N-terminal mutation of apoA-I and interaction with ABCA1 reveal mechanisms of nascent HDL biogenesis

Liu, Minjing; Mei, Xiaohu; Herscovitz, Haya; Atkinson, David

doi:10.1194/jlr.m084376

Cited by 23 publications

(27 citation statements)

References 56 publications

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“…This model has been supported by electron paramagnetic resonance evidence showing a structural change in the C-terminal domain upon lipid binding [25], which may drive subsequent unfolding of the helical bundle. Atkinson and colleagues x-ray crystal and apoA1 site directed mutagenesis data support the model that N-terminal helical bundle unfolding is required for lipidation [6,26]. Our current findings extend the evidence for this model by showing that locking the helical bundle with a disulfide bond inhibits apoA1 lipidation, and that W8 plays a central role in coordinating one end of the helical bundle.…”

Section: Discussionsupporting

confidence: 83%

“…Another helical bundle destabilizing isoform (L38G, K40G), in the context of full length apoA1, was also shown to unzip the helical bundle from the opposite end of W8, exposing more hydrophobic surface and leading to faster cellular ABCA1 mediated HDL formation [26]. However, whether this bundle destabilizing isoform could rescue the activity of C-terminal deletion was not determined [26].…”

Section: Discussionmentioning

confidence: 99%

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First eight residues of apolipoprotein A-I mediate the C-terminus control of helical bundle unfolding and its lipidation

et al. 2020

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The crystal structure of a C-terminal deletion of apolipoprotein A-I (apoA1) shows a large helical bundle structure in the amino half of the protein, from residues 8 to 115. Using site directed mutagenesis, guanidine or thermal denaturation, cell free liposome clearance, and cellular ABCA1-mediated cholesterol efflux assays, we demonstrate that apoA1 lipidation can occur when the thermodynamic barrier to this bundle unfolding is lowered. The absence of the C-terminus renders the bundle harder to unfold resulting in loss of apoA1 lipidation that can be reversed by point mutations, such as Trp8Ala, and by truncations as short as 8 residues in the amino terminus, both of which facilitate helical bundle unfolding. Locking the bundle via a disulfide bond leads to loss of apoA1 lipidation. We propose a model in which the C-terminus acts on the N-terminus to destabilize this helical bundle. Upon lipid binding to the C-terminus, Trp8 is displaced from its interaction with Phe57, Arg61, Leu64, Val67, Phe71, and Trp72 to destabilize the bundle. However, when the C-terminus is deleted, Trp8 cannot be displaced, the bundle cannot unfold, and apoA1 cannot be lipidated.

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Section: Discussionsupporting

confidence: 83%

Section: Discussionmentioning

confidence: 99%

First eight residues of apolipoprotein A-I mediate the C-terminus control of helical bundle unfolding and its lipidation

et al. 2020

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show abstract

“…This model has been supported by electron paramagnetic resonance evidence showing a structural change in the C-terminal domain upon lipid binding (21), which may drive subsequent unfolding of the helical bundle. Atkinson and colleagues x-ray crystal and apoA1 site directed mutagenesis data support the model that N-terminal helical bundle unfolding is required for lipidation (6,22). Our current findings extend the evidence for this model by showing that locking the helical bundle with a disulfide bond inhibits apoA1 lipidation, and that W8 plays a central role in coordinating one end of the helical bundle.…”

Section: Discussionsupporting

confidence: 83%

“…Another helical bundle destabilizing isoform (L38G, K40G), in the context of full length apoA1, was also shown to unzip the helical bundle from the opposite end of W8, exposing more hydrophobic surface and leading to faster cellular ABCA1 mediated HDL formation (22). However, whether this bundle destabilizing isoform could rescue the activity of C-terminal deletion was not determined (22).…”

Section: Discussionmentioning

confidence: 99%

First eight residues of apolipoprotein A-I mediate the C-terminus control of helical bundle unfolding and its lipidation

