what is apoptosis, its mechanism and importance of it. you will get to know about it in this presentation

1. Apoptosis
BY
Robin Singh
B.Sc (hons) Biochemistry

2. Contents
• Introduction
• Impotrance of Apoptosis
• Mechanism
• Extrinsic Pathway
• Intrinsic Pathway
• Apoptosis related Disorders

3. Definition:
• the death of cells which occurs as a normal and controlled part of an
organism's growth or development.
(Wikipedia)
• Cells die when they fail to receive life maintaining signals or when
they receive a death signal, such programmed death of cell is called
Apoptosis.
(Lodish et al. ; 2004)

4. • Cell death may occur due to
• Accident or damage due to traumatic event.
• Death by suicide.
• Suicidal death also occurs in two ways, i.e. Apoptosis and Necrosis.

7. Importance

8. • helps to shape organs and carve out the interdigital webs of the
fingers and toes.
• Both the nervous system and the immune system arise through
overproduction of cells followed by the apoptotic death

9. • Resorption of tail in
tadpole
• Shedding off of
endometrium in the
process of
menstruation

10. • Useful for killing virus infected cells.
• Killing cancer cells.
• Killing DNA damaged cells.

11. Mechanism

12. Extrinsic Pathway

13. • Extrinsic pathway is initiated by external signal.
• Most common extrinsic factor for initiation is TNF(alpha) secrete by T-killer
cells.
• Killler lymphocyte attaches to death receptor’s of the diseased cell through
Fas ligands or TNF.
• The FADD adaptor protein is attached to death receptor (in cytoplasm).
• Eventually inactivated procaspase-8 or 10 attaches to FADD to activate
itself.
• Activated caspase-8 breaks other proteins and actin cytoskeleton bringing
the death for cell.

14. Intrinsic Pathway

15. • Most of the times intrinsic pathway is initiated due to damage of DNA
in the cell.
• DNA lesions leads to the activation of ATM which activates tumor
suppressor p53 protein.
• p53 activates protein BAX which form pores on outer mitochondrial
membrane.
• This leads to leakage of calcium ion, hydrogen ions along with protein
cytochrome – c.
• Cytochrome C forms ‘Apoptosome’ by attaching to adaptor protein.

16. • Apoptosome activates Caspases especially caspase-9 which cleaves
other protein and activates other caspases continuing the cycle.
• Caspase also cleaves the actin cytoskeleton, causing shrinkage of the
cell and its death.

17. Apoptosis related Disorders

18. • Neurodegenerative diseases such as Alzheimer's disease, Parkinson's
disease, and amyotrophic lateral sclerosis.
• Ischaemic injury after myocardial infarction, stroke, and reperfusion.
• Autoimmune diseases such as hepatitis and graft versus host.
• Decreased or inhibited apoptosis is a feature of many malignancies,
autoimmune disorders such as systemic lupus erythematosus, and
some viral infections.
• The role of apoptosis in cancer has probably received the greatest
research effort.
• Increased apoptosis is characteristic of AIDS

19. END