Format

Send to

Choose Destination
Sci Rep. 2015 Dec 17;5:18311. doi: 10.1038/srep18311.

Autophagic degradation of aquaporin-2 is an early event in hypokalemia-induced nephrogenic diabetes insipidus.

Author information

1
Department of Pediatrics, Faculty of Medicine, Thammasat University Klong Luang, Pathumthani, 12120, Thailand.
2
Department of Physiology, Faculty of Medicine Siriraj Hospital, Mahidol University Bangkok, 10700, Thailand.
3
Systems Biology Center, Research Affairs, Faculty of Medicine, Chulalongkorn University 1873 Rama 4 Road, Pathumwan, Bangkok, 10330, Thailand.
4
Department of Pathology, Faculty of Medicine Siriraj Hospital, Mahidol University Bangkok, 10700, Thailand.
5
National Institute of Diabetes and Digestive and Kidney, Bethesda MD 20892, United States.
6
Department of Electrical &Computer Engineering and Department of Computer Science, Western Michigan University Kalamazoo, 49008, United States.
7
Department of Chemistry, National Cheng Kung University, Tainan City, 701, Taiwan.
8
Department of Biomedicine and Center for Interactions of Proteins in Epithelial Transport, Aarhus University, Aarhus, 8000, Denmark.
9
Epithelial Systems Biology Laboratory, National Heart, Lung, and Blood Institute, Bethesda MD 20892, United States.

Abstract

Hypokalemia (low serum potassium level) is a common electrolyte imbalance that can cause a defect in urinary concentrating ability, i.e., nephrogenic diabetes insipidus (NDI), but the molecular mechanism is unknown. We employed proteomic analysis of inner medullary collecting ducts (IMCD) from rats fed with a potassium-free diet for 1 day. IMCD protein quantification was performed by mass spectrometry using a label-free methodology. A total of 131 proteins, including the water channel AQP2, exhibited significant changes in abundance, most of which were decreased. Bioinformatic analysis revealed that many of the down-regulated proteins were associated with the biological processes of generation of precursor metabolites and energy, actin cytoskeleton organization, and cell-cell adhesion. Targeted LC-MS/MS and immunoblotting studies further confirmed the down regulation of 18 selected proteins. Electron microscopy showed autophagosomes/autophagolysosomes in the IMCD cells of rats deprived of potassium for only 1 day. An increased number of autophagosomes was also confirmed by immunofluorescence, demonstrating co-localization of LC3 and Lamp1 with AQP2 and several other down-regulated proteins in IMCD cells. AQP2 was also detected in autophagosomes in IMCD cells of potassium-deprived rats by immunogold electron microscopy. Thus, enhanced autophagic degradation of proteins, most notably including AQP2, is an early event in hypokalemia-induced NDI.

PMID:
26674602
PMCID:
PMC4682130
DOI:
10.1038/srep18311
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Nature Publishing Group Icon for PubMed Central
Loading ...
Support Center