BackgroundInformation | I.TESTPRINCIPLE TheUPSTATE®colorimetricSTAR(SignalTransductionAssayReaction)ELISAkitisasolidphasesandwichenzymelinkedimmunosorbentassaythatprovidesafast,sensitivemethodtodetectspecificlevelsofsignalingtargetsinwholecellextracts.ThePRAS40plateiscoatedwithaspecificmousemonoclonalPRAS40captureantibodyonthemicrowellsofthe96-wellclearplate.SamplelysateorthestandardincludedinthekitareincubatedinthemicrowellsallowingPRAS40antigentobecapturedintheplatewells.Theplateisthenwashedtoremoveanyunboundnon-specificmaterial.Thewellsarethenincubatedwithaspecificrabbitanti-phospho-PRAS40(Thr246)antibodytodetectthecapturedPRAS40ontheplatewellthatisphosphorylatedonThr246.TheunbounddetectionantibodyiswashedawayfollowedbyincubationwithanHRP-conjugatedanti-rabbitantibody.AftertheadditionofTMBsubstrateandstopsolutiontheabsorbanceismeasuredat450nmusingaplatereader.Thisallowsforasensitiveenzymaticdetectionofthesample. Theentireassaytakeslessthan5hourstocompletewithminimalhands-ontime.Manyofthereagentsaresuppliedinready-touseformulationsforeaseofuse.ThekitalsoincludesastandardthatisrunasbothapositivecontrolandtogenerateastandardcurveforphosphorylatedPRAS40(Thr246)measurement.
II.PRAS40BACKGROUND PRAS40(ProlineRichAktSubstrate,40kDa),alsoknownasAKT1S1,isaubiquitouslyexpressproteinthatisphosphorylatedonresidueThr246viathePI3K/Aktpathway.ItwasoriginallydiscoveredasanAktsubstrateasithastheputativeAktphosphorylationmotifofRxRxxpS/pT2.Thisphosphorylationallowsittobind14-3-3andRaptorofthemTORcomplexmTORC1.PRAS40isknowntobindtoandregulatemTORC1(mTOR,Raptor,mLST8)kinasesactivitythatisactivatedbyinsulindownstreamofPI3KandAktandsubsequentlyphosphorylatesp70S6Kand4EBP1.PRAS40isknowntohaveaputativeTOSmotif(FVMDE)thatallowsitbindtoRaptorofmTORC1intheabsenceofinsulin.ItisthoughtthatthroughitbindingtotheRaptor,PRAS40inhibitsthekinaseactivityofmTORC1bypreventingtobindtoitssubstratessuchasp70S6Kand4EBP1. |