Intersegmental muscles (ISMsi of ilic ninth, Manduca secta are a useful model ior the biochemical events inediatiiif; profjiiiiiined cell dc.nh (PCD) These ,giant muscle fibres are retained during lan.i! and pupal stages until 3 days before adult celosiun at which point thcv hegin to alropliv as a result of a decline in the line of the insect nioullinp hormone (20-hydtoxyecdysonc) Atropln involes the loss ol niuscle mass, without change in niorpliology or physiological luiiction A fnrtlier decline in ecd>steroids (list before emergence commits the ISMs to die during the 36 horns lolloping aduli eclosion When the ISMs become committed to degenerate, polvnbiqinlin gene cxpicssion increases diamaiK.ilK Tins suggests that iibiqnilin-depcndeni piotcohsis il'imclinn of 26S prolcasomes) may play a role in PCD. By screening cDNA clones diffeicnlially expressed during PCD. we liaxe cloned one of the regulator ATPase siibnmts of the Munthtiu 26S pioieasome (MS73). The expression of this gene in ISM greath increases in the pie-eclosion period. Western blots shou that the amount ol'MS73 and other proteasome snbunils increase about 6-fold during the elimination of ISMs. We investigated tiirlher the role of the MS73 proteasome siibnml by ininnmogold electron microscopy using affinity purified antiscra. MS73 imimiuorcacmity was present in ISM undergoing PCD. and lhat the amount of MS73 uithin the cells increased with the progress of cell disruption The heaviest labelling was observed over hclerochromalin in degenerating nuclei, indicating lhat MS73 mav have a special role in Ihc nucleus 1 he coinpaiativc iaiity of labelling over ISM contractile appaialus suggests that disassemhlv and degeneration of mvolllamenls mav not involve MS7v although uc cannot inle out Hie participation ofproleasoincs not containing MS73 snbumts.
|Journal||Biochemical Society transactions|
|Publication status||Published - Jan 1 1996|
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