| To test whether Nedd 4 2 , SGK 1 , SGK 3 and protein kinase B regulate EAAT 1 , cRNA encoding EAAT 1 was injected into Xenopus oocytes with or without additional injection of wild type Nedd 4 2 , constitutively active S422DSGK1 , inactive K127NSGK1 , wild type SGK 3 and / or constitutively active T308D , S473DPKB . ^^^ Site directed mutagenesis of the SGK 1 phosphorylation sites in the Nedd 4 2 protein ( S382A , S468ANedd4 2 ) and in the EAAT 1 protein ( T482AEAAT1 , T482DEAAT1 ) significantly blunts the effect of S422DSGK1 . ^^^ |