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Abstract: FR-PO620

SNX27, Interacting with AQP2 in a PDZ-Dependent Manner, Regulates the Stability of AQP2 Protein

Session Information

Category: Fluid and Electrolytes

  • 901 Fluid and Electrolytes: Basic

Authors

  • Choi, Hyo-Jung, Kyungpook National University, Daegu, Korea (the Republic of)
  • Jang, Hyo-Ju, Kyungpook National University, Daegu, Korea (the Republic of)
  • Park, Eui-Jung, Kyungpook National University, Daegu, Korea (the Republic of)
  • Jung, Hyun Jun, University of Maryland School of Medicine, Baltimore, Maryland, United States
  • Park, Hye-Jeong, Kyungpook National University, Daegu, Korea (the Republic of)
  • Kwon, Tae-Hwan, Kyungpook National University, Daegu, Korea (the Republic of)
Background

Sorting nexin 27 (SNX27), a PDZ domain-containing protein, is known to cooperate with a retromer complex, regulating the trafficking and stability of membrane proteins. The carboxyl-terminus of aquaporin-2 (AQP2c) has the class I PDZ-interacting motif (X-T/S-X-Φ), however, interaction between SNX27 and AQP2 has not been studied. We aimed to examine the interaction of SNX27 for the regulation of AQP2.

Methods

GST-SNX27 constructs [SNX27-Full Length, Δ(PX+FERM), ΔFERM, ΔPDZ, and Δ(PDZ+PX)] were generated, and the purified proteins were incubated with His-tagged AQP2c protein in vitro. Coimmunoprecipitation (Co-IP) assay was performed using rat kidney inner medullary collecting duct (IMCD) tubule suspension. Immunoblotting and immunolabeling were carried out in SNX27 siRNA-transfected mpkCCD cells. Autophagy was examined using autophagosome marker (mRFP-GFP-LC3).

Results

Co-IP and GST pull-down assays demonstrated that PDZ domain of SNX27 directly interacted with AQP2c. Immunocytochemistry of HeLa cells co-transfected with Flag-SNX27 and HA-AQP2 revealed that AQP2 co-localized with the intact SNX27, suggesting that a PDZ domain of SNX27 is required for the interaction with AQP2. Removal of PDZ domain (SNX27-ΔPDZ) induced accumulation of AQP2 at the perinuclear region in HeLa cells. Immunohistochemistry revealed colocalization of SNX27 and AQP2 at both cytoplasm and plasma membrane in rat kidney CD cells. Subcellular redistribution of SNX27 under dDAVP stimulation/withdrawal was almost identical with AQP2 in rat kidney. Cell surface biotinylation assay showed that dDAVP-induced AQP2 translocation to the apical plasma membrane of mpkCCD was not affected by SNX27 knockdown. Immunoblotting revealed that dDAVP-induced AQP2 up-regulation was significantly blunted by SNX27 knockdown, whereas qRT-PCR showed no change of AQP2 mRNA expression. During dDAVP withdrawal, decrease of AQP2 expression in mpkCCD cells with SNX27 knockdown was significantly attenuated by chloroquine, but not by MG132. Moreover, SNX27 knockdown remarkably induced autophagy in mpkCCD cells expressing LC3.

Conclusion

SNX27, directly interacts with AQP2 in a PDZ-dependent manner, is likely to regulate stability of AQP2 protein. It acts as a component of the AQP2 controlling machinery, at least in part, through regulation of autophagy-lysosomal degradation of AQP2.

Funding

  • Government Support - Non-U.S.