The Caenorhabditis elegans UDP-Glc:glycoprotein glucosyltransferase homologue CeUGGT-2 is an essential protein that does not function as a glycoprotein conformation sensor

BUZZI, L; SIMONETTA , S; ARMANDO J. PARODI .; CASTRO, O

Los Angeles

Congreso; 19 thI nternational C.elegans Meeting; 2013

Genetic Society of America

The UDP-Glc:glycoprotein glucosyltransferase (UGGT) is the key component of the glycoprotein folding quality control mechanism that takes place in the endoplasmic reticulum (ER). It behaves as a sensor of glycoprotein conformation as it exclusively glucosylates glycoproteins not displaying their native conformations. The addition of this glucose residue enables the interaction of folding intermediates with Calnexin/Calreticulin. An enzymatically active UGGT is encoded by a single gene in Schizosaccharomyces pombe, Drosophila melanogaster, Trypanosoma cruzi and plants. There are two homologues coding for UGGT-like proteins in in the genus Caenorhabditis. Both UGGT homologues are expressed in human cells, the former but not the latter displays UGGT activity and is upregulated under ER stress conditions. Bioinformatics analysis showed that in Chaenorhabditis elegans there are two genes, uggt-1 and uggt-2 coding for UGGT homologues. We had previously reported that C. elegans expressed an active UGGT protein localized to the ER encoded by the uggt-1.gene and its expression is upregulated under ER stress. Here we report that CeUGGT-2 expression is essential for normal development and this enzyme lacks UGGT activity. We analyzed heterozygous uggt-2(ok2510) worms, chromosome balanced with hT2 (I; III), and found that more than 50% of the eggs laid by this strain did not develop to progressive larval stages. A small amount of embryos progressed to L1 stage, looked very sick and had many vacuoles in their intestinal cells. We expressed CeUGGT-2 and two chimeric proteins, one composed by the N-terminal domain of S.pombe UGGT and the CeUGGT-2 C-terminal domain; and the other one composed by the CeUGGT-2 N-terminal domain and the S.pombe C-terminal domain in S.pombe. Both UGGT-2 and the two chimeric protein proved to be fully inactive.