phosphatidylserine exposure on apoptotic cell surface

Definition

Target type: biologicalprocess

A phospholipid scrambling process that results in the appearance of phosphatidylserine on the outer leaflet of the plasma membrane of an apoptotic cell, which acts as an 'eat-me' signal for engulfing cells. Phosphatidylserine is exposed on the apoptotic cell surface by a phospholipid scramblase activity. [GOC:mah, GOC:mtg_apoptosis, GOC:rk, PMID:11536005]

Phosphatidylserine (PS) is a phospholipid normally localized to the inner leaflet of the plasma membrane in healthy cells. During apoptosis, a complex series of events leads to the translocation of PS from the inner leaflet to the outer leaflet of the plasma membrane, where it becomes exposed to the extracellular environment. This exposure is a hallmark of apoptosis and serves several critical roles:

1. **Recognition by phagocytes:** PS on the cell surface acts as an "eat me" signal, recognized by specific receptors on phagocytic cells, such as macrophages. This recognition triggers the engulfment of apoptotic cells, preventing the release of cellular contents and promoting tissue homeostasis.

2. **Activation of the coagulation cascade:** Exposure of PS can also trigger the coagulation cascade, leading to the formation of a blood clot at the site of cell death. This helps to contain the damage and prevent further bleeding.

3. **Induction of immune tolerance:** Apoptotic cells undergoing PS exposure often display immunosuppressive properties. This may be due to the release of specific factors or the modulation of immune cell responses.

The mechanism of PS exposure during apoptosis involves multiple factors:

* **Scramblase activation:** Scramblases are enzymes that facilitate the bidirectional movement of phospholipids across the plasma membrane. During apoptosis, scramblase activity is increased, promoting the movement of PS from the inner to the outer leaflet.

* **Flippase inhibition:** Flippases are enzymes that actively transport PS from the outer to the inner leaflet. During apoptosis, flippase activity is inhibited, contributing to the accumulation of PS on the outer leaflet.

* **Membrane blebbing:** As apoptosis progresses, the cell membrane undergoes blebbing, forming outward protrusions. These blebs often contain high concentrations of PS, further increasing its exposure.

The exposure of PS on the surface of apoptotic cells is a tightly regulated process that plays a crucial role in the removal of damaged cells, the maintenance of tissue integrity, and the prevention of inflammation and immune responses. This process is essential for normal cellular turnover and the prevention of diseases.'
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Proteins (1)

Compounds (8)