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Žužul S, Kelam N, Racetin A, Kovačević P, Konjevoda S, Filipović N, Pavlović N, Vukojević K. Immunoexpression Patterns of Megalin, Cubilin, Caveolin-1, Gipc1 and Dab2IP in the Embryonic and Postnatal Development of the Kidneys in Yotari ( Dab1-/-) Mice. Biomedicines 2024; 12:1542. [PMID: 39062115 PMCID: PMC11274389 DOI: 10.3390/biomedicines12071542] [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: 06/15/2024] [Revised: 07/04/2024] [Accepted: 07/08/2024] [Indexed: 07/28/2024] Open
Abstract
Our study examines the immunoexpression patterns of Megalin, Cubilin, Caveolin-1, Gipc1 and Dab2IP in the embryonic development (E) and postnatal (P) mouse kidney, with a focus on differentiating patterns between wild-type (wt) and yotari, Dab1-/- (yot) mice. Immunofluorescence revealed raised immunoexpression of receptors Megalin and Cubilin at the ampulla/collecting ducts and convoluted tubules across all developmental stages, with the most prominent immunoexpression observed in the convoluted tubules and the parietal epithelium of the Bowman's capsule. Quantitative analysis showed a higher percentage of Megalin and Cubilin in wt compared to yot mice at E13.5. Co-expression of Megalin and Cubilin was observed at the apical membrane of convoluted tubules and the parietal layer of the Bowman's capsule. The staining intensity of Megalin varied across developmental stages, with the strongest reactivity observed at the ampulla and collecting ducts at embryonic day (E) 13.5 in wt mice. In contrast, Caveolin-1 exhibited high immunoexpression in the metanephric mesenchyme, blood vessels, and the border area between the metanephric mesenchyme and renal vesicle, with a decrease in immunoexpression as development progressed. Gipc1 showed diffuse cytoplasmic staining in metanephric mesenchyme, convoluted tubules and collecting ducts, with significant differences in immunoexpression between wild-type and yot mice at both investigated embryonic time points. Dab2IP immunofluorescent staining was most prominent in renal vesicle/glomeruli and ampulla/collecting ducts at E13.5, with mild staining intensity observed in the distal convoluted tubules postnatally. Our findings elucidate distinct immunoexpression of patterns and potential parts of these proteins in the development and function of the kidney, highlighting the importance of further investigation into their regulatory mechanisms.
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Affiliation(s)
- Sani Žužul
- Clinic for Surgery, Clinical Hospital Firule, 21 000 Split, Croatia;
| | - Nela Kelam
- Department of Anatomy, Histology and Embryology, School of Medicine, University of Split, 21 000 Split, Croatia; (N.K.); (A.R.); (N.F.); (N.P.)
- Center for Translational Research in Biomedicine, School of Medicine, University of Split, 21 000 Split, Croatia
| | - Anita Racetin
- Department of Anatomy, Histology and Embryology, School of Medicine, University of Split, 21 000 Split, Croatia; (N.K.); (A.R.); (N.F.); (N.P.)
- Center for Translational Research in Biomedicine, School of Medicine, University of Split, 21 000 Split, Croatia
| | - Petra Kovačević
- Department of Ophthalmology, University Hospital Center of Zagreb, 10 000 Zagreb, Croatia;
| | - Suzana Konjevoda
- Department of Health Studies, University of Zadar, 23 000 Zadar, Croatia;
- Department of Ophthalmology, General Hospital Zadar, 23 000 Zadar, Croatia
| | - Natalija Filipović
- Department of Anatomy, Histology and Embryology, School of Medicine, University of Split, 21 000 Split, Croatia; (N.K.); (A.R.); (N.F.); (N.P.)
| | - Nikola Pavlović
- Department of Anatomy, Histology and Embryology, School of Medicine, University of Split, 21 000 Split, Croatia; (N.K.); (A.R.); (N.F.); (N.P.)
| | - Katarina Vukojević
- Department of Anatomy, Histology and Embryology, School of Medicine, University of Split, 21 000 Split, Croatia; (N.K.); (A.R.); (N.F.); (N.P.)
- Center for Translational Research in Biomedicine, School of Medicine, University of Split, 21 000 Split, Croatia
- Department of Anatomy, School of Medicine, University of Mostar, 88 000 Mostar, Bosnia and Herzegovina
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Yang J, Liu X. Controversy between biopsy and risk in children with proteinuria: is there a paradigm war? BMC Nephrol 2024; 25:221. [PMID: 38992620 PMCID: PMC11238415 DOI: 10.1186/s12882-024-03660-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2024] [Accepted: 07/01/2024] [Indexed: 07/13/2024] Open
Abstract
BACKGROUND Proteinuria is a prevalent symptom of pediatric nephrology, while kidney biopsy remains the gold standard for kidney tissue analysis, and it is currently controversial. We report the rare case that the mutation in the AMN gene was considered to cause chronically isolated proteinuria and also suggest that renal biopsy should be chosen with caution in children with chronic isolated non-nephrotic levels of proteinuria and that genetic testing may be feasible for the early precise diagnosis. CASE PRESENTATION A 35-month-old boy presented with excessive urine foaming for more than half a month; his proteinuria was considered non-nephrotic range and urine protein electrophoresis was suggestive of mixed proteinuria; other than that, the investigations are non-specific. Given the child's chronic isolated proteinuria and good renal function, we chose to refine the genetic test rather than a renal biopsy; a compound heterozygous variant was found in the AMN gene of this child which was caused by a point mutation in the father, and a partial chromosomal deletion in the mother. CONCLUSIONS Cubilin(encoded by CUBN), amnionless(encoded by AMN), and megalin form a multiligand receptor complex; CUBN or AMN gene variants have been implicated as a hereditary cause of megaloblastic anemia, proteinuria, and neurological impairment. In the past few decades, chronic isolated proteinuria caused by CUBN gene variants is benign, non-progressive, and has normal renal function. However, the child is the first reported case of isolated proteinuria of AMN gene mutation, indicating that the earlier diagnostic genetic sequencing in an otherwise well, not nephrotic proteinuria child may be a convenient, cost-effective, and harmless option, challenging the traditional paradigm.
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Affiliation(s)
- Jingyi Yang
- Department of Nephrology, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health, No. 56 Nanlishi Street, Xi Cheng District, Beijing, 100045, China
| | - Xiaorong Liu
- Department of Nephrology, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health, No. 56 Nanlishi Street, Xi Cheng District, Beijing, 100045, China.
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Yang H, He L, Gong H, Wan C, Ding J, Liao P, Wang X. Identification of novel pathogenic variants of CUBN in patients with isolated proteinuria. Mol Genet Genomic Med 2024; 12:e2353. [PMID: 38488435 PMCID: PMC10941600 DOI: 10.1002/mgg3.2353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2023] [Revised: 11/29/2023] [Accepted: 12/11/2023] [Indexed: 03/18/2024] Open
Abstract
BACKGROUND Although proteinuria is long recognized as an independent risk factor for progressive chronic kidney diseases, not all forms of proteinuria are detrimental to kidney function, one of which is isolated proteinuria caused by cubilin (CUBN)-specific mutations. CUBN encodes an endocytic receptor, initially found to be responsible for the Imerslund-Gräsbeck syndrome (IGS; OMIM #261100) characterized by a combined phenotype of megaloblastic anemia and proteinuria. METHODS After analyzing their clinical and pathological characterizations, next-generation sequencing for renal disease genes or whole-exome sequencing (WES) was performed on four patients with non-progressive isolated proteinuria. CUBN biallelic pathogenic variants were identified and further analyzed by cDNA-PCR sequencing, immunohistochemistry, minigene assay, and multiple in silico prediction tools, including 3D protein modeling. RESULTS Here, we present four patients with isolated proteinuria caused by CUBN C-terminal biallelic pathogenic variants, all of which showed no typical IGS symptoms, such as anemia and vitamin B12 deficiency. Their urine protein levels fluctuated between +~++ and estimated glomerular filtration rate (eGFR) were normal or slightly higher. Mild mesangial hypercellularity was found in three children's renal biopsies. A homozygous splice-site variant of CUBN (c.6821+3 (IVS44) A>G) was proven to result in the exon 44 skipping and premature translation termination by cDNA sequencing and immunohistochemistry. Compound heterozygous mutations were identified among the other three children, including another novel splice-site variant (c.10764+1 (IVS66) G>A) causing the retention of first 4 nucleotides in intron 66 by minigene assay, two unreported missense mutations (c.4907G>A (p.R1636Q); c. 9095 A>G (p.Y3032C)), and two reported missense mutations in China (c.8938G>A (p.D2980N); c. 9287T>C (p.L3096P)), locating behind the vitamin B12-binding domain, affecting CUB11, CUB16, CUB22, CUB23, and CUB27 domains, respectively. CONCLUSION These results demonstrate that above CUBN mutations may cause non-progressive and isolated proteinuria, expanding the variant spectrum of CUBN and benefiting our understanding of proteinuria and renal function.
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Affiliation(s)
- Huihui Yang
- Department of Nephrology, Wuhan Children's Hospital (Wuhan Maternal and Child Healthcare Center)Tongji Medical College, Huazhong University of Science & TechnologyWuhanChina
| | - Lanfen He
- Department of Nephrology, Wuhan Children's Hospital (Wuhan Maternal and Child Healthcare Center)Tongji Medical College, Huazhong University of Science & TechnologyWuhanChina
| | - Hongjian Gong
- Clinical Research Center, Wuhan Children's Hospital (Wuhan Maternal and Child Healthcare Center)Tongji Medical College, Huazhong University of Science & TechnologyWuhanChina
| | - Chunhui Wan
- Precision Medical Center, Wuhan Children's Hospital (Wuhan Maternal and Child Healthcare Center)Tongji Medical College, Huazhong University of Science & TechnologyWuhanChina
| | - Juanjuan Ding
- Department of Nephrology, Wuhan Children's Hospital (Wuhan Maternal and Child Healthcare Center)Tongji Medical College, Huazhong University of Science & TechnologyWuhanChina
| | - Panli Liao
- Department of Nephrology, Wuhan Children's Hospital (Wuhan Maternal and Child Healthcare Center)Tongji Medical College, Huazhong University of Science & TechnologyWuhanChina
| | - Xiaowen Wang
- Department of Nephrology, Wuhan Children's Hospital (Wuhan Maternal and Child Healthcare Center)Tongji Medical College, Huazhong University of Science & TechnologyWuhanChina
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Clinical and genetic characterization of children with cubilin variants. Pediatr Nephrol 2023; 38:1381-1385. [PMID: 36112210 DOI: 10.1007/s00467-022-05730-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Revised: 08/28/2022] [Accepted: 08/29/2022] [Indexed: 10/14/2022]
Abstract
BACKGROUND Cubilin is one of the receptor proteins responsible for reabsorption of albumin in proximal tubules and is encoded by the CUBN gene. We aimed to evaluate clinical and genetic characterization of six patients with proteinuria who had CUBN mutations. METHODS Patients' characteristics, serum creatinine, albumin, vitamin B12 levels, urine analysis, spot urine protein/creatinine, microalbumin/creatinine, beta-2 microglobulin/creatinine ratios, estimated glomerular filtration rates (eGFR), treatments, kidney biopsies, and genetic analyses were evaluated. RESULTS Six patients (2 female, 4 male) with an incidental finding of proteinuria were evaluated. Mean admission age and follow-up time were 7.3 ± 2.9 and 6.5 ± 5.6 years, respectively. Serum albumin, creatinine, and eGFR were normal; urine analysis revealed no hematuria, and C3, C4, ANA, and anti-DNA were negative; kidney ultrasonography was normal for all patients. Urine protein/creatinine was 0.9 ± 0.3 mg/mg, and microalbumin was high in all patients. Serum vitamin B12 was low in two patients and normal in four. Kidney biopsy was performed in four patients, three demonstrated normal light microscopy, and there was one focal segmental glomerulosclerosis (FSGS). Genetic tests revealed four homozygous and two compound heterozygous mutations in the C-terminal part of cubilin. All patients had normal eGFR and still had non-nephrotic range proteinuria at last visit. CONCLUSIONS CUBN gene mutations should be considered in patients with isolated non-nephrotic range proteinuria and normal kidney function. Diagnosing these patients, who are thought to have a better prognosis, is important in terms of avoiding unnecessary treatment and predicting prognosis. CUBN gene mutations may also present as FSGS which extends the spectrum of renal manifestation of these patients. A higher resolution version of the Graphical abstract is available as Supplementary information.
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Pathological characteristics of light chain crystalline podocytopathy. Kidney Int 2023; 103:616-626. [PMID: 36581019 DOI: 10.1016/j.kint.2022.11.026] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 11/14/2022] [Accepted: 11/17/2022] [Indexed: 12/28/2022]
Abstract
Monoclonal immunoglobulin light chain (LC) crystalline inclusions within podocytes are rare, poorly characterized entities. To provide more insight, we now present the first clinicopathologic series of LC crystalline podocytopathy (LCCP) encompassing 25 patients (68% male, median age 56 years). Most (80%) patients presented with proteinuria and chronic kidney disease, with nephrotic syndrome in 28%. Crystalline keratopathy and Fanconi syndrome were present in 22% and 10%, respectively. The hematologic condition was monoclonal gammopathy of renal significance (MGRS) in 55% and multiple myeloma in 45%. The serum monoclonal immunoglobulin was IgG κappa in 86%. Histologically, 60% exhibited focal segmental glomerulosclerosis (FSGS), often collapsing. Ultrastructurally, podocyte LC crystals were numerous with variable effacement of foot processes. Crystals were also present in proximal tubular cells as light chain proximal tubulopathy (LCPT) in 80% and in interstitial histiocytes in 36%. Significantly, frozen-section immunofluorescence failed to reveal the LC composition of crystals in 88%, requiring paraffin-immunofluorescence or immunohistochemistry, with identification of kappa LC in 87%. The LC variable region gene segment, determined by mass spectrometry of glomeruli or bone marrow plasma cell sequencing, was IGKV1-33 in four and IGKV3-20 in one. Among 21 patients who received anti-plasma cell-directed chemotherapy, 50% achieved a kidney response, which depended on a deep hematologic response. After a median follow-up of 36 months, 26% progressed to kidney failure and 17% died. The mean kidney failure-free survival was 57.6 months and was worse in those with FSGS. In sum, LCCP is rare, mostly associates with IgG κappa MGRS, and frequently has concurrent LCPT, although Fanconi syndrome is uncommon. Paraffin-immunofluorescence and electron microscopy are essential to prevent misdiagnosis as primary FSGS since kidney survival depends on early diagnosis and subsequent clone-directed therapy.
