Circulating urokinase receptor as a cause of focal segmental glomerulosclerosis
TL;DR: It is reported that serum soluble urokinase receptor (suPAR) is elevated in two-thirds of subjects with primary FSGS, but not in people with other glomerular diseases, and that a higher concentration of suPAR before transplantation underlies an increased risk for recurrence of FSGS after transplantation.
Abstract: Focal segmental glomerulosclerosis (FSGS) is a cause of proteinuric kidney disease, compromising both native and transplanted kidneys. Treatment is limited because of a complex pathogenesis, including unknown serum factors. Here we report that serum soluble urokinase receptor (suPAR) is elevated in two-thirds of subjects with primary FSGS, but not in people with other glomerular diseases. We further find that a higher concentration of suPAR before transplantation underlies an increased risk for recurrence of FSGS after transplantation. Using three mouse models, we explore the effects of suPAR on kidney function and morphology. We show that circulating suPAR activates podocyte β(3) integrin in both native and grafted kidneys, causing foot process effacement, proteinuria and FSGS-like glomerulopathy. Our findings suggest that the renal disease only develops when suPAR sufficiently activates podocyte β(3) integrin. Thus, the disease can be abrogated by lowering serum suPAR concentrations through plasmapheresis, or by interfering with the suPAR-β(3) integrin interaction through antibodies and small molecules targeting either uPAR or β(3) integrin. Our study identifies serum suPAR as a circulating factor that may cause FSGS.
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TL;DR: Current approaches to diagnosis and management ofocal segmental glomerulosclerosis are considered, which is characterized by progressive glomerular scarring, in children and adults.
Abstract: Focal segmental glomerulosclerosis, which is characterized by progressive glomerular scarring, accounts for about 20% of cases of the nephrotic syndrome in children and 40% in adults. This review considers current approaches to diagnosis and management of the disease.
645 citations
TL;DR: This Sixth Edition of the ASFA Special Issue has further improved the process of using evidence‐based medicine in the recommendations by consistently applying the category and GRADE system definitions, but eliminating the “level of evidence” criteria.
Abstract: The American Society for Apheresis (ASFA) JCA Special Issue Writing Committee is charged with reviewing, updating and categorizating indications for therapeutic apheresis. Beginning with the 2007 ASFA Special Issue (Fourth Edition), the committee has incorporated systematic review and evidence‐based approach in the grading and categorization of indications. This Sixth Edition of the ASFA Special Issue has further improved the process of using evidence‐based medicine in the recommendations by consistently applying the category and GRADE system definitions, but eliminating the “level of evidence” criteria (from the University HealthCare Consortium) utilized in prior editions given redundancy between GRADE and University HealthCare Consortium systems. The general layout and concept of a fact sheet that was utilized in the Fourth and Fifth Editions, has been largely maintained in this edition. Each fact sheet succinctly summarizes the evidence for the use of therapeutic apheresis in a specific disease entity. This article consists of 78 fact sheets (increased from 2010) for therapeutic indications in ASFA categories I through IV, with many diseases categorized having multiple clinical presentations/situations which are individually graded and categorized. J. Clin. Apheresis 28:145–284, 2013. © 2013 Wiley Periodicals, Inc.
590 citations
TL;DR: A membrane biologist's view of the podocyte is taken, examining the many membrane receptors, channels, and other signaling molecules that have been implicated in podocyte biology and emphasizing that this approach may be fruitful in understanding the podocytes and its unique properties.
Abstract: As an integral member of the filtration barrier in the kidney glomerulus, the podocyte is in a unique geographical position: It is exposed to chemical signals from the urinary space (Bowman's capsule), it receives and transmits chemical and mechanical signals to/from the glomerular basement membrane upon which it elaborates, and it receives chemical and mechanical signals from the vascular space with which it also communicates. As with every cell, the ability of the podocyte to receive signals from the surrounding environment and to translate them to the intracellular milieu is dependent largely on molecules residing on the cell membrane. These molecules are the first-line soldiers in the ongoing battle to sense the environment, to respond to friendly signals, and to defend against injurious foes. In this review, we take a membrane biologist's view of the podocyte, examining the many membrane receptors, channels, and other signaling molecules that have been implicated in podocyte biology. Although we atte...
