Antagonistic regulation of ROMK by long and kidney-specific WNK1 isoforms.
WNK kinases are serine-threonine kinases with an atypical placement of the catalytic lysine. Intronic deletions with increased expression of a ubiquitous long WNK1 transcript cause pseudohypoaldosteronism type 2 (PHA II), characterized by hypertension and hyperkalemia. Here, we report that long WNK1 inhibited ROMK1 by stimulating its endocytosis. Inhibition of ROMK by long WNK1 was synergistic with, but not dependent on, WNK4. A smaller transcript of WNK1 lacking the N-terminal 1-437 amino acids is expressed highly in the kidney. Whether expression of the KS-WNK1 (kidney-specific, KS) is altered in PHA II is not known. We found that KS-WNK1 did not inhibit ROMK1 but reversed the inhibition of ROMK1 caused by long WNK1. Consistent with the lack of inhibition by KS-WNK1, we found that amino acids 1-491 of the long WNK1 were sufficient for inhibiting ROMK. Dietary K(+) restriction decreases ROMK abundance in the renal cortical-collecting ducts by stimulating endocytosis, an adaptative response important for conservation of K(+) during K(+) deficiency. We found that K(+) restriction in rats increased whole-kidney transcript of long WNK1 while decreasing that of KS-WNK1. Thus, KS-WNK1 is a physiological antagonist of long WNK1. Hyperkalemia in PHA II patients with PHA II mutations may be caused, at least partially, by increased expression of long WNK1 with or without decreased expression of KS-WNK1.
Lazrak
Ahmed
A
Department of Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390-8856, USA.
Liu
Zhen
Z
Huang
Chou-Long
CL
D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D002966:Clathrin / Q000378:metabolism; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D034281:Dynamins / Q000378:metabolism; D004594:Electrophysiology; D004705:Endocytosis; D005091:Exons; D005260:Female; D005786:Gene Expression Regulation; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D047908:Intracellular Signaling Peptides and Proteins; D007668:Kidney / Q000378:metabolism; D008297:Male; D015778:Minor Histocompatibility Antigens; D008954:Models, Biological; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000737:chemistry / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying / Q000502:physiology*; D020033:Protein Isoforms; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis* / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014162:Transfection; D000076204:WNK Lysine-Deficient Protein Kinase 1
D002966:Clathrin; D047908:Intracellular Signaling Peptides and Proteins; C086989:KCNJ1 protein, human; C510692:Kcnj1 protein, rat; D015778:Minor Histocompatibility Antigens; D024661:Potassium Channels, Inwardly Rectifying; D020033:Protein Isoforms; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D049452:Green Fluorescent Proteins; D004247:DNA; C499025:Wnk4 protein, rat; D017346:Protein Serine-Threonine Kinases; D000076204:WNK Lysine-Deficient Protein Kinase 1; C498743:WNK1 protein, human; C433806:WNK4 protein, human; C410410:Wnk1 protein, rat; D034281:Dynamins; D011188:Potassium