Figure 4.

Lipid linked oligosaccharide analysis in 4 PGM1 deficient cell lines showing reduced LLO at Baseline and Improvement Following D-gal Supplementation

To investigate whether PGM1 deficiency disrupts the formation of LLO, which is a required precursor for the synthesis of nascent N-linked glycoproteins in the ER, we performed lipid linked oligosaccharide (LLO) and protein linked oligosaccharide (PLO) analyses in the skin fibroblasts of patients 1, 2, 8, and cell-line 2013Y. The cells were deprived of glucose while the culture media was supplemented without or with 10mM D-gal (for one hour. The level of full-length LLO (Glc₃Man₉GlcNAc₂-PP-Dol, G3) or sugar moieties bound to newly synthesized PLO (mainly Glc₁Man₉ and Man₉), remained fairly unchanged in control cells (Figure 4, left column), indicating a high degree of metabolic fitness in these cells. In contrast, cells from all four patients showed a large amount of shortened LLO (Man₉GlcNAc₂-PP-dolichol) (Figure 4, LLO top row). In contrast, the PLO profile was indistinguishable from the control cells (Figure 4, PLO top row). Interestingly, galactose supplementation led to the reduction of shortened LLO (Man₉GlcNAc₂-PP-dolichol) in patients 1 2, and cell-line 2013Y, resulting in a LLO profile that is similar to control. No improvement was observed in patient 8 (Figure 4, LLO bottom row). D-Gal supplementation had no effect on the PLO profile in all patients (Figure 4, PLO bottom row).