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Published online December 26, 2006
doi:10.1083/jcb.200605093
The Journal of Cell Biology, Vol. 176, No. 1, 89-100
The Rockefeller University Press, 0021-9525 $30.00
© 2006 Zagórska et al.
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Regulation of activity and localization of the WNK1 protein kinase by hyperosmotic stress



Anna Zagórska1, Eulalia Pozo-Guisado1, Jérôme Boudeau1, Alberto C. Vitari1, Fatema H. Rafiqi1, Jacob Thastrup1, Maria Deak1, David G. Campbell1, Nick A. Morrice1, Alan R. Prescott2, and Dario R. Alessi1

1 Medical Research Council Protein Phosphorylation Unit and 2 Division of Cell Biology and Immunology, School of Life Sciences, Medical Sciences Institute/Wellcome Trust Biocentre Complex, University of Dundee, Dundee DD1 5EH, Scotland, UK

Correspondence to Dario R. Alessi: d.r.alessi{at}dundee.ac.uk

Mutations within the WNK1 (with-no-K[Lys] kinase-1) gene cause Gordon's hypertension syndrome. Little is known about how WNK1 is regulated. We demonstrate that WNK1 is rapidly activated and phosphorylated at multiple residues after exposure of cells to hyperosmotic conditions and that activation is mediated by the phosphorylation of its T-loop Ser382 residue, possibly triggered by a transautophosphorylation reaction. Activation of WNK1 coincides with the phosphorylation and activation of two WNK1 substrates, namely, the protein kinases STE20/SPS1-related proline alanine–rich kinase (SPAK) and oxidative stress response kinase-1 (OSR1). Small interfering RNA depletion of WNK1 impairs SPAK/OSR1 activity and phosphorylation of residues targeted by WNK1. Hyperosmotic stress induces rapid redistribution of WNK1 from the cytosol to vesicular structures that may comprise trans-Golgi network (TGN)/recycling endosomes, as they display rapid movement, colocalize with clathrin, adaptor protein complex 1 (AP-1), and TGN46, but not the AP-2 plasma membrane–coated pit marker nor the endosomal markers EEA1, Hrs, and LAMP1. Mutational analysis suggests that the WNK1 C-terminal noncatalytic domain mediates vesicle localization. Our observations shed light on the mechanism by which WNK1 is regulated by hyperosmotic stress.

A. Zagórska, E. Pozo-Guisado, J. Boudeau, A.C. Vitari, and F.H. Rafiqi contributed equally to this paper.

Abbreviations used in this paper: CCT, conserved C-terminal; ERK, extracellular signal–regulated kinase; OSR1, oxidative stress response kinase-1; PP1{gamma}, protein phosphatase-1{gamma}; SPAK, STE20/SPS1-related proline alanine–rich kinase; WNK, with-no-K(Lys) kinase.


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