypertension Division, Perelman School of Medicine, University of Pennsylvania, Philadelphia, 19104, USA
| | - Hiroki Hanayama
- Department of Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Koji Harano
- Department of Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Eiichi Nakamura
- Department of Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Yoshifumi Hamasaki
- Department of Hemodialysis and Apheresis, The University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan
| | - Kent Doi
- Department of Acute Medicine, The University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan
| | - Masaomi Nangaku
- Department of Nephrology and Endocrinology, The University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan
| | - Eisei Noiri
- Department of Nephrology and Endocrinology, The University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.
- National Center Biobank Network, National Center for Global Health and Medicine, 1-21-1 Toyama, Shinjuku, Tokyo, 162-8655, Japan.
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20
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Charlton JR, Tan W, Daouk G, Teot L, Rosen S, Bennett KM, Cwiek A, Nam S, Emma F, Jouret F, Oliveira JP, Tranebjærg L, Frykholm C, Mane S, Hildebrandt F, Srivastava T, Storm T, Christensen EI, Nielsen R. Beyond the tubule: pathological variants of LRP2, encoding the megalin receptor, result in glomerular loss and early progressive chronic kidney disease. Am J Physiol Renal Physiol 2020; 319:F988-F999. [PMID: 33103447 DOI: 10.1152/ajprenal.00295.2020] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Pathogenic variants in the LRP2 gene, encoding the multiligand receptor megalin, cause a rare autosomal recessive syndrome: Donnai-Barrow/Facio-Oculo-Acoustico-Renal (DB/FOAR) syndrome. Because of the rarity of the syndrome, the long-term consequences of the tubulopathy on human renal health have been difficult to ascertain, and the human clinical condition has hitherto been characterized as a benign tubular condition with asymptomatic low-molecular-weight proteinuria. We investigated renal function and morphology in a murine model of DB/FOAR syndrome and in patients with DB/FOAR. We analyzed glomerular filtration rate in mice by FITC-inulin clearance and clinically characterized six families, including nine patients with DB/FOAR and nine family members. Urine samples from patients were analyzed by Western blot analysis and biopsy materials were analyzed by histology. In the mouse model, we used histological methods to assess nephrogenesis and postnatal renal structure and contrast-enhanced magnetic resonance imaging to assess glomerular number. In megalin-deficient mice, we found a lower glomerular filtration rate and an increase in the abundance of injury markers, such as kidney injury molecule-1 and N-acetyl-β-d-glucosaminidase. Renal injury was validated in patients, who presented with increased urinary kidney injury molecule-1, classical markers of chronic kidney disease, and glomerular proteinuria early in life. Megalin-deficient mice had normal nephrogenesis, but they had 19% fewer nephrons in early adulthood and an increased fraction of nephrons with disconnected glomerulotubular junction. In conclusion, megalin dysfunction, as present in DB/FOAR syndrome, confers an increased risk of progression into chronic kidney disease.
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Affiliation(s)
- Jennifer R Charlton
- Division of Nephrology, Department of Pediatrics, University of Virginia, Charlottesville, Virginia
| | - Weizhen Tan
- Division of Nephrology, Massachusetts General Hospital for Children, Boston, Massachusetts
| | - Ghaleb Daouk
- Division of Nephrology, Massachusetts General Hospital for Children, Boston, Massachusetts
| | - Lisa Teot
- Department of Pathology, Boston Children's Hospital, Boston, Massachusetts
| | - Seymour Rosen
- Department of Pathology, Boston Children's Hospital, Boston, Massachusetts.,Department of Pathology, Beth Israel Deaconess Medical Center, Boston, Massachusetts
| | - Kevin M Bennett
- Department of Radiology, Washington University in Saint Louis, St. Louis, Missouri
| | - Aleksandra Cwiek
- Division of Nephrology, Department of Pediatrics, University of Virginia, Charlottesville, Virginia
| | - Sejin Nam
- Department of Physics, University of Hawai'i at Manoa, Manoa, Hawai'i
| | - Francesco Emma
- Division of Nephrology, Department of Pediatric Subspecialties, Bambino Gesù Children's Hospital- Istituto di Ricovero e Cura a Carattere Scientifico, Rome, Italy
| | - François Jouret
- Groupe Interdisciplinaire de Génoprotéomique Appliquée, Unit of Cardiovascular Sciences, University of Liège, Liège, Belgium
| | - João Paulo Oliveira
- Service of Medical Genetics, São João University Hospital Centre and Faculty of Medicine, University of Porto and i3S-Institute for Health Research and Innovation, Porto, Portugal
| | - Lisbeth Tranebjærg
- Department of Clinical Genetics, Rigshospitalet/The Kennedy Centre, Copenhagen, Denmark.,Institute of Clinical Medicine, University of Copenhagen, The Panum Institute, Copenhagen, Denmark
| | - Carina Frykholm
- Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden
| | - Shrikant Mane
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut
| | - Friedhelm Hildebrandt
- Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts
| | | | - Tina Storm
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | | | - Rikke Nielsen
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
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21
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Bedin M, Boyer O, Servais A, Li Y, Villoing-Gaudé L, Tête MJ, Cambier A, Hogan J, Baudouin V, Krid S, Bensman A, Lammens F, Louillet F, Ranchin B, Vigneau C, Bouteau I, Isnard-Bagnis C, Mache CJ, Schäfer T, Pape L, Gödel M, Huber TB, Benz M, Klaus G, Hansen M, Latta K, Gribouval O, Morinière V, Tournant C, Grohmann M, Kuhn E, Wagner T, Bole-Feysot C, Jabot-Hanin F, Nitschké P, Ahluwalia TS, Köttgen A, Andersen CBF, Bergmann C, Antignac C, Simons M. Human C-terminal CUBN variants associate with chronic proteinuria and normal renal function. J Clin Invest 2020; 130:335-344. [PMID: 31613795 DOI: 10.1172/jci129937] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Accepted: 10/02/2019] [Indexed: 12/30/2022] Open
Abstract
BACKGROUNDProteinuria is considered an unfavorable clinical condition that accelerates renal and cardiovascular disease. However, it is not clear whether all forms of proteinuria are damaging. Mutations in CUBN cause Imerslund-Gräsbeck syndrome (IGS), which is characterized by intestinal malabsorption of vitamin B12 and in some cases proteinuria. CUBN encodes for cubilin, an intestinal and proximal tubular uptake receptor containing 27 CUB domains for ligand binding.METHODSWe used next-generation sequencing for renal disease genes to genotype cohorts of patients with suspected hereditary renal disease and chronic proteinuria. CUBN variants were analyzed using bioinformatics, structural modeling, and epidemiological methods.RESULTSWe identified 39 patients, in whom biallelic pathogenic variants in the CUBN gene were associated with chronic isolated proteinuria and early childhood onset. Since the proteinuria in these patients had a high proportion of albuminuria, glomerular diseases such as steroid-resistant nephrotic syndrome or Alport syndrome were often the primary clinical diagnosis, motivating renal biopsies and the use of proteinuria-lowering treatments. However, renal function was normal in all cases. By contrast, we did not found any biallelic CUBN variants in proteinuric patients with reduced renal function or focal segmental glomerulosclerosis. Unlike the more N-terminal IGS mutations, 37 of the 41 proteinuria-associated CUBN variants led to modifications or truncations after the vitamin B12-binding domain. Finally, we show that 4 C-terminal CUBN variants are associated with albuminuria and slightly increased GFR in meta-analyses of large population-based cohorts.CONCLUSIONCollectively, our data suggest an important role for the C-terminal half of cubilin in renal albumin reabsorption. Albuminuria due to reduced cubilin function could be an unexpectedly common benign condition in humans that may not require any proteinuria-lowering treatment or renal biopsy.FUNDINGATIP-Avenir program, Fondation Bettencourt-Schueller (Liliane Bettencourt Chair of Developmental Biology), Agence Nationale de la Recherche (ANR) Investissements d'avenir program (ANR-10-IAHU-01) and NEPHROFLY (ANR-14-ACHN-0013, to MS), Steno Collaborative Grant 2018 (NNF18OC0052457, to TSA and MS), Heisenberg Professorship of the German Research Foundation (KO 3598/5-1, to AK), Deutsche Forschungsgemeinschaft (DFG) Collaborative Research Centre (SFB) KIDGEM 1140 (project 246781735, to CB), and Federal Ministry of Education and Research (BMB) (01GM1515C, to CB).
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Affiliation(s)
| | - Olivia Boyer
- Laboratory of Hereditary Kidney Disease, Imagine Institute, INSERM U1163, Université de Paris, Paris, France.,Department of Pediatric Nephrology and
| | - Aude Servais
- Laboratory of Hereditary Kidney Disease, Imagine Institute, INSERM U1163, Université de Paris, Paris, France.,Department of Nephrology, Necker Hospital, Assistance Publique Hôpitaux de Paris (APHP), Paris, France
| | - Yong Li
- Institute of Genetic Epidemiology, Faculty of Medicine and Medical Center, University of Freiburg, Freiburg, Germany
| | | | - Marie-Josephe Tête
- Laboratory of Hereditary Kidney Disease, Imagine Institute, INSERM U1163, Université de Paris, Paris, France
| | - Alexandra Cambier
- Department of Pediatric Nephrology and Transplantation, Robert-Debré Hospital, APHP, Paris, France
| | - Julien Hogan
- Department of Pediatric Nephrology and Transplantation, Robert-Debré Hospital, APHP, Paris, France
| | - Veronique Baudouin
- Department of Pediatric Nephrology and Transplantation, Robert-Debré Hospital, APHP, Paris, France
| | | | | | - Florie Lammens
- Centre Hospitalier Régional Universitaire de Lille, Lille, France
| | | | - Bruno Ranchin
- Department of Pediatric Nephrology, Hospices Civils de Lyon, Bron, France
| | - Cecile Vigneau
- Centre Hospitalier Universitaire de Rennes, INSERM U1085 IRSET-9, Rennes, France
| | - Iseline Bouteau
- Centre Hospitalier Universitaire de Poitiers, Poitiers, France
| | | | | | - Tobias Schäfer
- Renal Division, University Medical Center Freiburg, Freiburg, Germany
| | - Lars Pape
- Department of Pediatric Kidney, Liver and Metabolic Disease, Hannover Medical School, Hannover, Germany
| | - Markus Gödel
- Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Tobias B Huber
- Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | | | - Günter Klaus
- Department of Child and Adolescent Medicine, University Medical Center Marburg-Giessen, Marburg, Germany
| | - Matthias Hansen
- KfH-Nierenzentrum für Kinder und Jugendliche und Clementine-Kinderhospital, Frankfurt, Germany
| | - Kay Latta
- KfH-Nierenzentrum für Kinder und Jugendliche und Clementine-Kinderhospital, Frankfurt, Germany
| | - Olivier Gribouval
- Laboratory of Hereditary Kidney Disease, Imagine Institute, INSERM U1163, Université de Paris, Paris, France
| | | | - Carole Tournant
- Department of Genetics, Necker Hospital, APHP, Paris, France
| | - Maik Grohmann
- Center for Human Genetics, Bioscientia, Ingelheim, Germany.,Center for Human Genetics, Mainz, Germany
| | - Elisa Kuhn
- Center for Human Genetics, Bioscientia, Ingelheim, Germany
| | - Timo Wagner
- Center for Human Genetics, Bioscientia, Ingelheim, Germany
| | - Christine Bole-Feysot
- Bioinformatic Platform, INSERM UMR 1163, Institut Imagine, Paris, France.,Bioinformatics Core Facility, Structure Fédérative de Recherche Necker, INSERM US24/CNRS UMS3633, Université de Paris, Paris, France
| | - Fabienne Jabot-Hanin
- Bioinformatic Platform, INSERM UMR 1163, Institut Imagine, Paris, France.,Bioinformatics Core Facility, Structure Fédérative de Recherche Necker, INSERM US24/CNRS UMS3633, Université de Paris, Paris, France
| | - Patrick Nitschké
- Bioinformatic Platform, INSERM UMR 1163, Institut Imagine, Paris, France.,Bioinformatics Core Facility, Structure Fédérative de Recherche Necker, INSERM US24/CNRS UMS3633, Université de Paris, Paris, France
| | | | - Anna Köttgen
- Institute of Genetic Epidemiology, Faculty of Medicine and Medical Center, University of Freiburg, Freiburg, Germany
| | | | - Carsten Bergmann
- Center for Human Genetics, Bioscientia, Ingelheim, Germany.,Center for Human Genetics, Mainz, Germany.,Renal Division, Department of Medicine, University Hospital Freiburg, Freiburg, Germany
| | - Corinne Antignac
- Laboratory of Hereditary Kidney Disease, Imagine Institute, INSERM U1163, Université de Paris, Paris, France.,Department of Genetics, Necker Hospital, APHP, Paris, France
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22
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Abstract
Albuminuria acts as a marker of progressive chronic kidney disease and as an indicator for initiation of hypertension treatment via modulation of the renin-angiotensin-aldosterone system with angiotensin receptor blockers or angiotensin-converting enzyme inhibitors. However, the true significance of albuminuria has yet to be fully defined. Is it merely a marker of underlying pathophysiology, or does it play a causal role in the progression of kidney disease? The answer remains under debate. In this issue of the JCI, Bedin et al. used next-generation sequencing data to identify patients with chronic proteinuria who had biallelic variants in the cubilin gene (CUBN). Through investigation of these pathogenic mutations in CUBN, the authors have further illuminated the clinical implications of albuminuria.
