Cholesterol Determines and Limits rHDL Formation from Human Plasma Apolipoprotein A-II and Phospholipid Membranes

Bassett, G. Randall; Gillard, Baiba K.; Pownall, Henry J.

doi:10.1021/bi3011994

Cited by 8 publications

(16 citation statements)

References 31 publications

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“…This feature is mainly determined by the type, proportion, and interaction between lipid and protein cargo [119]. Many of the early structural studies on rHDL/sHDL employed particles reconstituted with dimyristoylphosphatidylcholine (DMPC, a shorter saturated acyl chain PL, 14:0), due to its ability to spontaneously form rHDL/sHDL particles when DMPC vesicles were mixed with apoA-I [120][121][122][123][124][125]. Later, the cholate dialysis method [126] was reported to allow reconstitution of rHDL/sHDL with physiologically relevant phospholipids that have longer and unsaturated acyl chains like palmitoyloleoylphosphatidylcoline (POPC, 16:0-18:1).…”

Section: Hdl-mimetics: Composition and Characteristicsmentioning

confidence: 99%

Advances in HDL: Much More than Lipid Transporters

Ben‐Aicha

Badimon

Vilahur

2020

IJMS

101

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High Density Lipoprotein (HDL) particles, beyond serving as lipid transporters and playing a key role in reverse cholesterol transport, carry a highly variable number of proteins, micro-RNAs, vitamins, and hormones, which endow them with the ability to mediate a plethora of cellular and molecular mechanisms that promote cardiovascular health. It is becoming increasingly evident, however, that the presence of cardiovascular risk factors and co-morbidities alters HDLs cargo and protective functions. This concept has led to the notion that metrics other than HDL-cholesterol levels, such as HDL functionality and composition, may better capture HDL cardiovascular protection. On the other hand, the potential of HDL as natural delivery carriers has also fostered the design of engineered HDL-mimetics aiming to improve HDL efficacy or as drug-delivery agents with therapeutic potential. In this paper, we first provide an overview of the molecules known to be transported by HDL particles and mainly discuss their functions in the cardiovascular system. Second, we describe the impact of cardiovascular risk factors and co-morbidities on HDL remodeling. Finally, we review the currently developed HDL-based approaches.

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Section: Hdl-mimetics: Composition and Characteristicsmentioning

confidence: 99%

Advances in HDL: Much More than Lipid Transporters

Ben‐Aicha

Badimon

Vilahur

2020

IJMS

101

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“…The dried lipids were dispersed into TBS by vortexing above 24 C after which the lipids were subjected to three cycles of warming to 50 C with vortexing and freezing to À20 C. rHDL were prepared by incubating DMPC MLV containing 15 mol % FC over night at the transition temperature of the DMPC, 24 C, with a DMPC/apo AI ratio of 10 (w/w). Unbound DMPC was sedimented at 16,000 Â g for 30 min in an Eppendorf 5415C centrifuge (Thermo-Fischer, Waltham, MA) at 4 C. The rHDL in the supernatant were separated into various rHDL by size exclusion chromatography (SEC) over tandem columns of Superose HR6 (GE Healthcare, Pittsburgh, PA) and fractions collected (9,19). The peak fraction for the largest rHDL (1 mL) was collected and analyzed by analytical SEC to ensure purity and document homogeneity.…”

Section: Introductionmentioning

confidence: 99%

Direct Measurement of the Structure of Reconstituted High-Density Lipoproteins by Cryo-EM

