Annexin A2 and Kidney Diseases

E53, E96, D162, E247 and D322 in Ca2+-binding domains of annexin A2 are essential for regulating intracellular [Ca2+] and crystal adhesion to renal cells via ERK1/2 and JNK signaling pathways

Annexin A2 (ANXA2) is expressed inside the cytoplasm and on the surface of renal tubular epithelial cells (RTECs) and is documented as a calcium oxalate monohydrate (COM) crystal-binding protein. Nevertheless, its molecular mechanism involved in kidney stone disease (KSD) remains underinvestigated. Herein, we performed various molecular assays to unravel the roles of ANXA2 and core residues (E53, E96, D162, E247 and D322) in its Ca2+-binding domains in the stone formation mechanism, particularly at crystal-cell adhesion step and downstream signaling cascade. ANXA2 was up-regulated in apical membranes, not cytosol, of RTECs after COM crystal exposure. Neutralizing the surface expression of ANXA2 by a specific monoclonal antibody and silencing its expression by small interfering RNA (siRNA) significantly decreased COM crystal-cell adhesion. siRNA also suppressed the COM-induced up-regulation of phospho-ERK1/2 and phospho-JNK, but not that of phospho-p38. Overexpression of ANXA2 wild-type (WT), but not that of E53A, E96A, D162A, E247A and D322A mutants of its Ca2+-binding domains, significantly increased intracellular [Ca2+], COM-cell adhesion, and phospho-ERK1/2 level. Therefore, E53, E96, D162, E247 and D322 in the Ca2+-binding domains of annexin A2 are essential for regulating intracellular [Ca2+] and COM crystal-cell adhesion via ERK1/2 and JNK signaling pathways.

Targeting AnxA2-EGFR signaling: hydroxychloroquine as a therapeutic strategy for bleomycin-induced pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a disease that causes progressive failure of lung function, and its molecular mechanism remains poorly understood. However, the AnnexinA2-epidermal growth factor receptor (EGFR) signaling pathway has been identified as playing a significant role in its development. Hydroxychloroquine, a common anti-malarial drug, has been found to inhibit this pathway and slow down the progression of IPF. To better understand the role of the AnxA2-EGFR signaling pathway in pulmonary fibrosis, an in vivo study was conducted. In this study, mice were induced with pulmonary fibrosis using bleomycin, and HCQ was administered intraperitoneally the next day of bleomycin induction. The study also employed nintedanib as a positive control. After the induction, the lungs showed increased levels of fibronectin and vimentin, along with enhanced expression of AnxA2, EGFR, and Gal-3, indicating pulmonary fibrosis. Additionally, the study also found that HCQ significantly inhibited these effects and showed antifibrotic properties similar to nintedanib. Overall, these findings suggest that HCQ can attenuate bleomycin-induced pulmonary fibrosis by inhibiting the AnxA2-EGFR signaling pathway. These results are promising for developing new treatments for IPF.

Tripartite motif (TRIM) proteins roles in the regulation of immune system responses: Focus on autoimmune diseases

The tripartite motif (TRIM) proteins are well-studied as essential modulators of many processes, including the modulation of several pathways linked to immunological reactions. Most TRIM family members can polyubiquitinate the targeted proteins by acting as E3 ubiquitin ligases. According to current research, TRIMs play a critical role in innate immune response via modifying transcription factors, pattern recognition receptors (PRRs), and key adaptor proteins within innate immunity. It is becoming clearer that TRIMs play important roles in adaptive immune response, especially in the stimulation and promotion of T cells. We highlight the E3 ubiquitin ligase functions of TRIMs in the PRRs axis linked to autoimmune disorders. By focusing on TRIM family members, we also clarify the new approaches to regulating immunological reactions to alleviate autoimmunity.

Comparative Proteomics of ccRCC Cell Lines to Identify Kidney Cancer Progression Factors

BACKGROUND/AIM

Clear cell renal cell carcinoma (ccRCC) is the most common type of kidney cancer, accounting for approximately 75% of kidney cancers. The objective of this study was to identify novel progression markers for ccRCC based on proteomics, with the goal of stage determination and early diagnosis of kidney cancer patients.

