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Article
GRP78/BIP is Involved in Ouabain-Induced Endocytosis of the Na/K-ATPase in LLC-PK1 Cells
Pharmaceutical Science and Research
  • Riad Kesiry
  • Jiang Liu, Marshall University
Document Type
Article
Publication Date
9-1-2005
Abstract
We have demonstrated that ouabain causes dose- and time-dependent decreases both in 86Rb+ uptake and plasmalemmal Na/K-ATPase content of LLC-PK1 cells, which is related to ouabain-induced endocytosis of plasmalemmal Na/K-ATPase in LLC-PK1 cells through a clathrin-dependent mechanism. GRP78/BiP is a resident protein of the endoplasmic reticulum (ER) and acts as a molecular chaperone. Recently, several studies have shown that GRP78/BiP is also expressed on the cell surface and forms heterogeneous, high molecular weight complexes with other proteins. To identify the proteins that are possibly involved in ouabain-induced endocytosis of the Na/K-ATPase in LLC-PK1 cells, we separated and identified endosomal proteins by 2D gel electrophoresis and MS/MS from both control and ouabain-treated LLC-PK1 cells. GRP78/BiP was identified by MS/MS as one of the several up-regulated proteins and confirmed by Western Blot. By using a cell surface protein biotinylation technique to isolate the cell surface membrane proteins, we found that GRP78/BiP is also expressed on the cell surface of LLC-PK1 cells, and surface-expressed GRP78/BiP is down regulated in a time-dependent manner in response to ouabain. By comparing the cellular redistributions, our data suggest that both the Na/K-ATPase a -1 subunit and GRP78/BiP follow the same redistribution pattern in response to ouabain.
Comments

The version of record is available from the publisher at https://www.bioscience.org/2005/v10/af/1680/fulltext.htm. Copyright © 2005 Frontiers in Bioscience. All rights reserved.

Citation Information
Kesiry, R., & Liu, J. (2005). GRP78/BIP is involved in ouabain-induced endocytosis of the Na/K-ATPase in LLC-PK1 cells. Frontiers In Bioscience, 10, 2045-2055.