S100–annexin complexes – biology of conditional association

REVIEWARTICLE

S100–annexincomplexes–biologyofconditionalassociation

NaofumiMiwa1,TatsuyaUebi2,*andSatoruKawamura2,3

1DepartmentofPhysiology,SchoolofMedicine,TohoUniversity,Tokyo,Japan2GraduateSchoolofFrontierBiosciences,OsakaUniversity,Japan

3DepartmentofBiology,GraduateSchoolofScience,OsakaUniversity,Japan

Keywords

annexin;calcium;colocalization;comprehensiveinteraction;dicalcin;

EF-hand;liposome;membranetraf cking;phospholipid;S100

Correspondence

S.Kawamura,GraduateSchoolofFrontierBiosciences,OsakaUniversity,Yamada-oka1–3,Suita,Osaka565-0871,JapanFax:+81668794614Tel:+81668794610

E-mail:kawamura@fbs.osaka-u.ac.jp*Presentaddress

LaboratoryofCellSignalandMetabolism,NationalInstituteofBiomedicalInnovation,Osaka,Japan

(Received17June2008,revised7August2008,accepted22August2008)doi:10.1111/j.1742-4658.2008.06653.x

S100proteinsandannexinsbothconstitutegroupsofCa2+-bindingpro-teins,eachofwhichcomprisesmorethan10members.S100proteinsaresmall,dimeric,EF-hand-typeCa2+-bindingproteinsthatexertbothintra-cellularandextracellularfunctions.Withinthecells,S100proteinsregu-latevariousreactions,includingphosphorylation,inresponsetochangesintheintracellularCa2+concentration.AlthoughS100proteinsareknowntobeassociatedwithmanydiseases,exactpathologicalcontribu-tionshavenotbeenprovenindetail.Annexinsarenon-EF-hand-typeCa2+-bindingproteinsthatexhibitCa2+-dependentbindingtophospho-lipidsandmembranesinvarioustissues.Annexinsbringdifferentmem-branesintoproximityandassistthemtofuse,andthereforearebelievedtoplayaroleinmembranetraf ckingandorganization.SeveralS100proteinsandannexinsareknowntointeractwitheachotherineitheraCa2+-dependentorCa2+-independentmanner,andformcomplexesthatexhibitbiologicalactivities.ThisreviewfocusesontheinteractionbetweenS100proteinsandannexins,andthepossiblebiologicalrolesofthesecomplexes.RecentstudieshaveshownthatS100–annexincomplexeshavearoleinthedifferentiationofgonadcellsandneurologicaldisor-ders,suchasdepression.Thesecomplexesregulatetheorganizationofmembranesandvesicles,andtherebymayparticipateintheappropriatedispositionofmembrane-associatedproteins,includingionchannelsand or

receptors.

Introduction

TheinteractionbetweenS100andannexinproteinswasinitiallyidenti edinporcineintestinalbrushbor-der-derivedmembranes,asacomplexformedbetweenS100A10andannexinA2.AnnexinA2(previouslynamedp36orcalpactinI,etc.)isasubstrateofsrc-relatedviraltyrosinekinase[1,2],whichraisesthepossibilitythatthiscomplexmaybeinvolvedincancer-relatedpathology.ThecomplexofS100A10andannexinA2(S100A10–annexinA2complex)hasbeenfoundtobindtocytoskeletalcomponentsand

tocolocalizeinsubmembranouscompartments[3],suggestingthatthiscomplexmayplayaroleinsub-cellularvesicleorganizationtoexertitsbiologicalfunction.

Followingthese ndings,anotherS100member,S100A11(originallynamedS100Corcalgizzarin),wasfoundtointeractwithannexinA1inaCa2+-depen-dentmanner,withadditionalevidenceshowingthatthiscomplexalsobindstocytoskeletalcomponents,suchastubulinandvimentin.UnliketheinteractionbetweenS100A10andannexinA2,theinteractionbetweenS100A11andannexinA1occursinatemporal

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mannerwhentheintracellularCa2+levelincreases,andthereforethiscomplexhasbeenpostulatedtoregulateCa2+-dependentmembraneorganizationdur-ingvesiculationorinternalization.

