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Discoidal complexes containing apolipoprotein E and their transformation by lecithin-cholesterol acyltransferase
E L Gong1, A V Nichols, K H Weisgraber
1Lawrence Berkeley Laboratory, University of California, Donner Laboratory, Berkeley 94720.
Biochimica Et Biophysica Acta
|December 18, 1989
Summary
Researchers created in vitro discoidal apolipoprotein (apo)E-containing high-density lipoproteins (HDL) that, when converted by lecithin-cholesterol acyltransferase (LCAT), formed spherical HDL particles similar to those found in human plasma.
Area of Science:
- Lipid Metabolism
- Protein Biochemistry
- Cardiovascular Research
Background:
- High-density lipoproteins (HDL) play a crucial role in reverse cholesterol transport.
- Apolipoprotein E (apoE) is a key component of certain HDL subclasses involved in lipoprotein metabolism and clearance.
- Understanding the in vitro formation and conversion of apoE-containing HDL is essential for elucidating their physiological functions.
Purpose of the Study:
- To synthesize in vitro discoidal apolipoprotein (apo)E-containing high-density lipoprotein (HDL) analogs.
- To investigate the conversion of these synthetic discoidal apoE-HDL particles by lecithin-cholesterol acyltransferase (LCAT).
- To compare the properties of LCAT-converted particles with native, core-containing, spherical apoE-HDL found in human plasma.
Main Methods:
- Preparation of apoE-POPC complexes using the cholate-dialysis technique, with and without incorporated unesterified cholesterol.
- Characterization of particle size and morphology using gradient gel electrophoresis.
- Incubation of isolated discoidal complexes with purified LCAT and a cholesterol source.
- Analysis of the size and properties of the resulting spherical particles.
Main Results:
- Discoidal apoE-HDL analogs were successfully prepared in vitro, with particle size correlating to the POPC:apoE molar ratio.
- Incorporation of unesterified cholesterol influenced the size distribution of the discoidal complexes.
- Incubation with LCAT converted discoidal complexes into spherical, cholesteryl ester-containing particles with sizes comparable to native apoE-HDL in human plasma.
- A portion of apoE shifted to the LDL particle size range during the conversion process.
Conclusions:
- The cholate-dialysis method can generate apoE-containing complexes resembling discoidal apoE-HDL.
- LCAT effectively converts these discoidal complexes into spherical, core-containing particles within the size range of plasma apoE-HDL.
- These findings suggest that direct LCAT conversion of discoidal apoE-HDL may contribute to the formation of plasma apoE-containing HDL particles.
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