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1、INTRACELLULARRECEPTORSTheintracellular(nuclear)receptorsuperfamilySteroidhormones,thyroidhormones,retinoidsandvitaminDIntracellularreceptorHYDROPHOBIC:Non-polarmoleculesGasesSteroidsRegulationoftranscriptionactivityRegulatorymechanismsvaryHeterodimericreceptors-exclusi
2、velynuclear;withoutligand,represstranscriptionbybindingtotheircognatesitesinDNAHomodimericreceptors-mostlycytoplasmic(withoutligands)&hormonebindingleadstonucleartranslocationofreceptorsWithoutligand-aggregationofreceptorwithinhibitorproteins(egHsp90)Steroidhormonesare
3、oftenrequiredtodimerizewithapartnertoactivategenetranscriptionReceptorsforvitaminD,retinoicacidandthyroidhormonebindtoresponsiveelementsasheterodimersSecondcomponentoftheheterodimerisRXRmonomer(i.e,RXR-RAR;RXR-VDR)Specificitiesofsomereceptors…Intracellularsignalmolecul
4、essmall,lipid-solublemoleculessuchassteroidhormones,retinoids,thyroidhormones,VitaminD.(madefromcholesterol)Thesemoleculesdiffusethroughplasmaandnuclearmembranesandinteractdirectlywiththetranscriptionfactorstheycontrol.6LipophilicHormonesCirculationinthebloodboundtotra
5、nsportproteinsDissociationfromcarrierattargetcellsActioninthecell-Passthroughthecellmembraneandbindtoanintracellularreceptor,eitherinthecytoplasmorthenucleus-Hormone-receptorcomplexbindstohormoneresponseelementsinDNA-Regulategeneexpression7ReceptorBloodplasmaProteinLip
6、ophilichormonesmRNADNAHormoneresponseelement1.Hormonepassesthroughplasmamembrane2.Insidetargetcellthehormonebindstoareceptorproteininthecytoplasmornucleus3.Hormone-receptorcomplexbindstohormoneresponseelementonDNA,regulatinggenetranscription4.Proteinsynthesis5.Changein
7、proteinsynthesisiscellularresponseCytoplasmPlasmamembraneNucleusCopyright©TheMcGraw-HillCompanies,Inc.Permissionrequiredforreproductionordisplay.SteroidHormonesSTEROIDHORMONES:-sexsteroids(estrogen,progesterone,testosterone)-corticosteroids(glucocorticoidsandmineralcor
8、ticoids)OTHERHORMONES Thyroidhormone,vitaminD3,andretinoicacidhavedifferentstructureandfunctionbutsharethesamemechani
