Receptor internalization is required for eotaxin-induced responses in human eosinophils

Area of Science:

• Immunology
• Cell Biology
• Biochemistry

Background:

• CC chemokine receptor 3 (CCR3) is crucial for eosinophil trafficking and function.
• Ligand binding to CCR3 triggers various cellular signals, including shape change, actin polymerization, and calcium mobilization.
• CCR3 undergoes rapid and prolonged internalization after ligand binding.

Purpose of the Study:

• To investigate the role of CCR3 internalization in downstream cellular processes.
• To determine if internalization affects eosinophil shape change, actin polymerization, calcium mobilization, and desensitization.

Main Methods:

• Human eosinophils were treated with internalization inhibitors (sucrose, phenylarsine oxide).
• Functional responses including shape change, actin polymerization, and calcium mobilization were monitored.
• Receptor desensitization was assessed by measuring eotaxin-induced eosinophil transepithelial migration.

Main Results:

• Ligand-induced CCR3 internalization is required for chemokine-induced eosinophil shape change.
• Inhibition of internalization blocked actin polymerization, indicating its role in this early response.
• Calcium mobilization and receptor desensitization were not affected by blocking CCR3 internalization.

Conclusions:

• CCR3 internalization plays a critical role in eosinophil shape change and actin polymerization.
• CCR3 internalization is not involved in eosinophil desensitization or calcium mobilization.
• These findings clarify the specific functions of CCR3 internalization in eosinophil biology.