What are the most well-known death receptors? What does ‘All elements and molecules involved in programmed cell death are actors’ mean?

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9.2.7-The most well-known death receptors

Death receptors, adapter proteins, and proteolytic enzymes (Caspases) are the groups that work actively in programmed cell death. The receptors of the death signal in the cell (death receptors) are usually molecules that have important roles in the cell cycle.

The most well-known death receptors are as follows:

CD95 (APO-1/Fas), TRAIL (TNF Related Apoptosis-Inducing Ligand)-R1, TRAILR2, TNF-R1, DR3 and DR6.

The task of death receptors is to bind to the adapter proteins and transmit the death signal. The adapter proteins that receive a death signal bind to caspases and cause them to be activated. Caspases cleave proteins only in regions having aspartic acid. Caspases are not active in the cell until the death signal reaches the cell. Inactive caspases in the cell are called procaspases.

There are 3 groups of caspases in terms of structure and functions.
1. Caspases involved in the production of lymphokines (activating substances that are secreted by lymphocytes and that act as signals among immune system cells).
2. Executioner caspases
3. Activating caspases (They are in charge of transmitting signals and activating executioner caspases).

The caspases are activated by the release of cytochrome c into the cytoplasm. The caspase that receives the death signal is operated irreversibly and activates other caspases. The initiating caspases that receive and transmit the death signal bind to the adapter, causing the cell to go to death but they do not carry out the execution. However, they are responsible for activating caspases that will carry out the execution. Those who carry out the execution are the executive caspases. The activated caspase sequence also causes DNA degradation through the DNase (CAD) enzyme. Caspase inhibitors are in charge of inhibiting effector caspases and preventing programmed cell death (Apoptosis)1

The operation of the programmed death mechanism in the cell is like an action film. There are those who give the death order, intermediaries, assassins, executioners, the dead and the removal of the dead from the scene.

As it is seen, the operation of the programmed death mechanism in the cell is like an action film. There are those who give the death order, intermediaries, assassins, executioners, the dead and the removal of the dead from the medium.

All elements and molecules involved in programmed cell death are actors. They only do the assigned task. It is Divine Power that plans and writes the wise and orderly death scenario in the cell, assigns special tasks to different actors and draws the boundaries of the given tasks, sometimes stops the film and restarts it according to circumstances.

1.Tomatır A.G.T.,Klin J MedSci, 2003, 23, 499-508.

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