Serine 269 phosphorylated aquaporin-2 is targeted to the apical membrane of collecting duct principal cells.
Trafficking of the water channel aquaporin-2 to the apical plasma membrane of the collecting duct is mediated by arginine vasopressin, rendering the cell permeable to water. We recently identified a novel form of aquaporin-2 that is phosphorylated at serine-269 (pS269-AQP2). Using antibodies specific for this form of the water channel, we detected rat and mouse pS269-AQP2 in the connecting tubule and throughout the collecting duct system. Using confocal immunofluorescence microscopy with organelle-specific markers and immunogold electron microscopy, we found that pS269-AQP2 was found only on the apical plasma membrane of principal cells. In vasopressin-deficient Brattleboro rats, pS269-AQP2 was undetectable but dramatically increased in abundance after these rats were treated with [deamino-Cys-1, d-Arg-8]vasopressin (dDAVP). This increase occurred only at the apical plasma membrane, even after long-term dDAVP treatment. Following dDAVP there was a time-dependent redistribution of total aquaporin-2 from predominantly intracellular vesicles to the apical plasma membrane, clathrin-coated vesicles, early endosomal compartments, and lysosomes. However, pS269-AQP2 was found only on the apical plasma membrane at any time. Our results show that S269 phosphorylated aquaporin-2 is exclusively associated with the apical plasma membrane, where it escapes endocytosis to remain at the cell surface.
The Water and Salt Research Center, Institute of Anatomy, University of Aarhus, Aarhus, Denmark.
Hanne B
HB
Moeller
Mark A
MA
Knepper
Robert A
RA
Fenton
D000818:Animals; D051399:Aquaporin 2 / Q000378:metabolism* / Q000648:ultrastructure; D002462:Cell Membrane / Q000378:metabolism* / Q000648:ultrastructure; D022163:Clathrin-Coated Vesicles / Q000378:metabolism; D003894:Deamino Arginine Vasopressin / Q000378:metabolism / Q000494:pharmacology; D011992:Endosomes / Q000378:metabolism / Q000648:ultrastructure; D007150:Immunohistochemistry; D007685:Kidney Tubules, Collecting / Q000166:cytology* / Q000378:metabolism* / Q000648:ultrastructure; D008247:Lysosomes / Q000378:metabolism / Q000648:ultrastructure; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009195:Peroxidase / Q000276:immunology / Q000378:metabolism; D010766:Phosphorylation; D051381:Rats; D011910:Rats, Brattleboro; D017208:Rats, Wistar; D012680:Sensitivity and Specificity; D012694:Serine / Q000378:metabolism*; D013997:Time Factors
D051399:Aquaporin 2; D012694:Serine; D009195:Peroxidase; D003894:Deamino Arginine Vasopressin