apoptotic process

Definition

Target type: biologicalprocess

A programmed cell death process which begins when a cell receives an internal (e.g. DNA damage) or external signal (e.g. an extracellular death ligand), and proceeds through a series of biochemical events (signaling pathway phase) which trigger an execution phase. The execution phase is the last step of an apoptotic process, and is typically characterized by rounding-up of the cell, retraction of pseudopodes, reduction of cellular volume (pyknosis), chromatin condensation, nuclear fragmentation (karyorrhexis), plasma membrane blebbing and fragmentation of the cell into apoptotic bodies. When the execution phase is completed, the cell has died. [GOC:cjm, GOC:dhl, GOC:ecd, GOC:go_curators, GOC:mtg_apoptosis, GOC:tb, ISBN:0198506732, PMID:18846107, PMID:21494263]

Apoptosis, also known as programmed cell death, is a highly regulated process of cellular self-destruction that plays a critical role in development, tissue homeostasis, and the elimination of damaged or unwanted cells. It is a fundamental biological process that ensures the integrity of multicellular organisms by removing cells that are no longer needed or that have become harmful.

Apoptosis is characterized by a series of biochemical events that lead to the dismantling of the cell in a controlled manner. These events include:

1. **Activation of caspases:** Caspases are a family of cysteine proteases that play a central role in apoptosis. They are activated in a cascade-like manner, with initiator caspases activating effector caspases.

2. **DNA fragmentation:** The activation of endonucleases leads to the cleavage of DNA into fragments of approximately 180 base pairs, resulting in a ladder-like pattern on electrophoresis.

3. **Cell shrinkage:** The cell shrinks in size due to the breakdown of the cytoskeleton and the condensation of the cytoplasm.

4. **Blebbing:** The plasma membrane begins to bulge outwards, forming protrusions called blebs.

5. **Apoptotic bodies:** The cell breaks down into small, membrane-bound vesicles called apoptotic bodies that contain cellular components.

6. **Phagocytosis:** Apoptotic bodies are efficiently phagocytosed by neighboring cells or specialized phagocytes, such as macrophages, preventing the release of cellular contents and inflammation.

Apoptosis can be triggered by a variety of stimuli, including:

- **Intrinsic pathway:** This pathway is initiated by internal cellular stress, such as DNA damage, hypoxia, or growth factor deprivation. It involves the activation of the mitochondrial pathway, leading to the release of cytochrome c and other pro-apoptotic proteins.

- **Extrinsic pathway:** This pathway is triggered by external signals, such as the binding of death ligands (e.g., TNF-α, FasL) to their receptors on the cell surface. This activates caspase-8, leading to the activation of the downstream apoptotic cascade.

Apoptosis plays a crucial role in:

- **Development:** Apoptosis is essential for sculpting organs and tissues during embryonic development, removing unnecessary or malformed cells.

- **Tissue homeostasis:** Apoptosis maintains the balance between cell proliferation and death, ensuring that tissues do not grow uncontrollably.

- **Immune response:** Apoptosis eliminates infected or damaged cells to prevent the spread of pathogens and inflammation.

- **Cancer prevention:** Apoptosis acts as a defense mechanism against cancer by eliminating cells with damaged DNA or uncontrolled growth potential.

Dysregulation of apoptosis can contribute to various diseases, including cancer, autoimmune disorders, and neurodegenerative diseases.'
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Proteins (153)

Compounds (2,776)