Changes in protein profiles during course of experimental glomerulonephritis

Better characterization of the molecular mechanisms underlying glomerular cell proliferation may improve our understanding of the pathogenesis of glomerulonephritis and yield disease-specific markers. We used two-dimensional gel electrophoresis (2DE) and mass spectrometry (MS) to generate expression profiles of glomerular proteins in the course of anti-Thy-1 nephritis. Glomeruli were isolated from Wistar rats by sieving, and proteins were separated by 2DE. In preliminary studies using normal rats, we identified known glomerular proteins from microfilaments [tropomyosin (Tm)] and intermediate filaments (vimentin and lamin A), proteins involved in assembly (alpha-actinin-4, F-actin capping protein) and membrane cytoskeletal linking (ezrin), as well as several enzymes (protein disulfide isomerase, ATP synthase, and aldehyde dehydrogenase). Comparison of glomerular protein abundance between normal rats and rats in the early phase of anti-Thy-1 nephritis yielded 28 differentially expressed protein spots. MS analysis identified 16 differentially expressed proteins including Tm. Altered Tm abundance in the course of anti-Thy-1 nephritis was confirmed, and specific isoforms were characterized by Western blotting. We demonstrated a complex change in Tm isoform abundance in the course of anti-Thy-1 nephritis. The early mesangiolytic phase of the disease was characterized by decreased abundance of low-molecular-weight isoforms Tm5a/5b and increased abundance of high-molecular-weight isoforms Tm6, Tm1, Tm2, and Tm3. The late proliferative phase of the disease was associated with increased abundance of isoforms Tm5a/5b, Tm6, and Tm1 and decreased abundance of Tm3. Isoforms Tm4 and Tm5 remained unchanged in the course of this model of experimental glomerulonephritis. Characterization of Tm isoform abundance in the course of clinical glomerulonephritis may identify disease-specific markers.