Apicalmembranerecyclinghasbeenproposedtobeimportantfornormalhaircellfunction.Thecurrentstudyreportsaninvitroworkthatdemonstratesthepresenceofphosphatidylserine(PS)andPS-positivevesicleslabeledbyAnnexinVintheapicalportionofhaircells.ThefollowingcharacteristicsofthePS-positivevesicleswerenoticedusingscanningconfocalfluorescencemicroscopy:(1)variablesizesaround200nm;(2)variabledistributionpatterns(eitheruniformlyalonginpidualstereociliainthehairbundleorirregular)inthestereociliafromcelltocell;(3)variablesizesandnumbersatlocationsalongtheborderofthecuticularplate(CP),withalargenumberofthemlocatedatthevestigalkinociliallocation;(4)motilitywithsomeofthevesiclesduringtheobservationperiod;(5)increaseinPSlabelingandthenumberofPS-positivevesiclesafterloudsoundstimulation;and(6)decreasedPSlabelingandPS-positivevesiclenumbersfollowingtreatmentwithLY-294002,aPI3-kinaseinhibitor.TheseresultssuggestthatthepresenceofPS-positivevesiclesattheapicalareaofhaircellsmaybeindicativeofvesiclesheddingortransportationofaproteinorrafts.
