Low-density lipoprotein receptor-related protein 1 is an essential receptor for myelin phagocytosis

Area of Science:

• Neuroimmunology
• Cellular Biology
• Biochemistry

Background:

• Multiple sclerosis (MS) involves progressive myelin degradation, potentially driving disease advancement.
• Efficient clearance of myelin debris is critical for managing MS progression.

Purpose of the Study:

• To identify the receptor responsible for clearing degraded myelin.
• To investigate the role of low-density lipoprotein receptor-related protein 1 (LRP1) in myelin phagocytosis.

Main Methods:

• Preparation of myelin vesicles (MV) from rat brains as a model of degraded myelin.
• Utilized murine embryonic fibroblasts (MEFs) and primary cultures of rat astrocytes, microglia, and oligodendrocytes.
• Employed receptor-associated protein (RAP) to inhibit LRP1 function and LRP1 gene silencing.
• Investigated the interaction between myelin basic protein (MBP) and LRP1.
• Examined LRP1 expression in a mouse model of experimental autoimmune encephalomyelitis (EAE).

Main Results:

• MEFs and primary CNS cells (astrocytes, microglia, oligodendrocytes) internalized MVs.
• MV uptake was dependent on LRP1 expression and inhibited by RAP.
• LRP1 gene silencing in oligodendrocytes blocked MV uptake.
• Recombinant myelin basic protein directly bound to LRP1, and an anti-MBP antibody inhibited MV uptake.
• LRP1 expression was significantly elevated in the cerebellum and spinal cord in EAE mice.

Conclusions:

• LRP1 is a major receptor mediating the phagocytosis of degraded myelin by CNS cells.
• LRP1 plays a significant role in clearing myelin debris, potentially impacting MS pathogenesis.
• LRP1 may function independently or with known co-receptors in myelin clearance.