Requirements for leukocyte transmigration via the transmembrane chemokine CX3CL1

Area of Science:

• Immunology
• Cell Biology
• Biochemistry

Background:

• CX3C chemokine ligand 1 (CX3CL1/fractalkine) is a molecule expressed on cell surfaces that binds to its receptor CX3CR1 on leukocytes, mediating cell adhesion.
• Shedding of CX3CL1 by ADAM10 and ADAM17 proteases generates a soluble form that acts as a chemoattractant for leukocytes.

Purpose of the Study:

• To investigate the mechanism by which transmembrane CX3CL1 induces leukocyte transmigration.
• To identify the roles of specific CX3CR1 receptor domains and ADAM proteases in this process.

Main Methods:

• Generation and functional analysis of CX3CR1 variants lacking the DRY motif or C-terminus.
• Investigation of leukocyte adhesion and transmigration assays using endothelial and epithelial cells expressing transmembrane CX3CL1.
• Pharmacological targeting of ADAM10 to assess its impact on CX3CL1-mediated leukocyte migration.

Main Results:

• Transmembrane CX3CL1 induces leukocyte transmigration.
• CX3CR1 variants with defects in the DRY motif or C-terminus impaired transmigration but not adhesion, causing leukocyte retention.
• Inhibition of ADAM10 increased adhesion but reduced transmigration mediated by transmembrane CX3CL1, without affecting soluble CX3CL1 activity.

Conclusions:

• Transmembrane CX3CL1 utilizes the DRY motif and C-terminus of CX3CR1 to mediate leukocyte transmigration.
• ADAM10 activity plays a critical role in regulating leukocyte transmigration induced by transmembrane CX3CL1.