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23
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Perez-Gomez MV, Sanchez-Niño MD, Ortiz A. Megalin/lipoprotein receptor-related protein 2 autoimmunity and kidney disease. Clin Kidney J 2020; 13:281-286. [PMID: 32701075 PMCID: PMC7367110 DOI: 10.1093/ckj/sfz171] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
In this issue of Clinical Kidney Journal, Gamayo et al. describe two cases of anti-low-density lipoprotein receptor-related protein 2 (LRP2) nephropathy. This is a recently described entity that has features of both tubulointerstitial disease and segmental membranous nephropathy. The originality of the present report consists of the association of a disease thought to be rare (only 13 in prior described patients, 11 in the past year) with B-cell lymphoproliferative disease. Together with the finding of a third case among 224 elderly patients studied, this raises the issue of the underdiagnoses of LRP2 nephropathy, on top of the potential association to B-cell malignancy. We now put these findings in context within the wider frame of autoimmunity against megalin/LRP2 and related antigens such as Fx1A and CD69.
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Affiliation(s)
- Maria V Perez-Gomez
- IIS-Fundacion Jimenez Diaz, School of Medicine, Universidad Autonoma de Madrid, Madrid, Spain
- Fundacion Renal Iñigo Alvarez de Toledo-IRSIN and REDINREN, Madrid, Spain
| | - Maria D Sanchez-Niño
- IIS-Fundacion Jimenez Diaz, School of Medicine, Universidad Autonoma de Madrid, Madrid, Spain
- Fundacion Renal Iñigo Alvarez de Toledo-IRSIN and REDINREN, Madrid, Spain
| | - Alberto Ortiz
- IIS-Fundacion Jimenez Diaz, School of Medicine, Universidad Autonoma de Madrid, Madrid, Spain
- Fundacion Renal Iñigo Alvarez de Toledo-IRSIN and REDINREN, Madrid, Spain
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24
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Induced pluripotent stem cell-based disease modeling identifies ligand-induced decay of megalin as a cause of Donnai-Barrow syndrome. Kidney Int 2020; 98:159-167. [PMID: 32471643 PMCID: PMC7322522 DOI: 10.1016/j.kint.2020.02.021] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 02/11/2020] [Accepted: 02/13/2020] [Indexed: 01/16/2023]
Abstract
Donnai-Barrow syndrome (DBS) is an autosomal-recessive disorder characterized by multiple pathologies including malformation of forebrain and eyes, as well as resorption defects of the kidney proximal tubule. The underlying cause of DBS are mutations in LRP2, encoding the multifunctional endocytic receptor megalin. Here, we identified a unique missense mutation R3192Q of LRP2 in an affected family that may provide novel insights into the molecular causes of receptor dysfunction in the kidney proximal tubule and other tissues affected in DBS. Using patient-derived induced pluripotent stem cell lines we generated neuroepithelial and kidney cell types as models of the disease. Using these cell models, we documented the inability of megalin R3192Q to properly discharge ligand and ligand-induced receptor decay in lysosomes. Thus, mutant receptors are aberrantly targeted to lysosomes for catabolism, essentially depleting megalin in the presence of ligand in this affected family.
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25
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Protective Role of Vitamin D in Renal Tubulopathies. Metabolites 2020; 10:metabo10030115. [PMID: 32204545 PMCID: PMC7142711 DOI: 10.3390/metabo10030115] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 03/13/2020] [Accepted: 03/17/2020] [Indexed: 02/06/2023] Open
Abstract
Vitamin D is tightly linked with renal tubular homeostasis: the mitochondria of proximal convoluted tubule cells are the production site of 1α,25-dihydroxyvitamin D3. Patients with renal impairment or tubular injury often suffer from chronic inflammation. This alteration comes from oxidative stress, acidosis, decreased clearance of inflammatory cytokines and stimulation of inflammatory factors. The challenge is to find the right formula for each patient to correctly modulate the landscape of treatment and preserve the essential functions of the organism without perturbating its homeostasis. The complexity of the counter-regulation mechanisms and the different axis involved in the Vitamin D equilibrium pose a major issue on Vitamin D as a potential effective anti-inflammatory drug. The therapeutic use of this compound should be able to inhibit the development of inflammation without interfering with normal homeostasis. Megalin-Cubilin-Amnionless and the FGF23-Klotho axis represent two Vitamin D-linked mechanisms that could modulate and ameliorate the damage response at the renal tubular level, balancing Vitamin D therapy with an effect potent enough to contrast the inflammatory cascades, but which avoids potential severe side effects.
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26
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Bedin M, Boyer O, Servais A, Li Y, Villoing-Gaudé L, Tête MJ, Cambier A, Hogan J, Baudouin V, Krid S, Bensman A, Lammens F, Louillet F, Ranchin B, Vigneau C, Bouteau I, Isnard-Bagnis C, Mache CJ, Schäfer T, Pape L, Gödel M, Huber TB, Benz M, Klaus G, Hansen M, Latta K, Gribouval O, Morinière V, Tournant C, Grohmann M, Kuhn E, Wagner T, Bole-Feysot C, Jabot-Hanin F, Nitschké P, Ahluwalia TS, Köttgen A, Andersen CBF, Bergmann C, Antignac C, Simons M. Human C-terminal CUBN variants associate with chronic proteinuria and normal renal function. J Clin Invest 2020. [PMID: 31613795 DOI: 10.1172/jci12937] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/12/2023] Open
Abstract
BACKGROUNDProteinuria is considered an unfavorable clinical condition that accelerates renal and cardiovascular disease. However, it is not clear whether all forms of proteinuria are damaging. Mutations in CUBN cause Imerslund-Gräsbeck syndrome (IGS), which is characterized by intestinal malabsorption of vitamin B12 and in some cases proteinuria. CUBN encodes for cubilin, an intestinal and proximal tubular uptake receptor containing 27 CUB domains for ligand binding.METHODSWe used next-generation sequencing for renal disease genes to genotype cohorts of patients with suspected hereditary renal disease and chronic proteinuria. CUBN variants were analyzed using bioinformatics, structural modeling, and epidemiological methods.RESULTSWe identified 39 patients, in whom biallelic pathogenic variants in the CUBN gene were associated with chronic isolated proteinuria and early childhood onset. Since the proteinuria in these patients had a high proportion of albuminuria, glomerular diseases such as steroid-resistant nephrotic syndrome or Alport syndrome were often the primary clinical diagnosis, motivating renal biopsies and the use of proteinuria-lowering treatments. However, renal function was normal in all cases. By contrast, we did not found any biallelic CUBN variants in proteinuric patients with reduced renal function or focal segmental glomerulosclerosis. Unlike the more N-terminal IGS mutations, 37 of the 41 proteinuria-associated CUBN variants led to modifications or truncations after the vitamin B12-binding domain. Finally, we show that 4 C-terminal CUBN variants are associated with albuminuria and slightly increased GFR in meta-analyses of large population-based cohorts.CONCLUSIONCollectively, our data suggest an important role for the C-terminal half of cubilin in renal albumin reabsorption. Albuminuria due to reduced cubilin function could be an unexpectedly common benign condition in humans that may not require any proteinuria-lowering treatment or renal biopsy.FUNDINGATIP-Avenir program, Fondation Bettencourt-Schueller (Liliane Bettencourt Chair of Developmental Biology), Agence Nationale de la Recherche (ANR) Investissements d'avenir program (ANR-10-IAHU-01) and NEPHROFLY (ANR-14-ACHN-0013, to MS), Steno Collaborative Grant 2018 (NNF18OC0052457, to TSA and MS), Heisenberg Professorship of the German Research Foundation (KO 3598/5-1, to AK), Deutsche Forschungsgemeinschaft (DFG) Collaborative Research Centre (SFB) KIDGEM 1140 (project 246781735, to CB), and Federal Ministry of Education and Research (BMB) (01GM1515C, to CB).
