L-ficolin binding and lectin pathway activation by acetylated low-density lipoprotein

Area of Science:

• Immunology
• Biochemistry

Background:

• L-ficolin and mannan-binding lectin (MBL) activate the lectin complement pathway.
• Both initiate C4 cleavage via MBL-associated serine protease-2 (MASP-2) upon ligand binding.

Purpose of the Study:

• To investigate L-ficolin binding reactions and MASP-2 activation.
• To establish optimal conditions for studying L-ficolin function using acetylated LDL (A-LDL) as a model ligand.

Main Methods:

• Plasma was passed through GlcNAc-derivatized Sepharose for L-ficolin and MASP-2 isolation.
• L-ficolin binding to A-LDL was assessed in various buffer conditions (NaCl, EDTA, calcium).
• MASP-2 activation by L-ficolin-A-LDL interaction was measured in modified and unmodified plasma.

Main Results:

• High-purity L-ficolin and MASP-2 were isolated using GlcNAc-Sepharose chromatography.
• L-ficolin demonstrated strong binding to A-LDL, particularly in 1.0 M NaCl-EDTA.
• L-ficolin binding to immobilized A-LDL induced MASP-2 activation in plasma.

Conclusions:

• Acetylated LDL (A-LDL) is a suitable ligand for studying L-ficolin.
• Albumin-free systems optimize L-ficolin binding and activation studies.
• 1.0 M NaCl in EDTA facilitates the isolation of L-ficolin and native MASP-2.