The Effects of Mutations in Helices 4 and 6 of ApoA-I on Scavenger Receptor Class B Type I (SR-BI)-mediated Cholesterol Efflux Suggest That Formation of a Productive Complex between Reconstituted High Density Lipoprotein and SR-BI Is Required for Efficient Lipid Transport

Liu, Tong; Krieger, Monty; Kan, Horng-Yuan; Zannis, Vassilis I.

doi:10.1074/jbc.m112103200

Cited by 98 publications

(131 citation statements)

References 61 publications

Supporting

Mentioning

120

Contrasting

Unclassified

Order By: Relevance

“…The mechanistic coupling of HDL binding and lipid transport observed here is consistent with the productive binding model for SR-BI interaction with HDL (29). A number of studies have explored the influence of the protein composition of HDL particles on binding and lipid transfer (26,29,(31)(32)(33).…”

Section: Discussionsupporting

confidence: 60%

“…BLTs and other inhibitors or activators of SR-BI should be useful for the analysis of the molecular and cellular mechanisms of SR-BI activity and the study of the physiologic functions of SR-BI by its pharmacologic manipulation in vivo. Our studies with the BLTs support a two-step mechanism of SR-BI activity, productive binding followed by lipid transfer (19,29), and suggest that these two steps may be mechanistically linked because they result in coordinated decreases in lipid transfer and increases in binding affinity. They also suggest that there may be differences in the mechanisms of SR-BI-mediated lipid uptake and cholesterol efflux (20,30), because the IC 50 values for uptake and efflux for each of three BLTs (BLT-3-BLT-5) differed.…”

Section: Discussionmentioning

confidence: 88%

“…A number of studies have explored the influence of the protein composition of HDL particles on binding and lipid transfer (26,29,(31)(32)(33). They showed that variations in the structure͞composition of HDL particles could affect the efficiency of selective uptake or efflux relative to lipoprotein binding and thus support the concept of productive binding.…”

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Discovery of chemical inhibitors of the selective transfer of lipids mediated by the HDL receptor SR-BI

Nieland

Penman

Dori

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

190

232

View full text Add to dashboard Cite

The high-density lipoprotein (HDL) receptor, scavenger receptor, class B, type I (SR-BI), mediates both the selective uptake of lipids, mainly cholesterol esters, from HDL to cells and the efflux of cholesterol from cells to lipoproteins. The mechanism underlying these lipid transfers is distinct from classic receptor-mediated endocytosis, but it remains poorly understood. To investigate SR-BI's mechanism of action and in vivo function, we developed a high-throughput screen to identify small molecule inhibitors of SR-BI-mediated lipid transfer in intact cells. We identified five compounds that in the low nanomolar to micromolar range block lipid transport (BLTs), both selective uptake and efflux. The effects of these compounds were highly specific to the SR-BI pathway, because they didn't interfere with receptor-mediated endocytosis or with other forms of intracellular vesicular traffic. Surprisingly, all five BLTs enhanced, rather than inhibited, HDL binding by increasing SR-BI's binding affinity for HDL (decreased dissociation rates). Thus, the BLTs provide strong evidence for a mechanistic coupling between HDL binding and lipid transport and may serve as a starting point for the development of pharmacologically useful modifiers of SR-BI activity and, thus, HDL metabolism.

show abstract

Section: Discussionsupporting

confidence: 60%

Section: Discussionmentioning

confidence: 88%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Discovery of chemical inhibitors of the selective transfer of lipids mediated by the HDL receptor SR-BI

Nieland

Penman

Dori

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

190

232

View full text Add to dashboard Cite

show abstract

“…Numerous studies indicate that SR-BI-mediated selective lipid uptake is a two-step process involving productive binding of HDL (1, 6, 7) followed by bindingdependent lipid transfer. In addition to mediating selective lipid uptake, SR-BI can mediate cholesterol efflux from cells to HDL (8) via a binding-dependent process (6,7,9) (however see Ref. 10 for alternative view).…”

mentioning

confidence: 99%

Identification of the N-Linked Glycosylation Sites on the High Density Lipoprotein (HDL) Receptor SR-BI and Assessment of Their Effects on HDL Binding and Selective Lipid Uptake