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Madureira Gomes S, Igreja AI, Silva R, Oliveira JP, Pinto H. Podocytopathy and Glomerular Basement Membrane Anomalies in Two Patients With Cubilin Gene Mutations. Cureus 2023; 15:e34730. [PMID: 36913226 PMCID: PMC9998106 DOI: 10.7759/cureus.34730] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/07/2023] [Indexed: 02/10/2023] Open
Abstract
Proteinuria is a frequent finding in pediatric patients and in most cases, it is intermittent or transient. When proteinuria is moderate/severe and persistent, it may require an extensive complementary study, histopathological examination and genetic test, in order to clarify its etiology. Cubilin (CUBN) is a large glycosylated extracellular protein, initially detected in proximal tubular cells, and later in podocytes. Isolated persistent proteinuria caused by cubilin gene mutations is rare, only a few cases have been reported in the literature and even fewer patients underwent renal biopsy and electron microscopy that could help to elucidate the pathogenesis of the disease. The authors describe two pediatric clinical cases referred to pediatric nephrology consultation due to persistent proteinuria. Neither of them had any other complaints, and renal function and immunological and serological studies were normal. Renal histopathology showed podocytes changes and glomerular basal membrane alterations suggestive of Alport Syndrome. The genetic study identified two heterozygous variants in the cubilin gene in both, also later identified in their parents. They were started on ramipril, with improvement in proteinuria, and both patients remain asymptomatic and without changes in renal function. At present, due to the uncertainty of prognosis, it is suggested to keep CUBN gene mutation patients under close surveillance of proteinuria and renal function. The variable ultrastructural patterns of podocytopathy and glomerular basal membrane alterations in kidney biopsies of pediatric patients with proteinuria should lead to the diagnostic possibility of CUBN gene mutation in the differential diagnosis.
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Affiliation(s)
| | - Ana Isabel Igreja
- Department of Pediatrics, Centro Hospitalar De Trás-Os-Montes E Alto Douro, Vila Real, PRT
| | - Roberto Silva
- Department of Pathology, Centro Hospitalar Universitário São João, Porto, PRT.,Faculty of Medicine, University of Porto, Porto, PRT
| | - João Paulo Oliveira
- Department of Genetics, Centro Hospitalar Universitário São João, Porto, PRT.,Institute for Research and Innovation in Health, University of Porto, Porto, PRT
| | - Helena Pinto
- Pediatric Nephrology Unit, Centro Hospitalar Universitário São João, Porto, PRT.,Faculty of Medicine, University of Porto, Porto, PRT
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Priante G, Ceol M, Gianesello L, Bizzotto D, Braghetta P, Calò LA, Del Prete D, Anglani F. Emerging Perspectives on the Rare Tubulopathy Dent Disease: Is Glomerular Damage a Direct Consequence of ClC-5 Dysfunction? Int J Mol Sci 2023; 24:1313. [PMID: 36674829 PMCID: PMC9864126 DOI: 10.3390/ijms24021313] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Revised: 12/22/2022] [Accepted: 12/24/2022] [Indexed: 01/12/2023] Open
Abstract
Dent disease (DD1) is a rare tubulopathy caused by mutations in the CLCN5 gene. Glomerulosclerosis was recently reported in DD1 patients and ClC-5 protein was shown to be expressed in human podocytes. Nephrin and actin cytoskeleton play a key role for podocyte functions and podocyte endocytosis seems to be crucial for slit diaphragm regulation. The aim of this study was to analyze whether ClC-5 loss in podocytes might be a direct consequence of the glomerular damage in DD1 patients. Three DD1 kidney biopsies presenting focal global glomerulosclerosis and four control biopsies were analyzed by immunofluorescence (IF) for nephrin and podocalyxin, and by immunohistochemistry (IHC) for ClC-5. ClC-5 resulted as down-regulated in DD1 vs. control (CTRL) biopsies in both tubular and glomerular compartments (p < 0.01). A significant down-regulation of nephrin (p < 0.01) in DD1 vs. CTRL was demonstrated. CRISPR/Cas9 (Clustered Regularly Interspaced Short Palindromic Repeats/Caspase9) gene editing of CLCN5 in conditionally immortalized human podocytes was used to obtain clones with the stop codon mutation p.(R34Efs*14). We showed that ClC-5 and nephrin expression, analyzed by quantitative Reverse Transcription/Polymerase Chain Reaction (qRT/PCR) and In-Cell Western (ICW), was significantly downregulated in mutant clones compared to the wild type ones. In addition, F-actin staining with fluorescent phalloidin revealed actin derangements. Our results indicate that ClC-5 loss might alter podocyte function either through cytoskeleton disorganization or through impairment of nephrin recycling.
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Affiliation(s)
- Giovanna Priante
- Kidney Histomorphology and Molecular Biology Laboratory, Nephrology Unit, Department of Medicine—DIMED, University of Padua, Via Giustiniani n° 2, 35128 Padua, Italy
| | - Monica Ceol
- Kidney Histomorphology and Molecular Biology Laboratory, Nephrology Unit, Department of Medicine—DIMED, University of Padua, Via Giustiniani n° 2, 35128 Padua, Italy
| | - Lisa Gianesello
- Kidney Histomorphology and Molecular Biology Laboratory, Nephrology Unit, Department of Medicine—DIMED, University of Padua, Via Giustiniani n° 2, 35128 Padua, Italy
| | - Dario Bizzotto
- Department of Molecular Medicine, University of Padua, 35121 Padua, Italy
| | - Paola Braghetta
- Department of Molecular Medicine, University of Padua, 35121 Padua, Italy
| | - Lorenzo Arcangelo Calò
- Kidney Histomorphology and Molecular Biology Laboratory, Nephrology Unit, Department of Medicine—DIMED, University of Padua, Via Giustiniani n° 2, 35128 Padua, Italy
| | - Dorella Del Prete
- Kidney Histomorphology and Molecular Biology Laboratory, Nephrology Unit, Department of Medicine—DIMED, University of Padua, Via Giustiniani n° 2, 35128 Padua, Italy
| | - Franca Anglani
- Kidney Histomorphology and Molecular Biology Laboratory, Nephrology Unit, Department of Medicine—DIMED, University of Padua, Via Giustiniani n° 2, 35128 Padua, Italy
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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: 52] [Impact Index Per Article: 26.0] [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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Koehler S, Huber TB, Denholm B. A protective role for <i>Drosophila</i> Filamin in nephrocytes via Yorkie mediated hypertrophy. Life Sci Alliance 2022; 5:e202101281. [PMID: 35922155 PMCID: PMC9351128 DOI: 10.26508/lsa.202101281] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 07/15/2022] [Accepted: 07/18/2022] [Indexed: 11/24/2022] Open
Abstract
Podocytes are specialized epithelial cells of the kidney glomerulus and are an essential part of the filtration barrier. Because of their position, they are exposed to constant biomechanical forces such as shear stress and hydrostatic pressure. These forces increase during disease, resulting in podocyte injury. It is likely podocytes have adaptative responses to help buffer against deleterious mechanical force and thus reduce injury. However, these responses remain largely unknown. Here, using the <i>Drosophila</i> model, we show the mechanosensor Cheerio (dFilamin) provides a key protective role in nephrocytes. We found expression of an activated mechanosensitive variant of Cheerio rescued filtration function and induced compensatory and hypertrophic growth in nephrocytes depleted of the nephrocyte diaphragm proteins Sns or Duf. Delineating the protective pathway downstream of Cheerio we found repression of the Hippo pathway induces nephrocyte hypertrophy, whereas Hippo activation reversed the Cheerio-mediated hypertrophy. Furthermore, we find Yorkie was activated upon expression of active Cheerio. Taken together, our data suggest that Cheerio acts via the Hippo pathway to induce hypertrophic growth, as a protective response in abnormal nephrocytes.
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Affiliation(s)
- Sybille Koehler
- Biomedical Sciences, University of Edinburgh, Edinburgh, UK
- III Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Tobias B Huber
- III Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Barry Denholm
- Biomedical Sciences, University of Edinburgh, Edinburgh, UK
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Raghubar AM, Pham DT, Tan X, Grice LF, Crawford J, Lam PY, Andersen SB, Yoon S, Teoh SM, Matigian NA, Stewart A, Francis L, Ng MSY, Healy HG, Combes AN, Kassianos AJ, Nguyen Q, Mallett AJ. Spatially Resolved Transcriptomes of Mammalian Kidneys Illustrate the Molecular Complexity and Interactions of Functional Nephron Segments. Front Med (Lausanne) 2022; 9:873923. [PMID: 35872784 PMCID: PMC9300864 DOI: 10.3389/fmed.2022.873923] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Accepted: 05/23/2022] [Indexed: 11/30/2022] Open
Abstract
Available transcriptomes of the mammalian kidney provide limited information on the spatial interplay between different functional nephron structures due to the required dissociation of tissue with traditional transcriptome-based methodologies. A deeper understanding of the complexity of functional nephron structures requires a non-dissociative transcriptomics approach, such as spatial transcriptomics sequencing (ST-seq). We hypothesize that the application of ST-seq in normal mammalian kidneys will give transcriptomic insights within and across species of physiology at the functional structure level and cellular communication at the cell level. Here, we applied ST-seq in six mice and four human kidneys that were histologically absent of any overt pathology. We defined the location of specific nephron structures in the captured ST-seq datasets using three lines of evidence: pathologist's annotation, marker gene expression, and integration with public single-cell and/or single-nucleus RNA-sequencing datasets. We compared the mouse and human cortical kidney regions. In the human ST-seq datasets, we further investigated the cellular communication within glomeruli and regions of proximal tubules-peritubular capillaries by screening for co-expression of ligand-receptor gene pairs. Gene expression signatures of distinct nephron structures and microvascular regions were spatially resolved within the mouse and human ST-seq datasets. We identified 7,370 differentially expressed genes (p adj < 0.05) distinguishing species, suggesting changes in energy production and metabolism in mouse cortical regions relative to human kidneys. Hundreds of potential ligand-receptor interactions were identified within glomeruli and regions of proximal tubules-peritubular capillaries, including known and novel interactions relevant to kidney physiology. Our application of ST-seq to normal human and murine kidneys confirms current knowledge and localization of transcripts within the kidney. Furthermore, the generated ST-seq datasets provide a valuable resource for the kidney community that can be used to inform future research into this complex organ.
