Activity, abundance and expression of XXXX -activated proteases in skeletal muscle of the aestivating frog, Cyclorana alboguttata.

@entity1 @entity462 @entity3396 @entity24365 @entity2537 @entity194 @entity141 @entity121
UNASSIGNED: In most mammals, prolonged @entity121 (e.g. bed-rest, limb casting or spaceflight) results in @entity194 of muscle fibres which is largely due to unregulated proteolysis. Although numerous proteolytic pathways are known to participate in @entity121 @entity194 , recent evidence suggests that activation of @entity141 -dependent @entity462 proteases (calpains) is required for disuse @entity194 in limb skeletal muscles. In contrast to typical models of @entity121 ( @entity1 and rodents), animals that experience natural bouts of chronic muscle inactivity, such as hibernating mammals and aestivating frogs, consistently exhibit limited or no change in skeletal muscle size. In the current study, we examined enzyme activity, protein abundance and gene expression levels of calpain isoforms in gastrocnemius muscle of the aestivating frog, Cyclorana alboguttata. We predicted that in aestivating C. alboguttata there would be a downregulation of the abundance, activity and gene expression of @entity3396 and @entity24365 . In contrast to our hypothesis, there was no significant decrease in the enzyme activity levels or the relative protein abundances of @entity3396 and @entity24365 . Similarly, gene expression assays (both qRT-PCR and RNA Seq data) indicated that calpains were unaffected by aestivation. Western blotting of 'muscle-specific' calpain 3, which is consistently downregulated during @entity2537 , indicated that this isoform is present in C. alboguttata muscle where it appears to be in its autolysed state. The absence of any increase in enzyme activity, protein and mRNA abundance of calpains in aestivators is consistent with the protection of gastrocnemius muscle against uncontrolled proteolysis throughout aestivation.
