Extracellular hydrophobic regions in scavenger receptor BI play a key role in mediating HDL-cholesterol transport

Papale, Gabriella; Nicholson, Kay; Hanson, P. J.; Pavlovic, Mitja; Drover, Victor A.; Sahoo, Daisy

doi:10.1016/j.abb.2010.02.011

Cited by 32 publications

(56 citation statements)

References 62 publications

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“…The importance of extracellular domain of SR-BI in cholesteryl ester uptake has been explored by the use of chimeric receptors ( 28 ), by insertion of epitope tags into various regions of the domain of SR-BI ( 29 ), by blocking antibody against the extracellular domain, and by mutations ( 30,31 ). However, the HDL binding site and the factors that regulate SR-BI-mediated cholesteryl ester uptake remain to be identifi ed.…”

Section: Discussionmentioning

confidence: 99%

C323 of SR-BI is required for SR-BI-mediated HDL binding and cholesteryl ester uptake

Guo

Chen

Song

et al. 2011

Journal of Lipid Research

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This article is available online at http://www.jlr.org from HDL into hepatocytes and subsequently secretes cholesterol from bile. SR-BI-mediated cholesteryl ester uptake is also required for steroidogenesis, in which SR-BI uptakes cholesteryl ester from HDL into endocrine tissues for steroid synthesis ( 3-7 ). The importance of SR-BI-mediated cholesterol transport has been established in mouse models. Mice defi cient in SR-BI have a 2-fold increase in total cholesterol concentration and a 3-fold increase in free cholesterol concentration in circulation, and they develop cardiovascular diseases ( 8-13 ). Mice overexpressing SR-BI have lower plasma cholesterol levels ( 14-17 ) and are protected against the development of atherosclerosis ( 11,18 ). A recent report showed that a family with functional mutation in SR-BI has elevated plasma HDL and changes in cholesterol metabolism in macrophages and platelets, indicating a role of SR-BI in humans ( 19 ). In addition to modulating HDL metabolism, recent studies revealed that SR-BI is a multifunctional protein. It activates eNOS in endothelial cells in the presence of HDL ( 20-23 ), induces apoptosis in the absence of HDL/eNOS ( 24 ), protects against nitric oxide (NO)-induced oxidative damage ( 25 ), and prevents endotoxic and septic animal death ( 25-27 ).SR-BI facilitates intracellular uptake of HDL cholesteryl esters in a two-step process involving binding of HDL through its extracellular domain and transferring cholesteryl ester from HDL into cells. The importance of extracellular domain of SR-BI in cholesteryl ester uptake has been explored by the use of chimeric receptors ( 28 ), by insertion of epitope tags into various regions of the domain of SR-BI ( 29 ), by blocking antibody against the extracellular domain, and by mutations ( 30, 31 ). However, SR-BI has a large extracellular domain that contains 403 amino acid residues, and the HDL binding site remains to be determined. Identifying the HDL binding site and understanding the regulation of SR-BI-mediated cholesterol Abstract Scavenger receptor BI (SR-BI) is an HDL receptor. It binds HDL and mediates the uptake of cholesteryl ester from HDL. Early studies have pointed out that the extracellular domain of SR-BI is critical for SR-BI-mediated cholesteryl ester uptake. However, the extracellular loop of SR-BI is large: it contains 403 amino acids. The HDL binding site and the modulation of SR-BI-mediated cholesteryl ester uptake remain to be identifi ed. In this study, using C323G mutant SR-BI, we showed that C323G mutant SR-BI lost its HDL binding and cholesteryl ester uptake activity, indicating that the highly conserved C323 is required for SR-BI-mediated HDL binding and cholesteryl ester uptake. Using a blocking antibody against C323 region, we demonstrated that C323 is directly involved in HDL binding and likely an HDL binding site. Using C323G mutant transgenic mouse model, we further demonstrated that C323 of SR-BI is required for regulating plasma cholesterol levels in vivo.Using redox reagents, we show...