Murray

Gillard

Ludtke

et al. 2016

Biophysical Journal

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Early forms of high-density lipoproteins (HDL), nascent HDL, are formed by the interaction of apolipoprotein AI with macrophage and hepatic ATP-binding cassette transporter member 1. Various plasma activities convert nascent to mature HDL, comprising phosphatidylcholine (PC) and cholesterol, which are selectively removed by hepatic receptors. This process is important in reducing the cholesterol burden of arterial wall macrophages, an important cell type in all stages of atherosclerosis. Interaction of apolipoprotein AI with dimyristoyl (DM)PC forms reconstituted (r)HDL, which is a good model of nascent HDL. rHDL have been used as an antiathersclerosis therapy that enhances reverse cholesterol transport in humans and animal models. Thus, identification of the structure of rHDL would inform about that of nascent HDL and how rHDL improves reverse cholesterol transport in an atheroprotective way. Early studies of rHDL suggested a discoidal structure, which included pairs of antiparallel helices of apolipoprotein AI circumscribing a phospholipid bilayer. Another rHDL model based on small angle neutron scattering supported a double superhelical structure. Herein, we report a cryo-electron microscopy-based model of a large rHDL formed spontaneously from apolipoprotein AI, cholesterol, and excess DMPC and isolated to near homogeneity. After reconstruction we obtained an rHDL structure comprising DMPC, cholesterol, and apolipoprotein AI (423:74:1 mol/mol) forming a discoidal particle 360 Å in diameter and 45 Å thick; these dimensions are consistent with the stoichiometry of the particles. Given that cryo-electron microscopy directly observes projections of individual rHDL particles in different orientations, we can unambiguously state that rHDL particles are protein bounded discoidal bilayers.

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“…(28) Others, like us, have observed that the DMPC (0 mol% FC) T m for rHDL (apo A-I) is lower than that of pure DMPC and that the thermal unfolding of apo A-II within rHDL occurs at a lower temperature than that of apo A-I. (29, 30) Moreover, increasing the FC content increases particle size(12, 13, 31) and the negative charge on apo A-I while reducing the free energy of apo A-I α-helix stabilization. (31)…”

Section: Discussionmentioning

confidence: 92%

“…The particle sizes do not increase continuously with increasing mol% FC but rather appear to be quantized so that they occur as discrete species. This has been attributed to an increase in domain size with the addition of FC so that additional apos are needed to fully circumscribe the domain(12, 13) and form a disc.…”

Section: Discussionmentioning

confidence: 99%

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Free Cholesterol Determines Reassembled High-Density Lipoprotein Phospholipid Phase Structure and Stability

Auton

Bassett

Gillard³

et al. 2013

Biochemistry

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Reassembled high density lipoproteins (rHDL) of various sizes and compositions containing apo A-I or apo A-II as their sole protein, dimyristoyl phosphatidylcholine (DMPC), and various amounts of free cholesterol (FC) have been isolated and analyzed by differential scanning calorimetry (DSC) and by circular dichroism to determine their stability and the temperature dependence of their helical content. Our data show that the multiple rHDL species obtained at each mol% FC usually do not have the same mole% FC as the starting mixture and that the size of the multiple species increases in a quantized way with their respective mol% FC. DSC studies reveal multiple phases or domains that can be classified as virtual DMPC, which contains a small amount of DMPC that slightly reduces the melting temperature Tm, a boundary phase that is adjacent to the apo A-I or apo A-II that circumscribes the discoidal rHDL, and a mixed FC + DMPC phase that has a Tm that increases with mol% FC. Only the large rHDL contain virtual DMPC whereas all contain boundary phase and various amounts of mixed FC + DMPC according to increasing size and mol% FC. As reported by others, FC stabilizes the rHDL. For rHDL (apo A-II) compared to rHDL (apo A-I), this occurs in spite of the reduced number of helical regions that mediate binding to the DMPC surface. This effect is attributed to the very high lipophilicity of apo A-II and the reduction in the polarity of the interface between DMPC and the aqueous phase with increasing mol% FC, an effect that is expected to increase the hydrophobic associations with the non polar face of the amphipathic helices of apo A-II. These data are relevant to the differential effects of FC and apolipoprotein species on intracellular and plasma membrane nascent HDL assembly and subsequent remodeling by plasma proteins.

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Cholesterol Determines and Limits rHDL Formation from Human Plasma Apolipoprotein A-II and Phospholipid Membranes

Cited by 8 publications

References 31 publications

Advances in HDL: Much More than Lipid Transporters

Advances in HDL: Much More than Lipid Transporters

Direct Measurement of the Structure of Reconstituted High-Density Lipoproteins by Cryo-EM

Free Cholesterol Determines Reassembled High-Density Lipoprotein Phospholipid Phase Structure and Stability

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