D.Uccelletti, A. Pascoli, P. Mancini1,C.B. Hirschberg2 and C. Palleschi. We report the characterization of
cen-1, a C. elegans gene involved in the unfolded protein response (UPR). Inactivation of UPR signaling has deleterious consequences on cell survival and accumulation of misfolded proteins in the ER may play an important role in human diseases. Therefore, cells have elaborated a phase of the UPR consisting of transcriptional activation of genes whose products play a role in protein processing in the secretory pathway. The mRNAs induced by the UPR encode ER chaperones, disulfide exchange factors and many components of the ER-associated protein degradation (ERAD) machinery. We found that the nucleotidase CEN-1, highly similar to a rat brain UDPase, was transcriptionally up regulated, through
ire-1 activation, in the conditions that induced UPR. In total membrane fractions of
cen-1(RNAi) worms a drastic reduction of UDPase activity was observed. The nucleotidase is probably required for the hydrolysis of UDP generated by the UDP-Glc:glycoprotein glucosyltransferase(GT), a key enzyme of UPR. The UDP is converted into UMP to relieve inhibition of the enzyme and to provide antiport substrates to couple the entrance of nucleotide sugars from the cytosol into the lumen of the secretory pathway with the exit of nucleoside monophosphates. RNAi experiments showed that, when
cen-1 was transiently knocked down, a delay in larval development occurred and a reduction of life span and a defect in pharyngeal morphogenesis could be observed. Although the tissue-specific expression of CEN-1 remain to be analyzed, this protein seems also to be important in the biosynthesis of cuticle and surrounding tissues; this imply a role in the functioning of the secretory apparatus.