MATERIALS AND METHODS

We performed quantitative global proteomics coupled with Stable Isotope Labeling by Amino Acids in Cell Culture (SILAC) and high-resolution tandem mass spectrometry on kidney-derived cells, including HEK-293, 786-O (primary ccRCC), and Caki-1 (metastatic ccRCC) cells, to investigate the novel progression factors of ccRCC.

RESULTS

In this study, a total of 1,106 proteins were quantified. The Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were conducted for differentially expressed proteins (DEPs) that were increased in ccRCC cells compared to HEK-293 cells. Ultimately, 99 DEPs including 75 up-regulated and 24 down-regulated proteins, that were significantly altered in both ccRCC cells, were identified. Among DEPs, vimentin was identified as the most significantly changed protein. Its increased expression in ccRCC was verified through immunoblotting in ccRCC cell lines and immunohistochemistry in kidney tumors.

CONCLUSION

From the global proteomics data detected in ccRCC, we propose 99 DEPs including vimentin as progression factors.

Unraveling the proteomic landscape of fibrosis in lupus nephritis through CI-based analysis

INTRODUCTION

The underlying mechanism by which lupus nephritis (LN) progresses to chronic kidney disease remains elusive. Fibrosis is a hallmark feature of chronic kidney disease, including LN. The chronicity index (CI) score, which incorporates glomerular sclerosis, fibrous crescents, tubular atrophy, and interstitial fibrosis, summarizes the extent of kidney tissue fibrosis.

METHOD

In this study, we employed label-free quantitative proteomics based on mass spectrometry to generate kidney protein profiles with varying CI scores.

RESULTS

A total of 98 proteins exhibiting linear correlation with CI scores were initially screened out by linear model (CI linearly related proteins), and subsequently, 12 key proteins were derived based on the CI linearly related proteins using Cytohubba. LN patients were stratified into two subtypes based on CI scores and epithelial-mesenchymal transition (EMT) characteristics. These subtypes exhibited significant disparities in immune infiltration and molecular pathways. The high EMT group exhibited heightened activation of immune cells, such as memory B cells, gamma delta T cells, and resting mast cells. Gene Set Enrichment Analysis (GSEA) uncovered substantial dysregulation in critical biological processes and signaling pathways, including NF-κB, JNK, PI3K/AKT/mTOR signaling pathway, lipoprotein biosynthetic process, and endocytosis, in both subgroups.

CONCLUSION

In conclusion, this study establishes molecular subgroups based on the CI score, providing novel insights into the molecular mechanisms governing chronicity in the kidneys of diverse LN patients. Key Points • Fibrosis is a fundamental and characteristic pathological process underlying the NIH-CI in LN. • Different EMT status presented variant clinical characteristics, immune features in LN.

Targeting the epidermal growth factor receptor (EGFR/ErbB) for the potential treatment of renal pathologies

Epidermal growth factor receptor (EGFR), which is referred to as ErbB1/HER1, is the prototype of the EGFR family of receptor tyrosine kinases which also comprises ErbB2 (Neu, HER2), ErbB3 (HER3), and ErbB4 (HER4). EGFR, along with other ErbBs, is expressed in the kidney tubules and is physiologically involved in nephrogenesis and tissue repair, mainly following acute kidney injury. However, its sustained activation is linked to several kidney pathologies, including diabetic nephropathy, hypertensive nephropathy, glomerulonephritis, chronic kidney disease, and renal fibrosis. This review aims to provide a summary of the recent findings regarding the consequences of EGFR activation in several key renal pathologies. We also discuss the potential interplay between EGFR and the reno-protective angiotensin-(1-7) (Ang-(1-7), a heptapeptide member of the renin-angiotensin-aldosterone system that counter-regulates the actions of angiotensin II. Ang-(1-7)-mediated inhibition of EGFR transactivation might represent a potential mechanism of action for its renoprotection. Our review suggests that there is a significant body of evidence supporting the potential inhibition of EGFR/ErbB, and/or administration of Ang-(1-7), as potential novel therapeutic strategies in the treatment of renal pathologies. Thus, EGFR inhibitors such as Gefitinib and Erlinotib that have an acceptable safety profile and have been clinically used in cancer chemotherapy since their FDA approval in the early 2000s, might be considered for repurposing in the treatment of renal pathologies.

