Faculty Collaboration Database

The calcium oxalate crystal growth inhibitor protein produced by mouse kidney cortical cells in culture is osteopontin. J Bone Miner Res 1992 Sep;7(9):1029-36

Date

09/01/1992

Pubmed ID

1414495

DOI

10.1002/jbmr.5650070905

Scopus ID

2-s2.0-0026731914 (requires institutional sign-in at Scopus site)   127 Citations

Abstract

Urine contains proteins that inhibit the growth of calcium oxalate (CaOx) crystals and may prevent the formation of kidney stones. We have identified a potent crystal growth inhibitor in the conditioned media from primary cultures of mouse kidney cortical cells. Conditioned media, incubated with the kidney cells for 6-72 h, was assayed for crystal growth inhibition; inhibitory activity increased 15-fold by 24 h. Inhibitory activity was purified from serum-free media containing proteinase inhibitors using anion-exchange and gel-filtration chromatography. A single band of molecular weight 80,000 daltons was seen after SDS-polyacrylamide gel electrophoresis. The sequence of the N-terminal 21 amino acids of this protein matched that of osteopontin (OP), a phosphoprotein initially isolated from bone matrix. Antisera raised to fusion proteins produced by plasmids containing the N-terminal or C-terminal portions of OP cDNA also cross-reacted with the protein purified from cell culture media on western blots. The effect of the purified protein on the growth of CaOx crystals was measured using a constant composition assay. A 50% inhibition of growth occurred at a protein concentration of 0.85 micrograms/ml, and the dissociation constant of the protein with respect to CaOx crystal was 3.7 x 10(-8) M. The concentration of OP in mouse urine, measured using antibodies raised to the purified protein, was approximately 8 micrograms/ml. We conclude that OP is synthesized by kidney cortical tubule cells and functions as a crystal growth inhibitory protein in urine.

Author List

Worcester EM, Blumenthal SS, Beshensky AM, Lewand DL

Author

Samuel S. Blumenthal MD Professor in the Medicine department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Amino Acid Sequence
Amino Acids
Animals
Calcium Oxalate
Cells, Cultured
Chromatography, Gel
Chromatography, Ion Exchange
Crystallization
Culture Media
Electrophoresis, Polyacrylamide Gel
Kidney Tubules
Mice
Molecular Sequence Data
Molecular Weight
Osteopontin
Sialoglycoproteins