Apoptosis "the programmed cell death"

1. APOPTOSIS
Programmed cell death

2. Cell death...?
 Cell death is the event of a biological cell ceasing to carry out its function
 Cell death in higher plants has been widely observed in predictable pattern
throughout development and in response to pathogenic function

3. Types of
cell death
Programm
ed cell
death
oNon-
inflammatory
apoptosis Autophagy
oPro
oinflammator
y
Necroptosis:
A type of
programmed
necrosis
Pyroptosis:A
type of
programmed
necrosis
Non
programmed
cell death
oNecrosis

4. Necrosis
• Necrosis has been defined as a type of uncontrolled
cell death can occur in response in infection ,toxin,
chemicals ,injury , or lake of blood supply.
• Morphologically , necrosis is associated with
cytoplasmic swelling ,rupture of the plasma
membrane, swelling of cytoplasmic organelles and
moderate chromatin condensation .

5. Autophagy
 The world
autophagy is
derived from
Greek words
“auto” meaning
self and “phagy”
meaning eating.
 Consumption of
the body’s own
tissue as a
metabolic process
occurring in
starvation and
certain disease.

7. Cells respond to
stress in a variety of
ways ranging
from activation of
pathways that
promote survival to
eliciting
programmed cell
death that
eliminates damaged
cells

8. Apoptosis
 Individual cell are induced to commit
suicide
• Apoptosis refer to active programmed cell death

9. APOPTOSIS :
MORPHOLOGICAL CHANGES
 Early: chromosome condensation ,cell body shrink .
 Later : membranes become irregular –Blebbing ;
Nucleus and cytoplasm fragment – apoptotic bodies .
At last : Phagocytosed

10. THE ENZYMATIC REGULATION OF
APOPTOSIS
 Apoptosis is initiated by activation of a family of proteases called
caspases.
 These are enzyme that are synthesized and stored in a cell as
inactive procaspases.
 Once activated the enzyme cleave and activate other procaspases
, triggering a cascade that rapidly break down proteins within the
cell.
 The cell thus break itself , and its remains are rapidly digested by
neighbouring phagocytic cells .

11. THE MECHANISMS OF
APOPTOSIS
 This process involves a specific proteolytic cascade
 There are 3 different mechanisms by which a cell commits
suicides by apoptosis
 By single arising within the cell ;
 By death activators binding to receptors at the cell surface :
- TNF –α
- Lymphotoxin
-Fas ligand (Fasl)
 Third that may be triggered by dangerous reactive oxygen species

12. The distinct pathways converges on
caspase activation
• Intrinsic pathway
Mitochondrial pathway
• Extrinsic pathway
The death receptor pathway

13. Intrinsic Pathway
 Initiated from within the cell.
 Activated in response to signals such as
DNA damage ,loss of cell survival factors,
cell stress.
 Hinges on balance between pro and
antiapoptotic signals of Bcl-2 family.
 Apaf-1,cytochrome-c ,ATP(apoptosome)
activate procaspase-9 complex.
 Pro apoptotic proteins released which
activate caspase proteases.

15. Extrinsic Pathway
 Begin outside the cells.
 Activation of death receptor (Fas-
R,TNF-R, DR-3,DRY/DR5)by death
ligands (Fas-l, TNF-alpha
,Apo3L,Apo2L) play major role .
 Death induced signalling complex
(DISC) activated.
 On DISC activation same effector
pathway as intrinsic pathway is
adopted .

18. Why do multicellular organisms need to
regulate the death of their cell.?
 To allow to body structures to grow and develop correctly.
 To remove body structures that are no longer required .
 To regulate the size of cell population in adult bodies cell
proliferation must be balanced with cell death .
 This allow organism to precisely control the size of their
tissue and organs .