101
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Zhang B, Shi W, Ma J, Sloan A, Faul C, Wei C, Reiser J, Yang Y, Liu S, Wang W. The calcineurin-NFAT pathway allows for urokinase receptor-mediated beta3 integrin signaling to cause podocyte injury. J Mol Med (Berl) 2012; 90:1407-20. [PMID: 23015147 DOI: 10.1007/s00109-012-0960-6] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Revised: 09/09/2012] [Accepted: 09/14/2012] [Indexed: 11/26/2022]
Abstract
Circulating and podocyte-bound urokinase receptor (uPAR) is a mediator of podocyte injury, proteinuria, and focal segmental glomerulosclerosis (FSGS) allowing pathological activation of the uPAR-β3 integrin signaling axis. Clinically, calcineurin inhibitors (e.g., cyclosporine A, CsA) are known to suppress T cells, yet are also being used to reduce proteinuria in FSGS, suggesting the possibility of signal cross talk between uPAR and calcineurin. Calcineurin is known to facilitate the nuclear translocation of the nuclear factor of activated T cells (NFAT). Accordingly, in vivo conditional NFATc1 activation in podocytes leads to proteinuria in mice, yet the downstream targets of NFAT remain unclear. Here, we show that inducible podocyte-specific expression of constitutively active NFATc1 increased podocyte uPAR expression by binding to the Plaur gene promoter (encoding uPAR) in chromatin immunoprecipitation assays. Pathological uPAR signals in podocytes are independent of T cells and affect cell motility via activation, but not expression, changes of the β3 integrin and can be blocked by CsA, NFAT-siRNA, or the cell-permeable NFAT inhibitor (11R-VIVIT) using rodent models of glomerular disease (LPS; 5/6 nephrectomized rats). Taken together, these findings identify podocyte uPAR as a downstream target of NFAT and provide further insights into the pathogenesis of FSGS.
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Affiliation(s)
- Bin Zhang
- Department of Nephrology, Guangdong General Hospital, Guangdong Academy of Medical Sciences, 106 Zhongshan No. 2 Road, Guangzhou 510080, China
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102
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Cheng XW, Shi GP, Kuzuya M, Sasaki T, Okumura K, Murohara T. Role for cysteine protease cathepsins in heart disease: focus on biology and mechanisms with clinical implication. Circulation 2012; 125:1551-62. [PMID: 22451605 DOI: 10.1161/circulationaha.111.066712] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Xian Wu Cheng
- Department of Cardiology, Nagoya University Graduate School of Medicine, 65 Tsuruma-cho, Nagoya, Japan.
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103
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Wasik AA, Polianskyte-Prause Z, Dong MQ, Shaw AS, Yates JR, Farquhar MG, Lehtonen S. Septin 7 forms a complex with CD2AP and nephrin and regulates glucose transporter trafficking. Mol Biol Cell 2012; 23:3370-9. [PMID: 22809625 PMCID: PMC3431928 DOI: 10.1091/mbc.e11-12-1010] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Podocytes are insulin-sensitive and take up glucose in response to insulin. This requires nephrin, which interacts with vesicle-associated membrane protein 2 (VAMP2) on GLUT4 storage vesicles (GSVs) and facilitates their fusion with the plasma membrane. In this paper, we show that the filament-forming GTPase septin 7 is expressed in podocytes and associates with CD2-associated protein (CD2AP) and nephrin, both essential for glomerular ultrafiltration. In addition, septin 7 coimmunoprecipitates with VAMP2. Subcellular fractionation of cultured podocytes revealed that septin 7 is found in both cytoplasmic and membrane fractions, and immunofluorescence microscopy showed that septin 7 is expressed in a filamentous pattern and is also found on vesicles and the plasma membrane. The filamentous localization of septin 7 depends on CD2AP and intact actin organization. A 2-deoxy-d-glucose uptake assay indicates that depletion of septin 7 by small interfering RNA or alteration of septin assembly by forchlorfenuron facilitates glucose uptake into cells and further, knockdown of septin 7 increased the interaction of VAMP2 with nephrin and syntaxin 4. The data indicate that septin 7 hinders GSV trafficking and further, the interaction of septin 7 with nephrin in glomeruli suggests that septin 7 may participate in the regulation of glucose transport in podocytes.
