A pivotal gluconeogenic enzyme in Saccharomyces cerevisuae, fructose-1, 6-bisphosphatase (FBPase) was selectively turned over in vacuole via Vid (vacuole import and degradation) dependent pathway in response to the fresh glucose after chronic glucose starvation. TCO89, a novel and unique component of Tor Complex I (TORCI), was found to physically associate with FBPase and significantly affect FBPase degradation via Vid pathway. Further investigation indicated that Deltatco89 mutant strongly impaired FBPase's importing into Vid vesicles and Vid24's association with Vid vesicles. Inactivation of TORCI by rapamycin treatment strongly blocked FBPase degradation. Other components of TORCI were also found to physically associate with FBPase. The P1S mutation of FBPase, reported to block its degradation, was observed to impair the association of FBPase with TORCI components. These results implicated an important regulatory role of TCO89 and TORCI in this pathway.
Keywords: FBPase; Protein degradation; TCO89; Tor Complex 1; Vid.