439 citations
TL;DR: Important outstanding issues remain, including the identity of the plasma factor believed to be responsible for primary FSGS, the value of routine implementation of genetic testing, and the identification of more effective and less toxic therapeutic interventions for FSGS.
Abstract: Focal segmental glomerulosclerosis (FSGS) is a leading cause of kidney disease worldwide. The presumed etiology of primary FSGS is a plasma factor with responsiveness to immunosuppressive therapy and a risk of recurrence after kidney transplant–important disease characteristics. In contrast, adaptive FSGS is associated with excessive nephron workload due to increased body size, reduced nephron capacity, or single glomerular hyperfiltration associated with certain diseases. Additional etiologies are now recognized as drivers of FSGS: high-penetrance genetic FSGS due to mutations in one of nearly 40 genes, virus-associated FSGS, and medication-associated FSGS. Emerging data support the identification of a sixth category: APOL1 risk allele–associated FSGS in individuals with sub-Saharan ancestry. The classification of a particular patient with FSGS relies on integration of findings from clinical history, laboratory testing, kidney biopsy, and in some patients, genetic testing. The kidney biopsy can be helpful, with clues provided by features on light microscopy (e.g., glomerular size, histologic variant of FSGS, microcystic tubular changes, and tubular hypertrophy), immunofluorescence (e.g., to rule out other primary glomerulopathies), and electron microscopy (e.g., extent of podocyte foot process effacement, podocyte microvillous transformation, and tubuloreticular inclusions). A complete assessment of renal histology is important for establishing the parenchymal setting of segmental glomerulosclerosis, distinguishing FSGS associated with one of many other glomerular diseases from the clinical-pathologic syndrome of FSGS. Genetic testing is beneficial in particular clinical settings. Identifying the etiology of FSGS guides selection of therapy and provides prognostic insight. Much progress has been made in our understanding of FSGS, but important outstanding issues remain, including the identity of the plasma factor believed to be responsible for primary FSGS, the value of routine implementation of genetic testing, and the identification of more effective and less toxic therapeutic interventions for FSGS.
294 citations
TL;DR: An elevated level of suPAR was independently associated with incident chronic kidney disease and an accelerated decline in the eGFR in the groups studied.
Abstract: BackgroundRelatively high plasma levels of soluble urokinase-type plasminogen activator receptor (suPAR) have been associated with focal segmental glomerulosclerosis and poor clinical outcomes in patients with various conditions. It is unknown whether elevated suPAR levels in patients with normal kidney function are associated with future decline in the estimated glomerular filtration rate (eGFR) and with incident chronic kidney disease. MethodsWe measured plasma suPAR levels in 3683 persons enrolled in the Emory Cardiovascular Biobank (mean age, 63 years; 65% men; median suPAR level, 3040 pg per milliliter) and determined renal function at enrollment and at subsequent visits in 2292 persons. The relationship between suPAR levels and the eGFR at baseline, the change in the eGFR over time, and the development of chronic kidney disease (eGFR <60 ml per minute per 1.73 m2 of body-surface area) were analyzed with the use of linear mixed models and Cox regression after adjustment for demographic and clinical v...
294 citations
References
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TL;DR: A majority of patients with idiopathic membranous nephropathy have antibodies against a conformation-dependent epitope in PLA(2)R, indicating that PLA( 2)R is a major antigen in this disease.
