Stromatoxin-1(ScTx-1) hasbeenisolatedfromthevenomoftheAfricantarentula Stromatopelmacalceata.Stromatoxin-1 isa34amino-acidlongpeptidethatbelongstothestructuralfamilyofinhibitorcystineknotpeptidesreticulatedbythreedisulfidebridges.IthasanamidatedC-terminusandbearsstronghomologywithhanatoxin1(83%).Stromatoxin-1 inhibitswithhighaffinitiesKv2.1andKv2.2,thatencodedelayedK+ channels(respectively,withIC50 of12and21nM).Theblockisvoltage-dependentandslowlyreversIBLe. Stromatoxin-1 isalsoaverysensitiveinhibitorofKv4.2,thatencodesatransientK+ current(IC50 of1.2nM).Herealso,theblockisvoltage-dependentindicatingthatScTx-1actsasagatingmodifierratherthanaporeblocker.ReversibilityisfasteronKv4.2channels.Incontrast,Stromatoxin-1 hasnoeffectonKv1.1,Kv1.2,Kv1.3,Kv1.4,Kv1.5,Kv1.6orKv3.4channels.Thetoxinhasalsonoeffectonvoltage-dependentNa+ andCa2+ channelsofcerebellargranulecells. Stromatoxin-1 wasfoundtoincreasethespontaneousphasiccontractionamplitude,muscleforceandtoneinisolatedraturinarybladdersmoothmuscle.Italsoenhancesmyogenicconstrictioninpressurizedarterialsegments.
Description:
AAsequence: Asp-Cys2-Thr-Arg-Met-Phe-Gly-Ala-Cys9-Arg-Arg-Asp-Ser-Asp-Cys15-Cys16-Pro-His-Leu-Gly-Cys21-Lys-Pro-Thr-Ser-Lys-Tyr-Cys28-Ala-Trp-Asp-Gly-Thr-Ile-NH2
Disulfidebonds:Cys2-Cys16,Cys9-Cys21 andCys15-Cys28
Length(aa):34
Formula:C156H237N49O48S7
MolecularWeight: 3791,3Da
Appearance:whitelyophilizedsolid
Solubility:waterorsalinebuffer
CASnumber:
Source:Synthetic
Purityrate:>98%
Reference:
Kv2dysfunctionafterperipheralaxotomyenhancessensoryneuronresponsivenesstosustainedinput
PeripheralnerveinjuriescausedbytraumaareassociatedwithincreasedsensoryneuronexcitABIlityanddebilitatingchronicpainsymptoms.Axotomy-inducedalterationsinthefunctionofionchannelsarethoughttolargelyunderliethepathophysiologyofthesephenotypes.Here,wecharacterisethemRNAdistributionofKv2familymembersinratdorsalrootganglia(DRG)anddescribealinkbetweenKv2functionandmodulationofsensoryneuronexcitability.Kv2.1andKv2.2wereamplyexpressedincellsofallsizes,beingparticularlyabundantinmedium-largeneuronsalsoimmunoreactiveforneurofilament-200.Peripheralaxotomyledtoarapid,robustandlong-lastingtranscriptionalKv2downregulationintheDRG,correlatedwiththeonsetofmechanicalandthermalhypersensitivity.TheconsequencesofKv2loss-of-functionweresubsequentlyinvestigatedinmyelinatedneuronsusingintracellularrecordingsonexvivoDRGpreparations.Innaïveneurons,pharmacologicalKv2.1/Kv2.2inhibitionbystromatoxin-1(ScTx)resultedinshorteningofactionpotential(AP)after-hyperpolarization(AHP).Incontrast,ScTxapplicationonaxotomizedneuronsdidnotalterAHPduration,consistentwiththeinjury-inducedKv2downregulation.InaccordancewithashortenedAHP,ScTxtreatmentalsoreducedtherefractoryperiodandimprovedAPconductiontothecellsomaduringhighfrequencystimulation.TheseresultssuggestthatKv2downregulationfollowingtraumaticnervelesionfacilitatesgreaterfidelityofrepetitivefiringduringprolongedinputandthusnormalKv2functionispostulatedtolimitneuronalexcitability.Insummary,wehaveprofiledKv2expressioninsensoryneuronsandprovideevidenceforthecontributionofKv2dysfunctioninthegenerationofhyperexcitablephenotypesencounteredinchronicpainstates.
