Seeonlineversionforlegendandreferences.162Cell132,January11,2008©2008ElsevierInc.DOI10.1016/j.cell.2007.12.026SnapShot:MacroautophagyBethLevine1andGuidoKroemer21UTSouthwesternMedicalCenter,Dallas,Texas;2INSERM,InstitutGustaveRoussy,Villejuif,France162.e1Cell132,January11,2008©2008ElsevierInc.DOI10.1016/j.cell.2007.12.026(Middle)CellularEventsinMacroautophagyMacroautophagy(hereafterreferredtoasautophagy)isacatabolicprocessinwhichportionsofthecytoplasmaresequesteredwithindouble-ormultimembranedvesiclestermedautophagosomesandthendeliveredtolysosomesforbulkdegradation.Theinitialphasesofmacroautophagyconsistoftheformationofaphago-phore,whichisalsocalledanisolationmembrane(vesiclenucleationstep),theengulfmentofcytoplasmicmaterial—cytosoland/ororganelles—bythephagophore,theelongationofthephagophoremembrane,andfusionofitsedgestoformtheautophagosome(vesicleelongationandcompletionsteps).Inyeast,thepre-au-tophagosomalstructure(PAS),consistingofthephagophoreoritsprecursorandautophagy(Atg)proteins,isthoughttobethesiteforassemblyoftheautophago-some.Theoutermembraneoftheautophagosomefuseswiththevacuoleinyeasttoformtheautophagicbodyorwiththelysosomeinmammaliancellstoformtheautolysosome,whichisalsocalledtheautophagolysosome(dockingandfusionsteps).Insidetheautophagicbody/autolysosome,theluminalmaterialincludingtheinternalmembraneisdegradedbyvacuolar/lysosomehydrolases(vesiclebreakdownanddegradationsteps).Theresultingmacromoleculesarereleasedthroughpermeasesandrecycledinthecytosol.Alternatively(notdepictedhere),theautophagosomemayfusewithanendosometoformanamphisome,priortofusionwiththelysosome.(LeftandRight)MolecularEventsinAutophagyDepictedarethemolecularpathwaysofautophagyinyeast(right)andmammals(humanormouse)(left).Althoughmanyoftheregulatorsandexecutorsofyeastautophagyhaveorthologsinmammals(blueshadedovals),notallyeastautophagy(ATG)geneshaveaknownmammalianequivalentorviceversa.Theautophagicmachineryinothermodeleukaryoticorganisms(e.g.,Dictyosteliumdiscoideum,Arabidopsisthal...
