Integrin Signaling Regulates Blastocyst Adhesion to Fibronectin at Implantation: Intracellular Calcium Transients and Vesicle Trafficking in Primary Trophoblast Cells

[摘要] Accumulatingevidenceindicatesthattheendometrialextracellularmatrix(ECM)modulatestrophoblastadhesionduringmouseblastocystimplantation.Inpreviousstudiesofadhesion-competentmouseblastocysts,wehavedemonstratedthatintegrin-mediatedfibronectin(FN)-bindingactivityontheapicalsurfaceoftrophoblastcellsisinitiallylow,butbecomesstrengthenedafterembryosareexposedtoFN.Inthepresentstudy,wehaveexaminedwhethertheligand-inducedupregulationoftrophoblastadhesiontoFNismediatedbyintegrinsignaling.ThestrengtheningofadhesiontoFNrequiredintegrinligation,whichrapidlyelevatedcytoplasmic-freeCa2+.ChelationofintracellularCa2+usingBAPTA-AM,orinhibitionoftheCa2+-dependentproteins,proteinkinaseCorcalmodulin,significantlyattenuatedtheeffectofFNonbindingactivity.Furthermore,directelevationofcytoplasmicCa2+levelswithionomycinupregulatedFN-bindingactivity,demonstratingthatCa2+signalingisrequiredandsufficientforstrongadhesiontoFN.Ca2+signalingmayinduceproteintrafficking,aknownrequirementforligand-inducedupregulationofFN-bindingactivity.Indeed,intracellularvesiclesaccumulatedinadhesion-competentblastocysts,butwereabsentafterexposuretoeitherFNorionomycin.Thesefindingssuggestthat,duringimplantation,contactbetweenperi-implantationblastocystsandFNelevatesintracellularCa2+,whichstrengthenstrophoblastadhesiontoECMthroughproteinredistribution.

[学科分类] 生物科学（综合）

[关键词] ovum implantation;blastocyst;trophoblast;fibronectin;integrins;extracellular matrix;trafficking;cell adhesion;Ca2+ signaling;signal transduction