Cellulose Acetate Membrane Electrophoresis Based Urinary Proteomics for the Identification of Characteristic Proteins

BACKGROUND

Analysis of urinary proteins using cellulose acetate membrane electrophoresis (CAME) is a useful and challenging method for the recognition of damaged sites in the kidney. However, protein content of each CAME fraction is still not completely understood.

METHODS

In this study, an effective method of protein extraction from each band fractionated by CAME was established, which enabled us to examine the extracted proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and mass spectrometry.

RESULTS

Proteins were extracted from the gel and analyzed by mass spectrometry. In all, 31 proteins were identified, including 20 urinary proteins that were newly identified in the CAME-based analysis.

CONCLUSION

This methodology was useful for identifying the proteins responsible for creating unique bands on CAME in a urine sample of a patient with drug-induced interstitial nephritis. These findings provide in-depth characterization of urinary protein contents in each CAME fraction.

Analysis of an expanded width of albumin fraction by cellulose acetate membrane electrophoresis in IgA nephropathy urine before treatment

Cellulose acetate membrane electrophoresis with colloidal silver stain re-vealed that the width of the albumin fraction in IgA nephropathy (IgAN) urine before treatment was significantly expanded. This phenomenon was not shown in IgAN urine after treatment or in non-IgAN urine. There was a reverse correlation between the width of the albumin fraction and the albumin con-centration in IgAN urine. By immuno-fixation, Tamm-Horsfall protein (THP) was located in the same position as the albumin band in IgAN urine before treatment; however, in the urine of a healthy subject it was located in the same position as alpha(1)-globulin. By ELISA, the THP-albumin complex concentration in IgAN urine before treatment was significantly higher than in the other two diseases. The width of the albumin fraction and the sodium ion concentra-tion of the urine were significantly correlated. The THP/albumin ratio in IgAN urine before treatment was significantly higher than in the other two groups. This suggests that the characteristic expanded width of albumin found by immunofixation indicates a THP-albumin complex, and that the sodium concentration of urine is involved in the formation of this complex.

Cellulose acetate membrane electrophoresis in the analysis of urinary proteins in patients with tubulointerstitial nephritis

Urinary proteins from 14 patients with tubulointerstitial nephritis were analyzed by cellulose acetate membrane electrophoresis. Urinary total protein concentrations were measured, and urinary 15 proteins (prealbumin, albumin, alpha(1)-microglobulin, alpha(1)-antitrypsin, alpha(2)-macroglobulin, haptoglobin, retinol binding protein, transferrin, beta(2)-microglobulin, IgA, IgG, kappa- and lambda-light chains, cystatin C, and lysozyme) were identified by the use of a rapid and highly sensitive colloidal silver staining reagent suited for use with cellulose acetate membranes, as reported previously by Matsuda et al. (J Clin Lab Anal 15:171-174, 2001; Clin Chem47:763-766, 2001) and Hiratsuka et al. (J Clin Lab Anal 10:403-406, 1996). We also analyzed urinary total protein concentration and urinary protein fractions according to the presence of acute or nonacute interstitial nephritis. In addition, the relationship between urinary protein fraction and complications of interstitial nephritis was analyzed. The goal of this work was to find a useful index for the diagnosis of tubulointerstitial nephritis.