Todate,severalotherpairsofS100proteinsandannexinshavebeenreported(Table1),anditseemstimelytoviewthesepairsasconstituentsofabroadsystemofS100–annexincomplexes.Inthissystem,someS100proteinsareabletobindtoseveralann-exins.Thehost(forexample,S100protein)anditsbindingpartner(anannexinprotein)canbedeter-minedbytheirsubcellulardistributionsandtemporalexpressionpatternsineachtissue.Inthisreview,afterabriefdescriptionofS100proteins,annexinsandourrecentlycharacterizeddicalcin,anS100-likeprotein,wereviewseveralwell-characterizedS100–annexincomplexestoobtainanunderstandingofthediver-genceofthephysiologicalrolesofthedifferentcom-plexes.ThestructuralbasisofcomplexformationisreviewedintheaccompanyingarticlebyRintala-Dempseyetal.[4].

Proteins

S100proteins

S100proteinsformafamilyofsmall(10–14kDa)Ca2+-bindingproteinsthatregulatevariousintracellu-larandextracellularprocesses.IncreasedlevelsofS100proteinshavebeenreportedtobeassociatedwithanumberofdiseases.Originally,S100A1(originallynamedS100a)andS100B(S100b)wereisolatedinbovinebrainasproteinssolublein100%(saturated)ammoniumsulfateatneutralpH[5].Todate,20S100geneshavebeenidenti edexclusivelyinvertebrates,includinghumans,withmostoftheS100genesclus-teredonhumanchromosome1q21(S100A1–S100A16),whereasnoS100geneshavebeendetectedininvertebrates[6].S100proteinsareknowntoexistashomo- heterodimericfunctionalunitsinvarioustis-

sues,includingbrain,lungandheart.AnimportantfeatureofS100proteinsistheirroleasCa2+sensors.EachS100proteinhasapairofhigh-af nityCa2+-bindingsites,calledEF-handmotifs.Whenintracellu-larCa2+concentrationsincreaseafterenvironmentalstimuli,forexample,S100proteinscanbindtoCa2+viaEF-handmotifsandundergolargeconformationalchanges.Thesechangesinducetheexposureofahydrophobicpatchatthesurfaceofthesemoleculesandassistthemtointeractwiththeirtargetproteins,includingenzymes(e.g.kinase,phospholipaseA2)andcytoskeletalproteins(e.g.actin).Inthisway,S100proteinstransduceenvironmentalsignalstointracellu-laractivitiestoregulatecellproliferation,differentia-tion,etc.[7,8].SomeS100membersaresecretedfromcellsthroughunde nedexocytoticmachinery,exertingextracellularactions,suchasanti-apoptosisandanti-coagulation,throughtheirreceptorsonthesurfaceoftheplasmamembrane.Anumberoftar-getshavebeenreportedtodate[9],and,forseveralS100members,geneticallyengineeredanimalshavebeenproducedtostudythefunctionalrole(s)ofS100proteins[10].Annexins

AnnexinsareanotherfamilyofCa2+-bindingpro-teins.TheirCa2+-bindingmotifsaredifferentfromtheEF-handtypedescribedaboveandarecalledannexintypeortypeII[11,12].OnCa2+binding,annexinscaninteractwithanionicmembranephos-pholipids,makingthem‘Ca2+-dependentphospho-lipid-bindingproteins’.Annexinswere rstidenti edfromseveralsourcesandweregivendifferentnames(e.g.lipocortin,calpactin,http://wendang.chazidian.comter,theseproteinsweregivenanewfamilynameof‘annexin’,becausethemajorpropertyofthisfamilyisto‘annex’cellu-larmembranesinaCa2+-dependentmanner[13].Annexinsaredistributedinvariousspeciesfromhumanstoplants,and,todate,thevertebrateannex-

http://wendang.chazidian.complexformationbetweenS100proteinsandannexins.AnS100–annexincomplexisformedasindicatedbythereferencenumbers.

