Glucose starvation induces microautophagy in yeast cells (2014)

Undergraduates: Lauren Askew, Dr. Mara Duncan, Dr. Claire Gordy

Faculty Advisor: Henrik Dohlman
Department: Biology

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Autophagy is a survival mechanism utilized by all eukaryotic cells during nutrient starvation in which the cell recycles cytoplasmic components to the vacuole to degrade and release. Understanding this mechanism can potentially improve cell survival after stroke and heart attack, thus minimizing tissue damage. Macroautophagy,the better known pathway,involves recycling cellular components via a double-membrane bound vesicle, whereas microautophagy is poorly understood and involves the vacuole directly engulfing the cytoplasmic components. Previous internal studies showed glucose starvation inhibited macroautophagy in S. cerevisiae cells; yet, some autophagic activity was detected by an enzymatic assay. To determine whether this activity was due to microautophagy, we deleted a critical gene for macroautophagy, Atg5, and genes that potentially influence microautophagy, Vtc1 and Vtc2, in a Pho8Δ60 strain, allowing us to measure autophagy quantitatively through the Pho8Δ60 enzymatic assay. We starved these strains for nitrogen, glucose, or both nitrogen and glucose for 30 hours and found that Vtc2, not Vtc1 or Atg5, was required for autophagic activity in glucose-starved cells. We concluded that microautophagy occurs in glucose-starved cells, and some of the genes in the vacuolar transporter chaperone (VTC) complex are more important in glucose-starved cells than others. Currently, we are testing selective microautophagy of organelles during glucose starvation.