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Kidney Injury Molecule‐1 Enhances Endocytosis of Albumin in Renal Proximal Tubular Cells
Author(s) -
Zhao Xueying,
Jiang Chen,
Olufade Rebecca,
Liu Dong,
Emmett Nerimiah
Publication year - 2016
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.25181
Subject(s) - endocytosis , endosome , microbiology and biotechnology , clathrin , internalization , receptor mediated endocytosis , podocyte , reabsorption , biology , chemistry , kidney , intracellular , receptor , biochemistry , endocrinology , proteinuria
Receptor‐mediated endocytosis plays an important role in albumin reabsorption by renal proximal tubule epithelial cells. Kidney injury molecule‐1 (KIM‐1) is a scavenger receptor that is upregulated on the apical membrane of proximal tubules in proteinuric kidney disease. In this study, we examined the cellular localization and functional role of KIM‐1 in cultured renal tubule epithelial cells (TECs). Confocal immunofluorescence microscopy reveals intracellular and cell surface localization of KIM‐1 in primary renal TECs. Albumin stimulation resulted in a redistribution of KIM‐1 and tight junction protein zonula occludens‐1 in primary TEC monolayer. An increase in albumin internalization was observed in both primary TECs expressing endogenous KIM‐1 and rat kidney cell line (NRK‐52E) overexpressing exogenous KIM‐1. KIM‐1‐induced albumin accumulation was abolished by its specific antibody. Moreover, endocytosed KIM‐1 and its cargo proteins were delivered from endosomes to lysosomes for degradation in a clathrin‐dependent pathway. Supportive evidence includes (1) detection of KIM‐1 in Rab5‐positive early endosomes, Rab7‐positive late endosomes/multivesicular bodies, and LAMP1‐positive lysosomes, (2) colocalization of KIM‐1 and clathrin in the intracellular vesicles, and (3) blockade of KIM‐1‐mediated albumin internalization by chlorpromazine, an inhibitor of clathrin‐dependent endocytosis. KIM‐1 expression was upregulated by albumin but downregulated by transforming growth factor‐β1. Taken together, our data indicate that KIM‐1 increases albumin endocytosis in renal tubule epithelial cells, at least partially via a clathrin‐dependent mechanism. J. Cell. Physiol. 231: 896–907, 2016. © 2015 Wiley Periodicals, Inc.