Fission yeast mutant lacking glucosidase I as a model for human congenital disorders of glycosylation CDG IIb

VALKO, AYELÉN; ETCHEGARAY, EMILIANA; GALLO, GIOVANNA L; PARODI, AJ; ARAMBURU, SOFÍA I.; D'ALESSIO, C

Buenos Aires

Congreso; 3rd Argentinean Symposium on Glycobiology; 2019

Comite Organizador GlycoAR 2019

Glucosidase I(GI) plays a key role in the N-glycanremodeling in the secretory pathway, removing the outermost Glc from protein-linked Glc3Man9GlcNAc2(G3M9). Mutations in GI-encoding gene results in human congenital disordersof glycosylation (CDG) IIb. Deletion of the homologous gene in Schizosaccharomyces pombe produced cellswith a very sick phenotype (Δgls1) that could not be ascribed to theinability of glycoproteins to enter into calnexin-folding cycles, to aninhibition of the oligosaccharyltransferase transfer reaction or to apotentially reduced ERAD. Glycan elongation of glycoproteins in the Golgi and the overall cell wall(CW) monosaccharide composition of Δgls1 mutants were indistinguishable from that in cells lackingGlucosidase II (Δgls2α), whosephenotype is normal. However, transmission electron microscopy showed thatthe CW of Δgls1 was thickerthan the WT and Δgls2α ones, presented a feathered appearance, and lackedthe characteristic three-layered structure. Fluorescence-labeled lectinstaining confirmed that the CW of Δgls1 cells hadan altered structure. The ER localized below the plasma membrane was alsoabsent in Δgls1 cells, indicating that the secretory pathwaystructure may be altered in this mutants, whichconstitute an excellent model organism for the study of CDG-IIb.