SGK3isamemberoftheSGKfamilyandencodesaphosphoproteinwithaPX(phoxhomology)domain.PKD1canphosphorylateandactivateSGK3invitro(1).A10-foldincreaseinPKD1increasesthephosphorylationstatusofSGK3.Whenexpressedinhumanembryonickidneycells,IGF1andperoxidesignificantlyactivateSGK3,andtheactivationcouldbereducedbypreincubationwithinhibitorsofPI3kinase.Ayeast2-hybridscreenfounddirectinteractionbetweenhumanSGK3andGSK3β.SGK3phosphorylatesseveraltargetproteinsandhasaroleinneutralaminoacidtransportandactivationofpotassiumandchloridechannels(2).
5mMMOPS,2.5mMβ-glycerophosphate,5mMMgCl2,1mMEGTA,0.4mMEDTA,0.05mMDTT,2mMATP.IncubateSGK3with0.2mg/mlAkt(PKB)peptidesubstrate(CKRPRAASFAE)and50?M[33P]-ATPat30°Cfor15minutes,thenspotreactiononphosphocellulosepaper,fixin1%phosphoricacid,andassaywithascintillationcounter.
>6monthsat-80°C.
2.Gamper,N.etal:K+channelactivationbyallthreeisoformsofserum-andglucocorticoid-dependentproteinkinaseSGK.Europ.J.Physiol.445:60-66,2002.