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Identification of scavenger receptor SR-BI as a high density lipoprotein receptor
S Acton1, A Rigotti, K T Landschulz
1Department of Biology, Massachusetts Institute of Technology, Cambridge 02139, USA.
Insights
The scavenger receptor SR-BI acts as a high-density lipoprotein (HDL) receptor, facilitating selective cholesterol uptake in the liver and steroidogenic tissues. This finding clarifies a key mechanism in HDL cholesterol transport.
Area of Science:
- Biochemistry
- Molecular Biology
- Cardiovascular Research
Background:
- High-density lipoprotein (HDL) and low-density lipoprotein (LDL) are key cholesterol carriers linked to atherosclerosis risk.
- LDL uptake is understood, but HDL's selective cholesterol delivery mechanism and receptors remain unclear.
Purpose of the Study:
- To identify the receptor responsible for high-density lipoprotein (HDL) selective cholesterol uptake.
- To elucidate the mechanism of HDL cholesterol transport distinct from the LDL pathway.
Main Methods:
- Characterization of the class B scavenger receptor SR-BI.
- Assessing SR-BI's binding affinity for HDL.
- Evaluating SR-BI expression in key tissues (liver, steroidogenic tissues).
- Investigating cholesterol uptake mediated by SR-BI.
Main Results:
- The class B scavenger receptor SR-BI binds HDL with high affinity.
- SR-BI is predominantly expressed in the liver and nonplacental steroidogenic tissues.
- SR-BI mediates selective cholesterol uptake from HDL, independent of the LDL receptor pathway.
Conclusions:
- The scavenger receptor SR-BI functions as a high-density lipoprotein (HDL) receptor.
- SR-BI plays a crucial role in selective cholesterol uptake, particularly in the liver.
- This discovery provides a molecular basis for understanding HDL's role in cholesterol homeostasis and reverse cholesterol transport.
Abstract:
High density lipoprotein (HDL) and low density lipoprotein (LDL) are cholesterol transport particles whose plasma concentrations are directly (LDL) and inversely (HDL) correlated with risk for atherosclerosis. LDL catabolism involves cellular uptake and degradation of the entire particle by a well-characterized receptor. HDL, in contrast, selectively delivers its cholesterol, but not protein, to cells by unknown receptors. Here it is shown that the class B scavenger receptor SR-BI is an HDL receptor. SR-BI binds HDL with high affinity, is expressed primarily in liver and nonplacental steroidogenic tissues, and mediates selective cholesterol uptake by a mechanism distinct from the classic LDL receptor pathway.