plasma membrane phospholipid scrambling

Definition

Target type: biologicalprocess

The movement of a population of phospholipid molecules from one leaflet of the plasma membrane bilayer to the opposite leaflet, resulting in loss of lipid asymmetry and surface exposure of phosphatidylserine (PS) and phosphatidylethanolamine (PE). [GOC:cjm, PMID:20043909, PMID:20302864]

Plasma membrane phospholipid scrambling is a critical process in cellular signaling and membrane trafficking. It involves the rapid redistribution of phospholipids within the plasma membrane, specifically the movement of phosphatidylserine (PS) from the inner leaflet to the outer leaflet. This translocation typically occurs in response to various stimuli, including apoptotic signals, oxidative stress, and calcium influx.

The key enzyme responsible for phospholipid scrambling is scramblase. Scramblase is a transmembrane protein that facilitates the bidirectional movement of phospholipids across the membrane bilayer, independent of ATP hydrolysis. This means that scrambling is a passive process, driven by the concentration gradient of phospholipids.

When scramblase is activated, it allows the movement of PS, normally confined to the inner leaflet of the plasma membrane, to the outer leaflet. This exposes PS on the cell surface, which serves as a signal for various cellular processes. For example, in apoptosis, the exposure of PS on the outer leaflet acts as an "eat me" signal, attracting phagocytes to engulf the dying cell.

Phospholipid scrambling also plays a role in membrane fusion and vesicle trafficking. The redistribution of phospholipids can influence the curvature and fluidity of the membrane, facilitating the formation of vesicles and their fusion with other membranes.

The regulation of scramblase activity is complex and involves various signaling pathways. Calcium ions play a significant role in activating scramblase. Other factors, such as phosphorylation and interactions with other proteins, can also modulate scramblase activity.

In summary, plasma membrane phospholipid scrambling is a dynamic process that involves the redistribution of phospholipids, primarily PS, across the membrane bilayer. This process is regulated by various stimuli and plays a critical role in cellular signaling, membrane trafficking, and apoptosis.'
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Proteins (1)

Compounds (19)