TsantoulasC., etal. (2014) Kv2dysfunctionafterperipheralaxotomyenhancessensoryneuronresponsivenesstosustainedinput. ExpNeurol. PMID:24252178
Voltage-gatedK+channelssensitivetostromatoxin-1regulatemyogenicandneurogeniccontractionsofraturinarybladdersmoothmuscle
Membersofthevoltage-gatedK(+)(K(V))channelfamilyaresuggestedtocontroltherestingmembranepotentialandtherepolarizationphaseoftheactionpotentialinurinarybladdersmoothmuscle(UBSM).Recentstudiesreportthatstromatoxin-1,apeptideisolatedfromtarantulas,selectivelyinhibitsK(V)2.1,K(V)2.2,K(V)4.2,andK(V)2.1/9.3channels.TheobjectiveofthisstudywastoinvestigatewhetherK(V)channelssensitivetostromatoxin-1participateintheregulationofratUBSMcontractilityandtoidentifytheirmolecularfingerprints.Stromatoxin-1(100nM)increasedthespontaneousphasiccontractionamplitude,muscleforce,andtoneinisolatedUBSMstrips.However,stromatoxin-1(100nM)hadnoeffectontheUBSMcontractionsinducedbydepolarizingagentssuchasKCl(20mM)orcarbachol(1microM).Thisindicatesthat,underconditionsofsustainedmembranedepolarization,theK(V)channelssensitivetostromatoxin-1havenofurthercontributiontothemembraneexcitabilityandcontractility.Stromatoxin-1(100nM)increasedtheamplitudeoftheelectricalfieldstimulation-inducedcontractions,suggestingalsoaroleforthesechannelsinneurogeniccontractions.RT-PCRexperimentsonfreshlyisolatedUBSMcellsshowedmRNAexpressionofK(V)2.1,K(V)2.2,andK(V)9.3,butnotK(V)4.2channelsubunits.ProteinexpressionofK(V)2.1andK(V)2.2channelswasdetectedusingWesternblotandwasfurtherconfirmedbyimmunocytochemicaldetectioninfreshlyisolatedUBSMcells.ThesenovelfindingsindicatethatK(V)2.1andK(V)2.2,butnotK(V)4.2,channelsubunitsareexpressedinratUBSMandplayakeyroleinopposingbothmyogenicandneurogenicUBSMcontractions.
ChenM., etal. (2013) Voltage-gatedK+ channelssensitivetostromatoxin-1regulatemyogenicandneurogeniccontractionsofraturinarybladdersmoothmuscle. AmJPhysiolRegulIntegrCompPhysiol. PMID:20393158
KV2.1andelectricallysilentKVchannelsubunitscontrolexcitabilityandcontractilityofguineapigdetrusorsmoothmuscle
Voltage-gatedK(+)(K(V))channelsareimplicatedindetrusorsmoothmuscle(DSM)function.However,littleisknownaboutthefunctionalroleoftheheterotetramericK(V)channelsinDSM.Inthisreport,weprovidemolecular,electrophysiological,andfunctionalevidenceforthepresenceofK(V)2.1andelectricallysilentK(V)channelsubunitsinguineapigDSM.Stromatoxin-1(ScTx1),aselectiveinhibitorofthehomotetramericK(V)2.1,K(V)2.2,andK(V)4.2aswellastheheterotetramericK(V)2.1/6.3andK(V)2.1/9.3channels,wasusedtoexaminetheroleoftheseK(V)channelsinDSMfunction.RT-PCRindicatedmRNAexpressionofK(V)2.1,K(V)6.2-6.3,K(V)8.2,andK(V)9.1-9.3subunitsinisolatedDSMcells.K(V)2.1proteinexpressionwasconfirmedbyWesternblotandimmunocytochemistry.Perforatedwholecellpatch-clampexperimentsrevealedthatScTx1(100nM)inhibitedtheamplitudeoftheK(V)currentinfreshlyisolatedDSMcells.ScTx1(100nM)didnotsignificantlychangethesteady-stateactivationandinactivationcurvesforK(V)current.However,ScTx1(100nM)decreasedtheactivationtime-constantoftheK(V)currentatpositivevoltages.Althoughourpatch-clampdatacouldnotexcludethepresenceofthehomotetramericK(V)2.1channels,thebiophysicalcharacteristicsoftheScTx1-sensitivecurrentwereconsistentwiththepresenceofheterotetramericK(V)2.1/silentK(V)channels.Current-clamprecordingsshowedthatScTx1(100nM)didnotchangetheDSMcellrestingmembranepotential.ScTx1(100nM)increasedthespontaneousphasiccontractionamplitude,muscleforce,andmuscletoneaswellastheamplitudeoftheelectricalfieldstimulation-inducedcontractionsofisolatedDSMstrips.Collectively,ourdatarevealedthatK(V)2.1-containingchannelsareimportantphysiologicalregulatorsofguineapigDSMexcitabilityandcontractility.
