What is autophagy? Degradation, recycling, and a beneficial response to stress | Guido Kroemer

[Dr. Kroemer]: So, autophagy is a spectacular
phenomenon in cell biology, one that you can see with your eyes because cells become vacuolated
when this process is induced. So you can see it by light microscopy and
better, of course, by electron microscopy. It is a process that consists in sequestering
portions of the cytoplasm of the cell and then digesting them to recycle the material
and to degrade macromolecules into micromolecules, metabolites, and to allow rebuilding the structures
that have been destroyed. So technically, it works in the sense that
the mouth that is involved in this self-digestion process is the autophagosome. So, it will sequester portions of the cell
in the cytoplasm. It can be an entire organelles including mitochondria,
it can be protein aggregates, it can be bacteria or viruses that invade the cell, and this
autophagosome, once it closes, will fuse with the lysosomes, which is the sort of stomach
of the cell. And in the lysosome, it has been fusing with
the autophagosome, which is then called Autophagolysosome, the luminal content will then be digested. [Rhonda]: So you mentioned the digesting of
these multiple organelles or mitochondria, but also protein aggregates, and viruses,
bacteria, pieces of chromatin, and things all seem to be sort of things that at least
in the sense, if you’re looking at the aggregates, and you know, damage that occurs in a cell,
seems to be something that’s associated with aging in general. So it’s sort of like, kind of seems like it’s
getting rid of all these damaging, potentially damaging, not just aging but also obviously,
an infection. But this process is getting rid of these damaging,
potentially damaging molecules and aggregates and mitochondria which are defective. What is the actual goal of autophagy is? Like you said, is to get rid of these defective
things to then provide energy? [Dr. Kroemer]: Well, it’s actually interesting
to look at the history of autophagy. The name comes from “autos phagy” in Greek
which means “self-eating.” And it’s actually a linguistic invitation
to think about self-mutilation and self-destruction and cell death. And actually, the phenomenon is observed mostly
in the context of stress. So cells, when they are stressed, will often
undergo an autophagic reaction which occurs before the cells die. And so, this chronology of the phenomenon
has been also an invitation to think that autophagy is a mechanism that leads to cell
death until it has been understood that inhibition of autophagy, which can only be achieved in
a specific way by genetic tricks, will actually sensitize cells to cell death induction. And so, this means that autophagy is a means
of adaptation to stress and a technique of the cell to avoid cell death. So, the primary goal of autophagy is adaptation
to changing conditions and adaptation to external stress, and at the end, avoidance of the unwarranted
demise of the cell.

3 thoughts on “What is autophagy? Degradation, recycling, and a beneficial response to stress | Guido Kroemer

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