TheNav1.1voltage-gatedsodiumchannelisacriticalcontributortoexcitabilityinthebrain,wherepathologicallossoffunctionleadstosuchdisordersasepilepsy,Alzheimer’sdisease,andautism.Thisvoltage-gatedsodium(Nav)channelsubtypealsoplaysanimportantroleinmechanicalpainsignalingbyprimaryafferentsomatosensoryneurons.Therefore,pharmacologicmodulationofNav1.1representsapotentialstrategyfortreatingexcitabilitydisordersofthebrainandperiphery.InactivationisacomplexaspectofNavchannelgatingandconsistsoffastandslowcomponents,eachofwhichmayinvolveacontributionfromoneormorevoltage-sensingdomains.Here,weexploittheHm1aspidertoxin,aNav1.1-selectivemodulator,tobetterunderstandtherelationshipbetweenthesetemporallydistinctmodesofinactivationandaskwhethertheycanbedistinguishedpharmacologically.WeshowthatHm1ainhibitsthegatingmovementofthedomainIVvoltagesensor(VSDIV),hinderingbothfastandslowinactivationandle
ADIngtoanincreaseinNav1.1availabilityduringhigh-frequencystimulation.Incontrast,ICA-121431,asmall-moleculeNav1.1inhibitor,acceleratesasubsequentVSDIVgatingtransitiontoaccelerateentryintotheslowinactivatedstate,resultinginuse-dependentblock.FurtherevidenceforfunctionalcouplingbetweenfastandslowinactivationisprovidedbyaNav1.1mutantinwhichfastinactivationremovalhascomplexeffectsonslowinactivation.Takentogether,ourdatasubstantiatethekeyroleofVSDIVinNavchannelfastandslowinactivationanddemonstratethatthesegatingprocessesaresequentialandcoupledthroughVSDIV.ThesefindingsprovideinsightintoapharmacophoreonVSDIVthroughwhichmodulationofinactivationgatingcaninhibitorfacilitateNav1.1function.
Smartox生物素ProTx-I电压门控钠通道和T型Cav的阻断剂毒素I(ProTx-1;β-theraphotoxin-Tp1a) 是一种毒素,最初是从Prixopelma pruriens(秘鲁绿色天鹅绒狼蛛)的毒液中分离出来的。此毒素可逆地抑制抗河豚毒素(TTX)的通道 Na v 1.8(IC 50 = 27 nM)和 Na v 1.2,Na v 1.5和Na v 1.7 ,IC 50 值为50至100 nM。此外, ProTx-I 改变了T型Ca v 3.1通道的电压依赖性活动 (IC 50 = 50 nM),而不会影响灭活的电压依赖性。生物素ProTx-I是ProTx-I的生物素标签版本。