Regulation of the Water Channel Aquaporin-2 via 14-3-3θ and -ζ

• Published in: The Journal of biological chemistry 2016-01, Vol.291 (5), p.2469-2484
• Main Authors: Moeller, Hanne B., Slengerik-Hansen, Joachim, Aroankins, Takwa, Assentoft, Mette, MacAulay, Nanna, Moestrup, Soeren K., Bhalla, Vivek, Fenton, Robert A.
• Format: Article
• Language: English
• Subjects: 14-3-3 Proteins - metabolism; Animals; aquaporin; Aquaporin 2 - metabolism; Biotinylation; Cell Biology; Deamino Arginine Vasopressin - chemistry; Gene Expression Regulation; Glutathione Transferase - metabolism; HEK293 Cells; Humans; intracellular trafficking; kidney; Kidney - metabolism; Kidney Tubules - metabolism; Mice; Phosphorylation; post-translational modification (PTM); Protein Processing, Post-Translational; Protein Structure, Tertiary; Protein Transport; RNA, Messenger - metabolism; RNA, Small Interfering - metabolism; Surface Plasmon Resonance; ubiquitin; Ubiquitin - metabolism; Vasopressin; Vasopressins - metabolism; water channel
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M115.691121

The 14-3-3 family of proteins are multifunctional proteins that interact with many of their cellular targets in a phosphorylation-dependent manner. Here, we determined that 14-3-3 proteins interact with phosphorylated forms of the water channel aquaporin-2 (AQP2) and modulate its function. With the exception of σ, all 14-3-3 isoforms were abundantly expressed in mouse kidney and mouse kidney collecting duct cells (mpkCCD14). Long-term treatment of mpkCCD14 cells with the type 2 vasopressin receptor agonist dDAVP increased mRNA and protein levels of AQP2 alongside 14-3-3β and -ζ, whereas levels of 14-3-3η and -θ were decreased. Co-immunoprecipitation (co-IP) studies in mpkCCD14 cells uncovered an AQP2/14-3-3 interaction that was modulated by acute dDAVP treatment. Additional co-IP studies in HEK293 cells determined that AQP2 interacts selectively with 14-3-3ζ and -θ. Use of phosphatase inhibitors in mpkCCD14 cells, co-IP with phosphorylation deficient forms of AQP2 expressed in HEK293 cells, or surface plasmon resonance studies determined that the AQP2/14-3-3 interaction was modulated by phosphorylation of AQP2 at various sites in its carboxyl terminus, with Ser-256 phosphorylation critical for the interactions. shRNA-mediated knockdown of 14-3-3ζ in mpkCCD14 cells resulted in increased AQP2 ubiquitylation, decreased AQP2 protein half-life, and reduced AQP2 levels. In contrast, knockdown of 14-3-3θ resulted in increased AQP2 half-life and increased AQP2 levels. In conclusion, this study demonstrates phosphorylation-dependent interactions of AQP2 with 14-3-3θ and -ζ. These interactions play divergent roles in modulating AQP2 trafficking, phosphorylation, ubiquitylation, and degradation.