Intracellular trafficking pathway of albumin in glomerular epithelial cells.

Abstract

The intracellular trafficking pathway of albumin in podocytes remains controversial. We therefore analysed albumin endocytosis through caveolae, subsequent transcytosis, and exocytosis. In Western blot and immunofluorescence analysis in vitro, methyl-beta-cyclodextrin (MBCD) treatment significantly decreased the expression of caveolin-1 and albumin in cultured human podocytes after incubation with albumin; additionally, MBCD interfered with albumin endocytosis through caveolae in the experiment using Transwell plates. In the immunofluorescence analysis, albumin was incubated with cultured human podocytes, and colocalisation analysis with organelles and cytoskeletons in the podocytes showed that albumin particles colocalised with caveolin-1 and Fc-receptor but not clathrin in endocytosis, colocalised with actin cytoskeleton but not microtubules in transcytosis, and colocalised with early endosomes and lysosomes but not proteasome, endoplasmic reticulum, or Golgi apparatus. In the electron microscopic analysis of podocytes in nephrotic syndrome model mice, gold-labelled albumin was shown as endocytosis, transcytosis, and exocytosis with caveolae. These results indicate the intracellular trafficking of albumin through podocytes. Albumin enters through caveolae with the Fc-receptor, moves along actin, and reaches the early endosome, where some of them are sorted for lysosomal degradation, and others are directly transported outside the cells through exocytosis. This intracellular pathway may be a new aetiological hypothesis for albuminuria.

• Authors: Takahito Moriyama, Fumio Hasegawa, Yoei Miyabe, Kenichi Akiyama, Kazunori Karasawa, Keiko Uchida, Kosaku Nitta
• Journal: Biochemical and biophysical research communications (Biochem Biophys Res Commun) Vol. 574 Pg. 97-103 (10 15 2021) ISSN: 1090-2104 [Electronic] United States
• PMID: 34450430 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2021 Elsevier Inc. All rights reserved.

Chemical References

• Serum Albumin, Human

Topics

• Animals
• Epithelial Cells (metabolism)
• Humans
• Kidney Glomerulus (metabolism)
• Male
• Mice
• Mice, Inbred C57BL
• Serum Albumin, Human (metabolism)