Glycosylphosphatidylinositol-anchored proteins (GPI-AP) are the primary protein components of yeast cell wall and thus, essential for cellular integrity. The targeting of GPIAPs to the cell surface requires extensive remodeling of the GPI anchor. It has been generally accepted that remodeling of the GPI anchor is exclusively carried out in the Endoplasmic reticulum (ER) in yeast cells, including the addition and subsequent removal of ethanolamine phosphate (EtNP) from mannose 1 (Man1) and mannose 2 (Man2) of the glycan moiety.

My study provides evidence that the removal of EtNP from Man2 is essential for cell viability and is mediated by Ted1p in the ER and Dcr2p in the Golgi. Moreover, I also establish that Cdc1p, which was previously reported to be an ER-resident remodelase, is in fac...[ Read more ]

Glycosylphosphatidylinositol-anchored proteins (GPI-AP) are the primary protein components of yeast cell wall and thus, essential for cellular integrity. The targeting of GPIAPs to the cell surface requires extensive remodeling of the GPI anchor. It has been generally accepted that remodeling of the GPI anchor is exclusively carried out in the Endoplasmic reticulum (ER) in yeast cells, including the addition and subsequent removal of ethanolamine phosphate (EtNP) from mannose 1 (Man1) and mannose 2 (Man2) of the glycan moiety.

My study provides evidence that the removal of EtNP from Man2 is essential for cell viability and is mediated by Ted1p in the ER and Dcr2p in the Golgi. Moreover, I also establish that Cdc1p, which was previously reported to be an ER-resident remodelase, is in fact localized to cis/medial Golgi. In summary, my thesis research establishes that EtNP is removed from Man1 and Man2 of GPI-APs in the Golgi (via Cdc1p and Dcr2p), and while these enzymes rely on COPI-coatomer function for their steady-state localization to the Golgi, they do not ordinarily cycle between the Golgi and the ER.