Abstract
The secretion pathway of Saccharomyces cerevisiae was challenged by constitutively overexpressing plasmid-encoded acid phosphatase, a secreted endogenous glycoprotein. A 2-microns-based multicopy plasmid carrying the coding sequence of acid phosphatase under the control of a truncated variant of the strong constitutive glyceraldehyde-3-phosphate dehydrogenase promoter was used for expression. Selection for the promoterless dLEU2 marker leads to a growth arrest. This is not per se due to leucine starvation, but due to intracellular accumulation of highly glycosylated enzymatically active acid phosphatase. Immunofluorescence and cytological analysis indicate that intracellular accumulation of acid phosphatase occurs in a subpopulation of cells. By Ludox-AM density centrifugation, these cells can be enriched on the basis of their higher density. The dense accumulating cells have a higher average plasmid copy number and produce more acid phosphatase than non-accumulating cells of low density. These cells are defective in directed secretion and bud formation, therefore can no longer grow and show dramatic changes in cell morphology. We suggest that the secretion pathway in these cells is overloaded with the high level of acid phosphatase leading to a shutdown in vectorial secretion, subsequently to a standstill in growth and to the intracellular accumulation of further expressed acid phosphatase. We have indications that accumulation of acid phosphatase occurs in the late Golgi, suggesting a limitation of the overall secretion at this stage.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.