Abstract: TH-PO387

Endocytosis and Intracellular Trafficking of AQP2 Is Regulated by the Notch Signaling Pathway

Session Information

Category: Cell Biology

  • 201 Cell Signaling, Oxidative Stress

Authors

  • Huang, Huihui, Massachusetts General Hospital, Wayland, Massachusetts, United States
  • Su, Limin, Massachusetts General Hospital, Wayland, Massachusetts, United States
  • Paunescu, Teodor G., Massachusetts General Hospital, Wayland, Massachusetts, United States
  • Yang, Baoxue, Peking University, Beijing, China
  • Lu, Hua Ann Jenny, Massachusetts General Hospital, Wayland, Massachusetts, United States
Background

The Notch signaling pathway plays important roles in development and pathological processes in multiple tissues, including the kidney. A role of Notch signaling in regulating trafficking of nephrin in podocytes and of monocarboxylic acid transporter 1 in brain endothelial cells has recently been reported, implicating an emerging function for Notch in protein trafficking. Aquaporin-2 (AQP2) is a water channel that mediates water reabsorption in the collecting ducts (CDs) of the kidney.It plays a predominant role in regulating water balance in mammals. In this study, we investigate the function of Notch signaling in AQP2 trafficking and urinary concentration. Our data show that inhibiting Notch signaling either by Notch inhibitors DAPT and LY-411575, or by siRNA knock down in cultured cells increases AQP2 membrane accumulation. A similar increase in AQP2 membrane accumulation is observed in CD principal cells (PCs) in cultured mouse kidney slices treated with DAPT or LY-411575. Notch inhibition causes AQP2 accumulation on the apical membrane in CDs from both cortex and medulla. Membrane accumulation of AQP2 induced by Notch inhibition does not affect AQP2 expression, and is independent of AQP2 phosphorylation. Further analysis reveals that Notch inhibition reduces the endocytosis of AQP2 without affecting the overall exocytosis, and Notch inhibition negatively impacts F-actin polymerization. The role of Notch signaling in water transport was next investigated in vivo. DAPT treatment of mice attenuates the polyuria and increases urinary concentration in lithium treated mice by promoting apical membrane accumulation of AQP2 in CD PCs. Further supporting this idea, increased membrane accumulation of AQP2 was observed in the hemizygous PC-specific rbpj flox/+/aqp2 cre mice (recombination signal binding protein for immunoglobulin kappa J (RBPJ)-deficient mice). We further challenged the hemizygous rbpj flox/+/aqp2 cre mice with lithium. We found that the hemizygous rbpj flox/+/aqp2 cre mice are resistant to lithium induced nephrogenic diabetes insipidus. Our studies collectively show that AQP2 trafficking is regulated by the Notch signaling pathway both in vitro and in vivo, therefore uncovering a novel role of Notch signaling in modulating water homeostasis through regulating AQP2 trafficking.