Podocyte Changes after Induction of Acute Albuminuria in Mice by Anti-Aminopeptidase A mAb

Dijkman, Henry; Gerlofs-Nijland, Miriam E.; Laak, Jeroen van der; Wetzels, Jack F.M.; Groenen, Patricia J.T.A.; Assmann, K.J.M.

doi:10.1159/000072026

Cited by 17 publications

(18 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, others have not demonstrated this (23,24). It has been noted in several human biopsy studies (25,26) and animal models (27,28) that nephrin, podocin, and CD2AP distribution in nephrotic disease changes from a linear capillary loop pattern to a granular pattern, supportive of our observation of intracellular translocation. Previously, it has been impossible to study their location in vitro, as cell lines have not convincingly expressed these proteins.…”

Section: Discussionsupporting

confidence: 85%

Nephrotic Plasma Alters Slit Diaphragm–Dependent Signaling and Translocates Nephrin, Podocin, and CD2 Associated Protein in Cultured Human Podocytes

Coward¹,

Foster²,

Patton³

et al. 2005

Journal of the American Society of Nephrology

108

View full text Add to dashboard Cite

Podocytes are critical in maintaining the filtration barrier of the glomerulus and are dependent on the slit diaphragm (SD) proteins nephrin, podocin, and CD2-associated protein (CD2AP) to function optimally. The effects of normal human plasma and nephrotic plasma on podocytes were tested, focusing particularly on the SD complex. With the use of a conditionally immortalized human podocyte cell line, it first was shown that exposure to normal and non-nephrotic human plasma leads to a concentration of nephrin, podocin, CD2AP, and actin at the cell surface. Next, the effects of plasma from patients with nephrotic conditions to non-nephrotic conditions were compared. When exposed to all nephrotic plasma samples (and a non-human serum control), nephrin podocin and CD2AP assumed a cytoplasmic distribution; nephrin and synaptopodin were selectively downregulated, and the relocation of nephrin induced by nephrotic plasma could be rescued back to the plasma membrane by co-incubation with non-nephrotic plasma. Furthermore, intracellular calcium signaling was altered by nephrotic plasma, which was mediated by tyrosine kinase phosphorylation. With the use of nephrin mutant human cell lines, it was shown that this signaling and translocation response to normal plasma is nephrin dependent. This work demonstrates that nephrotic plasma seems to be deficient in factors that act via the podocyte SD complex, which are essential in maintaining its physiologic function. I n recent years, the podocyte slit diaphragm (SD) proteins have been shown to be central to the development of congenital and early childhood-onset human nephrotic syndromes through the seminal work of Kestila and Boute (1,2). Furthermore, the importance of CD2-associated protein (CD2AP) is critical in maintaining the integrity of the slit diaphragm (3) and has been demonstrated to be related closely to nephrin, podocin, and actin in human podocytes in culture (4). Of great interest is the role of these proteins in the much more common acquired nephrotic conditions, but in vitro work has been hampered by the lack of a representative human podocyte cell line. The podocyte displays a highly developed architectural phenotype, and in particular the SD is a unique type of cell junction (5), the permeability characteristics of which are determined by the unique proteins located there. Of these proteins, nephrin has been shown to be capable of signaling in combination with podocin (6), and these molecules are known to be intimately related to the actin cytoskeleton and to CD2AP in the podocyte (4,7). We hypothesized that these critical SD proteins are maintained in their structural conformation by factors in normal plasma that signal through this molecular complex. We studied the properties of the SD in a conditionally immortalized human cell line (8) when cultured in plasma from patients with no renal disease and compared these properties with plasma from patients with nephrotic conditions (three patients with focal segmental glomerulosclerosis [FSGS] in relapse and the ...

show abstract

Section: Discussionsupporting

confidence: 85%

Nephrotic Plasma Alters Slit Diaphragm–Dependent Signaling and Translocates Nephrin, Podocin, and CD2 Associated Protein in Cultured Human Podocytes

Coward¹,

Foster²,

Patton³

et al. 2005

Journal of the American Society of Nephrology

108

View full text Add to dashboard Cite

show abstract

“…In our mixed genetic background, anti-APA induced mild proteinuria for approximately 24 hours, allowing increased quantities of IgG to pass into the primary filtrate. 30 When visualizing rat IgG with a specific antibody, anti-APA was still detected within tubulointerstitial capillaries and along the brush border of proximal tubule cells (Figure 7, A-D0, arrows). In wild-type controls, anti-APA rat IgG was detected on the apical as well as along the basolateral aspect of proximal tubular cells (Figure 7, A-B0, arrowheads).…”