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Affiliation(s)
- Arti M. Raghubar
- Kidney Health Service, Royal Brisbane and Women's Hospital, Herston, QLD, Australia
- Conjoint Internal Medicine Laboratory, Chemical Pathology, Pathology Queensland, Health Support Queensland, Herston, QLD, Australia
- Faculty of Medicine, University of Queensland, Brisbane, QLD, Australia
- Anatomical Pathology, Pathology Queensland, Health Support Queensland, Herston, QLD, Australia
- Institute for Molecular Bioscience, University of Queensland, Brisbane, QLD, Australia
| | - Duy T. Pham
- Institute for Molecular Bioscience, University of Queensland, Brisbane, QLD, Australia
| | - Xiao Tan
- Institute for Molecular Bioscience, University of Queensland, Brisbane, QLD, Australia
| | - Laura F. Grice
- Institute for Molecular Bioscience, University of Queensland, Brisbane, QLD, Australia
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD, Australia
| | - Joanna Crawford
- Institute for Molecular Bioscience, University of Queensland, Brisbane, QLD, Australia
| | - Pui Yeng Lam
- Institute for Molecular Bioscience, University of Queensland, Brisbane, QLD, Australia
| | - Stacey B. Andersen
- Genome Innovation Hub, University of Queensland, Brisbane, QLD, Australia
- UQ Sequencing Facility, Institute for Molecular Bioscience, University of Queensland, Brisbane, QLD, Australia
| | - Sohye Yoon
- Genome Innovation Hub, University of Queensland, Brisbane, QLD, Australia
| | - Siok Min Teoh
- UQ Diamantina Institute, Faculty of Medicine, The University of Queensland, Woolloongabba, QLD, Australia
| | - Nicholas A. Matigian
- QCIF Facility for Advanced Bioinformatics, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
| | - Anne Stewart
- Anatomical Pathology, Pathology Queensland, Health Support Queensland, Herston, QLD, Australia
| | - Leo Francis
- Anatomical Pathology, Pathology Queensland, Health Support Queensland, Herston, QLD, Australia
| | - Monica S. Y. Ng
- Kidney Health Service, Royal Brisbane and Women's Hospital, Herston, QLD, Australia
- Conjoint Internal Medicine Laboratory, Chemical Pathology, Pathology Queensland, Health Support Queensland, Herston, QLD, Australia
- Faculty of Medicine, University of Queensland, Brisbane, QLD, Australia
- Institute for Molecular Bioscience, University of Queensland, Brisbane, QLD, Australia
- Nephrology Department, Princess Alexandra Hospital, Woolloongabba, QLD, Australia
| | - Helen G. Healy
- Kidney Health Service, Royal Brisbane and Women's Hospital, Herston, QLD, Australia
- Conjoint Internal Medicine Laboratory, Chemical Pathology, Pathology Queensland, Health Support Queensland, Herston, QLD, Australia
- Faculty of Medicine, University of Queensland, Brisbane, QLD, Australia
| | - Alexander N. Combes
- Department of Anatomy and Developmental Biology, Stem Cells and Development Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia
| | - Andrew J. Kassianos
- Kidney Health Service, Royal Brisbane and Women's Hospital, Herston, QLD, Australia
- Conjoint Internal Medicine Laboratory, Chemical Pathology, Pathology Queensland, Health Support Queensland, Herston, QLD, Australia
- Faculty of Medicine, University of Queensland, Brisbane, QLD, Australia
| | - Quan Nguyen
- Institute for Molecular Bioscience, University of Queensland, Brisbane, QLD, Australia
| | - Andrew J. Mallett
- Faculty of Medicine, University of Queensland, Brisbane, QLD, Australia
- Institute for Molecular Bioscience, University of Queensland, Brisbane, QLD, Australia
- College of Medicine & Dentistry, James Cook University, Townsville, Queensland, QLD, Australia
- Department of Renal Medicine, Townsville University Hospital, Townsville, Queensland, QLD, Australia
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11
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Yang J, Xu Y, Deng L, Zhou L, Qiu L, Zhang Y, Zhou J. CUBN gene mutations may cause focal segmental glomerulosclerosis (FSGS) in children. BMC Nephrol 2022; 23:15. [PMID: 34979989 PMCID: PMC8725476 DOI: 10.1186/s12882-021-02654-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 12/20/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Imerslund-Gräsbeck Syndrome (IGS) is mainly caused by CUBN gene biallelic mutations. Proteinuria accompanies IGS specific symptoms in about half of the patients, isolated proteinuria is rarely reported. Here we present 3 patients with isolated proteinuria and focal segmental glomerulosclerosis (FSGS) caused by CUBN gene biallelic pathogenic variants. METHOD Whole exome sequencing was performed on three children with isolated proteinuria. CUBN gene biallelic pathogenic variants were found and then verified by sanger sequencing. Their clinical, pathological and molecular genetic characteristics were analyzed and correlated accordingly. RESULTS All three children presented with isolated proteinuria, no megaloblastic anemia. Their urine levels of β2 microglobulin were normal or slightly higher. Renal biopsies showed focal segmental glomerulosclerosis with mild glomerular mesangial hypercellularity, partial effacement of foot processes and podocyte microvillation. Two of them were found to carry compound heterozygous mutations and one homozygous mutation of CUBN gene. Totally four CUBN gene biallelic pathogenic variants were identified, including c.9287 T > C (p.L3096P), c.122 + 1G > A, c.7906C > T (p.R2636*), c.10233G > A (p.W3411*). Except for intron splice-site mutation, all other variants are located in highly conserved sites of CUB domain for binding to albumin. CONCLUSION The results demonstrate that CUBN gene mutations may cause isolated proteinuria pathologically presented as FSGS. Our cases extend the spectrum of renal manifestation and genotype of CUBN gene mutations.
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Affiliation(s)
- Jing Yang
- Department of Pediatrics, Tongji Hospital, Tongji Medical college, Huazhong University of Science and Technology, Jiefang Ave. No. 1095, Wuhan, 430030, China
| | - Yongli Xu
- Department of Pediatrics, Tongji Hospital, Tongji Medical college, Huazhong University of Science and Technology, Jiefang Ave. No. 1095, Wuhan, 430030, China
| | - Linxia Deng
- Department of Pediatrics, Tongji Hospital, Tongji Medical college, Huazhong University of Science and Technology, Jiefang Ave. No. 1095, Wuhan, 430030, China
| | - Luowen Zhou
- Department of Neurosurgery, Tongji Hospital, Tongji Medical college, Huazhong University of Science and Technology, Wuhan, China
| | - Liru Qiu
- Department of Pediatrics, Tongji Hospital, Tongji Medical college, Huazhong University of Science and Technology, Jiefang Ave. No. 1095, Wuhan, 430030, China
| | - Yu Zhang
- Department of Pediatrics, Tongji Hospital, Tongji Medical college, Huazhong University of Science and Technology, Jiefang Ave. No. 1095, Wuhan, 430030, China
| | - Jianhua Zhou
- Department of Pediatrics, Tongji Hospital, Tongji Medical college, Huazhong University of Science and Technology, Jiefang Ave. No. 1095, Wuhan, 430030, China.
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12
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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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13
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Atienza-Manuel A, Castillo-Mancho V, De Renzis S, Culi J, Ruiz-Gómez M. Endocytosis mediated by an atypical CUBAM complex modulates slit diaphragm dynamics in nephrocytes. Development 2021; 148:272711. [PMID: 34738617 PMCID: PMC8710305 DOI: 10.1242/dev.199894] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 10/22/2021] [Indexed: 01/14/2023]
Abstract
The vertebrate endocytic receptor CUBAM, consisting of three cubilin monomers complexed with a single amnionless molecule, plays a major role in protein reabsorption in the renal proximal tubule. Here, we show that Drosophila CUBAM is a tripartite complex composed of Amnionless and two cubilin paralogues, Cubilin and Cubilin2, and that it is required for nephrocyte slit diaphragm (SD) dynamics. Loss of CUBAM-mediated endocytosis induces dramatic morphological changes in nephrocytes and promotes enlarged ingressions of the external membrane and SD mislocalisation. These phenotypes result in part from an imbalance between endocytosis, which is strongly impaired in CUBAM mutants, and exocytosis in these highly active cells. Of note, rescuing receptor-mediated endocytosis by Megalin/LRP2 or Rab5 expression only partially restores SD positioning in CUBAM mutants, suggesting a specific requirement of CUBAM in SD degradation and/or recycling. This finding and the reported expression of CUBAM in podocytes suggest a possible unexpected conserved role for this endocytic receptor in vertebrate SD remodelling. Summary: A genetic study revealing that endocytosis mediated by an atypical CUBAM endocytic receptor, composed of Amnionless and two Cubilin paralogues, regulates slit diaphragm remodelling in Drosophila nephrocytes.
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Affiliation(s)
- Alexandra Atienza-Manuel
- Centro de Biología Molecular Severo Ochoa, CSIC and UAM, Nicolás Cabrera 1, Cantoblanco 28049, Madrid, Spain
| | - Vicente Castillo-Mancho
- Centro de Biología Molecular Severo Ochoa, CSIC and UAM, Nicolás Cabrera 1, Cantoblanco 28049, Madrid, Spain
| | - Stefano De Renzis
- European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Joaquim Culi
- Centro de Biología Molecular Severo Ochoa, CSIC and UAM, Nicolás Cabrera 1, Cantoblanco 28049, Madrid, Spain
| | - Mar Ruiz-Gómez
- Centro de Biología Molecular Severo Ochoa, CSIC and UAM, Nicolás Cabrera 1, Cantoblanco 28049, Madrid, Spain
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14
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Molecular determinants of protein reabsorption in the amphibian kidneys. Acta Histochem 2021; 123:151760. [PMID: 34303296 DOI: 10.1016/j.acthis.2021.151760] [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: 04/07/2021] [Revised: 06/28/2021] [Accepted: 07/11/2021] [Indexed: 11/23/2022]
Abstract
Participation of molecular determinants of endocytosis in the processes of glomerular filtration and tubular reabsorption of albumin and lysozyme in the mesonephros of grass frogs (Rana temporaria L.), lake frogs (Rana ridibunda P.), and newts (Triturus vulgaris L.) is investigated. In all studied species, the constitutive expression of endocytic receptors in proximal tubule (PT) cells is established using immunofluorescence microscopy and immunoblotting. The certain stages of lysozyme and albumin endocytosis involving megalin/LRP2, cubilin, clathrin and protein Rab11 are detailed, and the central role of ligand-induced megalin/LRP2 activity in this process is shown. Increased ligand-induced expression for clathrin and Rab11was also found. In grass frogs, the different patterns of endocytic receptors and both absorbed proteins in the initial parts of proximal tubules suggest the proximo-distal specialization of absorptive processes along these tubule segments, similar to this in more complex mammalian nephrons. This data, as well as the revealed peculiarities of ligand-receptor interactions during intracellular trafficking of proteins prove that megalin is mainly involved in the absorption of lysozyme. At the same time, albumin absorption is mediated by both receptors, or cubilin contributes the most. The detection of endocytic receptor in glomerular structural elements in frogs and newts suggests the participation of filtration barrier components in endocytosis of filterable proteins. The results represent a new contribution to the study of the fundamental mechanisms of renal protein uptake in the amphibian mesonephros as a more primitive kidney compared to mammalian metanephros.
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15
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Gburek J, Konopska B, Gołąb K. Renal Handling of Albumin-From Early Findings to Current Concepts. Int J Mol Sci 2021; 22:ijms22115809. [PMID: 34071680 PMCID: PMC8199105 DOI: 10.3390/ijms22115809] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Revised: 05/20/2021] [Accepted: 05/25/2021] [Indexed: 12/29/2022] Open
Abstract
Albumin is the main protein of blood plasma, lymph, cerebrospinal and interstitial fluid. The protein participates in a variety of important biological functions, such as maintenance of proper colloidal osmotic pressure, transport of important metabolites and antioxidant action. Synthesis of albumin takes place mainly in the liver, and its catabolism occurs mostly in vascular endothelium of muscle, skin and liver, as well as in the kidney tubular epithelium. Long-lasting investigation in this area has delineated the principal route of its catabolism involving glomerular filtration, tubular endocytic uptake via the multiligand scavenger receptor tandem—megalin and cubilin-amnionless complex, as well as lysosomal degradation to amino acids. However, the research of the last few decades indicates that also additional mechanisms may operate in this process to some extent. Direct uptake of albumin in glomerular podocytes via receptor for crystallizable region of immunoglobulins (neonatal FC receptor) was demonstrated. Additionally, luminal recycling of short peptides into the bloodstream and/or back into tubular lumen or transcytosis of whole molecules was suggested. The article discusses the molecular aspects of these processes and presents the major findings and controversies arising in the light of the research concerning the last decade. Their better characterization is essential for further research into pathophysiology of proteinuric renal failure and development of effective therapeutic strategies.
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16
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Prutskova NP, Seliverstova EV. The Effect of Protein Overload on
Reabsorption of Different Proteins in Frog Renal Tubules. J EVOL BIOCHEM PHYS+ 2021. [DOI: 10.1134/s0022093021010105] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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17
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Tokhmafshan F, Dickinson K, Akpa MM, Brasell E, Huertas P, Goodyer PR. A no-nonsense approach to hereditary kidney disease. Pediatr Nephrol 2020; 35:2031-2042. [PMID: 31807928 DOI: 10.1007/s00467-019-04394-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 07/05/2019] [Accepted: 10/07/2019] [Indexed: 01/12/2023]
Abstract
The advent of a new class of aminoglycosides with increased translational readthrough of nonsense mutations and reduced toxicity offers a new therapeutic strategy for a subset of patients with hereditary kidney disease. The renal uptake and retention of aminoglycosides at a high intracellular concentration makes the kidney an ideal target for this approach. In this review, we explore the potential of aminoglycoside readthrough therapy in a number of hereditary kidney diseases and discuss the therapeutic window of opportunity for subclasses of each disease, when caused by nonsense mutations.
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Affiliation(s)
- Fatima Tokhmafshan
- Research Institute of the McGill University Health Center, 1001 Décarie Boulevard, EM1.2232, Montreal, QC, H4A 3J1, Canada
| | - Kyle Dickinson
- Research Institute of the McGill University Health Center, 1001 Décarie Boulevard, EM1.2232, Montreal, QC, H4A 3J1, Canada.,Department of Experimental Medicine, McGill University, Montreal, Canada
| | - Murielle M Akpa
- Research Institute of the McGill University Health Center, 1001 Décarie Boulevard, EM1.2232, Montreal, QC, H4A 3J1, Canada
| | - Emma Brasell
- Department of Human Genetics, McGill University, Montreal, Canada
| | | | - Paul R Goodyer
- Research Institute of the McGill University Health Center, 1001 Décarie Boulevard, EM1.2232, Montreal, QC, H4A 3J1, Canada. .,Department of Experimental Medicine, McGill University, Montreal, Canada. .,Department of Human Genetics, McGill University, Montreal, Canada. .,Department of Pediatrics, McGill University, Montreal, Canada.
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18
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Selma-Soriano E, Llamusi B, Fernández-Costa JM, Ozimski LL, Artero R, Redón J. Rabphilin involvement in filtration and molecular uptake in Drosophila nephrocytes suggests a similar role in human podocytes. Dis Model Mech 2020; 13:dmm041509. [PMID: 32680845 PMCID: PMC7522021 DOI: 10.1242/dmm.041509] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Accepted: 07/07/2020] [Indexed: 02/04/2023] Open
Abstract
Drosophila nephrocytes share functional, structural and molecular similarities with human podocytes. It is known that podocytes express the rabphilin 3A (RPH3A)-RAB3A complex, and its expression is altered in mouse and human proteinuric disease. Furthermore, we previously identified a polymorphism that suggested a role for RPH3A protein in the development of urinary albumin excretion. As endocytosis and vesicle trafficking are fundamental pathways for nephrocytes, the objective of this study was to assess the role of the RPH3A orthologue in Drosophila, Rabphilin (Rph), in the structure and function of nephrocytes. We confirmed that Rph is required for the correct function of the endocytic pathway in pericardial Drosophila nephrocytes. Knockdown of Rph reduced the expression of the cubilin and stick and stones genes, which encode proteins that are involved in protein uptake and filtration. We also found that reduced Rph expression resulted in a disappearance of the labyrinthine channel structure and a reduction in the number of endosomes, which ultimately leads to changes in the number and volume of nephrocytes. Finally, we demonstrated that the administration of retinoic acid to IR-Rph nephrocytes rescued some altered aspects, such as filtration and molecular uptake, as well as the maintenance of cell fate. According to our data, Rph is crucial for nephrocyte filtration and reabsorption, and it is required for the maintenance of the ultrastructure, integrity and differentiation of the nephrocyte.
