cell killing

Definition

Target type: biologicalprocess

Any process in an organism that results in the killing of its own cells or those of another organism, including in some cases the death of the other organism. Killing here refers to the induction of death in one cell by another cell, not cell-autonomous death due to internal or other environmental conditions. [GOC:add]

Cell killing, also known as apoptosis or programmed cell death, is a fundamental biological process that eliminates unwanted or damaged cells from the body. This process is tightly regulated and crucial for maintaining tissue homeostasis, development, and preventing disease.

Here's a detailed breakdown of the process:

1. **Initiation:** Cell killing can be triggered by various internal and external stimuli.
* **Internal Stimuli:** These include DNA damage, cellular stress, and growth factor deprivation.
* **External Stimuli:** These include cytotoxic chemicals, radiation, and immune system signals.

2. **Execution:** The execution phase involves a series of biochemical events that lead to cell death.
* **Caspase Activation:** Caspases are a family of proteases (enzymes that break down proteins) that play a central role in apoptosis. They are activated in a cascade, where one activated caspase triggers the activation of another.
* **Mitochondrial Membrane Permeabilization:** Mitochondria, the powerhouses of the cell, release proteins like cytochrome c into the cytoplasm, which triggers caspase activation.
* **DNA Fragmentation:** Caspases degrade DNA, leading to the characteristic fragmentation of the nucleus.

3. **Cellular Degradation:** The cell undergoes a series of morphological changes:
* **Cell Shrinkage:** The cell shrinks and condenses.
* **Blebbing:** The cell membrane forms protrusions called blebs.
* **Apoptotic Bodies:** The cell breaks up into membrane-bound fragments called apoptotic bodies.

4. **Phagocytosis:** Apoptotic bodies are rapidly engulfed by neighboring cells or macrophages, preventing inflammation and promoting tissue repair.

The precise mechanisms and pathways involved in cell killing vary depending on the cell type and the initiating stimulus. However, the core principles of caspase activation, mitochondrial involvement, and DNA fragmentation remain largely consistent.

Cell killing is a highly regulated process, and its dysregulation can lead to various diseases, including cancer, autoimmune disorders, and neurodegenerative diseases. The study of cell killing mechanisms is vital for understanding disease processes and developing new therapies.'
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