GaTx2 (gatingmodifierofanionchannels2)wasisolatedfromthevenomofLeiurusquinquestriatushebraeus. GaTx2 isthemostpotentpeptideinhibitorof ClC-2(CLCN2)chloridechannel everdescribed.Kd valueiscloseto20pM. GaTx2slowsClC-2activationbutwithoutalteringchannelconductance.Theeffectisvoltage-dependent.ThisinhibitoryeffectwashighlightedonrabbitClC-2channelsexpressedinoocytes. IthasnoeffectonClC-0,ClC-1,ClC-3,ClC-4,CFTR,GABAC,XenopusClCa,ShakerBorKv1.2channels.Structurally,GaTx2iscomposedoftwoβ-strandsandoneα-helix.ThispeptideisalsocalledLeiuropeptideII.Bears89,93and96%identitywithOdK1,neurotoxinPO1andleiuropeptideIII,respectively.
Description:
AAsequence:Val-Ser-Cys3-Glu-Asp-Cys6-Pro-Asp-His-Cys10-Ser-Thr-Gln-Lys-Ala-Arg-Ala-Lys-Cys19-Asp-Asn-Asp-Lys-Cys24-Val-Cys26-Glu-Pro-Ile-OH
Disulfidebondsbetween:Cys3-Cys19,Cys6-Cys24,andCys10-Cys26
Length(aa): 29
Formula: C125H199N39O47S6
MolecularWeight: 3191.25Da
Appearance:Whitelyophilizedsolid
Solubility: waterandsalinebuffer
CASnumber: notavailable
Source: Synthetic
Purityrate: >98%
Reference:
DualactivationofCFTRandCLCN2bylubiprostoneinmurinenasalepithelia
Multiplesodiumandchloridechannelsontheapicalsurfaceofnasalepithelialcellscontributetopericiliaryfluidhomeostasis,afunctionthatisdisruptedinpatientswithcysticfibrosis(CF).AmongthesechannelsisthechloridechannelCLCN2,whichhasbeenstudiedasapotentialalternativechlorideeffluxpathwayintheabsenceofCFTR.Theobjectofthepresentstudywastousethenasalpotentialdifferencetest(NPD)toquantifyCLCN2functioninanepithelial-directedTetOnCLCN2transgenicmousemodel(TGN-K18rtTA-hCLCN2)byusingtheputativeCLCN2pharmacologicalagoNISTlubiprostoneandpeptideinhibitorGaTx2.LubiprostonesignificantlyincreasedchloridetransportintheCLCN2-overexpressingmicefollowingactivationofthetransgenebydoxycycline.ThisresponsetolubiprostonewassignificantlyinhibitedbyGaTx2afterCLCN2activationinTGN-CLCN2mice.Cftr(-/-)andClc2(-/-)miceshowedhyperpolarizationindicativeofchlorideeffluxinresponsetolubiprostone,whichwasfullyinhibitedbyGaTx2andCFTRinhibitor172+GlyH-101,respectively.OurstudyrevealslubiprostoneasapharmacologicalactivatorofbothCFTRandCLCN2.OverexpressionandactivationofCLCN2leadstoimprovedmouseNPDreADIngs,suggestingitisavailableasanalternativepathwayforepithelialchloridesecretioninmurineairways.TheutilizationofCLCN2asanalternativechlorideeffluxchannelcouldprovideclinicalbenefittopatientswithCF,especiallyifthepharmacologicalactivatorisadministeredasanaerosol.
EricE,etal.(2013)DualactivationofCFTRandCLCN2bylubiprostoneinmurinenasalepithelia. AmJPhysiolLungCellMolPhysiol. PMID:23316067
IsolationandcharacterizationofahighaffinitypeptideinhibitorofClC-2chloridechannels
TheClCproteinfamilyincludesvoltage-gatedchloridechannelsandchloride/protonexchangers.Ineukaryotes,ClCproteinsregulatemembranepotentialofexcitablecells,contributetoepithelialtransport,andaidinlysosomalacidification.Althoughstructure/functionstudiesofClCproteinshavebeenaidedgreatlybytheavailablecrystalstructuresofabacterialClCchloride/protonexchanger,theavailABIlityofusefulpharmacologicaltools,suchaspeptidetoxininhibitors,haslaggedfarbehindthatoftheircationchannelcounterparts.Herewereporttheisolation,fromLeiurusquinquestriatushebraeusvenom,ofapeptidetoxininhibitoroftheClC-2chloridechannel.Thistoxin,GaTx2,inhibitsClC-2channelswithavoltage-dependentapparentK(D)ofapproximately20pm,makingitthehighestaffinityinhibitorofanychloridechannel.GaTx2slowsClC-2activationbyincreasingthelatencytofirstopeningbynearly8-foldbutisunabletoinhibitopenchannels,suggestingthatthistoxininhibitschannelactivationgating.Finally,GaTx2specificallyinhibitsClC-2channels,showingnoinhibitoryeffectonabatteryofothermajorclassesofchloridechannelsandvoltage-gatedpotassiumchannels.GaTx2isthefirstpeptidetoxininhibitorofanyClCprotein.ThehighaffinityandspecificitydisplayedbythistoxinwillmakeitaverypowerfulpharmacologicaltooltoprobeClC-2structure/function.
ThompsonCH, etal.(2009)IsolationandcharacterizationofahighaffinitypeptideinhibitorofClC-2chloridechannels.JBiolChem. PMID:23316067