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Affiliation(s)
- Anita A Wasik
- Department of Pathology, Haartman Institute, 00014 University of Helsinki, Finland
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104
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Chase SE, Encina CV, Stolzenburg LR, Tatum AH, Holzman LB, Krendel M. Podocyte-specific knockout of myosin 1e disrupts glomerular filtration. Am J Physiol Renal Physiol 2012; 303:F1099-106. [PMID: 22811491 DOI: 10.1152/ajprenal.00251.2012] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Myosin 1e (myo1e) is an actin-dependent molecular motor that plays an important role in kidney functions. Complete knockout of myo1e in mice and Myo1E mutations in humans are associated with nephrotic syndrome and focal segmental glomerulosclerosis. In this paper, we tested the hypothesis that myo1e is necessary for normal functions of glomerular visceral epithelial cells (podocytes) using podocyte-targeted knockout of myo1e. Myo1e was selectively knocked out in podocytes using Cre-mediated recombination controlled by the podocin promoter. Myo1e loss from podocytes resulted in proteinuria, podocyte foot process effacement, and glomerular basement membrane disorganization. Our findings indicate that myo1e expression in podocytes is necessary for normal glomerular filtration and that podocyte defects are likely to represent the primary pathway leading to glomerular disease associated with Myo1E mutations.
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Affiliation(s)
- Sharon E Chase
- Dept. of Cell and Developmental Biology, SUNY Upstate Medical Univ., 750 E. Adams St., Syracuse, NY 13210, USA
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105
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Is the antiproteinuric effect of cyclosporine a independent of its immunosuppressive function in T cells? Int J Nephrol 2012; 2012:809456. [PMID: 22778954 PMCID: PMC3384901 DOI: 10.1155/2012/809456] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Revised: 04/20/2012] [Accepted: 05/03/2012] [Indexed: 12/21/2022] Open
Abstract
The antiproteinuric effect of cyclosporine A(CsA) has been believed to result from its immunosuppressive effect on the transcription factor NFAT in T cells. However, current evidences supporting this hypothesis are missing. A recent study showed that CsA has a direct antiproteinuric effect on podocytes, suggesting a novel non-immunosuppressive mechanism for CsA's antiproteinuric effect. Conditional NFATc1 activation in podoyctes per se is sufficient to induce proteinuria in mice, indicating that NFAT activation in podocytes is a critical pathogenic molecular event leading to podocyte injury and proteinuria. Meanwhile, evidence showed that TRPC6-mediated Ca(2+) influx stimulates NFAT-dependent TRPC6 expression. Altogether, these advances in podocyte research indicate that calcineurin-NFAT signal or calcineurin-synaptopodin axis has a direct proteinuric effect on podocytes which raises the possibility of developing specific antiproteinuric drugs that lack the unwanted effects of calcineurin or NFAT inhibition.
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106
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Schell C, Huber TB. New players in the pathogenesis of focal segmental glomerulosclerosis. Nephrol Dial Transplant 2012; 27:3406-12. [PMID: 22767631 DOI: 10.1093/ndt/gfs273] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Focal segmental glomerulosclerosis (FSGS) is the most common primary glomerular disorder causing end-stage renal disease. Since the first description of this clinicopathological entity in the early 1930s, various studies have identified numerous underlying pathogenetic mechanisms. Nevertheless, FSGS is still a complex, only partially understood and in its classification sometimes confusing disease. A unifying pathophysiological concept has not been identified and might not even exist. However, research efforts of past decades identified FSGS as a podocytopathy with several podocyte molecules being key players in the development and the course of FSGS. Podocytes are crucially involved in the formation of the glomerular barrier and any assault on their delicate physiological balance and architecture can result in the development of proteinuria. The following review article will introduce most recent examples identifying novel players in the complex pathogenesis of FSGS.