Section: Tracing Igg and Albumin Across Proximal Tubular Cells In Fcrmentioning

confidence: 98%

“…30 After 16 hours, animals were proteinuric and euthanized; 1-mm kidney slices were fixed in 10 mM periodate, 75 mM lysine, and 2% paraformaldehyde (pH 6.2) at 4°C for 3 hours. The slices were washed in PBS for 30 minutes, cryoprotected by immersion in 2.3 M sucrose solution for 1 hour, and afterward, snap-frozen in liquid nitrogen; 20-mm cryosections were incubated with a peroxidase-labeled rabbit anti-rat IgG (Dako Glostrup, Denmark) diluted in PBS containing 1% BSA followed by three washes with PBS.…”

Section: Apa Injection and Immunoelectron Microscopymentioning

confidence: 99%

Albumin Is Recycled from the Primary Urine by Tubular Transcytosis

Tenten¹,

Menzel²,

Kunter³

et al. 2013

Journal of the American Society of Nephrology

117

103

View full text Add to dashboard Cite

Under physiologic conditions, significant amounts of plasma protein pass the renal filter and are reabsorbed by proximal tubular cells, but it is not clear whether the endocytosed protein, particularly albumin, is degraded in lysosomes or returned to the circulatory system intact. To resolve this question, a transgenic mouse with podocyte-specific expression of doxycycline-inducible tagged murine albumin was developed. To assess potential glomerular backfiltration, two types of albumin with different charges were expressed. On administration of doxycycline, podocytes expressed either of the two types of transgenic albumin, which were secreted into the primary filtrate and reabsorbed by proximal tubular cells, resulting in serum accumulation. Renal transplantation experiments confirmed that extrarenal transcription of transgenic albumin was unlikely to account for these results. Genetic deletion of the neonatal Fc receptor (FcRn), which rescues albumin and IgG from lysosomal degradation, abolished transcytosis of both types of transgenic albumin and IgG in proximal tubular cells. In summary, we provide evidence of a transcytosis within the kidney tubular system that protects albumin and IgG from lysosomal degradation, allowing these proteins to be recycled intact. 24: 196624: -198024: , 201324: . doi: 10.1681 The main function of the kidney is to filter plasma, while at the same time, retain the majority of plasma proteins. However, a certain fraction of plasma proteins inevitably passes the glomerular filtration barrier. The most abundant and most studied plasma protein, albumin, is produced at a rate of about 15 g per day in humans. 1 In the renal glomerulus, the albumin sieving coefficient (i.e., the transport rate of albumin across the glomerular filter in relation to water) has been estimated to be below 0.001. [2][3][4] In more recent studies using intravital microscopy, the albumin sieving coefficient has been estimated to be significantly higher, although this result is still controversial. 5-7 Thus, even when assuming a tight renal filtration barrier, significant amounts of albumin pass the glomerular filterroughly in the range of 1 g per day in healthy humans, J Am Soc Nephrol

show abstract

“…[34] More recent data suggests anti-APA antibodies may induce proteinuria secondary to interference with the CD2AP/nephrin/podocyte slit diaphragm complex. [35]…”

Section: Pathogenesis Of Idiopathic Membranous Nephropathymentioning

confidence: 99%

Experimental models of membranous nephropathy

Jefferson

Pippin

Shankland

2010

Drug Discovery Today: Disease Models

View full text Add to dashboard Cite

Membranous nephropathy (MN) is one of the commonest glomerular diseases, typically presenting in older males with nephrotic syndrome. The development and characterization of animal models of MN, in particular, the passive Heymann nephritis model (PHN), has greatly advanced our understanding of this disease. In this review we discuss the different animal models of human MN that are available, with an emphasis on the PHN model, including technical issues, the typical disease course and its application to human disease.

show abstract

Podocyte Changes after Induction of Acute Albuminuria in Mice by Anti-Aminopeptidase A mAb

Cited by 17 publications

References 24 publications

Nephrotic Plasma Alters Slit Diaphragm–Dependent Signaling and Translocates Nephrin, Podocin, and CD2 Associated Protein in Cultured Human Podocytes

Nephrotic Plasma Alters Slit Diaphragm–Dependent Signaling and Translocates Nephrin, Podocin, and CD2 Associated Protein in Cultured Human Podocytes

Albumin Is Recycled from the Primary Urine by Tubular Transcytosis

Experimental models of membranous nephropathy

Contact Info

Product

Resources

About