Abelson interactor-1 (ABI-1) interacts with MRL adaptor protein MIG-10 and is required in guided cell migrations and process outgrowth in C. elegans

摘要

Directedcellmigrationandprocessoutgrowtharevitaltoproperdevelopmentofmanymetazoantissues.Theseprocessesaredependentonreorganizationoftheactincytoskeletoninresponsetoexternalguidancecues.Duringdevelopmentofthenervoussystem,theMIG-10/RIAM/Lamellipodin(MRL)signalingproteinsarethoughttotransmitpositionalinformationfromsurfaceguidancecuestotheactinpolymerizationmachinery,andthustopromotepolarizedoutgrowthofaxons.InemC.elegans/em,mutationsintheMRLfamilymembergeneemmig-10/emresultinanimalsthathavedefectsinaxonguidance,neuronalmigration,andtheoutgrowthoftheprocessesorlsquo;canalsrsquo;oftheexcretorycell,whichisrequiredforosmoregulationintheworm.Inaddition,emmig-10/emmutantanimalshaverecentlybeenshowntohavedefectsinclusteringofvesiclesatthesynapse./ppid="sp0045"TodetermineadditionalmolecularpartnersofMIG-10,weconductedayeasttwo-hybridscreenusingisoformMIG-10AasbaitandisolatedAbelson-interactorprotein-1(ABI-1).ABI-1,adownstreamtargetofAblnon-receptortyrosinekinase,isamemberoftheWAVEregulatorycomplex(WRC)involvedintheinitiationofactinpolymerization.Furtheranalysisusingaco-immunoprecipitationsystemconfirmedtheinteractionofMIG-10andABI-1andshowedthatitrequirestheSH3domainofABI-1.Singlemutantsforemmig-10/emandemabi-1/emdisplayedsimilarphenotypesofincompletemigrationoftheALMneuronsandtruncatedoutgrowthoftheexcretorycellcanals,suggestingthattheABI-1/MIG-10interactionisrelevanteminvivo/em.CellautonomousexpressionofMIG-10isoformsrescuedboththeneuronalmigrationandthecanaloutgrowthdefects,showingthatMIG-10functionsautonomouslyintheALMneuronsandtheexcretorycell.TheseresultssuggestthatMIG-10andABI-1interactphysicallytopromotecellmigrationandprocessoutgrowtheminvivo/em./ppid="sp0050"Intheexcretorycanal,ABI-1isthoughttoactdownstreamofUNC-53/NAV2,linkingthislargescaffoldingproteintoactinpolymerizationduringexcretorycanaloutgrowth.emabi-1/em(emRNAi/em)enhancedtheexcretorycanaltruncationobservedinemmig-10/emmutants,whiledoublemutantanalysisbetweenemunc-53/emandemmig-10/emshowednoincreasedtruncationoftheposteriorcanalbeyondthatobservedinemmig-10/emmutants.Morphologicalanalysisofemmig-10/emandemunc-53/emmutantsshowedthatthesegenesregulatecanaldiameteraswellasitslength,suggestingthatdefectivelumenformationmaybelinkedtotheabilityoftheexcretorycanaltogrowoutlongitudinally.Takentogether,ourresultssuggestthatMIG-10,UNC-53,andABI-1actsequentiallytomediateexcretorycellprocessoutgrowth./p/div