Kidney Injury Molecule-1 Enhances Endocytosis of Albumin in Renal Proximal Tubular Cells

J Cell Physiol. 2016 Apr;231(4):896-907. doi: 10.1002/jcp.25181. Epub 2015 Sep 9.


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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Cell Communication
  • Cell Compartmentation
  • Cells, Cultured
  • Clathrin / metabolism
  • Endocytosis*
  • Epithelial Cells / metabolism
  • Fluorescein-5-isothiocyanate / analogs & derivatives*
  • Fluorescein-5-isothiocyanate / metabolism
  • Hepatitis A Virus Cellular Receptor 1 / metabolism*
  • Humans
  • Kidney Tubules, Proximal / cytology*
  • Kidney Tubules, Proximal / metabolism*
  • Lysosomes / metabolism
  • Male
  • Mice, Inbred C57BL
  • Rats
  • Serum Albumin, Bovine / metabolism*
  • Transforming Growth Factor beta1 / metabolism


  • Clathrin
  • HAVCR1 protein, human
  • Hepatitis A Virus Cellular Receptor 1
  • Transforming Growth Factor beta1
  • fluorescein isothiocyanate bovine serum albumin
  • Serum Albumin, Bovine
  • Fluorescein-5-isothiocyanate