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Affiliation(s)
| | - Olivia Boyer
- Laboratory of Hereditary Kidney Disease, Imagine Institute, INSERM U1163, Université de Paris, Paris, France
- Department of Pediatric Nephrology and
| | - Aude Servais
- Laboratory of Hereditary Kidney Disease, Imagine Institute, INSERM U1163, Université de Paris, Paris, France
- Department of Nephrology, Necker Hospital, Assistance Publique Hôpitaux de Paris (APHP), Paris, France
| | - Yong Li
- Institute of Genetic Epidemiology, Faculty of Medicine and Medical Center, University of Freiburg, Freiburg, Germany
| | | | - Marie-Josephe Tête
- Laboratory of Hereditary Kidney Disease, Imagine Institute, INSERM U1163, Université de Paris, Paris, France
| | - Alexandra Cambier
- Department of Pediatric Nephrology and Transplantation, Robert-Debré Hospital, APHP, Paris, France
| | - Julien Hogan
- Department of Pediatric Nephrology and Transplantation, Robert-Debré Hospital, APHP, Paris, France
| | - Veronique Baudouin
- Department of Pediatric Nephrology and Transplantation, Robert-Debré Hospital, APHP, Paris, France
| | | | | | - Florie Lammens
- Centre Hospitalier Régional Universitaire de Lille, Lille, France
| | | | - Bruno Ranchin
- Department of Pediatric Nephrology, Hospices Civils de Lyon, Bron, France
| | - Cecile Vigneau
- Centre Hospitalier Universitaire de Rennes, INSERM U1085 IRSET-9, Rennes, France
| | - Iseline Bouteau
- Centre Hospitalier Universitaire de Poitiers, Poitiers, France
| | | | | | - Tobias Schäfer
- Renal Division, University Medical Center Freiburg, Freiburg, Germany
| | - Lars Pape
- Department of Pediatric Kidney, Liver and Metabolic Disease, Hannover Medical School, Hannover, Germany
| | - Markus Gödel
- Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Tobias B Huber
- Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | | | - Günter Klaus
- Department of Child and Adolescent Medicine, University Medical Center Marburg-Giessen, Marburg, Germany
| | - Matthias Hansen
- KfH-Nierenzentrum für Kinder und Jugendliche und Clementine-Kinderhospital, Frankfurt, Germany
| | - Kay Latta
- KfH-Nierenzentrum für Kinder und Jugendliche und Clementine-Kinderhospital, Frankfurt, Germany
| | - Olivier Gribouval
- Laboratory of Hereditary Kidney Disease, Imagine Institute, INSERM U1163, Université de Paris, Paris, France
| | | | - Carole Tournant
- Department of Genetics, Necker Hospital, APHP, Paris, France
| | - Maik Grohmann
- Center for Human Genetics, Bioscientia, Ingelheim, Germany
- Center for Human Genetics, Mainz, Germany
| | - Elisa Kuhn
- Center for Human Genetics, Bioscientia, Ingelheim, Germany
| | - Timo Wagner
- Center for Human Genetics, Bioscientia, Ingelheim, Germany
| | - Christine Bole-Feysot
- Bioinformatic Platform, INSERM UMR 1163, Institut Imagine, Paris, France
- Bioinformatics Core Facility, Structure Fédérative de Recherche Necker, INSERM US24/CNRS UMS3633, Université de Paris, Paris, France
| | - Fabienne Jabot-Hanin
- Bioinformatic Platform, INSERM UMR 1163, Institut Imagine, Paris, France
- Bioinformatics Core Facility, Structure Fédérative de Recherche Necker, INSERM US24/CNRS UMS3633, Université de Paris, Paris, France
| | - Patrick Nitschké
- Bioinformatic Platform, INSERM UMR 1163, Institut Imagine, Paris, France
- Bioinformatics Core Facility, Structure Fédérative de Recherche Necker, INSERM US24/CNRS UMS3633, Université de Paris, Paris, France
| | | | - Anna Köttgen
- Institute of Genetic Epidemiology, Faculty of Medicine and Medical Center, University of Freiburg, Freiburg, Germany
| | | | - Carsten Bergmann
- Center for Human Genetics, Bioscientia, Ingelheim, Germany
- Center for Human Genetics, Mainz, Germany
- Renal Division, Department of Medicine, University Hospital Freiburg, Freiburg, Germany
| | - Corinne Antignac
- Laboratory of Hereditary Kidney Disease, Imagine Institute, INSERM U1163, Université de Paris, Paris, France
- Department of Genetics, Necker Hospital, APHP, Paris, France
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27
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Rangarajan S, Rezonzew G, Chumley P, Fatima H, Golovko MY, Feng W, Hua P, Jaimes EA. COX-2-derived prostaglandins as mediators of the deleterious effects of nicotine in chronic kidney disease. Am J Physiol Renal Physiol 2019; 318:F475-F485. [PMID: 31841390 DOI: 10.1152/ajprenal.00407.2019] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Tobacco smoking has been identified as a risk factor in the progression of chronic kidney disease (CKD). In previous studies, we showed that nicotine induces cyclooxygenase (COX)-2 expression in vivo and in vitro and that the administration of nicotine in vivo worsens the severity of renal injury in a model of subtotal renal ablation. In the present study, we tested the role of COX-2-derived prostaglandins on the deleterious effects of nicotine in CKD. Sham and 5/6 nephrectomy (5/6Nx) rats received tap water or nicotine (100 μg/mL) in the drinking water for 12 wk. Additional groups also systemically received the COX-2 inhibitor NS-398 (1.5 mg·kg-1·day-1 via osmotic minipump). The administration of nicotine worsened renal injury and proteinuria in 5/6Nx rats and increased proteinuria in sham rats. 5/6Nx rats had increased cortical production of the prostaglandins PGE2, PGI2, PGD2, and PGF2α and of thromboxane A2. In these rats, nicotine reduced the production of all prostaglandins examined except thromboxane A2. Treatment with the COX-2 inhibitor NS-398 resulted in complete inhibition of all prostaglandins studied and ameliorated renal injury and proteinuria in 5/6Nx rats on nicotine but not in 5/6 Nx rats on tap water. Nicotine also reduced the expression of megalin in all groups examined, and this was partially prevented by COX-2 inhibition. In the present study, we showed that in CKD, nicotine worsens renal injury at least in part by producing an imbalance in the production of prostaglandins. This imbalance in the production of prostaglandins likely plays a role in the deleterious effects of smoking on the progression of CKD.
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Affiliation(s)
- S Rangarajan
- Renal Division, University of Alabama at Birmingham, Birmingham, Alabama
| | - G Rezonzew
- Renal Division, University of Alabama at Birmingham, Birmingham, Alabama
| | - P Chumley
- Renal Division, University of Alabama at Birmingham, Birmingham, Alabama
| | - H Fatima
- Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama
| | - M Y Golovko
- Department of Biomedical Sciences, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota
| | - W Feng
- Renal Division, University of Alabama at Birmingham, Birmingham, Alabama
| | - P Hua
- Renal Division, University of Alabama at Birmingham, Birmingham, Alabama
| | - E A Jaimes
- Renal Service, Memorial Sloan Kettering Cancer Center and Weill Cornell Medical College, New York, New York
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28
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van der Wijst J, Belge H, Bindels RJM, Devuyst O. Learning Physiology From Inherited Kidney Disorders. Physiol Rev 2019; 99:1575-1653. [PMID: 31215303 DOI: 10.1152/physrev.00008.2018] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The identification of genes causing inherited kidney diseases yielded crucial insights in the molecular basis of disease and improved our understanding of physiological processes that operate in the kidney. Monogenic kidney disorders are caused by mutations in genes coding for a large variety of proteins including receptors, channels and transporters, enzymes, transcription factors, and structural components, operating in specialized cell types that perform highly regulated homeostatic functions. Common variants in some of these genes are also associated with complex traits, as evidenced by genome-wide association studies in the general population. In this review, we discuss how the molecular genetics of inherited disorders affecting different tubular segments of the nephron improved our understanding of various transport processes and of their involvement in homeostasis, while providing novel therapeutic targets. These include inherited disorders causing a dysfunction of the proximal tubule (renal Fanconi syndrome), with emphasis on epithelial differentiation and receptor-mediated endocytosis, or affecting the reabsorption of glucose, the handling of uric acid, and the reabsorption of sodium, calcium, and magnesium along the kidney tubule.
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Affiliation(s)
- Jenny van der Wijst
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center , Nijmegen , The Netherlands ; Institute of Physiology, University of Zurich , Zurich , Switzerland ; and Division of Nephrology, Institute of Experimental and Clinical Research (IREC), Medical School, Université catholique de Louvain, Brussels, Belgium
| | - Hendrica Belge
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center , Nijmegen , The Netherlands ; Institute of Physiology, University of Zurich , Zurich , Switzerland ; and Division of Nephrology, Institute of Experimental and Clinical Research (IREC), Medical School, Université catholique de Louvain, Brussels, Belgium
| | - René J M Bindels
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center , Nijmegen , The Netherlands ; Institute of Physiology, University of Zurich , Zurich , Switzerland ; and Division of Nephrology, Institute of Experimental and Clinical Research (IREC), Medical School, Université catholique de Louvain, Brussels, Belgium
| | - Olivier Devuyst
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center , Nijmegen , The Netherlands ; Institute of Physiology, University of Zurich , Zurich , Switzerland ; and Division of Nephrology, Institute of Experimental and Clinical Research (IREC), Medical School, Université catholique de Louvain, Brussels, Belgium
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29
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Jayasinghe K, White SM, Kerr PG, MacGregor D, Stark Z, Wilkins E, Simons C, Mallett A, Quinlan C. Isolated proteinuria due to CUBN homozygous mutation - challenging the investigative paradigm. BMC Nephrol 2019; 20:330. [PMID: 31438875 PMCID: PMC6704575 DOI: 10.1186/s12882-019-1474-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2019] [Accepted: 07/19/2019] [Indexed: 11/25/2022] Open
Abstract
Background Proteinuria is a common clinical presentation, the diagnostic workup for which involves many non-invasive and invasive investigations. We report on two siblings that highlight the clinically relevant functional role of cubulin for albumin resorption in the proximal tubule and supports the use of genomic sequencing early in the diagnostic work up of patients who present with proteinuria. Case presentation An 8-year-old boy was referred with an incidental finding of proteinuria. All preliminary investigations were unremarkable. Further assessment revealed consanguineous family history and a brother with isolated proteinuria. Renal biopsy demonstrated normal light microscopy and global glomerular basement membrane thinning on electron microscopy. Chromosomal microarray revealed long continuous stretches of homozygosity (LCSH) representing ~ 4.5% of the genome. Shared regions of LCSH between the brothers were identified and their further research genomic analysis implicated a homozygous stop-gain variant in CUBN (10p12.31). Conclusions CUBN mutations have been implicated as a hereditary cause of megaloblastic anaemia and variable proteinuria. This is the second reported family with isolated proteinuria due to biallelic CUBN variants in the absence of megaloblastic anaemia, demonstrating the ability of genomic testing to identify genetic causes of nephropathy within expanding associated phenotypic spectra. Genomic sequencing, undertaken earlier in the diagnostic trajectory, may reduce the need for invasive investigations and the time to definitive diagnosis for patients and families.
