Apoptosis content.ppt

self death cellular sucide

1. Apoptosis

2. Literal sense

3. Programmed cell death
Internally controlled “suicide” program
Cells are removed with minimal disruption
of the surrounding tissue

4. PathologicalPhysiological

5. Physiological
Potentially harmful cells
Outlived their usefulness
Maintain a steady number of cells
Pathological
Damaged beyond repair

6. EMBRYOGENESIS

7. Growth factor deprivation
Involution of
hormone
dependent
tissues
Lymphocytes
not stimulated
by antigens
and cytokines
Neurons
deprived of
nerve growth
factors

8. Cell loss in proliferating populations
•Eliminate self reactive lymphocytes
•Cell death by induced cytotoxic T lymphocytes
(defense against virus / tumorogenisis)

9. Genetically altered beyond repair
DNA damage (Direct or Free radical)
Radiation
Cytotoxic drugs
Extreme tempetature
Hypoxia

10. Accumulation of misfolded proteins
Arise because of mutations in the genes coding
these proteins or extrensic factors like free
radicals
Cell injury in infections
Atropy in parynchyma after duct obstruction

12. G1 S G2 M
p53
Repair Attempted
NO
YES

13. Chaperones control normal folding
Misfolded polypeptides are ubiquitinated and
targeted for proteolysis
If accumulated ER stress occurs
That triggers unfolded protein response i.e
increase production of chaperones and retard
protein translation
If unable to cope caspase activation and
apoptosis occurs

14. CASPASE
Mitochondrial pathway Death receptor pathway
Both pathways are not mutually exclusive with p53 causing cross over to
death receptor pathway.
Cystene protease that cleave proteins after aspartic residues
Cell Death by Apoptosis
Activation of caspase is the fundamental event of apoptosis

15. Caspase-1 (ICE)
Caspase-2 (ICH-1, Nedd-2)
Caspase-3 (CPP32, Apopain, Yama)
Caspase-4 (ICH-2, TX, ICEre
ıı
)
Caspase-5 (ICErel
ııı
, TY)
Caspase-6 (Mch2)
Caspase-7 (ICE-LAP3, Mch3, CMH-1)
Caspase-8 (FLICE, Mch5, MACH)
Caspace-9 (Mch6, ICE-LAP6)
Caspase-10 (Mch4)

16. Caspase activation
a.Proteolytic cleavage
e.g. pro-caspase 3
b.Induced proximity
e.g. pro-caspase 8
c.Oligomerization,
e.g. cyt c, Apaf-1 &
caspase 9

17. Inflammatory Caspases: -1, -4, and -5


Initiator Caspases: -2, -8, -9, and -10
Long N-terminal domain
Interact with effector caspases
Effector Caspases: -3, -6, and -7
Little to no N-terminal domain
Initiate cell death

18. Cytochrome C
antagonists of
endogenous
cytosolic
inhibitors of
apoptosis
Mitochondria has several proteins capable of
inducing apoptosis
Bcl 2 and bcl XL
antiapoptotic
BAX and BAK
( Pro apoptotic)

19. Dimerize and
insert into
membrane of
mitochondria
Permiability transition
pore Channel activated
(voltage gated channel)
Cytochrome C
CASPASE
ACTIVATION

20. Surface molecules trigger apoptosis
Members of TNF family
Ex: Type 1 TNF and Fas (CD95)
Normally present in cytoplasmic region
On Activation move to surface

21. FasLigand
membrane
protein on
activated T
lymphocytes
activate caspase-8 activating caspase cascade by activating
member of Bcl-2 family called Bid
Bind to Fas

22. Active enzymatic process
Nucleoproteins
are broken down
Cell organelles are
fragmented
Nuclei show various stages of condensation
and aggregation ultimately karyorrhexis.

24. Plasma membrane remains intact
But become avid targets to phagocytosis by flip
out of phosphotidyl serine on the inner leaflet of
plasma membrane
These are recognised by macrophages
Also secrete soluble factors that recruit
phagocytes
Express adhesive glycoproteins recognised by
phagocytes and macrophages

25. Dead cells cleared rapidly before contents
leak out
Hence does not elicit inflammatory
reaction
Hence differs from necrosis

26. CASPASE
.
Cleavage of nuclear LAMINS is involved in chromatin condensation
and nuclear shrinkage.
Cleavage of the inhibitor of the DNase CAD (caspase-activated
deoxyribonuclease), ICAD causes the release of the endonuclease,
which fragment DNA.
Cleavage of cytoskeletal proteins such as actin, plectin, Rho
kinase 1 (ROCK1) and gelsolin leads to cell fragmentation, blebbing
and the formation of apoptotic bodies.