Abstract: BACKGROUND Idiopathic membranous nephropathy, a common form of the nephrotic syndrome, is an antibody-mediated autoimmune glomerular disease. Serologic diagnosis has been elusive because the target antigen is unknown. METHODS We performed Western blotting of protein extracts from normal human glomeruli with serum samples from patients with idiopathic or secondary membranous nephropathy or other proteinuric or autoimmune diseases and from normal controls. We used mass spectrometry to analyze the reactive protein bands and confirmed the identity and location of the target antigen with a monospecific antibody. RESULTS Serum samples from 26 of 37 patients (70%) with idiopathic but not secondary membranous nephropathy specifically identified a 185-kD glycoprotein in nonreduced glomerular extract. Mass spectrometry of the reactive protein band detected the M-type phospholipase A 2 receptor (PLA 2 R). Reactive serum specimens recognized recombinant PLA 2 R and bound the same 185-kD glomerular protein as did the monospecific anti-PLA 2 R antibody. Anti-PLA 2 R autoantibodies in serum samples from patients with membranous nephropathy were mainly IgG4, the predominant immunoglobulin subclass in glomerular deposits. PLA 2 R was expressed in podocytes in normal human glomeruli and colocalized with IgG4 in immune deposits in glomeruli of patients with membranous nephropathy. IgG eluted from such deposits in patients with idiopathic membranous nephropathy, but not in those with lupus membranous or IgA nephropathy, recognized PLA 2 R. CONCLUSIONS A majority of patients with idiopathic membranous nephropathy have antibodies against a conformation-dependent epitope in PLA 2 R. PLA 2 R is present in normal podocytes and in immune deposits in patients with idiopathic membranous nephropathy, indicating that PLA 2 R is a major antigen in this disease.
1,643 citations
TL;DR: The urokinase receptor uPAR was originally thought to assist the directional invasion of migrating cells, but it is now becoming increasingly evident that this proteinase receptor elicits a plethora of cellular responses that include cellular adhesion, differentiation, proliferation and migration in a non-proteolytic fashion.
Abstract: The plasminogen system has been implicated in clot lysis, wound healing, tissue regeneration, cancer and many other processes that affect health and disease. The urokinase receptor uPAR was originally thought to assist the directional invasion of migrating cells, but it is now becoming increasingly evident that this proteinase receptor elicits a plethora of cellular responses that include cellular adhesion, differentiation, proliferation and migration in a non-proteolytic fashion.
1,181 citations
TL;DR: The development of this conditionally immortalized human podocyte cell line provides a new tool in the study of podocyte biology, which will enable accurate assessment of the behavior of these complex cells in health and disease.
Abstract: Recent molecular insights have established the podocyte as a key component of the glomerular filtration barrier, and hence an important common pathway in proteinuric diseases. A conditionally immortalized human podocyte cell line has been developed by transfection with the temperature-sensitive SV40-T gene. These cells proliferate at the "permissive" temperature (33 degrees C). After transfer to the "nonpermissive" temperature (37 degrees C), they entered growth arrest and expressed markers of differentiated in vivo podocytes, including the novel podocyte proteins, nephrin, podocin, CD2AP, and synaptopodin, and known molecules of the slit diaphragm ZO-1, alpha-, beta-, and gamma-catenin and P-cadherin. The differentiation was accompanied by a growth arrest and the upregulation of cyclin-dependent kinase inhibitors, p27 and p57, as well as cyclin D(1), whereas cyclin A was downregulated. These data are consistent with cell cycle protein expression during podocyte maturation in vivo. In conclusion, the development of this cell line provides a new tool in the study of podocyte biology, which will enable accurate assessment of the behavior of these complex cells in health and disease.
987 citations
15 Nov 2010
904 citations
TL;DR: Coordination of extracellular matrix (ECM) proteolysis and cell signalling by uPAR underlies its important function in cell migration, proliferation and survival and makes it an attractive therapeutic target in cancer and inflammatory diseases.
Abstract: Urokinase-type plasminogen activator receptor (uPAR) expression is elevated during inflammation and tissue remodelling and in many human cancers, in which it frequently indicates poor prognosis. uPAR regulates proteolysis by binding the extracellular protease urokinase-type plasminogen activator (uPA; also known as urokinase) and also activates many intracellular signalling pathways. Coordination of extracellular matrix (ECM) proteolysis and cell signalling by uPAR underlies its important function in cell migration, proliferation and survival and makes it an attractive therapeutic target in cancer and inflammatory diseases. uPAR lacks transmembrane and intracellular domains and so requires transmembrane co-receptors for signalling. Integrins are essential uPAR signalling co-receptors and a second uPAR ligand, the ECM protein vitronectin, is also crucial for this process.
808 citations