HristovKL., etal. (2012) KV2.1andelectricallysilentKVchannelsubunitscontrolexcitabilityandcontractilityofguineapigdetrusorsmoothmuscle. AmJPhysiolCellPhysiol.PMID:21998137
MechanismofestrADIol-inducedblockofvoltage-gatedK+currentsinratmedialpreopticneurons
Thepresentstudywasconductedtocharacterizepossiblerapideffectsof17-β-estradiolonvoltage-gatedK(+)channelsinpreopticneuronsand,inparticular,toidentifythemechanismsbywhich17-β-estradiolaffectstheK(+)channels.Whole-cellcurrentsfromdissociatedratpreopticneuronswerestudiedbyperforated-patchrecording.17-β-Estradiolrapidly(withinseconds)andreversiblyreducedtheK(+)currents,showinganEC(50)valueof9.7µM.Theeffectwasslightlyvoltagedependent,butindependentofexternalCa(2+),andnotsensitivetoanestrogen-receptorblocker.Although17-α-estradiolalsosignificantlyreducedtheK(+)currents,membrane-impermeantformsofestradioldidnotreducetheK(+)currentsandotherestrogens,testosteroneandcholesterolwereconsiderablylesseffective.ThereductioninducedbyestradiolwasoverlappingwiththatoftheK(V)-2-channelblockerr-stromatoxin-1.ThetimecourseofK(+)currentin17-β-estradiol,withatime-dependentinhibitionandaslightdependenceonexternalK(+),suggestedanopen-channelblockmechanism.Thepropertiesofblockwerepredictedfromacomputationalmodelwhere17-β-estradiolbindstoopenK(+)channels.Itwasconcludedthat17-β-estradiolrapidlyreducesvoltage-gatedK(+)currentsinawayconsistentwithanopen-channelblockmechanism.Thissuggestsanewmechanismforsteroidactiononionchannels.
DruzinM., etal. (2011) Mechanismofestradiol-inducedblockofvoltage-gatedK+currentsinratmedialpreopticneurons. PLoSOne. PMID:21625454
PostnataldevelopmentofA-typeandKv1-andKv2-mediatedpotassiumchannelcurrentsinneocorticalpyramidalneurons
Potassiumchannelsregulatenumerousaspectsofneuronalexcitability,andseveralvoltage-gatedK(+)channelsubunitshavebeenidentifiedinpyramidalneuronsofratneocortex.Previousstudieshaveeitherconsideredthedevelopmentofoutwardcurrentasawholeordividedcurrentsintotransient,A-typeandpersistent,delayedrectifiercomponentsbutdidnotdifferentiatebetweencurrentcomponentsdefinedbyα-subunittype.TofacilitatecomparisonsofstudiesreportingK(+)currentsfromanimalsofdifferentagesandtounderstandthefunctionalrolesofspecificcurrentcomponents,wecharacterizedthepostnataldevelopmentofidentifiedKvchannel-mediatedcurrentsinpyramidalneuronsfromlayersII/IIIfromratsomatosensorycortex.Boththepersistent/slowlyinactivatingandtransientcomponentsofthetotalK(+)currentincreasedindensitywithpostnatalage.WeusedspecificpharmacologicalagentstotesttherelativecontributionsofputativeKv1-andKv2-mediatedcurrents(100nMα-dendrotoxinand600nMstromatoxin,respectively).Acombinationofvoltageprotocol,pharmacology,andcurvefittingwasusedtoisolatetherapidlyinactivatingA-typecurrent.Wefoundthatthedensityofallidentifiedcurrentcomponentsincreasedwithpostnatalage,approachingaplateauat3-5wk.Wefoundnosignificantchangesintherelativeproportionsorkineticsofanycomponentbetweenpostnatalweeks1and5,exceptthattheactivationtimeconstantforA-typecurrentwaslongerat1wk.TheputativeKv2-mediatedcomponentwasthelargestatallages.ImmunocytochemistryindicatedthatproteinexpressionforKv4.2,Kv4.3,Kv1.4,andKv2.1increasedbetween1wkand4-5wkofage.
