Abstract
The yeast Saccharomyces cerevisiae is one of the best characterized eukaryotic models. The secretory pathway was the first trafficking pathway clearly understood mainly thanks to the work done in the laboratory of Randy Schekman in the 1980s. They have isolated yeast sec mutants unable to secrete an extracellular enzyme and these SEC genes were identified as encoding key effectors of the secretory machinery. For this work, the 2013 Nobel Prize in Physiology and Medicine has been awarded to Randy Schekman; the prize is shared with James Rothman and Thomas Südhof. Here, we present the different trafficking pathways of yeast S. cerevisiae. At the Golgi apparatus newly synthesized proteins are sorted between those transported to the plasma membrane (PM), or the external medium, via the exocytosis or secretory pathway (SEC), and those targeted to the vacuole either through endosomes (vacuolar protein sorting or VPS pathway) or directly (alkaline phosphatase or ALP pathway). Plasma membrane proteins can be internalized by endocytosis (END) and transported to endosomes where they are sorted between those targeted for vacuolar degradation and those redirected to the Golgi (recycling or RCY pathway). Studies in yeast S. cerevisiae allowed the identification of most of the known effectors, protein complexes, and trafficking pathways in eukaryotic cells, and most of them are conserved among eukaryotes.
Highlights
Introduction on Membrane TraffickingIn eukaryotic cells, membrane and soluble organellar proteins are generally translocated to the endoplasmic reticulum (ER) during synthesis and have to be transported to their correct target compartment in order to fulfill their function, undergo modifications, or be degraded
After being translocated to the ER, all newly synthesized proteins are directed to the Golgi apparatus where they are sorted between those transported to the plasma membrane (PM) or the external medium and those targeted to the vacuole either through endosomes or directly
Transported to endosomes where they are sorted between those targeted for vacuolar degradation and those redirected to the Golgi where they enter the secretory pathway to be readdressed to the PM
Summary
Members of the Fungi kingdom, proliferating by budding or fission. In 1875, Jacob Christian Jacobsen (1811–1887), founder of the Carlsberg brewing company, decided to set up a laboratory, “The Carlsberg Laboratory”, to understand the physiology of yeast cells in order to better control the fermentation process He hired Emil Christian Hansen (1842–1909), a renowned specialist in fungi and physiology. Hansen discovered that the fungi used by the industry were a mixture of different yeast species He isolated and selected the clones that were the most interesting for fermentation, introducing the use of pure culture strains in industry [1]. Unterhefe No 1, the bottom-fermenting brewer’s yeast used to produce the “Lager” since 1883; this strain is termed Saccharomyces carlsbergensis [2] Thanks to these pioneering studies and the development of experimental processes to isolate, maintain and culture pure yeast strains, S. cerevisiae has been playing an important role in research and has become a widely used eukaryotic model organism
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