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Affiliation(s)
- Estela Selma-Soriano
- Translational Genomics Group, Incliva Health Research Institute, 46010 Valencia, Spain
- Interdisciplinary Research Structure for Biotechnology and Biomedicine (ERI BIOTECMED), University of Valencia, 46100 Valencia, Spain
- CIPF-INCLIVA Joint Unit, 46010 Valencia, Spain
| | - Beatriz Llamusi
- Translational Genomics Group, Incliva Health Research Institute, 46010 Valencia, Spain
- Interdisciplinary Research Structure for Biotechnology and Biomedicine (ERI BIOTECMED), University of Valencia, 46100 Valencia, Spain
- CIPF-INCLIVA Joint Unit, 46010 Valencia, Spain
| | - Juan Manuel Fernández-Costa
- Translational Genomics Group, Incliva Health Research Institute, 46010 Valencia, Spain
- Interdisciplinary Research Structure for Biotechnology and Biomedicine (ERI BIOTECMED), University of Valencia, 46100 Valencia, Spain
- CIPF-INCLIVA Joint Unit, 46010 Valencia, Spain
| | - Lauren Louise Ozimski
- Translational Genomics Group, Incliva Health Research Institute, 46010 Valencia, Spain
- Interdisciplinary Research Structure for Biotechnology and Biomedicine (ERI BIOTECMED), University of Valencia, 46100 Valencia, Spain
- CIPF-INCLIVA Joint Unit, 46010 Valencia, Spain
| | - Rubén Artero
- Translational Genomics Group, Incliva Health Research Institute, 46010 Valencia, Spain
- Interdisciplinary Research Structure for Biotechnology and Biomedicine (ERI BIOTECMED), University of Valencia, 46100 Valencia, Spain
- CIPF-INCLIVA Joint Unit, 46010 Valencia, Spain
| | - Josep Redón
- Hypertension Unit, Hospital Clínico Universitario, 46010 Valencia, Spain
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19
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Gianesello L, Del Prete D, Anglani F, Calò LA. Genetics and phenotypic heterogeneity of Dent disease: the dark side of the moon. Hum Genet 2020; 140:401-421. [PMID: 32860533 PMCID: PMC7889681 DOI: 10.1007/s00439-020-02219-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Accepted: 08/20/2020] [Indexed: 12/18/2022]
Abstract
Dent disease is a rare genetic proximal tubulopathy which is under-recognized. Its phenotypic heterogeneity has led to several different classifications of the same disorder, but it is now widely accepted that the triad of symptoms low-molecular-weight proteinuria, hypercalciuria and nephrocalcinosis/nephrolithiasis are pathognomonic of Dent disease. Although mutations on the CLCN5 and OCRL genes are known to cause Dent disease, no such mutations are found in about 25–35% of cases, making diagnosis more challenging. This review outlines current knowledge regarding Dent disease from another perspective. Starting from the history of Dent disease, and reviewing the clinical details of patients with and without a genetic characterization, we discuss the phenotypic and genetic heterogeneity that typifies this disease. We focus particularly on all those confounding clinical signs and symptoms that can lead to a misdiagnosis. We also try to shed light on a concealed aspect of Dent disease. Although it is a proximal tubulopathy, its misdiagnosis may lead to patients undergoing kidney biopsy. In fact, some individuals with Dent disease have high-grade proteinuria, with or without hematuria, as in the clinical setting of glomerulopathy, or chronic kidney disease of uncertain origin. Although glomerular damage is frequently documented in Dent disease patients’ biopsies, there is currently no reliable evidence of renal biopsy being of either diagnostic or prognostic value. We review published histopathology reports of tubular and glomerular damage in these patients, and discuss current knowledge regarding the role of CLCN5 and OCRL genes in glomerular function.
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Affiliation(s)
- Lisa Gianesello
- Nephrology, Dialysis and Transplantation Unit, Kidney Histomorphology and Molecular Biology Laboratory, Department of Medicine-DIMED, University of Padua, Via Giustiniani n° 2, 35128, Padua, Italy
| | - Dorella Del Prete
- Nephrology, Dialysis and Transplantation Unit, Kidney Histomorphology and Molecular Biology Laboratory, Department of Medicine-DIMED, University of Padua, Via Giustiniani n° 2, 35128, Padua, Italy
| | - Franca Anglani
- Nephrology, Dialysis and Transplantation Unit, Kidney Histomorphology and Molecular Biology Laboratory, Department of Medicine-DIMED, University of Padua, Via Giustiniani n° 2, 35128, Padua, Italy.
| | - Lorenzo A Calò
- Nephrology, Dialysis and Transplantation Unit, Kidney Histomorphology and Molecular Biology Laboratory, Department of Medicine-DIMED, University of Padua, Via Giustiniani n° 2, 35128, Padua, Italy
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20
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Bryniarski MA, Yee BM, Chaves LD, Stahura CM, Yacoub R, Morris ME. Megalin-mediated albumin endocytosis in cultured murine mesangial cells. Biochem Biophys Res Commun 2020; 529:740-746. [PMID: 32736701 DOI: 10.1016/j.bbrc.2020.05.166] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Accepted: 05/22/2020] [Indexed: 12/25/2022]
Abstract
Endocytosis by podocytes is gaining increased attention as a biologic means of removing large proteins such as serum albumin from the glomerular barrier. Some of this function has been attributed to the megalin/cubilin (Lrp2/Cubn) receptor complex and the albumin recycling protein FcRn (Fcgrt). However, whether other glomerular cells possess the potential to perform this same phenomenon or express these proteins remains uncharacterized. Mesangial cells are uniquely positioned in glomeruli and represent a cell type capable of performing several diverse functions. Here, the expression of megalin and FcRn in murine mesangial cells along with the megalin adaptor protein Dab-2 (Dab2) was shown for the first time. Cubilin mRNA expression was detected, but the absence of the cubilin partner amnionless (Amn) suggested that cubilin is minimally functional, if at all, in these cells. Mesangial cell endocytosis of albumin was characterized and shown to involve a receptor-mediated process. Albumin endocytosis was significantly impaired (p < 0.01) under inducible megalin knockdown conditions in stably transduced mesangial cells. The current work provides both the novel identification of megalin and FcRn in mesangial cells and the functional demonstration of megalin-mediated albumin endocytosis.
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Affiliation(s)
- Mark A Bryniarski
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo, 303 Pharmacy Building, Buffalo, NY, 14214, USA
| | - Benjamin M Yee
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo, 303 Pharmacy Building, Buffalo, NY, 14214, USA
| | - Lee D Chaves
- Department of Internal Medicine, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, 875 Ellicott St, Buffalo, NY, 14214, USA
| | - Corrine M Stahura
- Department of Internal Medicine, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, 875 Ellicott St, Buffalo, NY, 14214, USA
| | - Rabi Yacoub
- Department of Internal Medicine, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, 875 Ellicott St, Buffalo, NY, 14214, USA
| | - Marilyn E Morris
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo, 303 Pharmacy Building, Buffalo, NY, 14214, USA.
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21
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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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22
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Gianesello L, Del Prete D, Ceol M, Priante G, Calò LA, Anglani F. From protein uptake to Dent disease: An overview of the CLCN5 gene. Gene 2020; 747:144662. [PMID: 32289351 DOI: 10.1016/j.gene.2020.144662] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 04/07/2020] [Indexed: 12/12/2022]
Abstract
Proteinuria is a well-known risk factor, not only for renal disorders, but also for several other problems such as cardiovascular diseases and overall mortality. In the kidney, the chloride channel Cl-/H+ exchanger ClC-5 encoded by the CLCN5 gene is actively involved in preventing protein loss. This action becomes evident in patients suffering from the rare proximal tubulopathy Dent disease because they carry a defective ClC-5 due to CLCN5 mutations. In fact, proteinuria is the distinctive clinical sign of Dent disease, and mainly involves the loss of low-molecular-weight proteins. The identification of CLCN5 disease-causing mutations has greatly improved our understanding of ClC-5 function and of the ClC-5-related physiological processes in the kidney. This review outlines current knowledge regarding the CLCN5 gene and its protein product, providing an update on ClC-5 function in tubular and glomerular cells, and focusing on its relationship with proteinuria and Dent disease.
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Affiliation(s)
- Lisa Gianesello
- Kidney Histomorphology and Molecular Biology Laboratory, Clinical Nephrology Unit, Department of Medicine - DIMED, University of Padua, Padua, Italy.
| | - Dorella Del Prete
- Kidney Histomorphology and Molecular Biology Laboratory, Clinical Nephrology Unit, Department of Medicine - DIMED, University of Padua, Padua, Italy.
| | - Monica Ceol
- Kidney Histomorphology and Molecular Biology Laboratory, Clinical Nephrology Unit, Department of Medicine - DIMED, University of Padua, Padua, Italy.
| | - Giovanna Priante
- Kidney Histomorphology and Molecular Biology Laboratory, Clinical Nephrology Unit, Department of Medicine - DIMED, University of Padua, Padua, Italy.
| | - Lorenzo Arcangelo Calò
- Kidney Histomorphology and Molecular Biology Laboratory, Clinical Nephrology Unit, Department of Medicine - DIMED, University of Padua, Padua, Italy.
| | - Franca Anglani
- Kidney Histomorphology and Molecular Biology Laboratory, Clinical Nephrology Unit, Department of Medicine - DIMED, University of Padua, Padua, Italy.
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23
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Sekulic M, Waikar S, Motwani SS, Weins A, Rennke HG. Chromogranin A Tubulopathy: Differing Histopathologic Patterns of Acute Tubular Injury in the Setting of Neuroendocrine Neoplasms. Kidney Int Rep 2019; 4:1085-1093. [PMID: 31440699 PMCID: PMC6698283 DOI: 10.1016/j.ekir.2019.04.025] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Accepted: 04/29/2019] [Indexed: 02/01/2023] Open
Abstract
Introduction Neoplasms of neuroendocrine derivation or differentiation may express specific peptides, some of which are capable of producing clinical symptomatology and others used as biomarkers: one such peptide being chromogranin A (CGA). Herein, we describe histopathologic changes present in kidney specimens from patients with such neoplasms, and illustrate 2 patterns of acute tubular injury (ATI) attributable to CGA. Methods Eleven patients with a history of a neoplasm of neuroendocrine derivation or differentiation and having histopathologic sampling of the kidney were retrospectively identified, 3 of whom had ATI with either engorgement of the proximal tubular epithelium by resorbed material or tubular cast formation. Results Two patterns of ATI were observed. One characterized by acutely injured proximal tubular cells engorged with resorption granules that expressed CGA via immunoperoxidase staining. Another pattern was characterized by intraluminal tubular cast material associated with ATI that did not exhibit restriction of immunoglobulin light chains (LCs), but immunoperoxidase staining for CGA revealed that the cast material was composed of the neuroendocrine-associated peptide. The level of serum CGA does not appear to necessarily equate to developing either of these 2 patterns of ATI. Conclusions Patients with a neoplasm of neuroendocrine derivation or differentiation may develop ATI, and in certain cases may be secondary to CGA renal tubular deposition.
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Affiliation(s)
- Miroslav Sekulic
- Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Sushrut Waikar
- Division of Nephrology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Shveta S Motwani
- Division of Nephrology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Astrid Weins
- Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Helmut G Rennke
- Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
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24
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Gianesello L, Anglani F, Del Prete D. Protein uptake at glomerular level: is it just the work of podocytes? Nephrol Dial Transplant 2019; 35:1675-1677. [DOI: 10.1093/ndt/gfz127] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Indexed: 11/14/2022] Open
Affiliation(s)
- Lisa Gianesello
- Clinical Nephrology Unit, Department of Medicine DIMED, Kidney Histomorphology and Molecular Biology Laboratory, University of Padua, Padua, Italy
| | - Franca Anglani
- Clinical Nephrology Unit, Department of Medicine DIMED, Kidney Histomorphology and Molecular Biology Laboratory, University of Padua, Padua, Italy
| | - Dorella Del Prete
- Clinical Nephrology Unit, Department of Medicine DIMED, Kidney Histomorphology and Molecular Biology Laboratory, University of Padua, Padua, Italy
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25
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Fels J, Scharner B, Zarbock R, Zavala Guevara IP, Lee WK, Barbier OC, Thévenod F. Cadmium Complexed with β2-Microglubulin, Albumin and Lipocalin-2 rather than Metallothionein Cause Megalin:Cubilin Dependent Toxicity of the Renal Proximal Tubule. Int J Mol Sci 2019; 20:ijms20102379. [PMID: 31091675 PMCID: PMC6566203 DOI: 10.3390/ijms20102379] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2019] [Revised: 05/03/2019] [Accepted: 05/09/2019] [Indexed: 11/25/2022] Open
Abstract
Cadmium (Cd2+) in the environment is a significant health hazard. Chronic low Cd2+ exposure mainly results from food and tobacco smoking and causes kidney damage, predominantly in the proximal tubule. Blood Cd2+ binds to thiol-containing high (e.g., albumin, transferrin) and low molecular weight proteins (e.g., the high-affinity metal-binding protein metallothionein, β2-microglobulin, α1-microglobulin and lipocalin-2). These plasma proteins reach the glomerular filtrate and are endocytosed at the proximal tubule via the multiligand receptor complex megalin:cubilin. The current dogma of chronic Cd2+ nephrotoxicity claims that Cd2+-metallothionein endocytosed via megalin:cubilin causes renal damage. However, a thorough study of the literature strongly argues for revision of this model for various reasons, mainly: (i) It relied on studies with unusually high Cd2+-metallothionein concentrations; (ii) the KD of megalin for metallothionein is ~105-times higher than (Cd2+)-metallothionein plasma concentrations. Here we investigated the uptake and toxicity of ultrafiltrated Cd2+-binding protein ligands that are endocytosed via megalin:cubilin in the proximal tubule. Metallothionein, β2-microglobulin, α1-microglobulin, lipocalin-2, albumin and transferrin were investigated, both as apo- and Cd2+-protein complexes, in a rat proximal tubule cell line (WKPT-0293 Cl.2) expressing megalin:cubilin at low passage, but is lost at high passage. Uptake was determined by fluorescence microscopy and toxicity by MTT cell viability assay. Apo-proteins in low and high passage cells as well as Cd2+-protein complexes in megalin:cubilin deficient high passage cells did not affect cell viability. The data prove Cd2+-metallothionein is not toxic, even at >100-fold physiological metallothionein concentrations in the primary filtrate. Rather, Cd2+-β2-microglobulin, Cd2+-albumin and Cd2+-lipocalin-2 at concentrations present in the primary filtrate are taken up by low passage proximal tubule cells and cause toxicity. They are therefore likely candidates of Cd2+-protein complexes damaging the proximal tubule via megalin:cubilin at concentrations found in the ultrafiltrate.
