Speciated human high-density lipoprotein protein proximity profiles

Area of Science:

• Biochemistry
• Lipid Metabolism
• Proteomics

Background:

• Human high-density lipoprotein (HDL) structure is heterogeneous, impacting its diverse metabolic functions.
• Understanding the apolipoprotein composition of HDL subfractions is key to elucidating particle-specific roles.

Purpose of the Study:

• To determine the structural heterogeneity of human HDL by analyzing major apolipoprotein stoichiometry profiles.
• To characterize distinct HDL subfractions and their apolipoprotein content for functional insights.

Main Methods:

• Separation of HDL into LpA-I and LpA-I/A-II populations, followed by size exclusion chromatography (SEC) into six subfractions each.
• Determination of protein proximity profiles (PPPs) using bis(sulfosuccinimidyl) suberate (BS(3)) cross-linking and MALDI-MS.
• Compositional analysis of phospholipids, cholesterol, and triglycerides in individual HDL subpopulations.

Main Results:

• LpA-I subfractions showed increasing apoA-I molecules (two to four) with increasing particle size.
• LpA-I/A-II particles consistently contained two apoA-I molecules, with apoA-II varying from one to three.
• ApoC-III was detected in a subset of subfractions alongside apoA-I and/or apoA-II.
• LpA-I/A-II subfractions maintained consistent proportions of protein, phospholipids, and lipids, while LpA-I components varied significantly.

Conclusions:

• Detailed apolipoprotein stoichiometry and structural profiles of HDL subfractions have been elucidated.
• This characterization provides a foundation for understanding the functional specificity of different HDL particles.