Cell-to-Cell Signaling

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1、NocellisanislandòCellscommunicatewitheachotheròCellssendandreceiveinformation(signals)òInformationisrelayedwithincelltoproduceaCell-to-CellSignalingresponse(signaltransduction)ReceptorsSignalingprocessLifeisnoteasyòRecognitionofsignalòTheeffectsofactivationofcellsurfacereceptorsòRecept

2、orsaremorecomplicatedthanasimplestep-by-òTransductionstepcascadeòChangeofexternalsignalintointracellularmessageòExtensivenetworkingandcrosstalkòEffectòBynomeanssignalingisalineareventòModificationofcellbehavioròKeyisintegrationRecognitionTransductionòPerformedbyreceptorsòActivatedrecep

3、torinteractswithotherintracellularsignalingmoleculesandòLigandwillproduceòDirectlychangescellularactivityresponseonlyincellsorthathavereceptorsòProducessomeintermediates(secondmessengers)forthisparticularthatchangecellularactivityligandòEachcellhasaspecificsetofreceptors1Cellulareffect

4、sWhysocomplicated?òMetabolismòAmplificationòGeneexpressionòReliablityòGrowthanddifferentiation(cellcycle)òRedundanceòSecretionòStructure(cytoskeleton)ReceptorsReceptorsòMoleculesspecializedinrecognizingsignalsòLigand–substancethatbindstoreceptorwithòCanbeinsidethecellorouthighaffinityò

5、Specificforasignal(theywillrecognizeonlyaòBindingoftheligandproducesbiologicalresponsesignalthattheyaremadefor)òLigandscanbeendogenousorexogenousòEnergyfromthesignal(stimulus)orligandòAgonist–biologicalresponseofthesametypeasbindingaltersthestructureofthereceptortheendogenousligand(can

6、besmaller)òAntagonist–bindsandblockstheresponseTobeareceptoramoleculeDefinitionofareceptoròHastohaveanendogenousligandòMoleculeswithinoronthesurfaceoftargetcellsòHastobinditwithhighaffinity(strength)towhichasubstanceendogenoustotheorganismattachesitselfwithhighaffinityandòHastorecogniz

7、ethebiologicallyactiveligandspecificityasanessentialstepinmodifyingfromothersimilarmolecules(specificity)cellularfunctionòHastoproducethebiologicalresponseAlltheconditionshavetobemet!!!2CharacterizationofthereceptorsbasedonlocalizationIntracellularreceptorsòIntracellularreceptorsòIfa