
Human CD40 is a member of the tumor necrosis factor (TNF) receptor family and is present on all B cells except plasma cells. CD40 is also found on some epithelial cells, carcinomas and lymphoid dendritic cells. CD40 plays an important role in B cell activation and the interaction with its ligand CD154 (CD40 Ligand) is essential for isotype switching (3).
Isotype: Murine IgG1
Immunogen: Murine L cells transfectants expressing human CD40
Specificity: Antibody BE-1 recognizes the CD40 molecule of about 44 kd (1, 2).
Functional Application: Binding of cross linked BE-1 will partially activate B cells.
References:
1. C.L. Law, B. Wormann & T.W. LeBien, (1990) Leukemia 4: 732-738.
2. Leukocyte Typing IV (W. Knapp, et al, eds.) Oxford University Press, Oxford, (1989) p. 90-91.
3. T.A. Foy, et al, (1996) Annu Rev Immunol 14:591-617.
4. M.R. Kuhné , et al, (1997) J Exp Med 186:337-342.
ebiomall.com






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QianWang,JessamyTiffen,CharlesG.Bailey,MelanieL.Lehman,WilliamRitchie,LadanFazli,CynthiaMetierre,Yue(Julie)Feng,EstelleLi,MartinGleave,GrantBuchanan,ColleenC.Nelson,JohnE.J.Rasko,JeffHolst
Correspondenceto:JeffHolst,PhD,OriginsofCancerLaboratory,LockedBag6,Newtown,NSW2042Australia.(e-mail:j.holst@centenary.org.au).
BackgroundL-typeaminoacidtransporters(LATs)uptakeneutralaminoacidsincludingL-leucineintocells,stimulatingmammaliantargetofrapamycincomplex1signalingandproteinsynthesis.LAT1andLAT3areoverexpressedatdifferentstagesofprostatecancer,andtheyareresponsIBLeforincreasingnutrientsandstimulatingcellgrowth.
MethodsWeexaminedLAT3proteinexpressioninhumanprostatecancertissuemicroarrays.LATfunctionwasinhibitedusingaleucineanalog(BCH)inandrogen-dependentand-independentenvironments,withgeneexpressionanalyzedbymicroarray.APC-3xenograftmousemodelwasusedtostudytheeffectsofinhibitingLAT1andLAT3expression.ResultswereanalyzedwiththeMann-WhitneyUorFisherexacttests.Allstatisticaltestsweretwo-sided.
ResultsLAT3proteinwasexpressedatallstagesofprostatecancer,withastatisticallysignificantdecreaseinexpressionafter4–7monthsofneoadjuvanthormonetherapy(4–7monthmean=1.571;95%confidenceinterval=1.155to1.987vs0month=2.098;95%confidenceinterval=1.962to2.235;P=.0187).InhibitionofLATfunctionledtoactivatingtranscriptionfactor4–mediatedupregulationofaminoacidtransportersincludingASCT1,ASCT2,and4F2hc,allofwhichwerealsoregulatedviatheandrogenreceptor.LATinhibitionsuppressedM-phasecellcyclegenesregulatedbyE2Ffamilytranscriptionfactorsincludingcriticalcastration-resistantprostatecancerregulatorygenesUBE2C,CDC20,andCDK1.InsilicoanalysisofBCH-downregulatedgenesshowedthat90.9%arestatisticallysignificantlyupregulatedinmetastaticcastration-resistantprostatecancer.Finally,LAT1orLAT3knockdowninxenograftsinhibitedtumorgrowth,cellcycleprogression,andspontaneousmetastasisinvivo.
ConclusionInhibitionofLATtransportersmayprovideanoveltherapeutictargetinmetastaticcastration-resistantprostatecancer,viasuppressionofmammaliantargetofrapamycincomplex1activityandM-phasecellcyclegenes.
L-typeaminoacidtransporters(LATs)supplycellswithlargeneutralaminoacids,whicharenotonlyrequiredforproteinsynthesisbutalsocontributetovarioussignalingpathways.Intracellularleucinelevelsaresensedbytheleucyl-transferRNAsynthetase,previouslyknowntocatalyzetheadenosinetriphosphate–dependentligationofL-leucinetotransferRNAduringproteinsynthesis(1,2).Leucyl-transferRNAsynthetaseactivatestheRagguanosinetriphosphatasecomplexandbindstoRaptortoactivatemammaliantargetofrapamycincomplex1(mTORC1)signalingonthesurfaceoflysosomes(1–3).Inthiswayleucineisnotonlyanessentialaminoacidbutactsasarate-limitingsignalingmoleculeinthemTORC1pathway.
Incellsdeprivedofaminoacids,thereisanaccumulationofunchargedtransferRNA,whichbindstoandactivatesthegeneralcontrolnonrepressed2(GCN2)kinase.Inturn,GCN2phosphorylatesthetranslationinitiationfactor2α(eIF2α)onserine51,triggeringtranslationalupregulationofactivatingtranscriptionfactor(ATF)4(4).ATF4itselfupregulatestheexpressionofaminoacidtransportersasameansofrestoringintracellularaminoacidlevels(5).Therefore,understandinghowaminoacidtransportersregulateintracellularleucinelevels,andgeneratingnovelinhibitorsofthesetransporters,mayleadtopotentsuppressorsofmTORC1signaling.
ThetwodistinctfamiliesofLATsare1)solutecarrier7(SLC7)members(LAT1/SLC7A5andLAT2/SLC7A8),whichmediateNa+-independentneutralaminoacidexchangeasheterodimerswiththe4F2cell-surfaceantigenheavychain(4F2hc/SLC3A2/CD98)glycoprotein(6,7);and2)SLC43proteins(LAT3/SLC43A1andLAT4/SLC43A2)thatmediateNa+-independentuniportofneutralaminoacids(8,9).AlthoughtheexpressionofeachLATmembervariesdramaticallyindifferenttissues,thesetransportersarecommonlyupregulatedincancer.IncreasedLAT1expressionhasbeendetectedinlungcancer,coloncancer,breastcancer,headandneckcancer,genitalcancers,andsofttissuesarcomas(10–12).WeandothershaveshownthatLAT1andLAT3areoverexpressedinprostatecancer(11–14),withLAT1expressionincreasedinmetastasiscomparedwithprimarycancer(10,12).
WehypothesizedthatinhibitionofLAT1andLAT3mayofferaneffectivetherapeuticapproachforprostatecancer.
感觉这样的提问是没有意义的
还是自己找下资料吧
微生物吸收营养和排出废弃物都需要通过细胞膜。而细胞膜是磷脂双分子层结构,无论是亲水物质还是疏水物质都无法通过细胞膜。
细胞膜上镶嵌有蛋白质,叫转运蛋白。蛋白质既有疏水基团,又有亲水基团,正是靠蛋白质的这种特殊结构,能够与两类物质结合,并通过蛋白质结构的细微变化,把这两类物质运送到细胞膜的另一侧。
所以,微生物吸收营养物质必须用镶嵌在细胞膜上的转运蛋白来实现。
另外在八版生理248页第二段,近端小管后半段氯离子通过氯离子碳酸氢根交换体被重吸收,此时小管液中氯离子浓度大于周围组织液氯离子浓度,所以也有细胞旁途径顺浓度被动重吸收,然而资料上的总结和题目里都是说氯离子在近端小管的重吸收为被动重吸收,感觉有些糊涂。希望来个大神指点一二。