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Affiliation(s)
- Johannes Fels
- Department of Physiology, Pathophysiology & Toxicology and ZBAF (Centre for Biomedical Education and Research), Faculty of Health, School of Medicine, Witten/Herdecke University, D-58453 Witten, Germany.
| | - Bettina Scharner
- Department of Physiology, Pathophysiology & Toxicology and ZBAF (Centre for Biomedical Education and Research), Faculty of Health, School of Medicine, Witten/Herdecke University, D-58453 Witten, Germany.
| | - Ralf Zarbock
- Department of Physiology, Pathophysiology & Toxicology and ZBAF (Centre for Biomedical Education and Research), Faculty of Health, School of Medicine, Witten/Herdecke University, D-58453 Witten, Germany.
| | - Itzel Pamela Zavala Guevara
- Departamento de Toxicología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN), Mexico 07360, México.
| | - Wing-Kee Lee
- Department of Physiology, Pathophysiology & Toxicology and ZBAF (Centre for Biomedical Education and Research), Faculty of Health, School of Medicine, Witten/Herdecke University, D-58453 Witten, Germany.
| | - Olivier C Barbier
- Departamento de Toxicología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN), Mexico 07360, México.
| | - Frank Thévenod
- Department of Physiology, Pathophysiology & Toxicology and ZBAF (Centre for Biomedical Education and Research), Faculty of Health, School of Medicine, Witten/Herdecke University, D-58453 Witten, Germany.
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26
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Zhao X, Chen X, Chima A, Zhang Y, George J, Cobbs A, Emmett N. Albumin induces CD44 expression in glomerular parietal epithelial cells by activating extracellular signal-regulated kinase 1/2 pathway. J Cell Physiol 2019; 234:7224-7235. [PMID: 30362534 PMCID: PMC6344259 DOI: 10.1002/jcp.27477] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Accepted: 09/04/2018] [Indexed: 01/21/2023]
Abstract
De novo expression of CD44 in glomerular parietal epithelial cells (PECs) leads to a prosclerotic and migratory PEC phenotype in glomerulosclerosis. However, the regulatory mechanisms underlying CD44 expression by activated PECs remain largely unknown. This study was performed to examine the mediators responsible for CD44 induction in glomerular PECs in association with diabetes. CD44 expression and localization were evaluated in the glomeruli of Zucker diabetic rat kidneys and primary cultured PECs upon albumin stimulation. Real-time polymerase chain reaction confirmed an albuminuria-associated upregulation of the CD44 gene in the glomeruli of diabetic rats. Immunostaining analysis of diabetic kidneys further revealed an increase in CD44 in hypertrophic PECs, which often contain albumin-positive vesicles. Losartan treatment significantly attenuated albuminuria and lowered CD44 protein levels in the diabetic kidneys. In primary cultured rat PECs, rat serum albumin (0.25-1 mg/ml) caused a dose-dependent upregulation of CD44, claudin-1, and megalin protein expression, which was accompanied by an activation of extracellular signal-regulated kinase1/2 (ERK1/2) signaling. Albumin-induced CD44 and claudin-1 expression were greatly suppressed in the presence of the ERK1/2 inhibitor, U0126. In addition, knockdown of megalin by small interfering RNA interference in PECs resulted in a significant reduction of albumin-induced CD44 and claudin-1 proteins. Taken together, our results demonstrate that albumin induces CD44 expression by PECs via the activation of the ERK signaling pathway, which is partially mediated by endocytic receptor megalin.
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Affiliation(s)
- Xueying Zhao
- Department of Physiology, Morehouse School of Medicine, Atlanta, Georgia
| | - Xiaoming Chen
- Department of Physiology, Morehouse School of Medicine, Atlanta, Georgia
| | - Ashmeer Chima
- Department of Physiology, Morehouse School of Medicine, Atlanta, Georgia
| | - Yuanyuan Zhang
- Department of Physiology, Morehouse School of Medicine, Atlanta, Georgia
| | - Jasmine George
- Department of Physiology, Morehouse School of Medicine, Atlanta, Georgia
| | - Alyssa Cobbs
- Department of Physiology, Morehouse School of Medicine, Atlanta, Georgia
| | - Nerimiah Emmett
- Department of Physiology, Morehouse School of Medicine, Atlanta, Georgia
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27
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Beara-Lasic L, Cogal A, Mara K, Enders F, Mehta RA, Haskic Z, Furth SL, Trachtman H, Scheinman SJ, Milliner DS, Goldfarb DS, Harris PC, Lieske JC. Prevalence of low molecular weight proteinuria and Dent disease 1 CLCN5 mutations in proteinuric cohorts. Pediatr Nephrol 2019; 35:633-640. [PMID: 30852663 PMCID: PMC6736764 DOI: 10.1007/s00467-019-04210-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Revised: 01/25/2019] [Accepted: 02/04/2019] [Indexed: 01/05/2023]
Abstract
BACKGROUND Dent disease type 1 (DD1) is a rare X-linked disorder caused mainly by CLCN5 mutations. Patients may present with nephrotic-range proteinuria leading to erroneous diagnosis of focal segmental glomerulosclerosis (FSGS) and unnecessary immunosuppressive treatments. METHODS The following cohorts were screened for CLCN5 mutations: Chronic Kidney Disease in Children (CKiD; n = 112); Multicenter FSGS-Clinical Trial (FSGS-CT) (n = 96), and Novel Therapies for Resistant FSGS Trial (FONT) (n = 30). Urinary α1-microglobulin (α1M), albumin (A), total protein (TP), and creatinine (Cr) were assessed from CKiD subjects (n = 104); DD1 patients (n = 14); and DD1 carriers (DC; n = 8). TP/Cr, α1M/Cr, α1M/TP, and A/TP from the CKiD cohort were compared with DD1 and DC. RESULTS No CLCN5 mutations were detected. TP/Cr was lower in DC and CKiD with tubulointerstitial disease than in DD1 and CKiD with glomerular disease (p < 0.002). α1M/Cr was higher in DD1 than in CKiD and DC (p < 0.001). A/TP was lower in DD1, DC, and CKiD with tubulointerstitial disease and higher in CKiD with glomerular disease (p < 0.001). Thresholds for A/TP of ≤ 0.21 and α1M/Cr of ≥ 120 mg/g (> 13.6 mg/mmol) creatinine were good screens for Dent disease. CONCLUSIONS CLCN5 mutations were not seen in screened CKiD/FSGS cohorts. In our study, a cutoff of TP/Cr > 600 mg/g (> 68 mg/mmol) and A/TP of < 0.3 had a high sensitivity and specificity to distinguish DD1 from both CKiD glomerular and tubulointerstitial cohorts. α1M/Cr ≥ 120 mg/g (> 13.6 mg/mmol) had the highest sensitivity and specificity when differentiating DD1 and studied CKiD populations.
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Affiliation(s)
- Lada Beara-Lasic
- Nephrology Division, Department of Medicine and Pediatrics, New York University Langone Health and New York University School of Medicine, New York, NY, USA.
- Rare Kidney Stone Consortium, Rochester, USA.
| | - Andrea Cogal
- Rare Kidney Stone Consortium, Rochester, USA
- Division of Nephrology, Department of Medicine and Pediatrics, Mayo Clinic, Rochester, MN, USA
| | - Kristin Mara
- Rare Kidney Stone Consortium, Rochester, USA
- Division of Biomedical Statistics and Informatics, Mayo Clinic, Rochester, MN, USA
| | - Felicity Enders
- Rare Kidney Stone Consortium, Rochester, USA
- Division of Biomedical Statistics and Informatics, Mayo Clinic, Rochester, MN, USA
| | - Ramila A Mehta
- Rare Kidney Stone Consortium, Rochester, USA
- Division of Biomedical Statistics and Informatics, Mayo Clinic, Rochester, MN, USA
| | - Zejfa Haskic
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA
| | - Susan L Furth
- Department of Pediatrics, Children's Hospital of Philadelphia, University of Pennsylvania Perelman, School of Medicine, Philadelphia, PA, USA
| | - Howard Trachtman
- Nephrology Division, Department of Medicine and Pediatrics, New York University Langone Health and New York University School of Medicine, New York, NY, USA
| | | | - Dawn S Milliner
- Rare Kidney Stone Consortium, Rochester, USA
- Division of Nephrology, Department of Medicine and Pediatrics, Mayo Clinic, Rochester, MN, USA
| | - David S Goldfarb
- Nephrology Division, Department of Medicine and Pediatrics, New York University Langone Health and New York University School of Medicine, New York, NY, USA
- Rare Kidney Stone Consortium, Rochester, USA
| | - Peter C Harris
- Rare Kidney Stone Consortium, Rochester, USA
- Division of Nephrology, Department of Medicine and Pediatrics, Mayo Clinic, Rochester, MN, USA
| | - John C Lieske
- Rare Kidney Stone Consortium, Rochester, USA
- Division of Nephrology, Department of Medicine and Pediatrics, Mayo Clinic, Rochester, MN, USA
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28
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Intracellular albumin overload elicits endoplasmic reticulum stress and PKC-delta/p38 MAPK pathway activation to induce podocyte apoptosis. Sci Rep 2018; 8:18012. [PMID: 30573754 PMCID: PMC6301950 DOI: 10.1038/s41598-018-36933-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Accepted: 11/29/2018] [Indexed: 12/22/2022] Open
Abstract
Podocyte injury is closely related to proteinuria and the progression of chronic kidney disease (CKD). Currently, there is no conclusive understanding about the mechanisms involved in albumin overload and podocyte apoptosis response. In this study, we sought to explore the ways by which intracellular albumin can mediate podocyte apoptosis. Here, immortalized mouse podocytes were treated with bovine serum albumin (BSA) at different times and concentrations, in the presence or absence of SB203580 (0.1 µM, inhibitor of mitogen-activated-protein kinase – p38MAPK). Using immunofluorescence images, flow cytometry and immunoblotting, we observed a time-dependent intracellular accumulation of fluorescent albumin-FITC-BSA, followed by concentration-and time-dependent effect of intracellular albumin overload on podocyte apoptosis, which was mediated by increased expression of the chaperone glucose-regulated-protein 78 (GRP 78) and phosphorylated inositol-requiring enzyme 1 alpha (pIRE1-α), as well as protein kinase C delta (PKC-δ), p38MAPK and cleaved caspase 12 expression. SB203580 prevented the cleavage of caspase 12 and the albumin-mediated podocyte apoptosis. These results suggest that intracellular albumin overload is associated with endoplasmic reticulum (ER) stress and upregulation of PKC-δ/p38MAPK/caspase 12 pathway, which may be a target for future therapeutic of albumin-induced podocyte apoptosis.
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29
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Kozyraki R, Cases O. Cubilin, the Intrinsic Factor-Vitamin B12 Receptor in Development and Disease. Curr Med Chem 2018; 27:3123-3150. [PMID: 30295181 DOI: 10.2174/0929867325666181008143945] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2018] [Revised: 08/11/2018] [Accepted: 08/21/2018] [Indexed: 12/29/2022]
Abstract
Gp280/Intrinsic factor-vitamin B12 receptor/Cubilin (CUBN) is a large endocytic receptor serving multiple functions in vitamin B12 homeostasis, renal reabsorption of protein or toxic substances including albumin, vitamin D-binding protein or cadmium. Cubilin is a peripheral membrane protein consisting of 8 Epidermal Growth Factor (EGF)-like repeats and 27 CUB (defined as Complement C1r/C1s, Uegf, BMP1) domains. This structurally unique protein interacts with at least two molecular partners, Amnionless (AMN) and Lrp2/Megalin. AMN is involved in appropriate plasma membrane transport of Cubilin whereas Lrp2 is essential for efficient internalization of Cubilin and its ligands. Observations gleaned from animal models with Cubn deficiency or human diseases demonstrate the importance of this protein. In this review addressed to basic research and medical scientists, we summarize currently available data on Cubilin and its implication in renal and intestinal biology. We also discuss the role of Cubilin as a modulator of Fgf8 signaling during embryonic development and propose that the Cubilin-Fgf8 interaction may be relevant in human pathology, including in cancer progression, heart or neural tube defects. We finally provide experimental elements suggesting that some aspects of Cubilin physiology might be relevant in drug design.
