Hormones, Growth Factors, Cell Signaling, Cell Biology and StructureAnnexin II Is Present on Renal Epithelial Cells and Binds Calcium Oxalate Monohydrate CrystalsKumar, Vivek*; Farell, Gerard*; Deganello, Sergio†; Lieske, John C.* Author Information *Division of Nephrology, Department of Internal Medicine, Mayo Clinic and Foundation, Rochester, Minnesota; and †Department C.F.T.A., University of Palermo, Palermo, Italy. Correspondence to Dr. John C. Lieske, Division of Nephrology, Department of Internal Medicine, Mayo Clinic and Foundation, 200 1st St SW, Rochester, MN 55905. Phone: 507-284-2064; Fax: 507-266-9315; Accepted October 21, 2002 Received July 11, 2002 Journal of the American Society of Nephrology 14(2):p 289-297, February 2003. | DOI: 10.1097/01.ASN.0000046030.24938.0A Buy Metrics Abstract ABSTRACT. Attachment of newly formed crystals to renal epithelial cells appears to be a critical step in the development of kidney stones. The current study was undertaken to identify potential calcium oxalate monohydrate (COM) crystal-binding proteins on the surface of renal tubular cells. Apical membranes were prepared from confluent monolayers of renal epithelial cells (MDCKI line), and COM crystal affinity was used to isolate crystal-binding proteins that were then subjected to electrophoresis and electroblotting. Microsequencing of the most prominent COM crystal-binding protein (Mr of 37 kD) identified it as annexin II (Ax-II). When exposed proteins on the surface of intact monolayers were biotinylated and then isolated using streptavidin agarose beads, Ax-II was detected, suggesting that at least a portion is exposed on the apical cell surface. Ax-II was not completely extracted by 0.1 M Na2CO3, suggesting that at least a portion of cellular Ax-II is an intrinsic membrane-bound protein. Using confocal immunofluorescence microscopy, Ax-II was visualized together with Caveolin-1 (Cav-1) on the apical membrane of intact MDCKI cells. Cells pretreated with a monoclonal anti-Ax-II antibody bound significantly fewer COM crystals, whereas anti-LDL receptor antibody did not decrease COM binding, further suggesting a functional role for Ax-II during adhesion of crystals to intact cells. These results suggest that Ax-II avidly binds COM crystals and is present on the apical surface of MDCKI cells. Therefore, in the intact nephron, Ax-II could mediate adhesion of COM crystals to cells, and altered exposure of Ax-II on the surface of renal tubular cells could promote crystal retention and possibly kidney stone formation. E-mail: [email protected] Copyright © 2003 The Authors. Published by Wolters Kluwer Health, Inc. All rights reserved.