GuanD., etal. (2011) PostnataldevelopmentofA-typeandKv1-andKv2-mediatedpotassiumchannelcurrentsinneocorticalpyramidalneurons. JNeurophysiol.PMID:21451062
Stromatoxin-sensitive,heteromultimericKv2.1/Kv9.3channelscontributetomyogeniccontrolofcerebralarterialdiameter
Cerebralvascularsmoothmusclecontractilityplaysacrucialroleincontrollingarterialdiameterand,thereby,bloodflowregulationinthebrain.AnumberofK(+)channelshavebeensuggestedtocontributetotheregulationofdiameterbycontrollingsmoothmusclemembranepotential(E(m))andCa(2+)influx.Previousstudiesindicatethatstromatoxin(ScTx1)-sensitive,Kv2-containingchannelscontributetothecontrolofcerebralarterialdiameterat80mmHg,buttheirpreciseroleandmolecularcompositionwerenotdetermined.Here,wetestedifKv2subunitsassociatewith‘silent’subunitsfromtheKv5,Kv6,Kv8orKv9subfamiliestoformheterotetramericchannelsthatcontributetocontrolofdiameterofratmiddlecerebralarteries(RMCAs)overarangeofintraluminalpressurefrom10to100mmHg.ThepredominantmRNAsexpressedbyRMCAsencodeKv2.1andKv9.3subunits.Co-localizationofKv2.1andKv9.3proteinsattheplasmamembraneofdissociatedsingleRMCAmyocyteswasdetectedbyproximityligationassay.ScTx1-sensitivenativecurrentofRMCAmyocytesandKv2.1/Kv9.3currentsexhibitedfunctionalidentitybasedonthesimilarityoftheirdeactivationkineticsandvoltagedependenceofactivationthatweredistinctfromthoseofhomomultimericKv2.1channels.ScTx1treatmentenhancedthemyogenicresponseofpressurizedRMCAsbetween40and100mmHg,butthistoxinalsocausedconstrictionbetween10and40mmHgthatwasnotpreviouslyobservedfollowinginhibitionoflargeconductanceCa(2+)-activatedK(+)(BK(Ca))andKv1channels.Takentogether,thisstudydefinesthemolecularbasisofKv2-containingchannelsandcontributestoourunderstandingofthefunctionalsignificanceoftheirexpressionincerebralvasculature.Specifically,ourfindingsprovidethefirstevidenceofheteromultimericKv2.1/Kv9.3channelexpressioninRMCAmyocytesandtheirdistinctcontributiontocontrolofcerebralarterialdiameteroverawiderrangeofE(m)andtransmuralpressurethanKv1orBK(Ca)channelsowingtotheirnegativerangeofvoltage-dependentactivation.
ZhongXZ., etal. (2010) Stromatoxin-sensitive,heteromultimericKv2.1/Kv9.3channelscontributetomyogeniccontrolofcerebralarterialdiameter. JPhysiol. PMID:20876197
ParticipationofKCNQ(Kv7)potassiumchannelsinmyogeniccontrolofcerebralarterialdiameter
KCNQgeneexpressionwaspreviouslyshowninvariousrodentbloodvessels,wheretheproductsofKCNQ4andKCNQ5,Kv7.4andKv7.5potassiumchannelsubunits,respectively,haveaninfluenceonvascularreactivity.TheaimofthisstudywastodetermineifsmallcerebralresistancearteriesoftheratexpressKCNQgenesandwhetherKv7channelsparticipateintheregulationofmyogeniccontrolofdiameter.Quantitativereversetranscriptionpolymerasechainreaction(QPCR)wasundertakenusingRNAisolatedfromratmiddlecerebralarteries(RMCAs)andimmunocytochemistrywasperformedusingKv7subunit-specificantibodiesandfreshlyisolatedRMCAmyocytes.KCNQ4messagewasmoreabundantthanKCNQ5=KCNQ1,butKCNQ2andKCNQ3messagelevelswerenegligible.Kv7.1,Kv7.4andKv7.5immunoreactivitywaspresentatthesarcolemmaoffreshlyisolatedRMCAmyocytes.Linopirdine(1microm)partiallydepressed,whereastheKv7activatorS-1(3and/or20microm)enhancedwhole-cellKv7.4(inHEK293cells),aswellasnativeRMCAmyocyteKvcurrentamplitude.TheeffectsofS-1werevoltage-dependent,withprogressivelossofstimulationatpotentialsof>15mV.AttheconcentrationsemployedlinopirdineandS-1didnotaltercurrentsduetorecombinantKv1.2/Kv1.5orKv2.1/Kv9.3channels(inHEK293cells)thatarealsoexpressedbyRMCAmyocytes.Incontrast,anotherwidelyusedKv7blocker,XE991(10microm),significantlyattenuatednativeKvcurrentandalsoreducedKv1.2/Kv1.5andKv2.1/Kv9.3currents.PressurizedarterialmyographywasperformedusingRMCAsexposedtointravascularpressuresof10-100mmHg.Linopirdine(1microm)enhancedthemyogenicresponseat20mmHg,whereastheactivationofKv7channelswithS-1(20microm)inhibitedmyogenicconstrictionat>20mmHgandreversedtheincreasedmyogenicresponseproducedbysuppressionofKv2-containingchannelswith30nmstromatoxin(ScTx1).ThesedatarevealanovelcontributionofKCNQgeneproductstotheregulationofmyogeniccontrolofcerebralarterialdiameterandsuggestthatKv7channelactivatingdrugsmaybeappropriatecandidatesforthedevelopmentofaneffectivetherapytoamelioratecerebralvasospasm.
ZhongXZ.,etal.(2010) ParticipationofKCNQ(Kv7)potassiumchannelsinmyogeniccontrolofcerebralarterialdiameter.JPhysiol.PMID:20624791
Membranepotential-dependentinactivationofvoltage-gatedionchannelsinalpha-cellsinhibitsglucagonsecretionfromhumanislets
OBJECTIVE:
Todocumentthepropertiesofthevoltage-gatedionchannelsinhumanpancreaticalpha-cellsandtheirroleinglucagonrelease.
