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Enzymatically modified low-density lipoprotein is recognized by c1q and activates the classical complement pathway.

Arlaud GJ, Biro A, Ling WL - J Lipids (2011)

Bottom Line: To further investigate this question, we have studied the ability of native and modified forms of LDL to bind and activate C1, the complex protease that triggers the classical pathway of complement.Further investigations revealed that C1q recognizes a lipid component of E-LDL.Several approaches, including reconstitution of model lipid vesicles, cosedimentation, and electron microscopy analyses, provided evidence that C1 binding to E-LDL particles is mediated by the C1q globular domain, which senses unesterified fatty acids generated by cholesterol esterase.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire d'Enzymologie Moléculaire, Institut de Biologie Structurale Jean-Pierre Ebel, 41 rue Jules Horowitz, 38027 Grenoble Cedex 1, France.

ABSTRACT
Several studies suggest that the complement system is involved in atherogenesis. To further investigate this question, we have studied the ability of native and modified forms of LDL to bind and activate C1, the complex protease that triggers the classical pathway of complement. Unlike native LDL, oxidized (oxLDL) and enzymatically modified (E-LDL) derivatives were both recognized by the C1q subunit of C1, but only E-LDL particles, obtained by sequential treatment with a protease and then with cholesterol esterase, had the ability to trigger C1 activation. Further investigations revealed that C1q recognizes a lipid component of E-LDL. Several approaches, including reconstitution of model lipid vesicles, cosedimentation, and electron microscopy analyses, provided evidence that C1 binding to E-LDL particles is mediated by the C1q globular domain, which senses unesterified fatty acids generated by cholesterol esterase. The potential implications of these findings in atherogenesis are discussed.

No MeSH data available.


Related in: MedlinePlus

C1 activation by E-LDL particle: correlation with the amount of unesterified cholesterol generated. LDL (1 mg/mL) was treated with 20 μg/mL trypsin for 2 h at 37°C and then with 320 milliunits/mL CEase for the indicated periods at 37°C. The lipid fraction from each sample was extracted and incorporated into vesicles. Each vesicle was tested for its C1-activating ability (black bars). The cholesterol content of each lipid fraction (open circles) was determined by reverse-phase HPLC. LDL: native LDL; Try-LDL: trypsin-treated LDL (taken from [15], with permission).
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fig2: C1 activation by E-LDL particle: correlation with the amount of unesterified cholesterol generated. LDL (1 mg/mL) was treated with 20 μg/mL trypsin for 2 h at 37°C and then with 320 milliunits/mL CEase for the indicated periods at 37°C. The lipid fraction from each sample was extracted and incorporated into vesicles. Each vesicle was tested for its C1-activating ability (black bars). The cholesterol content of each lipid fraction (open circles) was determined by reverse-phase HPLC. LDL: native LDL; Try-LDL: trypsin-treated LDL (taken from [15], with permission).

Mentions: As a first step towards identification of the LDL component(s) recognized by C1q, the lipid fractions of native LDL, trypsin-treated LDL, and E-LDL were extracted and used to prepare vesicles which were then tested for their ability to activate C1 [15]. As shown in Figure 2, vesicles containing the lipid fraction of unmodified or trypsin-treated LDL did not yield C1 activation. In contrast, vesicles prepared from LDL samples treated with trypsin and then incubated with CEase for increasing periods at 37°C developed increasing C1-activating ability, to reach about 90% activation after incubation with 320 milliunits CEase for 16 h. In contrast, the protein component of this sample left after lipid extraction did not induce C1 activation. Likewise, native or trypsin-treated ApoB-100 had no activating effect.


Enzymatically modified low-density lipoprotein is recognized by c1q and activates the classical complement pathway.

Arlaud GJ, Biro A, Ling WL - J Lipids (2011)

C1 activation by E-LDL particle: correlation with the amount of unesterified cholesterol generated. LDL (1 mg/mL) was treated with 20 μg/mL trypsin for 2 h at 37°C and then with 320 milliunits/mL CEase for the indicated periods at 37°C. The lipid fraction from each sample was extracted and incorporated into vesicles. Each vesicle was tested for its C1-activating ability (black bars). The cholesterol content of each lipid fraction (open circles) was determined by reverse-phase HPLC. LDL: native LDL; Try-LDL: trypsin-treated LDL (taken from [15], with permission).
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3066639&req=5

fig2: C1 activation by E-LDL particle: correlation with the amount of unesterified cholesterol generated. LDL (1 mg/mL) was treated with 20 μg/mL trypsin for 2 h at 37°C and then with 320 milliunits/mL CEase for the indicated periods at 37°C. The lipid fraction from each sample was extracted and incorporated into vesicles. Each vesicle was tested for its C1-activating ability (black bars). The cholesterol content of each lipid fraction (open circles) was determined by reverse-phase HPLC. LDL: native LDL; Try-LDL: trypsin-treated LDL (taken from [15], with permission).
Mentions: As a first step towards identification of the LDL component(s) recognized by C1q, the lipid fractions of native LDL, trypsin-treated LDL, and E-LDL were extracted and used to prepare vesicles which were then tested for their ability to activate C1 [15]. As shown in Figure 2, vesicles containing the lipid fraction of unmodified or trypsin-treated LDL did not yield C1 activation. In contrast, vesicles prepared from LDL samples treated with trypsin and then incubated with CEase for increasing periods at 37°C developed increasing C1-activating ability, to reach about 90% activation after incubation with 320 milliunits CEase for 16 h. In contrast, the protein component of this sample left after lipid extraction did not induce C1 activation. Likewise, native or trypsin-treated ApoB-100 had no activating effect.

Bottom Line: To further investigate this question, we have studied the ability of native and modified forms of LDL to bind and activate C1, the complex protease that triggers the classical pathway of complement.Further investigations revealed that C1q recognizes a lipid component of E-LDL.Several approaches, including reconstitution of model lipid vesicles, cosedimentation, and electron microscopy analyses, provided evidence that C1 binding to E-LDL particles is mediated by the C1q globular domain, which senses unesterified fatty acids generated by cholesterol esterase.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire d'Enzymologie Moléculaire, Institut de Biologie Structurale Jean-Pierre Ebel, 41 rue Jules Horowitz, 38027 Grenoble Cedex 1, France.

ABSTRACT
Several studies suggest that the complement system is involved in atherogenesis. To further investigate this question, we have studied the ability of native and modified forms of LDL to bind and activate C1, the complex protease that triggers the classical pathway of complement. Unlike native LDL, oxidized (oxLDL) and enzymatically modified (E-LDL) derivatives were both recognized by the C1q subunit of C1, but only E-LDL particles, obtained by sequential treatment with a protease and then with cholesterol esterase, had the ability to trigger C1 activation. Further investigations revealed that C1q recognizes a lipid component of E-LDL. Several approaches, including reconstitution of model lipid vesicles, cosedimentation, and electron microscopy analyses, provided evidence that C1 binding to E-LDL particles is mediated by the C1q globular domain, which senses unesterified fatty acids generated by cholesterol esterase. The potential implications of these findings in atherogenesis are discussed.

No MeSH data available.


Related in: MedlinePlus