Medical College of Wisconsin
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Extracellular disulfide bonds support scavenger receptor class B type I-mediated cholesterol transport. Biochemistry 2011 Jul 19;50(28):6245-54

Date

06/17/2011

Pubmed ID

21675794

Pubmed Central ID

PMC3940413

DOI

10.1021/bi2005625

Scopus ID

2-s2.0-79960208673 (requires institutional sign-in at Scopus site)   27 Citations

Abstract

Scavenger receptor class B type I (SR-BI) binds high-density lipoprotein (HDL) and mediates the selective uptake of cholesteryl esters (CE). Although the extracellular domain of SR-BI is critical for function, the structural characteristics of this region remain elusive. Using sulfhydryl labeling strategies, we report the novel finding that all six cysteine (Cys) residues in the extracellular domain of SR-BI are involved in disulfide bond formation that is intramolecular by nature. We hypothesized that an SR-BI conformation stabilized by extracellular disulfide bonds is a prerequisite for SR-BI-mediated cholesterol transport. Thus, single-Cys mutant SR-BI receptors (C251S-, C280S-, C321S-, C323S-, C334S-, and C384S-SR-BI), as well as Cys-less SR-BI, a mutant SR-BI receptor void of all Cys residues, were created, and plasma membrane localization was confirmed. Functional assays revealed that C280S-, C321S-, C323S-, and C334S-SR-BI and Cys-less SR-BI mutant receptors displayed weakened HDL binding and subsequent selective uptake of HDL-CE. However, only C323S-SR-BI and Cys-less SR-BI were unable to mediate wild-type levels of efflux of free cholesterol (FC) to HDL. None of the Cys mutations disrupted SR-BI's ability to redistribute plasma membrane FC. Taken together, the intramolecular disulfide bonds in the extracellular domain of SR-BI appear to maintain the receptor in a conformation integral to its cholesterol transport functions.

Author List

Papale GA, Hanson PJ, Sahoo D

Author

Daisy Sahoo PhD Dean, Professor in the Medicine department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Animals
Biological Transport
CD36 Antigens
COS Cells
Cholesterol
Cholesterol, HDL
Disulfides
Endocytosis
Extracellular Fluid
Hydrolysis
Mice
Protein Binding
Protein Conformation