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Affiliation(s)
- Renata Kozyraki
- INSERM UMRS 1138, Centre de Recherche des Cordeliers, Paris-Diderot University, Paris, France
| | - Olivier Cases
- INSERM UMRS 1138, Centre de Recherche des Cordeliers, Paris-Diderot University, Paris, France
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30
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Figueira MF, Castiglione RC, de Lemos Barbosa CM, Ornellas FM, da Silva Feltran G, Morales MM, da Fonseca RN, de Souza-Menezes J. Diabetic rats present higher urinary loss of proteins and lower renal expression of megalin, cubilin, ClC-5, and CFTR. Physiol Rep 2018; 5:5/13/e13335. [PMID: 28676554 PMCID: PMC5506523 DOI: 10.14814/phy2.13335] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Revised: 05/25/2017] [Accepted: 05/26/2017] [Indexed: 01/27/2023] Open
Abstract
Diabetic nephropathy (DN) occurs in around 40% of those with diabetes. Proteinuria is the main characteristic of DN and develops as a result of increased permeability of the glomerulus capillary wall and/or decreased proximal tubule endocytosis. The goal of this work was to evaluate renal function and the expression of megalin, cubilin, CFTR (cystic fibrosis transmembrane conductance regulator), and ClC-5 in the proximal tubule and renal cortex of rats with type 1 diabetes. Male Wistar rats were randomly assigned to control (CTRL) and diabetic (DM) groups for 4 weeks. Renal function was assessed in 24-h urine sample by calculating clearance and fractional excretion of solutes. The RNA and protein contents of ClC-5, CFTR, megalin, and cubilin were determined in the renal proximal tubule and cortex using real-time polymerase chain reaction and western blotting techniques, respectively. The results showed higher creatinine clearance and higher urinary excretion of proteins, albumin, and transferrin in the DM group than in the CTRL group. Furthermore, the renal cortex and proximal tubule of diabetic animals showed downregulation of megalin, cubilin, ClC-5, and CFTR, critical components of the endocytic apparatus. These data suggest dysfunction in proximal tubule low-molecular-weight endocytosis and protein glomerulus filtration in the kidney of diabetic rats.
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Affiliation(s)
- Miriam F Figueira
- Laboratório Integrado de Ciências Morfofuncionais, Núcleo em Ecologia e Desenvolvimento Socioambiental de Macaé, Universidade Federal do Rio de Janeiro, Macaé, Rio de Janeiro, Brazil.,Laboratório de Fisiologia Celular e Molecular, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Raquel C Castiglione
- Laboratório de Fisiologia Celular e Molecular, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.,Instituto de Biologia Roberto Alcântara Gomes, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, Brazil
| | - Carolina M de Lemos Barbosa
- Laboratório de Fisiologia Celular e Molecular, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.,Instituto de Biologia Roberto Alcântara Gomes, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, Brazil
| | - Felipe M Ornellas
- Laboratório de Fisiologia Celular e Molecular, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Geórgia da Silva Feltran
- Laboratório Integrado de Ciências Morfofuncionais, Núcleo em Ecologia e Desenvolvimento Socioambiental de Macaé, Universidade Federal do Rio de Janeiro, Macaé, Rio de Janeiro, Brazil
| | - Marcelo M Morales
- Laboratório de Fisiologia Celular e Molecular, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Rodrigo N da Fonseca
- Laboratório Integrado de Ciências Morfofuncionais, Núcleo em Ecologia e Desenvolvimento Socioambiental de Macaé, Universidade Federal do Rio de Janeiro, Macaé, Rio de Janeiro, Brazil
| | - Jackson de Souza-Menezes
- Laboratório Integrado de Ciências Morfofuncionais, Núcleo em Ecologia e Desenvolvimento Socioambiental de Macaé, Universidade Federal do Rio de Janeiro, Macaé, Rio de Janeiro, Brazil
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Rubio-Navarro A, Sanchez-Niño MD, Guerrero-Hue M, García-Caballero C, Gutiérrez E, Yuste C, Sevillano Á, Praga M, Egea J, Román E, Cannata P, Ortega R, Cortegano I, de Andrés B, Gaspar ML, Cadenas S, Ortiz A, Egido J, Moreno JA. Podocytes are new cellular targets of haemoglobin-mediated renal damage. J Pathol 2018; 244:296-310. [PMID: 29205354 DOI: 10.1002/path.5011] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Revised: 10/27/2017] [Accepted: 11/21/2017] [Indexed: 01/02/2023]
Abstract
Recurrent and massive intravascular haemolysis induces proteinuria, glomerulosclerosis, and progressive impairment of renal function, suggesting podocyte injury. However, the effects of haemoglobin (Hb) on podocytes remain unexplored. Our results show that cultured human podocytes or podocytes isolated from murine glomeruli bound and endocytosed Hb through the megalin-cubilin receptor system, thus resulting in increased intracellular Hb catabolism, oxidative stress, activation of the intrinsic apoptosis pathway, and altered podocyte morphology, with decreased expression of the slit diaphragm proteins nephrin and synaptopodin. Hb uptake activated nuclear factor erythroid-2-related factor 2 (Nrf2) and induced expression of the Nrf2-related antioxidant proteins haem oxygenase-1 (HO-1) and ferritin. Nrf2 activation and Hb staining was observed in podocytes of mice with intravascular haemolysis. These mice developed proteinuria and showed podocyte injury, characterized by foot process effacement, decreased synaptopodin and nephrin expression, and podocyte apoptosis. These pathological effects were enhanced in Nrf2-deficient mice, whereas Nrf2 activation with sulphoraphane protected podocytes against Hb toxicity both in vivo and in vitro. Supporting the translational significance of our findings, we observed podocyte damage and podocytes stained for Hb, HO-1, ferritin and phosphorylated Nrf2 in renal sections and urinary sediments of patients with massive intravascular haemolysis, such as atypical haemolytic uraemic syndrome and paroxysmal nocturnal haemoglobinuria. In conclusion, podocytes take up Hb both in vitro and during intravascular haemolysis, promoting oxidative stress, podocyte dysfunction, and apoptosis. Nrf2 may be a potential therapeutic target to prevent loss of renal function in patients with intravascular haemolysis. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
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Affiliation(s)
- Alfonso Rubio-Navarro
- Renal, Vascular and Diabetes Research Laboratory, Fundación Instituto de Investigación Sanitaria-Fundación Jiménez Díaz, Autónoma University, Madrid, Spain
| | - Maria Dolores Sanchez-Niño
- Renal, Vascular and Diabetes Research Laboratory, Fundación Instituto de Investigación Sanitaria-Fundación Jiménez Díaz, Autónoma University, Madrid, Spain.,Red de Investigación Renal (REDINREN), Madrid, Spain
| | - Melania Guerrero-Hue
- Renal, Vascular and Diabetes Research Laboratory, Fundación Instituto de Investigación Sanitaria-Fundación Jiménez Díaz, Autónoma University, Madrid, Spain
| | - Cristina García-Caballero
- Renal, Vascular and Diabetes Research Laboratory, Fundación Instituto de Investigación Sanitaria-Fundación Jiménez Díaz, Autónoma University, Madrid, Spain
| | - Eduardo Gutiérrez
- Red de Investigación Renal (REDINREN), Madrid, Spain.,Department of Nephrology, Hospital 12 de Octubre, Madrid, Spain
| | - Claudia Yuste
- Red de Investigación Renal (REDINREN), Madrid, Spain.,Department of Nephrology, Hospital 12 de Octubre, Madrid, Spain
| | - Ángel Sevillano
- Red de Investigación Renal (REDINREN), Madrid, Spain.,Department of Nephrology, Hospital 12 de Octubre, Madrid, Spain
| | - Manuel Praga
- Red de Investigación Renal (REDINREN), Madrid, Spain.,Department of Nephrology, Hospital 12 de Octubre, Madrid, Spain
| | - Javier Egea
- Instituto de Investigación Sanitaria-Hospital Universitario de la Princesa, Madrid, Spain.,Instituto Teófilo Hernando, Department of Pharmacology and Therapeutics, Medicine Faculty, Autónoma University, Madrid, Spain
| | - Elena Román
- Paediatric Nephrology Department, La Fe Hospital, Valencia, Spain
| | - Pablo Cannata
- Red de Investigación Renal (REDINREN), Madrid, Spain.,Pathology Department, Fundación Instituto de Investigaciones Sanitarias-Fundación Jiménez Díaz, Autónoma University, Madrid, Spain
| | - Rosa Ortega
- Pathology Department, Hospital Universitario Reina Sofia, Córdoba, Spain
| | - Isabel Cortegano
- Immunology Department, Centro Nacional de Microbiología, Instituto de Salud Carlos III (ISCIII), Madrid, Spain
| | - Belén de Andrés
- Immunology Department, Centro Nacional de Microbiología, Instituto de Salud Carlos III (ISCIII), Madrid, Spain
| | - María Luisa Gaspar
- Immunology Department, Centro Nacional de Microbiología, Instituto de Salud Carlos III (ISCIII), Madrid, Spain
| | - Susana Cadenas
- Centro de Biología Molecular 'Severo Ochoa' and Molecular Biology Department, Autónoma University, Madrid, Spain.,Instituto de Investigación Sanitaria La Princesa, Madrid, Spain
| | - Alberto Ortiz
- Renal, Vascular and Diabetes Research Laboratory, Fundación Instituto de Investigación Sanitaria-Fundación Jiménez Díaz, Autónoma University, Madrid, Spain.,Red de Investigación Renal (REDINREN), Madrid, Spain
| | - Jesús Egido
- Renal, Vascular and Diabetes Research Laboratory, Fundación Instituto de Investigación Sanitaria-Fundación Jiménez Díaz, Autónoma University, Madrid, Spain.,Spanish Biomedical Research Centre in Diabetes and Associated Metabolic Disorders (CIBERDEM), Madrid, Spain
| | - Juan Antonio Moreno
- Renal, Vascular and Diabetes Research Laboratory, Fundación Instituto de Investigación Sanitaria-Fundación Jiménez Díaz, Autónoma University, Madrid, Spain
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Liu T, Liu M, Shang P, Jin X, Liu W, Zhang Y, Li X, Ding Y, Li Y, Wen A. Investigation into the underlying molecular mechanisms of hypertensive nephrosclerosis using bioinformatics analyses. Mol Med Rep 2018; 17:4440-4448. [PMID: 29328390 PMCID: PMC5802219 DOI: 10.3892/mmr.2018.8405] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2017] [Accepted: 11/24/2017] [Indexed: 12/11/2022] Open
Abstract
Hypertensive nephrosclerosis (HNS) is a major risk factor for end-stage renal disease. However, the underlying pathogenesis of HNS remains to be fully determined. The gene expression profile of GSE20602, which consists of 14 glomeruli samples from patients with HNS and 4 normal glomeruli control samples, was obtained from the Gene Expression Omnibus database. Gene ontology (GO) and pathway enrichment analyses were performed in order to investigate the functions and pathways of differentially expressed genes (DEGs). Pathway relation and co‑expression networks were constructed in order to identify key genes and signaling pathways involved in HNS. In total, 483 DEGs were identified to be associated with HNS, including 302 upregulated genes and 181 downregulated genes. Furthermore, GO analysis revealed that DEGs were significantly enriched in the small molecule metabolic process. In addition, pathway analysis also revealed that DEGs were predominantly involved in metabolic pathways. The tricarboxylic acid (TCA) cycle was identified as the hub pathway in the pathway relation network, whereas the sorbitol dehydrogenase (SORD) and cubulin (CUBN) genes were revealed to be the hub genes in the co‑expression network. The present study revealed that the SORD, CUBN and albumin genes as well as the TCA cycle and metabolic pathways are involved in the pathogenesis of HNS. The results of the present study may contribute to the determination of the molecular mechanisms underlying HNS, and provide insight into the exploration of novel targets for the diagnosis and treatment of HNS.
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Affiliation(s)
- Tianlong Liu
- Department of Pharmacy, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
| | - Minna Liu
- Department of Nephrology, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
| | - Peijin Shang
- Department of Pharmacy, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
| | - Xin Jin
- Department of Pharmacy, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
| | - Wenxing Liu
- Department of Pharmacy, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
| | - Yikai Zhang
- Department of Pharmacy, General Hospital of Shenyang Military Region, Shenyang, Liaoning 110016, P.R. China
| | - Xinfang Li
- Department of Inorganic Chemistry, School of Pharmacy, Second Military Medical University, Shanghai 200433, P.R. China
| | - Yi Ding
- Department of Pharmacy, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
| | - Yuwen Li
- Department of Pharmacy, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
| | - Aidong Wen
- Department of Pharmacy, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
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Gianesello L, Priante G, Ceol M, Radu CM, Saleem MA, Simioni P, Terrin L, Anglani F, Del Prete D. Albumin uptake in human podocytes: a possible role for the cubilin-amnionless (CUBAM) complex. Sci Rep 2017; 7:13705. [PMID: 29057905 PMCID: PMC5651885 DOI: 10.1038/s41598-017-13789-z] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Accepted: 10/02/2017] [Indexed: 12/23/2022] Open
Abstract
Albumin re-uptake is a receptor-mediated pathway located in renal proximal tubuli. There is increasing evidence of glomerular protein handling by podocytes, but little is known about the mechanism behind this process. In this study, we found that human podocytes in vitro are committed to internalizing albumin through a receptor-mediated mechanism even after exposure to low doses of albumin. We show that these cells express cubilin, megalin, ClC-5, amnionless and Dab2, which are partners in the tubular machinery. Exposing human podocytes to albumin overload prompted an increase in CUBILIN, AMNIONLESS and CLCN5 gene expression. Inhibiting cubilin led to a reduction in albumin uptake, highlighting its importance in this mechanism. We demonstrated that human podocytes are committed to performing endocytosis via a receptor-mediated mechanism even in the presence of low doses of albumin. We also disclosed that protein overload first acts on the expression of the cubilin-amnionless (CUBAM) complex in these cells, then involves the ClC-5 channel, providing the first evidence for a possible role of the CUBAM complex in albumin endocytosis in human podocytes.
