Nerve-dependent changes in content of ribosomes, polysomes, and nascent peptides in newt limb regenerates☆

[摘要] Regenerationofanewtlimbrequiresaconstantsupplyofadequateamountsofaneuronalcontributionattheamputationsite.Denervationduringtheearlystagesofregenerationprecludesitsgrowthandmorphogenesis.Ithasbeenreportedthatdenervationofaregeneratinglimblowerstheefficiencyofincorporationofradioactiveaminoacidsto60%ofcontralateralcontrollevels.Togainmoreinsightintothemechanismresponsibleforthisdecrease,weexaminedtheeffectsofdenervationonthesizedistributionandquantityofregeneratepolysomes.Wecharacterizedthe[35S]methionine-labelednascentpeptidyl-tRNAfrompolysomesbyhydroxyapatitechromatography.Moreover,weshowthatthelabelednascentpeptidesonpolysomescanserveasameasuretoquantitatetherelativeamountsofribosomesonpolysomesandtherelativesizeofthetranslationalmachinery.Thus,wereportthat[35S]methionine-labelednascentpolypeptidesonpolysomesfromdenervatedregeneratescontainabout48%lessradioactivitythanthosefromcontrols.Despitedecreasedincorporationof[35S]methionineintonascentpeptides,therelativedistributionofradioactivityacrosslinearsucrosegradientsisnotsignificantlyalteredbydenervation.Studiesofpolysomeslabeledwith[3H]uridinepriortodenervationindicatethatribosomecontentisdepressedbydenervation.Ourresultssuggestthatthenerve-dependentdecreaseinproteinsynthesisismediatedbydecreasingthenumberofribosomesactiveinproteinsynthesis.Inaddition,similaritiesintheratiosoffreemonosomestopolysomesandtherelativesizedistributionofpolypeptidesbetweendenervatedandinnervatedregeneratesindicatethatindenervatedregeneratesthenumberoftranslatablemRNAmoleculesdecreasesinacoordinatemannerwiththenumberofribosomesactiveinproteinsynthesis.

[学科分类] 生物科学（综合）