Mutation of Nogo-B Receptor, a Subunit of cis-Prenyltransferase, Causes a Congenital Disorder of Glycosylation

• Loss of NgBR in mice causes early embryonic lethality and defects in glycosylation
• Eukaryotic cis-PTase is a heteromer composed of NgBR and hCIT
• Mutations of NgBR cause defects in cholesterol trafficking and dolichol biosynthesis
• NgBR mutation in humans causes a new congenital disorder of glycosylation

SummaryDolichol is an obligate carrier of glycans for N-linked protein glycosylation, O-mannosylation, and GPI anchor biosynthesis. cis-prenyltransferase (cis-PTase) is the first enzyme committed to the synthesis of dolichol. However, the proteins responsible for mammalian cis-PTase activity have not been delineated. Here we show that Nogo-B receptor (NgBR) is a subunit required for dolichol synthesis in yeast, mice, and man. Moreover, we describe a family with a congenital disorder of glycosylation caused by a loss of function mutation in the conserved C terminus of NgBR-R290H and show that fibroblasts isolated from patients exhibit reduced dolichol profiles and enhanced accumulation of free cholesterol identically to fibroblasts from mice lacking NgBR. Mutation of NgBR-R290H in man and orthologs in yeast proves the importance of this evolutionarily conserved residue for mammalian cis-PTase activity and function. Thus, these data provide a genetic basis for the essential role of NgBR in dolichol synthesis and protein glycosylation.

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