SR-BI/CD36 chimeric receptors define extracellular subdomains of SR-BI critical for cholesterol transport.

Abstract

High-density lipoproteins (HDLs) are athero-protective, primarily because of their ability to promote cholesterol flux from peripheral tissues to the liver by reverse cholesterol transport (RCT). The delivery of HDL-cholesteryl esters (CE) into cells is mediated by the HDL receptor, scavenger receptor class B type I (SR-BI), a promising target for enhancing whole body cholesterol disposal and preventing cardiovascular disease. A detailed understanding of the structural determinants underlying proper SR-BI/HDL alignment that supports the selective uptake of HDL-CE into cells remains lacking. To this end, we exploited CD36, a class B scavenger receptor with a predicted topology similar to that of SR-BI that binds HDL but is unable to mediate efficient selective uptake of HDL-CE. We generated a series of SR-BI/CD36 chimeric receptors that span the extracellular (EC) domain of SR-BI to delineate regions that are essential for SR-BI's cholesterol transport functions. All 16 SR-BI/CD36 chimeras were transiently expressed in COS-7 cells, and their plasma membrane localization was confirmed. The majority of SR-BI/CD36 chimeric receptors displayed significant reductions in their ability to (i) bind HDL, (ii) deliver HDL-CE to cells, (iii) mediate efflux of free cholesterol (FC) to HDL, and (iv) redistribute plasma membrane domains of FC. We also demonstrated that changes in SR-BI function were independent of receptor oligomerization. Altogether, we have identified discrete subdomains, particularly in the N-terminal and C-terminal regions of the EC domain of SR-BI, that are critical for productive receptor-ligand interactions and the various cholesterol transport functions of SR-BI.

• Authors: Gabriella A Kartz, Rebecca L Holme, Kay Nicholson, Daisy Sahoo
• Journal: Biochemistry (Biochemistry) Vol. 53 Issue 39 Pg. 6173-82 (Oct 07 2014) ISSN: 1520-4995 [Electronic] United States
• PMID: 25211142 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• CD36 Antigens
• Lipoproteins, HDL
• Recombinant Fusion Proteins
• Cholesterol

Topics

• Amino Acid Sequence
• Animals
• Binding Sites
• Biological Transport (genetics)
• CD36 Antigens (chemistry, genetics, metabolism)
• COS Cells
• Chlorocebus aethiops
• Cholesterol (chemistry, metabolism)
• Electrophoresis, Polyacrylamide Gel
• Lipoproteins, HDL (chemistry, metabolism)
• Mice
• Molecular Sequence Data
• Protein Multimerization
• Protein Structure, Tertiary
• Rats
• Recombinant Fusion Proteins (chemistry, genetics, metabolism)
• Sequence Homology, Amino Acid