title: Dexamethasone increases the phosphorylation of nephrin in cultured podocytes.
abstract: BACKGROUND
  We reported that nephrin is phosphorylated at Y1204 and Y1228 under normal conditions and that the phosphorylation is decreased in puromycin nephrosis and in human minimal change nephrosis. These results indicate that the phosphorylation of nephrin is important for maintaining normal podocyte function. However, little is known about the regulation of nephrin phosphorylation. Here, we investigated whether glucocorticoid, a drug used to treat glomerular diseases with proteinuria, might affect the phosphorylation of nephrin.
  
  
  METHODS
  Human cultured podocytes transiently expressing human nephrin were treated with dexamethasone (Dex), and the phosphorylation of nephrin was determined by immunoblot with the anti-pY1228 antibody.
  
  
  RESULTS
  Dex treatment for 24 h increased the phosphorylation of nephrin; this increased phosphorylation was inhibited by the glucocorticoid receptor antagonist but not by the mineral corticoid receptor antagonist. A shorter incubation time (30 min) did not increase the phosphorylation, and actinomycin D and cycloheximide treatments abolished the increased phosphorylation. The activation of Src-family kinases was correlated with nephrin phosphorylation, both of which were abolished by small interfering RNA (siRNA) treatment for serum/glucocorticoid-induced kinase 1 (SGK1).
  
  
  CONCLUSIONS
  These results clarify a novel action of glucocorticoid on nephrin phosphorylation through SGK1. Glucocorticoid treatment for human glomerulonephritis may exert its function by regulating the phosphorylation of nephrin.
authors.affiliation: Department of Medicine, Kidney Center, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjyuku-ku, Tokyo, 162-8666, Japan.|Department of Nephrology, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo, Tokyo, 113-8519, Japan.
authors.forename: Teiko
authors.initials: T
authors.lastname: Ohashi
authors.affiliation: Department of Medicine, Kidney Center, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjyuku-ku, Tokyo, 162-8666, Japan. kuchida@kc.twmu.ac.jp.
authors.forename: Keiko
authors.initials: K
authors.lastname: Uchida
authors.affiliation: Department of Nephrology, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo, Tokyo, 113-8519, Japan.
authors.forename: Shinichi
authors.initials: S
authors.lastname: Uchida
authors.affiliation: Department of Nephrology, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo, Tokyo, 113-8519, Japan.
authors.forename: Sei
authors.initials: S
authors.lastname: Sasaki
authors.affiliation: Department of Medicine, Kidney Center, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjyuku-ku, Tokyo, 162-8666, Japan.
authors.forename: Kosaku
authors.initials: K
authors.lastname: Nitta
mesh_terms: D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology*; D006801:Humans; D017874:Immediate-Early Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D015735:Mifepristone / Q000494:pharmacology; D010766:Phosphorylation; D050199:Podocytes / Q000187:drug effects* / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011965:Receptors, Glucocorticoid / Q000037:antagonists & inhibitors; D019061:src-Family Kinases / Q000378:metabolism; D000099184:Serum-Glucocorticoid Regulated Kinases
chemical_list: D003513:Cycloheximide; D003609:Dactinomycin; D003907:Dexamethasone; D017874:Immediate-Early Proteins; D008565:Membrane Proteins; D015735:Mifepristone; D017346:Protein Serine-Threonine Kinases; D011965:Receptors, Glucocorticoid; D019061:src-Family Kinases; D000099184:Serum-Glucocorticoid Regulated Kinases; C113267:nephrin