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

• Published in: The Journal of biological chemistry Vol. 284; no. 48; pp. 33369 - 33376
• Main Authors: Wong-Mauldin, Kasuen, Raussens, Vincent, Forte, Trudy M., Ryan, Robert O.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 27.11.2009; American Society for Biochemistry and Molecular Biology
• Subjects: Animals; Apolipoprotein A-V; Apolipoproteins - chemistry; Apolipoproteins - genetics; Apolipoproteins - metabolism; Apolipoproteins A - chemistry; Apolipoproteins A - genetics; Apolipoproteins A - metabolism; Binding Sites; Circular Dichroism; Humans; Hypertriglyceridemia - genetics; Hypertriglyceridemia - metabolism; Hypertriglyceridemia - pathology; Immunoblotting; Kinetics; Lipids and Lipoproteins: Metabolism, Regulation, and Signaling; Lipoproteins, HDL - blood; Lipoproteins, HDL - metabolism; Lipoproteins, VLDL - blood; Lipoproteins, VLDL - metabolism; Male; Mice; Mice, Knockout; Mutation; Phospholipids - metabolism; Protein Binding; Protein Structure, Secondary; Spectrometry, Fluorescence; Spectroscopy, Fourier Transform Infrared
• ISSN: 0021-9258; 1083-351X; 1083-351X
• DOI: 10.1074/jbc.M109.040972

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 α-helix secondary structure content of 60%. Fourier transformed infrared spectroscopy analysis revealed that apoA-V(1–146) α-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) α-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.