TEMPERATURE-DEPENDENT ENHANCEMENT OF PROTEOLYSIS IN C2C12 MYOTUBES INASSOCIATION WITH THE ACTIVATION OF 26S PROTEASOME

The effect of temperature on protein metabolism of C2C12 myotubes was investigated in order to estimate the potential effect of fever on mus cle catabolism. The half-life of long-lived proteins in C2C12 myotubes was significantly (13%) shorter when incubated at 40 degrees C than a t 37 degrees C. The activities of cathepsins B and L were not signific antly different at 37 and 40 degrees C, nor were the levels of the pro tein and mRNA of the two cathepsins. In contrast, the chymotrypsin-lik e activity of 26S proteasome was elevated by 53% at 40 degrees C, comp ared to that at 37 degrees C, although it was not associated with an i ncrease in the levels of the protein and mRNA of proteasome subunits. mRNA levels of calpain and ubiquitin were not affected by temperature. It is concluded that temperature-dependent enhancement of proteolysis in C2C12 myotubes is associated with an increase in 26S proteasome ac tivity. (C) 1996 Academic Press, Inc.