S. Duvet et al., Reciprocal relationship between alpha 1,2 mannosidase processing and reglucosylation in the rough endoplasmic reticulum of Man-P-Dol deficient cells, EUR J BIOCH, 267(4), 2000, pp. 1146-1152
The study of the glycosylation pathway of a mannosylphosphoryldolichol-defi
cient CHO mutant cell line (B3F7) reveals that truncated Glc((0-3))Man(5)Gl
cNAc(2) oligosaccharides are transferred onto nascent proteins. Pulse-chase
experiments indicate that these newly synthesized glycoproteins are retain
ed in intracellular compartments and converted to Man(4)GlcNAc(2) species.
In this paper, we demonstrate that the alpha 1,2 mannosidase, which is invo
lved in the processing of Man(5)GlcNAc(2) into Man(4)GlcNAc(2), is located
in the rough endoplasmic reticulum. The enzyme was shown to be inhibited by
kifunensine and deoxymannojirimycin, indicating that it is a class I manno
sidase. In addition, Man(4)GlcNAc(2) species were produced at the expense o
f Glc(1)Man(5)GlcNAc(2) species. Thus, the trimming of Man(4)GlcNAc(2) to M
an(4)GlcNAc(2), which is catalyzed by this mannosidase, could be involved i
n the control of the glucose-dependent folding pathway.