Comparison of WNK4 and WNK1 kinase and inhibiting activities.
WNK kinases are novel serine/threonine protein kinases. Mutations in two members of the WNK family, WNK1 and WNK4, cause familial hyperkalemic hypertension. These kinases regulate ion transport across diverse epithelia; WNK4 reduces activity of the Na-Cl cotransporter activity and the potassium channel, ROMK, by reducing their appearance at the plasma membrane. We examined the kinase activity of WNK1 and WNK4 in vitro. A glutathione S-transferase (GST) fusion protein of the WNK1 kinse domain phosphorylated itself and a substrate protein, as reported previously. A longer construct, containing the autoinhibitory domain, did not. A GST WNK4 kinase domain construct demonstrated no kinase activity, in vitro or in HEK 293 cells. WNK4 constructs that included a region homologous to the autoinhibitory domain of WNK1 inhibited WNK1 kinase activity. Inhibition by a short WNK4 segment, WNK4 (444-518), was greater than inhibition by WNK4 (444-563). Together, these results suggest that WNK4 must be activated by currently unknown factors to exhibit kinase activity and that WNK4 contains an inhibitory domain that can inhibit the kinase activity of WNK1.
Wang
Zhaohong
Z
Division of Nephrology and Hypertension, Department of Medicine, Oregon Health and Science University, Portland, OR 97239, USA.
Yang
Chao-Ling
CL
Ellison
David H
DH
D000595:Amino Acid Sequence; D000818:Animals; D015778:Minor Histocompatibility Antigens; D008969:Molecular Sequence Data; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000502:physiology*; D011506:Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000502:physiology*; D051381:Rats; D017386:Sequence Homology, Amino Acid; D000076204:WNK Lysine-Deficient Protein Kinase 1
D015778:Minor Histocompatibility Antigens; D011506:Proteins; C499025:Wnk4 protein, rat; D017346:Protein Serine-Threonine Kinases; D000076204:WNK Lysine-Deficient Protein Kinase 1; C410410:Wnk1 protein, rat