Autophagy – the 2016 Nobel Prize in Physiology or Medicine
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Autophagy – the 2016 Nobel Prize in Physiology or Medicine


Autophagy is the process by which eukaryotic
cells degrade and recycle their cellular components. The word autophagy stems from Greek words,
auto=self and phagein=to eat. Thus, the word autophagy represents self-eating. This phenomenon of cells eating their own
contents was first observed in the 1960s. But little was known about the process until
Yoshinori Ohsumi came up with a method to study autophagy using baker’s yeast. Yeast cells are easy to manipulate and study
and so are often used as model for mammalian cells. But yeast cells are also very small and so
it is difficult to see what is going on in the cells. It was known that during autophagy, contents
of the cell are enclosed in membranes and carried to the lysosome in case of mammalian
cells or vacuoles in case of yeast and plant cells. Here, in these specialized compartments, the
contents of the cell are degraded. Ohsumi reasoned that if he disrupted the degradation
process, the cargo will accumulate in the vacuole of the yeast and could be easily studied. So he prepared mutant cells of baker’s yeast
lacking vacuolar proteases. Proteases are enzymes that degrade proteins. His experiment was successful. These mutant yeast cells accumulated small
spherical bodies in their vacuoles when exposed to nutrient-deficient stress conditions. The mutants could not degrade these bodies. In 3 hours, the bodies completely filled the
vacuole. These bodies were named autophagic bodies. They were 400-900 nm in diameter. The contents of the autophagic bodies were
morphologically identical to that of the cytosol. These bodies enclosed ribosomes, rough endoplasmic
reticulum, mitochondria, lipid granuoles, glycogen granuoles and packets of cytosol. Ohsumi next prepared autophagy-defective mutants
by chemical mutagenesis of the protease-deficient mutants. Autophagy-defective mutants did not accumulate
autophagic bodies under stress conditions. These mutants lacked the ability to perform
autophagy and lost their viability fast under nutrient deficient stress conditions. These showed that autophagy was important
for survival under stress. Genetic analysis of these autophagy-defective
mutants led to identification of 14 genes essential for autophagy. Further study of these mutants helped in deciphering
the protein-conjugate system involved in the process of autophagy. These discovered proteins have mammalian homologues,
suggesting that the process of autophagy is conserved from yeast to mammals. Thus, the process of autophagy functional
in our own cells is very similar to the one in yeast. Ohsumi’s pioneering work in baker’s yeast
provided tools for studying autophagy in human cells. We now know that autophagy is important for
adaptation to starvation or response to infections. Autophagy also contributes to embryonic development
and cell differentiation. Thus, impaired autophagy can result in genetic
disorders. Autophagy also removes damaged proteins and
organelles in elderly and thus helps minimize the negative effects of ageing. Disruption of autophagy is linked to various
diseases of elderly like cancer, cardiovascular diseases, neurodegenerative diseases, Parkinson’s
disease and type 2 diabetes. For his contributions in understanding the
mechanism of autophagy, Yoshinori Ohsumi was awarded the 2016 Nobel Prize in physiology/medicine. Hi, don’t forget to like and share the video. Also subscribe to get more videos about the
fascinating Omnipotent Microbes.

3 thoughts on “Autophagy – the 2016 Nobel Prize in Physiology or Medicine

  1. Dr. Sebi has been imputing this in us for years way before this scientist. However I love the fact that people are starting to open up theirs eyes to the bullshit the pharmaceutical industry sells us.

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