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Affiliation(s)
- Kushani Jayasinghe
- Department of Nephrology, Monash Medical Centre, Melbourne, Australia.,Monash University, Melbourne, Australia.,Murdoch Children's Research Institute, Melbourne, Australia.,The KidGen Collaborative, Australian Genomics Health Alliance, Victoria, Australia
| | - Susan M White
- The KidGen Collaborative, Australian Genomics Health Alliance, Victoria, Australia.,Department of Paediatrics, University of Melbourne, Victoria, Australia.,Victorian Clinical Genetics Services, Murdoch Children's Research Institute, Melbourne, Australia
| | - Peter G Kerr
- Department of Nephrology, Monash Medical Centre, Melbourne, Australia.,Monash University, Melbourne, Australia
| | - Duncan MacGregor
- Department of Pathology, Royal Children's Hospital, Melbourne, Australia
| | - Zornitza Stark
- Murdoch Children's Research Institute, Melbourne, Australia.,The KidGen Collaborative, Australian Genomics Health Alliance, Victoria, Australia.,Department of Paediatrics, University of Melbourne, Victoria, Australia.,Victorian Clinical Genetics Services, Murdoch Children's Research Institute, Melbourne, Australia
| | - Ella Wilkins
- Murdoch Children's Research Institute, Melbourne, Australia.,The KidGen Collaborative, Australian Genomics Health Alliance, Victoria, Australia.,Victorian Clinical Genetics Services, Murdoch Children's Research Institute, Melbourne, Australia
| | - Cas Simons
- Murdoch Children's Research Institute, Melbourne, Australia.,The KidGen Collaborative, Australian Genomics Health Alliance, Victoria, Australia
| | - Andrew Mallett
- Murdoch Children's Research Institute, Melbourne, Australia.,The KidGen Collaborative, Australian Genomics Health Alliance, Victoria, Australia.,Kidney Health Service and Conjoint Renal Research Laboratory, Royal Brisbane and Women's Hospital, Brisbane, Australia.,Institute for Molecular Bioscience and Faculty of Medicine, The University of Queensland, Brisbane, Australia
| | - Catherine Quinlan
- Murdoch Children's Research Institute, Melbourne, Australia. .,The KidGen Collaborative, Australian Genomics Health Alliance, Victoria, Australia. .,Department of Paediatric Nephrology, Royal Children's Hospital, 50 Flemington Street, Parkville, Australia.
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30
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Pyzik M, Sand KMK, Hubbard JJ, Andersen JT, Sandlie I, Blumberg RS. The Neonatal Fc Receptor (FcRn): A Misnomer? Front Immunol 2019; 10:1540. [PMID: 31354709 PMCID: PMC6636548 DOI: 10.3389/fimmu.2019.01540] [Citation(s) in RCA: 237] [Impact Index Per Article: 47.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Accepted: 06/20/2019] [Indexed: 12/13/2022] Open
Abstract
Antibodies are essential components of an adaptive immune response. Immunoglobulin G (IgG) is the most common type of antibody found in circulation and extracellular fluids. Although IgG alone can directly protect the body from infection through the activities of its antigen binding region, the majority of IgG immune functions are mediated via proteins and receptors expressed by specialized cell subsets that bind to the fragment crystallizable (Fc) region of IgG. Fc gamma (γ) receptors (FcγR) belong to a broad family of proteins that presently include classical membrane-bound surface receptors as well as atypical intracellular receptors and cytoplasmic glycoproteins. Among the atypical FcγRs, the neonatal Fc receptor (FcRn) has increasingly gained notoriety given its intimate influence on IgG biology and its ability to also bind to albumin. FcRn functions as a recycling or transcytosis receptor that is responsible for maintaining IgG and albumin in the circulation, and bidirectionally transporting these two ligands across polarized cellular barriers. More recently, it has been appreciated that FcRn acts as an immune receptor by interacting with and facilitating antigen presentation of peptides derived from IgG immune complexes (IC). Here we review FcRn biology and focus on newer advances including how emerging FcRn-targeted therapies may affect the immune responses to IgG and IgG IC.
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Affiliation(s)
- Michal Pyzik
- Division of Gastroenterology, Hepatology and Endoscopy, Department of Medicine, Harvard Medical School, Brigham and Women's Hospital, Boston, MA, United States
| | - Kine M K Sand
- Division of Gastroenterology, Hepatology and Endoscopy, Department of Medicine, Harvard Medical School, Brigham and Women's Hospital, Boston, MA, United States.,Department of Biosciences, University of Oslo, Oslo, Norway
| | - Jonathan J Hubbard
- Division of Gastroenterology, Hepatology and Endoscopy, Department of Medicine, Harvard Medical School, Brigham and Women's Hospital, Boston, MA, United States.,Division of Gastroenterology, Hepatology and Nutrition, Department of Pediatrics, Harvard Medical School, Boston Children's Hospital, Boston, MA, United States
| | - Jan Terje Andersen
- Department of Immunology, Oslo University Hospital Rikshospitalet, Oslo, Norway.,Department of Pharmacology, Institute of Clinical Medicine, University of Oslo and Oslo University Hospital, Oslo, Norway
| | - Inger Sandlie
- Department of Biosciences, University of Oslo, Oslo, Norway
| | - Richard S Blumberg
- Division of Gastroenterology, Hepatology and Endoscopy, Department of Medicine, Harvard Medical School, Brigham and Women's Hospital, Boston, MA, United States.,Harvard Digestive Diseases Center, Boston, MA, United States
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31
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Lenhard SC, McAlexander A, Virtue A, Fieles W, Skedzielewski T, Rambo M, Trinh H, Cheng SH, Hong H, Isidro-Llobet A, Nadin A, Geske R, Klein JL, Lee D, Jucker BM, Hu E. In Vivo Imaging of Small Molecular Weight Peptides for Targeted Renal Drug Delivery: A Study in Normal and Polycystic Kidney Diseased Mice. J Pharmacol Exp Ther 2019; 370:786-795. [PMID: 30936291 DOI: 10.1124/jpet.119.257022] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Accepted: 03/18/2019] [Indexed: 12/15/2022] Open
Affiliation(s)
- Stephen C Lenhard
- Bioimaging (S.C.L., T.S., M.R., S.-H.C., H.H., B.M.J.), Renal Discovery Group, Future Pipeline Discovery (A.V, E.H.), Experimental Cell and Tissue Biology, Target and Pathway Validation (W.F., H.T., R.G., J.-L.K.), Drug Delivery (A.M., D.L.), and Drug Design and Selection (A.I.-L., A.N.), GlaxoSmithKline plc, Collegeville, Pennsylvania
| | - Allen McAlexander
- Bioimaging (S.C.L., T.S., M.R., S.-H.C., H.H., B.M.J.), Renal Discovery Group, Future Pipeline Discovery (A.V, E.H.), Experimental Cell and Tissue Biology, Target and Pathway Validation (W.F., H.T., R.G., J.-L.K.), Drug Delivery (A.M., D.L.), and Drug Design and Selection (A.I.-L., A.N.), GlaxoSmithKline plc, Collegeville, Pennsylvania
| | - Anthony Virtue
- Bioimaging (S.C.L., T.S., M.R., S.-H.C., H.H., B.M.J.), Renal Discovery Group, Future Pipeline Discovery (A.V, E.H.), Experimental Cell and Tissue Biology, Target and Pathway Validation (W.F., H.T., R.G., J.-L.K.), Drug Delivery (A.M., D.L.), and Drug Design and Selection (A.I.-L., A.N.), GlaxoSmithKline plc, Collegeville, Pennsylvania
| | - William Fieles
- Bioimaging (S.C.L., T.S., M.R., S.-H.C., H.H., B.M.J.), Renal Discovery Group, Future Pipeline Discovery (A.V, E.H.), Experimental Cell and Tissue Biology, Target and Pathway Validation (W.F., H.T., R.G., J.-L.K.), Drug Delivery (A.M., D.L.), and Drug Design and Selection (A.I.-L., A.N.), GlaxoSmithKline plc, Collegeville, Pennsylvania
| | - Tina Skedzielewski
- Bioimaging (S.C.L., T.S., M.R., S.-H.C., H.H., B.M.J.), Renal Discovery Group, Future Pipeline Discovery (A.V, E.H.), Experimental Cell and Tissue Biology, Target and Pathway Validation (W.F., H.T., R.G., J.-L.K.), Drug Delivery (A.M., D.L.), and Drug Design and Selection (A.I.-L., A.N.), GlaxoSmithKline plc, Collegeville, Pennsylvania
| | - Mary Rambo
- Bioimaging (S.C.L., T.S., M.R., S.-H.C., H.H., B.M.J.), Renal Discovery Group, Future Pipeline Discovery (A.V, E.H.), Experimental Cell and Tissue Biology, Target and Pathway Validation (W.F., H.T., R.G., J.-L.K.), Drug Delivery (A.M., D.L.), and Drug Design and Selection (A.I.-L., A.N.), GlaxoSmithKline plc, Collegeville, Pennsylvania
| | - Han Trinh
- Bioimaging (S.C.L., T.S., M.R., S.-H.C., H.H., B.M.J.), Renal Discovery Group, Future Pipeline Discovery (A.V, E.H.), Experimental Cell and Tissue Biology, Target and Pathway Validation (W.F., H.T., R.G., J.-L.K.), Drug Delivery (A.M., D.L.), and Drug Design and Selection (A.I.-L., A.N.), GlaxoSmithKline plc, Collegeville, Pennsylvania
| | - Shih-Hsun Cheng
- Bioimaging (S.C.L., T.S., M.R., S.-H.C., H.H., B.M.J.), Renal Discovery Group, Future Pipeline Discovery (A.V, E.H.), Experimental Cell and Tissue Biology, Target and Pathway Validation (W.F., H.T., R.G., J.-L.K.), Drug Delivery (A.M., D.L.), and Drug Design and Selection (A.I.-L., A.N.), GlaxoSmithKline plc, Collegeville, Pennsylvania
| | - Hyundae Hong
- Bioimaging (S.C.L., T.S., M.R., S.-H.C., H.H., B.M.J.), Renal Discovery Group, Future Pipeline Discovery (A.V, E.H.), Experimental Cell and Tissue Biology, Target and Pathway Validation (W.F., H.T., R.G., J.-L.K.), Drug Delivery (A.M., D.L.), and Drug Design and Selection (A.I.-L., A.N.), GlaxoSmithKline plc, Collegeville, Pennsylvania
| | - Albert Isidro-Llobet
- Bioimaging (S.C.L., T.S., M.R., S.-H.C., H.H., B.M.J.), Renal Discovery Group, Future Pipeline Discovery (A.V, E.H.), Experimental Cell and Tissue Biology, Target and Pathway Validation (W.F., H.T., R.G., J.-L.K.), Drug Delivery (A.M., D.L.), and Drug Design and Selection (A.I.-L., A.N.), GlaxoSmithKline plc, Collegeville, Pennsylvania
| | - Alan Nadin
- Bioimaging (S.C.L., T.S., M.R., S.-H.C., H.H., B.M.J.), Renal Discovery Group, Future Pipeline Discovery (A.V, E.H.), Experimental Cell and Tissue Biology, Target and Pathway Validation (W.F., H.T., R.G., J.-L.K.), Drug Delivery (A.M., D.L.), and Drug Design and Selection (A.I.-L., A.N.), GlaxoSmithKline plc, Collegeville, Pennsylvania
| | - Robert Geske
- Bioimaging (S.C.L., T.S., M.R., S.-H.C., H.H., B.M.J.), Renal Discovery Group, Future Pipeline Discovery (A.V, E.H.), Experimental Cell and Tissue Biology, Target and Pathway Validation (W.F., H.T., R.G., J.-L.K.), Drug Delivery (A.M., D.L.), and Drug Design and Selection (A.I.-L., A.N.), GlaxoSmithKline plc, Collegeville, Pennsylvania
| | - Jean-Louis Klein
- Bioimaging (S.C.L., T.S., M.R., S.-H.C., H.H., B.M.J.), Renal Discovery Group, Future Pipeline Discovery (A.V, E.H.), Experimental Cell and Tissue Biology, Target and Pathway Validation (W.F., H.T., R.G., J.-L.K.), Drug Delivery (A.M., D.L.), and Drug Design and Selection (A.I.-L., A.N.), GlaxoSmithKline plc, Collegeville, Pennsylvania
| | - Dennis Lee
- Bioimaging (S.C.L., T.S., M.R., S.-H.C., H.H., B.M.J.), Renal Discovery Group, Future Pipeline Discovery (A.V, E.H.), Experimental Cell and Tissue Biology, Target and Pathway Validation (W.F., H.T., R.G., J.-L.K.), Drug Delivery (A.M., D.L.), and Drug Design and Selection (A.I.-L., A.N.), GlaxoSmithKline plc, Collegeville, Pennsylvania
| | - Beat M Jucker
- Bioimaging (S.C.L., T.S., M.R., S.-H.C., H.H., B.M.J.), Renal Discovery Group, Future Pipeline Discovery (A.V, E.H.), Experimental Cell and Tissue Biology, Target and Pathway Validation (W.F., H.T., R.G., J.-L.K.), Drug Delivery (A.M., D.L.), and Drug Design and Selection (A.I.-L., A.N.), GlaxoSmithKline plc, Collegeville, Pennsylvania
| | - Erding Hu
- Bioimaging (S.C.L., T.S., M.R., S.-H.C., H.H., B.M.J.), Renal Discovery Group, Future Pipeline Discovery (A.V, E.H.), Experimental Cell and Tissue Biology, Target and Pathway Validation (W.F., H.T., R.G., J.-L.K.), Drug Delivery (A.M., D.L.), and Drug Design and Selection (A.I.-L., A.N.), GlaxoSmithKline plc, Collegeville, Pennsylvania
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32
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Immature megalin expression in the preterm neonatal kidney is associated with urinary loss of vitamin carrier proteins. Pediatr Res 2019; 85:405-411. [PMID: 30659269 DOI: 10.1038/s41390-018-0261-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2018] [Revised: 11/15/2018] [Accepted: 11/30/2018] [Indexed: 01/19/2023]
Abstract
BACKGROUND Vitamin A and D deficiencies are common in preterm infants. Megalin is an endocytic receptor in the proximal tubule, which reabsorbs retinol-binding protein (RBP) and vitamin D-binding protein (VDBP). Although the proximal tubule is immature in preterm infants, little is known about megalin expression during kidney development. In this study, we establish the abundance of megalin in the developing human kidney and its relationship to the urinary excretion of vitamin carriers in preterm infants. METHODS We analyzed a postmortem group (20-40 weeks gestation), where we used morphometric means of measuring megalin and its ligands in kidney tissue and a living group of patients (28-40 weeks), where urinary RBP and VDBP were measured. RESULTS The presence of megalin, RBP, and VDBP increased in the proximal tubule through gestation. At birth the urinary concentration of RBP and VDBP were higher in the 28-32 week group compared to the 38-40 week group and a significant inverse correlation of tissue megalin and urinary loss of RBP and VDBP existed. CONCLUSIONS Preterm infants experience vitamin carrier protein losses, which are associated with decreased megalin expression. This developmental expression of megalin in the kidney has clinical implications in the prevention of vitamin deficiencies in preterm babies.
