Structural heterogeneity of apoB-containing serum lipoproteins visualized using cryo-electron microscopy

Area of Science:

• Biochemistry
• Structural Biology
• Medical Science

Background:

• Lipoprotein structure and heterogeneity are crucial for understanding cardiovascular disease.
• Distinct lipoprotein profiles, such as large buoyant LDL (pattern A) versus small dense LDL (pattern B), have different clinical implications.

Purpose of the Study:

• To investigate the structural characteristics of human very low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), and low-density lipoprotein (LDL) particles using cryo-electron microscopy.
• To compare the structural heterogeneity of these lipoproteins in individuals with different LDL patterns (Pattern A vs. Pattern B).

Main Methods:

• Cryo-electron microscopy was employed to analyze lipoprotein particles isolated from density gradient subfractions.
• Lipoproteins from normolipidemic subjects with Pattern A (large, buoyant LDL) and Pattern B (small, dense LDL) were compared.

Main Results:

• VLDL particles exhibited heterogeneity in size but were generally circular with even contrast.
• LDL particles displayed diverse structures, including circular with a high-density ring or rectangular with two high-density bands, decreasing in size with increasing density.
• IDL preparations contained particles resembling both VLDL and LDL, with heterogeneity observed within LDL-like IDL particles, irrespective of LDL pattern.

Conclusions:

• The structural heterogeneity observed in apolipoprotein B-containing serum lipoproteins, particularly LDL and IDL, suggests compositional differences.
• These structural variations may contribute to differing metabolic and pathological properties of these lipoproteins.