recognition of apoptotic cell

Definition

Target type: biologicalprocess

The process in which a cell interprets signals (in the form of specific proteins and lipids) on the surface of a dying cell which it will engulf and remove by phagocytosis. [GOC:rk, PMID:15536015]

Recognition of apoptotic cells is a complex and tightly regulated process that involves a series of molecular interactions between apoptotic cells and surrounding phagocytes. These interactions are essential for the efficient and timely removal of apoptotic cells from the body, preventing inflammation and maintaining tissue homeostasis. The process can be broadly divided into four main stages:

1. **Exposure of "Eat Me" Signals:** Apoptotic cells undergo a series of biochemical changes that lead to the externalization of specific molecules that act as "eat me" signals. These signals include phosphatidylserine (PS), which normally resides on the inner leaflet of the plasma membrane but is flipped to the outer leaflet during apoptosis, calreticulin, which is exposed on the cell surface, and oxidized lipids, which are produced as a result of oxidative stress.

2. **Binding of Phagocytes:** Phagocytes, such as macrophages and neutrophils, express a variety of receptors that recognize these "eat me" signals. These receptors include:
* **Phosphatidylserine receptors:** These receptors, such as TIM-4, BAI1, and Stabilin-2, directly bind to PS exposed on the apoptotic cell surface.
* **Calreticulin receptors:** These receptors, such as LRP1 and CD91, bind to calreticulin on the apoptotic cell surface.
* **Other receptors:** Other receptors, such as CD36, SR-A, and scavenger receptors, recognize oxidized lipids and other apoptotic cell-associated molecules.

3. **Phagocytosis and Engulfment:** Upon binding to apoptotic cells, phagocytes initiate the process of engulfment. This process involves cytoskeletal rearrangements and the formation of pseudopods that surround and enclose the apoptotic cell. The engulfed apoptotic cell is then internalized into the phagocyte, forming a phagosome.

4. **Phagosome Maturation and Degradation:** Once the apoptotic cell is internalized, the phagosome undergoes a series of maturation steps that involve fusion with lysosomes. This process leads to the degradation of the engulfed apoptotic cell by lysosomal enzymes.

Throughout the process, various signaling pathways are activated, contributing to the regulation and efficiency of apoptotic cell recognition and clearance. These include integrin-mediated signaling, signaling pathways involving adaptor proteins like GULP, and intracellular signaling pathways involving kinases and phosphatases. The precise molecular mechanisms and the relative importance of different receptors and signaling pathways vary depending on the cell type, the context of cell death, and the specific phagocyte involved.'
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Proteins (1)

Compounds (1)