Biochemical and functional Characterization of the two putative ER UDP-Glc:glycoprotein glucosyltransferase of C. elegans

BUZZI, LUCILA INÉS; PARODI, ARMANDO; CASTRO, OLGA A.

Nueva York, Cold Spring Harbor

Exposición; "C. elegans course": work presentation; 2010

Cold Spring Harbor Laboratory, C. elegans course

The N-glycan-dependent quality control of glycoprotein folding prevents endoplasmic to Golgi exit of folding intermediates, irreparably misfolded glycoproteins and incompletely assembled multimeric complexes. It also enhances folding efficiency by preventing aggregation and facilitating formation of proper disulfide bonds. The control mechanism essentially involves four components, resident lectin-chaperones that recognize monoglucosylated polymannose glycans, a lectin-associated oxidoreductase acting on monoglucosylated glycoproteins, a glucosyltransferase that creates monoglucosytlated epitopes in protein-linked glycans and a glucosidase that removes the glucose units added by the glucosyltransferase. This last enzyme is the only mechanism component sensing glycoprotein conformations as it creates monoglucosylated glycans exclusively in not properly folded species or in not completely assembled complexes. The UDP-Glc: glycoprotein glucosyltransferase (GT) in the ER of eukaryotic cells behaves as a sensor of glycoprotein conformations and is a key element in the quality control of glycoprotein folding in that subcellular location. Most organisms (Schizosaccharomyces pombe, Drosophila melanogaster, Mus musculum, Arabidopsis thaliana, etc) only express one GT protein whereas Homo sapiens and C. elegans express two of them. One of the human GT proteins apparently lacks enzymatic activity and is not induced under ER stress conditions as happens with the active variety. Moreover Saccharomyces cerevisiae only express one GT-like protein and it lacks enzymatic activity. We showed that one of the genes of C. elegans is a GT while the other might not have a GT activity. Both of them can be expressed in S. cerevisiae, and we´re trying to tag them in S. pombe to show their correct expression. We found also that worms treated with RNAi against both proteins has survival defects and has a delay in development. Also worms presented protruding vulva and protruding intestine while treated with RNAi against any one of these genes.