Reticulocalbin-1 facilitates microglial phagocytosis

Area of Science:

• Immunology and Neuroscience
• Cell Biology
• Molecular Mechanisms of Phagocytosis

Background:

• Phagocytosis is essential for tissue homeostasis, clearing apoptotic cells and debris.
• Identifying phagocytosis ligands is crucial for understanding phagocyte function but traditionally challenging.
• Extrinsic regulation of phagocytosis remains poorly defined due to identification difficulties.

Purpose of the Study:

• To develop a systematic approach for identifying microglial phagocytosis ligands.
• To investigate the role of secreted proteins as phagocytosis regulators.
• To characterize novel ligands involved in the clearance of apoptotic cells.

Main Methods:

• Functional screening approach for systematic identification of microglial phagocytosis ligands.
• Characterization of reticulocalbin-1 (Rcn1) as a potential phagocytosis ligand.
• Assays to assess Rcn1 binding to apoptotic neurons and its effect on microglial phagocytosis.

Main Results:

• A novel functional screening method enabled systematic identification of microglial phagocytosis ligands.
• Reticulocalbin-1 (Rcn1), a secreted protein, selectively binds to apoptotic neurons.
• Rcn1 enhances microglial phagocytosis of apoptotic neurons, with ingested cells localizing to Rab7-positive phagosomes.

Conclusions:

• Reticulocalbin-1 (Rcn1) functions as a genuine phagocytosis ligand for apoptotic neurons.
• The developed screening approach allows for broad applicability in identifying ligands for various phagocytes.
• This study advances the understanding of extrinsic regulation in microglial phagocytosis and tissue repair.