1. Chapter 18
Apoptosis
Copyright © Garland Science 2008

2. Two distinct forms of cell death
Apoptosis
M18.1
건강한 성인: Billions of cells die every hour
Programmed cell death(PCD): idea in 1970s acceptance (20년)
:apoptosis (PCD의 한종류)
Two distinct forms of cell death
apoptosis
necrosis
Swell
Burst
Spilling their contents
Eliciting inflammatory response
Cell shrinks, Cytoskeletin collapses, 핵막 분해, DNA 절단
Apoptic body-chemically altered:macrophage

3. Programmed cell death morphology in tobacco cells.

4. Programmed cell death eliminates unwanted cells
Sculpting the digits in the developing mouse paw by apotosis
불필요 세포/조직/기관제거
세포수 조절 (간세포 분열/phenobarbital)
Quality control: B-/T-lymphocyte cell 제거
골수세포: 백혈구 제거
Figure Molecular Biology of the Cell (© Garland Science 2008)

5. Apoptotic Cells Are Biochemically Recognizable
Markers of apoptosis
TUNEL technique
Phosphatidylserine: 세포막 안쪽 바깥: Annexin V로 검출
“eat me” signal
“Don’t eat me” signal
Figure 18-4a Molecular Biology of the Cell (© Garland Science 2008)

6. Apoptotic Cells Are Biochemically Recognizable
Markers of apoptosis
Positively charged 형광색소
: 미토콘도리아 inner membrane 의 안쪽
Cytochrome C: released from the intermembrane space of mitochondria
Figure 18-4b Molecular Biology of the Cell (© Garland Science 2008)

7. Procaspase activation during apoptosis
Apoptosis Depends on an Intracellular Proteolytic Cascade That Is Mediated by Caspases
Caspase:
Procaspase activation during apoptosis
Figure 18-5a Molecular Biology of the Cell (© Garland Science 2008)

8. Procaspase activation during apoptosis
Apoptosis Depends on an Intracellular Proteolytic Cascade That Is Mediated by Caspases
Procaspase activation during apoptosis
Caspase recruitment domain: activation complex
Cytoskeleton
Cell-cell adhesion proteins
endonuclease
Figure 18-5b Molecular Biology of the Cell (© Garland Science 2008)

9. Cell-Surface Death Receptors Activate the Extrinsic Pathway of Apoptosis
The extrinsic pathway of apoptosis activated through Fas death receptors
Tumor necrosis fctor receptor familiy
DISC: Death-inducing signaling complex
Decoy receptor
FLIP blocking protein
Figure Molecular Biology of the Cell (© Garland Science 2008)

10. The Intrinsic Pathway of Apoptosis Depends on Mitochondria
Release of cytochrome c from mitochondria during apoptosis
bind procaspase-activating adapter protein(Apaf) apoptosome 형성
 Recruit initiator procaspase proteins (procaspase-9)
Figure Molecular Biology of the Cell (© Garland Science 2008)

11. The Intrinsic Pathway of Apoptosis Depends on Mitochondria
Figure Molecular Biology of the Cell (© Garland Science 2008)

12. Apoptosis 효소?

13. Bcl2 Proteins Regulate the Intrinsic Pathway of Apoptosis
The three classes of Bcl2
Figure Molecular Biology of the Cell (© Garland Science 2008)

14. Bcl2 Proteins Regulate the Intrinsic Pathway of Apoptosis
The role of BH123 pro-apoptotic Bcl2 proteins(mainly Bax and Bak) in the release of mitochondrial intermembrane proteins in the intrinsic pathway of apoptosis
Figure Molecular Biology of the Cell (© Garland Science 2008)

15. Bax, Bak
Bax
Bound to mitochondrial outer membrane
Bak
Located in cytosol, transport into mitochondira after apoptotic signaling
Both work on ER and nuclear membrane, activated by ER stress release Ca++ and intrinsic apoptotic pathway

16. Bcl2 Proteins Regulate the Intrinsic Pathway of Apoptosis
How pro-apoptotic BH3-only and anti-apoptotic Bcl2 proteins regulate the intrinsic pathway of apoptosis
Figure 18-11a Molecular Biology of the Cell (© Garland Science 2008)

17. Bcl2 Proteins Regulate the Intrinsic Pathway of Apoptosis
How pro-apoptotic BH3-only and anti-apoptotic Bcl2 proteins regulate the intrinsic pathway of apoptosis
Figure 18-11b Molecular Biology of the Cell (© Garland Science 2008)

