An essential role for Rab27a GTPase in eosinophil exocytosis

[摘要] Eosinophildegranulationhasbeenimplicatedininflammatoryprocessesassociatedwithallergicasthma.Rab27a,aRab‐relatedGTPase,isaregulatoryintracellularsignalingmoleculeexpressedinhumaneosinophils.WepostulatedthatRab27aregulateseosinophildegranulation.WeinvestigatedtheroleofRab27aineosinophildegranulationwithinthecontextofairwayinflammation.Rab27aexpressionandlocalizationineosinophilswereinvestigatedbyusingsubcellularfractionationcombinedwithWesternblotanalysis,andtheresultswereconfirmedbyimmunofluorescenceanalysisofRab27aandthegranulemembranemarkerCD63.TodeterminethefunctionofeosinophilRab27a,weusedAshenmice,astrainofRab27a‐deficientanimals.AsheneosinophilsweretestedfordegranulationinresponsetoPAFandcalciumionophorebymeasuringreleasedEPXactivity.AirwayEPXreleasewasalsodeterminedbyintratrachealinjectionofeosinophilsintomicelackingEPX.Rab27aimmunoreactivitycolocalizedwitheosinophilcrystalloidgranules,asdeterminedbysubcellularfractionationandimmunofluorescenceanalysis.PAFinducedeosinophildegranulationincorrelationwithredistributionofRab27a+structures,someofwhichcolocalizedwithCD63+crystalloidgranulesatthecellmembrane.EosinophilsfrommicehadsignificantlyreducedEPXreleasecomparedwithnormalWTeosinophils,bothinvitroandinvivo.Inmousemodels,AshenmicedemonstratedreducedEPXreleaseinBALfluid.ThesefindingssuggestthatRab27ahasakeyroleineosinophildegranulation.Furthermore,thesefindingshaveimplicationsforRab27a‐dependenteosinophildegranulationinairwayinflammation...

[学科分类] 生理学

[关键词] allergic asthma;degranulation;subcellular fractionation;IL‐5 transgenic mice;hE2 transgenic mice;Ashen mice