Overexpression of human WNK1 increases paracellular chloride permeability and phosphorylation of claudin-4 in MDCKII cells.
Pseudohypoaldosteronism type II (PHAII), an autosomal dominant disorder characterized by hypertension, hyperkalemia, and hyperchloremic acidosis, is reportedly due to mutations in WNK1 and WNK4 kinase genes. However, the pathogenesis of the disease remains unknown. Mutations in the WNK1 gene are the deletions in the first intron, which reportedly increases WNK1 mRNA expression. Thus, we generated WNK1 over-expressing stable cell lines using MDCKII cells to model the distal nephron of PHAII patients. Using these cell lines, we investigated whether increased WNK1 expression might affect paracellular chloride permeability and claudin phosphorylation, since we previously observed an increase in both with a disease-causing mutant WNK4. WNK1 expression in MDCKII cells increased chloride permeability two to threefold. Co-expression of wild-type WNK4 did not further increase WNK1-enhanced chloride permeability. WNK1 expression also induced phosphorylation of endogenous claudin-4 in MDCKII cells, as well as over-expressed claudin-4. Combined, these results suggest that increased WNK1 expression has the same effect on chloride permeability and claudin phosphorylation as the mutant WNK4. Thus, increased chloride shunt may be involved in the pathogenesis of PHAII caused by WNK1 mutations.
Ohta
Akihito
A
Department of Nephrology, Graduate School of Medicine, Tokyo Medical and Dental University, Tokyo 113-8519, Japan.
Yang
Sung-Sen
SS
Rai
Tatemitsu
T
Chiga
Motoko
M
Sasaki
Sei
S
Uchida
Shinichi
S
D000818:Animals; D002460:Cell Line; D002712:Chlorides / Q000737:chemistry / Q000378:metabolism; D062506:Claudin-4; D018076:DNA, Complementary / Q000378:metabolism; D004285:Dogs; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D007438:Introns; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000737:chemistry; D015778:Minor Histocompatibility Antigens; D009154:Mutation; D009399:Nephrons / Q000378:metabolism; D010539:Permeability; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D013912:Threonine / Q000737:chemistry; D000076204:WNK Lysine-Deficient Protein Kinase 1
C568157:CLDN4 protein, human; D002712:Chlorides; D062506:Claudin-4; D018076:DNA, Complementary; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D015778:Minor Histocompatibility Antigens; D012333:RNA, Messenger; D013912:Threonine; D017346:Protein Serine-Threonine Kinases; D000076204:WNK Lysine-Deficient Protein Kinase 1; C498743:WNK1 protein, human