Immuneandnon-immunefunctionsofDrosophilahemocytesininfestationandhypoxia.

Abstract

초파리배아에서유래한순환혈구세포는크게3가지종류로나눌수있다.식균작용을하는plasmatocyte과,흑색화작용에관여하는crystalcell과마지막으로병원체캡슐화에관여하는lamellocyte이있다.최근,단세포분석방법을통해기존에알려진종류외에다른여러종류의순환혈구세포의존재가밝혀졌지만그것들의기능은아직많은부분에서연구되지않았다.이번연구에서,나는선천성면역반응쪽으로만연구가활발히진행되고있었던초파리혈구세포의내부산소항상성및대사기능측면에서의연구를진행했다. 첫번째로,초파리애벌레가말벌에감염되는상황에서뇌에서분비된GABA가조혈모세포안으로들어가대사산물로서lamellocyte의분화에사용된다는것을찾아냈다.GABAtransporter를통해안으로들어간GABA는GABAshuntpathway를통해succinate을만들고나아가Hifprotein을안정화시키면서lamellocyte분화를촉진시키는것을발견했다.초파리애벌레가Or49a를통해말벌특유의취기(iridomyrmecin)를먼거리에서부터감지해GABA를분비함으로써미리면역체계를준비하는후각-면역중심선을발견했다. 두번째로,식균작용쪽으로만많은연구가진행되고있었던plasmatocyte의하위집단을발견했다.평소이런하위집단은적은비율로유지되고있다가말벌감염이나인슐린저항성같은특정상황에비율을늘리는것을발견했다.수를증폭시키면서지방세포에신호를전달해인슐린신호전달경로를저해하는것을발견했으며이는나아가전체적인면역시스템을증진시키기위한면역트레이드오프(Immunetrade-off)와관련이있다는것을알아냈다. 마지막으로,나는흑색화작용쪽으로만연구가진행되고있던crystalcell의전혀다른새로운기능을발견했다.나는산소전달과는무관하다고알려진초파리순환혈구세포가산소농도에따라그위치를변화시키며특히PPO2+crystalcell이몸전체적인산소항상성조절에관여하고있다는것을알아냈다.PPO2+crystalcell이저산소상황에서숨관에붙고떨어지며PPO2의결정화/사이토졸의상전이를통해산소를얻고특히지방세포의산소보유정도에관여한다는것을알아냈다.특히초파리애벌레가밥을먹기위해밥속으로파고들어가저산소상황을마주했을때PPO2를흑색화작용이아닌산소항상성조절에사용하는것을알아냈다. 이3가지의주제를통해나는각기다른스트레스상황에반응하는3종류의초파리순환혈구세포(plasmatocyte,crystalcell,lamellocyte)의선천성면역외적반응에대한연구를진행했다.Plasmatocyte의전신대사관련연구와lamellocyte의세포대사관련연구및crystalcell의내부산소항상성관련연구를진행함으로써초파리순환혈구세포의선천성면역외적측면에대한연구의가능성과필요성을제시할수있었다. |TherearethreemaintypesofDrosophilaembryonicallyderivedcirculatinghemocytes.Itwasknowntobedividedintoplasmatocytes,whichplaythefunctionofphagocytosis,crystalcells,whichplaytheroleofmelanization,andfinally,lamellocytes,whichplaytheroleofencapsulation.Recently,varioustypesofcirculatinghemocyteshavebeenidentifiedthroughsingle-cellanalysis.However,thefunctionofthisdiversepopulationhasnotbeenelucidatedyet.Inthisstudy,IconductedresearchontherespiratoryandmetabolicfunctionsofDrosophilahemocytes,whichhadbeenactivelystudiedonlyontheinnateimmunefunction. First,IfoundthatGABAcouldbeusedasametaboliteinthelymphgland.GABAenteredthroughtheGABAtransporterinthelymphgland,producedsuccinatethroughtheGABAshuntpathway,andaffectedlamellocytedifferentiationthroughHifstabilizationinsuchaswaspinfestation.Byilluminatingtheolfaction-immuneaxis,IfoundthatDrosophilalarvaedetecttheodorofwasp(iridomyrmecin),anaturalenemyofDrosophila,fromadistancetoprepareforlamellocytedifferentiationthroughOr49a. Second,Idiscoveredasubpopulationofplasmatocytesthathadbeenlargelystudiedonlytowardsphagocytosis.Usually,thissubgroupremainsatasmallpercentagebuthasbeenfoundtoincreaseincertainsituations,suchaswaspinfectionorinsulinresistance.Ifoundthatplasmatocytesubpopulationattenuatestheinsulinsignalingpathwaybytransmittingacytokinetoadipocyteswhileamplifyingthenumber. Finally,Irevealedacompletelydifferentfunctionofthecrystalcellinwhichtheroleofmelanizationwasmainlyrevealed.IfoundoutthatPPO2incrystalcells,whichwaspreviouslyknowntobeirrelevanttooxygendelivery,isinvolvedininternaloxygenhomeostasisthroughoutthebody.IfoundthatPPO2+crystalcellsinteractwiththetracheaandparticipateinfatbodyoxygenationthroughacrystal/cytosolphasetransition,especiallywhenlarvaeareinhypoxicsituationssuchasbeingburiedinfood. Throughthesethreetopics,IconductedastudyonthreetypesofDrosophilacirculatinghemocytes(plasmatocyte,crystalcell,andlamellocyte)respondingtodifferentstressconditions.ThepossibilityandnecessityofresearchbeyondtheinnateimmuneaspectsofDrosophilacirculatinghemocytescouldbesuggestedbyconductingresearchonthesystemicmetabolismofplasmatocyte,cellmetabolismoflamellocytes,andinternaloxygenhomeostasisofcrystalcells.

Keywords:Drosophilahemocytes,Lamellocyte,GABAshuntpathway,Orco-Immuneaxis,Plasmatocyte,Subpopulations,Crystalcell,PPO2,Oxygenhomeostasis