Interaction of apoA-1 and ApoE-3 with triglyceride-phospholipid emulsions containing increasing cholesterol concentrations. Model of triglyceride-rich nascent and remnant lipoproteins

Derksen, Arie; Small, Donald

doi:10.1021/bi00428a074

Cited by 36 publications

(35 citation statements)

References 33 publications

(34 reference statements)

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“…The binding capacity of full-length apoE4 (around 0.8 amino acid/PC molecule) was comparable with the previous data of human apoE3 binding to emulsion particles (34,35). Assuming that all of the amphipathic ␣-helices in the apoE molecule interact similarly with lipid, the B max values in terms of amino acids/PC molecule of all proteins should be identical.…”

Section: Binding Of Apoe To Emulsionsupporting

confidence: 88%

Lipid Binding-induced Conformational Change in Human Apolipoprotein E

Saito¹,

Dhanasekaran²,

Baldwin³

et al. 2001

Journal of Biological Chemistry

108

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Apolipoprotein (apo) E contains two structural domains, a 22-kDa (amino acids 1-191) N-terminal domain and a 10-kDa (amino acids 223-299) C-terminal domain.To better understand apoE-lipid interactions on lipoprotein surfaces, we determined the thermodynamic parameters for binding of apoE4 and its 22-and 10-kDa fragments to triolein-egg phosphatidylcholine emulsions using a centrifugation assay and titration calorimetry. In both large (120 nm) and small (35 nm) emulsion particles, the binding affinities decreased in the order 10-kDa fragment Ϸ 34-kDa intact apoE4 > 22-kDa fragment, whereas the maximal binding capacity of intact apoE4 was much larger than those of the 22-and 10-kDa fragments. These results suggest that at maximal binding, the binding behavior of intact apoE4 is different from that of each fragment and that the N-terminal domain of intact apoE4 does not contact lipid. Isothermal titration calorimetry measurements showed that apoE binding to emulsions was an exothermic process. Binding to large particles is enthalpically driven, and binding to small particles is entropically driven. At a low surface concentration of protein, the binding enthalpy of intact apoE4 (؊69 kcal/mol) was approximately equal to the sum of the enthalpies for the 22-and 10-kDa fragments, indicating that both the 22-and 10-kDa fragments interact with lipids. In a saturated condition, however, the binding enthalpy of intact apoE4 (؊39 kcal/mol) was less exothermic and rather similar to that of each fragment, supporting the hypothesis that only the C-terminal domain of intact apoE4 binds to lipid. We conclude that the N-terminal four-helix bundle can adopt either open or closed conformations, depending upon the surface concentration of emulsion-bound apoE.

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Section: Binding Of Apoe To Emulsionsupporting

confidence: 88%

Lipid Binding-induced Conformational Change in Human Apolipoprotein E

Saito¹,

Dhanasekaran²,

Baldwin³

et al. 2001

Journal of Biological Chemistry

108

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“…In the case of the full-length proteins, apoE2 and apoE3 displayed much lower binding affinity for both emulsions compared with apoE4, whereas the binding capacities of the three isoforms were similar for both emulsion particle sizes. The binding parameters for full-length apoE3 were comparable to the previously reported data for human apoE3 (34,35), and the higher affinity of apoE4 compared with apoE3 was also observed for VLDL-size emulsion particles (16,36). In contrast to the 22-kDa fragment of apoE4, the 22-kDa fragments of apoE2 and apoE3 displayed negligible binding capacities for both emulsions.…”

Section: Binding Of Apoe Isoforms To Emulsion Particles-previouslysupporting

confidence: 87%

Effects of Polymorphism on the Lipid Interaction of Human Apolipoprotein E

Saito

Dhanasekaran

Baldwin

et al. 2003

Journal of Biological Chemistry

111

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ApoE exists as three common isoforms, apoE2, apoE3, and apoE4; apoE2 and apoE3 preferentially bind to high density lipoproteins, whereas apoE4 prefers very low density lipoproteins (VLDL). To understand the molecular basis for the different lipoprotein distributions of these isoforms in human plasma, we examined the lipid-binding properties of the apoE isoforms and some mutants using lipid emulsions. With both large (120 nm) and small (35 nm) emulsion particles, the binding affinity of apoE4 was much higher than that of apoE2 and apoE3, whereas the maximal binding capacities were similar among the three isoforms. The 22-kDa N-terminal fragment of apoE4 displayed a much higher binding capacity than did apoE2 and apoE3. The apoE4(E255A) mutant, which has no electrostatic interaction between Arg 61 and Glu 255, showed binding behavior similar to that of apoE3, indicating that N-and C-terminal domain interaction in apoE4 is responsible for its high affinity for lipid. In addition, the apoE3(P267A) mutant, which is postulated to contain a long ␣-helix in the Cterminal domain, had significantly decreased binding capacities for both sizes of emulsion particle, suggesting that the apoE4 preference for VLDL is not due to a stabilized long ␣-helical structure. Isothermal titration calorimetry measurements showed that there is no significant difference in thermodynamic parameters for emulsion binding among the apoE isoforms. However, fluorescence measurements of 8-anilino-1-naphthalenesulfonic acid binding to apoE indicated that apoE4 has more exposed hydrophobic surface compared with apoE3 mainly due to the different tertiary organization of the C-terminal domain. The less organized structure in the C-terminal domain of apoE4 leads to the higher affinity for lipid, contributing to its preferential association with VLDL. In fact, we found that apoE4 binds to VLDL with higher affinity compared with apoE3.