Viñals¹,

Vasile

et al. 2003

Journal of Biological Chemistry

Self Cite

View full text Add to dashboard Cite

The murine class B, type I scavenger receptor mSR-BI, a high density lipoprotein (HDL) receptor that mediates selective uptake of HDL lipids, contains 11 potential N-linked glycosylation sites and unknown numbers of both endoglycosidase H-sensitive and -resistant oligosaccharides. We have examined the consequences of mutating each of these sites (Asn 3 Gln or Thr 3 Ala) on post-translational processing of mSR-BI, cell surface expression, and HDL binding and lipid transport activities. All 11 sites were glycosylated; however, disruption of only two (Asn-108 and Asn-173) substantially altered expression and function. There was very little detectable post-translational processing of these two mutants to endoglycosidase H resistance and very low cell surface expression, suggesting that oligosaccharide modification at these sites apparently plays an important role in endoplasmic reticulum folding and/or intracellular transport. Strikingly, although the low levels of the 108 and 173 mutants that were expressed on the cell surface exhibited a marked reduction in their ability to transfer lipids from HDL to cells, they nevertheless bound nearly normal amounts of HDL. Indeed, the affinity of 125 I-HDL binding to the 173 mutant was similar to that of the wild-type receptor. Thus, N-linked glycosylation can influence both the intracellular transport and lipid-transporter activity of SR-BI. The ability to uncouple the HDL binding and lipid transport activities of mSR-BI by in vitro mutagenesis should provide a powerful tool for further analysis of the mechanism of SR-BI-mediated selective lipid uptake. Scavenger receptor class B, type I, SR-BI,1 is a 509-residue, ϳ82-kDa integral membrane cell surface glycoprotein of the CD36 superfamily that was the first high density lipoprotein (HDL) receptor to be characterized in detail (1, 2). SR-BI helps control the structure and metabolism of HDL by mediating the transport of lipids from HDL to cells. The mechanism by which SR-BI mediates this lipid transport differs from the classic LDL receptor pathway of endocytosis, in which the entire lipoprotein is internalized via coated pits and subsequently hydrolyzed by lysosomal enzymes (3). Instead, HDL binds to SR-BI, lipids of HDL (primarily neutral lipids such as cholesteryl esters in the core of the particle) are transported into the cells, and the lipid-depleted particle is released into the extracellular space (1, 2, 4, 5). This mechanism is called selective lipid uptake (2, 4, 5). Numerous studies indicate that SR-BI-mediated selective lipid uptake is a two-step process involving productive binding of HDL (1, 6, 7) followed by bindingdependent lipid transfer. In addition to mediating selective lipid uptake, SR-BI can mediate cholesterol efflux from cells to HDL (8) via a binding-dependent process (6, 7, 9) (however see In vivo analyses of the function of SR-BI, primarily using SR-BI homozygous null mice (11, 12) and murine hepatic overexpression of SR-BI transgenes (13-18), have shown that SR-BI can profoundly influence several ph...

show abstract

“…Materials not mentioned in the Experimental Procedures have been obtained from sources described previously (23,24).…”

Section: Experimental Procedures Materialsmentioning

confidence: 99%

Residues Leu261, Trp264, and Phe265 Account for Apolipoprotein E-Induced Dyslipidemia and Affect the Formation of Apolipoprotein E-Containing High-Density Lipoprotein

2007

Self Cite

View full text Add to dashboard Cite

Overexpression of apolipoprotein E (apoE) induces hypertriglyceridemia in apoE-deficient mice, which is abrogated by deletion of the carboxy-terminal segment of residues 260-299. We have used adenovirus-mediated gene transfer in apoE −/− and apoA-I −/− mice to test the effect of three sets of apoE mutations within the region of residues 261-265 on the induction of hypertriglyceridemia, the esterification of cholesterol of very low-density lipoprotein (VLDL) and high-density lipoprotein (HDL), and the formation of spherical or discoidal apoE-containing HDL. A single-amino acid substitution (apoE4-[Phe265Ala]) induced hypertriglyceridemia in apoE −/− or apoA-I −/− mice, promoted the accumulation of free cholesterol in the very low-density lipoprotein (VLDL) and HDL region, and decreased HDL cholesterol levels. A double substitution (apoE4[Leu261Ala/ Trp264Ala]) induced milder hypertriglyceridemia and increased HDL cholesterol levels. A triple substitution (apoE4-[Leu261Ala/Trp264Ala/Phe265Ala] or apoE2-[Leu261Ala/Trp264Ala/ Phe265Ala]) did not induce hypertriglyceridemia and increased greatly the HDL cholesterol levels. Electron microscopy (EM) analysis of the HDL fractions showed that apoE4-[Leu261Ala/ Trp264Ala/Phe265Ala] and apoE2-[Leu261Ala/Trp264Ala/Phe265Ala] contained spherical HDL, apoE4-[Leu261Ala/Trp264Ala] contained mostly spherical and few discoidal HDL particles, and apoE4-[Phe265Ala] contained discoidal HDL. We conclude that residues Leu261, Trp264, and Phe265 play an important role in apoE-induced hypertriglyceridemia, the accumulation of free cholesterol in VLDL and HDL, and the formation of discoidal HDL. Substitution of these residues with Ala improves the apoE functions by preventing hypertriglyceridemia and promoting formation of spherical apoE-containing HDL.ApoE 1 is a very important protein of the lipoprotein transport system that plays an important role in the protection from or the pathogenesis of atherosclerosis, dyslipidemia, and Alzheimer's disease (1-5).

show abstract

The Effects of Mutations in Helices 4 and 6 of ApoA-I on Scavenger Receptor Class B Type I (SR-BI)-mediated Cholesterol Efflux Suggest That Formation of a Productive Complex between Reconstituted High Density Lipoprotein and SR-BI Is Required for Efficient Lipid Transport

Cited by 98 publications

References 61 publications

Discovery of chemical inhibitors of the selective transfer of lipids mediated by the HDL receptor SR-BI

Discovery of chemical inhibitors of the selective transfer of lipids mediated by the HDL receptor SR-BI

Identification of the N-Linked Glycosylation Sites on the High Density Lipoprotein (HDL) Receptor SR-BI and Assessment of Their Effects on HDL Binding and Selective Lipid Uptake

Residues Leu261, Trp264, and Phe265 Account for Apolipoprotein E-Induced Dyslipidemia and Affect the Formation of Apolipoprotein E-Containing High-Density Lipoprotein

Contact Info

Product

Resources

About