RESEARCHDESIGNANDMETHODS:
Glucagonreleasewasmeasuredfromintactislets.[Ca(2+)](i)wasrecordedincellsshowingspontaneousactivityat1mmol/lglucose.Membranecurrentsandpotentialweremeasuredbywhole-cellpatch-clampinginisolatedalpha-cellsidentifiedbyimmunocytochemistry.
RESULT:
Glucoseinhibitedglucagonsecretionfromhumanislets;maximalinhibitionwasobservedat6mmol/lglucose.Glucagonsecretionat1mmol/lglucosewasinhibitedbyinsulinbutnotbyZnCl(2).GlucoseremainedinhibitoryinthepresenceofZnCl(2)andafterblockadeoftype-2somatostatinreceptors.Humanalpha-cellsareelectricallyactiveat1mmol/lglucose.InhibitionofK(ATP)-channelswithtolbutamidedepolarizedalpha-cellsby10mVandreducedtheactionpotentialamplitude.Humanalpha-cellscontainheteropodatoxin-sensitiveA-typeK(+)-channels,stromatoxin-sensitivedelayedrectifyingK(+)-channels,tetrodotoxin-sensitiveNa(+)-currents,andlow-thresholdT-type,isradipine-sensitiveL-type,andomega-agatoxin-sensitiveP/Q-typeCa(2+)-channels.Glucagonsecretionat1mmol/lglucosewasinhibitedby40-70%bytetrodotoxin,heteropodatoxin-2,stromatoxin,omega-agatoxin,andisradipine.The[Ca(2+)](i)oscillationsdependprincipallyonCa(2+)-influxviaL-typeCa(2+)-channels.Capacitancemeasurementsrevealedarapid(<50ms)componentofexocytosis.Exocytosiswasnegligibleatvoltagesbelow-20mVandpeakedat0mV.BlockingP/Q-typeCa(2+)-currentsabolisheddepolarization-evokedexocytosis.
CONCLUSIONS:
Humanalpha-cellsareelectricallyexcitable,andblockadeofanyionchannelinvolvedinactionpotentialdepolarizationorrepolarizationresultsininhibitionofglucagonsecretion.Weproposethatvoltage-dependentinactivationofthesechannelsunderliestheinhibitionofglucagonsecretionbytolbutamideandglucose.
RamracheyaR.,etal.(2010) Membranepotential-dependentinactivationofvoltage-gatedionchannelsinalpha-cellsinhibitsglucagonsecretionfromhumanislets.Diabetes.PMID:20547976
Voltage-gatedionchannelsinhumanpancreaticbeta-cells:electrophysiologicalcharacterizationandroleininsulinsecretion
OBJECTIVE:
Tocharacterizethevoltage-gatedionchannelsinhumanbeta-cellsfromnondiabeticdonorsandtheirroleinglucose-stimulatedinsulinrelease.
RESEARCHDESIGNANDMETHODS:
Insulinreleasewasmeasuredfromintactislets.Whole-cellpatch-clampexperimentsandmeasurementsofcellcapacitancewereperformedonisolatedbeta-cells.TheionchannelcomplementwasdeterminedbyquantitativePCR.
RESULTS:
Humanbeta-cellsexpresstwotypesofvoltage-gatedK(+)currentsthatflowthroughdelayedrectifying(K(V)2.1/2.2)andlarge-conductanceCa(2+)-activatedK(+)(BK)channels.BlockadeofBKchannels(usingiberiotoxin)increasedactionpotentialamplitudeandenhancedinsulinsecretionby70%,whereasinhibitionofK(V)2.1/2.2(withstromatoxin)waswithoutstimulatoryeffectonelectricalactivityandsecretion.Voltage-gatedtetrodotoxin(TTX)-sensitiveNa(+)currents(Na(V)1.6/1.7)contributetotheupstrokeofactionpotentials.InhibitionofNa(+)currentswithTTXreducedglucose-stimulated(6-20mmol/l)insulinsecretionby55-70%.Humanbeta-cellsareequippedwithL-(Ca(V)1.3),P/Q-(Ca(V)2.1),andT-(Ca(V)3.2),butnotN-orR-typeCa(2+)channels.BlockadeofL-typechannelsabolishedglucose-stimulatedinsulinrelease,whileinhibitionofT-andP/Q-typeCa(2+)channelsreducedglucose-induced(6mmol/l)secretionby60-70%.MembranepotentialrecordingssuggestthatL-andT-typeCa(2+)channelsparticipateinactionpotentialgeneration.BlockadeofP/Q-typeCa(2+)channelssuppressedexocytosis(measuredasanincreaseincellcapacitance)by>80%,whereasinhibitionofL-typeCa(2+)channelsonlyhadaminoreffect.
