Regulation of Aquaporin-2 Trafficking
Principal cells lining renal collecting ducts control the fine-tuning of body water homeostasis by regulating water reabsorption through the water channels aquaporin-2 (AQP2), aquaporin-3 (AQP3), and aquaporin-4 (AQP4). While the localization of AQP2 is s
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Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AQP2 Trafficking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 Role of Phosphorylation in AQP2 Trafficking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Compartmentalization of cAMP Signaling in Renal Principal Cells: A Role for AKAPs and PDEs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 The Involvement of Cytoskeletal Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 Role of Calcium in AQP2 Trafficking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Regulation of Endocytosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Phosphorylation-Independent Translocation of AQP2 to the Plasma Membrane . . . . . . . . 5 Dysfunction of AQP2 Trafficking Causes Nephrogenic Diabetes Insipidus (NDI) . . . . . . 6 Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Abstract Principal cells lining renal collecting ducts control the fine-tuning of body water homeostasis by regulating water reabsorption through the water channels aquaporin-2 (AQP2), aquaporin-3 (AQP3), and aquaporin-4 (AQP4). While the localization of AQP2 is subject to regulation by arginine-vasopressin (AVP), AQP3 and AQP4 are constitutively expressed in the basolateral plasma membrane. AVP adjusts the amount of AQP2 in the plasma membrane by triggering its redistribution from intracellular vesicles into the plasma membrane. This permits water entry into the cells and water exit through AQP3 and AQP4. The translocation of AQP2 is initiated by an increase in cAMP following V2R activation through AVP. The AVP-induced rise in cAMP activates protein kinase A (PKA), which in turn phosphorylates AQP2, and thereby triggers the redistribution of AQP2. Several proteins participating in the control of cAMP-dependent AQP2 trafficking have been identified; for example, A kinase anchoring proteins (AKAPs) tethering PKA E. Klussmann (¬) Leibniz-Institut f¨ur Molekulare Pharmakologie, Robert-R¨ossle-Street 10, Campus Berlin-Buch, D-13125 Berlin, Germany [email protected] E. Beitz (ed.), Aquaporins, Handbook of Experimental Pharmacology 190, c Springer-Verlag Berlin Heidelberg 2009
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to cellular compartments; phosphodiesterases (PDEs) regulating the local cAMP level; cytoskeletal components such as F-actin and microtubules; small GTPases of the Rho family controlling cytoskeletal dynamics; motor proteins transporting AQP2-bearing vesicles to and from the plasma
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