AnnexinA1

S100A1S100A4S100A6S100A10S100A11S100A12S100B

AnnexinA2

AnnexinA5

AnnexinA6[82,83]

[61][60]

[3,22–46][58]

[89]

[82,83][88][62]

[66,70,71,74]AnnexinA11

[47,51,52,57–59,63]

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ins,whichhavebeenmostextensivelystudied,com-priseupto12members[14].Annexinsareexpressedwidelyinmanytissues,buttheirlocalizationvaries:somearepresentintracellularlyandothersarelocal-izedattheplasmamembrane.MostannexinsconsistofanindividuallyuniqueN-terminaldomainandafairlyconservedC-terminalcorethatcontainseitherfouroreightrepeatingunitsofapproximately70aminoacids.ItisbelievedthattheannexinC-terminalcoreisamodulethatmediatesbothCa2+andmem-branebinding.Annexinsinteractwithmanytargetsandexertvariousbiologicalfunctions,includingregu-lationofmembraneaggregationandmembranetraf- cking.Theyalsohaveextracellularfunctions,forexample,inanti-in ammationandanti-coagulation[11,12].Althoughafewannexinshavebeenanalysedinknockoutanimals[14,15],theirphenotypesaresubtle,sothattheirexactphysiologicalfunctionsremainelusive.Dicalcin

Dicalcin,anS100-likeCa2+-bindingproteinformerlycalledp26olf,wasoriginallyidenti edinfrog(Ranacatesbeiana)olfactoryepithelium[16].Aftertheoriginalidenti cation,however,thisproteinwasalsofoundinothertissues,includinglungandspleen.Althoughdetailedstructuralanalysis(i.e.crystallo-graphicstudy)hasnotbeencarriedout,sequencealignmentandmolecularmodellinghavesuggestedthatdicalcinconsistsoftwoS100-likeregionsalignedintandem(eachregionhasapproximately50%iden-titytothesequenceofchickS100A11),andpossiblyadoptsaremarkablysimilarconformationtothatofahomodimericformofS100B[17,18].AsallotherS100members,exceptcalbindin,formahomo-orhetero-dimerinsolutiontoexerttheirbiologicalfunctions,dicalcinmaysubstitutethefunction(s)ofS100proteinsintheformofamonomer.Basedonthisconsider-ation,wegaveitamnemonicname:‘dimerformofS100calcium-bindingprotein’.OurquantitativeCa2+-bindingstudyshowedcooperativeCa2+bindingofdicalcin,withanapparentoveralldissociationcon-stant(Kd)of10–20lm[19].OnCa2+binding,dicalcininteractswithasetofannexinmembersinboththeolfactoryandrespiratorycilia[20],aswellaswithseveralotherolfactoryciliaproteins,includingb-adrenergicreceptor-likeprotein,whichhasnotyetbeencloned[21].Throughinteractionswithannex-ins,dicalcinenhancesliposomeaggregationinaCa2+-dependentmanner,whichsuggeststhatdicalcinplaysaroleinmembrane-associatedeventsintheolfactoryandrespiratorycilia(seebelow).

S100–annexincomplexes

S100A10–annexinA2complex

Distribution

ThemRNAexpressionofS100A10andannexinA2hasbeenshowninvariousmousetissues,andbothareexpressedcoincidentallyathighlevelsinlung,intestineandthymus[22].Onthebasisofanimmunohisto-chemicalcolocalizationstudy[3],bothS100A10andannexinA2werefoundinthefollowingsites:(a)brushborderinporcineintestine;(b)glomerularcellsinclu-dingmesangialcellsandendothelialcellsinporcinekidney;(c)endothelialcellsinporcinebrain;and(d) broblastsinbovineheart.Withinthesecells,bothproteinsweremainlylocalizedtoendosomesandattheplasmamembrane[23–25].Propertiesofinteraction