Brubaker

Lorkowski

Gulshan

et al. 2019

Preprint

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The crystal structure of a C-terminal deletion of apolipoprotein A-I (apoA1) shows a large helical bundle structure in the amino half of the protein, from residues 8 to 115. Using site directed mutagenesis, guanidine or thermal denaturation, cell free liposome clearance, and cellular ABCA1-mediated cholesterol efflux assays, we demonstrate that apoA1 lipidation can occur when the barrier to this bundle unfolding is lowered. The absence of the C-terminus renders the bundle harder to unfold resulting in loss of apoA1 lipidation that can be reversed by point mutations, such as Trp8Ala, and by truncations as short as 8 residues in the amino terminus, both of which lower the barrier to helical bundle unfolding. Locking the bundle via a disulfide bond leads to loss of apoA1 lipidation. We propose a model in which the Cterminus acts on the N-terminus to destabilize helical bundle. Upon lipid binding to the C-terminus, Trp8 is displaced from its interaction with Phe57, Arg61, Leu64, Val67, Phe71, and Trp72 to destabilize the bundle. However, when the C-terminus is deleted, Trp8 cannot be displaced, the bundle cannot unfold, and apoA1 cannot be lipidated.

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“…This process is facilitated by apoA-I interaction with members of the ATP-binding cassette transporters superfamily such as ABCA1, a cholesterol efflux mediator present in various cell types such as hepatocytes, enterocytes, and macrophages [ 13 , 14 ]. ABCA1 transfers cholesterol to lipid-poor apoA-I and promotes the formation of discoidal particles, denominated nascent HDLs, that are mainly composed of phosphatidylcholine and cholesterol [ 15 , 16 , 17 , 18 , 19 , 20 ]. In contrast, the ABCG1 transporter mediates cholesterol transport to the assembled HDL [ 21 , 22 ], but not to lipid-free apoA-I [ 21 , 23 ].…”

Section: Introductionmentioning

confidence: 99%

Cholesterol Efflux Efficiency of Reconstituted HDL Is Affected by Nanoparticle Lipid Composition

et al. 2020

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Cardiovascular disease (CVD), the leading cause of mortality worldwide is primarily caused by atherosclerosis, which is promoted by the accumulation of low-density lipoproteins into the intima of large arteries. Multiple nanoparticles mimicking natural HDL (rHDL) have been designed to remove cholesterol excess in CVD therapy. The goal of this investigation was to assess the cholesterol efflux efficiency of rHDLs with different lipid compositions, mimicking different maturation stages of high-density lipoproteins (HDLs) occurring in vivo. Methods: the cholesterol efflux activity of soybean PC (Soy-PC), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), DPPC:Chol:1-palmitoyl-2-hydroxy-sn-glycero-3-phosphocholine (LysoPC) and DPPC:18:2 cholesteryl ester (CE):LysoPC rHDLs was determined in several cell models to investigate the contribution of lipid composition to the effectiveness of cholesterol removal. Results: DPPC rHDLs are the most efficient particles, inducing cholesterol efflux in all cellular models and in all conditions the effect was potentiated when the ABCA1 transporter was upregulated. Conclusions: DPPC rHDLs, which resemble nascent HDL, are the most effective particles in inducing cholesterol efflux due to the higher physical binding affinity of cholesterol to the saturated long-chain-length phospholipids and the favored cholesterol transfer from a highly positively curved bilayer, to an accepting planar bilayer such as DPPC rHDLs. The physicochemical characteristics of rHDLs should be taken into consideration to design more efficient nanoparticles to promote cholesterol efflux.

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N-terminal mutation of apoA-I and interaction with ABCA1 reveal mechanisms of nascent HDL biogenesis

Cited by 23 publications

References 56 publications

First eight residues of apolipoprotein A-I mediate the C-terminus control of helical bundle unfolding and its lipidation

First eight residues of apolipoprotein A-I mediate the C-terminus control of helical bundle unfolding and its lipidation

First eight residues of apolipoprotein A-I mediate the C-terminus control of helical bundle unfolding and its lipidation

Cholesterol Efflux Efficiency of Reconstituted HDL Is Affected by Nanoparticle Lipid Composition

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