18. Bid is the link between the two pathways
Death receptor extrinsic pathway
The initiator caspase, caspase-8 cleasve Bid producing tBid
tBid translocates to mitochondria inhibit bcl2
Bid: a proapoptotic BHS-3-only protein

19. IAPs Inhibit Caspases
A proposed model for the roles of IAPs and anti-IAPs in the control of apoptosis in mammalian cells
IAP: Inhibitor of apoptosis
first identified from vaculovirus.
Figure 18-12a Molecular Biology of the Cell (© Garland Science 2008)

20. IAPs Inhibit Caspases
A proposed model for the roles of IAPs and anti-IAPs in the control of apoptosis in mammalian cells
Figure 18-12b Molecular Biology of the Cell (© Garland Science 2008)

21. Extracellular Survival Factors Inhibit Apoptosis in Various Ways
The role of survival factors and cell death in adjusting the number of developing nerve cells to the amount of target tissue
Figure Molecular Biology of the Cell (© Garland Science 2008)

22. Extracellular Survival Factors Inhibit Apoptosis in Various Ways
Three ways that extracellular survival factors can inhibit apoptosis
Figure Molecular Biology of the Cell (© Garland Science 2008)

23. Bak/bax double mutant in mouse
Cannot activate intrinsic apoptosis
But without survival signal, nutrient import is not efficient
Autophagedie from starvation

24. Figure Q18-1 Molecular Biology of the Cell (© Garland Science 2008)

26. UV illumination to human Hela Cells  within 24h apoptosis in all cells  from 6 h after illumination to 24 h
Slow apoptosis? or
Gradual apoptosis in cell population?

27. Figure Q18-2 Molecular Biology of the Cell (© Garland Science 2008)

28. Apoptotic-like regulation of programmed cell death in plants
Apoptosis (2010) 15:249–256
Apoptotic-like regulation of programmed cell death in plants
Protoplast condensation, nuclear condensation, fragmentation
A central regulatory role for the mitochondria
The degradation of the cell and its contents by PCD associated proteases.
Caspase-like
Study using caspase inhibitor, substrate
Lack in caspase ortholog from Arabidopsis genome
No evidence that cyt c can directly activate AL-PCD proteases.
No Bcl2 family homologs identified
Involvement of chloroplast?

29. Schematic representation of AL-PCD
Fig. 1 Schematic representation of AL-PCD. Having perceived a
death stimulus, plant cells can undergo AL-PCD resulting in a
distinctive corpse morphology. It is thought that the mitochondrion
plays a role in integrating signals generated through stress or
developmental signals, thus determining whether the cell activates
it’s PCD pathway or not and the chloroplast may also be an important
integrator of stress responses in plant cells. A calcium influx is the
earliest event detected and similar to animal cells, cyt c is released
rapidly from the mitochondria in the early stages of AL-PCD but
unlike the animal system, does not appear to be responsible for
activating a caspase-driven cascade of events, which leads to PCD,
but rather may serve to amplify the death process. Cyt c release will
disrupt the electron transport chain resulting in generation of ROS. As
well as a signalling molecule, which can lead to opening of the PTP
and release of cyt c, more ROS can be generated in this way, causing
a feedback loop that amplifies the original death signal. The
chloroplast is also a source of ROS and most probably contributes
to this feedback loop. We also know that a Mg2?-dependent nuclease
which also normally resides in the mitochondrial intermembrane
space can be released, causing HMW DNA cleavage (picture of cells
courtesy of Siamsa Doyle)
MMP: mitochondrial membrane permeablization
PTP: the perability transition pore

30. Caspase-independent DNA degradation
Endo G
No homolog in plant
Mito IMS contain strong Mg2+ dependent nuclease activity
AIF/monodehydroascorbate reductase
5 homologs in Arabidospsis
Antioxidant pathway
DNA-binding defective AIF fails to induce cell death

31. Metacaspases 9 metacaspases in Arabidopsis
Arginine instead of Aspartic acid
No caspase substrate clevage, no inhibition by caspase inhibitors
Involvement in PCD of Arabidopsis
Natural substrates?
TSN(Tudor staphylococcal nuclease) in Norway spruce (유럽가문비)
hTSN: caspase substrate, involved in PCD