Downstream Effects of the Homophilic PECAM‐1 Interaction in Neutrophils

Abstract

Transmigration of neutrophils across the endothelial border and out of the blood vessel into tissues is essential to their ability to fight infection. We are interested in signaling pathways triggered in neutrophils by interaction with specific and spatially oriented components of the endothelial border milieu. The neutrophil/endothelial PECAM‐1 homophilic interaction has been shown critical for successful transmigration with many chemokines. Using microfabrication techniques, we have covalently immobilized the extracellular domain of junctional glycoprotein PECAM‐1 (Platelet/Endothelial Cell Adhesion Molecule) to a glass coverslide in a gradient fashion, and over biorelevant distances, in an effort to mimic traversal across the endothelial cell‐cell border. We demonstrate that neutrophil‐like HL‐60 cells and murine bone marrow neutrophils showed cell polarization when plated on PECAM‐1 coated glass slides but not on control slides, as evidenced by change in cell shape and localization of filamentous actin to the leading edge of the cell. PECAM‐1 is co‐localized with filamentous actin, as evidenced by a neutrophil‐specific antibody to PECAM‐1. These findings suggest an actin polymerization event triggered by an upstream PECAM‐1 homophilic interaction, and suggests that this homophilic interaction plays a role in cell‐shape change that may be necessary for transmigration.