Cdc1 removes the ethanolamine phosphate of the first mannose of GPI anchors and thereby facilitates the integration of GPI proteins into the yeast cell wall.
Bottom Line: Cdc1-314(ts) mutants do not accumulate GPI proteins in the ER but have a partial secretion block later in the secretory pathway.Osmotic support restores GPI protein secretion and actin polarization but not growth.This suggests that the presumed transglycosidases Dfg5 and Dcw1 of cdc1-314(ts) transfer GPI proteins to cell wall β1,6-glucans inefficiently.
Affiliation: Department of Biology, University of Fribourg, CH-1700 Fribourg, Switzerland.Show MeSH
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Mentions: The reason why emp24∆, per1∆, and gup1∆ restore the growth of cdc1 at 30°C may be that all these mutants reportedly accumulate GPI proteins in the ER (Fujita and Jigami, 2008; Castillon et al., 2011; Figure S3B). This would prolong the time span during which newly synthesized GPI proteins can be acted on by the residual phosphodiesterase activity of Cdc1-314 in the ER, thereby increasing the percentage of correctly processed anchors. It may also be, however, that the strong UPR induced by deletions such as emp24∆, per1∆, and gup1∆ (Jonikas et al., 2009) would help cdc1 cells to overcome its late secretion block (see Figure 7A later in this article). Indeed, the similar sec1ts block is partially cured by a strong UPR (Chang et al., 2004). On the other hand, subsistence of the acyl on the inositol moiety in bst1∆ may impede the interaction of the GPI anchor with Cdc1, leading to the strongly negative interaction of bst1∆ and cdc1 (Table S1).
Affiliation: Department of Biology, University of Fribourg, CH-1700 Fribourg, Switzerland.