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Clusterin (complement lysis inhibitor) forms a high density lipoprotein complex with apolipoprotein A-I in human
D E Jenne1, B Lowin, M C Peitsch
1Institut of Biochemistry, University of Lausanne, Epalinges-sur-Lausanne, Switzerland.
The Journal of Biological Chemistry
|June 15, 1991
Summary
Clusterin, a complement inhibitor, circulates in plasma bound to apolipoprotein A-I (apoA-I) within high-density lipoproteins (HDL). This complex may regulate both complement and lipid transport.
Area of Science:
- Biochemistry
- Immunology
- Lipidology
Background:
- Clusterin, also known as human complement lysis inhibitor (CLI), is a known inhibitor of the terminal complement cascade.
- The native form and plasma interactions of clusterin are not fully elucidated.
Purpose of the Study:
- To identify and characterize protein components that co-purify with clusterin from human plasma.
- To investigate the functional relationship between clusterin and its associated plasma proteins, particularly concerning lipid transport.
Main Methods:
- Affinity chromatography using anti-clusterin antibodies.
- Immunoblotting and amino acid sequencing for protein identification.
- Lipid analysis of isolated complexes.
- Electrophoretic techniques (free flow isotachophoresis) and density ultracentrifugation for complex characterization.
Main Results:
- Apolipoprotein A-I (apoA-I) was identified as a 28-kDa protein co-purifying with clusterin.
- Clusterin binds to delipidated apoA-I and high-density lipoproteins (HDL).
- The isolated apoA-I-clusterin complex contains lipids, primarily cholesterol and phospholipids, and is found in HDL fractions.
Conclusions:
- Clusterin circulates in human plasma as a high-density lipoprotein (HDL) complex with apolipoprotein A-I (apoA-I).
- This complex may function as both a complement cascade inhibitor and a regulator of lipid transport and redistribution.