The Mechanisms involved in apoptosis
Apoptosis, derived from the Greek word for a natural process of leaves falling from trees or petals from ?owers. Apoptosis is the natural process of programmed cell death in a multicellular body. This mechanism removes damaged cells from the body. It is enormously important in right functioning of the body. In early development of embryo cells between finger and toes are separate by apoptosis and in immune system development, where insufficient T -cell are destroyed in thymus to avoid autoimmunisation.
Apoptosis process can be distinguished into three stages: signal, execution, elimination. The signal can be cause by intracellular or extracellular triggers, like cell damage, cellular stress and viral infection. This signal activates protein Caspase 3, which is an execution for the cell. Caspase 3 activate one of two enzymes – proteases or nucleases, which desaturase protein and nucleic acid, respectively. During the apoptosis in the cells cloud some morphological changes. Cytoplasm and chromatin in the nucleus condenses and the cell surface starts to become convoluted. The cell shrink, show deformation and loses contact to its neighbouring cells .The cell starts to degrade forming apoptotic blebs. The cell crack into small parts, called apoptotic bodies which contain cytosol, the condensed chromatin, and organelles. This crosslinked remnant are engulfed by phagocytes and digested.
The cell death signal is transmitted through an extrinsic or intrinsic pathway. The extrinsic pathway involves death signal of extracellular origin. Fas ligand binds to death domain receptors located on the cell membrane. This receptor activates Death-inducing signal complex, which activate Caspase 3. In Intrinsic pathway death signal is derived from protein intracellular factors that arise in processes associated with mitochondria. This protein activate proteases that create pore in the mitochondria, causing leakage of Cytochrome C which is death signal for the cell, as activate Caspase 3. All of signalling cascades eventually leads to same elimination and clearing process.
Apoptosis is a natural regulator of many processes in the human body.Natural development process is a different cause of cell death. Skin cells begin their lives in the deepest layers of the skin, then move towards the surface, undergoing apoptosis along the way. Dead cells form the outer protective layer of the skin – the epidermis.
Eye lenses, which form during embryonic development, are made of apoptotic cells. The cytoplasm of such cells has been replaced with a colorless protein called crystalline.
A difference way of cells death is for example necrosis. The cells die in an uncontrolled manner. Because of this, cell fall into pieces and release their content which destroy other nearby cells and tissues. Apoptosis can be compared to planned, controlled cell suicide, aimed at the good of the whole organism for example kill cancerous cells.
In this process an adult human loses between 50 and 70 billion cells daily due the apoptosis for the maintenance of homeostasis and for specific tasks such as the regulation of immune cell selection and activity (Fadeel, 1999b). Dysregulated apoptosis is the reason of a large number of disease