Co-receptors are dispensable for tethering receptor-mediated phagocytosis of apoptotic cells

Area of Science:

• Immunology
• Cell Biology
• Biochemistry

Background:

• Efferocytosis, the process of clearing apoptotic cells, involves phagocytic receptors binding to ligands on dying cells.
• While many phagocytic receptors and signaling pathways are known, downstream pathways for tethering receptors remain unclear.
• The role and necessity of co-receptors for tethering receptors in efferocytosis are poorly understood.

Purpose of the Study:

• To investigate whether co-receptors are indispensable for tethering receptor-mediated efferocytosis.
• To elucidate the downstream signaling pathways involved in efferocytosis mediated by tethering receptors.
• To examine the inflammatory consequences of efferocytosis induced by tethering receptors.

Main Methods:

• Utilized glycophosphatidylinositol (GPI)-anchored annexin A5 (Anxa5-GPI), an artificial tethering receptor lacking a co-receptor.
• Assessed phagocyte binding and ingestion of apoptotic cells mediated by Anxa5-GPI.
• Investigated the dependence of Anxa5-GPI-induced phagocytosis on cytoskeletal machinery, Elmo-Dock-Rac module, and integrin pathways.
• Monitored anti-inflammatory responses following Anxa5-GPI-mediated efferocytosis.

Main Results:

• Phagocytes expressing Anxa5-GPI showed enhanced binding and promoted ingestion of apoptotic cells in a phosphatidylserine-dependent manner.
• Anxa5-GPI-induced phagocytosis utilized known cytoskeletal machinery but partially depended on the Elmo-Dock-Rac module or integrin pathway.
• Anxa5-GPI-mediated efferocytosis elicited anti-inflammatory responses.

Conclusions:

• Co-receptors are dispensable for tethering receptor-induced efferocytosis.
• Tethering receptors can mediate the engulfment of apoptotic cells through multiple signaling pathways.
• Efferocytosis induced by tethering receptors contributes to anti-inflammatory effects.