Rac-1isasmallG-proteinintheRhofamilythatregulatescellmotilityinresponsetoextracellularsignals.Severalchangesincytoskeletalstructureandotheraspectsofcellstructureareinvolvedincellmotility.Rac-1isactivatedbyGEFfactors,andrepressedbyGAPs.GEFsareguaninenucleotideexchangefactors,includingTrioandVav.Sos-1isinvolvedinRassignalingandalsoactsasaGEFforRactotransducesignalsbetweenRasandRac.SWAP-70isaRacGEFthatbindsIP3andtransducessignalsfromtyrosinekinasestoRactomodulatetheCytoskeletonandcausemembraneruffling.GAPsareGTPase-activatingproteins.Racstimulatestheformationofactin-basedstructuressuchasfilopodiaandlamellopodia,whileGAPssuchaschimerinopposetheformationoftheseRacdependentstructures.SeveraldifferentfactorsdownstreamofRacactoncytoskeletalstructureandotheraspectsofcellmotility.Pak1providesadirectlinkfromRactocellmotilitythroughphosphorylationofthemyosinlightchain.Pak1alsophosphorylatesandactivatesLIMkinase,whichphosphorylatescofilinasonetarget.Cofilinstimulatesactindepolymerizationandchangesincellstructure,andphosphorylationofcofilinbyLIMkinaserepressesitsactivity.Inneurons,Racactsthroughtheproteinkinasecdk5andp35tophosphorylateanddownregulatePak1,increasingneuronalmigration.Rac-1alsointeractswithseveralotherfactorstoregulateavarietyofprocesses.InteractionofPor1withRac-1isinvolvedinmembraneruffling.WAVEisamemberoftheWASPfamilyofproteinsthatregulateactinorganizationandthatisinvolvedinRacsignalingtocausemembraneruffling.InteractionofRac-1withMEKK1integratesRacsignalingwithpathwayssignalingthroughmapkinases.

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