Variable Expression of Neural Cell Adhesion Molecule Isoforms in Renal Tissue: Possible Role in Incipient Renal Fibrosis

Neural cell adhesion molecule 1 is a novel autoantigen in membranous lupus nephritis

Membranous lupus nephritis is a frequent cause of nephrotic syndrome in patients with systemic lupus erythematosus. It has been shown in phospholipase A2 receptor positive membranous nephropathy that known antibodies can be detected within sera, determination of the target autoantigen can have diagnostic significance, inform prognosis, and enable non-invasive monitoring of disease activity. Here we utilized mass spectrometry for antigen discovery in laser captured microdissected glomeruli from formalin-fixed paraffin embedded tissue and tissue protein G immunoprecipitation studies to interrogate immune complexes from frozen kidney biopsy tissue. We identified neural cell adhesion molecule 1 (NCAM1) to be a target antigen in some cases of membranous lupus nephritis and within rare cases of primary membranous nephropathy. The prevalence of NCAM1 association was 6.6% of cases of membranous lupus nephritis and in 2.0% of primary membranous nephropathy cases. NCAM1 was found to colocalize with IgG within glomerular immune deposits by confocal microscopy. Additionally, serum from patients with NCAM1-associated membranous nephropathy showed reactivity to NCAM1 recombinant protein on Western blotting and by indirect immunofluorescence assay, demonstrating the presence of circulating antibodies. Thus, we propose that NCAM1 is a target autoantigen in a subset of patients with membranous lupus nephritis. Future studies are needed to determine whether anti-NCAM1 antibody levels correlate with disease activity or response to therapy.

Mechanisms of Primary Membranous Nephropathy

Membranous nephropathy (MN) is an autoimmune disease of the kidney glomerulus and one of the leading causes of nephrotic syndrome. The disease exhibits heterogenous outcomes with approximately 30% of cases progressing to end-stage renal disease. The clinical management of MN has steadily advanced owing to the identification of autoantibodies to the phospholipase A2 receptor (PLA2R) in 2009 and thrombospondin domain-containing 7A (THSD7A) in 2014 on the podocyte surface. Approximately 50–80% and 3–5% of primary MN (PMN) cases are associated with either anti-PLA2R or anti-THSD7A antibodies, respectively. The presence of these autoantibodies is used for MN diagnosis; antibody levels correlate with disease severity and possess significant biomarker values in monitoring disease progression and treatment response. Importantly, both autoantibodies are causative to MN. Additionally, evidence is emerging that NELL-1 is associated with 5–10% of PMN cases that are PLA2R- and THSD7A-negative, which moves us one step closer to mapping out the full spectrum of PMN antigens. Recent developments suggest exostosin 1 (EXT1), EXT2, NELL-1, and contactin 1 (CNTN1) are associated with MN. Genetic factors and other mechanisms are in place to regulate these factors and may contribute to MN pathogenesis. This review will discuss recent developments over the past 5 years.

Extracellular vesicle-associated proteins as potential biomarkers

Every cell in the body secretes extracellular vesicles (EVs) possibly as cellular signaling components and these cell-derivatives can be found in multiple numbers in biological fluids. EVs have in the scientific field received great attention in relation to pathophysiology and disease diagnostics. Altered protein expressions associated with circulating EVs in diseased individuals can serve as biomarkers for different disease states. This capacity paves the way for non-invasive screening tools and early diagnostic markers. However, no isolation method of EVs has been acknowledged as the "golden standard," thus reproducibility of the studies remains inadequate. Increasing interest in EV proteins as disease biomarkers could give rise to more scientific knowledge with diagnostic applicability. In this chapter, studies of proteins believed to be associated with EVs within cancer, autoimmunity, metabolic and neurodegenerative diseases have been outlined.

Endosomal dysfunction impacts extracellular vesicle release: Central role in Aβ pathology

Alzheimer's Disease (AD) is characterized by progressive loss of cognitive abilities; senile plaques represent the major histopathological findings. Amyloid precursor protein (APP) processing machinery, and its product amyloid-beta (Aβ) peptide, have been found in extracellular vesicles (EVs), specifically exosomes, which allows for Aβ peptide aggregation and subsequent senile plaques deposition. We review the APP processing imbalance in EVs, autophagic and endosomal pathways in AD. Increased intraluminal vesicle (ILV) production and exosome release appear to counteract the endosomal dysfunction of APP processing; however, this process results in elevated amyloidogenic processing of APP and augmented senile plaque deposition. Several players related to APP processing and dysfunctional endosomal-lysosomal-exosomal (and other EVs) pathway are described, and the interconnected systems are discussed. The components Arc, p75, Rab11 and retromer complex emerge as candidates for key convergent mechanisms that lead to increased EVs loaded with APP machinery and Aβ levels, in atrophy and damage of basal forebrain cholinergic neurons in AD.

