Atg7-dependent canonical autophagy regulates the degradation of aquaporin 2 in prolonged hypokalemia

Wan Young Kim, Sun Ah Nam, Arum Choi, Yu Mi Kim, Sang Hee Park, Hong Lim Kim, Hyang Kim, Ki Hwan Han, Chul Woo Yang, Myung Shik Lee, Yong Kyun Kim, Jin Kim

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8 Scopus citations

Abstract

Prolonged hypokalemia induces a decrease of urinary concentrating ability via down-regulation of aquaporin 2 (AQP2); however, the precise mechanisms remain unknown. To investigate the role of autophagy in the degradation of AQP2, we generated the principal cell-specific Atg7 deletion (Atg7 Δpc ) mice. In hypokalemic Atg7-floxed (Atg7 f/f ) mice, huge irregular shaped LC3-positive autophagic vacuoles accumulated mainly in inner medullary collecting duct (IMCD) cells. Total- and pS261-AQP2 were redistributed from apical and subapical domains into these vacuoles, which were not co-localized with RAB9. However, in the IMCD cells of hypokalemic Atg7 Δpc mice, these canonical autophagic vacuoles were markedly reduced, whereas numerous small regular shaped LC3-negative/RAB9-positive non-canonical autophagic vacuoles were observed along with diffusely distributed total- and pS261-AQP2 in the cytoplasm. The immunoreactivity of pS256-AQP2 in the apical membrane of IMCD cells was markedly decreased, and no redistribution was observed in both hypokalemic Atg7 f/f and Atg7 Δpc mice. These findings suggest that AQP2 down regulation in hypokalemia was induced by reduced phosphorylation of AQP2, resulting in a reduction of apical plasma labeling of pS256-AQP2 and degradation of total- and pS261-AQP2 via an LC3/ATG7-dependent canonical autophagy pathway.

Original languageEnglish
Article number3021
JournalScientific Reports
Volume9
Issue number1
DOIs
StatePublished - 1 Dec 2019

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