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Affiliation(s)
- Lisa Gianesello
- Clinical Nephrology, Department of Medicine - DIMED, University of Padua, 35129, Padua, Italy
| | - Giovanna Priante
- Clinical Nephrology, Department of Medicine - DIMED, University of Padua, 35129, Padua, Italy
| | - Monica Ceol
- Clinical Nephrology, Department of Medicine - DIMED, University of Padua, 35129, Padua, Italy
| | - Claudia M Radu
- Thrombotic and Hemorrhagic Diseases Unit, Department of Medicine - DIMED, University of Padua, 35129, Padua, Italy
| | - Moin A Saleem
- Academic and Children's Renal Unit, Dorothy Hodgkin Building, BS8 1TH, Bristol, United Kingdom
| | - Paolo Simioni
- Thrombotic and Hemorrhagic Diseases Unit, Department of Medicine - DIMED, University of Padua, 35129, Padua, Italy
| | - Liliana Terrin
- Clinical Nephrology, Department of Medicine - DIMED, University of Padua, 35129, Padua, Italy
| | - Franca Anglani
- Clinical Nephrology, Department of Medicine - DIMED, University of Padua, 35129, Padua, Italy
| | - Dorella Del Prete
- Clinical Nephrology, Department of Medicine - DIMED, University of Padua, 35129, Padua, Italy.
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Castrop H, Schießl IM. Novel routes of albumin passage across the glomerular filtration barrier. Acta Physiol (Oxf) 2017; 219:544-553. [PMID: 27452481 DOI: 10.1111/apha.12760] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Revised: 06/13/2016] [Accepted: 07/20/2016] [Indexed: 12/20/2022]
Abstract
Albuminuria is a hallmark of kidney diseases of various aetiologies and an unambiguous symptom of the compromised integrity of the glomerular filtration barrier. Furthermore, there is increasing evidence that albuminuria per se aggravates the development and progression of chronic kidney disease. This review covers new aspects of the movement of large plasma proteins across the glomerular filtration barrier in health and disease. Specifically, this review focuses on the role of endocytosis and transcytosis of albumin by podocytes, which constitutes a new pathway of plasma proteins across the filtration barrier. Thus, we summarize what is known about the mechanisms of albumin endocytosis by podocytes and address the fate of the endocytosed albumin, which is directed to lysosomal degradation or transcellular movement with subsequent vesicular release into the urinary space. We also address the functional consequences of overt albumin endocytosis by podocytes, such as the formation of pro-inflammatory cytokines, which might eventually result in a deterioration of podocyte function. Finally, we consider the diagnostic potential of podocyte-derived albumin-containing vesicles in the urine as an early marker of a compromised glomerular barrier function. In terms of new technical approaches, the review covers how our knowledge of the movement of albumin across the glomerular filtration barrier has expanded by the use of new intravital imaging techniques.
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Affiliation(s)
- H. Castrop
- Institute of Physiology; University of Regensburg; Regensburg Germany
| | - I. M. Schießl
- Institute of Physiology; University of Regensburg; Regensburg Germany
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35
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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: 298] [Impact Index Per Article: 42.6] [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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36
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Skorecki K, Wasser WG. Beyond APOL1: Genetic Inroads into Understanding Population Disparities in Diabetic Kidney Disease. Clin J Am Soc Nephrol 2016; 11:928-931. [PMID: 27197913 PMCID: PMC4891746 DOI: 10.2215/cjn.04680416] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- Karl Skorecki
- Department of Genetics and Developmental Biology, Rappaport Faculty of Medicine and Research Institute, Technion, Haifa, Israel Institute of Technology, Israel
- Department of Nephrology, Rambam Health Care Campus, Haifa, Israel; and
| | - Walter G. Wasser
- Department of Nephrology, Rambam Health Care Campus, Haifa, Israel; and
- Division of Nephrology, Mayanei HaYeshua Medical Center, Bnei Brak, Israel
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37
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Abstract
The function of the kidney, filtering blood and concentrating metabolic waste into urine, takes place in an intricate and functionally elegant structure called the renal glomerulus. Normal glomerular function retains circulating cells and valuable macromolecular components of plasma in blood, resulting in urine with just trace amounts of proteins. Endothelial cells of glomerular capillaries, the podocytes wrapped around them, and the fused extracellular matrix these cells form altogether comprise the glomerular filtration barrier, a dynamic and highly selective filter that sieves on the basis of molecular size and electrical charge. Current understanding of the structural organization and the cellular and molecular basis of renal filtration draws from studies of human glomerular diseases and animal models of glomerular dysfunction.
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Affiliation(s)
- Rizaldy P Scott
- Feinberg School of Medicine, Northwestern University, Chicago, IL 60611
| | - Susan E Quaggin
- Feinberg School of Medicine, Northwestern University, Chicago, IL 60611
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38
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Schießl IM, Hammer A, Kattler V, Gess B, Theilig F, Witzgall R, Castrop H. Intravital Imaging Reveals Angiotensin II-Induced Transcytosis of Albumin by Podocytes. J Am Soc Nephrol 2015; 27:731-44. [PMID: 26116357 DOI: 10.1681/asn.2014111125] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 05/11/2015] [Indexed: 11/03/2022] Open
Abstract
Albuminuria is a hallmark of kidney disease of various etiologies and usually caused by deterioration of glomerular filtration barrier integrity. We recently showed that angiotensin II (Ang II) acutely increases albumin filtration in the healthy kidney. Here, we used intravital microscopy to assess the effects of Ang II on podocyte function in rats. Acute infusion of 30, 60, or 80 ng/kg per minute Ang II enhanced the endocytosis of albumin by activation of the type 1 Ang II receptor and resulted in an average (±SEM) of 3.7±2.2, 72.3±18.6 (P<0.001), and 239.4±34.6 µm(3) (P<0.001) albumin-containing vesicles per glomerulus, respectively, compared with none at baseline or 10 ng/kg per minute Ang II. Immunostaining of Ang II-infused kidneys confirmed the presence of albumin-containing vesicles, which colocalized with megalin, in podocin-positive cells. Furthermore, podocyte endocytosis of albumin was markedly reduced in the presence of gentamicin, a competitive inhibitor of megalin-dependent endocytosis. Ang II infusion increased the concentration of albumin in the subpodocyte space, a potential source for endocytic protein uptake, and gentamicin further increased this concentration. Some endocytic vesicles were acidified and colocalized with LysoTracker. Most vesicles migrated from the capillary to the apical aspect of the podocyte and were eventually released into the urinary space. This transcytosis accounted for approximately 10% of total albumin filtration. In summary, the transcellular transport of proteins across the podocyte constitutes a new pathway of glomerular protein filtration. Ang II enhances the endocytosis and transcytosis of plasma albumin by podocytes, which may eventually impair podocyte function.
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Affiliation(s)
| | | | | | | | - Franziska Theilig
- Department of Medicine, University of Fribourg, Fribourg, Switzerland
| | - Ralph Witzgall
- Molecular and Cellular Anatomy, University of Regensburg, Regensburg, Germany; and
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39
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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: 144] [Impact Index Per Article: 16.0] [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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40
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Jensen LL, Andersen RK, Hager H, Madsen M. Lack of megalin expression in adult human terminal ileum suggests megalin-independent cubilin/amnionless activity during vitamin B12 absorption. Physiol Rep 2014; 2:2/7/e12086. [PMID: 25052491 PMCID: PMC4187553 DOI: 10.14814/phy2.12086] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Cubilin plays an essential role in terminal ileum and renal proximal tubules during absorption of vitamin B12 and ligands from the glomerular ultrafiltrate. Cubilin is coexpressed with amnionless, and cubilin and amnionless are mutually dependent on each other for correct processing to the plasma membrane upon synthesis. Patients with defects in either protein suffer from vitamin B12‐malabsorption and in some cases proteinuria. Cubilin lacks a transmembrane region and signals for endocytosis and is dependent on a transmembrane coreceptor during internalization. Amnionless has been shown to be able to mediate internalization of cubilin in a cell‐based model system. Cubilin has additionally been suggested to function together with megalin, and a recent study of megalin‐deficient patients indicates that uptake of cubilin ligands in the kidney is critically dependent on megalin. To further investigate the potential role of amnionless and megalin in relation to cubilin function in terminal ileum and vitamin B12 uptake, we initiated a study of CUBN/cubilin, AMN/amnionless, and LRP2/megalin expression in adult human terminal ileum. Our study is the first to reveal the expression pattern of cubilin, amnionless, and megalin in adult human terminal ileum, where cubilin and amnionless localize to the epithelial cells. Surprisingly, we did not detect any megalin protein in adult terminal ileum and consistently, only extremely low amounts of LRP2 mRNA. Our data therefore advocate that cubilin and amnionless act independently of megalin in adult terminal ileum and that the cubilin‐megalin interdependency accordingly should be considered as tissue and ligand specific. e12086 Studies of human terminal ileum samples demonstrate lack of LRP2/megalin expression in adult terminal ileum and point to a megalin‐independent cubilin‐amnionless‐driven uptake mechanism for vitamin B12.
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Affiliation(s)
- Louise L Jensen
- Department of Biomedicine, University of Aarhus, 8000 Aarhus C., Denmark
| | - Rikke K Andersen
- Department of Biomedicine, University of Aarhus, 8000 Aarhus C., Denmark
| | - Henrik Hager
- Department of Pathology, Aarhus University Hospital, 8000 Aarhus C., Denmark
| | - Mette Madsen
- Department of Biomedicine, University of Aarhus, 8000 Aarhus C., Denmark
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41
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De S, Kuwahara S, Saito A. The endocytic receptor megalin and its associated proteins in proximal tubule epithelial cells. MEMBRANES 2014; 4:333-55. [PMID: 25019425 PMCID: PMC4194038 DOI: 10.3390/membranes4030333] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/31/2014] [Revised: 06/23/2014] [Accepted: 07/01/2014] [Indexed: 02/08/2023]
Abstract
Receptor-mediated endocytosis in renal proximal tubule epithelial cells (PTECs) is important for the reabsorption and metabolization of proteins and other substances, including carrier-bound vitamins and trace elements, in glomerular filtrates. Impairment of this endocytic process results in the loss of such substances and development of proteinuria, which is an important clinical indicator of kidney diseases and is also a risk marker for cardiovascular disease. Megalin, a member of the low-density lipoprotein receptor gene family, is a multiligand receptor expressed in the apical membrane of PTECs and plays a central role in the endocytic process. Megalin interacts with various intracellular adaptor proteins for intracellular trafficking and cooperatively functions with other membrane molecules, including the cubilin-amnionless complex. Evidence suggests that megalin and the cubilin-amnionless complex are involved in the uptake of toxic substances into PTECs, which leads to the development of kidney disease. Studies of megalin and its associated molecules will be useful for future development of novel strategies for the diagnosis and treatment of kidney diseases.
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Affiliation(s)
- Shankhajit De
- Division of Clinical Nephrology and Rheumatology, Niigata University Graduate School of Medical and Dental Sciences, 1-757 Asahimachi-dori, Chuo-ku, Niigata 951-8510, Japan.
| | - Shoji Kuwahara
- Department of Applied Molecular Medicine, Niigata University Graduate School of Medical and Dental Sciences, 1-757 Asahimachi-dori, Chuo-ku, Niigata 951-8510, Japan.
| | - Akihiko Saito
- Department of Applied Molecular Medicine, Niigata University Graduate School of Medical and Dental Sciences, 1-757 Asahimachi-dori, Chuo-ku, Niigata 951-8510, Japan.
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42
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Ma L, Shelness GS, Snipes JA, Murea M, Antinozzi PA, Cheng D, Saleem MA, Satchell SC, Banas B, Mathieson PW, Kretzler M, Hemal AK, Rudel LL, Petrovic S, Weckerle A, Pollak MR, Ross MD, Parks JS, Freedman BI. Localization of APOL1 protein and mRNA in the human kidney: nondiseased tissue, primary cells, and immortalized cell lines. J Am Soc Nephrol 2014; 26:339-48. [PMID: 25012173 DOI: 10.1681/asn.2013091017] [Citation(s) in RCA: 107] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Although APOL1 gene variants are associated with nephropathy in African Americans, little is known about APOL1 protein synthesis, uptake, and localization in kidney cells. To address these questions, we examined APOL1 protein and mRNA localization in human kidney and human kidney-derived cell lines. Indirect immunofluorescence microscopy performed on nondiseased nephrectomy cryosections from persons with normal kidney function revealed that APOL1 protein was markedly enriched in podocytes (colocalized with synaptopodin and Wilms' tumor suppressor) and present in lower abundance in renal tubule cells. Fluorescence in situ hybridization detected APOL1 mRNA in glomeruli (podocytes and endothelial cells) and tubules, consistent with endogenous synthesis in these cell types. When these analyses were extended to renal-derived cell lines, quantitative RT-PCR did not detect APOL1 mRNA in human mesangial cells; however, abundant levels of APOL1 mRNA were observed in proximal tubule cells and glomerular endothelial cells, with lower expression in podocytes. Western blot analysis revealed corresponding levels of APOL1 protein in these cell lines. To explain the apparent discrepancy between the marked abundance of APOL1 protein in kidney podocytes observed in cryosections versus the lesser abundance in podocyte cell lines, we explored APOL1 cellular uptake. APOL1 protein was taken up readily by human podocytes in vitro but was not taken up efficiently by mesangial cells, glomerular endothelial cells, or proximal tubule cells. We hypothesize that the higher levels of APOL1 protein in human cryosectioned podocytes may reflect both endogenous protein synthesis and APOL1 uptake from the circulation or glomerular filtrate.
