Denaturation of human plasma high-density lipoproteins by urea studied by apolipoprotein A-I dissociation

Biochim Biophys Acta Mol Cell Biol Lipids. 2021 Jan;1866(1):158814. doi: 10.1016/j.bbalip.2020.158814. Epub 2020 Sep 19.

Abstract

We studied the mechanism of HDL denaturation with concomitant apoA-I dissociation with HDL preparations from 48 patients with a wide range of plasma HDL-C and evaluated the contribution of lipid-free apoA-I into cholesterol efflux from macrophage, in particular, mediated by cholesterol transporter ABCA1. We prepared HDL by precipitation of apoB-containing lipoproteins by polyethylene glycol and used the chaotropic agent urea to denature HDL preparations. Apo-I dissociation from urea-treated HDL was assessed by the increase of preβ-band fraction with agarose gel electrophoresis followed by electro transfer and immunodetection and by the increase of ABCA1-mediated efflux of fluorescent analogue BODIPY-Cholesterol from RAW 264.7 macrophages. The HDL denaturation is governed by a single transition to fully dissociated apoA-I and the transition cooperativity decreases with increasing HDL-C. The apoA-I release depends on phospholipid concentration of HDL preparation and HDL compositional and structural heterogeneity and is well described by apolipoprotein partition between aqueous and lipid phases. Dissociated apoA-I determines the increase of ABCA1-mediated efflux of BODIPY-Cholesterol from RAW 264.7 macrophages to patient HDL. The increase in apoA-I dissociation is associated with the increase of ABCA1 gene transcript in peripheral blood mononuclear cells from patients. The low level of plasma HDL particles may be compensated by their increased potency for apoA-I release, thus suggesting apoA-I dissociation as a new HDL functional property.

Keywords: ABCA1; Cholesterol efflux; HDL kinetic stability; HDL mass and charge heterogeneity; Lipid-protein interaction; apoA-I.

MeSH terms

  • ATP Binding Cassette Transporter 1 / genetics
  • ATP Binding Cassette Transporter 1 / metabolism*
  • Adult
  • Animals
  • Apolipoprotein A-I / genetics
  • Apolipoprotein A-I / metabolism*
  • Biological Transport
  • Body Mass Index
  • Boron Compounds / chemistry
  • Cholesterol, HDL / blood*
  • Cholesterol, LDL / blood
  • Cohort Studies
  • Dyslipidemias / blood*
  • Dyslipidemias / genetics
  • Dyslipidemias / pathology
  • Fluorescent Dyes / chemistry
  • Gene Expression
  • Humans
  • Male
  • Mice
  • Middle Aged
  • Polyethylene Glycols / chemistry
  • Protein Denaturation / drug effects
  • RAW 264.7 Cells
  • Staining and Labeling / methods
  • Triglycerides / blood
  • Urea / chemistry*
  • Urea / pharmacology

Substances

  • 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene
  • ABCA1 protein, human
  • APOA1 protein, human
  • ATP Binding Cassette Transporter 1
  • Apolipoprotein A-I
  • Boron Compounds
  • Cholesterol, HDL
  • Cholesterol, LDL
  • Fluorescent Dyes
  • Triglycerides
  • Polyethylene Glycols
  • Urea