BackgroundInformation | I.TESTPRINCIPLETheUPSTATE®colorimetricSTAR(SignalTransductionAssayReaction)ELISAkitisasolidphasesandwichenzymelinkedimmunosorbentassaythatprovidesafast,sensitivemethodtodetectspecificlevelsofsignalingtargetsinwholecellextracts.TheGSK-3βplateiscoatedwithaspecificmousemonoclonalGSK-3&betacaptureantibodyonthemicrowellsofthe96-wellclearplate.SamplelysateorthestandardincludedinthekitareincubatedinthemicrowellsallowingGSK-3βantigentobecapturedintheplatewells.Theplateisthenwashedtoremoveanynon-boundunspecificmaterial.Thewellsarethenincubatedwithaspecificrabbitanti-GSK-3βantibodytodetectthecapturedphosphor-GSK-3β(Ser9)ontheplatewell.TheunbounddetectionantibodyiswashedawayfollowedbyincubationwithanHRP-conjugatedanti-rabbitantibody.Thisallowsforasensitiveenzymaticdetectionofthesample.AftertheadditionofTMBsubstrateandstopsolutiontheabsorbanceismeasuredat450nmusingaplatereader.Theentireassaytakeslessthan5hourstocompletewithminimalhands-ontime.Manyofthereagentsaresuppliedinready-touseformulationsforeaseofuse.Thekitalsoincludesastandardthatisrunasbothapositivecontrolandtodevelopastandardlineofdetection.
II.GSK-3βBACKGROUNDGlycogenSynthaseKinase-3differsfrommostserine/threoninekinasesinthatitisactiveintheabsenceoftheactionofsignalingpathways.Whenitbecomesphosphorylated,theproteinbecomesinactive.Therearetwoisoformsthatexist,GSK-3αandGSK-3β.ThefunctionofGSK-3istophosphorylateGlycogenSynthaseandtherebyinactivateit.InsulinactionstimulatesthePI3KinasepathwaythatresultsintheactivationofAkt.AktphosphorylatesGSK-3,therebyinactivatingit.GlycogenSynthase,GSK-3"sdownstreamsubstrate,isthenrapidlydephosphorylatedandactivated.OtherGSK-3substratesincludeJun(oninhibitorysites),andeIF2B.DetectionofGSK-3"sphosphorylationstatusoftheAktsite(Ser21)onGSK-3issuitableforsurrogateassaysoftheactivationstateofthepathway. |