Neither the N-terminal domain that harbors the misfolding sensing activity nor C-terminal catalytic domain of C.elegans UGGT2 is functionally competent

SANTILLAN V; BUZZI LI; SEGOBIA VA; ARMANDO J. PARODI .; CASTRO OA

Buenos Aires

Simposio; FRONTERAS EN BIOCENCIAS 3; 2018

Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA, CONICET ? Partner Institute of the Max Planck Society)

Neither the N-terminal domain that harbors the misfolding sensing activity nor C-terminal catalytic domain of C.elegans UGGT2 is functionally competentBuzzi, LI a, Segobia VA b, Santillán VJ c, Parodi, A d. and Castro OA b,c+. a Fundación Instituto Leloir, Buenos Aires, Argentina b Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Buenos Aires, Argentina c Universidad de Buenos Aires-CONICET, (IQUIBICEN), Buenos Aires, Argentina.d Fundación Instituto Leloir, IIBBA-CONICET, Buenos Aires, Argentina.+ e-mail (alecastro2901@gmail.com) Quality control mechanism ensure that newly synthesized glycoproteins reach their properly folded conformation. The UDP-Glc glycoprotein glucosyltransferase (UGGT) which functions as a conformational sensor that selectively recognizes and reglucosylates only misfolded glycoproteins is the key element of this mechanism. UGGT is composed of at least two domains: the N-terminal domain that has no homology to other known proteins and is involved in the recognition of the improperly folded proteins and the C-terminal domain displaying significant similarity to members of glycosyltransferase family 8. There are two homologous genes (uggt1 and uggt2) coding for UGGT-like proteins in most vertebrates and at least in some species of nematodes belonging to the genus Caenorhabditis. On the contrary, Drosophila melanogaster and Schizosaccharomyces pombe genomes carry only one uggt gene. Whereas the role of UGGT1 in glycoprotein folding has been undoubtedly stated, biological function of UGGT2 is still elusive. We have previously determined that CeUGGT1 is active but CeUGGT2 does not display canonical UGGT activity. Whereas Ceuggt-2 is an essential protein, depletion of UGGT1 only produces subtle phenotypes suggesting that both UGGTs plays different biological functions. Chimeric proteins containing S. pombe UGGT N-terminal and CeUGGT2 C-terminal domains or the inverse construction were expressed in S.pombe UGGT null mutant cells. In this report, we demonstrate that CeUGGT2 C-terminal domain lacks UGGT canonical activity and that CeUGGT-2 N-terminal domain does not activate the S. pombe catalytic domain. In addition, transgenic worms were generated to study the body pattern expression of CeUGGT-1 and CeUGGT-2 using fluorescent reporters. UGGT-1 were widely expressed but the extremely low level of expression of UGGT-2 did not allow us to determine its pattern. These results reinforce the idea that each UGGTs perform a different biological function. Unpublished analysis from our laboratory indicates that CeUGGT2 probably had gone through a neofunctionalization process.