title: Inhibition of prostasin expression by TGF-beta1 in renal epithelial cells.
abstract: BACKGROUND
  Prostasin has been shown to be involved in the regulation of sodium handling in the kidney. TGF-beta1 has been demonstrated to suppress alphaENaC expression and sodium uptake. Therefore, we hypothesized that TGF-beta1 may regulate prostasin expression to modulate sodium reabsorption in the kidney.
  
  
  METHODS
  To determine if TGF-beta1 has an effect on prostasin expression, we isolated 2.9 kb of the rat prostasin promoter, and measured its transcriptional activity with a luciferase assay in mouse cortical collecting duct cell line (M-1). The effect of TGF-beta1 on the mRNA and protein abundance of prostasin, and amiloride-sensitive (22)Na uptake was determined.
  
  
  RESULTS
  Treatment of M-1 cells with 20 ng/mL of TGF-beta1 for 24 hours significantly decreased the promoter activity by 50 +/- 1%, and the inhibitory effect was dose dependent over the range of 0.1 to 20 ng/mL. We identified a 50 bp region (-410 to -360) containing c-Rel-like sequence in prostasin promoter that is responsible for the TGF-beta1-mediated inhibition, and found that TGF-beta1 increases IkappaBalpha expression in M-1 cells. TGF-beta1 reduced endogenous prostasin mRNA and protein expression in M-1 cells by 50 +/- 12% and 44 +/- 12%, respectively, and the amiloride-sensitive (22)Na uptake by 35.9 +/- 4.8%.
  
  
  CONCLUSIONS
  Our findings indicate the possibility that TGF-beta1 transcriptionally inhibits prostasin expression by the induction of IkappaBalpha and the subsequent inhibition of NF-kappaB/Rel activity in M-1 cells, and also suggest the possibility that TGF-beta1 might inhibit sodium reabsorption through a reduction in prostasin expression and subsequent inhibition of ENaC activity.
authors.affiliation: Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Kumamoto, Japan.
authors.forename: Do Gia
authors.initials: DG
authors.lastname: Tuyen
authors.forename: Kenichiro
authors.initials: K
authors.lastname: Kitamura
authors.forename: Masataka
authors.initials: M
authors.lastname: Adachi
authors.forename: Taku
authors.initials: T
authors.lastname: Miyoshi
authors.forename: Naoki
authors.initials: N
authors.lastname: Wakida
authors.forename: Junko
authors.initials: J
authors.lastname: Nagano
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nonoguchi
authors.forename: Kimio
authors.initials: K
authors.lastname: Tomita
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D017136:Ion Transport / Q000187:drug effects; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012697:Serine Endopeptidases / Q000235:genetics* / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D053773:Transforming Growth Factor beta1; D000099271:Prostasin
chemical_list: D000584:Amiloride; D018076:DNA, Complementary; D012333:RNA, Messenger; D011994:Recombinant Proteins; D012697:Serine Endopeptidases; D012964:Sodium; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D000099271:Prostasin; C508961:Tgfb1 protein, mouse; C508962:Tgfb1 protein, rat