Response of Transmembrane Proteins to Glucose Starvation in Saccharomyces Cerevisiae (2013)

Undergraduate: Laura Ganser

Faculty Advisor: Mara Duncan
Department: Chemistry

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A novel response of Saccharomyces Cerevisiae cells to glucose starvation was characterized. This response involves the endocytosis of transmembrane proteins from the plasma membrane (PM) to the vacuole where they are degraded by proteolysis. Movement begins within 30 min. of starvation and the protein is almost entirely removed between 2 hours and 1 day of starvation. This response was observed in nine of eleven proteins varying in structure, function, and localization on the PM indicating that it is not a selective process. The two outlying proteins are known to exist in stable sub-domains of the PM, indicating that proteins with slower turnover rates are resistant to the internalization. The proteins of interest were tagged with GFP on the cytoplasmic terminus so that observations could be made with fluorescence microscopy at different times throughout starvation. The intensity at the PM was measured for every cell at every time point to quantify the loss of protein from the PM. Several proteins involved in this internalization response have been determined through a mutational analysis. Specific protein mutations that have prevented or delayed the internalization of a representative membrane protein are considered important in the cellular response, however a complete pathway has yet to be determined.