Migration of the guinea pig sperm membrane protein PH-20 from one localized surface domain to another does not occur by a simple diffusion-trapping mechanism☆

[摘要] Theredistributionofmembraneproteinsonthesurfaceofcellsisaprevalentfeatureofdifferentiationinavarietyofcells.Inmostcasesthemechanismresponsibleforsuchredistributionispoorlyunderstood.Twopotentialmechanismsfortheredistributionofsurfaceproteinsare:(1)passivediffusioncoupledwithtrapping,and(2)activetranslocation.WehavestudiedtheprocessofmembraneproteinredistributionforthePH-20proteinofguineapigsperm,asurfaceproteinrequiredforspermbindingtotheeggzonapellucida(P.Primakoff,H.Hyatt,andD.G.Myles(1985).J.CellBiol.101,2239–2244).PH-20proteinislocalizedtotheposteriorheadplasmamembraneofthematurespermcell.Followingtheexocytoticacrosomereaction,PH-20proteinmovesintothenewlyincorporatedinneracrosomalmembrane(IAM),placingitinapositionfavorableforaroleinbindingspermtotheeggzonapellucida(D.G.Myles,andP.Primakoff(1984).J.CellBiol.99,1634–1641).Toanalyzethemechanisticbasisforthisproteinmigration,wehaveusedfluorescencemicroscopyanddigitalimageprocessingtocharacterizePH-20proteinmigrationinindividualcells.PH-20proteinwasobservedtomoveagainstaconcentrationgradientintheposteriorheadplasmamembrane.ThisresultarguesstronglyagainstamodelofpassivediffusionfollowedbytrappingintheIAM,andinsteadsuggeststhatanactiveprocessservestoconcentratePH-20proteintowardtheboundaryseparatingtheposteriorheadandIAMregions.AtransientgradientofPH-20concentrationobservedintheIAMsuggeststhatoncePH-20proteinreachestheIAM,itisfreelydiffusing.Additionally,weobservedthatmigrationofPH-20proteinwascalciumdependent.

[学科分类] 生物科学（综合）