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33
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Liu D, Lv LL. New Understanding on the Role of Proteinuria in Progression of Chronic Kidney Disease. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1165:487-500. [PMID: 31399981 DOI: 10.1007/978-981-13-8871-2_24] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Proteinuria is identified as an important marker and risk factor of progression in chronic kidney disease. However, the precise mechanism of action in the progress of chronic kidney disease is still unclear. Mesangial toxicity from specific filtered compounds such as albumin-bound fatty acids and transferrin/iron, tubular overload and hyperplasia, and induction of proinflammatory molecules such as MCP-1 and inflammatory cytokines are some of the proposed mechanisms. Reversing intraglomerular hypertension with protein restriction or antihypertensive therapy may be beneficial both by diminishing hemodynamic injury to the glomeruli and by reducing protein filtration. Therefore, understanding proteinuria and its role in renal tubular interstitial inflammation and fibrosis is of great significance for the study of renal protective therapy, such as antiproteinuric treatments, and delaying the progression of chronic renal disease.
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Affiliation(s)
- Dan Liu
- Institute of Nephrology, Zhong Da Hospital, Southeast University School of Medicine, Nanjing, China
| | - Lin-Li Lv
- Institute of Nephrology, Zhong Da Hospital, Southeast University School of Medicine, Nanjing, China.
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34
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Li Q, Lei F, Tang Y, Pan JSC, Tong Q, Sun Y, Sheikh-Hamad D. Megalin mediates plasma membrane to mitochondria cross-talk and regulates mitochondrial metabolism. Cell Mol Life Sci 2018; 75:4021-4040. [PMID: 29916093 PMCID: PMC11105752 DOI: 10.1007/s00018-018-2847-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Revised: 05/01/2018] [Accepted: 05/28/2018] [Indexed: 01/21/2023]
Abstract
Mitochondrial intracrines are extracellular signaling proteins, targeted to the mitochondria. The pathway for mitochondrial targeting of mitochondrial intracrines and actions in the mitochondria remains unknown. Megalin/LRP2 mediates the uptake of vitamins and proteins, and is critical for clearance of amyloid-β protein from the brain. Megalin mutations underlie the pathogenesis of Donnai-Barrow and Lowe syndromes, characterized by brain defects and kidney dysfunction; megalin was not previously known to reside in the mitochondria. Here, we show megalin is present in the mitochondria and associates with mitochondrial anti-oxidant proteins SIRT3 and stanniocalcin-1 (STC1). Megalin shuttles extracellularly-applied STC1, angiotensin II and TGF-β to the mitochondria through the retrograde early endosome-to-Golgi transport pathway and Rab32. Megalin knockout in cultured cells impairs glycolytic and respiratory capacities. Thus, megalin is critical for mitochondrial biology; mitochondrial intracrine signaling is a continuum of the retrograde early endosome-to-Golgi-Rab32 pathway and defects in this pathway may underlie disease processes in many systems.
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MESH Headings
- Agenesis of Corpus Callosum/genetics
- Agenesis of Corpus Callosum/metabolism
- Agenesis of Corpus Callosum/pathology
- Amyloid beta-Peptides/genetics
- Amyloid beta-Peptides/metabolism
- Animals
- Brain/metabolism
- Brain/pathology
- Cell Membrane/genetics
- Glycoproteins/genetics
- HEK293 Cells
- Hearing Loss, Sensorineural/genetics
- Hearing Loss, Sensorineural/metabolism
- Hearing Loss, Sensorineural/pathology
- Hernias, Diaphragmatic, Congenital/genetics
- Hernias, Diaphragmatic, Congenital/metabolism
- Hernias, Diaphragmatic, Congenital/pathology
- Humans
- Low Density Lipoprotein Receptor-Related Protein-2/genetics
- Low Density Lipoprotein Receptor-Related Protein-2/metabolism
- Mice
- Mitochondria/genetics
- Mitochondria/metabolism
- Myopia/genetics
- Myopia/metabolism
- Myopia/pathology
- Oculocerebrorenal Syndrome/genetics
- Oculocerebrorenal Syndrome/metabolism
- Oculocerebrorenal Syndrome/pathology
- Proteinuria/genetics
- Proteinuria/metabolism
- Proteinuria/pathology
- RAW 264.7 Cells
- Renal Tubular Transport, Inborn Errors/genetics
- Renal Tubular Transport, Inborn Errors/metabolism
- Renal Tubular Transport, Inborn Errors/pathology
- Signal Transduction
- Sirtuin 3/genetics
- Transforming Growth Factor beta/genetics
- rab GTP-Binding Proteins/genetics
- rab GTP-Binding Proteins/metabolism
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Affiliation(s)
- Qingtian Li
- Division of Nephrology, Department of Medicine, Selzman Institute for Kidney Health, Baylor College of Medicine, One Baylor Plaza, ABBR R706, M/S BCM395, Houston, TX, 77030-3498, USA
| | - Fan Lei
- Division of Nephrology, Department of Medicine, Selzman Institute for Kidney Health, Baylor College of Medicine, One Baylor Plaza, ABBR R706, M/S BCM395, Houston, TX, 77030-3498, USA
- Renmin Hospital of Wuhan University, Wuhan, Hubei, People's Republic of China
| | - Yi Tang
- Division of Nephrology, Department of Medicine, Selzman Institute for Kidney Health, Baylor College of Medicine, One Baylor Plaza, ABBR R706, M/S BCM395, Houston, TX, 77030-3498, USA
- West China Medical Center of Sichuan University, Chengdu, Sichuan, People's Republic of China
| | - Jenny Szu-Chin Pan
- Division of Nephrology, Department of Medicine, Selzman Institute for Kidney Health, Baylor College of Medicine, One Baylor Plaza, ABBR R706, M/S BCM395, Houston, TX, 77030-3498, USA
| | - Qiang Tong
- Children's Nutrition Research Center, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Yuxiang Sun
- Department of Nutrition and Food Science (NFSC), Texas A&M University, College Station, TX, 77843, USA
| | - David Sheikh-Hamad
- Division of Nephrology, Department of Medicine, Selzman Institute for Kidney Health, Baylor College of Medicine, One Baylor Plaza, ABBR R706, M/S BCM395, Houston, TX, 77030-3498, USA.
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35
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Zanoni P, Velagapudi S, Yalcinkaya M, Rohrer L, von Eckardstein A. Endocytosis of lipoproteins. Atherosclerosis 2018; 275:273-295. [PMID: 29980055 DOI: 10.1016/j.atherosclerosis.2018.06.881] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 06/04/2018] [Accepted: 06/22/2018] [Indexed: 02/06/2023]
Abstract
During their metabolism, all lipoproteins undergo endocytosis, either to be degraded intracellularly, for example in hepatocytes or macrophages, or to be re-secreted, for example in the course of transcytosis by endothelial cells. Moreover, there are several examples of internalized lipoproteins sequestered intracellularly, possibly to exert intracellular functions, for example the cytolysis of trypanosoma. Endocytosis and the subsequent intracellular itinerary of lipoproteins hence are key areas for understanding the regulation of plasma lipid levels as well as the biological functions of lipoproteins. Indeed, the identification of the low-density lipoprotein (LDL)-receptor and the unraveling of its transcriptional regulation led to the elucidation of familial hypercholesterolemia as well as to the development of statins, the most successful therapeutics for lowering of cholesterol levels and risk of atherosclerotic cardiovascular diseases. Novel limiting factors of intracellular trafficking of LDL and the LDL receptor continue to be discovered and to provide drug targets such as PCSK9. Surprisingly, the receptors mediating endocytosis of high-density lipoproteins or lipoprotein(a) are still a matter of controversy or even new discovery. Finally, the receptors and mechanisms, which mediate the uptake of lipoproteins into non-degrading intracellular itineraries for re-secretion (transcytosis, retroendocytosis), storage, or execution of intracellular functions, are largely unknown.
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Affiliation(s)
- Paolo Zanoni
- Institute for Clinical Chemistry, University and University Hospital Zurich, Zurich, Switzerland; Centre for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Srividya Velagapudi
- Institute for Clinical Chemistry, University and University Hospital Zurich, Zurich, Switzerland; Centre for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Mustafa Yalcinkaya
- Institute for Clinical Chemistry, University and University Hospital Zurich, Zurich, Switzerland; Centre for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Lucia Rohrer
- Institute for Clinical Chemistry, University and University Hospital Zurich, Zurich, Switzerland; Centre for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Arnold von Eckardstein
- Institute for Clinical Chemistry, University and University Hospital Zurich, Zurich, Switzerland; Centre for Integrative Human Physiology, University of Zurich, Zurich, Switzerland.
