DEXAMETHASONE RAPIDLY INDUCES A NOVEL RAS SUPERFAMILY MEMBER-RELATED GENE IN ATT-SO CELLS

Differential display was used to identify a new Ras superfamily gene ( Dexras1) induced by dexamethasone (Dex) in AtT-20 cells. Treatment of AtT-20 cells with Dex for 30 min resulted in increased mRNA for Dexras 1; the highest concentrations appeared after 2 h of treatment, The gen e was also identified in mouse heart, brain, liver, and kidney and fur thermore was induced in these tissues after Dex treatment, The deduced protein shows regions of homology characteristic of members of the Ra s superfamily of small GTPases, Highest homology (36% identity, 57% po sitives) was found with human Rap-ab, followed closely by a number of other Ras subfamily members, suggesting that Dexras1 is probably a mem ber of the Ras subfamily of GTPases (members include Ras and Rap). Dex ras1 is the first Ras superfamily member identified that is induced in response to steroids. The function of this gene is unknown; however, its wide distribution and rapid induction by Dex suggests the possibil ity of a role in glucocorticoid action in a variety of tissues.