Apolipoprotein Scaffold–Interface Coupling in Classical Lipoprotein Identity and Routing

Classical lipoproteins are classified by density, size, lipid composition, apolipoprotein content, metabolic origin, and receptor routing. These variables explain much of lipid transport but do not establish whether supramolecular organization of the lipid interface adds causal information about particle behavior. We hypothesize that classical lipoproteins are apolipoprotein-scaffolded lipid-state particles in which a measurable, perturbable, and persistent lipid-interface state cooperates with a biogenetic scaffold to influence stability, extracellular remodeling, routing, and recipient-cell responses. Source-state continuity may be material, as during ATP-binding cassette transporter A1-mediated transfer of cellular phospholipids and cholesterol to apolipoprotein A-I, or configurational, as when hepatic or intestinal physiology biases microsomal triglyceride transfer protein-dependent assembly of apolipoprotein B-containing particles. Apolipoprotein B provides a non-exchangeable scaffold with high continuity, whereas apolipoprotein A-I forms a more adaptable scaffold that is initiated by ATP-binding cassette transporter A1-dependent lipidation and subsequently remodeled by lecithin–cholesterol acyltransferase and other plasma factors. After biogenesis, exchangeable apolipoproteins, enzymes, and other associated proteins form an editable identity layer. Structural studies of apolipoprotein B, high-density lipoprotein biogenesis and heterogeneity, and inflammatory remodeling of high-density lipoprotein provide mechanistic precedents, but do not establish the proposed incremental causal layer. The hypothesis predicts that controlled differences in interfacial packing, accessibility, topology, oxidation, or electrostatics will alter protein acquisition, routing, or function after particle number, size, bulk composition, scaffold abundance, and established receptor pathways are controlled. It is weakened if these variables add no reproducible causal or predictive information beyond conventional lipoprotein biology.