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36
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Salihu S, Tosheska K, Aluloska N, Gucev Z, Cekovska S, Tasic V. The Spectrum of Kidney Diseases in Children Associated with Low Molecular Weight Proteinuria. Open Access Maced J Med Sci 2018; 6:814-819. [PMID: 29875851 PMCID: PMC5985860 DOI: 10.3889/oamjms.2018.221] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Revised: 04/23/2018] [Accepted: 04/30/2018] [Indexed: 11/05/2022] Open
Abstract
BACKGROUND Proteinuria, in addition to haematuria, is the most important laboratory parameter in patients with nephro-urological diseases. Low molecular weight proteinuria (LMWP) is of particular importance because some diseases genetic and tubulointerstitial are diagnosed based on its presence. AIM The purpose of this study is to describe the clinical features, the course and outcome of pediatric patients with a renal disease associated with LMWP. MATERIAL AND METHODS This retrospective observational study included 250 pediatric patients with various kidney diseases in which the type of proteinuria was defined by 4-20% gradient gel sodium dodecyl sulphate polyacrylamide gel (SDS-PAG) electrophoresis. RESULTS Isolated LMWP was detected in 12% of patients, while mixed glomerulotubular proteinuria was detected in 18% of patients. It was detected in all patients with the Dent-1/2 disease, Lowe's syndrome and secondary Fanconi syndrome. Transient LMWP was also detected in a series of 12 patients with distal renal tubular acidosis. In patients with nephrotic syndrome, it was associated with corticoresistence and unfavourable clinical course. CONCLUSION This study contributes to the understanding of the clinical spectrum of various kidney diseases associated with LMWP, their natural course, and the effect of therapy.
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Affiliation(s)
- Shpetim Salihu
- Department of Neonatology, University Clinical Center, Prishtina, Kosovo
| | - Katerina Tosheska
- Institute of Medical and Experimental Biochemistry, Medical Faculty, Ss Cyril and Methodius University of Skopje, Skopje, Republic of Macedonia
| | - Natasa Aluloska
- University Children's Hospital, Medical Faculty, Ss Cyril and Methodius University of Skopje, Skopje, Republic of Macedonia
| | - Zoran Gucev
- University Children's Hospital, Medical Faculty, Ss Cyril and Methodius University of Skopje, Skopje, Republic of Macedonia
| | - Svetlana Cekovska
- Institute of Medical and Experimental Biochemistry, Medical Faculty, Ss Cyril and Methodius University of Skopje, Skopje, Republic of Macedonia
| | - Velibor Tasic
- University Children's Hospital, Medical Faculty, Ss Cyril and Methodius University of Skopje, Skopje, Republic of Macedonia
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37
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Cil O, Perwad F. Monogenic Causes of Proteinuria in Children. Front Med (Lausanne) 2018; 5:55. [PMID: 29594119 PMCID: PMC5858124 DOI: 10.3389/fmed.2018.00055] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Accepted: 02/15/2018] [Indexed: 01/02/2023] Open
Abstract
Glomerular disease is a common cause for proteinuria and chronic kidney disease leading to end-stage renal disease requiring dialysis or kidney transplantation in children. Nephrotic syndrome in children is diagnosed by the presence of a triad of proteinuria, hypoalbuminemia, and edema. Minimal change disease is the most common histopathological finding in children and adolescents with nephrotic syndrome. Focal segmental sclerosis is also found in children and is the most common pathological finding in patients with monogenic causes of nephrotic syndrome. Current classification system for nephrotic syndrome is based on response to steroid therapy as a majority of patients develop steroid sensitive nephrotic syndrome regardless of histopathological diagnosis or the presence of genetic mutations. Recent studies investigating the genetics of nephrotic syndrome have shed light on the pathophysiology and mechanisms of proteinuria in nephrotic syndrome. Gene mutations have been identified in several subcellular compartments of the glomerular podocyte and play a critical role in mitochondrial function, actin cytoskeleton dynamics, cell-matrix interactions, slit diaphragm, and podocyte integrity. A subset of genetic mutations are known to cause nephrotic syndrome that is responsive to immunosuppressive therapy but clinical data are limited with respect to renal prognosis and disease progression in a majority of patients. To date, more than 50 genes have been identified as causative factors in nephrotic syndrome in children and adults. As genetic testing becomes more prevalent and affordable, we expect rapid advances in our understanding of mechanisms of proteinuria and genetic diagnosis will help direct future therapy for individual patients.
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Affiliation(s)
- Onur Cil
- Department of Pediatrics, Division of Nephrology, University of California San Francisco, San Francisco, CA, United States
| | - Farzana Perwad
- Department of Pediatrics, Division of Nephrology, University of California San Francisco, San Francisco, CA, United States
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38
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Zeng B, Chen GL, Garcia-Vaz E, Bhandari S, Daskoulidou N, Berglund LM, Jiang H, Hallett T, Zhou LP, Huang L, Xu ZH, Nair V, Nelson RG, Ju W, Kretzler M, Atkin SL, Gomez MF, Xu SZ. ORAI channels are critical for receptor-mediated endocytosis of albumin. Nat Commun 2017; 8:1920. [PMID: 29203863 PMCID: PMC5714946 DOI: 10.1038/s41467-017-02094-y] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Accepted: 11/06/2017] [Indexed: 01/15/2023] Open
Abstract
Impaired albumin reabsorption by proximal tubular epithelial cells (PTECs) has been highlighted in diabetic nephropathy (DN), but little is known about the underlying molecular mechanisms. Here we find that ORAI1-3, are preferentially expressed in PTECs and downregulated in patients with DN. Hyperglycemia or blockade of insulin signaling reduces the expression of ORAI1-3. Inhibition of ORAI channels by BTP2 and diethylstilbestrol or silencing of ORAI expression impairs albumin uptake. Transgenic mice expressing a dominant-negative Orai1 mutant (E108Q) increases albuminuria, and in vivo injection of BTP2 exacerbates albuminuria in streptozotocin-induced and Akita diabetic mice. The albumin endocytosis is Ca2+-dependent and accompanied by ORAI1 internalization. Amnionless (AMN) associates with ORAIs and forms STIM/ORAI/AMN complexes after Ca2+ store depletion. STIM1/ORAI1 colocalizes with clathrin, but not with caveolin, at the apical membrane of PTECs, which determines clathrin-mediated endocytosis. These findings provide insights into the mechanisms of protein reabsorption and potential targets for treating diabetic proteinuria. Patients with diabetic nephropathy suffer from impaired albumin reabsorption by proximal tubular epithelial cells. Here authors use diabetic and transgenic mouse models and in vitro models to show the cause for this lies in the down regulation and internalization of the ion channels, ORAI1-3.
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Affiliation(s)
- Bo Zeng
- Centre for Cardiovascular and Metabolic Research, Hull York Medical School, University of Hull, Hull, HU6 7RX, UK. .,Key Laboratory of Medical Electrophysiology, Ministry of Education, and Institute of Cardiovascular Research, Southwest Medical University, Luzhou, 646000, China.
| | - Gui-Lan Chen
- Centre for Cardiovascular and Metabolic Research, Hull York Medical School, University of Hull, Hull, HU6 7RX, UK.,Key Laboratory of Medical Electrophysiology, Ministry of Education, and Institute of Cardiovascular Research, Southwest Medical University, Luzhou, 646000, China
| | - Eliana Garcia-Vaz
- Department of Clinical Sciences in Malmö, Lund University Diabetes Centre, Lund University, Malmö, 214 28 Malmö, Sweden
| | - Sunil Bhandari
- Department of Renal Medicine and Hull York Medical School, Hull Royal Infirmary, Hull and East Yorkshire Hospitals NHS Trust, Hull, HU3 2JZ, UK
| | - Nikoleta Daskoulidou
- Centre for Cardiovascular and Metabolic Research, Hull York Medical School, University of Hull, Hull, HU6 7RX, UK
| | - Lisa M Berglund
- Department of Clinical Sciences in Malmö, Lund University Diabetes Centre, Lund University, Malmö, 214 28 Malmö, Sweden
| | - Hongni Jiang
- Centre for Cardiovascular and Metabolic Research, Hull York Medical School, University of Hull, Hull, HU6 7RX, UK
| | - Thomas Hallett
- Centre for Cardiovascular and Metabolic Research, Hull York Medical School, University of Hull, Hull, HU6 7RX, UK
| | - Lu-Ping Zhou
- Key Laboratory of Medical Electrophysiology, Ministry of Education, and Institute of Cardiovascular Research, Southwest Medical University, Luzhou, 646000, China
| | - Li Huang
- Key Laboratory of Medical Electrophysiology, Ministry of Education, and Institute of Cardiovascular Research, Southwest Medical University, Luzhou, 646000, China
| | - Zi-Hao Xu
- Key Laboratory of Medical Electrophysiology, Ministry of Education, and Institute of Cardiovascular Research, Southwest Medical University, Luzhou, 646000, China
| | - Viji Nair
- Department of Internal Medicine & Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Robert G Nelson
- Chronic Kidney Disease Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Phoenix, AZ, 85014, USA
| | - Wenjun Ju
- Department of Internal Medicine & Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Matthias Kretzler
- Department of Internal Medicine & Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Stephen L Atkin
- Centre for Cardiovascular and Metabolic Research, Hull York Medical School, University of Hull, Hull, HU6 7RX, UK.,Weill Cornell Medical College Qatar, PO Box, 24144, Doha, Qatar
| | - Maria F Gomez
- Department of Clinical Sciences in Malmö, Lund University Diabetes Centre, Lund University, Malmö, 214 28 Malmö, Sweden
| | - Shang-Zhong Xu
- Centre for Cardiovascular and Metabolic Research, Hull York Medical School, University of Hull, Hull, HU6 7RX, UK.
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39
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Abolishment of proximal tubule albumin endocytosis does not affect plasma albumin during nephrotic syndrome in mice. Kidney Int 2017; 93:335-342. [PMID: 29032953 DOI: 10.1016/j.kint.2017.07.024] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2017] [Revised: 07/11/2017] [Accepted: 07/27/2017] [Indexed: 11/22/2022]
Abstract
The megalin/cubilin receptor complex is required for proximal tubular endocytosis and degradation of filtered albumin. An additional high-capacity retrieval pathway of intact albumin for the recovery of large amounts of filtered albumin has been proposed, possibly involving cooperation between megalin/cubilin and the neonatal Fc receptor. To clarify the potential role of such a pathway, we examined the effects of megalin/cubilin gene inactivation on tubular albumin uptake and plasma albumin levels in nephrotic, podocin knockout mice. Immunofluorescence microscopy of megalin/cubilin/podocin knockout mouse kidneys demonstrated abolishment of proximal tubule albumin uptake, in contrast to the excessive albumin accumulation observed in podocin knockout mice compared to controls. Correspondingly, urinary albumin excretion was increased 1.4 fold in megalin/cubilin/podocin compared to podocin knockout mice (albumin/creatinine: 226 vs. 157 mg/mg). However, no difference in plasma albumin levels was observed between megalin/cubilin/podocin and podocin knockout mice, as both were reduced to approximately 40% of controls. There were no differences in liver albumin synthesis by mRNA levels and protein abundance. Thus, megalin/cubilin knockout efficiently blocks proximal tubular albumin uptake in nephrotic mice but plasma albumin levels did not differ as a result of megalin/cubilin-deficiency, suggesting no significance of the megalin/cubilin-pathway for albumin homeostasis by retrieval of intact albumin.