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“…VLDL-like emulsion particles prepared from triolein and phosphatidylcholine (PC) were utilized as a model for TG-rich lipoproteins (21, 22). To better understand how the mutations introduced in apoE4-mut1and apoE4-mut2 alter the function of apoE4, we investigated the conformation and stability of the apoE4 variants.…”

mentioning

confidence: 99%

Biophysical Properties of Apolipoprotein E4 Variants: Implications in Molecular Mechanisms of Correction of Hypertriglyceridemia

et al. 2008

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In humans and animal models, high plasma concentrations of apolipoprotein (apo) E are associated with hypertriglyceridemia. It has been shown that overexpression of human wild-type (WT) apoE4 in apoE-deficient mice induces hypertriglyceridemia. In contrast, overexpression of an apoE4 variant, apoE4-mut1 (apoE4(L261A, W264A, F265A, L268A, V269A)), does not induce hypertriglyceridemia and corrects hypercholesterolemia. Furthermore, overexpression of another variant, apoE4-mut2 (apoE4(W276A, L279A, V280A, V283A)), induces mild hypertriglyceridemia and does not correct hypercholesterolemia. To better understand how these mutations improve the function of apoE4, we investigated the conformation and stability of apoE4-mut1 and apoE4-mut2 and their binding to dimyristoyl phosphatidylcholine (DMPC) vesicles and to triglyceride (TG)-rich emulsion particles. We found that the mutations introduced in apoE4-mut1 lead to a more stable and compactly folded conformation of apoE4. These structural changes are associated with a slower rate of solubilization of DMPC vesicles by apoE4-mut1 and reduced binding of the protein to emulsion particles as compared to WT apoE4. Under conditions of apoE4 overexpression, the reduced binding of apoE4-mut1 to TG-rich lipoprotein particles may facilitate the lipolysis of these particles and may alter the conformation of the lipoprotein-bound apoE in a way that favors the efficient clearance of the lipoprotein remnants. Mutations introduced in apoE4-mut2 result in smaller structural alterations compared to those observed in apoE4-mut1. The slightly altered structural properties of apoE4-mut2 are associated with slightly reduced binding of this protein to TG-rich lipoprotein particles and milder hypertriglyceridemia as compared to WT apoE4.Human apolipoprotein E (apoE) is a key component of the lipoprotein transport system and is required for the maintenance of lipid homeostasis in the circulation and the brain (1-3). In humans, there are three natural apoE isoforms that differ from each other by amino acid substitutions at positions 112 and 158. ApoE3 is the most common isoform; apoE2 is associated with type III hyperlipoproteinemia, while apoE4 (Arg-112, Arg-158) is associated with high plasma cholesterol level and an increased risk for both coronary heart disease and Alzheimer's diseases (4-7). ApoE is one of the major protein constituents of triglyceride (TG)-rich chylomicrons and very low density lipoproteins NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript (VLDL). In the bloodstream, these TGrich lipoproteins are converted into remnants through hydrolysis of their core TG by lipoprotein lipase (LPL). At physiological concentrations, apoE mediates the hepatic uptake of the lipoprotein remnants via the low density lipoprotein (LDL) receptor and thereby, regulates plasma lipid levels and contributes to atheroprotection (1-3, 7). However, elevated plasma apoE levels in humans and in animal models have been positively correlated with hypertriglyceridemia (8-1...

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Interaction of apoA-1 and ApoE-3 with triglyceride-phospholipid emulsions containing increasing cholesterol concentrations. Model of triglyceride-rich nascent and remnant lipoproteins

Cited by 36 publications

References 33 publications

Lipid Binding-induced Conformational Change in Human Apolipoprotein E

Lipid Binding-induced Conformational Change in Human Apolipoprotein E

Effects of Polymorphism on the Lipid Interaction of Human Apolipoprotein E

Biophysical Properties of Apolipoprotein E4 Variants: Implications in Molecular Mechanisms of Correction of Hypertriglyceridemia

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