Proteomic profiling of kidney biopsies in nephrotic syndrome.

Background: Minimal change disease (MCD) and focal segmental glomerulosclerosis (FSGS) are patterns of kidney injury observed in the filtering units of the kidney known as glomeruli. These histological patterns are seen in kidney biopsies from individuals with idiopathic nephrotic syndrome (iNS), which occurs in both children and adults. However, there is some indication that MCD and FSGS are within the same phenotypic spectrum.

Collagen IV assembly is influenced by fluid flow in kidney cell-derived matrices.

Kidney podocytes and endothelial cells assemble a complex and dynamic basement membrane that is essential for kidney filtration. Whilst many components of this specialised matrix are known, the influence of fluid flow on its assembly and organisation remains poorly understood. Using the coculture of podocytes and glomerular endothelial cells in a low-shear stress, high-flow bioreactor, we investigated the effect of laminar fluid flow on the composition and assembly of cell-derived matrix.

Lung extracellular matrix modulates KRT5 basal cell activity in pulmonary fibrosis.

Aberrant expansion of KRT5 basal cells in the distal lung accompanies progressive alveolar epithelial cell loss and tissue remodelling during fibrogenesis in idiopathic pulmonary fibrosis (IPF). The mechanisms determining activity of KRT5 cells in IPF have not been delineated. Here, we reveal a potential mechanism by which KRT5 cells migrate within the fibrotic lung, navigating regional differences in collagen topography.

Integrating basic science with translational research: the 13th International Podocyte Conference 2021.

The 13th International Podocyte Conference was held in Manchester, UK, and online from July 28 to 30, 2021. Originally planned for 2020, this biannual meeting was postponed by a year because of the coronavirus disease 2019 (COVID-19) pandemic and proceeded as an innovative hybrid meeting. In addition to in-person attendance, online registration was offered, and this attracted 490 conference registrations in total.

Structure of PLA2R reveals presentation of the dominant membranous nephropathy epitope and an immunogenic patch.

Membranous nephropathy is an autoimmune kidney disease caused by autoantibodies targeting antigens present on glomerular podocytes, instigating a cascade leading to glomerular injury. The most prevalent circulating autoantibodies in membranous nephropathy are against phospholipase A2 receptor (PLA2R), a cell surface receptor. The dominant epitope in PLA2R is located within the cysteine-rich domain, yet high-resolution structure-based mapping is lacking.

A basement membrane discovery pipeline uncovers network complexity, regulators, and human disease associations.

Basement membranes (BMs) are ubiquitous extracellular matrices whose composition remains elusive, limiting our understanding of BM regulation and function. By developing a bioinformatic and in vivo discovery pipeline, we define a network of 222 human proteins and their animal orthologs localized to BMs. Network analysis and screening in and zebrafish uncovered BM regulators, including ADAMTS, ROBO, and TGFβ.

A Point-of-Care Immunosensor Based on a Quartz Crystal Microbalance with Graphene Biointerface for Antibody Assay.

We present a sensitive and low-cost immunoassay, based on a customized open-source quartz crystal microbalance coupled with graphene biointerface sensors (G-QCM), to quantify antibodies in undiluted patient serum. We demonstrate its efficacy for a specific antibody against the phospholipase A2 receptor (anti-PLA2R), which is a biomarker in primary membranous nephropathy. A novel graphene-protein biointerface was constructed by adsorbing a low concentration of denatured bovine serum albumin (dBSA) on the reduced graphene oxide (rGO) sensor surface.

The anti-PLA2R antibody in membranous nephropathy: what we know and what remains a decade after its discovery.

The discovery in 2009 of the M-type phospholipase A2 receptor (PLA2R) as the primary target in membranous nephropathy (MN) greatly advanced basic and clinical research. Primary MN is now considered a renal-limited autoimmune disease, with antibodies against PLA2R (aPLA2Rab) identified in 70-80 % of patients of various ethnic groups. Although the use of aPLA2Rab as a diagnostic and prognostic biomarker is now widely accepted, many questions related to the development of the auto-immune response, the role of IgG subclasses and antigenic epitopes, and the pathways to podocyte injury remain unresolved.

PLAR binds to the annexin A2-S100A10 complex in human podocytes.

