What is the Origin of SR-BI Selective Uptake?

This concept originates from lipid metabolism and cellular biology, following the discovery and characterization of the SR-BI receptor. The term highlights a distinct pathway for cholesterol delivery that contrasts with the endocytosis of LDL by the LDL receptor. Understanding this selective process is crucial for cardiovascular health and endocrine function.

What is the Mechanism of SR-BI Selective Uptake?

SR-BI is a high-affinity receptor located on the cell surface. When an HDL particle docks at the receptor, the SR-BI protein facilitates the movement of cholesterol esters across the cell membrane and into the cell's interior. The now lipid-depleted HDL particle remains in circulation, ready to accept more cholesterol from peripheral tissues. In steroidogenic organs, this cholesterol is the necessary precursor for the synthesis of all steroid hormones, including cortisol and testosterone.

SR-BI Selective Uptake ∞ Area

SR-BI Selective Uptake

Meaning

A specific cellular process, mediated by the Scavenger Receptor Class B Type 1 (SR-BI) protein, that allows for the direct transfer of cholesterol esters from high-density lipoprotein (HDL) particles into target cells, predominantly hepatocytes (liver cells) and steroidogenic cells (e.g., in the adrenals and gonads). This mechanism is “selective” because it permits the uptake of cholesterol without the internalization or degradation of the entire HDL particle. SR-BI selective uptake is a key step in reverse cholesterol transport and is essential for the synthesis of steroid hormones.