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.
Moeller
Hanne B
HB
The Water and Salt Research Center, Institute of Anatomy, University of Aarhus, Aarhus, Denmark.
Knepper
Mark A
MA
Fenton
Robert A
RA
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