细胞的社会关系

功能:1.将细胞整合到特定组织上2.细胞连接:细胞之间的粘附和通讯3.细胞-间质粘附4.细胞外基质的组分与功能5.细胞壁第十五章细胞的社会关系：细胞连接,细胞粘着，胞外基质细胞连接的功能分类AFunctionalClassificationofCellJunctions1.封闭连接,Occludingjunctions(紧密连接,tightjunctions)2.锚定连接Anchoringjunctionsa.肌动蛋白纤维相关的锚定连接i.细胞-细胞之间的连接(e.g.,粘着带,adhesionbelts)ii.细胞-间质之间的连接(e.g.,粘着斑,focalcontacts)iii.隔膜连接(仅无脊椎动物)b.中间丝相关的锚定连接i.细胞-细胞之间(桥粒,desmosomes)ii.细胞-间质之间(半桥粒,hemidesmosomes)3.通讯连接(Communicatingjunctions)a.间隙连接,gapjunctionsb.化学突触,chemicalsynapsesc.胞间连丝,plasmodesmata(plantsonly)Figure19-1Simplifieddrawingofacross-sectionthroughpartofthewalloftheintestine.Thislong,tubelikeorganisconstructedfromepithelialtissues(red),connectivetissues(green),andmuscletissues(yellow).Eachtissueisanorganizedassemblyofcellsheldtogetherbycell-celladhesions,extracellularmatrix,orboth.Figure19-2Theroleoftightjunctionsintranscellulartransport.功能：①阻止可溶性物质从上皮细胞层一侧通过胞外间隙扩散到另一侧，形成渗透性屏障，起封闭作用。血脑屏障②形成上皮细胞质膜蛋白与膜脂分子侧向扩散的屏障，从而维持上皮细胞的极性。TightjunctionsFigure19-3Tightjunctionsallowcellsheetstoserveasbarrierstosolutediffusion.(A)Schematicdrawingshowinghowasmallextracellulartracermoleculeaddedononesideofanepithelialcellsheetcannottraversethetightjunctionsthatsealadjacentcellstogether.(B)Electronmicrographsofcellsinanepitheliumwhereasmall,extracellular,electron-densetracermoleculehasbeenaddedtoeithertheapicalside(ontheleft)orthebasolateralside(ontheright);inbothcasesthetracerisstoppedbythetightjunction.(B,courtesyofDanielFriend.)Figure19-4Structureofatightjunctionbetweenepithelialcellsofthesmallintestine.Thejunctionsareshownschematicallyin(A)andinfreeze-fracture(B)andconventional(C)electronmicrographs.Notethatthecellsareorientedwiththeirapicalendsdown.In(B)theplaneofthemicrographisparalleltotheplaneofthemembrane,andthetightjunctionappearsasabeltlikebandofanastomosingsealingstrandsthatencircleeachcellinthesheet.Thesealingstrandsareseenasridgesofintramembraneparticlesonthecytoplasmicfracturefaceofthemembrane(thePface)orascomplementarygroovesontheexternalfaceofthemembrane(theEface)(seeFigure19-5).In(C)thejunctionisseenasaseriesoffocalconnectionsbetweentheouterleafletsofthetwointeractingplasmamembranes,eachconnectioncorrespondingtoasealingstrandincross-section.(BandC,fromN.B.Gilula,inCellCommunication[R.P.Cox,ed.],pp.1-29)Figure19-5Acurrentmodelofatightjunction.Itispostulatedthatthesealingstrandsthatholdadjacentplasmamembranestogetherareformedbycontinuousstrandsoftransmembranejunctionalproteins,whichmakecontactacrosstheintercellularspaceandcreateaseal.Inthisschematicthecytoplasmichalfofonemembranehasbeenpeeledbackbytheartisttoexposetheproteinstrands.Twoperipheralproteinsassociatedwiththecytoplasmicsideoftightjunctionshavebeencharacterized,buttheputativetransmembraneproteinhasnotyetbeenidentified.Infreeze-fractureelectronmicroscopythetight-junctionproteinswouldremainwiththecytoplasmic(Pface)halfofthelipidbilayertogivethepatternofintramembraneparticlesseeninFigure19-4B,insteadofstayingintheotherhalfasshownhere.嵴线Figure19-6Anchoringjunctionsinanepithelialtissue.锚定连接将相邻细胞的骨架系统或将细胞与基质相连形成一个坚挺有序的细胞群体。锚定连接Figure19-7锚定连接的蛋白组成:intracellularattachmentproteinsandtransmembranelinkerproteins.细胞内附着蛋白跨膜连接的糖蛋白粘连蛋白（钙黏蛋白）盘状致密斑角蛋白纤维（中间纤维）Figure4-8桥粒结构模式图桥粒30nm整联蛋白层粘连蛋白Figure19-12桥粒.(A)Anelectronmicrographofthreedesmosomesbetweentwoepithelialcellsintheintestineofarat.(B)Anelectronmicrographofasingledesmosomebetweentwoepidermalcellsinadevelopingnewt（蝾螈）,showingclearlytheattachmentofintermediatefilaments.(C)Aschematicdrawingofadesmosome.Onthecytoplasmicsurfaceofeachinteractingplasmamembraneisadenseplaquecomposedofamixtureofintracellularattachmentproteins(includingplakoglobinanddesmoplakins).Eachplaqueisassociatedwithathicknetworkofkeratinfilaments,whichareattachedtothesurfaceoftheplaque.Transmembranelinkerproteins,whichbelongtothecadherinfamilyofcell-celladhesionmolecules,bindtotheplaquesandinteractthroughtheirextracellulardomainstoholdtheadjacentmembranestogetherbyaCa2+-dependentmechanism.(A,fromN.B.Gilula,inCellCommunication,pp.1-29;B,fromD.E.Kelly,JCB.28:51-59)Figure19-13Thedistributionofdesmosomesandhemidesmosomesinepithelialcellsofthesmallintestine.Thekeratinfilamentnetworksofadjacentcellsareindirectlyconnectedtooneanotherthroughdesmosomesandtothebasallaminathroughhemidesmosomes.Figure19-8Adhesionbeltsbetweenepithelialcellsinthesmallintestine.显著特点：可收缩的纤维束，平行于细胞膜。细胞-细胞之间的肌动蛋白由跨膜连接的糖蛋白（钙粘素）相连接。黏合带紧密连接肌动蛋白纤维束粘着带钙粘素30nmFigure19-9单层上皮细胞可折叠形成上皮细胞管。Itisthoughtthattheorientedcontractionofthebundleofactinfilamentsrunningalongadhesionbeltscausestheepithelialcellstonarrowattheirapexandthatthisplaysanimportantpartintherollingupoftheepithelialsheetintoatube(althoughcellularrearrangementsarealsothoughttoplayanimportantpart).AnexampleistheformationoftheneuraltubeinearlyvertebratedevelopmentFigure19-11Aseptatejunction（仅无脊椎动物）.软体动物2个细胞之间的隔膜连接电镜图。Theinteractingplasmamembranes,seenincross-section,areconnectedbyparallelrowsofjunctionalproteins.Therows,whichhavearegularperiodicity,areseenasdensebarsorsepta.(FromN.B.Gilula,inCellCommunication[R.P.Cox,ed.],pp.1-29)隔膜连接Table19-2锚定连接连接跨膜连接蛋白（粘着因子