RRC ID 12703
Author Stigliano ID, Alculumbre SG, Labriola CA, Parodi AJ, D'Alessio C.
Title Glucosidase II and N-glycan mannose content regulate the half-lives of monoglucosylated species in vivo.
Journal Mol Biol Cell
Abstract Glucosidase II (GII) sequentially removes the two innermost glucose residues from the glycan (Glc(3)Man(9)GlcNAc(2)) transferred to proteins. GII also participates in cycles involving the lectin/chaperones calnexin (CNX) and calreticulin (CRT) as it removes the single glucose unit added to folding intermediates and misfolded glycoproteins by the UDP-Glc:glycoprotein glucosyltransferase (UGGT). GII is a heterodimer in which the α subunit (GIIα) bears the active site, and the β subunit (GIIβ) modulates GIIα activity through its C-terminal mannose 6-phosphate receptor homologous (MRH) domain. Here we report that, as already described in cell-free assays, in live Schizosaccharomyces pombe cells a decrease in the number of mannoses in the glycan results in decreased GII activity. Contrary to previously reported cell-free experiments, however, no such effect was observed in vivo for UGGT. We propose that endoplasmic reticulum α-mannosidase-mediated N-glycan demannosylation of misfolded/slow-folding glycoproteins may favor their interaction with the lectin/chaperone CNX present in S. pombe by prolonging the half-lives of the monoglucosylated glycans (S. pombe lacks CRT). Moreover, we show that even N-glycans bearing five mannoses may interact in vivo with the GIIβ MRH domain and that the N-terminal GIIβ G2B domain is involved in the GIIα-GIIβ interaction. Finally, we report that protists that transfer glycans with low mannose content to proteins have nevertheless conserved the possibility of displaying relatively long-lived monoglucosylated glycans by expressing GIIβ MRH domains with a higher specificity for glycans with high mannose content.
Volume 22(11)
Pages 1810-23
Published 2011-6-1
DOI 10.1091/mbc.E11-01-0019
PII mbc.E11-01-0019
PMID 21471007
PMC PMC3103398
MeSH Carbohydrate Sequence Endoplasmic Reticulum / metabolism Gene Knockout Techniques Glucosyltransferases / genetics Glucosyltransferases / metabolism Glycoproteins / metabolism* Half-Life Hexosyltransferases / metabolism Mannose / metabolism* Molecular Sequence Data Polysaccharides / chemistry Polysaccharides / metabolism Protein Folding Protein Interaction Domains and Motifs Protein Stability Protein Structure, Tertiary Schizosaccharomyces / enzymology* Schizosaccharomyces / genetics alpha-Glucosidases / genetics alpha-Glucosidases / metabolism* alpha-Mannosidase
IF 3.791
Times Cited 30
DNA material pREP1-ccdB2 (RDB06519) S. pombe entry SpEnt26D11 (SPW010483).