The adhesion receptor CD-31 can be primed to rapidly adjust the neutrophil cytoskeleton

The adhesion receptor CD-31 is expressed on neutrophils and endothelial cells and participates in trans-endothelial migration of neutrophils. Although necessary, information on CD-31-induced signaling and its influence on the shape-forming actin network is scarce. Here, we found that antibody engagement of CD-31 on suspended neutrophils triggered a prompt intracellular Ca2+ signal, providing the cells had been primed with a chemotactic factor. Inhibition of Src-tyrosine kinases blocked this Ca2+ signal, but not a fMet-Leu-Phe-induced Ca2+ signal. Despite the ability of fMet-Leu-Phe to activate Src-tyrosine kinases, it did not per se induce tyrosine phosphorylation of CD-31. However, fMet-Leu-Phe did enable such a phosphorylation following an antibody-induced engagement of CD-31. This clustering also triggered a Ca2+-dependent depolymerization of actin and, surprisingly enough, a simultaneous polymerization. The ability of CD-31 to signal dynamic alterations in the cytoskeleton, particularly the Ca2+-induced actin depolymerization, further explains how neutrophils can squeeze themselves out between adjacent endothelial cells. (C) 2002 Elsevier Science (USA).