The Mystery Behind the Autophagic Process

In the research study “Ultrastructural Analysis of the Autophagic Process in Yeast: Detection of Autophagosomes and Their Characterization,” I enjoyed analyzing figure 1 and I thought it was the most compelling. Even though I have learned in my biology classes that autophagy is an intracellular degradation system that delivers cytoplasmic constituents to the lysosome, it was really interesting to learn how the authors of this experiment detected autophagosomes and analyzed the autophagic process in yeast. For figure 1, the authors wanted to examine the localization of cytosolic enzymes in the vacuoles in situ by immunological electron microscopy. Sections of cells were immunolabeled with anti-ADH antibodies followed by 10-nm colloidal gold-conjugated protein A. Immunoadsorption was used in this experiment, which is the selective removal of a desired compound from a solution or mixture, using an antibody that is bound to a large insoluble molecule. The authors used it to confirm the specificity of the labeling of the fold particles. Figure 1a was carbon-starvation media. The results showed that in control cells grown in YEPD medium, gold particles associated with ADH were found in the cytosol, but were excluded from the vacuoles. On the other hand, for figure 1b, the cells were incubated for 2 hours in nitrogen starvation media. Figure 1b showed how rarely any gold particles were found in the vacuolar sap. In other words, figure 1 indicates that “cytosolic enzymes were not imported directly into vacular sap, but were sequestered non-selectively into vacuoles in the form of autophagic bodies.”

I believe this Nobel Prize was warranted because it was done in yeast, explained the autophagic process which was unclear at the time, and gave hope to cure some critical illnesses caused from cancer and neurological diseases. First, the word autophagy originates from the Greek words “self to eat.” Back in the 1960s, researchers knew that cells could destroy their own contents by enclosing it in membranes and then transporting it to a recycling compartment for degradation, known as the lysosome. However, they had some difficulties in understanding the mechanism and pathways. Second, Ohsumi did not only analyze the autophagic process but also had the method to identify and characterize key genes involved in the process. After his discovery, scientists were able to study autophagy in different physiological conditions, such as in the adaptation to starvation and in response to infection, which was very interesting at the time. The analysis and understanding of the autophagic process were seen as a possible way to treat some forms of cancer since mutations in autophagy genes can cause different diseases and the autophagic process is involved in some neurological diseases, such as Alzheimer’s Disease.

Ohsumi analyzed the autophagic process in yeast cells since they are relatively easy to study and can be used as a model for human cells. Yeast cells are very helpful for identifying genes that are in complex pathways. There are many advantages of using yeast in research. For example, yeast is a eukaryotic organism, which means that they have a nucleus that contains DNA packaged in chromosomes. Genetic manipulation in yeast cells is easy and cheap compared to animals like mice. Also, yeast shares some genes with humans. This can be used to test for different drugs by testing the drug on yeast cells containing mutated human genes. Then, analyzing the results and checking whether the drugs can restore normal function. However, I think working with yeast cells was also challenging for Ohsumi since yeast cells are small and their inner structures are hard to distinguish under the microscope. Ohsumi discussed this issue in one of his interviews. He figured that “if he could disrupt the degradation process in the vacuole while the process of autophagy was active, then autophagosomes should accumulate within the vacuole and become visible under the microscope” (Whittel). Furthermore, Ohsumi’s experiment was very interesting because he proved that autophagy exists in yeast cells too.   



Works Cited


“The Nobel Prize in Physiology or Medicine 2016.”,

Whittel, Naomi. “Rare Interview with Nobel Prize Winner, Dr. Yoshinori Ohsumi on

Autophagy.” YouTube, YouTube, 20 Apr. 2019,