《离子通道生物学》课程教学课件（英文讲稿）Cl- channels & ligan‐gated channels

Cl- channels &ligan-gatedchannelsCheng Long, chenglong_scnu@qq.comSchool of Life Sciences, South China Normal UniversityMar. 27, 20121933華南師范大学INIVERSITYSOUTH CHINANORMAL

Cheng Long, chenglong_scnu@qq.com School of Life Sciences, South China Normal University Mar. 27, 2012 Cl- channels & ligan ‐gated channels

The outline...Required Readings:JentschTJ,SteinV,WeinreichF,ZdebikAA.Molecularstructureandphysiological function of chloride channels.Physiol Rev.2002,82(2):503-568.Verkman AS, Galietta LJ.Chloridechannels as drug targets.Nat Rev DrugDiscoV.2009,8(2):153-171BenarrochEE.(2011)NMDAreceptors:recentinsightsandclinicalcorrelations.Neurology.76(20):1750-1757LuscherB,FuchsT,KilpatrickCL.(2011)GABAAreceptortrafficking-mediatedplasticityofinhibitorysynapses.Neuron.70(3):385-409.EdwardO.Mann,OlePaulsen(2oo7)RoleofGABAergicinhibitioninhippocampalnetworkoscillations.TrendsinNeurosciences.3o(7):343-349.Further Readings:DuranC,ThompsonCH,XiaoQ,HartzellHC.(2010)Chloridechannels:oftenenigmatic,rarelypredictable.AnnuRevPhysiol.72:95-121.LeeHK,KirkwoodA.(2011)AMPAreceptorregulationduringsynapticplasticity in hippocampus and neocortex.Semin Cell DevBiol.22(5):514-520

The outline. Required Readings: Jentsch TJ, Stein V, Weinreich F, Zdebik AA. Molecular structure and physiological function of chloride channels. Physiol Rev. 2002, 82(2): 503-568. Verkman AS, Galietta LJ. Chloride channels as drug targets. Nat Rev Drug Discov. 2009, 8(2): 153-171. Benarroch EE. (2011) NMDA receptors: recent insights and clinical correlations. Neurology. 76(20): 1750-1757. Luscher B, Fuchs T, Kilpatrick CL. (2011) GABAA receptor trafficking-mediated plasticity of inhibitory synapses. Neuron. 70(3): 385-409. Edward O. Mann, Ole Paulsen (2007) Role of GABAergic inhibition in hippocampal network oscillations. Trends in Neurosciences. 30(7): 343- 349. Further Readings: Duran C, Thompson CH, Xiao Q, Hartzell HC. (2010) Chloride channels: often enigmatic, rarely predictable. Annu Rev Physiol. 72: 95-121. Lee HK, Kirkwood A. (2011) AMPA receptor regulation during synaptic plasticity in hippocampus and neocortex. Semin Cell Dev Biol. 22(5): 514-520

The outline...This class will cover:AnionchannelsOutsidecellTypes&structureofCl-channelsFunction & classification of ClchannelsMembraneRegulation&disordersofClchannelsInsidecellNMDACarboxyterminusGABA

The outline. This class will cover:  Anion channels  Types & structure of Cl- channels  Function & classification of Cl￾channels  Regulation & disorders of Cl￾channels  NMDA  GABA

IntroductionAnionchannelsareproteinaceousporesinbiologicalmembranesthat allowthe passivediffusionof negativelychargedionsalongtheirelectrochemical gradient.Althoughthesechannelsmayconductotheranions(e.g,IorNO,)betterthanCl,theyareoftencalledClchannelsbecauseClis the most abundant anion in organisms and hence is thepredominant permeating species under most circumstancesClchannel gatingmaydependonthetransmembranevoltage(in voltage-gated channels),on cell swelling,on thebinding ofsignaling molecules (as in ligand-gated anion channels ofpostsynapticmembranes),onvariousions [e.g.,anions,Ht(pH)orCa2+,onthephosphorylationof intracellularresiduesbyvarious protein kinases, or on the binding orhydrolysis of ATP

Introduction  Anion channels are proteinaceous pores in biological membranes that allow the passive diffusion of negatively charged ions along their electrochemical gradient.  Although these channels may conduct other anions (e.g., I- or NO3- ) better than Cl-, they are often called Cl- channels because Cl- is the most abundant anion in organisms and hence is the predominant permeating species under most circumstances.  Cl- channel gating may depend on the transmembrane voltage (in voltage-gated channels), on cell swelling, on the binding of signaling molecules (as in ligand-gated anion channels of postsynaptic membranes), on various ions [e.g., anions, H+ (pH), or Ca2+, on the phosphorylation of intracellular residues by various protein kinases, or on the binding or hydrolysis of ATP

Where are anion channelsencountered?Anionchannels were detected almosteverywhereInsynaptic vesiclesfrom rat brainandfromTorpedoelectricorgan,voltage-dependent anion channels of intermediateconductance(10-100pS)werefound.ThesechannelswerepresentineverysynapticvesicleReconstitutionofendoplasmicreticulummembranesfromrathepatocytesyieldedalarge-conductance(150-200pS)anionchannel,which wasalso voltage dependent.A different type ofanionchannelhasbeenfoundinsheepbrainendoplasmicreticulum membranes,where it is colocalized withcalciumreleasechannelsAnanionchannelintheGolgicomplexwascharacterizedwhichwaspresentevenintheabsenceofproteintranslationindicatingthat these channels are not en routetothe plasmamembrane,butendogenous tothis compartment

