Aldosterone induces ras methylation in A6 epithelia.
Aldosterone increases Na(+) reabsorption by renal epithelial cells: the acute actions (<4 h) appear to be promoted by protein methylation. This paper describes the relationship between protein methylation and aldosterone's action and describes aldosterone-mediated targets for methylation in cultured renal cells (A6). Aldosterone increases protein methylation from 7.90 +/- 0.60 to 20.1 +/- 0.80 methyl ester cpm/microg protein. Aldosterone stimulates protein methylation by increasing methyltransferase activity from 14.0 +/- 0.64 in aldosterone-depleted cells to 31.8 +/- 2.60 methyl ester cpm/microg protein per hour in aldosterone-treated cells. Three known methyltransferase inhibitors reduce the aldosterone-induced increase in methyltransferase activity. One of these inhibitors, the isoprenyl-cysteine methyltransferase-specific inhibitor, S-trans, trans-farnesylthiosalicylic acid, completely blocks aldosterone-induced protein methylation and also aldosterone-induced short-circuit current. Aldosterone induces protein methylation in two molecular weight ranges: near 90 kDa and around 20 kDa. The lower molecular weight range is the weight of small G proteins, and aldosterone does increase both Ras protein 1.6-fold and Ras methylation almost 12-fold. Also, Ras antisense oligonucleotides reduce the activity of Na(+) channels by about fivefold. We conclude that 1) protein methylation is essential for aldosterone-induced increases in Na(+) transport; 2) one target for methylation is p21(ras); and 3) inhibition of Ras expression or Ras methylation inhibits Na(+) channel activity.
Center for Cell and Molecular Signaling, Department of Physiology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
N F
NF
Al-Baldawi
J D
JD
Stockand
O K
OK
Al-Khalili
G
G
Yue
D C
DC
Eaton
D000450:Aldosterone / Q000494:pharmacology*; D000818:Animals; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism; D007684:Kidney Tubules / Q000187:drug effects / Q000378:metabolism; D008745:Methylation; D011496:Protein Methyltransferases / Q000187:drug effects* / Q000378:metabolism; D015222:Sodium Channels / Q000187:drug effects* / Q000378:metabolism; D018631:ras Proteins / Q000187:drug effects* / Q000378:metabolism
D015222:Sodium Channels; D000450:Aldosterone; D011496:Protein Methyltransferases; D018631:ras Proteins