Specific Developmental Changes in the Regulatory Subunits of the 26 S Proteasome in Intersegmental Muscles Preceding Eclosion inManduca sexta

Abstract

Previously, we have shown extensive reprogramming of the ATPase regulator of the 26S proteasome preceding the programmed destruction of intersegmental muscles (ISM) in the tabacco horn mothManduca sexta(Dawsonet al., J. Biol. Chem.,270,1850–1858, 1995). We now show that the extensive reprogramming of the regulatory components of the 26S proteasome occurs only in ISM and not in flight muscles (FM), which undergo terminal differentiation at ecdysis. Unlike in ISM, the ATPase regulators, MS73, MSS1, TBP1 and mts2, remain at low levels in 26S proteasomes in FM from developmental Stage-0 to Stage-7. The non-ATPase regulator subunit 5a, which binds to multiubiquitin chains, increased in ISM similarly to the ATPases but not in FM. The ecdysteroid agonist RH-5849 prevented these subunit increases in ISM. These findings show that reprogramming of 26 S proteasomes is involved in the specific elimination of ISM during eclosion and does not occur in FM which are needed for adult moth flight.