Where are anion channels encountered? Anion channels were detected almost everywhere.  In synaptic vesicles from rat brain and from Torpedo electric organ, voltage-dependent anion channels of intermediate conductance (10–100 pS) were found. These channels were present in every synaptic vesicle.  Reconstitution of endoplasmic reticulum membranes from rat hepatocytes yielded a large-conductance (150–200 pS) anion channel, which was also voltage dependent. A different type of anion channel has been found in sheep brain endoplasmic reticulum membranes, where it is colocalized with calcium release channels.  An anion channel in the Golgi complex was characterized, which was present even in the absence of protein translation, indicating that these channels are not en route to the plasma membrane, but endogenous to this compartment

AnionexchangeproteinsSLC4A1 (AE1):Erythrocyteband3proteinMajor integral glycoprotein in erythrocyte membrane·Polymorphisms determine Diego blood groupDiseases:Spherocytosis;Ovalocytosis;Renaltubularacidosis;HypokalemicperiodicparalysisOtherSLC4A2:Anionexchanger;Choroidplexus,Gl&OtherSLC4A3:Anionexchanger;Cardiac&BrainSLC4A4:NaBicarbonatecotransporter;Renal;Renaltubularacidosis,glaucoma,cataracts,&band keratopathySLC4A5:NaBicarbonatecotransporter;PancreasSLC4A6:NaBicarbonatecotransporter;Retina

Anion exchange proteins  SLC4A1 (AE1): Erythrocyte band 3 protein  Major integral glycoprotein in erythrocyte membrane  Polymorphisms determine Diego blood group  Diseases: Spherocytosis; Ovalocytosis; Renal tubular acidosis; Hypokalemic periodic paralysis  Other  SLC4A2: Anion exchanger; Choroid plexus, GI & Other  SLC4A3: Anion exchanger; Cardiac & Brain  SLC4A4: Na Bicarbonate cotransporter; Renal; Renal tubular acidosis, glaucoma, cataracts, & band keratopathy  SLC4A5: Na Bicarbonate cotransporter; Pancreas  SLC4A6: Na Bicarbonate cotransporter; Retina

Anion exchange proteinsOtherSLC17A5(Sialin):Salla syndrome(Sialicacid storage)SLC26A3:Down-regulatedinadenoma(DRA)SulfatetransporterCongenitalchloridediarrheaSLC26A4:TransporterofChloride&lodideNon-syndromic deafness, congenital (DFNB4)PendredsyndromeEnlargedvestibularaqueductsyndrome

Anion exchange proteins  Other  SLC17A5 (Sialin): Salla syndrome (Sialic acid storage)  SLC26A3: Down-regulated in adenoma (DRA)  Sulfate transporter  Congenital chloride diarrhea  SLC26A4: Transporter of Chloride & Iodide  Non-syndromic deafness, congenital (DFNB4)  Pendred syndrome  Enlarged vestibular aqueduct syndrome

Voltagedependentanionselectivechannelproteins(VDAC)Location:Outer mitochondrial membrane,inner mitochondrialmembrane,plasmamembraneFunctionsChannelsforsmallhydrophilicmoleculesTranslocationofadeninenucleotidesthroughoutermitochondrialmembraneBCL2proteinsbindtoVDAC:Regulatemitochondrialmembranepotential &releaseof cytochromecduringapoptosisMitochondrial binding sitefor:Hexokinase(HK1);Glycerolkinase

Voltage dependent anion selective channel proteins (VDAC)  Location: Outer mitochondrial membrane, inner mitochondrial membrane, plasma membrane  Functions  Channels for small hydrophilic molecules  Translocation of adenine nucleotides through outer mitochondrial membrane  BCL2 proteins bind to VDAC: Regulate mitochondrial membrane potential & release of cytochrome c during apoptosis  Mitochondrial binding site for: Hexokinase (HK1); Glycerol kinase

VDACVDAC1Pathwayformovementofadeninenucleotidesthroughoutermitochondrial membraneMitochondrial binding site forhexokinase and glycerol kinaseVDAC2Openconformation:Atloworzeromembranepotential;WeakanionselectivityClosedconformation:Atpotentialsabove 30-4o mV;Cation-selectiveVDAC3Highexpressionintestis●NullmiceSpermmotility:ReducedMuscle:Mitochondriaabnormallyshaped,Respiratorychaincomplex activityreducedVDAC4

VDAC  VDAC1  Pathway for movement of adenine nucleotides through outer mitochondrial membrane  Mitochondrial binding site for hexokinase and glycerol kinase  VDAC2  Open conformation: At low or zero membrane potential; Weak anion selectivity  Closed conformation: At potentials above 30-40 mV; Cation￾selective  VDAC3  High expression in testis  Null mice  Sperm motility: Reduced  Muscle: Mitochondria abnormally shaped, Respiratory chain complex activity reduced  VDAC4

AniontransporterOrganicaniontransporter(OATP)Nat-independent transport of organic anions,e.g.bileacidsCanalicular multispecific organic aniontransporter(CMOAT)Dubin-JohnsonSyndromeSulfateaniontransporter

Anion transporter  Organic anion transporter (OATP)  Na +-independent transport of organic anions, e.g. bile acids  Canalicular multispecific organic anion transporter (cMOAT)  Dubin-Johnson Syndrome  Sulfate anion transporter