Modulation of NCAM/FGFR1 signaling suppresses EMT program in human proximal tubular epithelial cells

Neural cell adhesion molecule (NCAM) and fibroblast growth factor receptor 1 (FGFR1) cross-talk have been involved in epithelial-to-mesenchymal transition (EMT) process during carcinogenesis. Since EMT also contributes to maladaptive repair and parenchymal damage during renal fibrosis, we became encouraged to explore the role of NCAM/FGFR1 signaling as initiating or driving forces of EMT program in cultured human proximal tubular epithelial cells (TECs). TECs stimulated with TGF-β1 (10ng/mL) was used as an established in vitro EMT model. TGF-β1 downstream effectors were detected in vitro, as well as in 50 biopsies of different human kidney diseases to explore their in vivo correlation. NCAM/FGFR1 signaling and its modulation by FGFR1 inhibitor PD173074 (100nM) were analyzed by light microscopy, immunolabeling, qRT-PCR and scratch assays. Morphological changes associated with EMT appeared 48h after TGF-ß1 treatment and was clearly apparent after 72 hours, followed by loss of CDH1 (encoding E-Cadherin) and transcriptional induction of SNAI1 (SNAIL), SNAI2 (SLUG), TWIST1, MMP2, MMP9, CDH2 (N-Cadherin), ITGA5 (integrin-α5), ITGB1 (integrin-β1), ACTA2 (α-SMA) and S100A4 (FSP1). Moreover, at the early stage of EMT program (24 hours upon TGF-β1 exposure), transcriptional induction of several NCAM isoforms along with FGFR1 was observed, implicating a mechanistic link between NCAM/FGFR1 signaling and induction of EMT. These assumptions were further supported by the inhibition of the EMT program after specific blocking of FGFR1 signaling by PD173074. Finally, there was evidence for an in vivo TGF-β1 pathway activation in diseased human kidneys and correlation with impaired renal excretory functions. Collectively, NCAM/FGFR1 signaling appears to be involved in the initial phase of TGF-ß1 initiated EMT which can be effectively suppressed by application of FGFR inhibitor.

Production and characterization of monoclonal antibody against a triple negative breast cancer cell line

Breast cancer is the most prevalent malignancy among women around the world such that more than 1,400,000 new cases are being diagnosed each year. Despite immense studies over many years on diagnosis and treatment of breast cancer, about 30% of treated patients will relapse and require subsequent therapy. By development of hybridoma technology, murine monoclonal antibodies (MAbs) against several human tumor-associated antigens have been produced and characterized in many laboratories. The purpose of these studies is to generate effective monoclonal antibodies that could be useful in tumor diagnosis and therapy. In this study, splenic lymphocytes of immunized BALB/c mouse with a new established breast cancer cell line (Pari-ICR cell line, established in Shiraz Institute for Cancer Research) were fused with the mouse myeloma cell line SP2/0 in the presence of polyethylene glycol. We generated a panel of monoclonal antibodies against the newly established cell line. The hybrid cultures were screened by flow cytometry. Hybridomas that produced antibody to surface antigens of immunizing cell line but not to Human Gingival Fibroblasts, adipose stem cells, and leucocytes isolated from peripheral blood were selected and cloned by limiting dilution method. The 1E3 clone (IgG2a type) that displayed clonal stability was further analyzed for specificity by flow cytometry. MAb 1E3 showed weak to strong reactivity to other cell lines compared with Pari-ICR cell line. Antigen identification was performed by a workflow consisting of immunoaffinity purification, SDS-PAGE, Western blotting, and mass spectrometry analysis. The target of 1E3 mAb was identified as NCAM1. In conclusion, using the antibody-based strategy we identified NCAM1 as a potential therapeutic target and biomarker for breast cancer.

Molecular imaging of the kidney in lupus nephritis to characterize response to treatment

The consequences of treatment for the kidney at the molecular level have not been explored in human lupus nephritis (LN). In this investigation, changes in intrarenal transcript expression were measured and correlated with response in a LN cohort that underwent serial kidney biopsies. The intrarenal transcript expression of 19 patients with proliferative LN (Class III or IV) was measured at diagnostic biopsy (Bx1) and after induction therapy was completed (Bx2) using Nanostring technology. Patients were segregated by clinical response into complete responders (n = 5, CR) or nonresponders (n = 4, NR). Transcript expression for each biopsy was compared with normal controls (n = 4), and the change in expression was compared in each responder group and between groups. Compared with controls, the CR group had 21 and 28, whereas NR had 45 and 103 differentially-expressed transcripts at Bx1 and Bx2, respectively. The profiles of these differentially-expressed genes indicated that the type I and II interferon, alternative complement and T cell signaling pathways discriminated CR from NR. Comparing the change in transcript expression from Bx1 to Bx2 revealed a 5-gene signature that differentiated NR from CR and included increased IL1RAP and FCAR in NR and increased NCAM1 in CR. In summary, molecular imaging of serial kidney biopsies from LN patients shows several immune and inflammatory pathways that are dysregulated in the kidneys during active disease that may serve as therapeutic targets to improve clinical response. This approach to LN biomarker development may facilitate personalized medicine in LN and improve long-term kidney outcomes.