Autoantibodies Targeting Nephrin in Podocytopathies.

Background: Minimal change disease and primary focal segmental glomerulosclerosis in adults, along with idiopathic nephrotic syndrome in children, are immune-mediated podocytopathies that lead to nephrotic syndrome. Autoantibodies targeting nephrin have been found in patients with minimal change disease, but their clinical and pathophysiological roles are unclear.

Methods: We conducted a multicenter study to analyze antinephrin autoantibodies in adults with glomerular diseases, including minimal change disease, focal segmental glomerulosclerosis, membranous nephropathy, IgA nephropathy, antineutrophil cytoplasmic antibody-associated glomerulonephritis, and lupus nephritis, as well as in children with idiopathic nephrotic syndrome and in controls.

Introduction of a novel chimeric active immunization mouse model of PLA2R1-associated membranous nephropathy.

The phospholipase A2 receptor 1 (PLA2R1) is the major target antigen in patients with membranous nephropathy (MN), an antibody-mediated autoimmune glomerular disease. Investigation of MN pathogenesis has been hampered by the lack of reliable animal models. Here, we overcome this issue by generating a transgenic mouse line expressing a chimeric PLA2R1 (chPLA2R1) consisting of three human PLA2R1 domains (cysteine-rich, fibronectin type-II and CTLD1) and seven murine PLA2R1 domains (CTLD2-8) specifically in podocytes.

The classical pathway triggers pathogenic complement activation in membranous nephropathy.

Membranous nephropathy (MN) is an antibody-mediated autoimmune disease characterized by glomerular immune complexes containing complement components. However, both the initiation pathways and the pathogenic significance of complement activation in MN are poorly understood. Here, we show that components from all three complement pathways (alternative, classical and lectin) are found in renal biopsies from patients with MN.

Podocyte expression of human phospholipase A2 receptor 1 causes immune-mediated membranous nephropathy in mice.

Antibody-mediated autoimmune pathologies like membranous nephropathy are difficult to model, particularly in the absence of local target antigen expression in model organisms such as mice and rats; as is the case for phospholipase A2 receptor 1 (PLA2R1), the major autoantigen in membranous nephropathy. Here, we generated a transgenic mouse line expressing the full-length human PLA2R1 in podocytes, which has no kidney impairment after birth. Beginning from the age of three weeks, these mice spontaneously developed anti-human PLA2R1 antibodies, a nephrotic syndrome with progressive albuminuria and hyperlipidemia, and the typical morphological signs of membranous nephropathy with granular glomerular deposition of murine IgG in immunofluorescence and subepithelial electron-dense deposits by electron microscopy.

A novel mouse model of phospholipase A2 receptor 1-associated membranous nephropathy mimics podocyte injury in patients.

The phospholipase A2 receptor 1 (PLA2R1) is the major autoantigen in patients suffering from membranous nephropathy. To date, the lack of endogenous glomerular expression of PLA2R1 in mice and rats has impeded the establishment of PLA2R1-dependent animal models of this disease. Here, we generated a transgenic mouse line expressing murine full-length PLA2R1 in podocytes.

The Most N-Terminal Region of THSD7A Is the Predominant Target for Autoimmunity in THSD7A-Associated Membranous Nephropathy.

Thrombospondin type 1 domain-containing 7A (THSD7A) has been identified as a pathogenic autoantigen in membranous nephropathy (MN). However, the THSD7A epitopes targeted by patient autoantibodies are unknown. We performed an analysis of the THSD7A multidomain structure, expressed the folded domains in HEK293 cells, and tested for domain reactivity with 31 serum samples from patients with THSD7A-associated MN using Western and native blotting.

Rho-kinase inhibition prevents proteinuria in immune-complex-mediated antipodocyte nephritis.

Podocyte foot process retraction is a hallmark of proteinuric glomerulonephritis. Cytoskeletal rearrangement causes a redistribution of slit membrane proteins from the glomerular filtration barrier towards the cell body. However, the underlying signaling mechanisms are presently unknown.

Nephrotic syndrome and subepithelial deposits in a mouse model of immune-mediated anti-podocyte glomerulonephritis.

Subepithelial immune complex deposition in glomerular disease causes local inflammation and proteinuria by podocyte disruption. A rat model of membranous nephropathy, the passive Heymann nephritis, suggests that Abs against specific podocyte Ags cause subepithelial deposit formation and podocyte foot process disruption. In this study, we present a mouse model in which a polyclonal sheep anti-mouse podocyte Ab caused subepithelial immune complex formation.

Simian virus 40 activates ATR-Delta p53 signaling to override cell cycle and DNA replication control.

During infection, simian virus 40 (SV40) attempts to take hold of the cell, while the host responds with various defense systems, including the ataxia-telangiectasia mutated/ATM-Rad3 related (ATM/ATR)-mediated DNA damage response pathways. Here we show that upon viral infection, ATR directly activates the p53 isoform Δp53, leading to upregulation of the Cdk inhibitor p21 and downregulation of cyclin A-Cdk2/1 (AK) activity, which force the host to stay in the replicative S phase. Moreover, downregulation of AK activity is a prerequisite for the generation of hypophosphorylated, origin-competent DNA polymerase α-primase (hypo-Polα), which is, unlike AK-phosphorylated Polα (P-Polα), recruited by SV40 large T antigen (T-Ag) to initiate viral DNA replication.

Rho kinase inhibition attenuates LPS-induced renal failure in mice in part by attenuation of NF-kappaB p65 signaling.

Rho kinase signaling regulates inflammatory cell migration and chemokine production. We therefore investigated the mechanisms of Rho-kinase-dependent inflammation in lipopolysaccharide (LPS)-induced renal failure. C57/BL6 mice received intraperitoneal LPS with or without daily treatment with specific Rho kinase inhibitors (Y-27632 or HA-1077; 5 mg/kg).

A novel human p53 isoform is an essential element of the ATR-intra-S phase checkpoint.

The archetypal human tumor suppressor p53 is considered to have unique transactivation properties. The assumption is based on the fact that additionally identified human p53 isoforms lack transcriptional activity. However, we provide evidence for the existence of an alternatively spliced p53 isoform (Deltap53) that exerts its transcriptional activity independent from p53.