SNARE Complex Assembly Is Required for Human Sperm Acrosome Reaction

[摘要] Exocytosisoftheacrosome(theacrosomereaction)isaterminalmorphologicalalterationthatspermmustundergopriortopenetrationoftheextracellularcoatoftheegg.Ca2+isanessentialmediatorofthisregulatedsecretoryevent.Aidedbyastreptolysin-Opermeabilizationprotocoldevelopedinourlaboratory,wehavepreviouslydemonstratedrequirementsforRab3A,NSF,andsynaptotagminVIinthehumanspermacrosomereaction.Interestingly,Rab3AelicitsanexocytoticresponseofcomparablemagnitudetothatofCa2+.Here,wereportadirectrolefortheSNAREcomplexintheacrosomereaction.First,thepresenceofSNAREproteinsisdemonstratedbyWesternblot.Second,theCa2+-triggeredacrosomereactionisinhibitedbybotulinumneurotoxinsBoNT/A,-E,-C,and-F.Third,antibodyinhibitionstudiesshowarequirementforSNAP-25,SNAP-23,syntaxins1A,1B,4,and6,andVAMP2.Fourth,additionofbacteriallyexpressedSNAP-25andSNAP-23abolishesexocytosis.AcrosomereactionelicitedbyRab3-GTPisalsoinhibitedbyBoNT/A,-C,and-F.Takentogether,theseresultsdemonstratearequirementformembersofallSNAREproteinfamiliesintheCa2+-andRab3A-triggeredacrosomereaction.Furthermore,theyindicatethattheonsetofspermexocytosisreliesonthefunctionalassemblyofSNAREcomplexes.

[学科分类] 生物科学（综合）

[关键词] acrosome;calcium;exocytosis;Rab3;SNAP-25;SNARE;sperm;syntaxin;toxin;VAMP