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107
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Huber TB, Edelstein CL, Hartleben B, Inoki K, Jiang M, Koya D, Kume S, Lieberthal W, Pallet N, Quiroga A, Ravichandran K, Susztak K, Yoshida S, Dong Z. Emerging role of autophagy in kidney function, diseases and aging. Autophagy 2012; 8:1009-31. [PMID: 22692002 PMCID: PMC3429540 DOI: 10.4161/auto.19821] [Citation(s) in RCA: 207] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2011] [Revised: 02/24/2012] [Accepted: 02/27/2012] [Indexed: 02/06/2023] Open
Abstract
Autophagy is a highly conserved process that degrades cellular long-lived proteins and organelles. Accumulating evidence indicates that autophagy plays a critical role in kidney maintenance, diseases and aging. Ischemic, toxic, immunological, and oxidative insults can cause an induction of autophagy in renal epithelial cells modifying the course of various kidney diseases. This review summarizes recent insights on the role of autophagy in kidney physiology and diseases alluding to possible novel intervention strategies for treating specific kidney disorders by modifying autophagy.
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Affiliation(s)
- Tobias B Huber
- Renal Division, University Hospital Freiburg; Freiburg, Germany.
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108
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Ding WY, Saleem MA. Current concepts of the podocyte in nephrotic syndrome. Kidney Res Clin Pract 2012; 31:87-93. [PMID: 26889414 PMCID: PMC4715158 DOI: 10.1016/j.krcp.2012.04.323] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2012] [Revised: 04/09/2012] [Accepted: 04/12/2012] [Indexed: 01/08/2023] Open
Abstract
Nephrotic syndrome is a disorder of the glomerular filtration barrier, and central to the filtration mechanism of the glomerular filtration barrier is the podocyte. We are starting to better understand how this cell, with its unique architectural features, fulfils its exact filtration properties. The multiprotein complex between adjacent podocyte foot processes, the slit diaphragm, is essential to the control of the actin cytoskeleton and cell morphology. Many of the proteins within the slit diaphragm, including nephrin, podocin, transient receptor potential-6 channel, and α-actinin-4, have been identified via genetic studies of inherited nephrotic syndromes. Signaling from slit diaphragm proteins to the actin cytoskeleton is mediated via the Rho GTPases. These are thought to be involved in the control of podocyte motility, which has been postulated as a focus of proteinuric pathways. Nephrotic syndrome is currently treated with immunosuppressive therapy, with significant adverse effects. These therapies may work in nephrotic syndrome due to specific effects on the podocytes. This review aims to describe our current understanding of the cellular pathways and molecules within the podocyte relevant to nephrotic syndrome and its treatment. With our current knowledge of the cellular biology of the podocyte, there is much hope for targeted therapies for nephrotic syndromes.
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Affiliation(s)
- Wen Y Ding
- Academic Renal Unit, University of Bristol, Southmead Hospital, Bristol, UK
| | - Moin A Saleem
- Academic Renal Unit, University of Bristol, Southmead Hospital, Bristol, UK
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109
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Müller-Krebs S, Kihm LP, Madhusudhan T, Isermann B, Reiser J, Zeier M, Schwenger V. Human RAGE antibody protects against AGE-mediated podocyte dysfunction. Nephrol Dial Transplant 2012; 27:3129-36. [DOI: 10.1093/ndt/gfs005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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110
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Asanuma K, Hidaka T, Tomino Y. [The cutting-edge of medicine; the role of podocytes in renal diseases]. NIHON NAIKA GAKKAI ZASSHI. THE JOURNAL OF THE JAPANESE SOCIETY OF INTERNAL MEDICINE 2012; 101:1092-101. [PMID: 22730741 DOI: 10.2169/naika.101.1092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Katsuhiko Asanuma
- Division of Nephrology, Juntendo University Graduate School of Medicine, Japan
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111
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Norden AG, Unwin RJ. Is the Albumin Retrieval Hypothesis a Paradigm Shift for Nephrology? J Am Soc Nephrol 2012; 23:569-71. [DOI: 10.1681/asn.2012020207] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
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112
