programmed cell death

Definition

Target type: biologicalprocess

A process which begins when a cell receives an internal or external signal and activates a series of biochemical events (signaling pathway). The process ends with the death of the cell. [GOC:lr, GOC:mtg_apoptosis]

Programmed cell death (PCD) is a highly regulated process essential for multicellular organisms. It involves a series of biochemical events that lead to the dismantling of the cell's components and ultimately its demise. PCD plays a critical role in various physiological processes, including development, tissue homeostasis, and immune responses.

There are two main types of PCD: apoptosis and necrosis.

Apoptosis is a highly controlled process characterized by a series of morphological changes, including cell shrinkage, chromatin condensation, and DNA fragmentation. It is often described as a "clean" death, as the cell is broken down into small membrane-bound vesicles that are readily phagocytosed by neighboring cells, minimizing inflammation.

Necrosis, on the other hand, is a form of cell death that results from severe injury or stress, such as trauma, infection, or toxins. It is characterized by cell swelling, organelle breakdown, and the release of cellular contents into the surrounding environment, leading to inflammation.

Apoptosis is initiated by a cascade of signaling events that can be triggered by a variety of stimuli, including:

- Extrinsic pathways: triggered by external signals, such as death receptors on the cell surface, which bind to ligands from neighboring cells or the immune system.
- Intrinsic pathways: initiated by intracellular signals, such as DNA damage, hypoxia, or oxidative stress, which activate a series of intracellular signaling molecules.

Both extrinsic and intrinsic pathways converge on the activation of caspases, a family of cysteine proteases that play a central role in executing the apoptotic program. Caspases are activated in a proteolytic cascade, with upstream caspases activating downstream caspases, which then cleave specific target proteins, leading to the dismantling of the cell.

Apoptosis is tightly regulated by a complex network of signaling pathways that ensure its proper execution and prevent uncontrolled cell death. These pathways involve a variety of proteins, including:

- Bcl-2 family proteins: regulate the permeability of the mitochondrial membrane, which plays a crucial role in the intrinsic apoptotic pathway.
- IAPs (Inhibitors of Apoptosis Proteins): block the activation of caspases.
- Survival factors: promote cell survival by inhibiting apoptotic pathways.

PCD is a highly intricate process with profound implications for human health. Defects in PCD pathways can contribute to various diseases, including cancer, autoimmune disorders, and neurodegenerative diseases. Conversely, dysregulation of PCD can also lead to excessive cell death, contributing to conditions such as stroke, myocardial infarction, and organ failure.

Understanding the intricate mechanisms of PCD is crucial for developing effective therapeutic strategies for a wide range of diseases.'
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Proteins (2)

Compounds (115)