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AUTOPHAGY
Parvinderdeep Singh Kahlon
PCDU Seminar
WS 2015/2016
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https://goo.gl/gz5oJA
CONTENT
 Introduction
 Role
of Autophagy
 Types of Autophagic Processes
 Summary
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INTRODUCTION
[1]
Autophagy, the process of cellular self-eating, is
an important protein degradation pathway,
particularly during starvation or stress.
 It is as a bulk process which degrade long-lived
proteins and organelles such as the endoplasmic
reticulum, mitochondria, peroxisomes, the
nucleus and ribosomes [2,3]

In contrast to the ubiquitin–proteasome system (UPS),
which targets individual short-lived proteins
[1] http://pilotfire.com/wp-content/uploads/autophagy.png
[2] Mizushima, N. & Klionsky, D. J. 2007. Protein turnover via autophagy: implications for metabolism. Annu. Rev. Nutr. 27, 19–40.
[3] Stolz, A., Ernst, A. & Dikic, I. 2014. Cargo recognition and trafficking in selective autophagy. Nat. Cell Biol. 16, 495–501 .
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ROLE OF AUTOPHAGY



Autophagic degradation promotes the recycling
and salvage of cellular nutrients, thereby
enabling cell survival during starvation.
Along with the UPS, helps in protein homeostasis
and quality control.
It also plays a key part in mobilizing diverse
cellular energy and nutrient stores, including
carbohydrates, lipids and minerals.
Kaur J and Debnath J. 2015. Autophagy at the crossroads of catabolism and anabolism. Nature Reviews : 16;461 472
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TYPES
Autophagy refers to a collection of tightly
regulated catabolic processes, all of which deliver
cytoplasmic components to the lysosome for
degradation
 In animals and yeasts, autophagy is often divided
into three main types:
Chaperone-mediated autophagy,
Microautophagy,
Macroautophagy.

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http://www.nature.com/nrgastro/journal/v11/n3/images/nrgastro
.2013.211-f1.jpg
DETAILED PROCESS
Kaur J and Debnath J. 2015. Autophagy at the crossroads of catabolism and anabolism. Nature Reviews : 16;461 472
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CHAPERONE-MEDIATED
AUTOPHAGY



Target protein binds to a chaperone
protein.
The target protein then is transported
to a lysosome, becomes unfolded and is
taken up by direct translocation
across the lysosomal membrane.
It occurs only in mammalian cells but it cannot
be excluded that a similar mechanism occurs in
plants.
Doorn WG and Papini A. 2013. Ultrastructure of autophagy in plant cells .Autophagy 9:12, 1–15
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MICROAUTOPHAGY



It is the process of uptake of cellular constituents
by the lysosomal/vacuolar membrane.
The membrane surrounds a portion of the
cytoplasm, merges with itself, and then
undergoes scission.
This results in a portion of the cytoplasm,
surrounded by a piece of lysosomal/vacuolar
membrane, inside the lysosome/ vacuole.
May AI, Devenish RJ, Prescott M. 2012 The many faces of mitochondrial autophagy: Making sense of contrasting observations
in recent research. Int J Cell Biol,1-18.
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DIAGRAMMATIC OVERVIEW
(A) Invagination (A1) or
protrusion (A2) of
the vacuolar membrane,
resulting in the uptake
of a portion of the
cytoplasm.
(B)
Invagination
membrane-bound
vesicle in the cytoplasm
is taken up by the
vacuole
Doorn WG and Papini A. 2013. Ultrastructure of autophagy in plant cells .Autophagy 9:12, 1–15
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EXAMPLE OF MICROAUTOPHAGY
(A and B) Invaginations into the vacuole. (C)
Rubber particles in cytoplasm and vacuole
D) Senescing petals of carnation flowers
Doorn WG and Papini A. 2013. Ultrastructure of autophagy in plant cells .Autophagy 9:12, 1–15
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MACROAUTOPHAGY



Macroautophagy is performed in the cytoplasm,
whereby a portion of the cytoplasm is
sequestered inside a doublemembrane-bound
organelle.
Hydrolases take place, away from the vacuole.
The cytoplasmic material is broken down inside
this structure by small tubules formation or
membranes formation at the ER
Bassham DC, Laporte M, Marty F, Moriyasu Y, Ohsumi Y, Olsen LJ, Yoshimoto K. 2006. Autophagy in development and
stress responses of plants. Autophagy 2:2-11.
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DIAGRAMMATIC OVERVIEW
(A) small tubules are formed in
the cytoplasm (B) membranes
with an ER-like structure are
formed at theER
Doorn WG and Papini A. 2013. Ultrastructure of autophagy in plant cells .Autophagy 9:12, 1–15
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EXAMPLE OF MACROAUTOPHAGY
(A) Formation of a cagelike structure (B–D)
Various
stages
of
autophagosome/
autolysosome formation
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Doorn WG and Papini A. 2013. Ultrastructure of autophagy in plant cells .Autophagy 9:12, 1–15
PROGRAMMED CELL DEATH (PCD)
during normal development and after abiotic
stress (developmental PCD)
2.
after invasion by a pathogen (pathogen-related
PCD).
 Massive autophagy (called mega-autophagy) is
typical for the final phase of developmental PCD.
1.
•
•
•
•
rupture of the vacuolar membrane
release of large amounts of hydrolases into the cytoplasm.
degrade the cytoplasm
This results in cell death
Doorn WG and Papini A. 2013. Ultrastructure of autophagy in plant cells .Autophagy 9:12, 1–15
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PCD AT TIME OF BACTERIAL INFECTION


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In plants, (AtMC1)
positively
regulates
HR
cell
death
mediated by NB-LRR
recognition
of
the
invading pathogen at
the site of infection.
LSD1
negatively
regulates cell death
propagation in cells
surrounding
the
infection
site
presumably by binding
to AtMC1 and holding
it inactive in the
cytoplasm..
Coll NS et al., 2011. Programmed cell death in
the plant immune system. Cell Death and
Differentiation18, 1247–1256.
INTERNAL DEGENERATION OF
CHLOROPLASTS
 Membrane
bound
vesicles
with
degradation products are formed inside
the organelle.
 These
vesicles move into the cytoplasm
and are subsequently taken up by the
vacuole where they become degraded.
Doorn WG and Papini A. 2013. Ultrastructure of autophagy in plant cells .Autophagy 9:12, 1–15
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SCHEMATIC OVERVIEW
Proposed model of
the degradation
of Rubisco and
possibly
other
stromal proteins
by
ATGdependent
autophagy
via
RCBs
Ishida H et al., 2008. Mobilization of Rubisco and Stroma-Localized Fluorescent Proteins
of Chloroplasts to the Vacuole by an ATG Gene-Dependent Autophagic Process.. Plant
Physiology, 148: 142-155
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SUMMARY
Autophagy, the process of cellular selfeating
recycling and salvage of cellular nutrients,
protein homeostasis, mobilizing diverse
cellular energy and nutrient stores
In yeast and mammals majorly divided
into three main types, plants have
addition types
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•Presently little is known
about the ultrastructure
of autophagy in plants
•Extensive research is yet
needed to know the
unknown
Thank You
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