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Argyropoulos CP, Chen SS, Ng YH, Roumelioti ME, Shaffi K, Singh PP, Tzamaloukas AH. Rediscovering Beta-2 Microglobulin As a Biomarker across the Spectrum of Kidney Diseases. Front Med (Lausanne) 2017; 4:73. [PMID: 28664159 PMCID: PMC5471312 DOI: 10.3389/fmed.2017.00073] [Citation(s) in RCA: 150] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Accepted: 05/26/2017] [Indexed: 12/28/2022] Open
Abstract
There is currently an unmet need for better biomarkers across the spectrum of renal diseases. In this paper, we revisit the role of beta-2 microglobulin (β2M) as a biomarker in patients with chronic kidney disease and end-stage renal disease. Prior to reviewing the numerous clinical studies in the area, we describe the basic biology of β2M, focusing in particular on its role in maintaining the serum albumin levels and reclaiming the albumin in tubular fluid through the actions of the neonatal Fc receptor. Disorders of abnormal β2M function arise as a result of altered binding of β2M to its protein cofactors and the clinical manifestations are exemplified by rare human genetic conditions and mice knockouts. We highlight the utility of β2M as a predictor of renal function and clinical outcomes in recent large database studies against predictions made by recently developed whole body population kinetic models. Furthermore, we discuss recent animal data suggesting that contrary to textbook dogma urinary β2M may be a marker for glomerular rather than tubular pathology. We review the existing literature about β2M as a biomarker in patients receiving renal replacement therapy, with particular emphasis on large outcome trials. We note emerging proteomic data suggesting that β2M is a promising marker of chronic allograft nephropathy. Finally, we present data about the role of β2M as a biomarker in a number of non-renal diseases. The goal of this comprehensive review is to direct attention to the multifaceted role of β2M as a biomarker, and its exciting biology in order to propose the next steps required to bring this recently rediscovered biomarker into the twenty-first century.
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Affiliation(s)
- Christos P Argyropoulos
- Nephrology Division, Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM, United States
| | - Shan Shan Chen
- Nephrology Division, Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM, United States
| | - Yue-Harn Ng
- Nephrology Division, Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM, United States
| | - Maria-Eleni Roumelioti
- Nephrology Division, Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM, United States
| | - Kamran Shaffi
- Nephrology Division, Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM, United States
| | - Pooja P Singh
- Nephrology Division, Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM, United States
| | - Antonios H Tzamaloukas
- Nephrology Division, Department of Internal Medicine, University of New Mexico School of Medicine, Albuquerque, NM, United States.,Raymond G. Murphy VA Medical Center Albuquerque, Albuquerque, NM, United States
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Endocytic receptor LRP2/megalin—of holoprosencephaly and renal Fanconi syndrome. Pflugers Arch 2017; 469:907-916. [DOI: 10.1007/s00424-017-1992-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 05/02/2017] [Accepted: 05/03/2017] [Indexed: 12/31/2022]
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Wen L, Andersen PK, Husum DMU, Nørregaard R, Zhao Z, Liu Z, Birn H. MicroRNA-148b regulates megalin expression and is associated with receptor downregulation in mice with unilateral ureteral obstruction. Am J Physiol Renal Physiol 2017; 313:F210-F217. [PMID: 28331063 DOI: 10.1152/ajprenal.00585.2016] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 03/02/2017] [Accepted: 03/16/2017] [Indexed: 11/22/2022] Open
Abstract
Megalin is a multiligand, endocytic receptor that is important for the normal, proximal tubule reabsorption of filtered proteins, hormones, enzymes, essential nutrients, and nephrotoxins. Megalin dysfunction has been associated with acute, as well as chronic kidney diseases. Tubular proteinuria has been observed following unilateral ureteral obstruction (UUO), suggesting megalin dysfunction; however, the pathophysiological mechanism has not been determined. To identify potential regulators of megalin expression, we examined renal microRNAs (miRNAs) expression and observed an upregulation of microRNA-148b (miR-148b) in obstructed mouse kidneys 7 days after UUO, which was associated with a significant reduction in proximal tubule megalin expression and accumulation of megalin ligands. By in silico miRNA target prediction analysis, we identified megalin messenger RNA (mRNA) as a potential target of miR-148b and confirmed using a dual-luciferase reporter assay that miR-148b targeted the 3'-untranslated region of the megalin gene. Transfection of LLC-PK1 cells with miR-148b mimic reduced endogenous megalin mRNA and protein levels in a concentration-dependent manner, while transfection with miR-148b inhibitor resulted in an increase. Our findings suggest that miR-148b directly downregulates megalin expression and that miR-148b negatively regulates megalin expression in UUO-induced kidney injury. Furthermore, the identification of a miRNA regulating megalin expression may allow for targeted interventions to modulate megalin function and proximal tubule uptake of proteins, as well as other ligands.
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Affiliation(s)
- Lu Wen
- Department of Biomedicine, Aarhus University, Aarhus, Denmark.,Department of Nephrology, First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Pia K Andersen
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Dina M U Husum
- Department of Clinical Medicine, Aarhus University, Aarhus, Denmark; and
| | - Rikke Nørregaard
- Department of Clinical Medicine, Aarhus University, Aarhus, Denmark; and
| | - Zhanzheng Zhao
- Department of Nephrology, First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Zhangsuo Liu
- Department of Nephrology, First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Henrik Birn
- Department of Biomedicine, Aarhus University, Aarhus, Denmark; .,Department of Renal Medicine, Aarhus University Hospital, Aarhus, Denmark
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Sun J, Hultenby K, Axelsson J, Nordström J, He B, Wernerson A, Lindström K. Proximal Tubular Expression Patterns of Megalin and Cubilin in Proteinuric Nephropathies. Kidney Int Rep 2017; 2:721-732. [PMID: 29142988 PMCID: PMC5678615 DOI: 10.1016/j.ekir.2017.02.012] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Revised: 02/09/2017] [Accepted: 02/21/2017] [Indexed: 01/10/2023] Open
Abstract
Introduction Receptor-mediated endocytosis is responsible for protein reabsorption in the proximal tubules. For albumin this process involves at least 2 interacting receptors, megalin and cubilin. Albumin is not usually present in the urine, indicating a highly efficient tubular reuptake under physiological conditions. However, early appearance of albuminuria may mean that the tubular system is overwhelmed by large quantities of albumin or that the function is impaired. Methods To better understand the physiological role of megalin and cubilin in human renal disease, renal biopsies from 15 patients with a range of albuminuria and 3 healthy living donors were analyzed for proximal tubular expression of megalin and cubilin using immunohistochemistry (IHC) and semiquantitative immune-electron microscopy. Their expression in proteinuric zebrafish was also studied. Results Megalin and cubilin were expressed in brush border and cytoplasmic vesicles. Patients with microalbuminuric IgA nephropathy and thin membrane disease had significantly higher megalin in proximal tubules, whereas those with macro- or nephrotic-range albuminuria had unchanged levels. Cubilin expression was significantly higher in all patients. In a proteinuric zebrafish nphs2 knockdown model, we found a dose-dependent increase in the expression of tubular megalin and cubilin in response to tubular protein uptake. Discussion Megalin and cubilin show different expression patterns in different human diseases, which indicates that the 2 tubular proteins differently cooperate in cleaning up plasma proteins in kidney tubules.
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Affiliation(s)
- Jia Sun
- Division of Renal Medicine, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden
| | - Kjell Hultenby
- Division of Clinical Research Center, Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Jonas Axelsson
- Division of Matrix Biology, Department of Medical Biochemistry and Biophysics; Karolinska Institutet, Stockholm, Sweden.,Department Clinical Immunology, Karolinska University Hospital, Stockholm, Sweden
| | - Johan Nordström
- Division of Transplantation, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden.,Department of Transplant Surgery, Karolinska University Hospital, Stockholm, Sweden
| | - Bing He
- Division of Matrix Biology, Department of Medical Biochemistry and Biophysics; Karolinska Institutet, Stockholm, Sweden
| | - Annika Wernerson
- Division of Renal Medicine, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden.,Department of Pathology, Karolinska University Hospital, Stockholm, Sweden
| | - Karin Lindström
- Division of Renal Medicine, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden.,Department of Nephrology, Karolinska University Hospital, Stockholm, Sweden
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Nielsen R, Christensen EI, Birn H. Megalin and cubilin in proximal tubule protein reabsorption: from experimental models to human disease. Kidney Int 2017; 89:58-67. [PMID: 26759048 DOI: 10.1016/j.kint.2015.11.007] [Citation(s) in RCA: 288] [Impact Index Per Article: 41.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Revised: 08/17/2015] [Accepted: 08/19/2015] [Indexed: 01/19/2023]
Abstract
Proximal tubule protein uptake is mediated by 2 receptors, megalin and cubilin. These receptors rescue a variety of filtered ligands, including biomarkers, essential vitamins, and hormones. Receptor gene knockout animal models have identified important functions of the receptors and have established their essential role in modulating urinary protein excretion. Rare genetic syndromes associated with dysfunction of these receptors have been identified and characterized, providing additional information on the importance of these receptors in humans. Using various disease models in combination with receptor gene knockout, the implications of receptor dysfunction in acute and chronic kidney injury have been explored and have pointed to potential new roles of these receptors. Based on data from animal models, this paper will review current knowledge on proximal tubule endocytic receptor function and regulation, and their role in renal development, protein reabsorption, albumin uptake, and normal renal physiology. These findings have implications for the pathophysiology and diagnosis of proteinuric renal diseases. We will examine the limitations of the different models and compare the findings to phenotypic observations in inherited human disorders associated with receptor dysfunction. Furthermore, evidence from receptor knockout mouse models as well as human observations suggesting a role of protein receptors for renal disease will be discussed in light of conditions such as chronic kidney disease, diabetes, and hypertension.
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Affiliation(s)
- Rikke Nielsen
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | | | - Henrik Birn
- Department of Biomedicine, Aarhus University, Aarhus, Denmark; Department of Renal Medicine, Aarhus University Hospital, Aarhus, Denmark.
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Storm T, Christensen EI, Christensen JN, Kjaergaard T, Uldbjerg N, Larsen A, Honoré B, Madsen M. Megalin Is Predominantly Observed in Vesicular Structures in First and Third Trimester Cytotrophoblasts of the Human Placenta. J Histochem Cytochem 2016; 64:769-784. [PMID: 27798286 DOI: 10.1369/0022155416672210] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 08/30/2016] [Indexed: 12/31/2022] Open
Abstract
The membrane receptor megalin is crucial for normal fetal development. Besides its expression in the developing fetus, megalin is also expressed in the human placenta. Similar to its established function in the kidney proximal tubules, placental megalin has been proposed to mediate uptake of vital nutrients. However, details of megalin expression, subcellular localization, and function in the human placenta remain to be established. By immunohistochemical analyses of first trimester and term human placenta, we showed that megalin is predominantly expressed in cytotrophoblasts, the highly proliferative cells in placenta. Only limited amounts of megalin could be detected in syncytiotrophoblasts and least in term placenta syncytiotrophoblasts. Immunocytochemical analyses furthermore showed that placental megalin associates with structures of the endolysosomal apparatus. Combined, our results clearly place placental megalin in the context of endocytosis and trafficking of ligands. However, due to the limited expression of megalin in syncytiotrophoblasts, especially in term placenta, it appears that the main role for placental megalin is not to mediate uptake of nutrients from the maternal bloodstream, as previously proposed. In contrast, our results point toward novel and complex functions for megalin in the cytotrophoblasts. Thus, we propose that the perception of placental megalin localization and function should be revised.
