LilrB3 is a putative cell surface receptor of APOE4

Area of Science:

• Immunology
• Neuroscience
• Structural Biology

Background:

• Apolipoprotein E (APOE) has three isoforms (APOE2, APOE3, APOE4) with distinct immunomodulatory functions.
• The molecular mechanisms driving these APOE isoform-specific immune responses are not well understood.

Purpose of the Study:

• To elucidate the mechanism by which APOE isoforms differentially affect immune responses.
• To identify the specific receptor mediating APOE4's immune effects.

Main Methods:

• Biochemical assays to study protein interactions.
• X-ray crystallography to determine atomic structures.
• Cell-based assays using human microglia cells (HMC3).

Main Results:

• APOE4 specifically binds to leukocyte immunoglobulin-like receptor B3 (LilrB3), unlike APOE2.
• Structural analysis revealed a hetero-tetrameric complex formed by APOE4 and LilrB3.
• APOE4, via LilrB3, induces a pro-inflammatory state in HMC3 cells.

Conclusions:

• Leukocyte immunoglobulin-like receptor B3 (LilrB3) is identified as a specific immune cell receptor for APOE4.
• This interaction provides a mechanism for APOE4's pro-inflammatory effects.
• Findings may illuminate APOE isoform roles in disease pathogenesis.