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Ghayur A, Liu L, Kolb M, Chawla A, Lambe S, Kapoor A, Margetts PJ. Adenovirus-mediated gene transfer of TGF-β1 to the renal glomeruli leads to proteinuria. THE AMERICAN JOURNAL OF PATHOLOGY 2011; 180:940-951. [PMID: 22203053 DOI: 10.1016/j.ajpath.2011.11.023] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2011] [Revised: 11/01/2011] [Accepted: 11/11/2011] [Indexed: 10/14/2022]
Abstract
The mechanism of proteinuria in many common kidney diseases involves glomerular hemodynamic effects and local expression of angiogenic, fibrogenic, and vasoactive factors. Transforming growth factor (TGF)-β has been associated with many diseases involving proteinuria and renal fibrosis. TGF-β has been shown to induce podocyte dedifferentiation in vitro, but its in vivo effects on the glomerular filtration barrier are not well described. In this study, we used an adenovirus vector to transfer active TGF-β1 to the glomeruli of rat kidneys. Transient TGF-β1 overexpression induced significant proteinuria, podocyte foot process effacement, nephrin down-regulation, and nephrinuria. The expression of synaptopodin was also significantly down-regulated by TGF-β1. Increased glomerular expression of Snail, suggestive of an in vivo dedifferentiation process, was associated with a loss of podocyte epithelial markers. The expression of angiopoietin-1 and angiopoietin-2 was significantly increased in TGF-β1-transfected glomeruli, and TGF-β1 increased the expression of the angiopoietin receptor, Tie2, in podocyte cell culture. TGF-β1 down-regulated nephrin and synaptopodin expression in podocytes in cell culture; this effect was reversed by the blockade of both angiopoietin and Tie2 activities. These findings suggest that locally produced TGF-β1 can cause podocyte dedifferentiation marked by a loss of synaptopodin, nephrin, and foot process effacement, partly regulated by angiopoietins. This process represents a novel pathway that may explain proteinuria in a variety of common renal diseases.
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Affiliation(s)
- Ayesha Ghayur
- Department of Medicine, McMaster University, Hamilton, Ontario, Canada
| | - Limin Liu
- Department of Medicine, McMaster University, Hamilton, Ontario, Canada
| | - Martin Kolb
- Department of Medicine, McMaster University, Hamilton, Ontario, Canada
| | - Arun Chawla
- Department of Surgery, McMaster University, Hamilton, Ontario, Canada
| | - Shahid Lambe
- Department of Surgery, McMaster University, Hamilton, Ontario, Canada
| | - Anil Kapoor
- Department of Surgery, McMaster University, Hamilton, Ontario, Canada
| | - Peter J Margetts
- Department of Medicine, McMaster University, Hamilton, Ontario, Canada.
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113
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Lydia A, Asanuma K, Nonaka K, Takagi M, Jeong KH, Kodama F, Asao R, Asanuma E, Prodjosudjadi W, Tomino Y. Effects of 22-oxa-calcitriol on podocyte injury in adriamycin-induced nephrosis. Am J Nephrol 2011; 35:58-68. [PMID: 22189044 DOI: 10.1159/000334626] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2011] [Accepted: 10/24/2011] [Indexed: 12/11/2022]
Abstract
BACKGROUND In various animal studies, vitamin D has been shown to have a significant effect on reduction of proteinuria and the progression of kidney disease. However, little is known on its renoprotective effect in adriamycin (ADR)-induced nephrosis mice. The present study was intended to determine the therapeutic benefit of 22-oxa-calcitriol (OCT), a vitamin D analog, in reducing proteinuria and its renoprotective effect, i.e. preventing podocyte injury on ADR-induced nephrosis mice. METHODS Three experimental groups were used as follows: (1) nephrosis mice, established by a single intravenous injection of ADR; (2) ADR+OCT mice, nephrosis mice treated with OCT, and (3) mice treated only with OCT as the control group. Podocyte injury was assessed by podocyte apoptosis using the TUNEL assay, podocyte counting, podocyte-specific expressed protein by immunofluorescence and Western blot analysis, and foot process effacement using electron microscopy. RESULTS Lower proteinuria was observed in ADR+OCT mice. Improvement in glomerulosclerosis and interstitial fibrosis, and prevention of glomerular hyperfiltration were observed in ADR+OCT mice. Immunofluorescence and Western blot analyses showed restoration of downregulated expression of nephrin, CD2AP and podocin. Nevertheless, dendrin expression was not restored. An insignificant reduction in podocyte numbers was found in ADR+OCT mice. Complete foot process effacement was partially prevented in ADR+OCT mice. CONCLUSIONS The results indicate that OCT reduces podocyte injury and has renoprotective effects in ADR nephrosis mice.
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Affiliation(s)
- Aida Lydia
- Division of Nephrology, Department of Internal Medicine, Juntendo University Faculty of Medicine, Tokyo, Japan
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