S100A10(alternativelycalledp11)andannexinA2areknowntoexistasaheterotetramer[(S100A10)2–(ann-exinA2)2]inamembranefraction[26].TheS100A10-bindingsiteinannexinA2isconsideredtoresideinN-terminalresidues(Val3,Ile6,Leu7,Leu10)basedoncosedimentationandgel ltrationexperimentsusingtruncatedannexinmutants[27,28].S100A10isanexceptionalproteinamongstS100membersintermsofCa2+binding:S100A10isunabletobindtoCa2+becauseofamutationwithinitsEF-handmotifs.ThreeaminoacidresiduesarelostintheN-terminalEF-handmotifandcrucialaminoacidsaresubstitutedintheC-terminalmotif[29].Asaconsequence,theassociationofS100A10andannexinA2isCa2+inde-pendent:thesetwoproteinsformaheterotetramericcomplexconstitutivelyregardlessoftheCa2+concen-tration.InsteadofCa2+,post-translationalmodi ca-tionsofannexinA2haveregulatoryeffectsontheassociationwithS100A10:N-acetylationofannexinA2isnecessaryforthisassociation[30,31]andproteinkinaseC-mediatedphosphorylationdecreasestheaf n-ityofannexinA2forS100A10[32].Bindingtargetsofthecomplex

InanS100A10–annexinA2complex,anS100A10dimerresidesinthecentreofthecomplex,intercon-nectingtwoannexinA2molecules[26].Annexinsintheouterpositionofthiscomplexpreferentiallybindtoanionicphospholipids,suchasphosphatidylinositol4,5-bisphosphate,whichisenrichedinlipidraftsintheplasmamembrane.BecauseS100A10hastheabilitytobindtocytoskeletalproteins,suchasactin,this

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complexcanlinkmembranesand orvesiclestocyto-skeletalproteinstoregulatemembraneorganization.ThisassociationofanS100–annexinA2complexwithlipidmembranesisCa2+dependentwithaKdvalueof2lm[33],whichprobablyre ectsCa2+bindingtoannexinA2(S100A10doesnothaveCa2+-bindingability).TheS100–annexinA2complexhasalsobeenshowntointeractwithmembrane-relatedproteins.Theyincludecertaintypesofsodiumchannel[34],potassiumchannels[35,36],transientreceptorpotentialchannels[37]andserotonin5-HT1Breceptors[38].

Themoleculartopologyofthiscomplexinthemembrane-boundstatehasbeenpostulatedfromtwoscenariosderivedfromdifferentexperimentalapproaches.CryoelectronmicroscopyhassuggestedthateachannexinA2moleculeintheouterpositionofthecomplexbindstoonemembrane,andthereforethetetramericcomplexlinkstwodifferentmembranes[39].Bycontrast,scanningforcemicroscopyhassuggestedthattwoannexinA2moleculesbindtothesamemem-brane[40].Inthelattercase,theS100A10dimerresidesinarelativelyouterpositionofthecomplexawayfromthemembrane,andtherebyinteractswithotherproteins(e.g.cytosolicportionofchannelsorreceptors),enablingthemtobeassociatedwithorincorporatedintothemembranesthatareboundbyannexinA2molecules.

Inadditiontotheintracellulartargetsdescribedabove,theS100A10–annexinA2complexhasbeenshowntobindtotissue-typeplasminogenactivatorintheextracellularspaceandtoactasafunctionalrecep-tortoproduceplasminogenfromtissue-typeplasmino-genactivator[41].However,theexactbindingcharacterremainsamatterofdebate[42].Biologicalroles

Severalstudiesusingknockoutanimalshavesuggestedthebiologicalrolesofthiscomplex[43].Foulkesetal.[44]havedemonstratedthatS100A10– –miceshowde cientnociception,whichmaybeattributedtoaseveredecreaseinthesodiumcurrent.Svenningssonetal.[38]havefoundthatS100A10) )miceexhibitadepression-likephenotypewithreducedresponsesto5-HT1Bagonists;thissuggeststhatthelackofthiscomplexcausesadepressivedisorder.Recently,thisgrouphasalsoshownthatS100A10hasaninhibitoryroleonsomeabnormalbehaviorscausedbyl-3,4-dihydroxyphenylalanineadministrationtoananimalmodelofParkinsonism[45].Theidenti cationofthetargetsoftheS100A10–annexinA2complex(seeabove)ledtothesuggestionthatthiscomplexfunctionsasaguidingmoleculeofchannelsand or

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receptorsfromtheendoplasmicreticulumtotheGolgiand orinternalizedvesicletotheplasmamem-brane.Thede citsintheseknockoutanimalsmaybeattributedtotheimproperassociationwithorincorporationintotheplasmamembraneofthesechannelsand orreceptors.

