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Missorting to late endosome/lysosomes due to increased phosphorylation by protein kinase C and mono‐ubiquitination of the Aquaporin‐2 mutant E258K might explain its role in dominant Nephrogenic Diabetes Insipidus
Author(s) -
Deen Peter MT,
Savelkoul Paul JM,
Kamsteeg ErikJan,
Hendriks Giel,
Konings Irene BM,
van der Sluijs Peter
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.6.a956-a
Subject(s) - aquaporin 2 , nephrogenic diabetes insipidus , phosphorylation , microbiology and biotechnology , endosome , forskolin , apical membrane , endocytosis , chemistry , aquaporin , ubiquitin , biology , biochemistry , vasopressin , water channel , endocrinology , receptor , membrane , intracellular , mechanical engineering , engineering , inlet , gene
Vasopressin regulates water homeostasis by phosphorylation Aquaporin‐2 (AQP2) at S256 and translocating them from vesicles to the apical membrane. AQP2‐E258K causes dominant Nephrogenic Diabetes Insipidus ( NDI). To address the molecular mechanism for dominant NDI, AQP2‐E258K was studied in polarized MDCK. AQP2‐E258K mainly co‐localized with the late endosomes(LE)/lysosomes(Lys). Upon co‐expression, wild‐type (wt) AQP2 interacted with AQP2‐E258K and localized to LE/Lys, independent of forskolin stimulation, while wt‐AQP2 alone translocated from vesicles to the apical membrane. Orthophosphate labeling revealed that forskolin increased phosphorylation of wt‐AQP2 and AQP2‐E258K, but not AQP2‐S256A, indicating that the E258K mutation does not interfere with the AQP2‐S256 phosphorylation. In contrast to wt‐AQP2, but consistent with the introduced PKC consensus site, AQP2‐E258K was phosphorylated by phorbol esters. Besides the 29 kDa band, however, a band of 38 kDa was observed for AQP2‐E258K only, which, consistent with the mass increase, was mono‐ubiquitinated AQP2‐E258K. Mono‐ubiquitination induces endocytosis of membrane proteins and targets them to LE/Lys. As the AQP2‐E258K NDI patients show a shortened period of urine concentration following dDAVP administration compared to central DI patients, increased endocytoses and LE/Lys targeting of wt‐AQP2/AQP2‐E258K complexes due to AQP2‐E258K mono‐ubiquitination provides an explanation for dominant NDI in these patients.