CONCLUSIONS:
Voltage-gatedT-typeandL-typeCa(2+)channelsaswellasNa(+)channelsparticipateinglucose-stimulatedelectricalactivityandinsulinsecretion.Ca(2+)-activatedBKchannelsarerequiredforrapidmembranerepolarization.Exocytosisofinsulin-containinggranulesisprincipallytriggeredbyCa(2+)influxthroughP/Q-typeCa(2+)channels.
BraunM.,etal.(2008) Voltage-gatedionchannelsinhumanpancreaticbeta-cells:electrophysiologicalcharacterizationandroleininsulinsecretion.Diabetes.PMID:18390794
Structuralbasisofbindingandinhibitionofnoveltarantulatoxinsinmammalianvoltage-dependentpotassiumchannels
Voltage-dependentpotassiumchannelKv2.1iswidelyexpressedinmammalianneuronsandwassuggestedresponsibleformediatingthedelayedrectifier(I(K))currents.Furtherinvestigationofthecentralroleofthischannelrequiresthedevelopmentofspecificpharmacology,forinstance,theutilizationofspidervenomtoxins.Mostofthesetoxinsbelongtothesamestructuralfamilywithashortpeptidereticulatedbydisulfidebridgesandshareasimilarmodeofaction.Hanatoxin1(HaTx1)fromaChileantarantulawasoneoftheearliestdiscussedtoolsregardingthisandhasbeenintensivelyappliedtocharacterizethechannelblockingnotthroughtheporedomain.Recently,morerelatednoveltoxinsfromAfricantarantulassuchasheteroscordratoxins(HmTx)andstromatoxin1(ScTx1)wereisolatedandshowntoactasgatingmodifierssuchasHaTxonKv2.1channelswithelectrophysiologicalrecordings.However,furtherinteractiondetailsareunavailableduetothelackofhigh-resolutionstructuresofvoltage-sensingdomainsinsuchmammalianKvchannels.Therefore,inthepresentstudy,weexploredstructuralobservationviamoleculardockingsimulationbetweentoxinsandKv2.1channelsbaseduponthesolutionstructuresofHaTx1andatheoreticalbasisofanindividualS3(C)helicalchannelfragmentincombinationwithhomologymodelingforothernoveltoxins.Ourresultsprovideprecisechemicaldetailsfortheinteractionsbetweenthesetarantulatoxinsandchannel,reasonablycorrelatingthepreviouslyreportedpharmacologicalpropertiestothethree-dimensionalstructuralinterpretation.Inaddition,itissuggestedthatcertainsubtlestructuralvariationsontheinteractionsurfaceoftoxinsmaydiscriminatebetweentherelatedtoxinswithdifferentaffinitiesforKvchannels.Evolutionarylinksbetweenspiderpeptidetoxinsanda“voltagesensorpaddles”mechanismmostrecentlyfoundinthecrystalstructureofanarchaebacterialK(+)channel,KvAP,arealsodelineatedinthispaper.
SchiauYS., etal. (2003) Structuralbasisofbindingandinhibitionofnoveltarantulatoxinsinmammalianvoltage-dependentpotassiumchannels. ChemResToxicol.PMID:14565763
NovelTarantulaToxinsforSubtypesofVoltage-DependentPotassiumChannelsintheKv2andKv4Subfamilies
Threenovelpeptideswiththeabilitytoinhibitvoltage-dependentpotassiumchannelsintheshab(Kv2)andshal(Kv4)subfamilieswereidentifiedfromthevenomoftheAfricantarantulasStromatopelmacalceata(ScTx1)andHeteroscodramaculata(HmTx1,HmTx2).Thethreetoxinsare34-to38-aminoacidpeptidesthatbelongtothestructuralfamilyofinhibitorcystineknotspiderpeptidesreticulatedbythreedisulfidebridges.ElectrophysiologicalrecordingsinCOScellsshowthatthesetoxinsactasgatingmodifierofvoltage-dependentK+channels.ScTx1isthefirsthigh-affinityinhibitoroftheKv2.2channelsubtype(IC50,21.4nM)tobedescribed.ScTx1alsoinhibitstheKv2.1channels,withanIC50of12.7nM,andKv2.1/Kv9.3heteromultimersthathavebeenproposedtobeinvolvedinO2sensinginpulmonaryarterymyocytes.Inaddition,itisthemosteffectiveinhibitorofKv4.2channelsdescribedthusfar,withanIC50of1.2nM.HmTxtoxinssharesequencesimilaritieswithboththepotassiumchannelblockertoxins(HmTx1)andthecalciumchannelblockertoxinomega-GsTxSIA(HmTx2).TheyinhibitpotassiumcurrentassociatedwithKv2subtypesinthe100to300nMconcentrationrange.HmTx2seemstobeaspecificinhibitorofKv2channels,whereasHmTx1alsoinhibitsKv4channels,includingKv4.1,withthesamepotency.HmTx1isthefirstdescribedpeptideeffectoroftheKv4.1subtype.Thosenoveltoxinsarenewtoolsfortheinvestigationofthephysiologicalroleofthedifferentpotassiumchannelsubunitsincellularphysiology.