28. Constant number of cells in an organism.
Cell death = Cell proliferation
Cell
Death
Growth
Survival
Proliferation

29. What happens when things become imbalanced?
Cell
Death
Growth
Survival
Proliferation
Cell
Death
Growth
Survival
Proliferation
Alzheimer’s
Parkinson’s
Cancer

30. Resistance of tumour cells to apoptosis is an
essential feature of cancer development
Loss of apoptosis can promote tumor
Initiation
Progression
Treatment resistence

31. Chemotherapy, irradiation and other stimuli
can initiate apoptosis through the
mitochondrial (intrinsic) pathway.
Pro-apoptotic BCL2 family proteins are
activated by treatment ---- caspase cascade
---- death of cell

32. Disrupted apoptotic cycle can effect sensitivity of
cancer drugs
As multiple drugs effect same mechanism it
causes multidrug resistance
Sufficient doses of almost all anticancer drugs
induce apoptosis by alternate pathway
indipendent of p53 pathway
Contribution of p53 is dependent on
Agent
Dose
mutational background

33. The best-defined mechanism of therapy-induced
cellular stress induced cance cell death.
Chemotherapeutic drugs (for example, the
nucleotide analogue 5-FU) induce CD95 by a
transcriptionally regulated, p53-dependent
mechanism.
They also engage the SAPK/JNK pathway
Leads to upregulation of CD95L
Allows the cells to either commit suicide or kill
neighbouring cells.

34. p53 induce the expression of proteins involved in
the mitochondrial pathway — BAX, NOXA, PUMA and
P53aip1
death receptor pathway — CD95, TRAIL-R1 and TRAIL-
R2.
When p53 is damaged it cannot induce apoptosis
so cell survive
Subsequent mutations develop
Progresses to malignancy

35. overexpression of anti-apoptotic genes
follicular B-cell lymphoma t(14;18), couples BCL2
gene to immunoglobulin heavy chain locus, leading
to enhanced BCL2 expression.
EBV and HHV8 encode proteins that are
homologues of BCL2.
BHRF1 from EBV and KSbcl-2 (vBcl-2) from HHV8 —
have an anti-apoptotic function and enhance
survival of the infected cells.

36. soluble receptors that act as decoys for death
ligands.
soluble CD95 (sCD95) and decoy receptor 3 (DcR3)
shown to competitively inhibit CD95 signalling.
sCD95 is expressed in various malignancies, and
elevated levels can be found in the sera of cancer
patients.
.

37. associated with poor prognosis in melanoma
patients
It is genetically amplified in several lung and
colon carcinomas
overexpressed in several adenocarcinomas,
glioma cell lines and glioblastomas.

38. the pro-apoptotic BCL2 family member BAX is
mutated.
 Frameshift mutations
loss of expression and function.
Reduced BAX expression is associated with a
poor response rate to chemotherapy and
shorter survival

39. Bcl2 shows discrepencies in effect on tumor
management
Studies have shown a correlation between
high levels of BCL2 expression and the
severity of malignancy of human tumours.
a high level of BCL2 expression is associated
with a poor response to chemotherapy and
seems to be predictive of shorter, disease-
free survival.
While in some cases Bcl-2 has been shown to
cause chemoresistence in other settings it is
shown to improve prognosis.

40. Clinical studies examine single alterations
Cannot exclude extragenic mutations in the same
pathway
Thus almost impossible to determine negative
results
Ex: murine lymphomas harbouring INK4a/ARF
have defective p53 but harbour wild type p53
hence classified as p53 normal
Extracellular survival factors affect cell
death
Cell density
microenvironment

41. Deregulated proliferation alone is not sufficient
for tumour formation
Overexpression of growth-promoting oncogenes
— such as c-MYC, E1A or E2F1 — sensitizes cells
to apoptosis.
Besides the expression of proteins that promote
cell proliferation, tumour progression requires
the expression of anti-apoptotic proteins or the
inactivation of essential pro-apoptotic proteins.

42. Apoptosis limited role in solid tumors
Side effects of cancer drugs are because
along with cancer cells they also target
normal cells like intestine and bone marrow

43. Caspase 10 mutation lymphoproliferative
syndrome type 2
Frameshift in caspase5 HNPCC, GI and
endometrial tumors

44. Death receptors Fas/CD95, TNFR1, DR3, DR4, DR5
TNFalpha trimerizes its ligand TNFR1
Recruts signal transducing TRADD
TRADD Recruits RIP and TRAF-2
Activates NF-kB which supress TNFa induced apoptosis
TRADD activate FADD thatactivate caspase 8 --- apoptosis
FADD disruption can prevent apoptosis (does not occur in
oncogenic mutations but occurs in tumor development )

45. Cytokines like IL6 can inhibit apoptosis
Adenovirus induce cells to bypass apoptosis
and replicate by E1B oncoprotein inducing
cells to enter s phase

46. Most mutations occur upstream
Machinery is retained
Tumor specific alterations in apoptotic
programmes
Ex: Adenoviral gene transfer in ovarian cancer
Ad-DF3-Bax eradicated >99% of these tumors in nude mice
Ex2: Taxanes known to phosphorylate and inactivate bcl2
inactivating NF-kb enhances chemo induced cell death
Restoring of pro-apoptotic p53
Activating death ligands hence p53 indipendent
death as normal cells are resistent to TRAIL
induced apoptosis in view of decoy receptors that
compete with DR4 and DR5

47. Oncogene induced apoptosis
Ras and its appln