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Changing S261, including constitutive phosphorylation, enhances AQP2 ubiquitination and internalization
Author(s) -
Deen Peter MT,
Tamma Grazia,
Stoffels Monique,
Hoffert Jason D,
Konings Irene BM,
Knepper Mark A
Publication year - 2009
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.23.1_supplement.998.3
Subject(s) - aquaporin 2 , internalization , apical membrane , microbiology and biotechnology , phosphorylation , ubiquitin , chemistry , intracellular , vesicle , aquaporin , chromosomal translocation , biology , biochemistry , water channel , membrane , cell , mechanical engineering , gene , engineering , inlet
For renal water reabsorption AVP‐induced phosphorylation of AQP2 at S256 (p256) is needed for its translocation to the apical membrane. Also, phorbol esters (TPA) activation of PKC induces AQP2 ubiquitination at K270, its internalization and lysosomal degradation. But AQP2 can also be phosphorylated at S261 (pS261), which role was studied here. In transfected MDCK cells, forskolin (F) redistributed AQP2 from vesicles to the apical membrane, which was reversed with subsequent F/TPA treatment. As in vivo for AVP, F increased pS256 and decreased pS261 AQP2, which was reversed with F/TPA. For all treatments, AQP2‐S256A and AQP2‐S261A/D always localized to intracellular vesicles, AQP2‐S256D localized in the apical membrane with/without F and internalized with F/TPA, but the changes in pS261 and pS256 were similar to AQP2. AQP2‐S261A/D were more ubiquitinated than wt‐AQP2 and AQP2‐S261D‐K270R, which cannot be ubiquitinated, always localized in the apical membrane. AQP2‐S256D‐S261D, however, localized as AQP2‐S256D. AQP2‐S256D‐Ub always localized to vesicles and was constitutively‐phosphorylated at S261. Thus, as in vivo with AVP, AQP2 is reciprocally changed in S256 and S261 phosphorylation with F and F/TPA, independent of their localization. pS256 is needed and sufficient for AQP2 translocation to the apical membrane, but is overruled by constitutive ubiquitination. Changing S261, including constitutive pS261, enhances AQP2 ubiquitination and internalization, but is overruled by constitutive pS256.