EscoubasP.,etal.(2002) NovelTarantulaToxinsforSubtypesofVoltage-DependentPotassiumChannelsintheKv2andKv4Subfamilies.MolPharm.PMID:12065754
Smartox Biotechnolgy的多肽毒素产品如下：
1. 作用于钠离子通道(Sodium channel)的毒素
Toxin name | Catalog # | Target |
Phrixotoxin-3 | 13PHX003 | Selective blocker of Nav1.2 |
µ-conotoxin GIIIB | CON020 | Selective blocker of Nav1.4 |
µ-conotoxin CnIIIC | CON021 | Selective blocker of Nav1.4 |
μ-conotoxin PIIIA | 08CON006 | Selective blocker of Nav1.4 |
Jingzhaotoxin-III | 12JZH003 | Selective blocker of Nav1.5 |
ProTx-II | 07PTX002 | Selective blocker of Nav1.7 |
ProTx-II Biotin | 12PTB002 | Selective blocker of Nav1.7 |
ProTx-I | 12PTX001 | Blocker of Nav1.8, Nav1.2, Nav1.5, Nav1.7 |
Huwentoxin-I | 07HWT001 | Blocker of TTX-S |
Huwentoxin-IV | 08HWT002 | Blocker of TTX-S |
Hainantoxin-III | 13HTX003 | Blocker of TTX-S |
Hainantoxin-IV | 12HTX001 | Blocker of TTX-S |
GsAF-I | 12GSF001 | Blocker of TTX-S |
GsAF-II | 12GSF002 | Blocker of TTX-S |
2. 作用于钾离子通道(Potassium channel)的毒素
Toxin name | Catalog # | Target |
KCa channels | ||
Apamin 蜜蜂神经毒素 | 08APA001 | SK1, SK2, SK3 |
Charybdotoxin 蝎毒素 | 11CHA001 | KCa1.1, KCa3.1 - Kv1.2, Kv1.3, Kv1.6 |
Iberiotoxin | 12IBX001 | KCa1.1 |
Leiurotoxin 1 (Scyllatoxin) | 10LEI001 | SK1, SK2, SK3 |
Tamapin | 10TAM001 | SK1, SK2, SK3 |
Kaliotoxin-1 | 08KTX002 | BK, Kv1.1, Kv1.2, Kv1.3 |
Kv channels | ||
ShK | 08SHK001 | Kv1.3, Kv1.1, Kv1.4, Kv1.6 |
TMR-ShK | SAT001 | Kv1.3, Kv1.1 |
Margatoxin | 08MAG001 | Kv1.3 |
(Dap22)-ShK | 13SHD001 | Kv1.3 |
ADWX-1 | 13ADW001 | Kv1.3 |
HsTx1 | 08NEU001 | Kv1.3, Kv1.2 |
Agitoxin-2 | 13AGI002 | Kv1.3, Kv1.1 |
Maurotoxin | 08MAR001 | Kv1.2, KCa3.1 |
Guangxitoxin 1E | 11GUA002 | Kv2.1, Kv2.2 |
Stromatoxin 1 NEW | SCT01 | Kv2.1, Kv2.2 |
Kaliotoxin-1 | 08KTX002 | BK, Kv1.1, Kv1.2, Kv1.3 |
Charybdotoxin | 11CHA001 | KCa1.1, KCa3.1 - Kv1.2, Kv1.3, Kv1.6 |
Phrixotoxin-2 | PHX002 | Kv4.2, Kv4.3 |
AmmTx3 NEW | AMX001 | A-type potassium channels |
Inwardly rectifying potassium channels | ||
TertiapinQ | 08TER001 | Kir1.1, Kir3.1/3.4, Kir3.1/3.2-KCa1.1 |
hERG/Kv11.1 | ||
BeKm-1 | 13BEK001 | ERG1 |
3. 作用于钙离子通道(Calcium channel)的毒素
Toxin name | Catalog # | Target |
High voltage-gated Ca2+ channels | ||
ω-agatoxin IVA | 11AGA001 | P/Qtype |
ω-Conotoxin MVIIC | 08CON002 | P/Qtype, N-type |
ω-Conotoxin MVIIA | 08CON001 | N-type |
ω-Conotoxin GVIA | 08CON003 | N-type |
ω-Conotoxin SO3 | 08CON013 | N-type |
Huwentoxin I | 07HWT001 | N-type |
ProTx-II | 07PTX002 | T-type, L-type |
Intermediate voltage-gated Ca2+ channels | ||
SNX482 | 08SNX002 | R-type |
Low voltage-gated Ca2+ channels | ||
ProTx-I | 12PTX001 | T-type |
ProTx-II | 07PTX002 | T-type, L-type |