Anotherpossiblebiologicalroleofthiscomplexisrelatedto brinhomeostasis.Inthenormalbloodvessel, brinisnotdepositedandarterialthrombinisclearedafterinjury.However,S100A10) )knockoutanimalsshowadisplaceddepositionof brininthemicrovasculatureandincompleteclearanceofarterialthrombin[46];thismaybecausedbythelossoftheS100A10–annexinA2complexontheoutersurfaceoftheplasmamembraneoftheendothelialcells.S100A11–annexinA1complex

Distribution

TheassociationofS100A11(previouslyknownasS100Corcalgizzarin)withannexinA1wasinitiallyfoundduringthesearchfortargetsofannexinA1,aprototypeofannexinthathasattractedconsiderableinterestbecauseofitsinvolvementincellgrowthanddifferentiation[47].S100A11mRNAisdistributedinalmostallhumantissues.Itishighlyexpressedinmuscle,heartandbladder[48,49].AnnexinA1isalsowidelyexpressedinmanytissues,includinglung,kidneyandspleen[50].Withinthecells,annexinA1islocalizedmostlyinthecytosol,exceptforitspresencewithinnucleiofthehumanrespiratoryepithelium[50].Althoughthesubcellularcolocalizationofthesetwoproteinsinvivohasnotbeenstudiedindetail,ectopi-callyexpressedS100A11hasbeenshowntocolocalizewithintrinsicannexinA1ontheearlyendosomalmembranesof broblasticBHKcells[51].BiochemicalstudieshaveshownthatS100A11andannexinA1arebothpresentinthecorni edenvelopepreparationofhumankeratinocytes[52].Propertiesofinteraction

IncontrastwiththeinteractionbetweenS100A10andannexinA2,S100A11bindstoannexinA1inaCa2+-dependentmanner[47],evokingthesuggestionthatthiscomplexregulatesCa2+-dependentcellularevents.S100A11hasbeenshowntobindtoannexinA1athighCa2+concentrations(1mm),presumablyformingaheterotetramer[(S100A11)2–(annexinA1)2][47].Asanindividualprotein,S100A11alonebindstoCa2+withaKdvalueof8–16lm[53]andundergoesconformationalchangeswithahalf-maximaleffec-tiveCa2+concentrationatasimilarconcentration

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( 35lm)inmeasurementswith uorescent-labelledprobes[54].AnnexinA1alonebindstoCa2+withaKdvalueof20–75lm,enhancingitsbindingactivityforphospholipidvesicles[55,56].AlthoughdetailedanalysisoftheCa2+concentrationrequiredfortheassociationofS100A11withannexinA1hasnotyetbeencarriedout,thesetwoproteinshavebeenhypo-thesizedtoassociatewithinasimilarCa2+concentra-tionrangeinwhichbothS100A11andannexinA1canbindtoCa2+.

TheS100A11-bindingsiteinannexinA1isconsid-eredtoresideintheN-terminalresidues,asrevealedbyexperimentssimilartothoseusedfortheidenti ca-tionoftheS100A10-bindingsiteinannexinA2[47,57,58].Withregardtothespeci cityofS100A11bindingtoannexinmembers,apreviousstudyusing uorescent-labelledpeptideshasshownthatS100A11interactsspeci callywiththeannexinA1N-terminaldomainanddoesnotinteractwiththecorrespondingN-terminaldomainofannexinA2[59].However,arecentstudyusingannexinA2peptideshasshownthatS100A11alsointeractswiththeN-terminaldomainofannexinA2[58],consistentwiththe ndingthatann-exinA2showsbroadbindingspeci citytootherS100members(e.g.S100A4andS100A6)[60,61].BindingofS100A11tobothannexinsA1andA2suggestspossi-blemultifunctionalrolesofS100A11intheregulationofmembranetraf ckingand ororganization.Bindingtargetsandrolesofthecomplex