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Affiliation(s)
| | | | | | | | - Peter A Antinozzi
- Biochemistry, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | | | - Moin A Saleem
- Children's Renal Unit, Bristol Royal Hospital for Children, University of Bristol, Bristol, United Kingdom
| | - Simon C Satchell
- Learning and Research Southmead Hospital Bristol, University of Bristol, Bristol, United Kingdom
| | - Bernhard Banas
- Internal Medicine II-Nephrology/Transplantation, University Medical Center, Regensburg, Germany
| | - Peter W Mathieson
- Children's Renal Unit, Bristol Royal Hospital for Children, University of Bristol, Bristol, United Kingdom
| | - Matthias Kretzler
- Department of Internal Medicine-Nephrology, University of Michigan at Ann Arbor Medical School, Ann Arbor, Michigan
| | | | | | - Snezana Petrovic
- Internal Medicine-Nephrology, Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina
| | | | - Martin R Pollak
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts; and
| | - Michael D Ross
- Renal Division, Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts
| | - John S Parks
- Pathology-Lipid Sciences, and Biochemistry, Wake Forest School of Medicine, Winston-Salem, North Carolina
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43
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Pawluczyk IZA, Pervez A, Ghaderi Najafabadi M, Saleem MA, Topham PS. The effect of albumin on podocytes: the role of the fatty acid moiety and the potential role of CD36 scavenger receptor. Exp Cell Res 2014; 326:251-8. [PMID: 24815572 DOI: 10.1016/j.yexcr.2014.04.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Revised: 04/07/2014] [Accepted: 04/21/2014] [Indexed: 10/25/2022]
Abstract
Evidence is emerging that podocytes are able to endocytose proteins such as albumin using kinetics consistent with a receptor-mediated process. To date the role of the fatty acid moiety on albumin uptake kinetics has not been delineated and the receptor responsible for uptake is yet to be identified. Albumin uptake studies were carried out on cultured human podocytes exposed to FITC-labelled human serum albumin either carrying fatty acids (HSA+FA) or depleted of them (HSA-FA). Receptor-mediated endocytosis of FITC-HSA+FA over 60 min was 5 times greater than that of FITC-HSA-FA. 24h exposure of podocytes to albumin up-regulated nephrin expression and induced the activation of caspase-3. These effects were more pronounced in response to HSA-FA. Individually, anti-CD36 antibodies had no effect upon endocytosis of FITC-HSA. However, a cocktail of 2 antibodies reduced uptake by nearly 50%. Albumin endocytosis was enhanced in the presence of the CD36 specific inhibitor sulfo-N-succinimidyl oleate (SSO) while knock-down of CD36 using CD36siRNA had no effect on uptake. These data suggest that receptor-mediated endocytosis of albumin by podocytes is regulated by the fatty acid moiety, although, some of the detrimental effects are induced independently of it. CD36 does not play a direct role in the uptake of albumin.
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Affiliation(s)
- I Z A Pawluczyk
- Department of Infection, Immunity and inflammation, University of Leicester, Leicester, UK; John Walls Renal Unit, Leicester General Hospital Leicester, UK.
| | - A Pervez
- Department of Infection, Immunity and inflammation, University of Leicester, Leicester, UK
| | - M Ghaderi Najafabadi
- Department of Infection, Immunity and inflammation, University of Leicester, Leicester, UK
| | - M A Saleem
- Academic and Children׳s Renal Unit, University of Bristol, Southmead Hospital, Bristol, UK
| | - P S Topham
- Department of Infection, Immunity and inflammation, University of Leicester, Leicester, UK; John Walls Renal Unit, Leicester General Hospital Leicester, UK
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44
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Wilkinson R, Wang X, Kassianos AJ, Zuryn S, Roper KE, Osborne A, Sampangi S, Francis L, Raghunath V, Healy H. Laser capture microdissection and multiplex-tandem PCR analysis of proximal tubular epithelial cell signaling in human kidney disease. PLoS One 2014; 9:e87345. [PMID: 24475278 PMCID: PMC3903679 DOI: 10.1371/journal.pone.0087345] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2013] [Accepted: 12/19/2013] [Indexed: 02/06/2023] Open
Abstract
Interstitial fibrosis, a histological process common to many kidney diseases, is the precursor state to end stage kidney disease, a devastating and costly outcome for the patient and the health system. Fibrosis is historically associated with chronic kidney disease (CKD) but emerging evidence is now linking many forms of acute kidney disease (AKD) with the development of CKD. Indeed, we and others have observed at least some degree of fibrosis in up to 50% of clinically defined cases of AKD. Epithelial cells of the proximal tubule (PTEC) are central in the development of kidney interstitial fibrosis. We combine the novel techniques of laser capture microdissection and multiplex-tandem PCR to identify and quantitate "real time" gene transcription profiles of purified PTEC isolated from human kidney biopsies that describe signaling pathways associated with this pathological fibrotic process. Our results: (i) confirm previous in-vitro and animal model studies; kidney injury molecule-1 is up-regulated in patients with acute tubular injury, inflammation, neutrophil infiltration and a range of chronic disease diagnoses, (ii) provide data to inform treatment; complement component 3 expression correlates with inflammation and acute tubular injury, (iii) identify potential new biomarkers; proline 4-hydroxylase transcription is down-regulated and vimentin is up-regulated across kidney diseases, (iv) describe previously unrecognized feedback mechanisms within PTEC; Smad-3 is down-regulated in many kidney diseases suggesting a possible negative feedback loop for TGF-β in the disease state, whilst tight junction protein-1 is up-regulated in many kidney diseases, suggesting feedback interactions with vimentin expression. These data demonstrate that the combined techniques of laser capture microdissection and multiplex-tandem PCR have the power to study molecular signaling within single cell populations derived from clinically sourced tissue.
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Affiliation(s)
- Ray Wilkinson
- Conjoint Kidney Research Laboratory, Pathology Queensland, Brisbane, Queensland, Australia
- Department of Renal Medicine, Royal Brisbane and Women's Hospital, Brisbane, Queensland, Australia
- Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia
- Medical School, University of Queensland, Brisbane, Queensland, Australia
| | - Xiangju Wang
- Conjoint Kidney Research Laboratory, Pathology Queensland, Brisbane, Queensland, Australia
- Department of Renal Medicine, Royal Brisbane and Women's Hospital, Brisbane, Queensland, Australia
| | - Andrew J. Kassianos
- Conjoint Kidney Research Laboratory, Pathology Queensland, Brisbane, Queensland, Australia
- Department of Renal Medicine, Royal Brisbane and Women's Hospital, Brisbane, Queensland, Australia
| | - Steven Zuryn
- Conjoint Kidney Research Laboratory, Pathology Queensland, Brisbane, Queensland, Australia
- Department of Renal Medicine, Royal Brisbane and Women's Hospital, Brisbane, Queensland, Australia
| | - Kathrein E. Roper
- Conjoint Kidney Research Laboratory, Pathology Queensland, Brisbane, Queensland, Australia
- Department of Renal Medicine, Royal Brisbane and Women's Hospital, Brisbane, Queensland, Australia
| | - Andrew Osborne
- Conjoint Kidney Research Laboratory, Pathology Queensland, Brisbane, Queensland, Australia
- Department of Renal Medicine, Royal Brisbane and Women's Hospital, Brisbane, Queensland, Australia
| | - Sandeep Sampangi
- Conjoint Kidney Research Laboratory, Pathology Queensland, Brisbane, Queensland, Australia
- Department of Renal Medicine, Royal Brisbane and Women's Hospital, Brisbane, Queensland, Australia
| | - Leo Francis
- Pathology Queensland, Brisbane, Queensland, Australia
| | - Vishwas Raghunath
- Department of Renal Medicine, Royal Brisbane and Women's Hospital, Brisbane, Queensland, Australia
| | - Helen Healy
- Conjoint Kidney Research Laboratory, Pathology Queensland, Brisbane, Queensland, Australia
- Department of Renal Medicine, Royal Brisbane and Women's Hospital, Brisbane, Queensland, Australia
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McMahon GM, O'Seaghdha CM, Hwang SJ, Meigs JB, Fox CS. The association of a single-nucleotide polymorphism in CUBN and the risk of albuminuria and cardiovascular disease. Nephrol Dial Transplant 2013; 29:342-7. [PMID: 24052458 DOI: 10.1093/ndt/gft386] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND Albuminuria is an important risk factor for cardiovascular disease (CVD). We have previously identified a missense single-nucleotide polymorphism (rs1801239) in the CUBN gene that is associated with albuminuria. Whether albuminuria is associated with CVD in the presence of the CUBN mutation is unknown. METHODS We analyzed participants from the Framingham Heart Study (n=6399, mean age 47 years, 53.4% women) who underwent genotyping of rs1801239. Cox proportional hazards models were used to test the association between microalbuminuria [UACR≥17 mg/g (men) and ≥25 mg/g (women)] and incident CVD stratified by the presence or absence of the CUBN risk allele. We tested whether the association between microalbuminuria and CVD was altered by the presence of the risk allele with interaction testing. RESULTS Overall, 21.1% of participants carried the risk allele. As expected, carriers of the risk (C) allele had a higher prevalence of microalbuminuria (10.7 versus 8.9%, P=0.04). During a mean follow-up of 10.4 years, 5.6% (n=346) of participants experienced a CVD event. Microalbuminuria was associated with an increased risk of CVD [hazards ratio (HR) 1.46, 95% confidence interval (CI) 1.14-1.88]. When stratified by risk allele carrier status, the HR for CVD was 1.95 (95% CI 1.15-3.29) among those with compared to 1.33 (95% CI 1.00-1.76) among those without the risk allele. There was no interaction between microalbuminuria and rs1801239 on CVD (Pinteraction=0.49). CONCLUSIONS MA is associated with CVD irrespective of the presence of the CUBN risk allele. These results challenge the concept that albuminuria in the setting of this mutation is benign.
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Affiliation(s)
- Gearoid M McMahon
- National Heart, Lung and Blood Institute's Framingham Heart Study and the Center for Population Studies, Framingham, MA, USA
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Glomerular Endothelial Surface Layer Acts as a Barrier against Albumin Filtration. THE AMERICAN JOURNAL OF PATHOLOGY 2013; 182:1532-40. [DOI: 10.1016/j.ajpath.2013.01.049] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2012] [Revised: 01/11/2013] [Accepted: 01/15/2013] [Indexed: 12/19/2022]
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Okamura K, Dummer P, Kopp J, Qiu L, Levi M, Faubel S, Blaine J. Endocytosis of albumin by podocytes elicits an inflammatory response and induces apoptotic cell death. PLoS One 2013; 8:e54817. [PMID: 23382978 PMCID: PMC3557279 DOI: 10.1371/journal.pone.0054817] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Accepted: 12/17/2012] [Indexed: 12/11/2022] Open
Abstract
The presence of albuminuria is strongly associated with progression of chronic kidney disease. While albuminuria has been shown to injure renal proximal tubular cells, the effects of albumin on podocytes have been less well studied. We have addressed the hypothesis that exposure of podocytes to albumin initiates an injury response. We studied transformed human-urine derived podocytes-like epithelial cells (HUPECS, or podocytes). Upon differentiation, these cells retain certain characteristics of differentiated podocytes, including expression of synaptopodin, CD2AP, and nestin. We exposed podocytes to recombinant human albumin, which lacks lipids and proteins that bind serum albumin; this reagent allowed a direct examination of the effects of albumin. Podocytes endocytosed fluoresceinated albumin and this process was inhibited at 4°C, suggesting an energy-dependent process. Exposure to albumin at concentrations of 5 and 10 mg/ml was associated with increased cell death in a dose-dependent manner. The mechanism of cell death may involve apoptosis, as caspase 3/7 were activated and the pan-caspase inhibitor z-VAD reduced cell death. Albumin exposure also increased nuclear factor (NF)-κB activation and increased transcription and release of interleukin (IL-) 1β, tumor necrosis factor (TNF), and IL-6. We extended these findings to an in vivo model. Glomeruli isolated from mice with nephrotic syndrome also had increased expression of IL-1β and TNF RNA. These data suggest that while podocyte injury begets albuminuria, albumin in the glomerular ultrafiltrate may also beget podocyte injury. Thus, an additional mechanism by which anti-proteinuric therapies are beneficial in the treatment of glomerular diseases may be a reduction in injury to the podocyte by albumin.
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Affiliation(s)
- Kayo Okamura
- Department of Medicine, University of Colorado Denver, Aurora, Colorado, United States of America
| | - Patrick Dummer
- Kidney Disease Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Jeffrey Kopp
- Kidney Disease Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Liru Qiu
- Department of Medicine, University of Colorado Denver, Aurora, Colorado, United States of America
| | - Moshe Levi
- Department of Medicine, University of Colorado Denver, Aurora, Colorado, United States of America
| | - Sarah Faubel
- Department of Medicine, University of Colorado Denver, Aurora, Colorado, United States of America
| | - Judith Blaine
- Department of Medicine, University of Colorado Denver, Aurora, Colorado, United States of America
- * E-mail:
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Christensen EI, Nielsen R, Birn H. From bowel to kidneys: the role of cubilin in physiology and disease. Nephrol Dial Transplant 2013; 28:274-81. [DOI: 10.1093/ndt/gfs565] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Christensen EI, Birn H, Storm T, Weyer K, Nielsen R. Endocytic Receptors in the Renal Proximal Tubule. Physiology (Bethesda) 2012; 27:223-36. [DOI: 10.1152/physiol.00022.2012] [Citation(s) in RCA: 170] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Protein reabsorption is a predominant feature of the renal proximal tubule. Animal studies show that the ability to rescue plasma proteins relies on the endocytic receptors megalin and cubilin. Recently, studies of patients with syndromes caused by dysfunctional receptors have supported the importance of these for protein clearance of human ultrafiltrate. This review focuses on the molecular biology and physiology of the receptors and their involvement in renal pathological conditions.
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Affiliation(s)
- Erik I. Christensen
- Department of Biomedicine, Faculty of Health Sciences, Aarhus University, Aarhus, Denmark
| | - Henrik Birn
- Department of Biomedicine, Faculty of Health Sciences, Aarhus University, Aarhus, Denmark
| | - Tina Storm
- Department of Biomedicine, Faculty of Health Sciences, Aarhus University, Aarhus, Denmark
| | - Kathrin Weyer
- Department of Biomedicine, Faculty of Health Sciences, Aarhus University, Aarhus, Denmark
| | - Rikke Nielsen
- Department of Biomedicine, Faculty of Health Sciences, Aarhus University, Aarhus, Denmark
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