Ryanodine receptors | ||
Maurocalcine | 07PAU001 | Ryr1 |
4. 作用于氯离子通道(Chloride channel)的毒素
Toxin name | Catalog # | Target |
Chlorotoxin | 08CHL001 | Blocker of small conductance Cl- channels |
GaTx1 | 13GTX001 | Selective blocker of CFTR channel |
GaTx2 | 10GTX002 | Selective blocker of ClC-2 channel |
5. 作用于乙酰胆碱受体(Acetylcholine receptor)的毒素
Toxin name | Catalog # | Target |
α-conotoxin PeIA | 13CON017 | α9α10, α3β2 subunits |
α-Conotoxin PrXA | 13CON016 | α1/β1/ε/δ, α1/β1/γ/δ subunits |
Waglerin-1 | 12WAG001 | MusclenAChR |
α-conotoxin MI | 08CON012 | α1/δsubunits |
α-conotoxin GI | 08CON005 | α/δsite |
α-conotoxin IMI | 08CON011 | α7 homomeric nAChR |
α-conotoxin GID | CON019 | Blocker of α3β2, α7 and α4β2 nAChRs |
6. 含N-甲基-D-天冬氨酸NR2B
(NMDA, NR2B containing N-methyl-D-aspartate)
Conantokin-G
选择性、特异性抑制含NR2B的NMDAR。Conantokin-G能剂量依赖性抑制Ca2+内流，抑制NMDA诱导的兴奋性中毒效应。研究表明，在小鼠皮层神经元，Conantokin-G阻滞NMDA引发的电流信号的IC50值为480 nM。
7. 作用于酸敏感离子通道(ASIC channel, Acid-Sensing Ion Channel)的毒素
Toxin name | Catalog # | Target |
APETx2 | 07APE002 | Selective blocker of ASIC3 |
Psalmotoxin1/PcTx1 | 13PCT001 | Selective blocker of ASIC1a |
Ugr9-1 | 13UGR001 | Blocker of ASIC3 |
8. 作用于瞬时受体电位(TRP channel, transient receptor potential)的毒素
Toxin name | Catalog # | Target |
GsMTx4 | 08GSM001 | TRPC, TRPA |
Vanillotoxin3 | 10VAN003 | Activator of TRPV1 |
ProTx-I | 12PTX001 | Antagonist of TRPA1 |
9. 作用于嘌呤能通道(Purinergic channel)的毒素
Purotoxin-1
选择性抑制P2X3受体。100 nM Purotoxin-1 (PT-1)选择性抑制P2X3受体通道，在大鼠DRG神经元上，使用膜片钳实验表明：PT-1对电压门控通道和TRPV1均无抑制效应。10 µM ATP和100 µM α,β Methylene-ATP浓度下Purotoxin-1对P2X3受体有选择性作用，在该ATP浓度下Purotoxin-1对P2X2和杂化二聚体P2X2/3并无激动作用。Purotoxin-1对疼痛的潜在治疗作用。
10. 作用于其它膜受体通道(Others)的毒素
Smartox Biotechnology还提供其他类型的膜受体抑制剂：
Toxin name | Catalog # | Target |
Morphiceptin | 011CAS001 | Agonist of µ-opoid receptors |
Lys-conopressin G | 11CON14 | Vasopressin-like peptide |
GsMTx4 | 08GSM001 | Mechano sensitive ion channels |
Obtustatin | 10OBT001 | Blocks the binding of α1β1 integrin to collagen IV |
Rho-Conotoxin TIA | CON022 | Blocks α1-adrenergic receptor |
公司简介
Smartox Biotechnology是全球唯一一家专门生产动物毒液多肽毒素，用于细胞离子通道功能研究的生物医药公司。多肽毒素在生物制药领域具有重要的使用价值。
Smartox Biotechnology于2009年由来自Grenoble神经科学研究所(Grenoble Institute of Neuroscience)的Michel De Waard博士创立。Smartox Biotechnology专门研究动物毒液，制作合成多种毒液中的多肽成分（常称为毒素）。De Waard博士研究离子通道与毒素多肽的关系，尤其是鉴定、开发毒素多肽作为治疗性分子或细胞穿透肽(cell penetrating peptides, CPP)。其研究团队在毒液分离，药理性活性肽鉴定、富半胱氨酸肽定性、制作和优化等方面具有独特、丰富的经验。2010年，Smartox Biotechnolgy被法国研究部(Ministry of Research)授予“新兴企业OSEO奖(OSEO prize for emerging businesses)”。
总之，Smartox Biotechnolgy提供一系列高质量、具开创价值的多肽毒素。这些化合物在离子通道 研究中具有高的亲和性和选择性，是相应领域科学研究理想的生物毒素提供商和贴心的合作伙伴。
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