Platelet/polymorphonuclear leukocyte adhesion: a new role for SRC kinases in Mac-1 adhesive function triggered by P-selectin

Adhesion of polymorphonuclear leukocytes (PMNLs) to activated platelets req uires a P-selectin-triggered, tyrosine kinase-dependent adhesiveness of Mac -1 and is accompanied by tyrosine phosphorylation of a 110-kd protein(P-110 ) in PMNLs. Inhibitors of SRC tyrosine kinases were found to inhibit PMNL a dhesion to activated platelets or to P-selectin expressing Chinese hamster ovary (CHO-P) cells and the tyrosine phosphorylation of P-110. Adhesion of PMNLs to activated platelets or to CHO-P cells stimulated activity of LYN a nd HCK. Monoclonal antibody blockade of P-selectin or beta2-integrins reduc ed the activation of both kinases. In PMNLs either adherent to platelets or aggregated by P-selectin-IgG chimera, Mac-1 was rapidly redistributed to t he Triton X-100-insoluble cytoskeletal fraction, and large clusters of Mac- 1 colocalized with patches of F-actin at the sites of cell-cell contact. in PMNLs stimulated by P-selectin-IgG chimera, SRC kinase inhibition impaired Mac-1 clustering, F-actin accumulation, and CD18 redistribution to the cyt oskeleton. Disruption of the actin filament network by cytochalasin D preve nted PMNL-platelet adhesion and P-selectin-induced PMNL aggregation and imp aired the clustering of Mac-1. In agreement with the requirement for the be ta2-integrin in the functional up-regulation of LYN and HCK, integrin block ade by monoclonal antibodies resulted in a complete inhibition of P-selecti n-Induced Mac-1 clustering and F-actin accumulation. Taken together,the res ults indicate that, after an initial P-selectin-triggered pa-integrin inter action with the ligand, SRC kinases are activated and allow the remodeling of cytoskeleton-integrin link ages and integrin clustering that finally str engthen cell-cell adhesion. This model highlights a new role for SRC kinase s in a regulatory loop by which the Mac-1 promotes its own adhesive functio n. (C) 2001 by The American Society of Hematology.