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

GALLO GIOVANNA LUCRECIA; VALKO, AYELEN; ARAMBURU, SOFÍA IVANA; ETCHEGARAY, EMILIANA; PARODI ARMANDO; D'ALESSIO CECILIA

Partido de San Martín, Buenos Aires

Simposio; 3rd Argentinean Glycobiology Symposium "GlycoAr 2019"; 2019

Universidad Nacional de San Martín

Glucosidase I (GI) plays a key role in the N-glycan remodeling inthe secretory pathway, removing the outermost Glc from proteinlinkedGlc3Man9GlcNAc2 (G3M9). Mutations in GI-encoding generesults in human congenital disorders of glycosylation (CDG) IIb.Deletion of the homologous gene in Schizosaccharomycespombe produced cells with a very sick phenotype (Δgls1) thatcould not be ascribed to the inability of glycoproteins to enter intocalnexin-folding cycles, to an inhibition of theoligosaccharyltransferase transfer reaction or to a potentiallyreduced ERAD. Glycan elongation of glycoproteins in the Golgiand the overall cell wall (CW) monosaccharide composition ofΔgls1 mutants were indistinguishable from that in cells lackingGlucosidase II (Δgls2α), whose phenotype is normal. However,transmission electron microscopy showed that the CW of Δgls1was thicker than the WT and Δgls2α ones, presented a featheredappearance, and lacked the characteristic three-layeredstructure. Fluorescence-labeled lectin staining confirmed that theCW of Δgls1 cells had an altered structure. The ER localizedbelow the plasma membrane was also absent in Δgls1 cells,indicating that the secretory pathway structure may be altered inthis mutants, which constitute an excellent model organism forthe study of CDG-IIb.