Modulation of calcium oxalate dihydrate growth by selective crystal-face binding of phosphorylated osteopontin and polyaspartate peptide showing occlusion by sectoral (compositional) zoning.
Calcium oxalate dihydrate (COD) mineral and the urinary protein osteopontin/uropontin (OPN) are commonly found in kidney stones. To investigate the effects of OPN on COD growth, COD crystals were grown with phosphorylated OPN or a polyaspartic acid-rich peptide of OPN (DDLDDDDD, poly-Asp(86-93)). Crystals grown with OPN showed increased dimensions of the {110} prismatic faces attributable to selective inhibition at this crystallographic face. At high concentrations of OPN, elongated crystals with dominant {110} faces were produced, often with intergrown, interpenetrating twin crystals. Poly-Asp(86-93) dose-dependently elongated crystal morphology along the {110} faces in a manner similar to OPN. In crystal growth studies using fluorescently tagged poly-Asp(86-93) followed by imaging of crystal interiors using confocal microscopy, sectoral (compositional) zoning in COD was observed resulting from selective binding and incorporation (occlusion) of peptide exclusively into {110} crystal sectors. Computational modeling of poly-Asp(86-93) adsorption to COD {110} and {101} surfaces also suggests increased stabilization of the COD {110} surface and negligible change to the natively stable {101} surface. Ultrastructural, colloidal-gold immunolocalization of OPN by transmission electron microscopy in human stones confirmed an intracrystalline distribution of OPN. In summary, OPN and its poly-Asp(86-93) sequence similarly affect COD mineral growth; the {110} crystallographic faces become enhanced and dominant attributable to {110} face inhibition by the protein/peptide, and peptides can incorporate into the mineral phase. We, thus, conclude that the poly-Asp(86-93) domain is central to the OPN ability to interact with the {110} faces of COD, where it binds to inhibit crystal growth with subsequent intracrystalline incorporation (occlusion).
Chien
Yung-Ching
YC
Faculty of Dentistry, McGill University, Montreal, Quebec H3A 2B2, Canada.
Masica
David L
DL
Gray
Jeffrey J
JJ
Nguyen
Sarah
S
Vali
Hojatollah
H
McKee
Marc D
MD
D000368:Aged; D002129:Calcium Oxalate / Q000737:chemistry* / Q000378:metabolism; D003460:Crystallization; D003461:Crystallography; D005260:Female; D006801:Humans; D007669:Kidney Calculi / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008968:Molecular Conformation; D053495:Osteopontin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding
D010455:Peptides; D053495:Osteopontin; C017645:polyaspartate; D002129:Calcium Oxalate