Protein Sorting Upon Exit from the Endoplasmic Reticulum Dominates Golgi Biogenesis in Budding Yeast.

Cells sense and control the number and quality of their organelles, but the underlying mechanisms of this regulation are not understood. Our recent research in the yeast Saccharomyces cerevisiae has shown that long acyl chain ceramides in the endoplasmic reticulum (ER) membrane and the lipid moiety of glycosylphosphatidylinositol (GPI) anchor determine the sorting of GPI-anchored proteins in the ER. Here, we show that a mutant strain, which produces shorter ceramides than the wild-type strain, displays a different count of Golgi cisternae. Moreover, deletions of proteins that remodel the lipid portion of GPI anchors resulted in an abnormal number of Golgi cisternae. Thus, our study reveals that protein sorting in the ER plays a critical role in maintaining Golgi biogenesis. The endoplasmic reticulum (ER) serves not only as a site of coat protein complex II vesicle formation but also as a site of protein sorting in budding yeast. Our data show that mutant strains defective in protein sorting in the ER affect the numbers of Golgi cisternae. This finding suggests that protein sorting plays a critical role in maintaining Golgi biogenesis. image