The N-Terminus of Apolipoprotein A-V Adopts a Helix Bundle Molecular Architecture

Wong, Kasuen; Beckstead, Jennifer A.; Lee, Dustin; Weers, Paul M.M.; Guigard, Emmanuel; Kay, Cyril M.; Ryan, Robert O.

doi:10.1021/bi800515c

Cited by 12 publications

(21 citation statements)

References 43 publications

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“…38 ) suggested a domain organization for lipid-free apoA-V analogous to that previously determined for apoA-I ( 39 ) and apoE ( 40 ). Thus, in the absence of lipids, apoA-V would be expected to feature an elongated, four-helix bundle comprising apoA-V interactions with sortilin covalently bound to CM5 sensor chips are shown in Fig.…”

Section: Apoa-v Stimulation Of Lpl Activitysupporting

confidence: 63%

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Structural and functional analysis of APOA5 mutations identified in patients with severe hypertriglyceridemia

Mendoza-Barberá

Julve

Nilsson

et al. 2013

Journal of Lipid Research

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Hypertriglyceridemia is common in humans and is a well-established cardiovascular risk factor independent of HDL cholesterol ( 1 ). Hypertriglyceridemia is present in hyperlipidemia types I, IIb, III, IV, and V, all of which (with the exception of type I hyperlipidemia, also known as familial hyperchylomicronemia) are currently considered complex diseases with a strong polygenic component ( 2, 3 ). While LPL and APOC2 gene mutations have been known for decades to be a cause of familial hyperchylomicronemia ( 4-6 ), mutations in the APOA5 or glycosylphosphatidylinositol-anchored HDL-binding protein 1 ( GPIHBP1 ) genes have been found more recently to explain some cases of this disease in which no LPL or APOC2 mutations were found ( 7-9 ). APOA5 variants have also been linked to the polygenic hyperlipidemia types IIb, III, IV, and V as well as to cardiovascular disease risk ( 3,(10)(11)(12)(13)(14).ApoA-V was fi rst identifi ed and characterized as a liver preprotein of 366 amino acid residues that is secreted 08-1147 (to F.B.-V.), 11-01076 (to F.B.-V.), 10-00277 (to J.J.), and SAF2010-15668 (to P.F.-P.) This work was funded by Instituto de Salud Carlos III (ISCIII) Grants

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Section: Apoa-v Stimulation Of Lpl Activitysupporting

confidence: 63%

“…However, and to verify this point while avoiding protein aggregation, we subjected wild-type apoA-V to limited proteolysis with pepsin at acidic pH, similar to a recent report (see Materials and Methods and Ref. 38 ). As shown in supplementary Fig.…”

Section: Cloning Expression and Characterization Of Recombinant Hummentioning

confidence: 99%

Structural and functional analysis of APOA5 mutations identified in patients with severe hypertriglyceridemia

Mendoza-Barberá

Julve

Nilsson

et al. 2013

Journal of Lipid Research

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“…Unlike the full-length protein, recombinant apoA-V(1-146) was soluble in neutral-pH buffer in the absence of lipid (26). Guanidine HCl denaturation experiments at pH 3.0 yielded a one-step native-to-unfolded transition that corresponds directly with the more stable component of the two-stage denaturation profile exhibited by full-length apoA-V. Taken together, the data suggest that the N-terminal 146 residues of human apoA-V adopt a helix bundle molecular architecture in the absence of lipid and thus likely exist as an independently folded structural domain within the context of the intact protein.…”

Section: Unique Aspects Of Apoa-v Structurementioning

confidence: 99%

The ins (cell) and outs (plasma) of apolipoprotein A-V

Forte¹,

Shu

Ryan

2009

Journal of Lipid Research

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Apolipoprotein A-V (apoA-V) has a close interrelationship with plasma triglyceride (TG). Since the discovery of the apoA-V gene in 2001, we have learned that single nucleotide polymorphisms in this gene correlate with altered plasma TG levels in humans, while genetically engineered mice manifest unique TG phenotypes. Studies of recombinant apoA-V protein have revealed that it is composed of two independently folded structural domains. The C-terminal domain possesses high lipid binding affinity, while the N-terminal domain adopts a helix bundle molecular architecture. A sequence element with high positive charge character, between residues 185 and 228, functions in binding of apoA-V to heparan sulfate proteoglycans as well as to members of the low-density lipoprotein receptor family and glycosylphosphatidylinositol high-density lipoprotein binding protein1. These interactions may be related to the capacity of this protein to regulate TG levels. ApoA-V is poorly secreted from transfected cultured hepatoma cell lines and is present in plasma at exceedingly low levels. Studies of apoA-V intracellular trafficking revealed an association with cytosolic lipid droplets. Thus, it is conceivable that apoA-V may also modulate TG metabolism within the cell. Much remains to be learned about this fascinating yet confounding member of the class of exchangeable apolipoproteins.-Forte, T. M., X. Shu, and R. O. Ryan. The ins (cell) and outs (plasma) of apolipoprotein A-V. J. Lipid Res. 2009. 50: S150-S155.Supplementary key words apolipoprotein A-V molecular structureExchangeable apolipoproteins that possess a unique structural feature, the amphipathic a-helix, play an essential role in plasma lipoprotein metabolism. Aberrations in the concentration and/or structure of apolipoproteins are frequently associated with dyslipidemias and increased risk for premature coronary artery disease. A new member of the exchangeable apolipoprotein family was discovered by Pennacchio et al. in 2001 (1). These authors carried out a comparative genomics study in the region of the apolipoprotein (apo) gene cluster (APOAI/CIII/AIV ) on human chromosome 11q23. Comparison with the corresponding mouse sequence revealed a conserved region ?30 kb proximal to the gene cluster. This new gene, termed APOAV, encodes a 366 amino acid protein in humans.To evaluate the physiological function of apoA-V, Pennacchio et al.(1) created mice that were deficient in murine apoA-V or that overexpressed human apoA-V. Mice expressing the APOAV transgene showed a 70% decrease in plasma triglyceride (TG) compared with control littermates, while apoA-V deficient mice had a 4-fold elevation in TG concentration. These early observations suggested that apoA-V has a role in regulating TG metabolism.While the discovery of Pennacchio et al. was unfolding, van der Vliet et al. (2), using cDNA subtractive hybridization, discovered a gene that is upregulated in regenerating rat liver. The encoded protein, comprising 367 amino acids, was expressed only in liver and was identif...