IncontrastwiththedetailedstructuralanalysisoftheS100A11–annexinA1complex,thecellulartargetsandfunctionsofthiscomplexhavenotbeenstudiedindetail.Potentialtargetsofthiscomplexmaybephos-pholipidsandcytoskeletalproteinsbasedonthecon-siderationofthefollowingreports:(a)annexinA1alonebindstolipidmembranesinaCa2+-dependentmanner[55,56];(b)S100A11alonebindstocytoskele-talproteinswithaKdvalueof3lminporcineheart[53];(c)S100A11isalsoabletointeractwithannexinA6atahighCa2+concentration(1mm),andthisS100A11–annexinA6complexbindstonativelipo-somesderivedfromratvascularsmoothmuscleaswellasphosphatidylserineliposomesinthepresenceofCa2+(200lm)[62].

Withregardtoapotentialbiologicalrole(s)oftheS100A11–annexinA1complex,Robinsonetal.[52]havereportedthatS100A11andannexinA1arecolo-calizedbeneaththeplasmamembraneduringthe nalstagesofepidermalkeratinocytedifferentiation,indi-catingthatthiscomplexmaybeinvolvedintheforma-tionofthecorni edenvelopeinhumankeratinocytes.

AbiochemicalstudyhasshownthatS100A11sup-pressesthephosphorylationofannexinA1byproteinkinaseC,resultinginadecreaseintheaggregationofphospholipidvesicles[63].ThisresultalsosuggestsarolefortheS100A11–annexinA1complexintheregu-lationofmembraneorganization.

S100A11hasbeenshowntoinhibitactin-activatedmyosinMg2+-ATPaseactivityinaCa2+-dependentmannerandtoregulatethegenerationofsmoothmus-cleforcewithaKdvalueof50lm[64].Insmoothmuscle,however,annexinA1isnotexpressedabun-dantly[50],andthereforetheS100A11–annexinA1complexmaynotbeinvolvedinthisbiologicaleffect.S100A6–annexinA11complex

Distribution

BothS100A6(formallycalledcalcyclin)andannexinA11havebeenstudiedtoinvestigatetheirinvolvementincellcycleregulationandcancerbiology,becausetheexpressionlevelsoftheseproteinsarehighinmalig-nanttumours[65,66].

S100A6isexpressedinsmoothmusclecells,epithe-lialcellsand broblastsinalmostallmammaliantissues,includingintestine,kidney[67,68]andbrain[69].Withinthesecells,S100A6isexpressedattheplasmamembraneandthenuclearenvelopeinembry-onicpigtestis-derivedSTcelllines,aswellashumanskinandembryonicmousetestis[66,70,71].TheexpressionlevelofS100A6iselevatedinanumberofmalignanttumours,suchasacutemyeloidleukaemia,neuroblastomaandmelanomacelllines[72,73],withpeakexpressionbetweentheG0andSphasesofthecellcycle[68,74,75].

AnnexinA11isalsowidelydistributedinthenucle-oplasminmanyculturedcelllines.ThesubcellulardistributionofannexinA11isalteredduringthecellcycle:itshowsadynamicandbiphasicinteractionwiththenuclearenvelope, rstduringenvelopebreakdownandsecondduringitsreassembly[66].

PropertiesofinteractionandtargetsofthecomplexCa2+-dependentinteractionofS100A6andannexinA11wasinitiallyfoundinbiochemicalS100A6af nitychromatography[76].However,ourknowledgeofthisinteraction(e.g.bindingpropertyandmoleculartargetofthecomplex)isstilllimited.S100A6hasbeenshowntobindtotheN-terminus(Gln49–Thr62)ofannexinA11atapproximately200lmCa2+.ThisS100A6–annexinA11complexhasbeenshowntobindtophospholipidvesiclesinthepresenceofCa2+(1mm)[76].

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