부산대학교 도서관

Endoplasmic reticulum-associated degradation of misfolded or misprocessed glycoproteins in mammalian cells is prevented by inhibitors of class I α-mannosidases implicating mannose trimming from the precursor oligosaccharide Glc[sub 3]Man[sub 9]GlcNAc[sub 2] as an essential step in this pathway. However, the extent of mannose removal has not been determined. We show here that glycoproteins subject to endoplasmic reticulum-associated degradation undergo reglucosylation, deglucosylation, and mannose trimming to yield Man[sub 6]GlcNAc[sub 2] and Man[sub 5]GlcNAc[sub 2]. These structures lack the mannose residue that is the acceptor of glucose transferred by UDPGlc:glycoprotein glucosyltransferase. This could serve as a mechanism for removal of the glycoproteins from folding attempts catalyzed by cycles of reglucosylation and calnexin/calreticulin binding and result in targeting of these molecules for proteasomal degradation. [ABSTRACT FROM AUTHOR]