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“…This finding is consistent with the stability properties of these apolipoproteins. At physiological pH apoA-V(1-146) is less stable than apoE3 NT (guanidine HCl denaturation midpoint of 2.0 M versus 2.5 M, respectively) (8,36) yet is more stable than apoA-I (1 M guanidine HCl denaturation midpoint) (37). Thus, it appears that the intrinsic stability of helix bundle apolipoproteins in solution correlates directly with the ability to bind newly created sites on a spherical lipoprotein substrate (8).…”

Section: Apoa-v(mentioning

confidence: 99%

“…Structural studies revealed that apoA-V is a two-domain protein (7) and that its N-terminal 146 residues adopt a helix bundle structure in the absence of lipid (8). Truncated apoA-V proteins in this size range have been reported in human subjects with severe hypertriglyceridemia (HTG) (9,10).…”

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confidence: 99%

Apolipoprotein A-V N-terminal Domain Lipid Interaction Properties in Vitro Explain the Hypertriglyceridemic Phenotype Associated with Natural Truncation Mutants

Mauldin

Raussens

Forte³

et al. 2009

Journal of Biological Chemistry

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The N-terminal 146 residues of apolipoprotein (apo) A-V adopt a helix bundle conformation in the absence of lipid. Because similarly sized truncation mutants in human subjects correlate with severe hypertriglyceridemia, the lipid binding properties of apoA-V(1-146) were studied. Upon incubation with phospholipid in vitro, apoA-V(1-146) forms reconstituted high density lipoproteins 15-17 nm in diameter. Far UV circular dichroism spectroscopy analyses of lipid-bound apoA-V(1-146) yielded an ␣-helix secondary structure content of 60%. Fourier transformed infrared spectroscopy analysis revealed that apoA-V(1-146) ␣-helix segments align perpendicular with respect to particle phospholipid fatty acyl chains. Fluorescence spectroscopy of single Trp variant apoA-V(1-146) indicates that lipid interaction is accompanied by a conformational change. The data are consistent with a model wherein apoA-V(1-146) ␣-helices circumscribe the perimeter of a disk-shaped bilayer. The ability of apoA-V(1-146) to solubilize dimyristoylphosphatidylcholine vesicles at a rate faster than full-length apoA-V suggests that N-and C-terminal interactions in the full-length protein modulate its lipid binding properties. Preferential association of apoA-V(1-146) with murine plasma HDL, but not with VLDL, suggests that particle size is a determinant of its lipoprotein binding specificity. It may be concluded that defective lipoprotein binding of truncated apoA-V contributes to the hypertriglyceridemia phenotype associated with truncation mutations in human subjects.The helix bundle motif is a common molecular architecture in proteins (1). Exchangeable apolipoproteins (apo) 4 are known to adopt this conformation, which supports their dual existence in alternate lipid-free and lipid-bound states. Classic examples of the helix bundle structure include the N-terminal (NT) domains of apoE (2) and apoA-I (3) as well as apolipophorin III (4). In the case of apoE and apoA-I, the helix bundle motifs are present within the context of a larger protein structure. In each of these examples the bundle exists as an up-and-down series of amphipathic ␣-helices wherein the hydrophobic face of each helical segment orients toward the interior of the bundle. At the same time, the polar face of the amphipathic helices is directed toward the exterior of the bundle. In this way the globular structure is stabilized by hydrophobic helix-helix interactions and is conferred with water solubility through projection of polar and charged amino acid side chains toward the aqueous milieu. Upon interaction with lipid surfaces, the helix bundle is postulated to unfurl, adopting an extended open conformation that promotes interaction between the hydrophobic faces of amphipathic helices and the lipid surface. Essentially, lipid binding of helix bundle apolipoproteins substitutes helix-helix contacts in the bundle for helix-lipid contacts that stabilize the lipid-bound state.In 2001 a new apolipoprotein, termed apoA-V, was reported that profoundly affects plasma TG levels (5, 6). Str...

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The N-Terminus of Apolipoprotein A-V Adopts a Helix Bundle Molecular Architecture

Cited by 12 publications

References 43 publications

Structural and functional analysis of APOA5 mutations identified in patients with severe hypertriglyceridemia

Structural and functional analysis of APOA5 mutations identified in patients with severe hypertriglyceridemia

The ins (cell) and outs (plasma) of apolipoprotein A-V

Apolipoprotein A-V N-terminal Domain Lipid Interaction Properties in Vitro Explain the Hypertriglyceridemic Phenotype Associated with Natural Truncation Mutants

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