Cytoskeleton Rearrangement in Podocytopathies: An Update

Podocyte injury can disrupt the glomerular filtration barrier (GFB), leading to podocytopathies that emphasize podocytes as the glomerulus's key organizer. The coordinated cytoskeleton is essential for supporting the elegant structure and complete functions of podocytes. Therefore, cytoskeleton rearrangement is closely related to the pathogenesis of podocytopathies. In podocytopathies, the rearrangement of the cytoskeleton refers to significant alterations in a string of slit diaphragm (SD) and focal adhesion proteins such as the signaling node nephrin, calcium influx via transient receptor potential channel 6 (TRPC6), and regulation of the Rho family, eventually leading to the disorganization of the original cytoskeletal architecture. Thus, it is imperative to focus on these proteins and signaling pathways to probe the cytoskeleton rearrangement in podocytopathies. In this review, we describe podocytopathies and the podocyte cytoskeleton, then discuss the molecular mechanisms involved in cytoskeleton rearrangement in podocytopathies and summarize the effects of currently existing drugs on regulating the podocyte cytoskeleton.

AnnexinA6: a potential therapeutic target gene for extracellular matrix mineralization

The mineralization of the extracellular matrix (ECM) is an essential and crucial process for physiological bone formation and pathological calcification. The abnormal function of ECM mineralization contributes to the worldwide risk of developing mineralization-related diseases; for instance, vascular calcification is attributed to the hyperfunction of ECM mineralization, while osteoporosis is due to hypofunction. AnnexinA6 (AnxA6), a Ca2+-dependent phospholipid-binding protein, has been extensively reported as an essential target in mineralization-related diseases such as osteoporosis, osteoarthritis, atherosclerosis, osteosarcoma, and calcific aortic valve disease. To date, AnxA6, as the largest member of the Annexin family, has attracted much attention due to its significant contribution to matrix vesicles (MVs) production and release, MVs-ECM interaction, cytoplasmic Ca2+ influx, and maturation of hydroxyapatite, making it an essential target in ECM mineralization. In this review, we outlined the recent advancements in the role of AnxA6 in mineralization-related diseases and the potential mechanisms of AnxA6 under normal and mineralization-related pathological conditions. AnxA6 could promote ECM mineralization for bone regeneration in the manner described previously. Therefore, AnxA6 may be a potential osteogenic target for ECM mineralization.

Macrophage Function Modulated by tPA Signaling in Mouse Experimental Kidney Disease Models

Macrophage infiltration and accumulation is a hallmark of chronic kidney disease. Tissue plasminogen activator (tPA) is a serine protease regulating the homeostasis of blood coagulation, fibrinolysis, and matrix degradation, and has been shown to act as a cytokine to trigger various receptor-mediated intracellular signal pathways, modulating macrophage function in response to kidney injury. In this review, we discuss the current understanding of tPA-modulated macrophage function and underlying signaling mechanisms during kidney fibrosis and inflammation.

Bioinformatics and computational analyses of kidney stone modulatory proteins lead to solid experimental evidence and therapeutic potential

In recent biomedical research, bioinformatics and computational analyses have played essential roles for examining experimental findings and database information. Several bioinformatic tools have been developed and made publicly available for analyzing protein sequence, structure, functional motif/domain, and interactions network. Such properties are very helpful to define biochemical and functional roles of the protein(s) of interest. During the past few decades, bioinformatics and computational biotechnology have been widely applied to kidney stone research. This review summarizes commonly used tools and evidence of bioinformatics and computational biotechnology applied to kidney stone disease (KSD) with special emphasis on analyses of the stone modulatory proteins that play critical roles in kidney stone formation. Such analyses lead to solid experimental evidence to demonstrate mechanisms underlying their stone modulatory activities. The findings obtained from such analyses may also lead to better understanding of KSD pathogenesis and to further development of new therapeutic and preventive strategies.