Figure 1.

GPI-based protein production system. (A) PGAP2 is required for the addition of the saturated acyl chain to the lyso-GPI moiety, which ensures correct expression of GPI-APs on the cell surface. In PGAP2 mutant cells, lyso-GPI-APs are transported to the cell surface and then most of the GPI-APs are secreted into the medium. Since lyso-forms of GPI-APs are very sensitive to PLD, the GPI structure of secreted proteins become PLD-cleaved forms. (B) The GPI-anchoring system ensures the expression of target proteins as GPI-APs on the cell surface. Cells expressing target proteins at a high level can be enriched by selection of the GPI-anchored target proteins. Removal of the PGAP2 gene results in higher amounts of the target proteins being secreted into the medium.