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Affiliation(s)
- Tina Storm
- Department of Biomedicine, Aarhus University, Aarhus C, Denmark (TS, EIC, JNC, TK, AL, BH, MM)
| | - Erik I Christensen
- Department of Biomedicine, Aarhus University, Aarhus C, Denmark (TS, EIC, JNC, TK, AL, BH, MM)
| | - Julie Nelly Christensen
- Department of Biomedicine, Aarhus University, Aarhus C, Denmark (TS, EIC, JNC, TK, AL, BH, MM)
| | - Tine Kjaergaard
- Department of Biomedicine, Aarhus University, Aarhus C, Denmark (TS, EIC, JNC, TK, AL, BH, MM)
| | - Niels Uldbjerg
- Department of Clinical Medicine-Obstetrics and Gynaecology, Aarhus University Hospital, Skejby, Denmark (NU)
| | - Agnete Larsen
- Department of Biomedicine, Aarhus University, Aarhus C, Denmark (TS, EIC, JNC, TK, AL, BH, MM)
| | - Bent Honoré
- Department of Biomedicine, Aarhus University, Aarhus C, Denmark (TS, EIC, JNC, TK, AL, BH, MM)
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Christ A, Herzog K, Willnow TE. LRP2, an auxiliary receptor that controls sonic hedgehog signaling in development and disease. Dev Dyn 2016; 245:569-79. [PMID: 26872844 DOI: 10.1002/dvdy.24394] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2015] [Revised: 02/03/2016] [Accepted: 02/07/2016] [Indexed: 12/31/2022] Open
Abstract
To fulfill their multiple roles in organ development and adult tissue homeostasis, hedgehog (HH) morphogens act through their receptor Patched (PTCH) on target cells. However, HH actions also require HH binding proteins, auxiliary cell surface receptors that agonize or antagonize morphogen signaling in a context-dependent manner. Here, we discuss recent findings on the LDL receptor-related protein 2 (LRP2), an exemplary HH binding protein that modulates sonic hedgehog activities in stem and progenitor cell niches in embryonic and adult tissues. LRP2 functions are crucial for developmental processes in a number of tissues, including the brain, the eye, and the heart, and defects in this receptor pathway are the cause of devastating congenital diseases in humans. Developmental Dynamics 245:569-579, 2016. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Annabel Christ
- Max-Delbrueck-Center for Molecular Medicine, 13125, Berlin, Germany
| | - Katja Herzog
- Max-Delbrueck-Center for Molecular Medicine, 13125, Berlin, Germany
| | - Thomas E Willnow
- Max-Delbrueck-Center for Molecular Medicine, 13125, Berlin, Germany
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47
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Cárdenas-González M, Jacobo Estrada T, Rodríguez-Muñoz R, Barrera-Chimal J, Bobadilla NA, Barbier OC, Del Razo LM. Sub-chronic exposure to fluoride impacts the response to a subsequent nephrotoxic treatment with gentamicin. J Appl Toxicol 2015; 36:309-19. [DOI: 10.1002/jat.3186] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Revised: 05/01/2015] [Accepted: 05/02/2015] [Indexed: 01/03/2023]
Affiliation(s)
- Mariana Cárdenas-González
- Departamento de Toxicología; Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN); México D. F. Mexico
| | - Tania Jacobo Estrada
- Departamento de Toxicología; Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN); México D. F. Mexico
| | - Rafael Rodríguez-Muñoz
- Departamento de Fisiología, Biofísica y Neurociencias; Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN); México D. F. Mexico
| | - Jonatan Barrera-Chimal
- Unidad de Fisiología Molecular. Instituto de Investigaciones Biomédicas; Universidad Nacional Autónoma de México and Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán; México D. F. Mexico
| | - Norma A. Bobadilla
- Unidad de Fisiología Molecular. Instituto de Investigaciones Biomédicas; Universidad Nacional Autónoma de México and Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán; México D. F. Mexico
| | - Olivier C. Barbier
- Departamento de Toxicología; Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN); México D. F. Mexico
| | - Luz M. Del Razo
- Departamento de Toxicología; Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN); México D. F. Mexico
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Wagner MC, Campos-Bilderback SB, Chowdhury M, Flores B, Lai X, Myslinski J, Pandit S, Sandoval RM, Wean SE, Wei Y, Satlin LM, Wiggins RC, Witzmann FA, Molitoris BA. Proximal Tubules Have the Capacity to Regulate Uptake of Albumin. J Am Soc Nephrol 2015; 27:482-94. [PMID: 26054544 DOI: 10.1681/asn.2014111107] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Accepted: 05/04/2015] [Indexed: 12/26/2022] Open
Abstract
Evidence from multiple studies supports the concept that both glomerular filtration and proximal tubule (PT) reclamation affect urinary albumin excretion rate. To better understand these roles of glomerular filtration and PT uptake, we investigated these processes in two distinct animal models. In a rat model of acute exogenous albumin overload, we quantified glomerular sieving coefficients (GSC) and PT uptake of Texas Red-labeled rat serum albumin using two-photon intravital microscopy. No change in GSC was observed, but a significant decrease in PT albumin uptake was quantified. In a second model, loss of endogenous albumin was induced in rats by podocyte-specific transgenic expression of diphtheria toxin receptor. In these albumin-deficient rats, exposure to diphtheria toxin induced an increase in albumin GSC and albumin filtration, resulting in increased exposure of the PTs to endogenous albumin. In this case, PT albumin reabsorption was markedly increased. Analysis of known albumin receptors and assessment of cortical protein expression in the albumin overload model, conducted to identify potential proteins and pathways affected by acute protein overload, revealed changes in the expression levels of calreticulin, disabled homolog 2, NRF2, angiopoietin-2, and proteins involved in ATP synthesis. Taken together, these results suggest that a regulated PT cell albumin uptake system can respond rapidly to different physiologic conditions to minimize alterations in serum albumin level.
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Affiliation(s)
- Mark C Wagner
- Indiana University School of Medicine, The Roudebush Veterans Affair Medical Center, Indiana Center for Biological Microscopy, Indianapolis, Indiana
| | - Silvia B Campos-Bilderback
- Indiana University School of Medicine, The Roudebush Veterans Affair Medical Center, Indiana Center for Biological Microscopy, Indianapolis, Indiana
| | - Mahboob Chowdhury
- Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan
| | - Brittany Flores
- Indiana University School of Medicine, The Roudebush Veterans Affair Medical Center, Indiana Center for Biological Microscopy, Indianapolis, Indiana
| | - Xianyin Lai
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana; and
| | - Jered Myslinski
- Indiana University School of Medicine, The Roudebush Veterans Affair Medical Center, Indiana Center for Biological Microscopy, Indianapolis, Indiana
| | - Sweekar Pandit
- Indiana University School of Medicine, The Roudebush Veterans Affair Medical Center, Indiana Center for Biological Microscopy, Indianapolis, Indiana
| | - Ruben M Sandoval
- Indiana University School of Medicine, The Roudebush Veterans Affair Medical Center, Indiana Center for Biological Microscopy, Indianapolis, Indiana
| | - Sarah E Wean
- Indiana University School of Medicine, The Roudebush Veterans Affair Medical Center, Indiana Center for Biological Microscopy, Indianapolis, Indiana
| | - Yuan Wei
- Department of Pediatrics, The Icahn School of Medicine at Mount Sinai, New York
| | - Lisa M Satlin
- Department of Pediatrics, The Icahn School of Medicine at Mount Sinai, New York
| | - Roger C Wiggins
- Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan
| | - Frank A Witzmann
- Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana
| | - Bruce A Molitoris
- Indiana University School of Medicine, The Roudebush Veterans Affair Medical Center, Indiana Center for Biological Microscopy, Indianapolis, Indiana; Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana
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The role of albumin receptors in regulation of albumin homeostasis: Implications for drug delivery. J Control Release 2015; 211:144-62. [PMID: 26055641 DOI: 10.1016/j.jconrel.2015.06.006] [Citation(s) in RCA: 139] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Revised: 06/02/2015] [Accepted: 06/04/2015] [Indexed: 12/20/2022]
Abstract
Albumin is the most abundant protein in blood and acts as a molecular taxi for a plethora of small insoluble substances such as nutrients, hormones, metals and toxins. In addition, it binds a range of medical drugs. It has an unusually long serum half-life of almost 3weeks, and although the structure and function of albumin has been studied for decades, a biological explanation for the long half-life has been lacking. Now, recent research has unravelled that albumin-binding cellular receptors play key roles in the homeostatic regulation of albumin. Here, we review our current understanding of albumin homeostasis with a particular focus on the impact of the cellular receptors, namely the neonatal Fc receptor (FcRn) and the cubilin-megalin complex, and we discuss their importance on uses of albumin in drug delivery.
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50
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In-depth phenotyping of a Donnai-Barrow patient helps clarify proximal tubule dysfunction. Pediatr Nephrol 2015; 30:1027-31. [PMID: 25822460 DOI: 10.1007/s00467-014-3037-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Revised: 12/11/2014] [Accepted: 12/16/2014] [Indexed: 10/23/2022]
Abstract
BACKGROUND The megalin/cubilin/amnionless complex is essential for albumin and low molecular weight (LMW) protein reabsorption by renal proximal tubules (PT). Mutations of the LRP2 gene encoding megalin cause autosomal recessive Donnai-Barrow/facio-oculo-acoustico-renal syndrome (DB/FOAR), which is characterized by LMW proteinuria. The pathophysiology of DB/FOAR-associated PT dysfunction remains unclear. CLINICAL CASE A 3-year-old girl presented with growth retardation and proteinuria. Clinical examination was unremarkable, except for a still-opened anterior fontanel and myopia. Psychomotor development was delayed. At 6, she developed sensorineural hearing loss. Hypertelorism was noted when she turned 12. Blood analyses, including renal function parameters, were normal. Urine sediment was bland. Proteinuria was significant and included albumin and LMW proteins. Immunoblotting analyses detected cubilin and type 3 carbonic anhydrase (CA3) in the urine. Renal ultrasound was unremarkable. Optical examination of a renal biopsy did not disclose any tubular or glomerular abnormality. Electron microscopy revealed that PT apical endocytic apparatus was significantly less developed. Immunostaining for megalin showed a faint signal in PT cytosol contrasting with the distribution of cubilin at the apical membrane. The diagnostic procedure led to identifying two mutations of the LRP2 gene. CONCLUSIONS The functional loss of megalin in DB/FOAR causes PT dysfunction characterized by increased urinary shedding of CA3 and cubilin.
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