Stone former urine proteome demonstrates a cationic shift in protein distribution compared to normal.
Many urine proteins are found in calcium oxalate stones, yet decades of research have failed to define the role of urine proteins in stone formation. This urine proteomic study compares the relative amounts of abundant urine proteins between idiopathic calcium oxalate stone forming and non-stone forming (normal) cohorts to identify differences that might correlate with disease. Random mid-morning urine samples were collected following informed consent from 25 stone formers and 14 normal individuals. Proteins were isolated from urine using ultrafiltration. Urine proteomes for each sample were characterized using label-free spectral counting mass spectrometry, so that urine protein relative abundances could be compared between the two populations. A total of 407 unique proteins were identified with the 38 predominant proteins accounting for >82% of all sample spectral counts. The most highly abundant proteins were equivalent in stone formers and normals, though significant differences were observed in a few moderate abundance proteins (immunoglobulins, transferrin, and epidermal growth factor), accounting for 13 and 10% of the spectral counts, respectively. These proteins contributed to a cationic shift in protein distribution in stone formers compared to normals (22% vs. 18%, p = 0.04). Our data showing only small differences in moderate abundance proteins suggest that no single protein controls stone formation. Observed increases in immunoglobulins and transferrin suggest increased inflammatory activity in stone formers, but cannot distinguish cause from effect in stone formation. The observed cationic shift in protein distribution would diminish protein charge stabilization, which could lead to protein aggregation and increased risk for crystal aggregation.
Division of Nephrology, Department of Medicine, Medical College of Wisconsin, 9200 W Wisconsin Avenue, Milwaukee, WI, 53226, USA.
Ann M
AM
Kolbach-Mandel
Mandel International Stone and Molecular Analysis Center, Zablocki VA Medical Center, 5000 W. National Avenue, Milwaukee, WI, 53295, USA.|Division of Nephrology, Department of Medicine, Medical College of Wisconsin, 9200 W Wisconsin Avenue, Milwaukee, WI, 53226, USA.
Neil S
NS
Mandel
Department of Biomedical Engineering, Cardiovascular Center, Medical College of Wisconsin, 9200 W Wisconsin Avenue, Milwaukee, WI, 53226, USA.
Brian R
BR
Hoffmann
Division of Nephrology, Department of Medicine, Medical College of Wisconsin, 9200 W Wisconsin Avenue, Milwaukee, WI, 53226, USA.
Jack G
JG
Kleinman
Nephrology Section, Consultant Care Division, Zablocki Department of Veterans Affairs Medical Center, 5000 W. National Avenue (111K), Milwaukee, WI, 53295, USA. jwesson@mcw.edu.|Division of Nephrology, Department of Medicine, Medical College of Wisconsin, 9200 W Wisconsin Avenue, Milwaukee, WI, 53226, USA. jwesson@mcw.edu.
Jeffrey A
http://orcid.org/0000-0002-2181-0323
JA
Wesson
D000328:Adult; D002129:Calcium Oxalate / Q000378:metabolism*; D002412:Cations / Q000378:metabolism*; D019295:Computational Biology; D004815:Epidermal Growth Factor / Q000378:metabolism; D005260:Female; D006801:Humans; D007136:Immunoglobulins / Q000378:metabolism; D008297:Male; D013058:Mass Spectrometry / Q000379:methods; D008875:Middle Aged; D066263:Protein Aggregation, Pathological / Q000473:pathology; D020543:Proteome / Q000378:metabolism*; D040901:Proteomics / Q000379:methods; D014168:Transferrin / Q000378:metabolism; D014462:Ultrafiltration; D014545:Urinary Calculi / Q000473:pathology*; D014556:Urine / Q000737:chemistry*
D002412:Cations; D007136:Immunoglobulins; D020543:Proteome; D014168:Transferrin; D002129:Calcium Oxalate; D004815:Epidermal Growth Factor
Calcium oxalate; Kidney calculi; Osteopontin; Proteomics; Urine