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Section: Discussionmentioning

confidence: 99%

C323 of SR-BI is required for SR-BI-mediated HDL binding and cholesteryl ester uptake

Guo

Chen

Song

et al. 2011

Journal of Lipid Research

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“…It has been speculated that formation of a productive HDL/SR-BI complex [25] depends on the correct alignment of specific lipoprotein and receptor domains and/or the capacity of the receptor to undergo appropriate conformational changes that permit efficient lipid transport. Several studies [26–29], including our own [5,30–32], have demonstrated the important contributions of specific extracellular regions of SR-BI in mediating the selective uptake of HDL-CE. Indeed, the recent availability of the X-ray crystal structure of the extracellular domain of LIMP-2 [33], a scavenger receptor that shares 30% sequence identity with SR-BI, provides the opportunity to better recognize key structural features of this domain that contribute to its cholesterol transport functions.…”

Section: Introductionmentioning

confidence: 98%

Expression, purification and reconstitution of the C-terminal transmembrane domain of scavenger receptor BI into detergent micelles for NMR analysis

Chadwick

Jensen

Peterson

et al. 2015

Protein Expression and Purification

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Scavenger receptor class B type I (SR-BI), the high density lipoprotein (HDL) receptor, is important for the delivery of HDL-cholesteryl esters to the liver for excretion via bile formation. The focus on therapeutic strategies aimed at reducing cholesterol levels highlights the critical need to understand the structural features of SR-BI that drive cholesterol removal. Yet, in the absence of a high-resolution structure of SR-BI, our understanding of how SR-BI interacts with HDL is limited. In this study, we have optimized the NMR solution conditions for the structural analysis of the C-terminal transmembrane domain of SR-BI that harbors putative domains required for receptor oligomerization. An isotopically-labeled SR-BI peptide encompassing residues 405–475 was bacterially-expressed and purified. [U-15N]-SR-BI(405–475) was incorporated into different detergent micelles and assessed by 1H-15N-HSQC in order to determine which detergent micelle best maintained SR-BI(405–475) in a folded, native conformation for subsequent NMR analyses. We also determined the optimal detergent concentration used in micelles, as well as temperature, solution buffer and pH conditions. Based on 1H-15N-HSQC peak dispersion, intensity, and uniformity, we determined that [U-15N]-SR-BI(405–475) should be incorporated into 5% detergent micelles consisting of 1-palmitoyl-2-hydroxy-sn-glycero-3-phospho-[1’-rac-glycerol] (LPPG) and data collected at 40°C in a non-buffered solution at pH 6.8. Furthermore, we demonstrate the ability of SR-BI(405–475) to form dimers upon chemical crosslinking. These studies represent the first steps in obtaining high-resolution structural information by NMR for the HDL receptor that plays a critical role in regulating whole body cholesterol removal.

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“…6G-J ). Because production of transgenic larvae is not suitable for high-throughput studies, in vitro reconstitution of selective carotenoid uptake by SCRB15 and Cameo2, such as has been achieved for cellular cholesteryl ester uptake by SR-BI (46)(47)(48), is required to examine the selectivity mechanism by point mutagenesis or analysis of chimeric genes of SCRB15 and Cameo2.…”

Section: Discussionmentioning

confidence: 99%

CD36 homolog divergence is responsible for the selectivity of carotenoid species migration to the silk gland of the silkworm Bombyx mori

Sakudoh

Kuwazaki²,

Iizuka

et al. 2013

Journal of Lipid Research

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Extracellular hydrophobic regions in scavenger receptor BI play a key role in mediating HDL-cholesterol transport

Cited by 32 publications

References 62 publications

C323 of SR-BI is required for SR-BI-mediated HDL binding and cholesteryl ester uptake

C323 of SR-BI is required for SR-BI-mediated HDL binding and cholesteryl ester uptake

Expression, purification and reconstitution of the C-terminal transmembrane domain of scavenger receptor BI into detergent micelles for NMR analysis

CD36 homolog divergence is responsible for the selectivity of carotenoid species migration to the silk gland of the silkworm Bombyx mori

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