Phospholipase A receptor (PLAR) is a member of the mannose receptor family found in podocytes in human kidney. PLAR is the target of the autoimmune disease, membranous nephropathy, characterised by production of anti-PLAR autoantibodies which bind to the podocyte. However the function of PLAR in health and in disease remains unclear.

Identification of a major epitope recognized by PLA2R autoantibodies in primary membranous nephropathy.

Phospholipase A2 receptor 1 (PLA2R) is a target autoantigen in 70% of patients with idiopathic membranous nephropathy. We describe the location of a major epitope in the N-terminal cysteine-rich ricin domain of PLA2R that is recognized by 90% of human anti-PLA2R autoantibodies. The epitope was sensitive to reduction and SDS denaturation in the isolated ricin domain and the larger fragment containing the ricin, fibronectin type II, first and second C-type lectin domains (CTLD).

Armet/Manf and Creld2 are components of a specialized ER stress response provoked by inappropriate formation of disulphide bonds: implications for genetic skeletal diseases.

Mutant matrilin-3 (V194D) forms non-native disulphide bonded aggregates in the rER of chondrocytes from cell and mouse models of multiple epiphyseal dysplasia (MED). Intracellular retention of mutant matrilin-3 causes endoplasmic reticulum (ER) stress and induces an unfolded protein response (UPR) including the upregulation of two genes recently implicated in ER stress: Armet and Creld2. Nothing is known about the role of Armet and Creld2 in human genetic diseases.

Loss of matrilin 1 does not exacerbate the skeletal phenotype in a mouse model of multiple epiphyseal dysplasia caused by a Matn3 V194D mutation.

Objective: Mutations in matrilin 3 can result in multiple epiphyseal dysplasia (MED), a disease characterized by delayed and irregular bone growth and early-onset osteoarthritis. Although intracellular retention of the majority of mutant matrilin 3 was previously observed in a murine model of MED caused by a Matn3 V194D mutation, some mutant protein was secreted into the extracellular matrix. Thus, it was proposed that secretion of mutant matrilin 3 may be dependent on the formation of hetero-oligomers with matrilin 1.

Structural and functional investigations of Matrilin-1 A-domains reveal insights into their role in cartilage ECM assembly.

Matrilin-1 is expressed predominantly in cartilage and co-localizes with matrilin-3 with which it can form hetero-oligomers. We recently described novel structural and functional features of the matrilin-3 A-domain (M3A) and demonstrated that it bound with high affinity to type II and IX collagens. Interactions preferentially occurred in the presence of Zn(2+) suggesting that matrilin-3 has acquired a requirement for specific metal ions for activation and/or molecular associations.

A recessive skeletal dysplasia, SEMD aggrecan type, results from a missense mutation affecting the C-type lectin domain of aggrecan.

Analysis of a nuclear family with three affected offspring identified an autosomal-recessive form of spondyloepimetaphyseal dysplasia characterized by severe short stature and a unique constellation of radiographic findings. Homozygosity for a haplotype that was identical by descent between two of the affected individuals identified a locus for the disease gene within a 17.4 Mb interval on chromosome 15, a region containing 296 genes.

Novel mutations in exon 2 of MATN3 affect residues within the alpha-helices of the A-domain and can result in the intracellular retention of mutant matrilin-3.

Multiple epiphyseal dysplasia (MED) is a clinically variable and genetically heterogeneous chondrodysplasia characterized by mild to moderate short stature and early onset osteoarthritis. Some forms of MED result from mutations in the gene encoding the cartilage structural protein matrilin-3 (MATN3). The majority of MATN3 mutations affect conserved residues within the beta-sheet of the single A-domain of matrilin-3.

Structural and functional characterization of recombinant matrilin-3 A-domain and implications for human genetic bone diseases.

Mutations in matrilin-3 result in multiple epiphyseal dysplasia, which is characterized by delayed and irregular bone growth and early onset osteoarthritis. The majority of disease-causing mutations are located within the beta-sheet of the single A-domain of matrilin-3, suggesting that they disrupt the structure and/or function of this important domain. Indeed, the expression of mutant matrilin-3 results in its intracellular retention within the rough endoplasmic reticulum of cells, where it elicits an unfolded protein response.