Glycophosphatidylinositol-anchored proteins (GPI-APs) play essential roles in physiology, but their biogenesis and trafficking have not been systematically characterized. Here, we took advantage of the recently available haploid genetics approach to dissect GPI-AP pathways in human cells using prion protein (PrP) and CD59 as model molecules. Our screens recovered a large number of common and unexpectedly specialized factors in the GPI-AP pathways. PIGN, PGAP2, and PIGF, which encode GPI anchor-modifying enzymes, were selectively isolated in the CD59 screen, suggesting that GPI anchor composition significantly influences the biogenesis of GPI-APs in a substrate-dependent manner. SEC62 and SEC63, which encode components of the ER-targeting machinery, were selectively recovered in the PrP screen, indicating that they do not constitute a universal route for the biogenesis of mammalian GPI-APs. Together, these comparative haploid genetic screens demonstrate that, despite their similarity in overall architecture and subcellular localization, GPI-APs follow markedly distinct biosynthetic and trafficking pathways. Using comparative haploid genetic screens in human cells, Davis et al. find that GPI-anchored proteins follow markedly distinct biosynthetic and trafficking pathways in spite of their similarity in overall architecture and subcellular localization.
Davis, E. M., Kim, J., Menasche, B. L., Sheppard, J., Liu, X., Tan, A. C., & Shen, J. (2015). Comparative Haploid Genetic Screens Reveal Divergent Pathways in the Biogenesis and Trafficking of Glycophosphatidylinositol-Anchored Proteins. Cell Reports, 11(11), 1727–1736. https://doi.org/10.1016/j.celrep.2015.05.026