cholesterol efflux

Definition

Target type: biologicalprocess

The directed movement of cholesterol, cholest-5-en-3-beta-ol, out of a cell or organelle. [GOC:sart]

Cholesterol efflux is a critical process that removes excess cholesterol from cells, preventing its accumulation and the development of atherosclerosis. The process involves a series of steps mediated by specific proteins and involves the coordinated action of different cell types:

1. **Cellular Cholesterol Mobilization:** Cholesterol is mobilized from intracellular compartments like the endoplasmic reticulum and lysosomes, where it is stored. This step involves proteins like ATP-binding cassette transporter A1 (ABCA1) and ABCA7, which bind to cholesterol and facilitate its movement to the cell membrane.

2. **Cholesterol Transport to Acceptor Molecules:** Once at the cell membrane, cholesterol is transferred to acceptor molecules in the extracellular environment.
* **High-density lipoproteins (HDL):** HDL particles are the primary acceptors of cholesterol from cells. They are synthesized in the liver and have a structure that allows them to bind and transport cholesterol. ABCA1 is crucial for the transfer of cholesterol to HDL, forming nascent HDL particles.
* **Other Acceptors:** Other acceptors include scavenger receptor BI (SR-BI), which can directly take up cholesterol from cells, and various lipoproteins that can exchange cholesterol with HDL.

3. **Reverse Cholesterol Transport:** HDL particles with acquired cholesterol travel back to the liver through the bloodstream. This process is known as reverse cholesterol transport.
* **Cholesterol Esters:** In the plasma, cholesterol is converted to cholesterol esters by the enzyme lecithin-cholesterol acyltransferase (LCAT), making it more stable and allowing HDL to carry more cholesterol.
* **Delivery to Liver:** HDL particles deliver their cholesterol load to the liver, either directly or through exchange with other lipoproteins. The liver then processes the cholesterol and either uses it for biosynthesis or excretes it in bile.

4. **Cellular Cholesterol Homeostasis:** By removing excess cholesterol from cells, cholesterol efflux helps maintain cellular cholesterol homeostasis and prevent the buildup of cholesterol in the cell membrane and other compartments. This is essential for normal cell function and prevents the development of atherosclerosis.

This complex and well-regulated process plays a vital role in protecting against cardiovascular disease by removing excess cholesterol from cells and preventing its buildup in the arteries.'
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Proteins (5)

Compounds (42)