Endothelial cell cortactin coordinates intercellular adhesion molecule-1 clustering and actin cytoskeleton remodeling...

Area of Science:

• Cell Biology
• Immunology
• Biochemistry

Background:

• Endothelial cell ICAM-1 (Intercellular Adhesion Molecule-1) interacts with leukocyte beta(2) integrins, mediating adhesion and facilitating leukocyte transmigration.
• ICAM-1 redistribution and clustering are essential for leukocyte transmigration, but the underlying mechanisms remain unclear.

Purpose of the Study:

• To investigate if the Src family kinase-cortactin pathway mediates the association of ICAM-1 with the actin cytoskeleton.
• To determine if this association is required for ICAM-1 clustering and subsequent leukocyte transmigration.

Main Methods:

• Utilized small interfering RNA (siRNA) to knockdown cortactin expression.
• Employed a cortactin mutant deficient in Src phosphorylation sites (cortactin3F).
• Administered the Src kinase inhibitor PP2.
• Assessed ICAM-1 lateral mobility using fluorescence recovery after photobleaching (FRAP).
• Quantified actin and ICAM-1 clustering in cytokine-activated human endothelial monolayers.

Main Results:

• Cross-linking ICAM-1 induced cytoskeletal remodeling and reduced ICAM-1 lateral mobility.
• Cortactin knockdown, expression of cortactin3F, or PP2 treatment diminished cytoskeletal remodeling after ICAM-1 cross-linking.
• Cortactin siRNA significantly decreased actin and ICAM-1 clustering around adherent polymorphonuclear cells (PMNs).
• The formation of actin-ICAM-1 clusters essential for PMN transmigration was reduced by cortactin siRNA.

Conclusions:

• Tyrosine phosphorylation of cortactin by Src kinase dynamically links ICAM-1 to the actin cytoskeleton.
• This linkage is critical for ICAM-1 clustering, which facilitates leukocyte transmigration.
• The Src-cortactin pathway represents a key regulatory mechanism for leukocyte extravasation.