[Comprehensive analysis of urinary proteins for identification of renal disease markers]

Urine can be obtained noninvasively and relatively easily to provide a large sample and it is an important source of biomarker discovery in kidney diseases. Today, urinary albumin screening is not only useful for detecting early kidney diseases, but also recognized as a risk factor for cardiovascular diseases. We have shown different kinds of post-translational modification of urinary albumin in patients with glomerulonephritis, such as high- and low-molecular mass forms of albumin and highly carbonylated albumin. These characteristic molecular forms of albumin are not detected in serum samples obtained from the same patients or urine of healthy subjects, reflecting the kidney diseases processes. Furthermore, measuring the levels of albumin and other urinary proteins enables comprehensive kidney examination. The urinary protein profile using cellulose acetate membrane electrophoresis coupled with colloidal silver staining allows us to construct urinary protein profiles. Basically, urinary protein patterns in patients with glomerulonephritis show 5 fractions, the same as the serum pattern; however, characteristic bands of cathode β and anode β fractions, reflecting β2-microglobulin and retinol binding protein, appear in patients with tubular dysfunction. This method is useful to diagnose damaged portions of the kidney, and it provides supportive data for renal biopsy. Most recently, exosome-derived proteins are considered as a new marker source which reflects in-situ alterations in the urology and renal diseases. Different forms of electrophoresis reveal slight alterations in the protein profile on the analysis of urinary proteins including exosomes. This report introduces the electrophoresis-based urinary proteome results generated by our research group.