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Complement regulatory proteins in glomerular diseases
1Division of Nephrology and Endocrinology, University of Tokyo School of Medicine, Tokyo, Japan. mnangaku-tky@umin.ac.jp
Insights
Complement regulatory proteins protect the glomerulus from injury in glomerulonephritis. Therapeutic strategies like protein administration and overexpression show promise for treating kidney disease.
Area of Science:
- Nephrology
- Immunology
- Molecular Biology
Background:
- Complement activation is a key driver in glomerulonephritis pathogenesis, causing tissue damage via chemotactic factors and C5b-9 insertion.
- Complement regulatory proteins (CRPs) like DAF, MCP, CR1, and CD59 control complement activation.
- These proteins, particularly membrane-bound CRPs, are abundant in the glomerulus and protect against immune-mediated renal injury.
Purpose of the Study:
- To review the role of complement regulatory proteins in glomerulonephritis.
- To discuss the mechanisms of action and regulation of CRPs in the glomerulus.
- To explore novel therapeutic strategies for glomerulonephritis based on CRPs.
Main Methods:
- Review of scientific literature on complement activation and regulation in glomerulonephritis.
- Analysis of the expression and function of CRPs (DAF, MCP, CR1, CD59) in glomerular cells.
- Evaluation of studies using cultured cells and animal models to assess CRP protective roles.
Main Results:
- DAF, MCP, and CR1 inactivate C3/C5 convertase, while CD59 inhibits C5b-9 formation.
- All three resident glomerular cells express DAF, MCP, and CD59; podocytes uniquely express CR1.
- Altered CRP expression is observed in glomerular disorders, and studies indicate their protective function against renal injury.
Conclusions:
- Complement regulatory proteins play a crucial protective role in the glomerulus against immune-mediated injury.
- Therapeutic strategies involving systemic administration of soluble CRPs or local overexpression are promising for glomerulonephritis treatment.
Abstract:
Complement activation plays a critical role in the pathogenesis of many forms of glomerulonephritis. Complement activation leads to tissue injury through various mechanisms including the generation of chemotactic factors and activation of the resident glomerular cells following C5b-9 insertion. Recent advances have disclosed the mechanisms of regulation of complement activation by discovery of a number of complement regulatory proteins. Decay accelerating factor (DAF), membrane cofactor protein (MCP), and complement receptor type 1 (CR1) act by inactivating C3/C5 convertase. They belong to the gene superfamily known as the regulators of complement activation (RCA), and share a common structural motif called a short consensus repeat (SCR). In contrast, CD59 works by inhibiting formation of C5b-9. The glomerulus is particularly well endowed with these membrane-bound complement regulatory proteins. DAF, MCP, and CD59 are ubiquitously expressed by all three resident glomerular cells, while CR1 is localized exclusively in podocytes. Expression of complement regulatory proteins can be changed by many factors including complement attack itself, and their expression levels are affected in various glomerular disorders. Studies utilizing cultured glomerular cells and animal models of glomerular diseases suggest important protective roles of complement regulatory proteins against immune-mediated renal injury. Recent progress in molecular biological techniques has made new therapeutic strategy feasible. Systemic administration of soluble recombinant complement regulatory proteins and local overexpression of complement regulatory proteins are promising therapeutic approaches.